U.S. patent application number 17/806666 was filed with the patent office on 2022-09-29 for communication system, base station, and user apparatus.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Fumihiro HASEGAWA, Mitsuru MOCHIZUKI, Masayuki NAKAZAWA, Tadahiro SHIMODA.
Application Number | 20220311553 17/806666 |
Document ID | / |
Family ID | 1000006394692 |
Filed Date | 2022-09-29 |
United States Patent
Application |
20220311553 |
Kind Code |
A1 |
SHIMODA; Tadahiro ; et
al. |
September 29, 2022 |
COMMUNICATION SYSTEM, BASE STATION, AND USER APPARATUS
Abstract
Provided is a communication system capable of suppressing
decrease in a transmission rate. An eNB communicates with a UE
using a self-contained subframe. The self-contained subframe
includes a downlink signal to be transmitted from the eNB to the
UE, and an uplink signal to be transmitted from the UE to the eNB
in response to the downlink signal. The uplink signal has a
structure including an uplink control signal indicating information
for controlling transmission of the uplink signal, and uplink user
data to be transmitted before and after the uplink control signal.
The eNB notifies the UE of a structure of the uplink signal. The
eNB may predetermine scheduling for retransmission to retransmit
the downlink signal, before performing initial transmission of the
downlink signal.
Inventors: |
SHIMODA; Tadahiro; (Tokyo,
JP) ; MOCHIZUKI; Mitsuru; (Tokyo, JP) ;
NAKAZAWA; Masayuki; (Tokyo, JP) ; HASEGAWA;
Fumihiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
1000006394692 |
Appl. No.: |
17/806666 |
Filed: |
June 13, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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17019894 |
Sep 14, 2020 |
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17806666 |
|
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16329916 |
Mar 1, 2019 |
10812228 |
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PCT/JP2017/028223 |
Aug 3, 2017 |
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17019894 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 28/04 20130101;
H04W 24/10 20130101; H04W 76/27 20180201; H04L 5/005 20130101; H04L
1/189 20130101; H04W 72/0446 20130101; H04L 25/0226 20130101; H04W
48/10 20130101; H04W 28/06 20130101; H04L 1/1819 20130101; H04W
74/0833 20130101; H04L 5/0055 20130101; H04W 80/02 20130101; H04W
72/04 20130101 |
International
Class: |
H04L 1/18 20060101
H04L001/18; H04W 72/04 20060101 H04W072/04; H04L 25/02 20060101
H04L025/02; H04L 5/00 20060101 H04L005/00; H04W 80/02 20060101
H04W080/02; H04W 24/10 20060101 H04W024/10; H04W 74/08 20060101
H04W074/08; H04W 76/27 20060101 H04W076/27; H04W 48/10 20060101
H04W048/10; H04W 28/04 20060101 H04W028/04; H04W 28/06 20060101
H04W028/06 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2016 |
JP |
2016190003 |
Claims
1. A communication system comprising: a base station; and a user
apparatus configured to perform downlink communication and uplink
communication with the base station, wherein the base station
transmits, to the user apparatus, control information related to a
gap provided after transmission of an uplink signal by the user
apparatus.
2. The communication system according to claim 1, wherein the gap
is set in a unit of a symbol in the control information.
3. The communication system according to claim 2, wherein the gap
is selected from multiple candidates.
4. The communication system according to claim 1, wherein the
control information includes time information that indicates a time
until which the gap indicated by the control information is
activated.
5. The communication system according to claim 1, wherein the base
station dynamically sets the control information to the user
apparatus using L1/L2 signalling.
6. The communication system according to claim 1, wherein the gap
is set for each type of the uplink communication in the control
information.
7. A base station in a communication system comprising the base
station and a user apparatus configured to perform downlink
communication and uplink communication with the base station,
wherein the base station transmits, to the user apparatus, control
information related to a gap provided after transmission of an
uplink signal by the user apparatus.
8. A user apparatus in a communication system comprising a base
station and the user apparatus configured to perform downlink
communication and uplink communication with the base station,
wherein the user apparatus performs the uplink communication based
on control information transmitted from the base station and
related to a gap provided after transmission of an uplink signal by
the user apparatus.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 17/019,894, filed Sep. 14, 2020, which is a
continuation application of and claims the benefit of priority
under 35 U.S.C. .sctn. 120 for U.S. Ser. No. 16/329,916, filed Mar.
1, 2019 (now U.S. Pat. No. 10,812,228 on Oct. 20, 2020), which is a
National Stage application of PCT/JP2017/028223, filed Aug. 3, 2017
and claims benefit of priority under 35 U.S.C. .sctn. 119 from JP
2016-190003, filed Sep. 28, 2016, the entire contents of each of
which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a communication system in
which radio communication is performed between a communication
terminal device such as a user equipment device and a base station
device.
BACKGROUND ART
[0003] The 3rd generation partnership project (3GPP), the standard
organization regarding the mobile communication system, is studying
communication systems referred to as long term evolution (LTE)
regarding radio sections and system architecture evolution (SAE)
regarding the overall system configuration including a core network
and a radio access network, which will be hereinafter collectively
referred to as a network as well (for example, see Non-Patent
Documents 1 to 5). This communication system is also referred to as
3.9 generation (3.9 G) system.
[0004] As the access scheme of the LTE, orthogonal frequency
division multiplexing (OFDM) is used in a downlink direction and
single carrier frequency division multiple access (SC-FDMA) is used
in an uplink direction. Further, differently from the wideband code
division multiple access (W-CDMA), circuit switching is not
provided but a packet communication system is only provided in the
LTE.
[0005] The decisions by 3GPP regarding the frame configuration in
the LTE system described in Non-Patent Document 1 (Chapter 5) will
be described with reference to FIG. 1. FIG. 1 is a diagram
illustrating the configuration of a radio frame used in the LTE
communication system. With reference to FIG. 1, one radio frame is
10 ms. The radio frame is divided into ten equally sized subframes.
The subframe is divided into two equally sized slots. The first and
sixth subframes contain a downlink synchronization signal per radio
frame. The synchronization signals are classified into a primary
synchronization signal (P-SS) and a secondary synchronization
signal (S-SS).
[0006] Non-Patent Document 1 (Chapter 5) describes the decisions by
3GPP regarding the channel configuration in the LTE system. It is
assumed that the same channel configuration is used in a closed
subscriber group (CSG) cell as that of a non-CSG cell.
[0007] A physical broadcast channel (PBCH) is a channel for
downlink transmission from a base station device (hereinafter may
be simply referred to as a "base station") to a communication
terminal device (hereinafter may be simply referred to as a
"communication terminal") such as a user equipment device
(hereinafter may be simply referred to as a "user equipment"). A
BCH transport block is mapped to four subframes within a 40 ms
interval. There is no explicit signaling indicating 40 ms
timing.
[0008] A physical control format indicator channel (PCFICH) is a
channel for downlink transmission from a base station to a
communication terminal. The PCFICH notifies the number of
orthogonal frequency division multiplexing (OFDM) symbols used for
PDCCHs from the base station to the communication terminal. The
PCFICH is transmitted per subframe.
[0009] A physical downlink control channel (PDCCH) is a channel for
downlink transmission from a base station to a communication
terminal. The PDCCH notifies of the resource allocation information
for downlink shared channel (DL-SCH) being one of the transport
channels described below, resource allocation information for a
paging channel (PCH) being one of the transport channels described
below, and hybrid automatic repeat request (HARQ) information
related to DL-SCH. The PDCCH carries an uplink scheduling grant.
The PDCCH carries acknowledgement (Ack)/negative acknowledgement
(Nack) that is a response signal to uplink transmission. The PDCCH
is referred to as an L1/L2 control signal as well.
[0010] A physical downlink shared channel (PDSCH) is a channel for
downlink transmission from a base station to a communication
terminal. A downlink shared channel (DL-SCH) that is a transport
channel and a PCH that is a transport channel are mapped to the
PDSCH.
[0011] A physical multicast channel (PMCH) is a channel for
downlink transmission from a base station to a communication
terminal. A multicast channel (MCH) that is a transport channel is
mapped to the PMCH.
[0012] A physical uplink control channel (PUCCH) is a channel for
uplink transmission from a communication terminal to a base
station. The PUCCH carries Ack/Nack that is a response signal to
downlink transmission. The PUCCH carries a channel quality
indicator (CQI) report. The CQI is quality information indicating
the quality of received data or channel quality. In addition, the
PUCCH carries a scheduling request (SR).
[0013] A physical uplink shared channel (PUSCH) is a channel for
uplink transmission from a communication terminal to a base
station. An uplink shared channel (UL-SCH) that is one of the
transport channels is mapped to the PUSCH.
[0014] A physical hybrid ARQ indicator channel (PHICH) is a channel
for downlink transmission from a base station to a communication
terminal. The PHICH carries Ack/Nack that is a response signal to
uplink transmission. A physical random access channel (PRACH) is a
channel for uplink transmission from the communication terminal to
the base station. The PRACH carries a random access preamble.
[0015] A downlink reference signal (RS) is a known symbol in the
LTE communication system. The following five types of downlink
reference signals are defined: a cell-specific reference signal
(CRS), an MBSFN reference signal, a data demodulation reference
signal (DM-RS) being a UE-specific reference signal, a positioning
reference signal (PRS), and a channel state information reference
signal (CSI-RS). The physical layer measurement objects of a
communication terminal include reference signal received power
(RSRP).
[0016] The transport channels described in Non-Patent Document 1
(Chapter 5) will be described. A broadcast channel (BCH) among the
downlink transport channels is broadcast to the entire coverage of
a base station (cell). The BCH is mapped to the physical broadcast
channel (PBCH).
[0017] Retransmission control according to a hybrid ARQ (HARQ) is
applied to a downlink shared channel (DL-SCH). The DL-SCH can be
broadcast to the entire coverage of the base station (cell). The
DL-SCH supports dynamic or semi-static resource allocation. The
semi-static resource allocation is also referred to as persistent
scheduling. The DL-SCH supports discontinuous reception (DRX) of a
communication terminal for enabling the communication terminal to
save power. The DL-SCH is mapped to the physical downlink shared
channel (PDSCH).
[0018] The paging channel (PCH) supports DRX of the communication
terminal for enabling the communication terminal to save power. The
PCH is required to be broadcast to the entire coverage of the base
station (cell). The PCH is mapped to physical resources such as the
physical downlink shared channel (PDSCH) that can be used
dynamically for traffic.
[0019] The multicast channel (MCH) is used for broadcast to the
entire coverage of the base station (cell). The MCH supports SFN
combining of multimedia broadcast multicast service (MBMS) services
(MTCH and MCCH) in multi-cell transmission. The MCH supports
semi-static resource allocation. The MCH is mapped to the PMCH.
[0020] Retransmission control according to a hybrid ARQ (HARQ) is
applied to an uplink shared channel (UL-SCH) among the uplink
transport channels. The UL-SCH supports dynamic or semi-static
resource allocation. The UL-SCH is mapped to the physical uplink
shared channel (PUSCH).
[0021] A random access channel (RACH) is limited to control
information. The RACH involves a collision risk. The RACH is mapped
to the physical random access channel (PRACH).
[0022] The HARQ will be described. The HARQ is the technique for
improving the communication quality of a channel by combination of
automatic repeat request (ARQ) and error correction (forward error
correction). The HARQ is advantageous in that error correction
functions effectively by retransmission even for a channel whose
communication quality changes. In particular, it is also possible
to achieve further quality improvement in retransmission through
combination of the reception results of the first transmission and
the reception results of the retransmission.
[0023] An example of the retransmission method will be described.
If the receiver fails to successfully decode the received data, in
other words, if a cyclic redundancy check (CRC) error occurs
(CRC=NG), the receiver transmits "Nack" to the transmitter. The
transmitter that has received "Nack" retransmits the data. If the
receiver successfully decodes the received data, in other words, if
a CRC error does not occur (CRC=OK), the receiver transmits "AcK"
to the transmitter. The transmitter that has received "Ack"
transmits the next data.
[0024] The logical channels described in Non-Patent Document 1
(Chapter 6) will be described. A broadcast control channel (BCCH)
is a downlink channel for broadcast system control information. The
BCCH that is a logical channel is mapped to the broadcast channel
(BCH) or downlink shared channel (DL-SCH) that is a transport
channel.
[0025] A paging control channel (PCCH) is a downlink channel for
transmitting paging information and system information change
notifications. The PCCH is used when the network does not know the
cell location of a communication terminal. The PCCH that is a
logical channel is mapped to the paging channel (PCH) that is a
transport channel.
[0026] A common control channel (CCCH) is a channel for
transmission control information between communication terminals
and a base station. The CCCH is used in the case where the
communication terminals have no RRC connection with the network. In
the downlink direction, the CCCH is mapped to the downlink shared
channel (DL-SCH) that is a transport channel. In the uplink
direction, the CCCH is mapped to the uplink shared channel (UL-SCH)
that is a transport channel.
[0027] A multicast control channel (MCCH) is a downlink channel for
point-to-multipoint transmission. The MCCH is used for transmission
of MBMS control information for one or several MTCHs from a network
to a communication terminal. The MCCH is used only by a
communication terminal during reception of the MBMS. The MCCH is
mapped to the multicast channel (MCH) that is a transport
channel.
[0028] A dedicated control channel (DCCH) is a channel that
transmits dedicated control information between a communication
terminal and a network on a point-to-point basis. The DCCH is used
when the communication terminal has an RRC connection. The DCCH is
mapped to the uplink shared channel (UL-SCH) in uplink and mapped
to the downlink shared channel (DL-SCH) in downlink.
[0029] A dedicated traffic channel (DTCH) is a point-to-point
communication channel for transmission of user information to a
dedicated communication terminal. The DTCH exists in uplink as well
as downlink. The DTCH is mapped to the uplink shared channel
(UL-SCH) in uplink and mapped to the downlink shared channel
(DL-SCH) in downlink.
[0030] A multicast traffic channel (MTCH) is a downlink channel for
traffic data transmission from a network to a communication
terminal. The MTCH is a channel used only by a communication
terminal during reception of the MBMS. The MTCH is mapped to the
multicast channel (MCH).
[0031] CGI represents a cell global identifier. ECGI represents an
E-UTRAN cell global identifier. A closed subscriber group (CSG)
cell is introduced in the LTE, and the long term evolution advanced
(LTE-A) and universal mobile telecommunication system (UMTS)
described below.
[0032] The closed subscriber group (CSG) cell is a cell in which
subscribers who are allowed use are specified by an operator
(hereinafter, also referred to as a "cell for specific
subscribers"). The specified subscribers are allowed to access one
or more cells of a public land mobile network (PLMN). One or more
cells to which the specified subscribers are allowed access are
referred to as "CSG cell(s)". Note that access is limited in the
PLMN.
[0033] The CSG cell is part of the PLMN that broadcasts a specific
CSG identity (CSG ID) and broadcasts "TRUE" in a CSG indication.
The authorized members of the subscriber group who have registered
in advance access the CSG cells using the CSG ID that is the access
permission information.
[0034] The CSG ID is broadcast by the CSG cell or cells. A
plurality of CSG IDs exist in the LTE communication system. The CSG
IDs are used by communication terminals (UEs) for making access
from CSG-related members easier.
[0035] The locations of communication terminals are tracked based
on an area composed of one or more cells. The locations are tracked
for enabling tracking the locations of communication terminals and
calling communication terminals, in other words, incoming calling
to communication terminals even in an idle state. An area for
tracking locations of communication terminals is referred to as a
tracking area.
[0036] 3GPP is studying base stations referred to as Home-NodeB
(Home-NB; HNB) and Home-eNodeB (Home-eNB; HeNB). HNB/HeNB is a base
station for, for example, household, corporation, or commercial
access service in UTRAN/E-UTRAN. Non-Patent Document 2 discloses
three different modes of the access to the HeNB and HNB.
Specifically, an open access mode, a closed access mode, and a
hybrid access mode are disclosed.
[0037] Further, 3GPP is pursuing specifications standard of long
term evolution advanced (LTE-A) as Release 10 (see Non-Patent
Documents 3 and 4). The LTE-A is based on the LTE radio
communication system and is configured by adding several new
techniques to the system.
[0038] Carrier aggregation (CA) is studied for the LTE-A system, in
which two or more component carriers (CCs) are aggregated to
support wider transmission bandwidths up to 100 MHz. Non-Patent
Document 1 describes the CA.
[0039] In the case where CA is configured, a UE has a single RRC
connection with a network (NW). In RRC connection, one serving cell
provides NAS mobility information and security input. This cell is
referred to as a primary cell (PCell). In downlink, a carrier
corresponding to PCell is a downlink primary component carrier (DL
PCC). In uplink, a carrier corresponding to PCell is an uplink
primary component carrier (UL PCC).
[0040] A secondary cell (SCell) is configured to form a pair of a
PCell and a serving cell, in accordance with the UE capability. In
downlink, a carrier corresponding to SCell is a downlink secondary
component carrier (DL SCC). In uplink, a carrier corresponding to
SCell is an uplink secondary component carrier (UL SCC).
[0041] A pair of one PCell and a serving cell configured by one or
more SCells is configured for one UE.
[0042] The new techniques in the LTE-A include the technique of
supporting wider bands (wider bandwidth extension) and the
coordinated multiple point transmission and reception (CoMP)
technique. The CoMP studied for LTE-A in 3GPP is described in
Non-Patent Document 1.
[0043] Furthermore, 3GPP is studying the use of small eNB s
(hereinafter also referred to as "small-scale base station
devices") configuring small cells to satisfy tremendous traffic in
the future. In an example technique under study, etc., a large
number of small eNBs will be installed to configure a large number
of small cells, thus increasing spectral efficiency and
communication capacity. The specific techniques include dual
connectivity (abbreviated as DC) in which a UE communicates with
two eNBs through connection thereto. Non-Patent Document 1
describes the DC.
[0044] Among eNBs that perform dual connectivity (DC), one of them
may be referred to as a master eNB (abbreviated as MeNB), and the
other may be referred to as a secondary eNB (abbreviated as
SeNB).
[0045] The traffic flow of a mobile network is on the rise, and the
communication rate is also increasing. It is expected that the
communication rate will be further increased when the operations of
the LTE and the LTE-A are fully initiated.
[0046] For increasingly sophisticated mobile communications, the
fifth generation (hereinafter also referred to as "5G") radio
access system is studied, whose service is aimed to be launched in
2020 and afterward. For example, in the Europe, an organization
named METIS summarizes the requirements for 5G (see Non-Patent
Document 5).
[0047] Among the requirements in the 5G radio access system are a
system capacity 1000 times as high as, a data transmission rate 100
times as high as, a data latency one tenth ( 1/10) as low as, and
simultaneously connected communication terminals 100 times as many
as those in the LTE system, to further reduce the power consumption
and device cost.
[0048] To satisfy such requirements, 3GPP is pursuing the study of
5G standards as Release 14 (see Non-Patent Documents 6 and 7). The
techniques on 5G radio sections are referred to as "New Radio
(abbreviated as NR) Access Technology", and the several new
techniques are being studied (see Non-Patent Documents 8 to 11).
Examples of the techniques include a NR frame structure using a
self-contained subframe, and precoding using an uplink sounding
reference signal (SRS).
PRIOR-ART DOCUMENTS
Non-Patent Documents
[0049] Non-Patent Document 1: 3GPP TS36.300 V13.4.0 [0050]
Non-Patent Document 2: 3GPP S1-083461 [0051] Non-Patent Document 3:
3GPP TR 36.814 V9.0.0 [0052] Non-Patent Document 4: 3GPP TR 36.912
V13.0.0 [0053] Non-Patent Document 5: "Scenarios, requirements and
KPIs for 5G mobile and wireless system", [online], Apr. 30, 2013,
ICT-317669-METIS/D1.1, [Searched on Sep. 16, 2016], Internet
<https://www.metis2020.com/documents/deliverables/> [0054]
Non-Patent Document 6: 3GPP TR 23.799 V0.7.0 [0055] Non-Patent
Document 7: 3GPP TR 38.912 V0.0.1 [0056] Non-Patent Document 8:
3GPP RP-160697 [0057] Non-Patent Document 9: 3GPP R1-164032 [0058]
Non-Patent Document 10: 3GPP R1-165887 [0059] Non-Patent Document
11: 3GPP R1-166880
SUMMARY
Problems to be Solved by the Invention
[0060] 5G requires performance, for example, a data transmission
rate 100 times as high as and a data latency one tenth ( 1/10) as
low as those in the LTE system.
[0061] To reduce latency, a proposal is made on a self-contained
subframe consisting of downlink and uplink in one subframe as an NR
frame structure. A response to the downlink is returned in the same
subframe in the self-contained subframe (see Non-Patent Document
9).
[0062] The self-contained subframe has an interval (hereinafter
also referred to as a "gap") for a UE during a shift from the
downlink to the uplink to demodulate and decode a downlink signal,
generate an uplink signal to be coded, and code and modulate the
uplink signal.
[0063] Another proposal is made on retransmission from an eNB to
the UE in the next subframe in the self-contained subframe, in
response to the PUCCH from the UE, particularly, in response to a
Nack signal. For example, Non-Patent Document 11 proposes providing
a gap for the eNB to demodulate and decode the PUCCH, generate a
retransmission signal, and code and modulate the retransmission
signal after the UE transmits the uplink signal.
[0064] Thus, when the self-contained subframe is used, the gap
duration is useless, and the use efficiency of resources decreases.
Providing the gap duration reduces the number of symbols allocable
to an uplink signal. This causes overlap in transmission timing
between an uplink control signal such as Ack/Nack and the SRS, and
decrease in the number of transmissions of the SRS. Thus, the
precoding performance will degrade. Consequently, a problem of
decrease in the transmission rate occurs.
[0065] The object of the present invention is to provide a
communication system capable of suppressing decrease in the
transmission rate.
Means to Solve the Problems
[0066] A communication system according to the present invention
includes a base station device and a communication terminal device
capable of radio communication with the base station device,
wherein the base station device communicates with the communication
terminal device using a self-contained subframe, the self-contained
subframe including a downlink signal to be transmitted from the
base station device to the communication terminal device, and an
uplink signal to be transmitted from the communication terminal
device to the base station device in response to the downlink
signal, the uplink signal has a structure including an uplink
control signal indicating information for controlling transmission
of the uplink signal, and uplink user data to be transmitted before
and after the uplink control signal, and the base station device
notifies the communication terminal device of the structure of the
uplink signal.
Effects of the Invention
[0067] In a communication system according to the present
invention, a base station device communicates with a communication
terminal device using a self-contained subframe including a
downlink signal and an uplink signal. The base station device
notifies the communication terminal device of a structure of the
uplink signal. This enables the communication terminal device to
recognize the structure of the uplink signal in the self-contained
subframe. Thus, the communication terminal device can transmit the
uplink signal using the self-contained subframe.
[0068] Since the uplink signal includes an uplink control signal,
and uplink user data to be transmitted before and after the uplink
control signal, a gap duration between the downlink signal and the
uplink signal during which the uplink signal and the downlink
signal are not transmitted can be reduced. The retransmission of
the downlink signal in the next self-contained subframe can be
performed with the gap duration after transmitting the uplink
signal eliminated or reduced. Consequently, the radio resources can
be efficiently used. Thus, decrease in the transmission rate with
the self-contained subframe can be suppressed.
[0069] These and other objects, features, aspects and advantages of
the present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0070] FIG. 1 is a diagram illustrating the configuration of a
radio frame for use in an LTE communication system.
[0071] FIG. 2 is a block diagram showing the overall configuration
of an LTE communication system 200 under discussion of 3GPP.
[0072] FIG. 3 is a block diagram showing the configuration of a
user equipment 202 shown in FIG. 2, which is a communication
terminal according to the present invention.
[0073] FIG. 4 is a block diagram showing the configuration of a
base station 203 shown in FIG. 2, which is a base station according
to the present invention.
[0074] FIG. 5 is a block diagram showing the configuration of an
MME according to the present invention.
[0075] FIG. 6 is a flowchart showing an outline from a cell search
to an idle state operation performed by a communication terminal
(UE) in the LTE communication system.
[0076] FIG. 7 shows the concept of a cell configuration when macro
eNBs and small eNBs coexist.
[0077] FIG. 8 illustrates an example sequence on setting a gap
after transmission of an uplink signal in a self-contained
subframe.
[0078] FIG. 9 illustrates an example uplink signal structure in the
self-contained subframe.
[0079] FIG. 10 illustrates an example sequence on setting the
uplink signal structure in the self-contained subframe.
[0080] FIG. 11 illustrates an example method for scheduling one
frame ahead according to the second modification of the first
embodiment.
[0081] FIG. 12 illustrates the example method for scheduling one
frame ahead according to the second modification of the first
embodiment.
[0082] FIG. 13 illustrates an example method for scheduling
retransmission two frames ahead according to the second
modification of the first embodiment.
[0083] FIG. 14 illustrates the example method for scheduling
retransmission two frames ahead according to the second
modification of the first embodiment.
[0084] FIG. 15 illustrates an example method for scheduling the
initial transmission and retransmission two frames ahead according
to the second modification of the first embodiment.
[0085] FIG. 16 illustrates the example method for scheduling the
initial transmission and retransmission two frames ahead according
to the second modification of the first embodiment.
[0086] FIG. 17 illustrates an example method for scheduling one
frame ahead when retransmission is performed once according to the
third modification of the first embodiment.
[0087] FIG. 18 illustrates the example method for scheduling one
frame ahead when retransmission is performed once according to the
third modification of the first embodiment.
[0088] FIG. 19 illustrates an example method for scheduling
retransmission two frames ahead when the retransmission is
performed once according to the third modification of the first
embodiment.
[0089] FIG. 20 illustrates the example method for scheduling
retransmission two frames ahead when the retransmission is
performed once according to the third modification of the first
embodiment.
[0090] FIG. 21 illustrates an example method for scheduling the
initial transmission and retransmission two frames ahead when the
retransmission is performed once according to the third
modification of the first embodiment
[0091] FIG. 22 illustrates the example method for scheduling the
initial transmission and retransmission two frames ahead when the
retransmission is performed once according to the third
modification of the first embodiment
[0092] FIG. 23 illustrates an example method for scheduling one
frame ahead according to the fourth modification of the first
embodiment.
[0093] FIG. 24 illustrates the example method for scheduling one
frame ahead according to the fourth modification of the first
embodiment.
[0094] FIG. 25 illustrates an example method for scheduling one
frame ahead when retransmission is performed once according to the
fourth modification of the first embodiment.
[0095] FIG. 26 illustrates the example method for scheduling one
frame ahead when retransmission is performed once according to the
fourth modification of the first embodiment.
[0096] FIG. 27 illustrates an example method for scheduling one
frame ahead according to the fifth modification of the first
embodiment.
[0097] FIG. 28 illustrates the example method for scheduling one
frame ahead according to the fifth modification of the first
embodiment.
[0098] FIG. 29 illustrates an example method for scheduling one
frame ahead when retransmission is performed once according to the
fifth modification of the first embodiment.
[0099] FIG. 30 illustrates the example method for scheduling one
frame ahead when retransmission is performed once according to the
fifth modification of the first embodiment.
[0100] FIG. 31 illustrates an example method for scheduling one
frame ahead according to the sixth modification of the first
embodiment.
[0101] FIG. 32 illustrates the example method for scheduling one
frame ahead according to the sixth modification of the first
embodiment.
[0102] FIG. 33 illustrates an example method for scheduling one
frame ahead when retransmission is performed once according to the
sixth modification of the first embodiment.
[0103] FIG. 34 illustrates the example method for scheduling one
frame ahead when retransmission is performed once according to the
sixth modification of the first embodiment.
[0104] FIG. 35 illustrates an example method for scheduling one
frame ahead according to the seventh modification of the first
embodiment.
[0105] FIG. 36 illustrates the example method for scheduling one
frame ahead according to the seventh modification of the first
embodiment.
[0106] FIG. 37 illustrates an example method for scheduling one
frame ahead when retransmission is performed once according to the
seventh modification of the first embodiment.
[0107] FIG. 38 illustrates the example method for scheduling one
frame ahead when retransmission is performed once according to the
seventh modification of the first embodiment.
[0108] FIG. 39 illustrates a method for setting a SRS transmission
period according to the second embodiment.
[0109] FIG. 40 illustrates a method for transmitting a periodic SRS
when a SRS transmission offset is set together with the SRS
transmission period.
[0110] FIG. 41 illustrates a method for transmitting the periodic
SRS when the SRS transmission offset is set together with the SRS
transmission period.
[0111] FIG. 42 illustrates a method for transmitting the periodic
SRS when the SRS transmission offset is set together with the SRS
transmission period.
[0112] FIG. 43 illustrates an example sequence for setting the SRS
transmission period according to the second embodiment.
[0113] FIG. 44 illustrates an example SRS transmission sequence
when a plurality of subframes in which a SRS can be transmitted are
configured.
[0114] FIG. 45 illustrates an example SRS transmission sequence
when the plurality of subframes in which the SRS can be transmitted
are configured to change a SRS subframe structure.
[0115] FIG. 46 illustrates the example SRS transmission sequence
when the plurality of subframes in which the SRS can be transmitted
are configured to change the SRS subframe structure.
[0116] FIG. 47 illustrates an example sequence for transmitting SRS
period change request information from the UE according to the
second modification of the second embodiment.
[0117] FIG. 48 illustrates a conflict in transmission timing
between Ack/Nack and the SRS in the LTE.
[0118] FIG. 49 illustrates one example of frequency-division
multiplexing an uplink control signal with the SRS in the same
symbol and transmitting the resulting signal according to the third
embodiment.
[0119] FIG. 50 illustrates another example of frequency-division
multiplexing the uplink control signal with the SRS in the same
symbol and transmitting the resulting signal according to the third
embodiment.
[0120] FIG. 51 illustrates yet another example of
frequency-division multiplexing the uplink control signal with the
SRS in the same symbol and transmitting the resulting signal
according to the third embodiment.
[0121] FIG. 52 illustrates one example of increasing the number of
UL symbols by one symbol and time-division multiplexing Ack/Nack
with the SRS.
[0122] FIG. 53 illustrates another example of increasing the number
of UL symbols by one symbol and time-division multiplexing Ack/Nack
with the SRS.
[0123] FIG. 54 illustrates the uplink signal from the UE when an
eNB is configured by a plurality of TRPs.
[0124] FIG. 55 illustrates the timing of receiving, by TRPs, the
uplink signal transmitted from a UE 1.
[0125] FIG. 56 illustrates the timing of receiving, by the TRPs,
the uplink signal transmitted from the UE 1 when an adjustment
value .alpha. is provided.
[0126] FIG. 57 illustrates an example structure of the uplink
signal.
[0127] FIG. 58 illustrates an example sequence for setting an
adjustment value for an uplink transmission timing according to the
fourth embodiment.
[0128] FIG. 59 illustrates the example sequence for setting the
adjustment value for the uplink transmission timing according to
the fourth embodiment.
[0129] FIG. 60 illustrates the example sequence for setting the
adjustment value for the uplink transmission timing according to
the fourth embodiment.
[0130] FIG. 61 illustrates the reception timing by the TRPs when an
adjustment value .beta. is provided for the uplink signal which is
transmitted from the UE 1 and to which a gCP has been added.
[0131] FIG. 62 illustrates an example of setting the gCP to a part
of consecutive uplink signals.
[0132] FIG. 63 illustrates another example of setting the gCP to a
part of consecutive uplink signals.
[0133] FIG. 64 illustrates the timing of receiving, by the TRPs,
the uplink signal transmitted from the UE 1 when an adjustment
value .gamma. is provided in a structure with GTs.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0134] FIG. 2 is a block diagram showing an overall configuration
of an LTE communication system 200, which is under discussion of
3GPP. FIG. 2 will be described. A radio access network is referred
to as an evolved universal terrestrial radio access network
(E-UTRAN) 201. A user equipment device (hereinafter, referred to as
a "user equipment (UE)") 202 that is a communication terminal
device is capable of radio communication with a base station device
(hereinafter, referred to as a "base station (E-UTRAN Node B:
eNB)") 203 and transmits and receives signals through radio
communication.
[0135] Here, the "communication terminal device" covers not only a
user equipment device such as a movable mobile phone terminal
device, but also an unmovable device such as a sensor. In the
following description, the "communication terminal device" may be
simply referred to as a "communication terminal".
[0136] The E-UTRAN is composed of one or a plurality of base
stations 203, provided that a control protocol for the user
equipment 202 such as a radio resource control (RRC), and user
planes such as a packet data convergence protocol (PDCP), radio
link control (RLC), medium access control (MAC), or physical layer
(PHY) are terminated in the base station 203.
[0137] The control protocol radio resource control (RRC) between
the user equipment 202 and the base station 203 performs broadcast,
paging, RRC connection management, and the like. The states of the
base station 203 and the user equipment 202 in RRC are classified
into RRC_IDLE and RRC_CONNECTED.
[0138] In RRC_IDLE, public land mobile network (PLMN) selection,
system information (SI) broadcast, paging, cell re-selection,
mobility, and the like are performed. In RRC_CONNECTED, the user
equipment has RRC connection and is capable of transmitting and
receiving data to and from a network. In RRC_CONNECTED, for
example, handover (HO) and measurement of a neighbor cell are
performed.
[0139] The base stations 203 are classified into eNBs 207 and
Home-eNBs 206. The communication system 200 includes an eNB group
203-1 including a plurality of eNBs 207 and a Home-eNB group 203-2
including a plurality of Home-eNBs 206. A system, composed of an
evolved packet core (EPC) being a core network and an E-UTRAN 201
being a radio access network, is referred to as an evolved packet
system (EPS). The EPC being a core network and the E-UTRAN 201
being a radio access network may be collectively referred to as a
"network".
[0140] The eNB 207 is connected to an MME/S-GW unit (hereinafter,
also referred to as an "MME unit") 204 including a mobility
management entity (MME), a serving gateway (S-GW), or an MME and an
S-GW by means of an S1 interface, and control information is
communicated between the eNB 207 and the MME unit 204. A plurality
of MME units 204 may be connected to one eNB 207. The eNBs 207 are
connected to each other by means of an X2 interface, and control
information is communicated between the eNBs 207.
[0141] The Home-eNB 206 is connected to the MME unit 204 by means
of an S1 interface, and control information is communicated between
the Home-eNB 206 and the MME unit 204. A plurality of Home-eNBs 206
are connected to one MME unit 204. Or, the Home-eNBs 206 are
connected to the MME units 204 through a Home-eNB gateway (HeNBGW)
205. The Home-eNB 206 is connected to the HeNBGW 205 by means of an
S1 interface, and the HeNBGW 205 is connected to the MME unit 204
by means of an S1 interface.
[0142] One or a plurality of Home-eNBs 206 are connected to one
HeNBGW 205, and information is communicated therebetween through an
S1 interface. The HeNBGW 205 is connected to one or a plurality of
MME units 204, and information is communicated therebetween through
an S1 interface.
[0143] The MME units 204 and HeNBGW 205 are entities of higher
layer, specifically, higher nodes, and control the connections
between the user equipment (UE) 202 and the eNB 207 and the
Home-eNB 206 being base stations. The MME units 204 configure an
EPC being a core network. The base station 203 and the HeNBGW 205
configure the E-UTRAN 201.
[0144] Further, 3GPP is studying the configuration below. The X2
interface between the Home-eNBs 206 is supported. In other words,
the Home-eNBs 206 are connected to each other by means of an X2
interface, and control information is communicated between the
Home-eNBs 206. The HeNBGW 205 appears to the MME unit 204 as the
Home-eNB 206. The HeNBGW 205 appears to the Home-eNB 206 as the MME
unit 204.
[0145] The interfaces between the Home-eNBs 206 and the MME units
204 are the same, which are the S1 interfaces, in both cases where
the Home-eNB 206 is connected to the MME unit 204 through the
HeNBGW 205 and it is directly connected to the MME unit 204.
[0146] The base station device 203 may configure a single cell or a
plurality of cells. Each cell has a range predetermined as a
coverage in which the cell can communicate with the user equipment
202 and performs radio communication with the user equipment 202
within the coverage. In the case where one base station device 203
configures a plurality of cells, every cell is configured so as to
communicate with the user equipment 202.
[0147] FIG. 3 is a block diagram showing the configuration of the
user equipment 202 of FIG. 2 that is a communication terminal
according to the present invention. The transmission process of the
user equipment 202 shown in FIG. 3 will be described. First, a
transmission data buffer unit 303 stores the control data from a
protocol processing unit 301 and the user data from an application
unit 302. The data stored in the transmission data buffer unit 303
is passed to an encoding unit 304 and is subjected to an encoding
process such as error correction. There may exist the data output
from the transmission data buffer unit 303 directly to a modulating
unit 305 without the encoding process. The data encoded by the
encoding unit 304 is modulated by the modulating unit 305. The
modulated data is converted into a baseband signal, and the
baseband signal is output to a frequency converting unit 306 and is
then converted into a radio transmission frequency. After that, a
transmission signal is transmitted from an antenna 307 to the base
station 203.
[0148] The user equipment 202 executes the reception process as
follows. The radio signal from the base station 203 is received
through the antenna 307. The received signal is converted from a
radio reception frequency into a baseband signal by the frequency
converting unit 306 and is then demodulated by a demodulating unit
308. The demodulated data is passed to a decoding unit 309 and is
subjected to a decoding process such as error correction. Among the
pieces of decoded data, the control data is passed to the protocol
processing unit 301, and the user data is passed to the application
unit 302. A series of processes by the user equipment 202 is
controlled by a control unit 310. This means that, though not shown
in FIG. 3, the control unit 310 is connected to the individual
units 301 to 309.
[0149] FIG. 4 is a block diagram showing the configuration of the
base station 203 of FIG. 2 that is a base station according to the
present invention. The transmission process of the base station 203
shown in FIG. 4 will be described. An EPC communication unit 401
performs data transmission and reception between the base station
203 and the EPC (such as the MME unit 204), HeNBGW 205, and the
like. A communication with another base station unit 402 performs
data transmission and reception to and from another base station.
The EPC communication unit 401 and the communication with another
base station unit 402 each transmit and receive information to and
from a protocol processing unit 403. The control data from the
protocol processing unit 403, and the user data and the control
data from the EPC communication unit 401 and the communication with
another base station unit 402 are stored in a transmission data
buffer unit 404.
[0150] The data stored in the transmission data buffer unit 404 is
passed to an encoding unit 405 and is then subjected to an encoding
process such as error correction. There may exist the data output
from the transmission data buffer unit 404 directly to a modulating
unit 406 without the encoding process. The encoded data is
modulated by the modulating unit 406. The modulated data is
converted into a baseband signal, and the baseband signal is output
to a frequency converting unit 407 and is then converted into a
radio transmission frequency. After that, a transmission signal is
transmitted from an antenna 408 to one or a plurality of user
equipments 202.
[0151] The reception process of the base station 203 is executed as
follows. A radio signal from one or a plurality of user equipments
202 is received through the antenna 408. The received signal is
converted from a radio reception frequency into a baseband signal
by the frequency converting unit 407, and is then demodulated by a
demodulating unit 409. The demodulated data is passed to a decoding
unit 410 and is then subjected to a decoding process such as error
correction. Among the pieces of decoded data, the control data is
passed to the protocol processing unit 403, the EPC communication
unit 401, or the communication with another base station unit 402,
and the user data is passed to the EPC communication unit 401 and
the communication with another base station unit 402. A series of
processes by the base station 203 is controlled by a control unit
411. This means that, though not shown in FIG. 4, the control unit
411 is connected to the individual units 401 to 410.
[0152] FIG. 5 is a block diagram showing the configuration of the
MME according to the present invention. FIG. 5 shows the
configuration of an MME 204a included in the MME unit 204 shown in
FIG. 2 described above. A PDN GW communication unit 501 performs
data transmission and reception between the MME 204a and the PDN
GW. A base station communication unit 502 performs data
transmission and reception between the MME 204a and the base
station 203 by means of the S1 interface. In the case where the
data received from the PDN GW is user data, the user data is passed
from the PDN GW communication unit 501 to the base station
communication unit 502 via a user plane communication unit 503 and
is then transmitted to one or a plurality of base stations 203. In
the case where the data received from the base station 203 is user
data, the user data is passed from the base station communication
unit 502 to the PDN GW communication unit 501 via the user plane
communication unit 503 and is then transmitted to the PDN GW.
[0153] In the case where the data received from the PDN GW is
control data, the control data is passed from the PDN GW
communication unit 501 to a control plane control unit 505. In the
case where the data received from the base station 203 is control
data, the control data is passed from the base station
communication unit 502 to the control plane control unit 505.
[0154] A HeNBGW communication unit 504 is provided in the case
where the HeNBGW 205 is provided, which performs data transmission
and reception between the MME 204a and the HeNBGW 205 by means of
the interface (IF) according to an information type. The control
data received from the HeNBGW communication unit 504 is passed from
the HeNBGW communication unit 504 to the control plane control unit
505. The processing results of the control plane control unit 505
are transmitted to the PDN GW via the PDN GW communication unit
501. The processing results of the control plane control unit 505
are transmitted to one or a plurality of base stations 203 by means
of the S1 interface via the base station communication unit 502,
and are transmitted to one or a plurality of HeNBGWs 205 via the
HeNBGW communication unit 504.
[0155] The control plane control unit 505 includes a NAS security
unit 505-1, an SAE bearer control unit 505-2, and an idle state
mobility managing unit 505-3, and performs an overall process for
the control plane. The NAS security unit 505-1 provides, for
example, security of a non-access stratum (NAS) message. The SAE
bearer control unit 505-2 manages, for example, a system
architecture evolution (SAE) bearer. The idle state mobility
managing unit 505-3 performs, for example, mobility management of
an idle state (LTE-IDLE state, which is merely referred to as idle
as well), generation and control of a paging signal in the idle
state, addition, deletion, update, and search of a tracking area of
one or a plurality of user equipments 202 being served thereby, and
tracking area list management.
[0156] The MME 204a distributes a paging signal to one or a
plurality of base stations 203. In addition, the MME 204a performs
mobility control of an idle state. When the user equipment is in
the idle state and an active state, the MME 204a manages a list of
tracking areas. The MME 204a begins a paging protocol by
transmitting a paging message to the cell belonging to a tracking
area in which the UE is registered. The idle state mobility
managing unit 505-3 may manage the CSG of the Home-eNBs 206 to be
connected to the MME 204a, CSG IDs, and a whitelist.
[0157] An example of a cell search method in a mobile communication
system will be described next. FIG. 6 is a flowchart showing an
outline from a cell search to an idle state operation performed by
a communication terminal (UE) in the LTE communication system. When
starting a cell search, in Step ST601, the communication terminal
synchronizes slot timing and frame timing by a primary
synchronization signal (P-SS) and a secondary synchronization
signal (S-SS) transmitted from a neighbor base station.
[0158] The P-SS and S-SS are collectively referred to as a
synchronization signal (SS). Synchronization codes, which
correspond one-to-one to PCIs assigned per cell, are assigned to
the synchronization signals (SSs). The number of PCIs is currently
studied in 504 ways. The 504 ways of PCIs are used for
synchronization, and the PCIs of the synchronized cells are
detected (specified).
[0159] In Step ST602, next, the user equipment detects a
cell-specific reference signal (CRS) being a reference signal (RS)
transmitted from the base station per cell and measures the
reference signal received power (RSRP). The codes corresponding
one-to-one to the PCIs are used for the reference signal RS.
Separation from another cell is enabled by correlation using the
code. The code for RS of the cell is derived from the PCI specified
in Step ST601, so that the RS can be detected and the RS received
power can be measured.
[0160] In Step ST603, next, the user equipment selects the cell
having the best RS received quality, for example, the cell having
the highest RS received power, that is, the best cell, from one or
more cells that have been detected up to Step ST602.
[0161] In Step ST604, next, the user equipment receives the PBCH of
the best cell and obtains the BCCH that is the broadcast
information. A master information block (MIB) containing the cell
configuration information is mapped to the BCCH over the PBCH.
Accordingly, the MIB is obtained by obtaining the BCCH through
reception of the PBCH. Examples of the MIB information include the
downlink (DL) system bandwidth (also referred to as a transmission
bandwidth configuration (dl-bandwidth)), the number of transmission
antennas, and a system frame number (SFN).
[0162] In Step ST605, next, the user equipment receives the DL-SCH
of the cell based on the cell configuration information of the MIB,
to thereby obtain a system information block (SIB) 1 of the
broadcast information BCCH. The SIB1 contains the information about
the access to the cell, information about cell selection, and
scheduling information on another SIB (SIBk; k is an integer equal
to or greater than two). In addition, the SIB1 contains a tracking
area code (TAC).
[0163] In Step ST606, next, the communication terminal compares the
TAC of the SIB1 received in Step ST605 with the TAC portion of a
tracking area identity (TAI) in the tracking area list that has
already been possessed by the communication terminal. The tracking
area list is also referred to as a TAI list. TAI is the
identification information for identifying tracking areas and is
composed of a mobile country code (MCC), a mobile network code
(MNC), and a tracking area code (TAC). MCC is a country code. MNC
is a network code. TAC is the code number of a tracking area.
[0164] If the result of the comparison of Step ST606 shows that the
TAC received in Step ST605 is identical to the TAC included in the
tracking area list, the user equipment enters an idle state
operation in the cell. If the comparison shows that the TAC
received in Step ST605 is not included in the tracking area list,
the communication terminal requires a core network (EPC) including
MME and the like to change a tracking area through the cell for
performing tracking area update (TAU).
[0165] The device configuring a core network (hereinafter, also
referred to as a "core-network-side device") updates the tracking
area list based on an identification number (such as UE-ID) of a
communication terminal transmitted from the communication terminal
together with a TAU request signal. The core-network-side device
transmits the updated tracking area list to the communication
terminal. The communication terminal rewrites (updates) the TAC
list of the communication terminal based on the received tracking
area list. After that, the communication terminal enters the idle
state operation in the cell.
[0166] Widespread use of smartphones and tablet terminal devices
explosively increases traffic in cellular radio communications,
causing a fear of insufficient radio resources all over the world.
To increase spectral efficiency, thus, it is studied to downsize
cells for further spatial separation.
[0167] In the conventional configuration of cells, the cell
configured by an eNB has a relatively-wide-range coverage.
Conventionally, cells are configured such that
relatively-wide-range coverages of a plurality of cells configured
by a plurality of macro eNBs cover a certain area.
[0168] When cells are downsized, the cell configured by an eNB has
a narrow-range coverage compared with the coverage of a cell
configured by a conventional eNB. Thus, in order to cover a certain
area as in the conventional case, a larger number of downsized eNBs
than the conventional eNBs are required.
[0169] In the description below, a "macro cell" refers to a cell
having a relatively wide coverage, such as a cell configured by a
conventional eNB, and a "macro eNB" refers to an eNB configuring a
macro cell. A "small cell" refers to a cell having a relatively
narrow coverage, such as a downsized cell, and a "small eNB" refers
to an eNB configuring a small cell.
[0170] The macro eNB may be, for example, a "wide area base
station" described in Non-Patent Document 7.
[0171] The small eNB may be, for example, a low power node, local
area node, or hotspot. Alternatively, the small eNB may be a pico
eNB configuring a pico cell, a femto eNB configuring a femto cell,
HeNB, remote radio head (RRH), remote radio unit (RRU), remote
radio equipment (RRE), or relay node (RN). Still alternatively, the
small eNB may be a "local area base station" or "home base station"
described in Non-Patent Document 7.
[0172] FIG. 7 shows the concept of the cell configuration in which
macro eNBs and small eNBs coexist. The macro cell configured by a
macro eNB has a relatively-wide-range coverage 701. A small cell
configured by a small eNB has a coverage 702 whose range is
narrower than that of the coverage 701 of a macro eNB (macro
cell).
[0173] When a plurality of eNBs coexist, the coverage of the cell
configured by an eNB may be included in the coverage of the cell
configured by another eNB. In the cell configuration shown in FIG.
7, as indicated by a reference "704" or "705", the coverage 702 of
the small cell configured by a small eNB may be included in the
coverage 701 of the macro cell configured by a macro eNB.
[0174] As indicated by the reference "705", the coverages 702 of a
plurality of, for example, two small cells may be included in the
coverage 701 of one macro cell. A user equipment (UE) 703 is
included in, for example, the coverage 702 of the small cell and
performs communication via the small cell.
[0175] In the cell configuration shown in FIG. 7, as indicated by a
reference "706", the coverage 701 of the macro cell configured by a
macro eNB may overlap the coverages 702 of the small cells
configured by small eNBs in a complicated manner.
[0176] As indicated by a reference "707", the coverage 701 of the
macro cell configured by a macro eNB may not overlap the coverages
702 of the small cells configured by small eNBs.
[0177] Further, as indicated by a reference "708", the coverages
702 of a large number of small cells configured by a large number
of small eNBs may be configured in the coverage 701 of one macro
cell configured by one macro eNB.
[0178] In the LTE, asynchronous and adaptive scheduling is
performed in the downlink, and synchronous and adaptive or
non-adaptive scheduling is performed in the uplink (see Non-Patent
Document 1).
[0179] Here, the synchronous scheduling means scheduling in which
the retransmission timing is predetermined by a relative position
with respect to the initial transmission timing. The asynchronous
scheduling means scheduling for instructing the retransmission
timing by including a process number in the downlink control
information (DCI) and transmitting the process number to a
recipient because the retransmission timing is not predetermined in
the scheduling.
[0180] In the adaptive scheduling, the Modulation and Coding Scheme
(MCS) and the frequency resource allocation can be changed for each
retransmission. In the non-adaptive scheduling, the MCS and the
frequency resource allocation for retransmission can be changed in
a method identical to that for the initial transmission or for the
previous retransmission, or in a predefined method (see 3GPP TS
36.321 V13.2.0 (hereinafter referred to as "Reference 1")).
[0181] In the self-contained subframe proposed as the NR, a
structure principally involving downlink user data and Ack/Nack in
response to the downlink user data, a structure principally
involving an uplink grant and uplink user data according to the
uplink grant, a structure principally involving a downlink
reference signal and a measurement result on the downlink reference
signal, and a structure principally involving a downlink control
signal and the CQI or the sounding reference signal (SRS)
instructed by the downlink control signal are proposed. A structure
in which the downlink is synchronous with the uplink, that is, a
structure in which the times to be allocated to the downlink and
the uplink are the same is also proposed (see Non-Patent Document
9).
[0182] Another proposal is made on providing a gap in a portion
after transmission of an uplink signal in the self-contained
subframe to enable downlink retransmission in the next subframe
upon receipt of Nack and minimize the latency from the receipt of
Nack to the downlink retransmission (see Non-Patent Document
11).
[0183] However, Non-Patent Document 11 fails to disclose a method
for providing a gap in the portion after transmission of the uplink
signal in a subframe. This causes a problem with the UE which can
neither recognize the subframe structure nor receive the downlink
signal and transmit the uplink signal.
[0184] The first embodiment will disclose a method for solving such
a problem. An eNB (a 5G base station will be also referred to as an
"eNB" in the Description) sets, to the UE, a gap after transmission
of the uplink signal according to the first embodiment.
[0185] For example, a gap length after transmission of the uplink
signal may be used in setting the gap after transmission of the
uplink signal. The gap length of the uplink signal may be given,
for example, per minimum time, per symbol, or per another unit in
the 5G radio access system. The gap length after transmission of
the uplink signal may be given as a ratio to the length of the
subframe.
[0186] The gap length after transmission of the uplink signal may
be selected from several options. For example, the eNB may notify
the UE of a list of the options and an identifier indicating a
selection from the list. The list of the options and the identifier
may be notified simultaneously or separately.
[0187] The gap length after transmission of the uplink signal may
have a default value. Examples of a situation requiring the default
value include a time when the UE is connected to the eNB. When
being connected to the eNB, the UE needs to receive the broadcast
information and a paging signal and also to transmit a physical
random access channel. Here, the UE may communicate with the eNB
using a subframe structure corresponding to the default value.
[0188] The default value may be statically determined in a standard
or changeable.
[0189] An absolute value, that is, a necessary length may be
directly given or a relative value may be given as the gap length
after transmission of the uplink signal. For example, a default
value may be used as a basis for giving the gap length using the
relative value, or a difference from the previous setting value may
be given.
[0190] When the gap after transmission of the uplink signal is set,
the gap length to be set may be immediately validated.
[0191] Alternatively, when the gap length to be set is validated
may be notified. The notification may, for example, directly
specify the time when the gap length is validated or specify the
time difference required from the notification to the validation of
the gap length. A subframe number may be used as the time. The
number of subframes may be used as the time difference. This
enables the eNB and the UE to share the timing to change the gap
length, which can prevent the transmission/reception loss between
the eNB and the UE when the gap setting is changed.
[0192] The following (1) to (3) will be disclosed as specific
examples of a method for notifying the gap setting after
transmission of the uplink signal:
[0193] (1) a semi-static setting;
[0194] (2) a dynamic setting; and
[0195] (3) a combination of (1) and (2) above.
[0196] For example, the eNB may broadcast the semi-static setting
in (1) to the UEs being served thereby. The broadcasting may be
performed via, for example, the RRC common signaling. SIB1 or SIB2
may be used as an example of the RRC common signaling.
[0197] The RRC-dedicated signaling may be used as another example
of the semi-static setting in (1). For example, RRC connection
reconfiguration may be used as the RRC-dedicated signaling.
Alternatively, a message 4 in a random access process may be
used.
[0198] For example, the L1/L2 signaling may be used for the dynamic
setting in (2). Since the gap setting can be changed per
Transmission Time Interval (TTI) or per subframe, the gap setting
can be changed with a short period.
[0199] MAC signaling (a MAC control element) may be used as another
example of the dynamic setting in (2). Since retransmission is
controlled in the MAC signaling, the setting can be notified with
high reliability.
[0200] The eNB may make the semi-static and dynamic settings in (3)
for the UE, using different setting details as one combination. For
example, a list of the options of the gap length may be
semi-statically given, and an identifier indicating a selection may
be dynamically given. For example, a default value of the gap
length may be semi-statically notified, and a difference from the
default value may be dynamically set. Consequently, the gap length
after transmission of the uplink signal can be flexibly set with
less amount of signaling.
[0201] The eNB may notify the UE of each piece of configuration
information of a downlink signal, a gap between the downlink signal
and an uplink signal, and the uplink signal to set the gap after
transmission of the uplink signal. The UE may calculate the gap
length after transmission of the uplink signal, based on each piece
of the configuration information. The gap length after transmission
of the uplink signal may be obtained by, for example, subtracting,
from the self-contained subframe, a sum of the lengths of the
downlink signal, the gap between the downlink signal and the uplink
signal, and the uplink signal as a calculation method thereof. The
UE may use a result of the calculation as the gap setting after
transmission of the uplink signal.
[0202] The eNB may notify the UE of each piece of the configuration
information of the downlink signal, the gap between the downlink
signal and the uplink signal, and the uplink signal to set the gap
after transmission of the uplink signal. The UE may calculate the
gap length after transmission of the uplink signal, based on each
piece of the configuration information. The gap length after
transmission of the uplink signal may be obtained by, for example,
subtracting, from the self-contained subframe, a sum of the lengths
of the downlink signal, the gap between the downlink signal and the
uplink signal, and the uplink signal as a calculation method
thereof. The UE may use a result of the calculation as the gap
setting after transmission of the uplink signal.
[0203] The gap after transmission of the uplink signal, the
downlink signal, the gap between the downlink signal and the uplink
signal, and the uplink signal may be set simultaneously or
separately.
[0204] In setting the gap after transmission of the uplink signal
and the gap between the downlink signal and the uplink signal, the
eNB and the UE may change the length of one of the gaps to follow
the change in length of the other gap. For example, a sum of the
lengths of the gap after transmission of the uplink signal and the
gap between the downlink signal and the uplink signal may be
constant.
[0205] The UE may change each piece of the configuration
information of the downlink signal, the gap between the downlink
signal and the uplink signal, and the uplink signal, using the gap
length after transmission of the uplink signal that has been
notified from the eNB. When the eNB notifies the UE of change in
the gap length of the uplink signal, the UE may change the length
of the downlink signal. Alternatively, the gap length between the
downlink signal and the uplink signal may be changed.
Alternatively, the length of the uplink signal may be changed.
Alternatively, the length of the downlink signal, the gap length
between the downlink signal and the uplink signal, and the length
of the uplink signal may be changed in combination. Here, a sum of
the length of the downlink signal, the gap length between the
downlink signal and the uplink signal, the length of the uplink
signal, and the gap length after transmission of the uplink signal
may be constant.
[0206] The following (1) to (4) will be disclosed as specific
examples of a unit for setting a gap after transmission of the
uplink signal:
[0207] (1) constant setting within the eNB;
[0208] (2) setting per UE;
[0209] (3) setting for each HARQ process; and
[0210] (4) combinations of (1) to (3) above.
[0211] (1) may be broadcast to the UE in the eNB. The broadcast
information may be used. The broadcast information may be SIB 1 or
SIB2. (1) may be notified to each UE. The notification for each UE
may be made via the RRC-dedicated signaling, the MAC signaling, or
the L1/L2 signaling.
[0212] (2) may be notified to each UE. (2) may be broadcast to the
UE in the eNB. The broadcast information may be used. The
notification for each UE may be made via the RRC-dedicated
signaling, the MAC signaling, or the L1/L2 signaling.
[0213] (3) may be notified to each UE. In the notification for each
UE, the gap lengths may be collectively or separately transmitted
after transmission of the uplink signal in each HARQ process. In
the notification for each UE, an identifier indicating each HARQ
process may be used. The notification for each UE may be made via
the RRC-dedicated signaling, the MAC signaling, or the L1/L2
signaling.
[0214] (3) may be notified for each HARQ process. The notification
for each HARQ process may be made via the MAC signaling or the
L1/L2 signaling. Consequently, Ack/Nack can be transmitted earlier
in a subframe with less downlink data, and the eNB can perform
processes for decoding and scheduling the Ack/Nack with sufficient
leeway. The sufficient leeway in the processing time allows the eNB
to perform the other processes such as device control.
[0215] The following (1) to (9) will be disclosed as specific
examples of information necessary for the eNB to determine the gap
length after transmission of the uplink signal:
[0216] (1) capability of decoding Ack/Nack by the eNB, for example,
the time required for the decoding by the eNB;
[0217] (2) scheduling capability of the eNB, for example, the time
required for the scheduling by the eNB;
[0218] (3) coding capability of the eNB, for example, the time
required for coding the downlink user data by the eNB;
[0219] (4) decoding capability of the UE, for example, the time
required for decoding the downlink user data by the UE;
[0220] (5) capability of coding Ack/Nack by the UE, for example,
the time required for the coding by the UE;
[0221] (6) the length of the downlink signal;
[0222] (7) the gap length between the downlink signal and the
uplink signal;
[0223] (8) the length of the uplink signal; and
[0224] (9) combinations of (1) to (8) above.
[0225] In (9), for example, the eNB may determine the gap length
after uplink transmission, in consideration of each leeway in the
time from reception of the downlink signal to transmission of
Ack/Nack by the UE and in the time from reception of Ack/Nack to
transmission of the downlink user data in the next subframe by the
eNB.
[0226] A high-level network device may mainly determine the gap
length after transmission of the uplink signal. The high-level
network device may transmit the gap length after transmission of
the uplink signal to the UE via the eNB.
[0227] The following (1) to (3) will be disclosed as specific
examples of a judgment condition for the high-level network device
to mainly determine the gap length after transmission of the uplink
signal:
[0228] (1) the gap length after transmission of the uplink signal
in a neighboring eNB of the eNB;
[0229] (2) a default value of the gap length after transmission of
the uplink signal in the neighboring eNB of the eNB; and
[0230] (3) a combination of (1) and (2) above.
[0231] The high-level network device may transmit a request for
information on (1) to the neighboring eNB of the eNB. The
neighboring eNB of the eNB may transmit the information on (1) to
the high-level network device.
[0232] The high-level network device may transmit a request for
information on (2) to the eNB. The eNB may transmit the information
on (2) to the high-level network device.
[0233] The inter-cell interference can be reduced because the gap
setting after transmission of the uplink signal mainly made by the
high-level network device allows for the setting with consideration
given to states of the other eNBs.
[0234] The eNB and the UE may change a method for scheduling the
downlink signal simultaneously when the eNB sets the gap length
after transmission of the uplink signal to the UE. The eNB may
transmit an identifier indicating the scheduling method to the UE.
Examples of the identifier indicating the scheduling method may
include a flag indicating whether the retransmission in the next
subframe is possible. The identifier indicating the scheduling
method may include the flag.
[0235] The eNB and the UE may change the scheduling method
simultaneously when setting of the gap length after uplink
transmission is validated. The associations of changing the method
for scheduling the downlink signal according to change in setting
of the gap length after uplink transmission may be defined in a
standard. For example, no retransmission allowed in the next
subframe when the gap length after uplink transmission is less than
a predefined threshold may be defined in a standard.
[0236] The eNB and the UE may not change the scheduling for the
downlink signal when the eNB sets the gap length after transmission
of the uplink signal to the UE. The UE may receive the downlink
user data according to a downlink control signal to be transmitted
from the eNB, regardless of whether the eNB sets the gap length
after transmission of the uplink signal to the UE. Alternatively,
the UE may receive the downlink user data according to the
scheduling given from the eNB in advance.
[0237] The scheduling method may be changed for the uplink signal.
The scheduling methods for the downlink signal and the uplink
signal may be changed simultaneously or separately.
[0238] FIG. 8 illustrates an example sequence on setting the gap
length after transmission of the uplink signal in the
self-contained subframe. FIG. 8 illustrates an example where in an
initial connection of the UE, the eNB sets a default value of the
gap length after transmission of the uplink signal using the
broadcast information, and semi-statically sets, after RRC
connection establishment, a UE-dedicated gap length after
transmission of the uplink signal.
[0239] In Step ST800, the eNB broadcasts the default value of the
gap length after uplink transmission to the UE. The broadcast
information may be used in the broadcasting. The broadcast
information may be, for example, SIB 1.
[0240] In Step ST801, the UE reflects the default value of the gap
length after uplink transmission. Then, the UE starts RRC
connection processes with the eNB.
[0241] Steps ST802 to ST806 denote random access processes and the
RRC connection processes.
[0242] In Step ST802, the UE notifies the eNB of an RA preamble.
The RA preamble is notified using, for example, the PRACH.
[0243] In Step ST803, the eNB transmits an RA response to the UE.
The eNB simultaneously notifies the uplink grant information to be
used for transmitting an RRC Connection Request from the UE.
[0244] In Step ST804, the UE transmits the RRC Connection Request
to the eNB. The RRC Connection Request may be transmitted using
radio resources designated by the uplink grant information.
[0245] In Step ST805, the eNB transmits the RRC Connection Setup to
the UE. The RRC Connection Setup may be transmitted together with a
Contention Resolution in a series of the RA sequences of Step ST802
to ST804.
[0246] In Step ST806, the UE notifies the eNB of RRC Connection
Setup Complete. Consequently, the RRC connection between the eNB
and the UE is completed.
[0247] In Step ST807, the eNB determines the gap length after
uplink transmission for the UE.
[0248] In Step ST808, the eNB transmits the determined gap length
after uplink transmission to the UE. The gap length after uplink
transmission may be transmitted via the RRC-dedicated signaling.
The eNB may simultaneously notify information on when the gap
length after uplink transmission is validated.
[0249] In Step ST809, the UE reflects the gap length after uplink
transmission that has been received from the eNB. In Step ST810,
the eNB reflects the gap length after uplink transmission that has
been transmitted to the UE. Consequently, the UE and the eNB
communicate with each other using the new gap length.
[0250] The gap length after uplink transmission may be changed
according to a type of the uplink signal. Examples of the type of
the uplink signal may include uplink user data, Ack/Nack, CQI, CSI,
SRS, and PRACH. Changing the gap length after uplink transmission
according to a type of the uplink signal enables the gap length
after uplink transmission to be set based on a difference in
processing time between uplink signals in the eNB without any
waste.
[0251] The eNB may notify the UE of the gap length after uplink
transmission for each type of the uplink signal as necessary. The
notification may be made via the L1/L2 signaling. Alternatively,
the eNB may notify the UE of a list of gap lengths for the
respective types of the uplink signals. The notification may be
made via the RRC-dedicated signaling, the MAC signaling, or the
L1/L2 signaling. The eNB may simultaneously notify the UE of
identifiers indicating the types of the uplink signals.
[0252] The identifiers may be notified via the L1/L2 signaling.
Alternatively, the eNB may notify the UE of patterns of the types
of the uplink signals for each subframe. The patterns may be
notified via the RRC-dedicated signaling, the MAC signaling, or the
L1/L2 signaling.
[0253] The gap length after uplink transmission may be changed
according to a communication service between the eNB and the UE.
Examples of the service may include enhanced Mobile BroadBand
(eMBB), Ultra Reliability and Low Latency Communication (URLLC),
and massive Machine Type Communication (mMTC).
[0254] Changing the gap length after uplink transmission according
to a communication service between the eNB and the UE enables
setting of the optimal gap length to satisfy the requirements in
each of the services. For example, setting the gap length after
uplink transmission in the URLLC enables the eNB to perform
retransmission in a subframe next to a subframe in which Nack has
been received from the UE. In the eMBB, shortening or eliminating
the gap length after uplink transmission can reduce useless
communication due to the gap and increase the communication
rate.
[0255] The eNB may determine the gap length after uplink
transmission for each service, during the communication between the
eNB and the UE. Alternatively, the gap length may be predetermined
in a standard. The eNB may broadcast the gap length after uplink
transmission for each service, or notify the gap length to each UE.
The broadcast information may be used in the broadcasting. The
broadcast information may be, for example, SIB1 or SIB2. The
notification may be made via the RRC-dedicated signaling.
Alternatively, the notification may be made via the MAC signaling.
Consequently, the eNB and the UE can find the gap setting in a
service to be used, from a combination with the identifier.
[0256] The eNB may notify the UE of a plurality of identifiers
indicating the services. Consequently, when the eNB and the UE
simultaneously adopt a plurality of services, the appropriate gap
setting can be given to each of the services, thus increasing
efficiency in the communication.
[0257] The eNB may notify the UE of an identifier indicating a
service to be used with the UE. The notification may be made via
the RRC-dedicated signaling, the MAC signaling, or the L1/L2
signaling.
[0258] The first embodiment enables the scheduling in the
self-contained subframe using the subframe structure in which a gap
is formed after uplink transmission. Thus, the eNB can perform
retransmission in the next subframe in response to the Ack/Nack
from the UE. This enables communication with low latency.
First Modification of First Embodiment
[0259] The first modification will describe a setting method to
reduce a gap in the self-contained subframe.
[0260] A proposal is made on a frame structure in the NR to reduce
a gap between the downlink signal and the uplink signal and
eliminate a gap after uplink transmission, for example, through
allocation of uplink user data before and after an uplink control
signal such as Ack/Nack (see 3GPP R1-166410 (hereinafter referred
to as "Reference 2")).
[0261] However, Reference 2 fails to disclose a method for
allocating the uplink user data before and after the uplink control
signal, thus causing a problem with the UE which can neither
recognize the subframe structure nor transmit the uplink
signal.
[0262] The first embodiment will disclose a method for solving such
a problem.
[0263] The eNB notifies the UE of a structure of the uplink
signal.
[0264] The following (1) to (4) will be disclosed as specific
examples of information to be notified as the structure of the
uplink signal:
[0265] (1) the type of the uplink signal;
[0266] (2) the length of the uplink signal;
[0267] (3) the start timing of the uplink signal; and
[0268] (4) combinations of (1) to (3) above.
[0269] The type of the uplink signal in (1) may be communicated
using an identifier. Examples of the type of the uplink signal may
include uplink user data, uplink control information, an uplink
reference signal, and a gap. The uplink control information may
include Ack/Nack, CQI, and CSI. Examples of the uplink reference
signal may include a reference signal for demodulating uplink data
and an uplink sounding reference signal.
[0270] The length of the uplink signal in (2) may be given, for
example, per minimum time, per symbol, or per another unit in the
5G radio access system. The length of the uplink signal may be
given as a ratio to the length of the subframe.
[0271] The start timing of the uplink signal in (3) may be given
as, for example, a time from the beginning of a subframe. The start
timing may be given as a time measured backward from the end of the
subframe. The start timing may be given as a time from the end of
the downlink signal.
[0272] The start timing of the uplink signal in (3) may be given,
for example, per minimum time, per symbol, or per another unit in
the 5G radio access system. The start timing of the uplink signal
may be given as a ratio to the length of the subframe.
[0273] A plurality of settings may be possible in (1) to (3) above.
For example, when there are a plurality of types of the uplink
signals to be transmitted in a subframe, the settings in (1) to (3)
above may be used for each of the types of the uplink signals.
[0274] In a structure of the uplink signal according to the first
modification, a signal that does not require a response in the next
subframe may be placed close to the end of the subframe. For
example, the structure of the uplink signal may include the uplink
user data, Ack/Nack, and the uplink user data, and the uplink user
data may be placed at the end of the subframe. Alternatively, an
uplink reference signal may be placed instead of the uplink user
data at the end of the subframe.
[0275] FIG. 9 illustrates one example of a structure of the uplink
signal (hereinafter may be referred to as an "uplink signal
structure") in the self-contained subframe. In FIG. 9, the uplink
signal includes the uplink user data, Ack/Nack, the uplink user
data, and the uplink sounding reference signal. In FIG. 9, the
start timing of each of the uplink signals is given as the timing
for reception in the eNB and as a time from the beginning of the
subframe. For example, the start timing of the first uplink user
data is given as s1, that of Ack/Nack is given as s2, that of the
second uplink user data is given as s3, and that of the uplink
sounding reference signal is given as s4.
[0276] In the first modification, the timing of the uplink signal
may be given as the timing of transmission by the UE. For example,
the start timing of the first uplink user data may be given as t1,
that of Ack/Nack may be given as t2, that of the second uplink user
data may be given as t3, and that of the uplink sounding reference
signal may be given as t4 in the example of FIG. 9.
[0277] In the first modification, when the structure of the uplink
signal to be notified from the eNB to the UE is validated may be
notified together. The notification on when the structure is
validated may, for example, directly specify the time of the
validation or specify the time difference required from the
notification to the validation. A subframe number may be used as
the time. The number of subframes may be used as the time
difference. This enables simultaneous switching of the structure of
the uplink signal between the eNB and the UE, which can prevent the
transmission/reception loss between the eNB and the UE in switching
of the structure of the uplink signal.
[0278] The structure of the uplink signal may be selected from
several options. For example, the eNB may notify the UE of a list
of the options and an identifier indicating a selection from the
list. The list of the options and the identifier may be notified
simultaneously or separately.
[0279] The following (1) to (3) will be disclosed as specific
examples of a method for notifying the structure of the uplink
signal:
[0280] (1) a semi-static setting;
[0281] (2) a dynamic setting; and
[0282] (3) a combination of (1) and (2) above.
[0283] For example, the eNB may broadcast the semi-static setting
in (1) to the UEs being served thereby. The broadcasting may be
performed via, for example, the RRC common signaling. SIB1 or SIB2
may be used as an example of the RRC common signaling.
[0284] The RRC-dedicated signaling may be used as another example
of the semi-static setting in (1). For example, RRC connection
reconfiguration may be used as the RRC-dedicated signaling.
Alternatively, the message 4 in a random access process may be
used.
[0285] The semi-static setting in (1) enables the eNB to notify the
UE of the structure of the uplink signal with less amount of
signaling.
[0286] For example, the L1/L2 signaling may be used for the dynamic
setting in (2). Since the uplink signal structure can be changed
per TTI or per subframe, the uplink signal structure can be changed
with a short period.
[0287] MAC signaling (a MAC control element) may be used as another
example of the dynamic setting in (2). Since retransmission is
controlled in the MAC signaling, the setting can be notified with
high reliability.
[0288] The eNB may make the semi-static and dynamic settings in (3)
for the UE, using different setting details as one combination. For
example, the uplink signal structure to be mainly used may be
semi-statically specified, and the uplink signal structure to be
suddenly used may be dynamically set. Consequently, the gap length
after transmission of the uplink signal can be flexibly set with
less amount of signaling.
[0289] In the first modification, the eNB may collectively notify
the UE of uplink signal structures for a plurality of subframes. In
the uplink signal structures, the uplink signal structures for the
subframes may be different from each other. The uplink signal
structures for the plurality of subframes may be notified using an
identifier indicating a selection from the options. The uplink
signal structures for the plurality of subframes may be notified
together with a subframe number to be a notification target.
[0290] The uplink signal structures for the plurality of subframes
may be notified via the RRC-dedicated signaling, the MAC signaling,
or the L1/L2 signaling. The RRC connection reconfiguration may be
used as an example of the RRC-dedicated signaling.
[0291] The eNB may transmit the downlink signals and receive the
uplink signals for the plurality of subframes, using the uplink
signal structures for the plurality of subframes.
[0292] The UE may receive the downlink signals and transmit the
uplink signals for the plurality of subframes, using the uplink
signal structures for the plurality of subframes.
[0293] The uplink signal structures for the plurality of subframes
may or may not have a validity time limit. When the uplink signal
structures do not have the validity time limit, the eNB and the UE
periodically communicate with each other according to the notified
uplink signal structures. When the uplink signal structures have
the validity time limit, the validity time limit may be once (one
period), or the eNB may notify the UE of a valid number of times or
a validity time separately. Since the communication can be
continued by notifying the uplink signal structures for the
plurality of subframes once from the eNB to the UE, the amount of
signaling can be reduced.
[0294] A default setting for the uplink signal structure may be
provided. Examples of a situation requiring the default setting
include a time when the UE is connected to the eNB. When being
connected to the eNB, the UE needs to receive the broadcast
information and a paging signal and also to transmit a physical
random access channel. Here, the UE may communicate with the eNB
using a subframe structure corresponding to the default
structure.
[0295] The following (1) to (4) will be disclosed as specific
examples of information for the eNB to determine the uplink signal
structure:
[0296] (1) a buffer status of the uplink user data in the UE: the
buffer status is indicated by, for example, information indicating
an amount of remaining buffer or information indicating an amount
of accumulated buffer;
[0297] (2) a channel state between the eNB and the UE;
[0298] (3) the switching time between transmission and reception in
the UE; and
[0299] (4) combinations of (1) to (3) above.
[0300] The UE may notify the eNB of the buffer status of the uplink
user data in (1). The Uplink Control Information (UCI) may be used
for notifying the buffer status. Alternatively, the notification
may be made via the MAC signaling.
[0301] The eNB may make a determination on (2) above based on an
uplink reference signal from the UE. Examples of the uplink
reference signal to be used may include a reference signal for
demodulating uplink data, an uplink sounding reference signal, and
another uplink reference signal. The eNB may use the CQI to be
transmitted from the UE.
[0302] The eNB may inquire of the UE about information indicating
the switching time between transmission and reception in the UE in
(3) above. The UE may notify the eNB of the information indicating
the switching time between transmission and reception in the UE.
The inquiry may be made via the RRC-dedicated signaling. The
notification may be made via the RRC-dedicated signaling. The UE
capability may be used as one example of the information indicating
the switching time between transmission and reception in the
UE.
[0303] In the first modification, information to be used for the
eNB to determine the uplink structure, a method for notifying
necessary information from the UE to the eNB, and a method for
notifying the uplink structure from the eNB to the UE may be
coordinated with one another. For example, the method for notifying
necessary information from the UE to the eNB may be identical to
the method for notifying the uplink structure from the eNB to the
UE. For example, when the eNB determines the uplink structure based
on a buffer status of the uplink user data in the UE, the MAC
signaling may be used as a method for notifying the buffer status
from the UE to the eNB and for notifying the uplink structure from
the eNB to the UE. Consequently, the eNB can determine the uplink
structure and notify the UE of the uplink structure in a method
that follows change in the necessary information with less wasteful
signaling.
[0304] FIG. 10 illustrates an example sequence on setting the
uplink signal structure in the self-contained subframe. FIG. 10
illustrates an example where in an initial connection of the UE,
the eNB sets a default value of the gap length after transmission
of the uplink signal in the broadcast information, and dynamically
sets a UE-dedicated uplink signal structure after RRC connection
establishment. Since the sequence illustrated in FIG. 10 includes
the same Steps as those in the sequence illustrated in FIG. 8, the
same step numbers will be assigned to the same Steps and the common
description thereof will be omitted.
[0305] In FIG. 10, Step ST1000 replaces Step ST800 in FIG. 8. In
Step ST1000, the eNB notifies the UE of the broadcast information
SIB1 including the default setting of the uplink signal structure.
The UE obtains the default setting of the uplink signal structure
that is included in the broadcast information SIB1 transmitted from
the eNB.
[0306] In FIG. 10, Step ST1001 replaces Step ST801 in FIG. 8. In
Step ST1001, the UE reflects the default setting of the uplink
signal structure.
[0307] In FIG. 10, Step ST1002 replaces Step ST807 in FIG. 8. In
Step ST1002, the eNB determines the uplink signal structure.
[0308] In FIG. 10, Step ST1003 replaces Step ST808 in FIG. 8. In
Step ST1003, the eNB notifies the UE of the uplink signal structure
via the L1/L2 signaling.
[0309] In FIG. 10, Step ST1004 replaces Step ST809 in FIG. 8. In
Step ST1004, the UE reflects the uplink signal structure received
from the eNB.
[0310] In FIG. 10, Step ST1005 replaces Step ST810 in FIG. 8. In
Step ST1005, the eNB reflects the uplink signal structure.
[0311] In the first modification, the UE may determine the uplink
signal structure. The UE may notify the eNB of the uplink signal
structure determined as above. The eNB may notify the UE of an
acceptance response or a rejection response to the uplink signal
structure notified from the UE. When simultaneously communicating
with a plurality of eNBs, the UE only needs to notify the plurality
of eNBs of the uplink signal structure once. Thus, signaling to be
generated between the eNB s can be reduced.
[0312] Alternatively, the eNB may not notify the UE of the
rejection response to the uplink signal structure notified from the
UE according to the first modification. Consequently, since the UE
can automatically determine the rejection response, the amount of
signaling can be reduced.
[0313] For another example, the eNB may notify the UE of the uplink
signal structure that can be set, together with the rejection
response. Consequently, the repetition of notification of the
uplink signal structure from the UE and the rejection response from
the eNB can be prevented. Thus, the amount of signaling can be
reduced, and the structure of the uplink signal can be promptly
set.
[0314] The eNB may use a subframe structure of another UE connected
to the UE to determine acceptance or rejection to the uplink signal
structure.
[0315] The following (1) to (4) will be disclosed as specific
examples of information necessary for the UE to determine the
uplink signal structure:
[0316] (1) a buffer status of the uplink user data in the UE: the
buffer status is indicated by, for example, information indicating
an amount of remaining buffer or information indicating an amount
of accumulated buffer;
[0317] (2) a channel state between the eNB and the UE;
[0318] (3) the switching time between transmission and reception in
the UE; and
[0319] (4) combinations of (1) to (3) above.
[0320] The eNB may notify the UE of an uplink channel state in (2).
For example, the MCS may be used as the uplink channel state. For
example, the uplink grant information may include the MCS. The
uplink channel state may be notified via the RRC-dedicated
signaling, using MAC control information, or via uplink L1/L2
signaling.
[0321] The UE may use a downlink channel state in (2). The CQI may
be used as the downlink channel state.
[0322] The UE may notify the eNB of the uplink signal structure via
the RRC-dedicated signaling. Alternatively, the MAC control
information may be used. Alternatively, the L1/L2 signaling may be
used.
[0323] When the uplink signal structure includes the uplink user
data, the eNB may notify the UE of the scheduling information in
the subframe. The L1/L2 signaling may be used as the scheduling
information.
[0324] Since the first modification can reduce a gap between the
downlink signal and the uplink signal in the self-contained
subframe and eliminate a gap after transmission of the uplink
signal, the radio resources can be efficiently used. Moreover, the
structure of the uplink signal can be flexibly set in the
self-contained subframe.
Second Modification of First Embodiment
[0325] The second modification will describe a scheduling method to
reduce a gap in the self-contained subframe.
[0326] In the conventional scheduling, the eNB accepts a gap
duration after receiving Ack/Nack to perform retransmission to the
UE in a subframe next to a subframe in which Nack has been received
from the UE (see Non-Patent Document 11).
[0327] However, the gap after receiving Ack/Nack reduces the use
efficiency of the resources. According to the methods disclosed in
the first modification of the first embodiment, the gap after
receiving Ack/Nack can be allocated to the uplink signal. If there
is no uplink signal that can be transmitted from the UE, a problem
with the remaining gap after receiving Ack/Nack occurs.
[0328] The second modification will disclose a method for solving
such a problem. In the second modification, the eNB predetermines
the scheduling for retransmission n subframes ahead. Here, n is an
integer larger than or equal to 1. The synchronous scheduling may
be performed. The eNB may use the scheduling for initial
transmission or the scheduling for retransmission. The eNB may use
both of the scheduling for initial transmission and the scheduling
for retransmission. Which scheduling the eNB uses may be determined
using Ack/Nack to be transmitted from the UE.
[0329] For example, when n=1, the scheduling for retransmission is
performed in advance in a subframe in which the initial
transmission data is transmitted.
[0330] For example, when n=2, the scheduling for retransmission is
performed in a subframe before transmission of the initial
transmission data. Here, the scheduling for the initial
transmission data may be simultaneously performed.
[0331] In the second modification, the scheduling for initial
transmission n subframes ahead may be simultaneously performed. For
example, when n=2, the scheduling for the initial transmission data
two subframes ahead may be performed.
[0332] The adaptive scheduling may be performed in the
retransmission. In other words, scheduling different from that for
the initial transmission may be performed. The non-adaptive
scheduling may be performed.
[0333] In the second modification, the structure of the uplink
signal may be set with application of the first embodiment or the
first modification of the first embodiment. The structure of the
uplink signal may include a gap after receiving Ack/Nack. This
holds true for the following modifications and the following
embodiments.
[0334] The operations of the eNB and the UE when n=1 according to
the second modification will be described.
[0335] The eNB determines the scheduling for initial
transmission.
[0336] In the next subframe, the eNB transmits information on the
scheduling for initial transmission to the UE. The information on
the scheduling for initial transmission may be transmitted using a
downlink control signal. The eNB transmits the initial transmission
data to the UE. The eNB schedules the retransmission data for the
initial transmission data. The eNB may simultaneously schedule the
next initial transmission data.
[0337] The retransmission data may overlap the next initial
transmission data in frequency resources. Here, the eNB may
transmit, in the next subframe, one of the next initial
transmission data and the retransmission data using Ack/Nack from
the UE. The retransmission data may be different from the next
initial transmission data in frequency resources. Here, the eNB may
transmit, in the next subframe, the retransmission data and the
next initial transmission data simultaneously, or only one of
them.
[0338] The UE receives the downlink control signal. The UE obtains
information on the scheduling for initial transmission from the
downlink signal. The UE receives the initial transmission data
according to the information on the scheduling. The UE transmits,
to the eNB, Ack/Nack in response to the initial transmission
data.
[0339] The UE releases received data for HARQ if transmitting Ack
in response to the initial transmission data. The UE holds the
received data for HARQ if not transmitting Ack in response to the
initial transmission data. The received data for HARQ to be held is
combined with the retransmission data received from the eNB to be
decoded. The received data for HARQ is held until Ack is returned
in response to the retransmission or until expiration of the number
of retransmissions.
[0340] The eNB receives Ack/Nack from the UE. The eNB determines
scheduling to be used in the next subframe, based on the Ack/Nack
from the UE. For example, upon receipt of Ack, the eNB uses the
next scheduling for initial transmission in the next subframe. For
example, upon receipt of Nack, the eNB uses the scheduling for
retransmission in the next subframe.
[0341] In the next subframe, the eNB transmits information on the
scheduling determined in a subframe immediately preceding the next
subframe. The eNB transmits, to the UE, the downlink user data
indicated by the information on the scheduling. The eNB also
schedules the downlink user data to be transmitted in the subframe
after the next. The scheduling method is the same as that for the
subframe immediately preceding the subframe after the next.
[0342] The eNB and the UE subsequently repeat the aforementioned
operations.
[0343] FIGS. 11 and 12 illustrate an example method for scheduling
one frame ahead according to the second modification of the first
embodiment. FIGS. 11 and 12 illustrate one example of the
scheduling according to the second modification of the first
embodiment when n=1. FIGS. 11 and 12 are connected across a
location of a border BL1. In FIGS. 11 and 12, the horizontal axis
represents time t, and the vertical axis represents a frequency f.
In FIGS. 11 and 12, scheduling corresponding to each of Ack and
Nack in the current subframe is performed in advance. Then,
scheduling to be applied is switched depending on Ack/Nack from the
UE, and is used in the next subframe.
[0344] FIGS. 13 and 14 illustrate an example method for scheduling
retransmission two frames ahead according to the second
modification of the first embodiment. FIGS. 13 and 14 illustrate
one example of the scheduling according to the second modification
of the first embodiment when n=2. FIGS. 13 and 14 are connected
across a location of a border BL2. In FIGS. 13 and 14, the
horizontal axis represents time t, and the vertical axis represents
a frequency f.
[0345] In FIGS. 13 and 14, the scheduling for initial transmission
to be used in the next subframe and the scheduling for
retransmission to be used in a subframe after the next are
performed in advance. Then, which scheduling is used is switched
depending on Ack/Nack in the subframe and Ack/Nack in the next
subframe. The scheduling for retransmission is performed for the
subframe after the next. Thus, the scheduling for retransmission is
scheduling for the retransmission data for the next initial
transmission, and scheduling for the second retransmission data for
the current initial transmission data.
[0346] FIGS. 15 and 16 illustrate an example method for scheduling
the initial transmission and retransmission two frames ahead
according to the second modification of the first embodiment. FIGS.
15 and 16 illustrate one example of scheduling the initial
transmission n subframes ahead in the scheduling according to the
second modification of the first embodiment. FIGS. 15 and 16
illustrate the case where n=2. FIGS. 15 and 16 are connected across
a location of a border BL3. In FIGS. 15 and 16, the horizontal axis
represents time t, and the vertical axis represents a frequency
f.
[0347] In FIGS. 15 and 16, scheduling to be used in the subframe
after the next is performed for both the initial transmission and
the retransmission. Then, which scheduling is used is switched,
depending on Ack/Nack in the subframe and in the next subframe. The
number of schedulings to be performed in one subframe is the n-th
power of 2. Thus, the number of schedulings to be performed in one
subframe is the second power of 2, that is, 4.
[0348] The following (1) to (5) will be disclosed as specific
examples of information necessary for determining the value n
according to the second modification:
[0349] (1) the uplink signal structure, for example, the Ack/Nack
timing or the gap length after transmission of the uplink
signal;
[0350] (2) the time required for decoding the Ack/Nack by the
eNB;
[0351] (3) the time required for encoding the downlink signal by
the eNB;
[0352] (4) the subframe length; and
[0353] (5) combinations of (1) to (4) above.
[0354] The uplink signal structure in (1) may have the same format
as that according to, for example, the first modification of the
first embodiment. The uplink signal structure may be, for example,
information including at least one of the start timing, the length,
and the end timing of an Ack/Nack symbol.
[0355] The time required for encoding the downlink signal in (3) to
determine the value n according to the second modification may be
the time required for encoding the downlink control information.
The time required for encoding the downlink signal in (3) may be
the time required for encoding the downlink user data.
Alternatively, the time required for encoding the downlink signal
in (3) may be both the time required for encoding the downlink
control information and the time required for encoding the downlink
user data.
[0356] The value n may be fixedly given in a standard according to
the second modification. The eNB may broadcast the value n to the
UE. The broadcast information may be used for the broadcasting. The
broadcast information may be SIB1 or SIB2. The eNB may notify the
UE of the value n via the RRC-dedicated signaling. The value n may
be set only once when the UE is connected to the eNB, or may be
changed after the connection.
[0357] Since the second modification enables the eNB to retransmit
the downlink user data to the UE in a subframe next to a subframe
in which Ack/Nack has been received, the communication latency can
be reduced. Since the gap after transmission of the uplink signal
can be reduced, the efficiency in communication can be
increased.
Third Modification of First Embodiment
[0358] The third modification will describe a scheduling method to
enable retransmission in a subframe next to a subframe in which
Ack/Nack has been received, without any gap after transmission of
the uplink signal in the self-contained subframe.
[0359] Although the method according to the second modification of
the first embodiment enables reduction in the gap after
transmission of the uplink signal, the time required for decoding
Ack and Nack from the UE cannot be completely eliminated. Thus, a
problem of failing to completely eliminate the gap after
transmission of the uplink signal occurs.
[0360] The third modification will disclose a method for solving
such a problem.
[0361] The eNB performs retransmission in m subframes after initial
transmission. Here, m is an integer larger than or equal to 1. The
synchronous scheduling may be performed. The eNB may apply Ack/Nack
from the UE to data to be transmitted in the (m+1)-th subframe
after initial transmission.
[0362] The third modification of the first embodiment is the same
as the TTI bundling (for example, see Reference 1) that is a
conventional technique in that the eNB transmits desired data to
the UE in a plurality of subframes. However, the third modification
differs from the TTI bundling in enabling different scheduling for
the retransmission data from that for the initial transmission.
[0363] For example, when m=1, the eNB performs scheduling after
receiving the Ack/Nack. Upon receipt of Ack, the eNB starts
scheduling for the next initial transmission data. The eNB
transmits the retransmission data to the UE in the next subframe.
Then in the subframe after the next, the eNB transmits the next
initial transmission data to the UE. Upon receipt of Nack, the eNB
starts scheduling for the second retransmission data. The eNB
transmits the retransmission data to the UE in the next subframe.
Then in the subframe after the next, the eNB transmits the second
retransmission data to the UE.
[0364] The eNB predetermines the scheduling for retransmission n
subframes ahead, similarly as the second modification of the first
embodiment. Here, n is an integer larger than or equal to 1. Which
scheduling the eNB uses may be determined using Ack/Nack to be
transmitted from the UE.
[0365] For example, when n=1, the scheduling for retransmission is
performed in advance in a subframe in which the initial
transmission data is transmitted.
[0366] For example, when n=2, the scheduling for retransmission is
performed in a subframe before transmission of the initial
transmission data. Here, the scheduling for the initial
transmission data may be simultaneously performed.
[0367] In the third modification, the scheduling for initial
transmission n subframes ahead may be simultaneously performed. For
example, when n=2, the initial transmission data two subframes
ahead may be scheduled.
[0368] The adaptive scheduling may be performed in the
retransmission. In other words, scheduling different from that for
the initial transmission may be performed. The adaptive scheduling
enables the eNB to perform scheduling that flexibly responds to
change in the radio environment. The non-adaptive scheduling may be
performed. The non-adaptive scheduling eliminates the need for the
UE to perform the decoding process on the downlink control
information upon receipt of retransmission, thus reducing the
processing load in the UE.
[0369] The operations of the eNB and the UE when m=1 and n=1
according to the third modification will be described.
[0370] The eNB determines the scheduling for initial
transmission.
[0371] In the next subframe, the eNB transmits information on the
scheduling for initial transmission to the UE. The information on
the scheduling for initial transmission may be transmitted using a
downlink control signal. The eNB transmits the initial transmission
data to the UE. The eNB also schedules the retransmission data for
the initial transmission data.
[0372] The UE receives the downlink control signal. The UE obtains
information on the scheduling for initial transmission from the
downlink signal. The UE receives the initial transmission data
according to the information on the scheduling. The UE transmits,
to the eNB, Ack/Nack in response to the initial transmission
data.
[0373] The UE releases the received data for HARQ if transmitting
Ack in response to the initial transmission data. The UE holds the
received data for HARQ if not transmitting Ack in response to the
initial transmission data. The received data for HARQ to be held is
combined with the retransmission data received from the eNB to be
decoded. The received data for HARQ is held until Ack is returned
in response to the retransmission or until expiration of the number
of retransmissions.
[0374] The eNB receives Ack/Nack from the UE. The eNB determines
scheduling to be used in the next subframe, based on the Ack/Nack
from the UE. For example, upon receipt of Ack, the eNB uses the
next scheduling for initial transmission in the next subframe. For
example, upon receipt of Nack, the eNB uses the scheduling for the
second retransmission in the next subframe.
[0375] In the next subframe, the eNB transmits, to the UE,
information on the scheduling determined in a subframe immediately
preceding the next subframe. The eNB also transmits, to the UE, the
downlink user data indicated by the information on the scheduling.
The eNB also schedules the downlink user data to be transmitted in
the subframe after the next. The scheduling method is the same as
that for the subframe immediately preceding the subframe after the
next.
[0376] The eNB and the UE subsequently repeat the aforementioned
operations.
[0377] In the third modification, the eNB may not receive Ack/Nack
in response to the retransmission data for which Ack has been
received in the initial transmission. Alternatively, the eNB may
not decode the Ack/Nack.
[0378] In the third modification, the UE may not transmit, to the
eNB, Ack/Nack in response to the retransmission data on or before
the (m-1)-th time. The eNB may not receive Ack/Nack in response to
the retransmission data on or before the (m-1)-th time.
Consequently, the process of coding the Ack/Nack by the UE can be
reduced. Moreover, the process of decoding the Ack/Nack by the eNB
can be reduced.
[0379] In the third modification, the UE may not receive the
retransmission data after transmitting Ack in response to the
initial transmission. Alternatively, the UE may not decode the
retransmission data. Alternatively, the UE may or may not transmit,
to the eNB, the Ack/Nack in response to the retransmission
data.
[0380] Alternatively, the eNB may not retransmit the data for which
Ack has been received from the UE before the m-th retransmission in
the third modification. For example, upon receipt of Ack from the
UE in response to the initial transmission where m=2, the eNB may
transmit the next initial transmission data without transmitting
the second retransmission data to the UE. This can prevent the eNB
from repeatedly transmitting the data that the UE has accurately
received, and increase the efficiency in communication between the
eNB and the UE.
[0381] FIGS. 17 and 18 illustrate an example method for scheduling
one frame ahead when retransmission is performed once according to
the third modification of the first embodiment. FIGS. 17 and 18
illustrate one example of the scheduling where m=1 and n=1
according to the third modification of the first embodiment. FIGS.
17 and 18 are connected across a location of a border BL4. In FIGS.
17 and 18, the horizontal axis represents time t, and the vertical
axis represents a frequency f.
[0382] In FIGS. 17 and 18, the eNB transmits the initial
transmission data to the UE in a subframe next to the subframe in
which the scheduling for initial transmission has been performed.
Since the retransmission is performed once, the eNB schedules
retransmission in the subframe next to the subframe in which the
scheduling for initial transmission has been performed, and
transmits the retransmission data in the subframe after the
next.
[0383] In FIGS. 17 and 18, upon receipt of Ack from the UE in
response to the initial transmission, the eNB schedules the next
initial transmission data in the next subframe, that is, in the
subframe in which the retransmission data is to be transmitted, and
transmits the next initial transmission data in the subframe after
the next. Upon receipt of Nack from the UE in response to the
initial transmission, the eNB schedules the second retransmission
data in the next subframe, and transmits the second retransmission
data in the subframe after the next.
[0384] FIGS. 19 and 20 illustrate an example method for scheduling
retransmission two frames ahead when the retransmission is
performed once according to the third modification of the first
embodiment. FIGS. 19 and 20 illustrate one example of the
scheduling where m=1 and n=2 according to the third modification of
the first embodiment. FIGS. 19 and 20 are connected across a
location of a border BL5. In FIGS. 19 and 20, the horizontal axis
represents time t, and the vertical axis represents a frequency
f.
[0385] In FIGS. 19 and 20, the eNB simultaneously schedules the
initial transmission and the retransmission of DL data #1, and
performs the initial transmission of the DL data #1 and performs
the scheduling for the second retransmission of the DL data #1 in
the next subframe. The eNB retransmits the DL data #1 in the
subframe after the next. Since the eNB also receives Ack from the
UE in response to the initial transmission of the DL data #1, the
eNB schedules the initial transmission and the retransmission of DL
data #2.
[0386] In FIGS. 19 and 20, the eNB performs, in the next subframe,
the initial transmission of the DL data #2 and the scheduling for
the second retransmission of the DL data #2. The eNB retransmits
the DL data #2 in the subframe after the next. Since the eNB
receives Nack from the UE in response to the initial transmission
of the DL data #2, the eNB schedules the third retransmission of
the DL data #2.
[0387] The eNB transmits the DL data #2 for the second
retransmission in the next subframe. Since the eNB receives Ack
from the UE in response to the retransmission of the DL data #2,
the eNB schedules the initial transmission and the retransmission
of DL data #3. The operations for the DL data #3 are the same as
those for the DL data #1.
[0388] FIGS. 21 and 22 illustrate an example method for scheduling
the initial transmission and retransmission two frames ahead when
the retransmission is performed once according to the third
modification of the first embodiment. FIGS. 21 and 22 illustrate
one example of the scheduling for initial transmission n subframes
ahead in the scheduling according to the third modification of the
first embodiment. FIGS. 21 and 22 illustrate the case where m=1 and
n=2. FIGS. 21 and 22 are connected across a location of a border
BL6. In FIGS. 21 and 22, the horizontal axis represents time t, and
the vertical axis represents a frequency f.
[0389] In FIGS. 21 and 22, the eNB performs the scheduling for
initial transmission of the DL data #2 and the scheduling for the
second retransmission of the DL data #1 in a subframe in which the
DL data #1 is to be transmitted. The eNB retransmits the DL data #1
to the UE in the next subframe. Since the eNB receives Ack in
response to the initial transmission of the DL data #1, the eNB
schedules retransmission of the DL data #2.
[0390] Since the eNB receives Ack in response to the initial
transmission of the DL data #1, the eNB performs, in the subframe
after the next, the initial transmission of the DL data #2 based on
the scheduling of the DL data #2 that has been performed two
subframes before. The eNB simultaneously schedules the initial
transmission of the DL data #3 and the second retransmission of the
DL data #2.
[0391] The eNB retransmits the DL data #2 to the UE in the next
subframe. Since the eNB receives Nack in response to the initial
transmission of the DL data #2, the eNB reschedules the initial
transmission of the DL data #3, and performs the scheduling for the
third retransmission of the DL data #2. The eNB performs the third
retransmission of the DL data #2 in the subframe after the next.
Since the eNB receives Ack for the DL data #2, the eNB schedules
retransmission of the DL data #3. The eNB performs the initial
transmission of the DL data #3 in the next subframe. The operations
for the DL data #3 are the same as those for the DL data #1.
[0392] The following (1) to (3) will be disclosed as specific
examples of information necessary for determining the value m
according to the third modification:
[0393] (1) the time for coding the downlink user data by the
eNB;
[0394] (2) a ratio of Ack/Nack transmitted from the UE; and
[0395] (3) a combination of (1) and (2) above.
[0396] The value m may be fixedly given in a standard according to
the third modification. The eNB may broadcast the value m to the
UE. The broadcast information may be used for the broadcasting. The
broadcast information may be SIB1 or SIB2. The eNB may notify the
UE of the value m via the RRC-dedicated signaling. The value m may
be set only once when the UE is connected to the eNB, or may be
changed after the connection.
[0397] Since the information necessary for determining the value n
is the same as that according to the second modification of the
first embodiment, the description will be omitted in the third
modification.
[0398] Since the way to give the value n in the third modification
is the same as that for the value m, the description will be
omitted.
[0399] Since the third modification enables the eNB to retransmit
the downlink user data to the UE in a subframe next to a subframe
in which Ack/Nack has been received, the communication latency can
be reduced. Since the gap after transmission of the uplink signal
can be eliminated, the efficiency in communication can be
increased.
Fourth Modification of First Embodiment
[0400] The fourth modification will describe a scheduling method to
enable retransmission in a subframe next to a subframe in which
Ack/Nack has been received, without using, in the self-contained
subframe, the downlink control information on the subframe in
retransmission.
[0401] Although the eNB transmits the downlink control information
to the UE also in its retransmission in the methods according to
the second and third modifications of the first embodiment, the eNB
performs scheduling without transmitting the downlink control
information to the UE in the retransmission according to the fourth
modification.
[0402] The eNB allocates, to the retransmission, the same frequency
resources and the same modulating method as those for the initial
transmission. In the retransmission, the redundancy version (RV)
may be changed from that for the initial transmission.
Consequently, the error correction capability in the retransmission
can be increased.
[0403] The eNB and the UE may preferably share the association
between the number of retransmissions and the RV. The association
between the number of retransmissions and the RV may be predefined
in a standard. The eNB may broadcast the association between the
number of retransmissions and the RV to the UE. The broadcast
information may be used for the broadcasting. The broadcast
information may be SIB1 or SIB2.
[0404] The eNB may notify the UE of the association between the
number of retransmissions and the RV via the RRC-dedicated
signaling or the MAC signaling. While maintaining the reliability
through the retransmission control, the MAC signaling enables
notification of the association between the number of
retransmissions and the RV more promptly than that by using the
broadcast information and the RRC-dedicated signaling. The RV in
the retransmission may be identical to that in the initial
transmission.
[0405] The eNB may allocate, to the downlink user data in
retransmission, a symbol allocated to the downlink control
information. Consequently, the number of physical channel bits and
the error correction capability in retransmission can be increased.
The eNB may notify the UE of an identifier indicating whether an
area for the downlink control information is allocated to the
downlink user data in retransmission, or whether the area for the
downlink control information is allocated to the downlink user data
may be defined in a standard.
[0406] The eNB may broadcast the identifier to the UE. The
broadcast information may be used for the broadcasting. The
broadcast information may be SIB 1 or SIB2. The eNB may notify the
UE of the identifier via the RRC-dedicated signaling, via the MAC
signaling, or as the downlink control information for the initial
transmission.
[0407] The UE may obtain the identifier. The UE may determine a
receiving area for the downlink user data in retransmission, using
the identifier.
[0408] The fourth modification may be applied to a conventional
method for scheduling the next subframe using Ack/Nack from the UE.
The fourth modification may be applied to the scheduling method
described in the second modification of the first embodiment. The
fourth modification may be applied to the scheduling method
described in the third modification of the first embodiment.
[0409] The operations of the eNB and the UE according to the fourth
modification will be described. The eNB performs scheduling for the
initial transmission data. The eNB transmits the scheduling
information for the initial transmission data. The scheduling
information may be transmitted using a downlink control signal. The
eNB transmits the initial transmission data. The UE receives the
initial transmission data. The UE transmits, to the eNB, Ack/Nack
in response to the initial transmission data.
[0410] The eNB determines whether the retransmission is necessary
for the initial transmission data. The Ack/Nack from the UE may be
used for the determination. Alternatively, the eNB may always
perform retransmissions for the designated number of subframes or
longer after the initial transmission.
[0411] The eNB transmits the retransmission data to the UE based on
the determination. The eNB may use the transmission area for the
downlink control information as the receiving area for the downlink
user data in transmitting the retransmission data.
[0412] The UE determines whether the downlink signal to be received
is for the initial transmission or the retransmission. The
determination may be made using the Ack/Nack transmitted to the
eNB. Alternatively, the arrangement for the eNB to always perform
retransmissions for the designated number of subframes or longer
after the initial transmission may be used.
[0413] The UE receives the retransmission data from the eNB.
Whether the eNB uses the transmission area for the downlink control
information as the area for the downlink user data may be used in
receiving the retransmission data. The UE transmits, to the eNB,
Ack/Nack in response to the retransmission data.
[0414] The UE may transmit a scheduling request to the eNB. The UE
may transmit the scheduling request during the HARQ retransmission
of the downlink user data from the eNB. The eNB may transmit
scheduling information to the UE using the scheduling request from
the UE as a trigger. The eNB may transmit the scheduling
information in response to the retransmission data. Consequently,
the eNB can transmit the downlink control information when
retransmitting the downlink user data. Thus, recover from the
malfunction caused by the eNB misjudging Ack/Nack from the UE is
possible.
[0415] FIGS. 23 and 24 illustrate an example method for scheduling
one frame ahead according to the fourth modification of the first
embodiment. FIGS. 23 and 24 illustrate one example of applying the
fourth modification to the scheduling method described in the
second modification of the first embodiment when n=1. FIGS. 23 and
24 are connected across a location of a border BL7. In FIGS. 23 and
24, the horizontal axis represents time t, and the vertical axis
represents a frequency f.
[0416] Since the UE returns Nack in response to the initial
transmission of the DL data #2 in FIGS. 23 and 24, the DL data #2
is retransmitted to the UE without any downlink control signal in
the next subframe. Furthermore, the initial transmission of the DL
data #3 is rescheduled. In FIGS. 23 and 24, an area for the
downlink control signal in transmitting the retransmission data is
allocated to the area for the downlink user data.
[0417] FIGS. 25 and 26 illustrate an example method for scheduling
one frame ahead when retransmission is performed once according to
the fourth modification of the first embodiment. FIGS. 25 and 26
illustrate one example of applying the fourth modification to the
scheduling method described in the third modification of the first
embodiment when m=1 and n=1. FIGS. 25 and 26 are connected across a
location of a border BL8. In FIGS. 25 and 26, the horizontal axis
represents time t, and the vertical axis represents a frequency
f.
[0418] The transmission area for the downlink user data is
allocated to each retransmission in FIGS. 25 and 26, instead of the
downlink control signal. Since the UE returns Nack to the eNB in
response to the initial transmission of the DL data #2, the second
retransmission of the DL data #2 is performed, and the transmission
area for the downlink user data is allocated to the second
retransmission instead of the downlink control signal, similarly as
in the retransmission.
[0419] Thus, the fourth modification can produce the following
advantages in addition to the advantages of the second or the third
modification of the first embodiment. Specifically, the elimination
of notification of the downlink control information in
retransmission can reduce the amount of signaling from the eNB to
the UE. Furthermore, allocation of a downlink user signal to the
area for the downlink control information in retransmission can
increase the error correction capability for the downlink user data
in retransmission. Consequently, the reliability can be
increased.
Fifth Modification of First Embodiment
[0420] The fifth modification will describe another specific
example of the scheduling method to enable retransmission in a
subframe next to a subframe in which Ack/Nack has been received,
without using, in the self-contained subframe, the downlink control
information on the subframe in retransmission.
[0421] The fourth modification of the first embodiment poses a
problem where radio resources that are the same as those for the
initial transmission data sometimes cannot be used depending on a
subframe, for example, a subframe in which a synchronization signal
and a physical broadcast information channel are transmitted.
[0422] The fifth modification will disclose a method for solving
such a problem.
[0423] In the scheduling for initial transmission, scheduling for
the k retransmissions is performed. Here, k may be an integer
ranging from 1 to the maximum number of retransmissions. k may not
be the value indicating the maximum number of retransmissions. The
retransmission is performed according to a scheduling different
from that for the initial transmission. The retransmission and the
initial transmission may have the same scheduling. The
retransmission may be different in coding rate from the initial
transmission.
[0424] The eNB may notify the UE of information on the scheduling
for the k retransmissions via the L1/L2 signaling. The information
on the scheduling for the k retransmissions may be notified
together with the scheduling for initial transmission.
[0425] The eNB may notify the UE of the downlink control
information in a subframe next to a subframe in which the k
retransmissions are completed. Consequently, when Ack is not
returned even with the k retransmissions, the retransmission can be
continued.
[0426] The value k may be common within a cell according to the
fifth modification. Alternatively, the value k may be set for each
UE. Alternatively, the value k may be set for each process ID.
[0427] The value k may be statically defined in a standard.
Alternatively, the eNB may broadcast the value k to the UE. For
example, the broadcast information may be used in the broadcasting.
The broadcast information may be, for example, SIB 1 or SIB2. The
notification may be made from the eNB to the UE via the
RRC-dedicated signaling, the MAC signaling, or the L1/L2
signaling.
[0428] The following (1) to (4) will be disclosed as specific
examples of information necessary for the eNB to determine the
value k:
[0429] (1) the maximum number of retransmissions;
[0430] (2) a ratio of Ack/Nack received from the UE, for example, a
block error rate (=Nack/(Ack+Nack));
[0431] (3) statistical information on the number of actual
retransmissions; and
[0432] (4) combinations of (1) to (3) above.
[0433] For example, the maximum number of actual retransmissions
may be used as the statistical information in (3). Alternatively,
an upper limit to the number of retransmissions performed more than
or equal to a designated number of times may be used. The
statistical information in (3) may be sourced from information
since start of the eNB or for a predefined period of time in the
past.
[0434] The fifth modification may be applied to the conventional
method for scheduling the next subframe using Ack/Nack from the UE.
The fifth modification may be applied to the scheduling method
described in the second modification of the first embodiment. The
fifth modification may be applied to the scheduling method
described in the third modification of the first embodiment.
[0435] The operations of the eNB and the UE according to the fifth
modification will be described. The eNB performs scheduling for the
initial transmission data. The eNB also performs the scheduling for
the k retransmissions. The scheduling information may be different
between the initial transmission and the retransmissions. Examples
of the scheduling information may include frequency resources, a
coding rate, and a modulating method.
[0436] The eNB transmits, to the UE, the scheduling information for
the initial transmission data and the scheduling information for
the k retransmissions. The eNB may use the area for the downlink
control information in transmitting the scheduling information for
the initial transmission data and the scheduling information for
the k retransmissions. The eNB transmits, to the UE, the initial
transmission data together with the scheduling information for the
initial transmission data and the scheduling information for the k
retransmissions.
[0437] The eNB determines whether the retransmission is necessary
for the initial transmission data. The Ack/Nack from the UE may be
used for the determination. Alternatively, the eNB may always
perform retransmissions for the designated number of subframes or
longer after the initial transmission.
[0438] The eNB transmits the retransmission data to the UE based on
the determination. The eNB may use the transmission area for the
downlink control information as the receiving area for the downlink
user data in the retransmission. The eNB may schedule the next
initial transmission and the k retransmissions before receiving Ack
from the UE. The eNB may reschedule the next initial transmission
and the k retransmissions that have already been scheduled.
[0439] The UE receives the scheduling information for the initial
transmission and for the k retransmissions.
[0440] The UE determines whether the downlink signal to be received
is for the initial transmission or the retransmission. The
determination may be made using the Ack/Nack transmitted to the
eNB. Alternatively, the arrangement for the eNB to always perform
retransmissions for the designated number of subframes or longer
after the initial transmission may be used.
[0441] The UE receives the retransmission data from the eNB.
Whether the eNB uses the transmission area for the downlink control
information as the area for the downlink user data may be used in
receiving the retransmission data. The UE transmits, to the eNB,
Ack/Nack in response to the retransmission data. The UE may discard
or hold the scheduling information for the k retransmissions.
[0442] The UE may transmit a scheduling request to the eNB,
similarly as the fourth modification of the first embodiment. The
UE may transmit the scheduling request during the HARQ
retransmission of the downlink user data from the eNB. The eNB may
transmit scheduling information to the UE, using the scheduling
request from the UE as a trigger. The eNB may transmit the
scheduling information in response to the retransmission data.
Consequently, the eNB can transmit the downlink control information
when retransmitting the downlink user data. Thus, recover from the
malfunction caused by the eNB misjudging Ack/Nack from the UE is
possible.
[0443] FIGS. 27 and 28 illustrate an example method for scheduling
one frame ahead according to the fifth modification of the first
embodiment. FIGS. 27 and 28 illustrate one example of applying the
fifth modification to the scheduling method described in the second
modification of the first embodiment when n=1. FIGS. 27 and 28 are
connected across a location of a border BL9. In FIGS. 27 and 28,
the horizontal axis represents time t, and the vertical axis
represents a frequency f.
[0444] In FIGS. 27 and 28, the eNB schedules the initial
transmission and the k retransmissions of the DL data #2 during
initial transmission of the DL data #1. In the next subframe, the
eNB transmits the scheduling information for the initial
transmission and the k retransmissions of the DL data #2, and the
initial transmission data of the DL data #2.
[0445] Similarly, the eNB schedules the initial transmission and
the k retransmissions of the DL data #3 during the initial
transmission of the DL data #2. In the next subframe, the eNB
transmits the scheduling information for the initial transmission
and the k retransmissions of the DL data #3, and the initial
transmission data of the DL data #3.
[0446] Since the UE returns Nack in response to the initial
transmission of the DL data #2 in FIGS. 27 and 28, the eNB
retransmits the DL data #2 and reschedules the initial transmission
and the k retransmissions of the DL data #3. Since the UE returns
Ack in response to the retransmission of the DL data #2, the eNB
transmits, in the next subframe, the scheduling information for the
initial transmission and the k retransmissions of the DL data #3,
and the initial transmission data of the DL data #3.
[0447] FIGS. 29 and 30 illustrate an example method for scheduling
one frame ahead when retransmission is performed once according to
the fifth modification of the first embodiment. FIGS. 29 and 30
illustrate one example of applying the fifth modification to the
scheduling method described in the third modification of the first
embodiment when m=1 and n=1. FIGS. 29 and 30 are connected across a
location of a border BL10. In FIGS. 29 and 30, the horizontal axis
represents time t, and the vertical axis represents a frequency
f.
[0448] After transmitting the DL data, the eNB schedules the next
initial transmission data and the k retransmissions in a subframe
next to a subframe in which the first Ack has been received. Since
Ack is returned in response to the initial transmission of the DL
data #1, the eNB schedules the initial transmission and the k
retransmissions of the DL data #2 in retransmitting the DL data #1.
However, Nack is returned in response to the initial transmission
of the DL data #2, and Ack is returned in response to the first
retransmission of the DL data #2. Thus, the eNB schedules the
initial transmission and the k retransmissions of the DL data #3
during the second retransmission of the DL data #2.
[0449] The fifth modification can produce the same advantages as
those according to the fourth modification of the first embodiment
even when the available frequency resources are different between
the initial transmission and the retransmissions.
Sixth Modification of First Embodiment
[0450] The sixth modification will describe a scheduling method to
enable retransmission in a subframe next to a subframe in which
Ack/Nack has been received, when asynchronous scheduling is
performed in the self-contained subframe.
[0451] Since the synchronous scheduling is performed in the methods
according to the second to fifth modifications of the first
embodiment, the retransmission data is always transmitted in a
subframe next to that for the initial transmission. However, when
the frequency resources in the subframe next to that for the
initial transmission are smaller than those for the initial
transmission or when the radio environment in the next subframe is
worse than that in the initial transmission, transmission of the
retransmission data in the subframe next to that for the initial
transmission causes problems of the low probability of Ack and the
inefficiency.
[0452] The sixth modification will disclose a method for solving
such a problem.
[0453] The eNB and the UE use the asynchronous scheduling. The eNB
schedules the initial transmission data or the retransmission data
to be transmitted in the next subframe, before receiving Ack/Nack
from the UE.
[0454] The eNB determines whether to perform retransmission in the
next subframe. The eNB transmits the downlink control information
to the UE for each retransmission. The UE receives the downlink
control information from the eNB in each subframe. The UE receives
the initial transmission data or the retransmission data according
to an instruction of the downlink control information.
[0455] In the sixth modification, the downlink control information
may include a HARQ process number. Alternatively, the downlink
control information may include an identifier indicating
retransmission.
[0456] The following (1) to (5) will be disclosed as specific
examples of information necessary for the eNB to determine whether
retransmission is possible according to the sixth modification:
[0457] (1) the number of available REs;
[0458] (2) a channel state;
[0459] (3) a coding rate of the retransmission data;
[0460] (4) the number of retransmissions; and
[0461] (5) combinations of (1) to (4) above.
[0462] The presence or absence of a common signaling channel may be
used in (1). The presence or absence of a common signaling channel
may be, for example, the presence or absence of a synchronization
channel. Alternatively, the presence or absence of a common
signaling channel may be the presence or absence of a physical
broadcast channel.
[0463] The channel state in (2) may be a CQI to be transmitted by
the UE. The CQI may be a periodic CQI or an aperiodic CQI. The eNB
may find the channel state using an uplink reference signal to be
transmitted by the UE. Examples of the uplink reference signal to
be used may include an uplink demodulation reference signal, an
uplink sounding reference signal, and another uplink reference
signal.
[0464] The coding rate of the retransmission data in (3) may have a
threshold, and whether the retransmission is possible may be
determined when the coding rate is higher than or equal to the
threshold or when the coding rate is lower than or equal to the
threshold. Regarding the determination on whether the
retransmission is possible using the threshold of the coding rate,
it may be determined that the retransmission is possible, for
example, when the coding rate is lower than or equal to 1, that is,
when the number of bits to be coded is less than or equal to the
number of coded bits, or based on the other criteria.
[0465] The following (1) to (4) will be disclosed as specific
examples of the criteria to be used for the scheduling by the eNB
according to the sixth modification:
[0466] (1) whether there are sufficient frequency resources for
performing retransmission in a subframe in which scheduling will be
performed;
[0467] (2) whether the eNB has data to be coded for initial
transmission;
[0468] (3) whether Ack has been received from the UE; and
[0469] (4) combinations of (1) to (3) above.
[0470] In (4), the scheduling may be performed, for example, in the
order of (1), (2), and (3). Alternatively, the scheduling may be
performed, for example, in the order of (3), (1), and (2).
[0471] The eNB may determine whether the retransmission is possible
simultaneously when the eNB schedules the retransmission data
according to the sixth modification. For example, whether the first
retransmission is possible may be determined when the eNB transmits
the initial transmission data. Whether the second retransmission is
possible may be determined when the eNB transmits the first
retransmission data.
[0472] Among a plurality of DL data requiring scheduling for
retransmission, scheduling for a part of the DL data as well as
scheduling of retransmission of DL data whose initial transmission
has been performed earlier may be performed according to the sixth
modification. Alternatively, scheduling for a part of the DL data
including retransmission of DL data whose initial transmission or
retransmission has been performed the most recently may be
performed. Alternatively, a plurality of DL data requiring
retransmission may be scheduled. Then, which DL data is to be
transmitted may be selected when the downlink user data is
transmitted.
[0473] The sixth modification may be applied to the scheduling for
predetermining retransmission scheduling n subframes ahead,
similarly as the second modification of the first embodiment.
[0474] The sixth modification may be applied to the scheduling for
retransmission in m subframes after the initial transmission,
similarly as the third modification of the first embodiment. The
eNB may perform, among a plurality of DL data requiring scheduling
for retransmission, scheduling for a part of the DL data as well as
scheduling of retransmission of DL data whose initial transmission
has been performed earlier. Alternatively, the eNB may schedule a
part of the DL data including retransmission of DL data whose
initial transmission or retransmission has been performed the most
recently. Alternatively, the eNB may schedule a plurality of DL
data requiring retransmission, and select which DL data is to be
transmitted when transmitting the downlink user data.
[0475] FIGS. 31 and 32 illustrate an example method for scheduling
one frame ahead according to the sixth modification of the first
embodiment. FIGS. 31 and 32 illustrate one example of the
scheduling for predetermining retransmission scheduling in the next
subframe (n=1) according to the sixth modification. FIGS. 31 and 32
are connected across a location of a border BL11. In FIGS. 31 and
32, the horizontal axis represents time t, and the vertical axis
represents a frequency f.
[0476] The eNB performs the initial transmission of the DL data #1
in a subframe #1. Since the next subframe #2 has frequency
resources for retransmitting the DL data #1, the eNB schedules
retransmission of the DL data #1 as well as the initial
transmission of the DL data #2.
[0477] Since the UE returns Ack in the subframe #1 illustrated in
FIGS. 31 and 32, the eNB performs the initial transmission of the
DL data #2 in the subframe #2. However, the next subframe #3 does
not have frequency resources necessary for retransmitting the DL
data #2. Thus, the eNB only schedules the initial transmission of
the DL data #3 without scheduling the retransmission of the DL data
#2.
[0478] Although the UE returns Nack in the subframe #2 illustrated
in FIGS. 31 and 32, only the scheduling for the DL data #3 for
initial transmission is completed in the subframe #2. Thus, the eNB
performs the initial transmission of the DL data #3 in the subframe
#3.
[0479] The candidates for the scheduling for the next subframe #4
are the DL data #2 for retransmission, the DL data #3 for
retransmission, and the DL data #4 for initial transmission. The
next subframe #4 has sufficient frequency resources for performing
retransmission of the DL data #2 and the DL data #3.
[0480] The eNB schedules the retransmission of the DL data #2, the
retransmission of the DL data #3, and the initial transmission of
the DL data #4. The eNB may perform any one or two of the three
schedulings above.
[0481] Since the UE returns Ack in the subframe #3 illustrated in
FIGS. 31 and 32, the scheduling for retransmission of the DL data
#3 is not necessary at the end of the subframe #3. The eNB selects,
from among the DL data #2 for retransmission and the DL data #4 for
initial transmission, the DL data #2 for retransmission whose data
number is smaller, and transmits the DL data #2 in the subframe #4.
The eNB may select and transmit the DL data #4 for initial
transmission.
[0482] FIGS. 33 and 34 illustrate an example method for scheduling
one frame ahead when retransmission is performed once according to
the sixth modification of the first embodiment. FIGS. 33 and 34
illustrate one example of scheduling for performing retransmission
for one subframe after the initial transmission (m=1, n=1)
according to the sixth modification. FIGS. 33 and 34 are connected
across a location of a border BL12. In FIGS. 33 and 34, the
horizontal axis represents time t, and the vertical axis represents
a frequency f.
[0483] The eNB performs the initial transmission of the DL data #1
in the subframe #1. Since the next subframe #2 has frequency
resources for retransmitting the DL data #1, the eNB schedules
retransmission of the DL data #1.
[0484] The eNB retransmits the DL data #1 in the subframe #2
illustrated in FIGS. 33 and 34. Since the UE returns Ack in the
subframe #1, the eNB schedules the initial transmission of the DL
data #2 in the subframe #2.
[0485] The eNB performs the initial transmission of the DL data #2
in the subframe #3 illustrated in FIGS. 33 and 34. However, the
next subframe #4 does not have frequency resources necessary for
retransmitting the DL data #2. Thus, the eNB schedules the initial
transmission of the DL data #3 without scheduling the
retransmission of the DL data #2.
[0486] The eNB performs the initial transmission of the DL data #3
in the subframe #4 illustrated in FIGS. 33 and 34. Since the
subframe #5 has frequency resources for retransmitting the DL data
#3, the eNB schedules retransmission of the DL data #3.
[0487] Since the UE returns Nack in the subframe #3, the eNB may
schedule the retransmission of the DL data #2 in the subframe #4
illustrated in FIGS. 33 and 34.
[0488] The eNB retransmits the DL data #3 in the subframe #5
illustrated in FIGS. 33 and 34. Since the subframe #6 has frequency
resources for retransmitting the DL data #2, the eNB schedules
retransmission of the DL data #2.
[0489] Thus, the sixth modification can produce the following
advantage in addition to the advantages of the second or the third
modification of the first embodiment. Specifically, the user data
can be efficiently communicated upon change in the radio
environment.
Seventh Modification of First Embodiment
[0490] The seventh modification will describe a scheduling method
to abort the HARQ retransmission in the self-contained
subframe.
[0491] Under a continued situation with the methods according to
the second to the fifth modifications of the first embodiment where
frequency resources and a modulating method vary for the reason of,
for example, worsening of the radio environment during
retransmission, the UE fails in accurate reception even with many
retransmissions, and the eNB continues the retransmission until the
expiration of the maximum number of retransmissions. This will
waste the communication.
[0492] If the situation is continued in the method according to the
sixth modification of the first embodiment, no transmission of the
retransmission data to the UE for a long time will cause a problem
of missing user data.
[0493] The seventh modification will disclose a method for solving
such a problem.
[0494] The eNB determines whether to abort the retransmission of
the downlink user data. The eNB aborts the retransmission of the
downlink user data based on the determination.
[0495] The initial transmission data after aborting the
retransmission of the downlink user data may or may not include
elements included in the data whose retransmission has been
aborted. Examples of the elements may include a protocol data unit
(PDU) in an upper layer of HARQ, and MAC signaling information. The
upper layer may be, for example, an RLC layer.
[0496] The retransmission may be aborted for each UE or for each
HARQ process according to the seventh modification.
[0497] The following (1) to (7) will be disclosed as information
necessary for determining whether to abort the retransmission
according to the seventh modification:
[0498] (1) the number of available REs;
[0499] (2) a channel state;
[0500] (3) a period with which information indicating a channel
state is updated;
[0501] (4) a coding rate of retransmission data;
[0502] (5) the number of retransmissions;
[0503] (6) the maximum number of retransmissions; and
[0504] (7) combinations of (1) to (6) above.
[0505] The presence or absence of a common signaling channel may be
used in (1). The presence or absence of a common signaling channel
may be, for example, the presence or absence of a synchronization
channel. Alternatively, the presence or absence of a common
signaling channel may be the presence or absence of a physical
broadcast channel.
[0506] The channel state in (2) may be a CQI to be transmitted by
the UE. The CQI may be a periodic CQI or an aperiodic CQI. The eNB
may find the channel state using an uplink reference signal to be
transmitted by the UE. Examples of the uplink reference signal to
be used may include an uplink demodulation reference signal, an
uplink sounding reference signal, and another uplink reference
signal.
[0507] The period in (3) may be, for example, a transmission period
of the CQI. Alternatively, the period may be a transmission period
of the uplink reference signal. The transmission period of the
uplink reference signal may be, for example, a transmission period
of the uplink demodulation reference signal, a transmission period
of a sounding reference signal, and a transmission period of the
other uplink reference signal.
[0508] The coding rate of the retransmission data in (4) may have a
threshold, and whether the retransmission is possible may be
determined when the coding rate is higher than or equal to the
threshold or when the coding rate is lower than or equal to the
threshold. Regarding the determination on whether the
retransmission is possible using the threshold of the coding rate,
it may be determined that the retransmission is aborted, for
example, when the coding rate is lower than or equal to 1, that is,
when a predefined number of subframes whose number of bits to be
coded is less than or equal to the number of coded bits are
continued, or based on the other criteria.
[0509] In (1) to (6) above, not only information on the subframe in
which scheduling will be performed but also information up to a
plurality of subframes ahead may be used.
[0510] In the seventh modification, it may be determined that the
retransmission is aborted, for example, when the retransmission is
scheduled. An alternative time may be the time upon receipt of the
information indicating the channel state in (2).
[0511] In the seventh modification, whether the initial
transmission data after aborting the retransmission includes the
constituent elements of the data whose retransmission has been
aborted may be determined using the presence or absence of the
retransmission control in the upper layer of HARQ, for example, in
the RLC layer. Alternatively, the presence or absence of reordering
in the upper layer of HARQ may be used. Alternatively, both of the
presence or absence of the retransmission control and the presence
or absence of the reordering may be used in combination.
[0512] For example, a mode of RLC may be used as information for
identifying the presence or absence of the retransmission control
and the presence or absence of the reordering. For example, an
acknowledge mode (AM) of the RLC indicates the presence of the
retransmission control and the presence of the reordering. For
example, an unacknowledged mode (UM) of the RLC indicates the
absence of the retransmission control and the presence of the
reordering. For example, a transparent mode (TM) of the RLC
indicates the absence of the retransmission control and the absence
of the reordering.
[0513] In the seventh modification, the eNB may notify the UE to
abort the HARQ retransmission. The notification of aborting the
HARQ retransmission may be made using the downlink control signal.
The downlink control signal may include an identifier indicating
new data. The identifier may be, for example, a new data indicator
(NDI). The downlink control signal may also include a HARQ process
ID. The downlink control signal may include both the identifier and
the process ID. For example, the eNB may include, in the downlink
control signal for the initial transmission after aborting the
retransmission, a process ID in which the retransmission has been
aborted and the NDI indicating the initial transmission.
Alternatively, the eNB may notify the UE to abort the HARQ
retransmission via the MAC signaling.
[0514] In the seventh modification, the UE may determine whether
the eNB has aborted the retransmission, based on the downlink
control signal from the eNB. For example, when the downlink control
signal received from the eNB includes a HARQ process ID indicating
a wait for the retransmission and the NID indicating the initial
transmission, the UE may determine that the eNB has aborted the
retransmission in the process ID.
[0515] In the seventh modification, a MAC layer of the eNB may
notify the upper layer to abort the HARQ retransmission. The upper
layer may be, for example, an RLC layer.
[0516] In the seventh modification, a MAC layer of the UE may
notify the upper layer to abort the HARQ retransmission. The upper
layer may be, for example, an RLC layer. The MAC layer of the UE
may discard the HARQ-received data subject to aborting of the HARQ
retransmission.
[0517] The seventh modification may be applied to the scheduling
for predetermining retransmission scheduling n subframes ahead,
similarly as the second modification of the first embodiment.
[0518] The seventh modification may be applied to the scheduling
for retransmission in m subframes after the initial transmission,
similarly as the third modification of the first embodiment. The
eNB may perform, among a plurality of DL data requiring scheduling
for retransmission, scheduling for a part of the DL data as well as
scheduling of retransmission of DL data whose initial transmission
has been performed earlier. Alternatively, the eNB may schedule a
part of the DL data including retransmission of DL data whose
initial transmission or retransmission has been performed the most
recently. Alternatively, the eNB may schedule a plurality of DL
data requiring retransmission, and select which DL data is to be
transmitted when transmitting the downlink user data.
[0519] FIGS. 35 and 36 illustrate an example method for scheduling
one frame ahead according to the seventh modification of the first
embodiment. FIGS. 35 and 36 illustrate one example of scheduling
for predetermining retransmission scheduling in the next subframe
(n=1) according to the seventh modification. FIGS. 35 and 36 are
connected across a location of a border BL13. In FIGS. 35 and 36,
the horizontal axis represents time t, and the vertical axis
represents a frequency f.
[0520] In the scheduling illustrated in FIGS. 35 and 36, the MAC
layer receives RLC PDUs from the upper RLC layer, and generates
data to be transmitted to the UE. Assume the frequency resources
necessary for transmitting the DL data in or before the subframe #2
are insufficient in or after the subframe #3.
[0521] In the subframe #1 illustrated in FIGS. 35 and 36, the eNB
transmits, to the UE, the DL data #1 generated from the RLC PDUs 1
to 3 as the initial transmission. The eNB schedules retransmission
of the DL data #1 as well as the initial transmission of the DL
data #2. The DL data #2 is data generated from the RLC PDUs 4 to
6.
[0522] Since the UE returns Ack in the subframe #1 illustrated in
FIGS. 35 and 36, the eNB performs the initial transmission of the
DL data #2 in the subframe #2. However, the next subframe #3 or the
subsequent subframes do not have resources for transmitting the DL
data #2. Thus, the eNB aborts retransmission of the DL data #2. The
eNB schedules the initial transmission of the DL data #4 in
preparation for Ack from the UE. The eNB schedules the initial
transmission of the DL data #3 in preparation for Nack from the UE.
The DL data #4 is data generated from the RLC PDUs 7 and 8 that are
not included in the DL data #2. The DL data #3 is data generated
from the RLC PDUs 4 and 5 that are included in the DL data #2. The
eNB may not schedule the initial transmission of the DL data #3 in
the scheduling in the subframe #2.
[0523] Since the UE returns Nack in the subframe #2 illustrated in
FIGS. 35 and 36, the eNB performs the initial transmission of the
DL data #3 in the subframe #3. The eNB schedules the initial
transmission of the DL data #5 and retransmission of the DL data
#3.
[0524] Since the UE returns Ack in the subframe #3 illustrated in
FIGS. 35 and 36, the eNB performs the initial transmission of the
DL data #5 in the subframe #4. The eNB schedules the initial
transmission of the DL data #6 and retransmission of the DL data
#5.
[0525] FIGS. 37 and 38 illustrate an example method for scheduling
one frame ahead when retransmission is performed once according to
the seventh modification of the first embodiment. FIGS. 37 and 38
illustrate one example of scheduling for performing retransmission
for one subframe after the initial transmission (m=1, n=1)
according to the seventh modification. FIGS. 37 and 38 are
connected across a location of a border BL14. In FIGS. 37 and 38,
the horizontal axis represents time t, and the vertical axis
represents a frequency f.
[0526] In the scheduling illustrated in FIGS. 37 and 38, the MAC
layer receives RLC PDUs from the upper RLC layer, and generates
data to be transmitted to the UE. Assume the frequency resources
necessary for transmitting the DL data in or before the subframe #3
are insufficient in or after the subframe #4.
[0527] In the subframe #1 illustrated in FIGS. 37 and 38, the eNB
transmits, to the UE, the DL data #1 generated from the RLC PDUs 1
to 3 as the initial transmission. The eNB schedules retransmission
of the DL data #1.
[0528] The eNB retransmits the DL data #1 in the subframe #2
illustrated in FIGS. 37 and 38. Since the UE returns Ack in the
subframe #1, the eNB schedules the initial transmission of the DL
data #2. The DL data #2 is data generated from the RLC PDUs 4 to
6.
[0529] The eNB performs the initial transmission of the DL data #2
in the subframe #3 illustrated in FIGS. 37 and 38. However, the
next subframe #4 or the subsequent subframes do not have resources
for transmitting the DL data #2. Thus, the eNB aborts
retransmission of the DL data #2. The eNB schedules the initial
transmission of DL data #2a. The DL data #2a is data generated from
the RLC PDUs 4 and 5 that are included in the DL data #2. The eNB
may schedule transmission of data including the RLC PDU 7 and the
subsequent RLC PDUs that are not included in the DL data #2,
instead of the DL data #2a.
[0530] The eNB performs the initial transmission of the DL data #2a
in the subframe #4 illustrated in FIGS. 37 and 38. Since the UE
returns Ack in response to the DL data #2, the eNB schedules the
initial transmission of the DL data #3. The eNB may schedule
retransmission of the DL data #2a, regardless of the presence or
absence of reception of Ack in response to the DL data #2 from the
UE.
[0531] Since the operations in and after the subframe #5
illustrated in FIGS. 37 and 38 are the same as those in FIGS. 17
and 18, the description thereof will be omitted.
[0532] The scheduling method described in the seventh modification
may be applied to the uplink scheduling. The entity that determines
to abort retransmission of the uplink user data may be the eNB or
the UE. The eNB may notify the UE to abort the retransmission of
the uplink user data. The eNB may notify the UE to abort the
retransmission via the L1/L2 signaling or the MAC signaling. The UE
may notify the eNB to abort the retransmission of the uplink user
data. The UE may notify the eNB to abort the retransmission via the
L1/L2 signaling or the MAC signaling.
[0533] Thus, the seventh modification can produce the following
advantages in addition to the advantages of the second or the third
modification of the first embodiment. Specifically, repetition of
the retransmission under the worse radio environment can be
prevented, and the user data can be efficiently communicated.
Eighth Modification of First Embodiment
[0534] The eighth modification will describe another method for
reducing or eliminating the gap length after transmission of the
uplink signal in the self-contained subframe.
[0535] Reducing or eliminating the gap length after transmission of
the uplink signal in the self-contained subframe causes a problem
of delay in the transmission of information on scheduling of the
subframe with respect to the timing of transmitting the downlink
control information in the next subframe.
[0536] The eighth modification will disclose a method for solving
such a problem.
[0537] The eNB allocates the scheduling information in a user data
area.
[0538] The eNB may apply the structure of the enhanced physical
downlink control channel (EPDCCH) for the allocation in the user
data area. The eNB may decode Ack/Nack from the UE along with the
timing of transmitting the downlink control information. The eNB
may schedule the next subframe. The eNB may code the user data to
be transmitted in the next subframe.
[0539] The UE may receive an area for EPDCCH for each subframe.
[0540] The eNB may notify the UE of information on the structure of
the EPDCCH. The information may be notified via the RRC-dedicated
signaling, the MAC signaling, or the L1/L2 signaling. The L1/L2
signaling may be transmitted using the PDCCH.
[0541] The eNB and the UE may apply the scheduling method described
in the eighth modification to both the synchronous and the
asynchronous schedulings. The scheduling method may also be applied
to both the adaptive and the non-adaptive schedulings.
[0542] Since the gap after transmission of the uplink signal can be
reduced or eliminated, the efficiency in communication between the
eNB and the UE can be increased.
Second Embodiment
[0543] Studies have been made to adopt, in the Time Division Duplex
(TDD) using reciprocity of channels, the sounding reference signal
(SRS) to be transmitted in the uplink for deriving a precoding
weight for downlink MIMO. Although the LTE supports the periodic
sounding reference signal (SRS), change in the transmission period
of the periodic SRS requires change in the settings via the
RRC-dedicated signaling (see 3GPP TS 36.331 V13.2.0 (hereinafter
referred to as "Reference 3")).
[0544] However, when the moving speed of the UE greatly fluctuates
with a short period of time, the required transmission period of
the SRS varies depending on the fluctuations in the Doppler
frequency. Here, the application of the RRC-dedicated signaling in
changing the transmission period of the SRS makes it difficult to
respond in a short time and degrades the precoding performance.
Even when sudden change in the radio propagation environment and in
the traffic occurs, the application of the RRC-dedicated signaling
in changing the transmission period of the SRS also makes it
difficult to respond in a short time and degrades the precoding
performance.
[0545] According to the conventional method for changing the
transmission period of the SRS, the periodic settings of the SRS
cannot be changed in a short time, and the SRS cannot be
transmitted when necessary. Thus, a problem of degradation in the
precoding performance for the downlink MIMO occurs.
[0546] The second embodiment will disclose a method for solving
such a problem.
[0547] A period with which the UE actually transmits the periodic
SRS (hereinafter may be referred to as a "SRS transmission period")
is set as L1/L2 control information. Examples of the SRS
transmission period include information indicating a value of the
SRS transmission period. The cell notifies the UE of the SRS
transmission period via the L1/L2 control signaling. The cell may
notify the SRS transmission period as the downlink control
information (DCI) to be transmitted via the downlink L1/L2 control
signaling. The cell may map the SRS transmission period to a
downlink physical control channel and notify the downlink physical
control channel.
[0548] The notification of the SRS transmission period from the
cell to the UE may make the UE start transmitting the periodic SRS.
Upon receipt of the SRS transmission period from the cell, the UE
may start transmitting the periodic SRS. The UE starts transmitting
the periodic SRS after changing the period, along with the timing
of a subframe which is the earliest since receipt of the SRS
transmission period from the cell and in which the SRS can be
transmitted.
[0549] Information for making the UE stop the SRS transmission may
be provided. The information may be provided separately from the
SRS transmission period, or as one value of the SRS transmission
period. For example, 0 may be provided as a value of the SRS
transmission period, and the SRS transmission may be stopped when 0
is set. The UE stops transmitting the SRS when the value of the SRS
transmission period is 0.
[0550] The subframe in which the SRS is to be actually transmitted
is set as a part or the entirety of the subframe in which the SRS
can be transmitted. The cell may preset, individually to each UE, a
subframe structure in which the SRS can be transmitted. The cell
sets, individually to each UE, for example, a period (hereinafter
may be referred to as a "SRS transmission possible period"), a
bandwidth, a sub-carrier interval (a comb value), a cyclic shift
(CS), etc. of the subframe in which the SRS can be transmitted. The
subframe structure in which the SRS can be transmitted is
transmitted via the RRC signaling. In consideration of multiplexing
of the SRSs among a plurality of UEs, the cell may set the subframe
structure in which each of the UEs can transmit the SRS.
[0551] The subframe in which the SRS is to be actually transmitted
is set as a part or the entirety of the subframe in which the SRS
can be transmitted, so that a subframe structure except for the SRS
transmission period of the subframe in which the SRS is to be
actually transmitted is set identical to the subframe structure in
which the SRS can be transmitted.
[0552] Consequently, setting the subframe in which the SRS is to be
actually transmitted as a part or the entirety of a subframe in
which the SRS can be transmitted for each UE in consideration of
multiplexing of the SRSs among the plurality of UEs allows the
multiplexing with the SRS of another UE without any problem even
when the SRS transmission period is changed.
[0553] FIG. 39 illustrates a method for setting the SRS
transmission period according to the second embodiment. In FIG. 39,
the horizontal axis represents time t. An allowable subframe is a
subframe in which the SRS can be transmitted and which is set for
each cell. A configured subframe is a subframe in which the SRS can
be transmitted for each UE and which is set for each UE. The
configured subframe is set in the subframe in which the SRS can be
transmitted and which is set for each cell. A transmission subframe
is a subframe in which the SRS is to be actually transmitted. The
subframe in which the SRS is to be actually transmitted is set as a
part or the entirety of the subframe in which the SRS can be
transmitted for each UE.
[0554] In FIG. 39, the allowable subframe is represented by a
non-hatched box. The configured subframe is represented by
diagonal-hatched solid lines that descend to the left. The
transmission subframe is represented by diagonal-hatched solid
lines that descend to the right. The notification of the SRS
transmission period from the cell to the UE is represented by
diagonal-hatched broken lines that descend to the right.
[0555] The cell broadcasts, to the UE, a subframe structure in
which the SRS can be transmitted for each cell. Here, the subframe
structure is broadcast using system information (SI). The subframe
structure in which the SRS can be transmitted for each cell
includes a subframe period with which the SRS can be transmitted
for each cell. The cell notifies the UE of a subframe structure in
which the SRS can be transmitted for each UE via the UE-dedicated
signaling. The structure is notified via the RRC-dedicated
signaling herein. The subframe structure in which the SRS can be
transmitted for each UE includes a subframe period with which the
SRS can be transmitted for each UE.
[0556] The SRS transmission period that is a period of the SRS to
be actually transmitted by the UE is provided as one piece of DCI.
The cell sets the SRS transmission period, includes the SRS
transmission period in the DCI, maps the DCI to a physical
dedicated control channel, and notifies the UE of the physical
dedicated control channel. Here, the physical dedicated control
channel is the PDCCH in the LTE. The UE starts transmitting the SRS
with the SRS transmission period, from the subframe in which the
SRS can be transmitted for each UE with the earliest timing since
receipt of the SRS transmission period. The cell receives the SRS
transmitted from the UE with the SRS transmission period, from the
subframe in which the SRS can be transmitted for each UE with the
earliest timing since notification of the SRS transmission period
to the UE.
[0557] In FIG. 39, the eNB notifies the UE of the subframe
structure in which the SRS can be transmitted for each UE. As an
alternative method, the eNB may not notify the UE of the subframe
structure in which the SRS can be transmitted for each UE. The eNB
may notify the UE of the subframe structure in which the SRS can be
transmitted for each cell. The eNB may notify the UE of the
subframe structure in which the SRS is to be actually
transmitted.
[0558] The subframe structure in which the SRS is to be actually
transmitted may be notified via the MAC signaling or the L1/L2
signaling. The UE may start transmitting the SRS with the SRS
transmission period, from the subframe in which the SRS can be
transmitted for each cell with the earliest timing since receipt of
the SRS transmission period. Since this can omit the notification
of the subframe structure in which the SRS can be transmitted for
each UE, the amount of signaling can be reduced, and the efficient
communication is possible.
[0559] As an alternative method, the eNB may not notify the UE of
the subframe structure in which the SRS can be transmitted for each
cell. The eNB may notify the UE of the subframe structure in which
the SRS can be transmitted for each UE. The eNB may notify the UE
of the subframe structure in which the SRS is to be actually
transmitted.
[0560] The subframe structure in which the SRS is to be actually
transmitted may be notified via the MAC signaling or the L1/L2
control signaling. The UE may start transmitting the SRS with the
SRS transmission period, from the subframe in which the SRS can be
transmitted for each UE with the earliest timing since receipt of
the SRS transmission period. Since this can omit the notification
of the subframe structure in which the SRS can be transmitted for
each cell, the amount of signaling can be reduced, and the
efficient communication is possible.
[0561] As an alternative method, the eNB may notify the UE of only
the subframe structure in which the SRS is to be actually
transmitted. The eNB may successively determine a subframe
structure in which the UE actually transmits the SRS, in
consideration of multiplexing of the SRSs with the other UEs. The
subframe structure may be periodic or aperiodic. The subframe
structure may be notified via the L1/L2 signaling. Consequently,
the SRS transmission timing for each UE can be flexibly
changed.
[0562] As described above, examples of the subframe structure
include a period, a bandwidth, a sub-carrier interval (a comb
value), and a cyclic shift (CS) of the subframe. There may be a
plurality of bandwidths. The bandwidths may be per resource block
or per sub-carrier. The subframe structure may include the number
of SRS transmission symbols, the SRS transmission symbols, a
sequence identifier of the SRS, a frequency hopping pattern of the
SRS, a sequence hopping pattern of the SRS, etc. One or more of
these elements may be combined to be applied to the subframe
structure.
[0563] The subframe structure may include the number of consecutive
SRS transmission symbols and the first SRS transmission symbol.
3GPP is studying a method for the UE to transmit the SRS using a
plurality of consecutive symbols. For example, notification of
these pieces of information as such a subframe structure eliminates
the need for notifying information on the SRS transmission symbols
as many as the number of the SRS transmission symbols. The amount
of information required for the notification can be reduced.
[0564] The subframe structure may include, for example, a bandwidth
for each SRS symbol. The subframe structure may include elements of
the other subframe structures for each SRS symbol. This is
effective when, for example, the bandwidth varies for each SRS
symbol.
[0565] A table indicating associations on information of the
subframe structure may be provided. The cell notifies the UE of one
or more pieces of information in the information of the subframe
structure. The UE derives another information from the notified one
or more pieces of information, using the table. For example, a
table indicating an association between the SRS transmission period
and the SRS transmission bandwidth is provided. Then, the cell
notifies the UE of the SRS transmission period. Upon receipt of the
SRS transmission period, the UE derives the SRS transmission
bandwidth using the table.
[0566] As such, the UE sets a subframe structure derived using the
table and one or more pieces of information in the subframe
structure information notified from the cell. The UE transmits the
SRS according to the derived subframe structure. The table
indicating associations on information of the subframe structure
may be statically predetermined in, for example, a standard or
semi-statically notified from the cell to the UE. The semi-static
notification may be made via the RRC signaling.
[0567] As such, the cell need not specify information derivable
using a table to the UE. The cell implicitly notifies the
information using the other information. Thus, the information to
be notified to the UE can be reduced.
[0568] According to the method illustrated in FIG. 39, the
notification of the SRS transmission period from the cell to the UE
makes the UE start transmitting the periodic SRS. As an alternative
method, information for starting to transmit the periodic SRS may
be separately provided. Notification of the information for
starting to transmit the periodic SRS from the cell to the UE makes
the UE start transmitting the periodic SRS. Upon receipt of the
information for starting to transmit the periodic SRS from the
cell, the UE may start transmitting the periodic SRS. The UE starts
transmitting the periodic SRS after changing the period, along with
the timing of a subframe which is the earliest since receipt of the
information for starting to transmit the periodic SRS from the cell
and in which the SRS can be transmitted.
[0569] The cell may notify the UE of the SRS transmission period
together with the information for starting to transmit the periodic
SRS. The UE starts transmitting the periodic SRS according to the
received SRS transmission period together with the information for
starting to transmit the periodic SRS.
[0570] The cell may notify the UE of the SRS transmission period
separately from the information for starting to transmit the
periodic SRS. Here, the UE may treat the initial value of the SRS
transmission period as a SRS transmission possible period. Until
the cell separately notifies the UE of the SRS transmission period,
the UE sets the preset SRS transmission possible period as the SRS
transmission period, and starts transmitting the periodic SRS. When
the cell separately notifies the UE of the SRS transmission period,
the UE sets the SRS transmission period as the transmission period
of the periodic SRS.
[0571] Consequently, transmission of the periodic SRS can be
started independently from the setting of the SRS transmission
period. Thus, transmission of the periodic SRS can be started
flexibly according to, for example, the radio propagation
environment.
[0572] As an alternative method, information for starting to
transmit the periodic SRS may not be provided. The notification of
the subframe structure in which the SRS can be transmitted from the
cell to the UE may make the UE start transmitting the periodic SRS.
Here, the UE may treat the initial value of the SRS transmission
period as the SRS transmission possible period. Until the cell
separately notifies the UE of the SRS transmission period, the UE
sets the preset SRS transmission possible period as the SRS
transmission period, and starts transmitting the periodic SRS. When
the cell separately notifies the UE of the SRS transmission period,
the UE sets the SRS transmission period as the transmission period
of the periodic SRS.
[0573] When the cell desires to change the SRS transmission period,
the cell only needs to notify the UE of the SRS transmission period
via the L1/L2 control signal. Thus, the amount of information
required for the notification can be reduced.
[0574] The information indicating a value of the SRS transmission
period is used as the SRS transmission period in the aforementioned
method. Here, another example method for setting the SRS
transmission period will be described. For example, the SRS
transmission period is n times a base period (n is a positive
integer), assuming that the base period is a SRS transmission
possible period that is a period of the subframe in which the SRS
can be transmitted for each UE. The subframe in which the SRS is to
be actually transmitted can be set to be included in the subframe
in which the SRS can be transmitted.
[0575] The amount of information indicating the value n suffices
for the amount of information indicating the SRS transmission
period. Thus, the amount of information can be less than that when
the value of the SRS transmission period is directly given. The
amount of information to be notified from the cell to the UE can be
reduced. Furthermore, n=0 may be added. The SRS transmission may be
stopped when n=0.
[0576] The SRS transmission period may be 2.sup.(n-1) times the
base period (n is a positive integer) as another setting method
thereof. Consequently, the subframe in which the SRS is to be
actually transmitted can be set to be included in the subframe in
which the SRS can be transmitted. The period can be changed more
greatly than that when the SRS transmission period is n times the
base period, with the same amount of information used. Furthermore,
n=0 may be added. The SRS transmission may be stopped when n=0.
Alternatively, the SRS transmission period may be 2.sup.n times the
base period (n is an integer larger than or equal to 0). When all
the bits indicating n indicate 1, the SRS transmission may be
stopped.
[0577] When the SRS transmission is stopped, n=0. The value may be
a specific value of another n. For example, when all the bits
indicating n indicate 1, the SRS transmission may be stopped.
Statically predetermining the value indicating stopping the SRS
transmission in, for example, a standard enables both the cell and
the UE to recognize the stop of the SRS transmission.
[0578] Another example setting method will be disclosed. A table
with the SRS transmission period indexed by a number is provided.
The table may be predetermined in, for example, a standard.
Alternatively, the table may be broadcast from the cell to the UE,
or notified from the cell to the UE via the RRC-dedicated
signaling. Information indicating the SRS transmission period is
represented by the number. The cell selects the SRS transmission
period from the table, and notifies the UE of the number indexed to
the selected SRS transmission period. The UE derives the SRS
transmission period from the received number and the table, and
sets the SRS transmission period as the transmission period of the
periodic SRS.
[0579] Consequently, any SRS transmission period can be set.
Narrowing down the SRS transmission periods to the number needed
enables reduction in the amount of information.
[0580] Another example method for setting the SRS transmission
period will be described. Information indicating an increment or a
decrement from the SRS transmission period currently set is
provided. The initial value of the SRS transmission period may be
of the SRS transmission possible period. The SRS transmission
period currently set is assumed to be once per "a" times of SRS
transmission possible subframes. To increase the SRS transmission
period, the SRS transmission period is prolonged as once per (a+1)
times of SRS transmission possible subframes. To reduce the SRS
transmission period, the SRS transmission period is shortened as
once per (a-1) times of SRS transmission possible subframes.
[0581] The maximum and minimum setting values of the SRS
transmission period may be determined. Even if the SRS transmission
period is greater than the maximum setting value in the setting
according to the increment and decrement information of the SRS
transmission period, the SRS transmission period is maintained at
the maximum setting value. Similarly, if the SRS transmission
period is less than the minimum setting value in the setting, the
SRS transmission period is maintained at the minimum setting value.
The minimum setting value may be of the SRS transmission possible
period. The maximum and minimum setting values of the SRS
transmission period may be predetermined in, for example, a
standard, or notified from the cell to the UE.
[0582] Another method for setting the SRS transmission period
includes setting, as the SRS transmission period, the information
indicating an increment or a decrement from the SRS transmission
period currently set, which enables the amount of information to
equal 1 bit and further enables reduction in the amount of
information to be notified from the cell to the UE.
[0583] An offset value of the SRS subframe to be actually
transmitted (hereinafter may be referred to as a "SRS transmission
offset value") may be set separately from the SRS transmission
period. The SRS transmission offset value may be, for example,
time. The SRS transmission offset value may be, for example, the
number of SRS transmission possible subframes from the setting of
the SRS transmission period to starting to transmit the periodic
SRS. For example, when the cell sets 3 to the SRS transmission
offset value, the UE starts transmitting the periodic SRS in the
third SRS transmission possible subframe since receipt of the
setting of the SRS transmission period.
[0584] The cell may notify the UE of offset information on the SRS
subframe to be actually transmitted (hereinafter may be referred to
as "SRS transmission offset information") together with the SRS
transmission period. The UE starts transmitting the periodic SRS,
with the received SRS transmission period and the SRS transmission
offset information.
[0585] Alternatively, the cell may notify the UE of the SRS
transmission offset information separately from the SRS
transmission period. The UE may treat the initial value of the SRS
transmission offset as an offset up to the earliest subframe in
which the SRS can be transmitted since receipt of the SRS
transmission period. When the cell separately notifies the UE of
the SRS transmission offset value, the UE reconfigures a subframe
in which the periodic SRS is to be transmitted, with the received
SRS transmission offset value. Setting the offset value in such a
manner enables the cell to flexibly set the transmission start
timing of the periodic SRS.
[0586] The offset information may be a remainder obtained by
dividing the subframe number in which the SRS is to be transmitted
by the SRS transmission period. This enables designation of a
unique offset to the UE, regardless of the notification timing of
the SRS transmission period from the cell to the UE.
[0587] When the cell notifies the UE of the offset information
together with information for stopping transmission of the periodic
SRS, the offset information indicates the SRS transmission time or
the number of SRS transmission possible subframes from setting of
the SRS transmission stopping information to stopping transmission
of the periodic SRS. The UE stops transmitting the periodic SRS
after a lapse of the offset information from receipt of the
information for stopping the SRS transmission.
[0588] The offset information that is information for starting the
SRS transmission and the offset information that is information for
stopping the SRS transmission may be different parameters. The cell
sets these pieces of information to different parameters, and
notifies the UE of the parameters. The UE can recognize whether the
offset information is the information for starting the SRS
transmission or the information for stopping the SRS
transmission.
[0589] FIGS. 40 to 42 illustrate methods for transmitting the
periodic SRS when the SRS transmission offset is set together with
the SRS transmission period. Since FIGS. 40 to 42 are similar to
FIG. 39, the differences will be mainly described. In FIGS. 40 to
42, the horizontal axis represents time t.
[0590] FIG. 40 illustrates a method for transmitting the periodic
SRS with the SRS transmission period identical to the SRS
transmission possible period for each UE. The cell includes the
changed SRS transmission period in the DCI, maps the DCI to a
physical control channel, and notifies the UE of the physical
control channel to change the period of the periodic SRS. The cell
also includes the SRS transmission offset in the DCI together with
the SRS transmission period, and notifies the UE of the DCI.
[0591] FIG. 41 illustrates a method for transmitting the periodic
SRS after changing the SRS period when the SRS transmission offset
value is 1. The cell sets the SRS transmission period to the UE,
and sets 1 to the SRS transmission offset value. Upon receipt of
the SRS transmission period and the SRS transmission offset value
from the cell, the UE changes the period into the SRS transmission
period that has been set from the first SRS transmission possible
subframe since setting of the SRS transmission offset. Then, the UE
starts transmitting the periodic SRS.
[0592] FIG. 42 illustrates a method for transmitting the periodic
SRS after changing the SRS period when the SRS transmission offset
value is 2. The cell sets the SRS transmission period to the UE,
and sets 2 to the SRS transmission offset value. Upon receipt of
the SRS transmission period and the SRS transmission offset value
from the cell, the UE changes the period into the SRS transmission
period that has been set from the second SRS transmission possible
subframe since setting of the SRS transmission offset. Then, the UE
starts transmitting the periodic SRS.
[0593] Consequently, the cell can set a different offset value to
each UE with the same SRS transmission period. According to this
setting, a different SRS transmission subframe can be set to each
UE. Furthermore, the SRS transmission timing appropriate for each
UE can be flexibly set to a plurality of the UEs.
[0594] The following (1) to (7) will be disclosed as specific
examples of a judgment indicator for changing the SRS transmission
period:
[0595] (1) channel quality information of the UE;
[0596] (2) the moving speed of the UE;
[0597] (3) acceleration (change in the speed) of the UE;
[0598] (4) the rotational speed of the UE;
[0599] (5) rotational acceleration (change in the rotational speed)
of the UE;
[0600] (6) the number of multiplexed UEs; and
[0601] (7) combinations of (1) to (6) above.
[0602] Taking, as the judgment indicator, the channel quality
information of the UE in (1), for example, when the channel quality
is inferior, the SRS transmission period is set shorter. When the
channel quality is superior, the SRS transmission period is set
longer. The UE transmits the SRS to the cell with a short period
when the channel quality is inferior, so that the cell can increase
the probability of receiving the SRS. The cell can also reflect a
state where the channel quality is inferior on deriving of a
pre-coding weight with low latency. Consequently, the precoding
performance can be improved.
[0603] Taking, as the judgment indicator, the moving speed of the
UE in (2), for example, when the moving speed is higher, the SRS
transmission period is set shorter. When the moving speed is lower,
the SRS transmission period is set longer. When the moving speed is
higher, the UE transmits the SRS to the cell with a short period,
and the cell receives the SRS with the short period. Thus, the
influence of the Doppler frequency due to the moving speed of the
UE can be reduced. Thus, precision of the SRS can be increased, and
the precoding performance can be improved.
[0604] Taking, as the judgment indicator, the acceleration (change
in the speed) of the UE in (3), for example, when the acceleration
is greater, the SRS transmission period is set shorter. When the
acceleration is less, the SRS transmission period is set longer.
When the acceleration is greater, the UE transmits the SRS to the
cell with a short period, and the cell receives the SRS with the
short period. Thus, change in the moving speed of the UE can be
reflected earlier. Consequently, the precoding performance can be
improved.
[0605] Taking, as the judgment indicator, the rotational speed of
the UE in (4), for example, when the rotational speed is higher,
the SRS transmission period is set shorter. When the rotational
speed is lower, the SRS transmission period is set longer. When the
rotational speed is higher, the UE transmits the SRS to the cell
with a short period, and the cell receives the SRS with the short
period. Thus, the rotation of the UE can be reflected earlier.
Consequently, the precoding performance can be improved.
[0606] Taking, as the judgment indicator, the rotational
acceleration (change in the rotational speed) of the UE in (5), for
example, when the rotational acceleration is greater, the SRS
transmission period is set shorter. When the rotational
acceleration is less, the SRS transmission period is set longer.
When the rotational acceleration is greater, the UE transmits the
SRS to the cell with a short period, and the cell receives the SRS
with the short period. Thus, change in the rotational speed of the
UE can be reflected earlier. Consequently, the precoding
performance can be improved.
[0607] Taking, as the judgment indicator, the number of multiplexed
UEs in (6), for example, when the number of multiplexed UEs is
many, the SRS transmission period is set shorter. When the number
of multiplexed UEs is few, the SRS transmission period is set
longer. When the number of multiplexed UEs in the MIMO is many, the
UE transmits the SRS to the cell with a short period, and the cell
receives the SRS with the short period. Thus, the precision of the
SRS can be increased for each UE. Consequently, even when the
number of multiplexed UEs is many, the precoding weight with higher
precision can be derived, and the precoding performance can be
improved.
[0608] The cell obtains information on the judgment indicator for
changing the SRS transmission period. The cell may measure the
information, or obtain the information from the UE. The cell may
appropriately determine, for each piece of information on the
judgment indicators, whether to measure or obtain the information.
In the examples of the judgment indicators described above, the
cell may measure (1) and (6), and the UE may measure (2) to
(5).
[0609] When the cell obtains information on a judgment indicator
from the UE, the UE measures the information, and notifies it to
the cell. The notification method may be the RRC signaling.
Alternatively, the notification method may be the MAC signaling.
The information may be included in the MAC control information to
be notified via the MAC signaling. Consequently, the cell can
obtain the information on the judgment indicator measured by the UE
earlier than that via the RRC signaling.
[0610] Alternatively, the notification method may be the L1/L2
control signaling. The information may be included in the uplink
L1/L2 control information (UCI) to be notified via the L1/L2
control signaling. Consequently, the cell can obtain the
information on the judgment indicator measured by the UE much
earlier than that via the MAC signaling.
[0611] When the information on the judgment indicator consists of
measurement values thereof, the amount of information increases. A
table indicating a range of the measurement values and an index
given to the range may be created. The table may be statically
predetermined in, for example, a standard. The index is used as the
information on the judgment indicator. Use of the index can reduce
the amount of information on the judgment indicator. The amount of
information carried by the MAC control information or the L1/L2
control information should be less. Thus, application of indices to
these is effective.
[0612] FIG. 43 illustrates an example sequence for setting the SRS
transmission period according to the second embodiment. The example
illustrated in FIG. 43 discloses a method for starting or changing
transmission of the periodic SRS according to the setting of the
SRS transmission period for each UE.
[0613] In Step ST3301, the cell includes, in SIB, a subframe
structure in which the SRS can be transmitted for each cell, and
broadcasts the SIB to the UEs being served thereby.
[0614] In Step ST3302, the cell determines a subframe structure in
which the SRS can be transmitted for each UE, in consideration of
multiplexing of SRSs among a plurality of UEs that set the SRSs.
The cell may determine the SRS transmission possible period for
each UE.
[0615] In Step ST3303, the cell notifies the UE of the subframe
structure in which the SRS can be transmitted for each UE. This
notification may be made via the RRC-dedicated signaling. The UE
does not start transmitting the periodic SRS upon this
notification.
[0616] In Step ST3304, the cell determines to start transmitting
the periodic SRS for each UE.
[0617] In Step ST3305, the cell sets the SRS transmission period
and the SRS transmission offset value to each of the UEs for which
the cell has determined to start transmitting the periodic SRS. In
these settings, the SRS transmission possible period may be set to
the SRS transmission period, and 1 may be set to the SRS
transmission offset value as the initial value. The UE transmits
the periodic SRS in a subframe in which the SRS can be transmitted
for each UE.
[0618] In Step ST3306, the cell notifies the SRS transmission
period and the SRS transmission offset value to each of the UEs for
which the cell has determined to start transmitting the periodic
SRS. These pieces of information may be included in the DCI as
L1/L2 control information to be notified via the L1/L2 signaling.
Consequently, the cell can notify the UE of the SRS transmission
period and the SRS transmission offset value earlier, after setting
the SRS transmission period and the SRS transmission offset
value.
[0619] Upon receipt of the SRS transmission period and the SRS
transmission offset value in Step ST3306, the UE derives a subframe
in which the SRS is to be transmitted, according to the received
SRS transmission period and the received SRS transmission offset
value in Step ST3307.
[0620] In Step ST3308, the UE starts transmitting the periodic SRS
in the subframe derived in Step ST3307.
[0621] In Step ST3309, the cell determines whether to change at
least one of the SRS transmission period and the SRS transmission
offset value for the UE that has started transmitting the periodic
SRS. The aforementioned judgment indicators for changing the SRS
transmission period are used in this determination.
[0622] When it is determined that at least one of the SRS
transmission period and the SRS transmission offset value needs to
be changed in Step ST3309, the process returns to Step ST3305, and
at least one of the SRS transmission period and the SRS
transmission offset value for each UE is set. In these settings,
how much change is necessary is derived using the judgment
indicators for changing the SRS transmission period, so that at
least one of the SRS transmission period and the SRS transmission
offset value may be set.
[0623] In Step ST3309, the cell may determine whether to stop
transmitting the periodic SRS, in addition to the determination on
whether to change at least one of the SRS transmission period and
the SRS transmission offset value.
[0624] Upon determination of stopping transmission of the periodic
SRS, the cell returns to the process in Step ST3305, and sets
stopping of transmitting the periodic SRS as the SRS transmission
period for each UE.
[0625] The cell that determines not to stop transmitting the
periodic SRS and determines that it is not necessary to change the
SRS transmission period and the SRS transmission offset value in
Step ST3309 continues to receive the periodic SRS in the same
settings. Without any notification of changing or stopping the
periodic SRS, the UE continues to transmit the periodic SRS in the
same settings.
[0626] The second embodiment enables the UE to stop transmitting
the periodic SRS according to information for stopping transmission
of the periodic SRS. Thus, the timing to transmit, to the UE, the
information for stopping transmission of the SRS may be after the
timing to transmit, to the UE, the information for starting the
SRS. The cell may transmit, for example, the offset information for
specifying a duration for stopping transmission of the SRS to the
UE together with the information for starting to transmit the SRS.
The cell may transmit the offset information for specifying a
duration for stopping transmission of the SRS, for example, at the
desired timing to make the UE stop transmitting the SRS. The UE
stops transmitting the SRS according to the received offset
information for specifying a duration for stopping transmission of
the SRS.
[0627] Transmission of the offset information for specifying a
duration for stopping transmission of the SRS together with the
information for starting to transmit the SRS enables the UE to stop
transmitting the SRS after the duration since transmission of the
SRS. This eliminates the need for separately notifying the
information for stopping transmission of the SRS.
[0628] When the SRS transmission period is set and changed, setting
the SRS transmission period as the L1/L2 control information and
notifying the SRS transmission period via the L1/L2 control
signaling allows notification with a shorter period of time than
that by changing the SRS transmission period using the conventional
RRC signaling, as disclosed in this second embodiment. The time
from when the cell determines to change at least one of the SRS
transmission period and the SRS transmission offset value to when
the UE transmits the periodic SRS in the changed setting can be
shorter than the conventional time.
[0629] Since this enables reduction in the latency in the periodic
settings of the SRS, the UE can transmit the SRS when necessary.
Thus, the precoding performance for the downlink MIMO can be
improved.
[0630] As described above, the subframe structure in which the SRS
is to be actually transmitted may be notified via the MAC signaling
or the L1/L2 control signaling. A subframe structure in which the
other SRSs are to be actually transmitted may be notified together
with the transmission period of the subframe in which the SRS is to
be actually transmitted. The subframe structure in which the SRS is
to be actually transmitted may be notified together with
information for starting to transmit the SRS.
[0631] A plurality of subframe structures in which the SRS can be
transmitted for each cell may be set. A plurality of subframe
structures in which the SRS can be transmitted for each UE may be
set. One of the plurality of subframe structures in which the SRS
can be transmitted for each UE may be selected, and the subframe
structure in which the SRS is to be actually transmitted for each
UE may be set to be a part or the entirety of the selected subframe
structure in which the SRS can be transmitted for each UE.
[0632] For example, one of the plurality of subframe structures in
which the SRS can be transmitted for each cell may be selected, and
a part or the entirety of the selected subframe structure may be
applied to the subframe structure in which the SRS is to be
actually transmitted for each UE. These are appropriately set in
the aforementioned setting methods, for example, in a setting
method depending on whether the eNB notifies the UE of only the
subframe structure in which the SRS is to be actually
transmitted.
[0633] This increases patterns of the subframe structures in which
the SRS is to be actually transmitted for each UE. Thus, the SRS
more appropriate for, for example, the moving speed and the radio
propagation environment of the UE can be transmitted.
[0634] FIG. 44 illustrates an example SRS transmission sequence
when a plurality of subframes in which the SRS can be transmitted
are configured. In Step ST6201, the cell sets a subframe structure
in which the SRS can be transmitted for each cell, and notifies the
UE of the setting. The cell may notify information on the set
subframe structure as system information. In Step ST6202, the cell
determines a plurality of SRS structures for each UE. In Step
ST6203, the cell notifies the UE of the determined plurality of
subframe structures in which the SRS can be transmitted for each
UE. This notification may be made via the UE-dedicated RRC
signaling.
[0635] In Step ST6204, the cell selects one of the determined
plurality of subframe structures in which the SRS can be
transmitted for each UE to make the UE actually transmit the SRS.
In Step ST6205, the cell notifies the UE of the selected SRS
transmission subframe structure. In the previous Step ST6203,
identifiers may be assigned to the respective subframe structures
in which the SRS can be transmitted for each UE, and such
identifiers may also be transmitted. In such a case, the cell may
notify the UE of the identifier of the selected subframe structure
in which the SRS can be transmitted in Step ST6205.
[0636] In the example illustrated in FIG. 44, notification of one
of the SRS transmission subframe structures or an identifier
indicating the one of the SRS transmission subframe structures is
used as information for starting to transmit the SRS. In Step
ST6206, the UE selects the subframe structure in which the SRS is
to be actually transmitted, using the plurality of subframe
structures in which the SRS can be transmitted for each UE that are
notified in Step ST6203, and the identifier notified in Step
ST6205. In Step ST6207, the UE starts transmitting the SRS
according to the selected subframe structure.
[0637] Making the notification in Step ST6205 via the L1/L2 control
signaling enables the UE to start transmitting the SRS dynamically
with low latency.
[0638] In Step ST6208, the cell determines whether to stop
transmission of the SRS by the UE. When determining not to stop the
transmission, the cell continues to receive the SRS. When
determining to stop the transmission of the SRS, the cell notifies
the UE of information for stopping the SRS in Step ST6209.
[0639] In Step ST6210, the UE stops transmitting the SRS according
to the information for stopping transmission of the SRS that has
been notified in Step ST6209. Making the notification in Step
ST6209 via the L1/L2 control signaling enables the UE to stop
transmitting the SRS dynamically with low latency.
[0640] Although notification of one of the SRS transmission
subframe structures or the identifier indicating the one of the SRS
transmission subframe structures is used as information for
starting to transmit the SRS in the example illustrated in FIG. 44,
the information for starting to transmit the SRS may be notified
instead. The information for starting to transmit the SRS may be
notified together with one of the SRS transmission subframe
structures or the identifier indicating the one of the SRS
transmission subframe structures. The UE selects the subframe
structure in which the SRS is to be actually transmitted, using the
notified plurality of subframe structures in which the SRS can be
transmitted for each UE, and the notified identifier, and starts
transmitting the SRS according to the notified information for
starting to transmit the SRS.
[0641] Notifying the UE of a plurality of subframe structures in
which the SRS can be transmitted and selecting one of the subframe
structures can reduce the amount of information to be notified via
the L1/L2 control signal. This can increase the use efficiency of
the radio resources.
[0642] When not the plurality of subframe structures in which the
SRS can be transmitted, but only one of the subframe structures in
which the SRS can be transmitted is notified in Step ST6203, the
cell only needs to determine in Step ST 6204 whether to make the UE
start transmitting the SRS and to notify the UE of the information
for starting to transmit the SRS in Step ST6205. The UE starts
transmitting the SRS according to the notified information for
starting to transmit the SRS.
[0643] FIGS. 45 and 46 illustrate an example SRS transmission
sequence when a plurality of subframes in which the SRS can be
transmitted are configured to change the SRS subframe structure.
FIGS. 45 and 46 are connected across a location of a border BL15.
In Step ST6301, the cell determines the initial SRS transmission
subframe structure. In Step ST6302, the cell notifies the UE of a
plurality of subframe structures in which the SRS can be
transmitted for each UE. The cell notifies the UE of an identifier
of the initial SRS transmission subframe structure together with
the plurality of SRS subframe structures. This notification may be
made via the UE-dedicated RRC signaling.
[0644] In Step ST6303, the UE selects the subframe structure in
which the SRS is to be actually transmitted, using the plurality of
subframe structures in which the SRS can be transmitted for each UE
and the identifier of the initial SRS transmission subframe
structure all of which have been notified in Step ST6302. In Step
ST6304, the UE starts transmitting the SRS according to the
selected subframe structure.
[0645] In Step ST6305, the cell determines to change the SRS
transmission subframe structure. In Step ST6306, the cell selects
one of the plurality of subframe structures in which the SRS can be
transmitted that have been determined in Step ST6302. In Step
ST6307, the cell notifies the UE of the selected SRS transmission
subframe structure. Here, the cell may notify the UE of the
selected SRS transmission subframe structure using the
identifier.
[0646] In Step ST6308, the UE selects the subframe structure in
which the SRS is to be actually transmitted, using the plurality of
subframe structures in which the SRS can be transmitted for each UE
that have been notified in Step ST6302, and the identifier notified
in Step ST6307. In Step ST6309, the UE starts transmitting the SRS
according to the selected subframe structure.
[0647] Making the notification in Step ST6307 via the L1/L2 control
signaling enables the UE to start transmitting the SRS dynamically
with low latency.
[0648] In Step ST6310, the cell determines whether to make the UE
stop transmitting the SRS. When determining not to stop the
transmission, the cell continues to receive the SRS. In Step
ST6312, the cell determines whether to change the SRS transmission
subframe structure. When the cell determines to change the SRS
transmission subframe structure, the sequence returns to Step
ST6306. When the cell determines not to change the SRS transmission
subframe structure, the cell continues to receive the SRS in Step
ST6309.
[0649] When determining to stop the transmission of the SRS in Step
ST6310, the cell notifies the UE of information for transmitting
the SRS in Step ST6209.
[0650] In Step ST6210, the UE stops transmitting the SRS according
to the information for stopping transmission of the SRS that has
been notified in Step ST6209. Making the notification in Step
ST6209 via the L1/L2 control signaling enables the UE to stop
transmitting the SRS dynamically with low latency.
[0651] As such, the UE is notified of a plurality of subframe
structures in which the SRS can be transmitted, and one of the
subframe structures is selected. Consequently, the UE only needs to
be notified of the identifier even in changing the subframe in
which the SRS is to be actually transmitted, which can reduce the
amount of information to be notified via the L1/L2 control signal.
This can increase the use efficiency of the radio resources.
[0652] A plurality of subframe structures in which the SRS is to be
actually transmitted for each UE may be set to one UE. This can
increase the transmission patterns of the SRS. A subframe structure
in which the SRS is to be actually transmitted for each UE may be
set to each of the subframe structures in which the SRS can be
transmitted for each UE. This can further increase the transmission
patterns of the SRS. Thus, the SRS more appropriate for, for
example, the moving speed and the radio propagation environment of
the UE can be transmitted.
[0653] The information for stopping transmission of the SRS may
include the SRS transmission subframe structure or information
indicating the SRS transmission subframe structure. The information
indicating the SRS transmission subframe structure may be, for
example, the aforementioned identifier. Since the transmission
pattern of the SRS whose transmission is to be stopped can be
uniquely identified from the plurality of subframe structures in
which the SRS is to be actually transmitted for each UE,
flexibility can be provided to the settings for transmitting the
SRS. The same may hold true for information for changing
transmission of the SRS.
[0654] Application of the aforementioned method enables setting of
transmitting a plurality of SRSs at one time. For example, a
plurality of subframe structures are set to the UE as subframe
structures in which the SRS can be transmitted for each cell or for
each UE, and a plurality of subframe structures in which the SRS is
to be actually transmitted among the set plurality of subframe
structures are set to the UE. Alternatively, only a plurality of
subframe structures may be set to the UE as the subframe structures
in which the SRS is to be actually transmitted for each UE. The UE
transmits the SRS according to the set plurality of subframe
structures in which the SRS is to be actually transmitted. As
described above, the subframe structure may be configured per
symbol. The SRS can be transmitted using a plurality of symbols in
one subframe.
[0655] Changing the number of settings for transmitting the SRS at
one time enables setting of a plurality of SRS transmission
patterns. The cell may dynamically change the number of settings
for transmitting the SRS at one time. The cell may set the number
of settings for transmitting the SRS at one time, simultaneously
when changing the SRS transmission period. The cell may set the
number of settings for transmitting the SRS at one time, in the
same method as that for changing the SRS transmission period.
[0656] A plurality of SRS transmission patterns may be prepared in
advance, and one of the SRS transmission patterns may be selected.
The plurality of SRS transmission patterns can be prepared by
changing, for example, the number of settings for transmitting the
SRS that is included in the subframe structure or the SRS
transmission period in each of the settings for transmitting the
SRS, etc. The plurality of SRS transmission patterns may be
statically predetermined in, for example, a standard or
semi-statically notified from the cell to the UE via, for example,
the RRC signaling. Each of the SRS transmission patterns may have
an identifier. The cell notifies the UE of the identifier of the
pattern. The UE starts transmitting the SRS, according to the
received identifier of the pattern and the setting for the SRS
corresponding to the pattern.
[0657] Consequently, various SRS transmission patterns including
the plurality of SRS transmission patterns can be set, and the UE
can transmit the SRS with the various SRS transmission patterns.
The settings appropriate for various communication services of the
UE and appropriate for transmitting the SRS in various situations
are possible.
[0658] The LTE allows not only the settings for the periodic SRS
but also the settings for the aperiodic SRS. The settings for the
periodic SRS according to the methods disclosed in the second
embodiment may be combined with a method for setting the periodic
SRS and a method for setting the aperiodic SRS in the LTE for use.
When the SRS period needs to be changed with low latency, the
periodic SRS disclosed in the second embodiment may be set, or the
SRS transmission period of the periodic SRS that is disclosed in
the second embodiment may be changed. Which SRS is to be set or
changed may be appropriately determined according to, for example,
a required latency amount.
[0659] The subframe structure in which the SRS can be transmitted
for each cell may be notified between adjacent eNBs. The subframe
structure in which the SRS can be transmitted for each UE may be
notified between adjacent eNBs. The subframe structure in which the
SRS is to be actually transmitted for each UE may be notified
between adjacent eNBs. The notification between adjacent eNBs may
be made directly or through a core network (CN) node. This enables
the UE to transmit the SRS coordinated among the adjacent eNB
s.
[0660] For example, in a handover (HO) between eNBs, a source eNB
(S-eNB) that is a HO-source eNB may notify a target eNB (T-eNB)
that is a HO-target eNB of a subframe structure in which the SRS
can be transmitted for each cell that is a HO-source cell, a
subframe structure in which the SRS can be transmitted for each UE
that is a UE subject to the HO, and a subframe structure in which
the SRS is to be actually transmitted for each UE. The subframe
structures may be notified via a signaling for a HO request.
[0661] Consequently, the T-eNB can set, in consideration of the SRS
subframe structure of the UE in the HO-source cell, a subframe
structure in which the SRS can be transmitted for each cell that is
a HO-target cell, the subframe structure in which the SRS can be
transmitted for each UE that is the UE subject to the HO, and the
subframe structure in which the SRS is to be actually transmitted
for each UE.
[0662] 3GPP is studying a transmission reception point (TRP) and a
dedicated unit (DU) as NR nodes. The methods disclosed in the
second embodiment may be applied to the TRP and the DU. The methods
disclosed in the second embodiment may be applied, using the TRP
and the DU instead of the cells.
[0663] Alternatively, only the subframe structure in which the SRS
can be actually transmitted may be set for each TRP or each DU. The
subframe structure in which the SRS can be transmitted for each
cell and the subframe structure in which the SRS can be transmitted
for each UE may be set for each high-level node of the TRP or for
each high-level node of the DU, for example, for each central unit
(CU). For example, even when the UE moves between the TRPs or
between the DUs, the subframe structure in which the SRS can be
actually transmitted only needs to be set, without any need for
reconfiguring the subframe structure in which the SRS can be
transmitted for each cell and the subframe structure in which the
SRS can be transmitted for each UE.
[0664] The subframe structure in which the SRS can be actually
transmitted for each UE may be notified between the TRP or the DU
and its high-level node. When the UE moves between the TRPs or
between the DUs, the subframe structure in the UE that moves
between the TRPs or between the DUs and in which the SRS can be
actually transmitted may be notified. This notification may be made
via the high-level node.
[0665] Application of the methods disclosed in the second
embodiment to the TRPs and the DUs enables improvement in the
precoding performance even when the downlink MIMO using the TRPs
and the DUs is performed.
First Modification of Second Embodiment
[0666] The first modification will disclose another method for
solving the problems disclosed in the second embodiment.
[0667] A period with which the UE actually transmits the periodic
SRS (hereinafter may be referred to as a "SRS transmission period")
is set as the MAC control information. The period may be provided
as a MAC control element (CE). The cell notifies the UE of the
period via the MAC signaling. The first embodiment may be applied
to information to be set.
[0668] The HARQ is applied in making the notification via the MAC
signaling. When the UE cannot accurately receive the MAC signaling
notified from the cell, the UE transmits Nack to the cell. Then,
the cell performs the retransmission to the UE under the
retransmission control.
[0669] Thus, the setting with consideration given to the
retransmission is a must, unlike the notification via the L1/L2
control signaling.
[0670] When acknowledging that the UE has accurately received the
MAC signaling including the SRS transmission period transmitted to
the UE, the cell changes reception of the periodic SRS with the set
SRS transmission period. Upon the accurate receipt of the MAC
signaling including the SRS transmission period transmitted from
the cell, the UE changes transmission of the periodic SRS with the
set SRS transmission period.
[0671] When acknowledging receipt of Ack from the UE in response to
the MAC signaling including the SRS transmission period transmitted
to the UE, the cell changes reception of the periodic SRS with the
set SRS transmission period. After accurately receiving the MAC
signaling including the SRS transmission period transmitted from
the cell and then transmitting Ack, the UE changes transmission of
the periodic SRS with the set SRS transmission period.
[0672] The same holds true when transmission of the periodic SRS is
started upon notification of the SRS transmission period.
[0673] When acknowledging that the UE has accurately received the
MAC signaling including the SRS transmission period transmitted to
the UE, the cell starts receiving the periodic SRS with the set SRS
transmission period. Upon the accurate receipt of the MAC signaling
including the SRS transmission period transmitted from the cell,
the UE starts transmitting the periodic SRS with the set SRS
transmission period.
[0674] The same holds true when the SRS transmission offset is
set.
[0675] When acknowledging that the UE has accurately received the
MAC signaling including the SRS transmission period transmitted to
the UE, the cell counts the SRS transmission offset. Upon the
accurate receipt of the MAC signaling including the SRS
transmission period transmitted from the cell, the UE counts the
SRS transmission offset.
[0676] For example, when the SRS transmission offset value is the
number of subframes in which the SRS can be transmitted since the
setting of the SRS transmission period until start of transmission
of the periodic SRS, the cell acknowledges that the UE has
accurately received the MAC signaling including the SRS
transmission period transmitted to the UE, and then changes
reception of the periodic SRS with the set SRS transmission period
in a subframe after the SRS transmission offset that is a subframe
in which the SRS can be transmitted. Upon the accurate receipt of
the MAC signaling including the SRS transmission period transmitted
from the cell, the UE changes transmission of the periodic SRS with
the set SRS transmission period in the subframe after the SRS
transmission offset that is the subframe in which the SRS can be
transmitted.
[0677] Consequently, the timing for the UE to start transmission
and reception of the periodic SRS can coincide with that in the
cell. Consequently, the process of transmitting the periodic SRS
can be executed without any malfunction in a system. This holds
true for starting and stopping the periodic SRS.
[0678] Similarly, when information for starting to transmit the SRS
or information for stopping transmitting the SRS is notified via
the MAC signaling, the timing for the UE to start or stop
transmission and reception of the periodic SRS can coincide with
that in the cell. Consequently, the process of transmitting the
periodic SRS can be executed without any malfunction in a
system.
[0679] Similarly as the second embodiment, the offset information
may be a remainder obtained by dividing the subframe number in
which the SRS is to be transmitted by the SRS transmission period.
Consequently, the cell and the UE can use a unique offset,
regardless of the presence or absence of retransmission of the MAC
signaling to the UE.
[0680] When the SRS transmission period is changed, setting the SRS
transmission period as the MAC control information and notifying
the SRS transmission period via the MAC signaling allows the
notification with a shorter period of time than that in changing
the SRS transmission period via the conventional RRC signaling, as
disclosed in this second embodiment. The time from when the cell
determines to change at least one of the SRS transmission period
and the SRS transmission offset value to when the UE transmits the
periodic SRS in the changed setting can be shorter than the
conventional time.
[0681] Since this enables reduction in the latency in the periodic
settings of the SRS, the UE can transmit the SRS when necessary.
Thus, the precoding performance for the downlink MIMO can be
improved.
[0682] The retransmission control is applied when the MAC signaling
is used, unlike when the L1/L2 control signaling is used as
disclosed in the second embodiment. Consequently, the cell can
receive the SRS transmitted from the UE at a lower error rate.
Thus, the precoding performance can be improved.
Second Modification of Second Embodiment
[0683] The SRS transmission period is set according to the
determination by the eNB in the second embodiment and the first
modification of the second embodiment. However, while the eNB
measures a reception condition of the UE using the SRS with
reciprocity, if the set SRS period is long, the eNB cannot
understand sudden change in the reception condition of the UE.
Here, the eNB cannot receive the SRS with a period appropriate for
fluctuations in the moving speed of the UE with a short period of
time and appropriate for sudden change in the radio propagation
environment. Thus, a problem of degradation in the precoding
performance occurs.
[0684] The second modification will disclose a method for solving
such a problem.
[0685] The UE requests the cell to change the SRS transmission
period. Information for requesting change in the SRS transmission
period is provided. Then, the UE notifies the cell of the
information. The information for requesting change in the SRS
transmission period may be information indicating whether to make
the request. The information may be information of 1 bit.
[0686] A method for notifying the information for requesting change
in the SRS transmission period (hereinafter may be referred to as
"SRS period change request information") will be disclosed. The SRS
period change request information is set as uplink L1/L2 control
information. The UE notifies the cell of the SRS period change
request information via the L1/L2 control signaling. The UE may
notify the SRS period change request information as uplink control
information (UCI) to be transmitted via the uplink L1/L2 control
signaling. The UE may map the SRS period change request information
to an uplink physical control channel and notify the uplink
physical control channel.
[0687] The UE may include the SRS period change request information
in the UCI, map the UCI to a physical dedicated control channel,
and notify the cell of the physical dedicated control channel.
Here, the physical dedicated control channel is the PUCCH in the
LTE. The cell may preset a configuration of the physical dedicated
control channel and a method for mapping the physical dedicated
control channel to the physical resources that are used for
notifying the SRS period change request information, and notify the
UE of the configuration and the method. This notification may be
made via the RRC-dedicated signaling. Alternatively, the
configuration and the method may be statically determined in, for
example, a standard. The methods identical to those for the
scheduling request (SR) in the LTE may be applied to these methods
(see 3GPP TS 36.211 V13.2.0 (hereinafter referred to as "Reference
4") and 3GPP TS 36.213 V13.2.0 (hereinafter referred to as
"Reference 5")).
[0688] Although the minimum period of the SR is 5 ms in the LTE, a
period much shorter than this period may be set. For example, 2 ms
or 1 ms, etc. may be provided as a period for requesting change in
the SRS period. Consequently, the time from when the UE determines
to request changing the SRS transmission period to when the UE
transmits the request for changing the SRS transmission period can
be shortened.
[0689] Another method for notifying the SRS period change request
information will be disclosed. An uplink RS is used. The RS to be
transmitted simultaneously when the UE transmits the PUCCH or the
PUSCH in the uplink may be used. The following (1) to (3) will be
disclosed as specific examples of a method in which the RS can be
recognized as a request for changing the SRS period, unlike that
for a normal RS:
[0690] (1) setting a specific sequence number for requesting change
in the SRS period;
[0691] (2) setting a specific cyclic shift (CS) for requesting
change in the SRS period; and
[0692] (3) modulating the bits of the RS according to the presence
or absence of a request for change in the SRS period.
[0693] In the method for setting a specific sequence number for
requesting change in the SRS period in (1), a sequence number
different from that for a normal RS may be set. Consequently, the
cell can recognize whether the RS indicates the request for change
in the SRS period, based on the sequence number of the RS that has
been transmitted by the UE.
[0694] In the method for setting a specific CS for requesting
change in the SRS period in (2), a CS different from that for a
normal RS may be set. Consequently, the cell can recognize whether
the RS indicates the request for change in the SRS period, based on
the CS of the RS that has been transmitted by the UE. Since the
orthogonality is maintained between different CS s in the case of
CS, the cell can recognize whether the RS is the normal RS or
indicates the request for change in the SRS period at a lower error
rate.
[0695] In the method for modulating the bits of the RS according to
the presence or absence of a request for change in the SRS period
in (3), for example, binary phase-shift keying (BPSK) modulation
may be performed. In the presence of the request for change in the
SRS period, the bits of the normal RS are multiplied by 1. In the
absence of the request for change in the SRS period, the bits of
the normal RS are multiplied by minus 1. Upon receipt of the
modulated RS, the cell can recognize whether the RS indicates the
request for change in the SRS period.
[0696] Application of the method for notifying the request for
change in the SRS period using the uplink RS eliminates the need
for new radio resources on the frequency axis and the time axis.
Thus, the request for change in the SRS period can be made without
reducing the use efficiency of the radio resources.
[0697] The SRS may be used as an uplink RS. The methods identical
to those above may be applied even when the SRS is used.
[0698] Another method for notifying the SRS period change request
information will be disclosed. The SRS period change request
information is set as the MAC control information. The information
may be provided as a MAC control element (CE). The UE notifies the
cell of the information via the MAC signaling. Since the HARQ is
applied when the information is notified via the MAC signaling, the
cell can receive the SRS period change request information
transmitted from the UE at a lower error rate.
[0699] Yet another method for notifying the SRS period change
request information will be disclosed. The SRS period change
request information is set as the RRC information. The UE notifies
the cell of the RRC information via the RRC signaling. Since the
HARQ is applied even when the information is notified via the RRC
signaling, the cell can receive the SRS period change request
information transmitted from the UE at a lower error rate. The
application of the RRC signaling is particularly effective when the
set SRS period is longer than a duration for the notification via
the RRC signaling.
[0700] The UE may transmit a judgment indicator for the cell to
change the SRS transmission period, together with notification of
the SRS period change request information. The judgment indicators
for changing the SRS transmission period that are disclosed in the
second embodiment may be applied as the judgment indicators for the
cell to change the SRS transmission period.
[0701] Upon receipt of the SRS period change request information
from the UE, the cell starts a process of changing the setting of
the SRS transmission period for the UE. Here, the cell may
determine whether to change the SRS transmission period for the UE.
If the change is necessary, the cell may change the setting of the
SRS transmission period. If the change is unnecessary, the cell may
not change the setting of the SRS transmission period.
[0702] The cell may notify the UE that the change is not possible
on the determination whether to change the SRS transmission period.
The cell may notify the UE of a reason why the change is not
possible as well. Consequently, the cell can notify the UE that
another UE has already transmitted the SRS with the same timing, in
response to the SRS period change request from the UE. The UE can
request, from the cell, a period different from that in a previous
SRS transmission period request. Thus, the cell can maintain the
precoding performance in the communication with the UE, even when
the other UE transmits the SRS.
[0703] The UE may notify a SRS transmission offset change request
together with the SRS period change request. Alternatively, the UE
may notify the SRS transmission offset change request separately
from the SRS period change request. The SRS transmission offset
change request may be notified in the same method as that for the
SRS period change request.
[0704] Upon receipt of information on the SRS transmission offset
change request from the UE, the cell starts a process of changing
the setting of the SRS transmission offset for the UE. Here, the
cell may determine whether to change the SRS transmission offset
for the UE. If the change is necessary, the cell may change the
setting of the SRS transmission offset. If the change is
unnecessary, the cell may not change the setting of the SRS
transmission offset.
[0705] The cell may notify the UE that the change is not possible
on the determination whether to change the SRS transmission offset.
The cell may notify the UE of a reason why the change is not
possible as well. Consequently, the cell can notify the UE that
another UE has already transmitted the SRS with the same timing, in
response to the SRS offset change request from the UE. The UE can
also request, from the cell, a period different from that of the
previous SRS transmission offset request. Thus, the cell can
maintain the precoding performance in the communication with the
UE, even when the other UE transmits the SRS.
[0706] FIG. 47 illustrates an example sequence for transmitting the
SRS period change request information from the UE according to the
second modification of the second embodiment. Since the sequence
illustrated in FIG. 47 includes the same Steps as those in the
sequence illustrated in FIG. 43, the same step numbers will be
assigned to the same Steps and the common description thereof will
be omitted.
[0707] In Step ST3401, the UE transmits the SRS to the cell with
the set SRS transmission period.
[0708] In Step ST3402, the UE determines whether to transmit a SRS
period change request. The judgment indicators for changing the SRS
transmission period that are disclosed in the first embodiment may
be applied in this determination. Since the UE cannot recognize the
number of multiplexed UEs, the number of multiplexed UEs is
excluded from the judgment indicators.
[0709] When determining that transmission of the SRS period change
request is unnecessary in Step ST3402, the UE transmits the SRS
with the set SRS transmission period.
[0710] When determining that transmission of the SRS period change
request is necessary in Step ST3402, the process proceeds to Step
ST3403.
[0711] In Step ST3403, the UE transmits the SRS period change
request to the cell. The UE sets the presence of the request to the
SRS period change request information in the uplink L1/L2 control
information, and makes the notification via the L1/L2 control
signaling.
[0712] Upon receipt of the presence of the SRS period change
request from the UE in Step ST3403, the cell determines whether to
change at least one of the SRS transmission period and the SRS
transmission offset value for the UE in Step ST3404. The judgment
indicators for changing the SRS transmission period that are
disclosed in the second embodiment may be applied in this
determination.
[0713] When it is determined that at least one of the SRS
transmission period and the SRS transmission offset value needs to
be changed in Step ST3404, the process returns to Step ST3305, and
at least one of the SRS transmission period and the SRS
transmission offset value for each UE is set. At least one of the
SRS transmission period and the SRS transmission offset value may
be set in these settings by deriving how much change is necessary
using the judgment indicators for changing the SRS transmission
period.
[0714] When the cell determines that it is not necessary to change
the SRS transmission period and the SRS transmission offset value
in Step ST3404, the cell continues to receive the periodic SRS in
the same settings. Without any notification of changing or stopping
the periodic SRS, the UE continues to transmit the periodic SRS in
the same settings.
[0715] When determining not to change at least one of the SRS
transmission period and the SRS transmission offset value for the
UE in Step ST3404, the cell continues to receive the SRS with the
SRS period set to the UE.
[0716] According to the methods disclosed in the second
modification, the UE can notify the cell of information for
requesting change in the SRS transmission period. Consequently,
even if the set SRS has a long period, the UE can notify the cell
of the information for requesting change in the SRS transmission
period upon detection of fluctuations in the moving speed of its
own UE with a short period of time and sudden change in the radio
propagation environment. Thus, the cell can set, to the UE, the SRS
transmission period appropriate for the fluctuations in the moving
speed of the UE with a short period of time and appropriate for
sudden change in the radio propagation environment. The cell can
receive the SRS from the UE with the appropriate period.
Consequently, the degradation in the precoding performance for the
downlink MIMO can be reduced.
[0717] The UE may notify the cell of a request for a termination of
change in the SRS transmission period. Information for requesting a
termination of change in the SRS transmission period is provided.
Then, the UE notifies the cell of the information. The information
may be information of 1 bit. Information indicating the information
for requesting change in the SRS transmission period or the
information for requesting a termination of change in the SRS
transmission period may be provided. The information may be
information of 1 bit.
[0718] Upon receipt of information for terminating change in the
SRS transmission period from the UE, the cell terminates the
settings in which the SRS transmission period of the UE has been
changed, and restores the settings to the original settings. The
cell notifies the UE of the SRS transmission period in the original
settings. Information indicating restoration to the original
settings may be provided. The cell may notify the UE of the
information when the settings of the SRS transmission period that
have been changed for the UE are restored to the original settings.
Since there is no need to notify the SRS transmission period in the
original settings, the amount of information necessary for
communication can be reduced.
[0719] The notification methods disclosed on the information for
requesting change in the SRS transmission period may be
appropriately applied to, for example, a method for making the
notification from the UE to the cell. Consequently, the UE can
notify the cell of the desire to terminate change in the SRS
transmission period. For example, the UE notifies the cell of a
request for changing the SRS transmission period because the moving
speed of the UE becomes faster. Accordingly, the cell makes the
setting for changing the SRS transmission period. After the moving
speed is restored to its original speed, the UE requires a
termination of change in the SRS transmission period. Here, the UE
requests the cell to terminate change in the SRS transmission
period. As such, the SRS transmission period appropriate for, for
example, a state of the UE or the communication quality between the
UE and the cell can be set.
[0720] The UE may notify the cell of a request for shortening or
extending the SRS transmission period. Information for the request
for shortening or extending the SRS transmission period is
provided. Then, the UE notifies the cell of the information.
Information indicating whether the request is for shortening the
SRS transmission period or extending the SRS transmission period
may be provided. The information may be information of 1 bit.
[0721] Upon receipt of the information indicating the request for
shortening the SRS transmission period from the UE, the cell makes
the settings for shortening the SRS transmission period of the UE.
The cell notifies the UE of the set SRS transmission period. Upon
receipt of the information indicating the request for extending the
SRS transmission period from the UE, the cell makes the settings
for extending the SRS transmission period of the UE. The cell
notifies the UE of the set SRS transmission period.
[0722] The notification methods disclosed on the information for
requesting change in the SRS transmission period may be
appropriately applied to, for example, a method for making the
notification from the UE to the cell. Consequently, the UE can
notify the cell of the desire about whether to shorten or extend
the SRS transmission period. For example, the UE makes the request
for shortening the SRS transmission period when the moving speed of
the UE becomes faster. For example, the UE makes the request for
extending the SRS transmission period when the amount of remaining
battery power of the UE becomes less. As such, the SRS transmission
period appropriate for, for example, a state of the UE or the
communication quality between the UE and the cell can be set.
[0723] The UE may notify the cell of a request for stopping or
starting transmission of the SRS. Information for a request for
stopping transmission of the SRS or information for a request for
starting transmission of the SRS is provided. Then, the UE notifies
the cell of the information. Information indicating whether the
request is for stopping or starting transmission of the SRS may be
provided. The information may be information of 1 bit.
[0724] Upon receipt of the information for the request for stopping
transmission of the SRS from the UE, the cell sets the transmission
of the SRS by the UE to a stop. The cell notifies the UE of
information for stopping transmission of the SRS. The UE stops
transmitting the SRS according to the information for stopping
transmission of the SRS. Upon receipt of the information for the
request for starting transmission of the SRS from the UE, the cell
sets the transmission of the SRS by the UE to a start. The cell
notifies the UE of information for starting to transmit the SRS.
The UE starts transmitting the SRS according to the information for
starting to transmit the SRS.
[0725] The notification methods disclosed on the information for
requesting change in the SRS transmission period may be
appropriately applied to, for example, a method for making the
notification from the UE to the cell. Consequently, the UE can
notify the cell of the desire to stop or start transmission of the
SRS. Transmission of the SRS may be temporarily stopped when, for
example, the UE is still and the communication quality is stable
and superior. Here, the UE may notify the cell of a request for
stopping transmission of the SRS to request a temporary stop of the
transmission of the SRS. The transmission of the SRS needs to be
resumed when the UE starts moving and the communication quality
state is not stable. Here, the UE may notify the cell of a request
for starting transmission of the SRS to request resumption of the
transmission of the SRS. As such, the settings for stopping or
resuming the transmission of the SRS appropriate for, for example,
a state of the UE or the communication quality between the UE and
the cell can be made.
Third Modification of Second Embodiment
[0726] When the UE cannot receive information for stopping
transmission of the SRS from the cell, a problem of continuing to
transmit the SRS while failing to stop the transmission of the SRS
may arise.
[0727] For example, in the case where the cell transmits
information for stopping transmission of the SRS and information
for starting the transmission of the SRS with separate timings, if
the UE cannot receive the information for stopping the transmission
of the SRS, the transmission of the SRS that has been started
according to the information for starting the transmission of the
SRS cannot be stopped. Then, the problem that the UE continues to
transmit the SRS will occur.
[0728] The maximum transmission time may be provided as a method
for solving such a problem. The cell notifies the UE of the maximum
transmission time. After starting to transmit the SRS according to
the information for starting the transmission of the SRS, the UE
stops transmitting the SRS after a lapse of the maximum
transmission time. Consequently, the problem for the UE which
continues to transmit the SRS while failing to stop the
transmission of the SRS can be solved.
[0729] The timer of the UE may manage the maximum transmission
time. The UE starts the timer with the start timing according to
the information for starting to transmit the SRS. The information
for starting to transmit the SRS includes SRS transmission starting
information and SRS transmission offset information. The timer may
be started in consideration of the offset information if the offset
information is present.
[0730] Alternatively, the UE starts the timer with the timing to
start transmitting the SRS, when starting to transmit the periodic
SRS with notification of the SRS transmission period to the UE. As
such, the timer may be started with the timing for the UE to start
the transmission of the SRS.
[0731] The UE stops transmitting the SRS after a lapse of the
maximum transmission time since starting of the timer, regardless
of reception of the information for stopping transmission of the
SRS. The UE resets the timer simultaneously with stopping of the
transmission of the SRS. Consequently, the transmission of the SRS
can be stopped after a lapse of the maximum transmission time since
start of the first transmission of the SRS.
[0732] Here, receipt of the information for stopping transmission
of the SRS before the lapse of the maximum transmission time since
start of the first transmission of the SRS may cause a problem. The
timer will not be reset even if the UE stops transmitting the SRS
upon receipt of the information for stopping transmission of the
SRS. When the UE receives information for starting to transmit the
next SRS or information on the SRS transmission period before the
lapse of the maximum transmission time, the UE starts transmitting
the SRS according to these pieces of information.
[0733] Such a case may cause the UE to stop transmitting the SRS
because the maximum transmission time will elapse soon after the UE
starts transmitting the SRS. As a method for solving such a
problem, the timer may be reset when the UE receives the
information for stopping the transmission of the SRS before the
lapse of the maximum transmission time since start of the first
transmission of the SRS. Alternatively, the timer may be reset when
the UE stops transmitting the SRS.
[0734] Consequently, a problem of stopping the transmission of the
SRS soon after start of the second transmission of the SRS onward
can be avoided.
[0735] The maximum transmission duration may be statically
predetermined in, for example, a standard. The cell may
semi-statically or dynamically notify the UE of information on the
maximum transmission duration. The information on the maximum
transmission duration may be notified via the RRC signaling.
Alternatively, the information on the maximum transmission duration
may be notified via the L1/L2 control signal. Alternatively, the
information on the maximum transmission duration may be notified
via the MAC signaling.
[0736] The maximum transmission duration may be set for each cell.
The complexity in the control can be avoided. The maximum
transmission duration may be set for each beam as an alternative
method. For example, a coverage to be provided for each beam
differs. Here, setting a different value to each beam can give
flexibility to the structure of the beam. The maximum transmission
duration may be set for each UE as an alternative method. Since the
value for each UE can be set, the maximum transmission duration can
be set according to a state of the UE, for example, the capability
of the UE or a service through which the UE is communicating,
etc.
[0737] The maximum transmission duration is measured in time in the
aforementioned method. Managing the maximum transmission duration
by the timer is disclosed. The maximum number of transmissions of
the SRS may be provided as an alternative method. The cell notifies
the UE of the maximum number of transmissions. Once starting to
transmit the SRS, the UE stops transmitting the SRS after
transmitting the SRS the maximum number of times. The number of
transmissions is reset when the UE stops transmitting the SRS.
[0738] Consequently, the same advantages as those in setting the
maximum transmission duration can be produced. For example, the
transmission period of the SRS may be set according to a state of
the UE, as in the specific examples of the judgment indicators for
changing the SRS transmission period that are disclosed in the
second embodiment. Here, application of the maximum transmission
duration requires setting of a different maximum transmission
duration for each UE, which complicates the control. However,
application of, for example, the maximum number of transmissions
enables setting of the maximum transmission duration according to
the SRS transmission period, even when the SRS transmission periods
differ.
Third Embodiment
[0739] In the LTE, the PUCCH to which an uplink control signal such
as Ack/Nack, CQI/CSI, or SR is mapped is mapped to all symbols in
one subframe. The SRS is transmitted in the last one symbol in one
subframe (see Reference 4).
[0740] When one UE has a conflict in transmission timing between
Ack/Nack and the SRS, the last symbol of the PUCCH to which
Ack/Nack is mapped and in which the conflict with the SRS occurs is
punctured to perform transmission. Among 14 symbols (including the
RS) of the PUCCHs in one subframe, only the last symbol is
punctured, and the other symbols are transmitted.
[0741] FIG. 48 illustrates the conflict in transmission timing
between Ack/Nack and the SRS in the LTE. In FIG. 48, the horizontal
axis represents time t, and the vertical axis represents a
frequency f. FIG. 48 illustrates an uplink subframe that consists
of 14 symbols. The PUCCHs are mapped to both ends of the system
bandwidth per resource block (RB), and the PUSCHs are mapped
between the ends. Although FIG. 48 omits the illustration of the
RS, the RS is mapped to predefined symbols in areas to which the
PUCCHs are mapped and in areas to which the PUSCHs are mapped.
[0742] The SRS is set to the last symbol of one subframe. The PUSCH
is not mapped to the last symbol in the subframe to which the SRS
is set. When transmission of the SRS and the PUCCH is set within
the same subframe of a UE, the UE punctures the last symbol of the
PUCCH in the subframe to perform transmission. In other words, the
UE does not transmit the PUCCH in the last symbol of the subframe.
The UE transmits the SRS in the subframe with a predefined
resource.
[0743] A signal to which such a method is applied is uplink
Ack/Nack for the downlink data. Ack/Nack consists of 1 bit or 2
bits, and is spread and mapped to the PUCCH. Among 14 symbols
(including the RS) of the PUCCHs in one subframe, only the last
symbol is punctured, and the other symbols are transmitted. Thus,
the cell can recognize Ack/Nack upon receipt of the PUCCHs in the
other symbols that have been transmitted.
[0744] Consequently, even if transmission of Ack/Nack conflicts
with transmission of the SRS in the same subframe, the UE can
transmit both the Ack/Nack and the SRS, and the eNB can receive
both the Ack/Nack and the SRS from the UE in the same subframe.
[0745] On the other hand, not mapping an uplink control signal such
as Ack/Nack to all symbols in one subframe but mapping the uplink
control signal to a symbol at the end of the subframe are proposed
as a subframe structure in the NR. Transmitting the SRS in a symbol
at the end of the one subframe is also proposed. For example, a
proposal is made on transmitting, in a self-contained subframe, the
uplink control signal such as Ack/Nack and the SRS in the last one
symbol in a subframe (see Non-Patent Document 9 and 3GPP R1-167203
(hereinafter referred to as "Reference 6")).
[0746] When one UE has a conflict in transmission timing between an
uplink control signal such as Ack/Nack and the SRS, puncturing the
last symbol to which the uplink control signal such as Ack/Nack is
mapped to prevent transmission in the last symbol as according to
the conventional method in the LTE causes a problem of failing to
transmit the uplink control signal such as Ack/Nack.
[0747] The uplink control signal such as Ack/Nack is transmitted
not in the other symbols but only in the last symbol in one
subframe. Thus, if the last symbol is punctured, the uplink control
signal such as Ack/Nack that is mapped only to the last symbol in
which a conflict with the SRS occurs is not transmitted, which is
the cause of the problem.
[0748] The third embodiment will disclose a method for solving such
a problem.
[0749] The uplink control signal is frequency-division multiplexed
with the SRS in the same symbol. The uplink control signal such as
Ack/Nack is transmitted in a symbol in which the SRS is
transmitted. An uplink control signal, and a SRS of a UE different
from the UE that transmits the uplink control signal may be
transmitted in the same symbol. An uplink control signal, and a SRS
of a UE identical to the UE that transmits the uplink control
signal may be transmitted in the same symbol.
[0750] Flexible scheduling for the uplink control signal in the
frequency axis direction is possible to frequency-division
multiplex the uplink control signal with the SRS in the same
symbol. The uplink control signal may be allocated to the frequency
resources different from those for the other information to be
mapped in the same subframe for its own UE. Examples of the other
information to be mapped in the same subframe for its own UE
include downlink data, downlink control information, and uplink
data. The allocation methods include a method for allocating
consecutive sub-carriers in a frequency range and a method for
allocating distributed sub-carriers in a frequency range.
[0751] The uplink control signal may be allocated to the frequency
resources that are not scheduled for the other UEs. Since the
multiplexing with the other UEs is unnecessary, the reception error
rate in the cell can be reduced. The complexity caused by control
for the multiplexing can be reduced.
[0752] The uplink control signal may be allocated to the frequency
resources that are scheduled for the other UEs. Here, the
multiplexing with the other UEs is performed. The multiplexing
method using the same frequency resources among a plurality of UEs
may be code-multiplexing. The code-multiplexing is multiplexing
using a code orthogonal between the UEs. Alternatively, the
multiplexing may be performed using a scrambling code between the
UEs. Consequently, the uplink control signal can be multiplexed
with an uplink control signal or uplink information of another UE.
Thus, flexible scheduling for the uplink control signal in the
frequency axis direction is possible.
[0753] The cell includes, in the L1/L2 control information,
scheduling information including information for allocation to the
frequency resources and a multiplexing method, and transmits the
L1/L2 control information to the UE via the L1/L2 control
signaling. The scheduling information may be notified in the same
subframe or in a different subframe. When the scheduling
information is notified in the different subframe, information
indicating which subframe is scheduled may be notified
together.
[0754] Consequently, the uplink control signal can be allocated to
the frequency resources different from those for the other
information to be mapped in the same subframe. Although the
Description may omit the description on the RS to be transmitted in
association with the uplink control signal, the RS to be
transmitted in association with the uplink control signal is
transmitted in association with the uplink control signal,
similarly as the uplink control signal.
[0755] When the uplink control signal is frequency-division
multiplexed with the SRS in the same symbol, the cell may allocate
the frequency resources to which the SRS to be actually transmitted
in the symbol is not set, as the frequency resources for the uplink
control signal. The cell notifies, according to the aforementioned
method, the UE of the scheduling information on the frequency
resources for the uplink control signal.
[0756] FIG. 49 illustrates one example of frequency-division
multiplexing the uplink control signal with the SRS in the same
symbol and transmitting the resulting signal according to the third
embodiment. In FIG. 49, the horizontal axis represents time t, and
the vertical axis represents a frequency f. 1 subframe consists of
14 symbols. The downlink L1/L2 control information is mapped to the
first three symbols in the one subframe. The last symbol of the one
subframe is set as a symbol in which the SRS can be transmitted. In
FIG. 49, diagonal-hatched solid lines that descend to the left
represent the SRS to be actually transmitted in the symbol.
[0757] A self-contained subframe is structured in a frequency range
"a" for a UE #a. For the UE #a, the DL data is mapped to the fourth
symbol to the tenth symbol in the one subframe, and gaps are
arranged from the 11th symbol to the 13th symbol of the one
subframe. FIG. 49 illustrates the case where the uplink control
signal is Ack/Nack.
[0758] In a conventional self-contained subframe, an Ack/Nack
signal for the downlink data is transmitted in the last symbol of
one subframe. Since the last symbol of the subframe is set as a
symbol in which the SRS can be transmitted, the symbol may have a
conflict with transmission of the SRS. For example, when a subframe
in which the SRS of another UE is to be actually transmitted is set
to the subframe, the SRS of the other UE is transmitted in the last
symbol of the subframe. Alternatively, when a subframe in which the
SRS of its own UE is to be actually transmitted is set to the
subframe, the SRS of its own UE is transmitted in the last symbol
of the subframe.
[0759] Here, without any ingenuity, transmission of Ack/Nack of its
own UE conflicts with transmission of the SRS of another UE or its
own UE, and the cell cannot accurately receive these
transmissions.
[0760] As illustrated in FIG. 49, an Ack/Nack signal for the
downlink data is frequency-division multiplexed with the SRS in the
last symbol of one subframe for transmission of the resulting
signal according to the third embodiment. The cell allocates, to
the Ack/Nack signal for the downlink data, frequency resources
different from frequency resources with which the SRS is to be
actually transmitted. The frequency resources different from the
frequency resources with which the SRS is to be actually
transmitted may be different from the frequency resources to which
the DL data of its own UE is mapped. In the example illustrated in
FIG. 49, the frequency resources in a frequency range b are
allocated to the Ack/Nack signal.
[0761] The scheduling information for Ack/Nack is included in the
L1/L2 control information for the UE #a, and is transmitted via the
L1/L2 control signaling. The UE receives the L1/L2 control
signaling to receive the L1/L2 control information addressed to its
own UE, thus obtaining the allocation information on the frequency
resources for Ack/Nack in response to the downlink data.
Consequently, the UE can transmit the Ack/Nack in response to the
downlink data without conflicting with the SRS.
[0762] Even when the SRS that is to be actually transmitted in the
subframe in which the UE #a has received the DL data is set,
Ack/Nack in response to the DL data can be transmitted in the same
subframe in which the DL data has been received.
[0763] FIG. 50 illustrates another example of frequency-division
multiplexing the uplink control signal with the SRS in the same
symbol and transmitting the resulting signal according to the third
embodiment. In FIG. 50, the horizontal axis represents time t, and
the vertical axis represents a frequency f. Since FIG. 50 is
similar to FIG. 49, the differences will be mainly described, and
the common description will be omitted.
[0764] An Ack/Nack signal for the downlink data is
frequency-division multiplexed with the SRS in the last symbol of
one subframe for transmission of the resulting signal. The cell
allocates, to the Ack/Nack signal for the downlink data,
distributed frequency resources different from those of the SRS
that is to be actually transmitted. In the example illustrated in
FIG. 50, the distributed frequency resources in the frequency range
b are allocated to the Ack/Nack signal. This may be applied when
the SRS that is to be actually transmitted is transmitted with the
distributed frequency resources. Consequently, this can increase
the use efficiency of the radio resources.
[0765] FIG. 51 illustrates another example of frequency-division
multiplexing the uplink control signal with the SRS in the same
symbol and transmitting the resulting signal according to the third
embodiment. In FIG. 51, the horizontal axis represents time t, and
the vertical axis represents a frequency f. Since FIG. 51 is
similar to FIG. 50, the differences will be mainly described, and
the common description will be omitted.
[0766] An Ack/Nack signal for the downlink data is
frequency-division multiplexed with the SRS in the last symbol of
one subframe for transmission of the resulting signal. The cell
allocates, to the Ack/Nack signal for the downlink data, the
distributed frequency resources different from those of the SRS
that is to be actually transmitted. The frequency resources with
which Ack/Nack is transmitted are a part of frequency resources to
which the DL data of its own UE is mapped. In the example
illustrated in FIG. 51, the distributed frequency resources in the
frequency range "a" are allocated to the Ack/Nack signal. This may
be applied when the SRS that is to be actually transmitted is
transmitted with the distributed frequency resources. Consequently,
this can increase the use efficiency of the radio resources.
[0767] Here, the frequency resources with which Ack/Nack is
transmitted may be less than predefined frequency resources. In the
example illustrated in FIG. 51, although the predefined frequency
resources are equal to the frequency resources to which the DL data
of its own UE is mapped, the frequency resources with which
Ack/Nack is transmitted are half the predefined frequency
resources. Here, the transmission power of the frequency resources
with which Ack/Nack is transmitted may be increased. Increasing the
transmission power will increase the received power of the cell.
Thus, even when the frequency resources with which Ack/Nack is
transmitted are less than the predefined frequency resources, the
cell can receive an Ack/Nack signal from the UE at a lower error
rate.
[0768] Information indicating increase in the transmission power of
the frequency resources is included in the L1/L2 control
information as scheduling information, and transmitted to the UE
via the L1/L2 control signaling. The information may be included in
the scheduling information together with the information for
allocation to the frequency resources and a multiplexing method.
The scheduling information may be notified in the same subframe or
in a different subframe. When the scheduling information is
notified in the different subframe, information indicating which
subframe is scheduled may be notified together.
[0769] As an alternative method, information indicating a method
for increasing the transmission power of the frequency resources
may be included in broadcast information to be broadcast. The
method for increasing the transmission power of the frequency
resources may be determined for each cell to be broadcast.
Alternatively, the method for increasing the transmission power of
the frequency resources may be determined for each cell, and
notified to each UE individually via the RRC-dedicated signaling.
Alternatively, the method for increasing the transmission power of
the frequency resources may be determined for each UE individually,
and notified to each of the UEs individually via the RRC-dedicated
signaling.
[0770] As an alternative method, the method for increasing the
transmission power of the frequency resources may be statically
predetermined in, for example, a standard. The cell may notify the
UE of only a parameter required for the method for increasing the
transmission power of the frequency resources. The methods
previously described may be applied to the notification method
[0771] Increasing the transmission power of the radio resources
with which Ack/Nack is transmitted can reduce the radio resources
with which Ack/Nack is transmitted. The radio resources to be used
can be reduced, and many UEs can be supported even when at least
one of the followings occurs in the same symbol: increase in the
number of UEs to which the SRS to be actually transmitted is set;
and increase in the number of UEs that transmit the uplink control
signal.
[0772] Application of the methods disclosed in the third embodiment
enables transmission of an uplink control signal such as Ack/Nack
and the SRS in the NR even when these signals conflict with each
other in the same subframe. Thus, the cell can receive the uplink
control signal such as Ack/Nack and the SRS with predefined timing.
Enabling reception of the Ack/Nack with the predefined timing
allows the cell to perform retransmission control without any
latency. Enabling reception of the SRS with the predefined timing
allows the cell to perform precoding with high precision.
[0773] Although the conflict between the uplink control signal and
the SRS in the last one symbol in one subframe is disclosed, the
uplink control signal and the SRS may be mapped to the other
symbols in the one subframe. When the uplink control signal and the
SRS conflict with each other in the other symbols, the methods
disclosed in the third embodiment such as the
frequency-multiplexing may be performed in the other symbols. Even
in such a case, the same advantages as those according to the third
embodiment can be produced.
[0774] Although what is disclosed is that the uplink control signal
and the SRS are mapped to the same symbol in one subframe and
conflict with each other, the uplink control signal and the SRS may
be mapped separately to symbols with different symbol numbers. Even
when the uplink control signal and the SRS conflict with each other
in a part of the symbols, the methods disclosed in the third
embodiment such as the frequency-multiplexing may be similarly
applied to the symbols in which the conflict has occurred. Even in
such a case, the same advantages as those according to the third
embodiment can be produced.
[0775] Although what is disclosed is that the uplink control signal
and the SRS are mapped to the same symbol in one subframe and
conflict with each other, the uplink control signal and the SRS may
be mapped separately to symbols with different symbol numbers.
Here, when the uplink control signal and the SRS conflict with each
other in a part of the symbols, all the symbols to which the uplink
control signal is mapped may be transmitted with the frequency
resources with which the SRS is not actually transmitted. The
methods disclosed in the third embodiment may be appropriately
applied to all the symbols to which the uplink control signal is
mapped and including the symbols in which the conflict has
occurred. Even in such a case, the same advantages as those
according to the third embodiment can be produced.
[0776] Transmissions of different uplink control signals may
conflict with each other in the same subframe in the same UE. The
methods disclosed in the third embodiment may be appropriately
applied to the conflict of transmissions of different uplink
control signals in one symbol or a part of the symbols in the same
subframe. For example, when transmissions of Ack/Nack and CQI/CSI
conflict with each other in the same symbol in the same subframe in
a UE, the UE transmits the CQI/CSI without changing the radio
resources for transmitting the CQI/CSI, and allocates the Ack/Nack
to the other frequency resources to transmit the Ack/Nack.
[0777] Consequently, even if the Ack/Nack and the CQI/CSI conflict
with each other in one symbol or a part of the symbols in the same
subframe, the UE can transmit both of the signals in the same
subframe. The cell can receive both of the signals in the same
subframe.
[0778] Among the uplink control signals, information on which
signal is transmitted without changing the radio resources and on
which signal is allocated to the other frequency resources to be
transmitted may be statically predetermined in a standard.
Alternatively, the cell may include the information in broadcast
information and broadcast the broadcast information. Consequently,
the information can be determined for each cell in consideration of
a state of each of the cells. Alternatively, the cell may
separately notify each UE of the information via the RRC-dedicated
signaling. The information may be determined for each cell or for
each UE. Consequently, the information can be determined for each
UE in consideration of a state of each of the UEs.
[0779] Alternatively, the information may be notified via the MAC
signaling when it is notified to each UE. The MAC signaling can
make the setting earlier than that via the RRC signaling.
Alternatively, the information may be included in the L1/L2 control
information to be notified via the L1/L2 control signaling. The
L1/L2 control signaling can make the setting much earlier than that
via the RRC signaling. When the information is included in the
L1/L2 control information, it may be included in the scheduling
information together with the information for allocation to the
frequency resources and a multiplexing method.
[0780] The number of uplink control signals is not limited to two,
but may be three or more. One uplink control signal may be
transmitted without changing the radio resources, and two uplink
control signals may be allocated to the other frequency resources
to be transmitted. Methods similar to the aforementioned methods
may be applied thereto.
[0781] Consequently, even if different uplink control signals
conflict with each other in one symbol or a part of the symbols in
the same subframe, the UE can transmit both of the signals in the
same subframe. The cell can receive both of the signals in the same
subframe.
[0782] Since the cell can receive information from the UE in a
predefined subframe, the cell can timely control the UE. For
example, the cell can perform retransmission control using Ack/Nack
without any latency. For example, the cell can execute precoding
for the downlink MIMO using CQI/CSI with high precision.
Alternatively, the cell can start the uplink communication early by
making an early uplink scheduling request using a SR.
First Modification of Third Embodiment
[0783] The first modification will disclose another method for
solving the problems disclosed in the third embodiment.
[0784] When the uplink control signal such as Ack/Nack conflicts
with the SRS, the uplink control signal is time-division
multiplexed with the SRS. When the uplink control signal such as
Ack/Nack conflicts with the SRS, the number of UL symbols in the
same subframe may be increased. The number of UL symbols is
increased, the uplink control signal is mapped to the increased UL
resources, and the uplink control signal is time-division
multiplexed with the SRS.
[0785] The number of UL symbols to be increased is not limited to
one, but may be two or more. The number of UL symbols to be
increased may be set according to the number of symbols to which
the uplink control signal is mapped. The UL symbols to be increased
may be set to be consecutive with the existing UL symbols. When the
UL symbols to be increased are discretely set, for example, when a
DL symbol exists between the UL symbols that are discretely set, a
gap needs to be newly provided, which will decrease the use
efficiency of the radio resources. When a gap exists between the UL
symbols that are discretely set, a new gap sometimes needs to be
provided between the DL symbol and the forward UL symbol to
maintain a predefined duration, which will decrease the use
efficiency of the radio resources.
[0786] The time-division multiplexing method is, for example, while
placing the SRS in the last symbol without any change from the
normal setting, mapping the uplink control signal such as Ack/Nack
to a symbol immediately preceding that of the SRS. Since not only
the SRS of the conflicting UE but also the SRS of another UE are to
be transmitted, no change from the normal setting of the SRS saves,
for example, a process of changing the setting into that for the
other UE. This can avoid complexity in the control.
[0787] The number of symbols in one subframe is predetermined.
Thus, when the number of uplink symbols is increased by one symbol
for the uplink control signal, the other symbols needs to be
reduced. The following (1) to (3) will be disclosed as specific
examples of the reduction method:
[0788] (1) the number of gap symbols is reduced;
[0789] (2) the number of DL symbols is reduced; and
[0790] (3) a combination of (1) and (2) above.
[0791] Since the number of gap symbols is reduced in (1), the
number of symbols for data can be maintained. Thus, reduction in
the data transmission rate can be suppressed. This is effective
when suppressing reduction in the data transmission rate is
desired. Since the number of DL symbols is reduced in (2), the
number of gap symbols can be maintained. Since the number of gap
symbols is determined from, for example, the cell coverage and the
demodulation performance of the UE, the number of gap symbols may
be desirably fixed. The method is effective in such a case. In (3),
for example, when the number of uplink symbols is increased by two
or more symbols, the data transmission rate and the number of gap
symbols can be maintained to a certain extent.
[0792] The cell and the UE may switch (1) to (3) above to use them.
The cell may notify the UE of the switching via the RRC signaling,
the MAC signaling, or the L1/L2 signaling. For example, when the UE
moves from a boundary of a cell to a neighborhood of the cell and
the number of gap symbols may be reduced due to less propagation
time, switching from (2) to (1) above can maintain the data
transmission rate.
[0793] FIG. 52 illustrate one example of increasing the number of
UL symbols by one symbol and time-division multiplexing Ack/Nack
with the SRS. In FIG. 52, the horizontal axis represents time t,
and the vertical axis represents a frequency f. Since FIG. 52 is
similar to FIG. 49, the differences will be mainly described, and
the common description will be omitted.
[0794] When an uplink control signal such as Ack/Nack conflicts
with the SRS in the last symbol in the same subframe, the second
symbol from the end of the subframe in which a gap is formed is
configured as the UL symbol. The SRS is mapped to the last symbol
without being changed from the normal setting. The Ack/Nack is
mapped to the second symbol from the end of the subframe which is
configured as the UL symbol.
[0795] The gap may be formed as the UL symbol only for the
frequency resources that are scheduled for the UE having a conflict
between the Ack/Nack and the SRS. Alternatively, when at least one
UE has a conflict between the Ack/Nack and the SRS, the gap may be
formed as the UL symbol over the entire bandwidth.
[0796] Since the Ack/Nack and the SRS are mapped to the different
symbols, the UE can transmit the Ack/Nack and the SRS in the same
subframe. The cell can receive the Ack/Nack and the SRS from the UE
in the same subframe.
[0797] FIG. 53 illustrate another example of increasing the number
of UL symbols by one symbol and time-division multiplexing Ack/Nack
with the SRS. In FIG. 53, the horizontal axis represents time t,
and the vertical axis represents a frequency f. Since FIG. 53 is
similar to FIG. 52, the differences will be mainly described, and
the common description will be omitted.
[0798] When an uplink control signal such as Ack/Nack conflicts
with the SRS in the last symbol in the same subframe, the second
symbol from the end of the subframe in which a gap is formed is
configured as the UL symbol, and the last symbol in which the DL
data is formed is configured as a gap. In other words, 3 symbols
for gap are maintained, the last one symbol for the DL data is
eliminated, and one UL symbol is increased in the second symbol
from the end of the subframe.
[0799] Such a configuration may be intended only for the frequency
resources that are scheduled for the UE having a conflict between
the Ack/Nack and the SRS. Alternatively, such a configuration may
be intended for all the UEs in the same subframe when at least one
of the UEs has a conflict between the Ack/Nack and the SRS.
[0800] Since the Ack/Nack and the SRS are mapped to the different
symbols, the UE can transmit the Ack/Nack and the SRS in the same
subframe. The cell can receive the Ack/Nack and the SRS from the UE
in the same subframe.
[0801] Information indicating how the uplink control signal is
time-division multiplexed with the SRS (hereinafter may be referred
to as "information on time-division multiplexing") may be provided.
The following (1) to (8) will be disclosed as specific examples of
the information on time-division multiplexing:
[0802] (1) the number of UL symbols to be increased;
[0803] (2) the symbol number in which each uplink control signal is
mapped;
[0804] (3) information on which signal is transmitted without
changing the radio resources and on which signal is allocated to
the increased UL resources to be transmitted;
[0805] (4) information indicating whether the number of gap symbols
or the number of DL symbols is reduced;
[0806] (5) the number of gaps after reducing the gaps;
[0807] (6) the number of DL symbols after reducing the DL
symbols;
[0808] (7) the symbol numbers of the respective UL symbol to be
increased; and
[0809] (8) combinations of (1) to (7) above.
[0810] When the uplink control signal such as Ack/Nack conflicts
with the SRS, the uplink control signal can be time-division
multiplexed with the SRS by setting the information on
time-division multiplexing.
[0811] When the symbol in which the SRS is transmitted and the
uplink control signal are time-division multiplexed, information
indicating a position relationship between the symbol in which the
SRS is transmitted and the uplink control signal may be provided.
For example, information indicating whether the SRS transmission
symbol is placed consecutively with the symbol to which the uplink
control signal is mapped may be provided. When the symbols are
arranged consecutively, a signal for which the radio resources are
changed is mapped consecutively with a signal for which the radio
resources are not changed. When the symbols are not arranged
consecutively, information for identifying a symbol to which the
signal for which the radio resources are not changed is mapped is
notified.
[0812] The cell notifies the UE of the information indicating the
position relationship. When the symbols are arranged consecutively,
a symbol to which the signal for which the radio resources are
changed is mapped may be derived without using the information on
time-division multiplexing. Here, the cell does not need to notify
the UE of the information on time-division multiplexing, and can
reduce the amount of information required for the notification.
[0813] The information indicating the position relationship may be
included in the information on time-division multiplexing. Setting
the information indicating the position relationship in combination
with the information on time-division multiplexing enables flexible
setting of the symbols in which the uplink control signal is
time-division multiplexed with the SRS.
[0814] The information on time-division multiplexing may be
statically predetermined in, for example, a standard. Consequently,
both the eNB and the UE can recognize the information. This
eliminates the need for signaling for notification between nodes,
and can reduce the signaling load.
[0815] Alternatively, the eNB may set the information on
time-division multiplexing, and notify it to the UE. The
information may be set for each cell or individually to each UE.
The eNB may include the information in the L1/L2 control
information, and notify the UE of the information via the L1/L2
control signaling. The information may be included in the L1/L2
control information together with the other scheduling information
for the UE and notified via the L1/L2 control signaling. Methods
similar to those disclosed in the third embodiment may be applied
thereto.
[0816] Notification of the information via the L1/L2 control
signaling can make the setting earlier. Thus, a method for
time-division multiplexing the uplink control signal with the SRS
can be supported earlier according to, for example, time
fluctuations in a radio propagation situation or change in the
speed of the UE.
[0817] The eNB may notify the UE of the information via the MAC
signaling. The reception error rate can be reduced with application
of the retransmission control. Alternatively, the information may
be notified via the RRC signaling. When the information is set for
each cell, it may be included in the broadcast information to be
broadcast. Alternatively, the information may be notified to each
UE via the RRC-dedicated signaling. When the information is set
individually to each UE, it may be notified to each of the UEs via
the RRC-dedicated signaling. When the information is notified via
the RRC signaling, it may be notified together with the
configuration information of the SRS. This can reduce the signaling
load.
[0818] Application of the methods disclosed in the third embodiment
enables transmission of both of the uplink control signal such as
Ack/Nack and the SRS in the NR even when these signals conflict
with each other in the same subframe. Thus, the cell can receive
the uplink control signal such as Ack/Nack and the SRS with
predefined timing. Enabling reception of Ack/Nack with the
predefined timing allows the cell to perform retransmission control
without any latency. Enabling reception of the SRS with the
predefined timing allows the cell to perform precoding with high
precision.
[0819] Since there is no need to separately set the frequency
resources in addition to those for the normal SRS as disclosed in
the third embodiment, the required frequency resources can be
reduced. Since a conflict with the resources in which the
information for the other UEs is scheduled can be avoided,
complexity in the control can also be avoided.
[0820] Although the conflict between the uplink control signal and
the SRS in the last one symbol in one subframe is disclosed, the
uplink control signal and the SRS may be mapped to the other
symbols in the one subframe. The methods disclosed in the first
modification such as the time-division multiplexing may be applied
similarly when the uplink control signal and the SRS conflict with
each other in the other symbols. Even in such a case, the same
advantages as those according to the first modification can be
produced.
[0821] Although the conflict between the uplink control signal and
the SRS in the same symbol in one subframe is disclosed, the uplink
control signal and the SRS may be mapped separately to symbols with
different symbol numbers. Even when the uplink control signal and
the SRS conflict with each other in a part of the symbols, the
methods disclosed in the first modification such as the
time-division multiplexing may be similarly applied to the symbols
in which the conflict has occurred. Even in such a case, the same
advantages as those according to the first modification can be
produced.
[0822] Transmissions of different uplink control signals may
conflict with each other in the same subframe in the same UE. The
methods disclosed in the first modification may be appropriately
applied to the conflict of transmissions of different uplink
control signals in one symbol or a part of the symbols in the same
subframe. For example, when transmissions of Ack/Nack and CQI/CSI
conflict with each other in the same symbol in the same subframe in
a UE, the number of UL symbols will be increased, and the UE
transmits the CQI/CSI without changing the radio resources for
transmitting the CQI/CSI, and allocates the Ack/Nack to the
increased UL symbols to transmit the Ack/Nack.
[0823] Consequently, even if the Ack/Nack and the CQI/CSI conflict
with each other in one symbol or a part of the symbols in the same
subframe, the UE can transmit both of the signals in the same
subframe. The cell can receive both of the signals in the same
subframe. When the symbol of the CQI/CSI is placed prior to the
symbol of the Ack/Nack, a response to the Ack/Nack for the downlink
data can be transmitted in the same subframe in a self-contained
subframe.
[0824] The number of uplink control signals is not limited to two,
but may be three or more. One uplink control signal may be
transmitted without changing the radio resources, and two uplink
control signals may be allocated to the increased UL symbols to be
transmitted. Methods similar to the aforementioned methods may be
applied thereto.
[0825] Consequently, even if different uplink control signals
conflict with each other in one symbol or a part of the symbols in
the same subframe, the UE can transmit both of the signals in the
same subframe. The cell can receive both of the signals in the same
subframe.
[0826] Since the cell can receive information from the UE in a
predefined subframe, the cell can timely control the UE. For
example, the cell can perform retransmission control using Ack/Nack
without any latency. For example, the cell can execute precoding
for the downlink MIMO using CQI/CSI with high precision.
Alternatively, the cell can start the uplink communication early by
making an early uplink scheduling request using a SR.
[0827] According to the disclosed methods, when the uplink control
signal such as Ack/Nack conflicts with the SRS, the number of UL
symbols in the same subframe is increased, the uplink control
signal is mapped to the increased UL resources, and the uplink
control signal is time-division multiplexed with the SRS. An
alternative method when the other UL symbols exist in the same
subframe may be mapping an uplink control signal to the existing UL
symbols without increasing the number of UL symbols. When such a
conflict does not occur and the UL information is mapped to the
existing UL symbols, the UL information may be reduced, and an
uplink control signal may be mapped to the existing UL symbols. The
UL information may be, for example, UL user data. Even in such a
case, the same advantages as those according to the first
modification can be produced.
[0828] When the existing UL symbols are used without increasing the
number of UL symbols, the "UL symbols to be increased" in the
specific examples of the information on time-division multiplexing
may be read as the "UL symbols in which the other UL information is
to be reduced". The same holds true for the UL symbols to which the
other UL information is not mapped.
[0829] When a UE has a conflict between a SRS symbol and an uplink
control signal, the SRS symbol may be moved forward, and a SRS
symbol of another UE to be transmitted in the subframe may also be
moved forward. The SRS transmission symbol of a UE may be identical
to that of another UE. The cell notifies the other UE to move the
SRS forward by symbols of the uplink control signal. This
notification may be made via the L1/L2 control signaling.
[0830] Here, when the number of symbols to which the uplink control
signal is mapped is different for each UE, the number of symbols of
the uplink control signal has to be notified individually to each
of the UEs, which will complicate the control. The maximum number
of symbols to be used for the uplink control signal may be notified
to solve such a problem. The maximum number of symbols for the
uplink control signal is notified to the UE whose number of symbols
for the uplink control signal is fewer than the maximum number of
symbols. Consequently, the same number of symbols for the uplink
control signal has only to be notified to UEs. This can avoid
complexity in the control.
[0831] As an alternative method, the number of symbols to which the
uplink control signal is mapped may be set for each cell. The cell
notifies, via the RRC, the UE of the symbols to which the uplink
control signal is mapped for each cell. Consequently, the cell has
only to notify, via the L1/L2 control signaling, the UE to move the
SRS forward. Information indicating moving the SRS forward may be
provided, and the cell may notify the UE of the information. There
is no need to notify by how many symbols the SRS should be moved
forward.
[0832] Although disclosed is setting, for each cell, the number of
symbols to which uplink control signal is mapped, the number of
symbols may be set not for each cell but for each numerology.
Alternatively, the number of symbols may be set for each frequency
bandwidth to which the same numerology is applied. Alternatively,
the number of symbols may be set for each UE with the same
numerology.
[0833] Examples of the numerology to be set include a symbol time
interval and a sub-carrier spacing. The 3GGP proposes setting
different numerologies in the same cell. The different settings
vary the symbol timing and the frequency bandwidth of the SRS.
Here, the setting for each numerology can avoid complexity
therein.
[0834] Setting the numerology for each UE with the same service,
for each UE of the same type, or for each UE with the same
capability can also avoid complexity therein.
[0835] Prevention of transmission of the SRS in the SRS
transmission symbol may be set to another UE that does not transmit
the SRS in the SRS transmission symbol. The UE that transmits the
SRS in the SRS transmission symbol may set, in an RB in which the
SRS is transmitted, prevention of transmission of the SRS in the
SRS transmission symbol to another UE for which an uplink channel
or an uplink signal is scheduled. The cell may notify the UE of
such a setting via the L1/L2 control signaling.
[0836] Consequently, the interference with the UE that transmits
the SRS can be reduced.
[0837] Although information on the UL symbols to be increased and
the UL symbols in which the other UL information is reduced is
disclosed as the information on time-division multiplexing, these
pieces of information are information on the symbols in which the
SRS is to be transmitted.
[0838] The eNB may notify the UE of not only information on the SRS
to be transmitted by the UE but also information on the SRS to be
transmitted in the same subframe by the other UE. Examples of the
information on the SRS include a symbol in which the SRS is
transmitted and information on the RB in which the SRS is
transmitted. The eNB may include the information in the L1/L2
control information, and notify the L1/L2 control information to
the UE via the L1/L2 control signaling. The eNB may include the
information in the L1/L2 control information together with the
other scheduling information, and notify the L1/L2 control
information to the UE via the L1/L2 control signaling.
[0839] When the eNB does not transmit, to the UE, another channel
or another signal in a SRS transmission symbol of the other UE, the
eNB may set prevention of transmission of the other channel or the
other signal in the SRS transmission symbol, and notify the UE of
the setting. Alternatively, prevention of transmission of the other
channel or the other signal in the SRS transmission symbol of the
other UE may be predetermined in, for example, a standard, and the
UE may prevent the other channel or the other signal from being
transmitted in the SRS transmission symbol of the other UE.
[0840] Consequently, the interference with the UE that transmits
the SRS can be reduced.
[0841] Although the setting of the SRS is made per symbol, a time
interval shorter than a symbol may be applied. The SRS may be set,
for example, per half a symbol.
[0842] The information on the RB in which the SRS is transmitted
may be set per RB or a plurality of RBs. Alternatively, subcarrier
information may be set not based on the RB but per subcarrier or a
plurality of sub-carriers.
[0843] The eNB may notify the UE of the information on the SRS to
be transmitted by the UE and/or the information on the SRS to be
transmitted by the other UE, together with the subframe structure
of the SRS disclosed in the second embodiment. Alternatively, the
eNB may notify the UE of the information on the SRS to be
transmitted by the UE and/or the information on the SRS to be
transmitted by the other UE, together with the information for
starting to transmit the SRS. Alternatively, the eNB may notify the
UE of the information on the SRS to be transmitted by the UE and/or
the information on the SRS to be transmitted by the other UE,
together with the information for stopping transmission of the
SRS.
[0844] These pieces of information may be appropriately combined.
The combined pieces of information may be included in the L1/L2
control information and notified via the L1/L2 control signaling.
Alternatively, the combined pieces of information may be included
in the L1/L2 control information together with the other scheduling
information for the UE, and notified via the L1/L2 control
signaling.
[0845] Consequently, transmission and stop of the SRS can be
dynamically and flexibly set to the UE. The SRS can be transmitted
to correspond to the capability and a situation of each UE in the
cell.
Second Modification of Third Embodiment
[0846] The second modification will disclose another method for
solving the problems disclosed in the third embodiment.
[0847] When the SRS conflicts with Ack/Nack, the Ack/Nack can be
determined using the SRS. A SRS in a sequence with a sequence
number different from that to be set to a normal SRS is provided,
and the sequence number of the SRS to be transmitted varies
depending on Ack or Nack.
[0848] When a UE has a conflict in transmission between the SRS and
Ack/Nack, for example, sequences different from the sequence of the
normal SRS of its own UE are used for both Ack and Nack. When the
Ack is issued, the SRS in a sequence different from that of the SRS
to be transmitted by its own UE is transmitted. When the Nack is
issued, the SRS in a sequence different from that of the SRS to be
transmitted by its own UE and different from that of the SRS to be
transmitted when the Ack is issued is transmitted.
[0849] The cell can determine whether the Ack or the Nack is issued
by receiving the SRS and recognizing which sequence is used. Since
the signal is transmitted as the SRS, it has an uplink sounding
function as a function of the SRS. The cell can obtain an uplink
channel state by receiving the SRS.
[0850] As another example, a sequence different from the sequence
of the normal SRS of its own UE is used only when Ack is issued.
When the Ack is issued, the SRS in the sequence different from that
of the SRS to be transmitted by its own UE is transmitted. When the
Nack is issued, the SRS in the same sequence as that of the SRS to
be transmitted by its own UE is transmitted. In other words, the
normal SRS of its own UE is transmitted.
[0851] The cell can determine whether the Ack or the Nack is issued
by receiving the SRS and recognizing which sequence is used. When a
sequence for Ack is used, the cell can recognize the Ack. When a
normal sequence is used, the cell can recognize Nack. Here, there
is no need to provide a sequence for Nack in comparison with the
former example. Thus, the number of sequences to be used can be
reduced.
[0852] Although application of the sequence number to be set to the
SRS is disclosed in the aforementioned examples, the cyclic shift
(CS) may be used as an alternative method. A SRS of a CS different
from a CS to be set to the normal SRS is provided, and the CS of
the SRS to be transmitted varies depending on Ack or Nack.
[0853] For example, the CS different from the CS of the normal SRS
of its own UE is used for both Ack and Nack. When the Ack is
issued, the SRS of the CS different from that of the SRS to be
transmitted by its own UE is transmitted. When the Nack is issued,
the SRS of the CS different from that of the SRS to be transmitted
by its own UE and different from that of the SRS to be transmitted
when the Ack is issued is transmitted. The cell can determine
whether the Ack or the Nack is issued by receiving the SRS and
recognizing which CS is used. Since the signal is transmitted as
the SRS, it has an uplink sounding function as a function of the
SRS. The cell can obtain an uplink channel state by receiving the
SRS.
[0854] As another example, the CS different from the CS of the
normal SRS of its own UE is used only when the Ack is issued. When
the Ack is issued, the SRS of the CS different from that of the SRS
to be transmitted by its own UE is transmitted. When the Nack is
issued, the SRS with the same CS as that of the SRS to be
transmitted by its own UE is transmitted. In other words, the
normal SRS of its own SRS is transmitted. The cell can determine
whether the Ack or the Nack is issued by receiving the SRS and
recognizing which CS is used. When a CS for Ack is used, the cell
can recognize the Ack. When the normal CS is used, the cell can
recognize Nack. Here, there is no need to provide a CS for Nack in
comparison with the former example. Thus, the number of CSs to be
used can be reduced.
[0855] When the CSs are used, the orthogonality exists between
different CSs. Thus, when the SRS indicating Ack or Nack of its own
UE is multiplexed with the SRS of the other UE, a reception error
rate of Ack or Nack in the cell can be reduced.
[0856] Although the aforementioned example discloses application of
the CS to be set to the SRS, information on the SRS may be
modulated as an alternative method. When the SRS conflicts with
Ack/Nack, information on the SRS to be transmitted is modulated
depending on Ack or Nack.
[0857] For example, the BPSK modulation is performed. When the Ack
is issued, each of bits of the SRS to be transmitted by its own UE
is multiplied by minus 1. When the Nack is issued, each of the bits
of the SRS to be transmitted by its own UE is multiplied by 1. The
SRS modulated in such a manner is mapped to the normal resources
and then transmitted.
[0858] The cell can determine whether the Ack or the Nack is issued
by receiving the SRS and determining whether the bit is multiplied
by minus 1 or 1. Since the signal is transmitted as the SRS, it has
an uplink sounding function as a function of the SRS. The cell can
obtain an uplink channel state by receiving the SRS.
[0859] Information on the method for multiplexing the Ack/Nack with
the SRS that is disclosed in the second modification may be
provided. The following (1) to (6) will be disclosed as specific
examples of the information:
[0860] (1) a sequence to be used for Ack;
[0861] (2) a sequence to be used for Nack;
[0862] (3) a CS to be used for Ack;
[0863] (4) a CS to be used for Nack;
[0864] (5) a method for modulating the SRS information; and
[0865] (6) information on which modulating method is applied.
[0866] When the uplink control signal such as Ack/Nack conflicts
with the SRS, the uplink control signal can be multiplexed with the
SRS by setting such information. The method for setting the
information on time-division multiplexing and the method for
notifying the information from the eNB to the UE which are
disclosed in the first modification of the third embodiment may be
applied to a method for setting the information and a method for
notifying the information from the eNB to the UE, respectively.
[0867] The sequence to be used for the SRS sometimes varies for
each cell. Here, the other cells may use the sequence for Ack/Nack.
Thus, a problem of interference in uplink signal between UEs may
arise. As a method for solving such a problem, the sequences for
Ack/Nack may vary between cells. Since the different sequences are
used between the cells, the interference in uplink signal between
the UEs can be reduced.
[0868] Methods for varying sequences for Ack/Nack between cells
include a method for determining a sequence to be used for each
cell in, for example, a standard. The sequence may be a sequence
for Ack/Nack that can be derived using an ID unique to the
cell.
[0869] Alternatively, when the cell has determined the sequence for
Ack/Nack, the cell notifies an adjacent cell of the sequence
number. Upon receipt of the sequence number, the adjacent cell
determines a sequence for Ack/Nack except for the received sequence
number. Notification of the sequence number for Ack/Nack between
these cells can avoid use of the same sequence between the
cells.
[0870] A CN node may determine the sequence number. The cell may
notify the CN node of the sequence number. The CN node may notify
each cell of the sequence for Ack/Nack. Since this eliminates the
need for notification of the sequence number between the cells, the
signaling between the cells can be reduced.
[0871] When the cell finishes using the different sequences for
Ack/Nack, it notifies the adjacent cell of the end sequence number.
Upon receipt of the sequence number, the adjacent cell determines a
sequence for Ack/Nack by including the received sequence number.
Notification of the sequence number indicating the end of the use
for Ack/Nack between these cells can increase the use efficiency of
the sequence.
[0872] Application of the methods disclosed in the second
modification enables transmission of both of Ack/Nack, etc. and the
SRS in the NR, even when these signals conflict with each other in
the same subframe. Thus, the cell can receive the Ack/Nack and the
SRS with predefined timing. Enabling reception of Ack/Nack with the
predefined timing allows the cell to perform retransmission control
without any latency. Enabling reception of the SRS with the
predefined timing allows the cell to perform precoding with high
precision.
[0873] Since there is no need to set the frequency resources and
the time resources aside from the radio resources to be used for
the SRS, information that can be transmitted is never reduced. Even
when the frequency resources and the time resources are limited,
the SRS and the uplink control signal can be transmitted with the
same radio resources. Thus, the use efficiency of the radio
resources can be increased, and reduction in the transmission rate
and in the transmission capacity can be suppressed.
[0874] Although the conflict between Ack/Nack and the SRS in a UE
is disclosed, the methods disclosed in the second modification may
be applied even to a conflict between a SR and the SRS. The SR may
correspond to Ack/Nack to be applied. For example, the presence of
the SR may correspond to Ack, and the absence of the SR may
correspond to Nack.
[0875] Both signals of the SR and the SRS can be transmitted in the
NR even when the SR and the SRS conflict with each other. Thus, the
cell can receive the SR and the SRS with predefined timing.
Enabling reception of the SR with the predefined timing allows the
cell to start transmission of the uplink signal earlier. Enabling
reception of the SRS with the predefined timing allows the cell to
perform precoding with high precision.
Third Modification of Third Embodiment
[0876] The third modification will disclose another method for
solving the problems disclosed in the third embodiment.
[0877] When a UE has a conflict between the SRS and the uplink
control signal, priorities are assigned to the SRS and the uplink
control signal to determine which one should be preferentially
transmitted. For example, Ack/Nack is prioritized, or the SRS is
prioritized. The other example methods for assigning the priorities
include assuming that the priorities increase in ascending order of
values indicating the priorities, e.g., the Ack/Nack is given the
highest priority, the CQI/CSI is given the second highest priority,
and the SRS is given the third highest priority.
[0878] A method for determining the priorities will be disclosed.
For example, the priorities may be statically predetermined in, for
example, a standard. The UE transmits the SRS or the uplink control
signal according to the determined priority. For example, it is
determined, in a standard, that the Ack/Nack is given the highest
priority, the CQI/CSI is given the second highest priority, and the
SRS is given the third highest priority. Giving the Ack/Nack a
higher priority enables the Ack/Nack to be transmitted earlier
without any latency, which can shorten the latency until the
retransmission.
[0879] For another example, it is determined, in a standard, that
the Ack/Nack is given the highest priority, the SRS is given the
second highest priority, and the CQI/CSI is given the third highest
priority. Giving the SRS a higher priority than the CQI/CSI enables
the cell to evaluate fluctuations in a downlink channel state
without any latency. This is effective when the fluctuations in the
downlink channel state take priority over fluctuations in an uplink
channel state.
[0880] For another example, it is determined, in a standard, that
the SRS is given the highest priority, the Ack/Nack is given the
second highest priority, and the CQI/CSI is given the third highest
priority. Giving the SRS a higher priority to prioritize the SRS
enables evaluation of fluctuations in the uplink channel state
without any latency. This is effective when the fluctuations in the
downlink channel state are evaluated in the TDD using the
fluctuations in the uplink channel state.
[0881] When which signal is to be transmitted has been determined
according to the set priorities, the other signals are not
transmitted. Specifically, the other signals are discarded.
Discarding the other signals enables reduction in the signaling
load and avoidance of complexity in the control.
[0882] When which signal is to be transmitted has been determined
according to the set priorities, the other signals may be
transmitted in a subframe after a subframe in which a conflict has
occurred as an alternative method. A part or the entirety of the
SRS and the uplink control signal may be transmitted in a subframe
after the subframe in which the conflict has occurred. These
settings may be made for each signal.
[0883] For example, when it is determined that the SRS and the
CQI/CSI are not transmitted in a subframe in which a conflict has
occurred, they are not transmitted in the subsequent subframes. For
example, when it is determined that the Ack/Nack and the SR are not
transmitted in the subframe in which the conflict has occurred,
they may be transmitted in the subsequent subframes.
[0884] Since the SRS and the CQI/CSI are transmitted to measure or
recognize a previous state of a radio channel, they can be newly
transmitted even if they are not transmitted in the subsequent
subframes. In contrast, the Ack/Nack has a slight latency in the
retransmission control if it is not transmitted in the subsequent
subframes. If the SR is not transmitted in the subsequent
subframes, the SR has to wait the transmission timing of the SR
again, which causes the latency for starting to transmit the uplink
signal.
[0885] As described above, whether to perform transmission in a
subframe subsequent to the subframe in which the conflict has
occurred is set according to a type of a signal, which enables the
setting to correspond to the characteristics of the type of the
signal.
[0886] For another method, an algorithm for determining the
priorities may be statically predetermined in, for example, a
standard. The UE transmits the SRS or the uplink control signal
according to the priority determined by the determined algorithm.
The example method may include deriving a prioritized probability
of the next SRS from the number of transmissions of the SRS since n
preceding times, comparing the prioritized probability with a
threshold .alpha. for determining the presence or absence of the
transmission, and determining whether to transmit the SRS. For
example, the SRS is transmitted when the prioritized probability is
larger than or equal to the threshold .alpha., and the SRS is not
transmitted when the prioritized probability is larger than the
threshold .alpha.. Parameters to be used for the algorithm for
determining the priorities may be statically predetermined in, for
example, a standard. The parameters in the example of the algorithm
are n and a.
[0887] A simple and specific example thereof will be disclosed. The
parameters in the algorithm are predetermined in a standard as n=1
and .alpha.=0.5. A prioritized probability x is derived from a sum
of the number of transmissions of the SRS since one immediate
preceding time. If the SRS is not transmitted at the one immediate
preceding time, the prioritized probability x is x=0/1=0. When this
prioritized probability x is compared with the threshold
.alpha.=0.5, x<.alpha. holds. Thus, it is determined that the
next SRS is to be transmitted. If the SRS is transmitted at the one
immediate preceding time, the prioritized probability x is x=1/1=1.
When this prioritized probability x is compared with the threshold
.alpha.=0.5, x.gtoreq..alpha. holds. Thus, it is determined that
the next SRS is not transmitted.
[0888] Each of the uplink control signals may have a threshold. A
threshold may be determined not only for each of the SRSs but also
for each of the uplink control signals. The prioritized probability
may be derived and the threshold may be determined so that the
priorities of not only the SRSs but also the uplink control signals
are determined. A signal to be transmitted next may be determined
through comparison of the prior probabilities of the SRSs and the
uplink control signals. This enables determination of the signal to
be transmitted next according to a transmission state in n
preceding times.
[0889] Although statically predetermining, in, for example, a
standard, the algorithm and the parameters for determining the
priorities is disclosed, the eNB may set the parameters and notify
the UE of the parameters. The notification method is to include the
parameters in the broadcast information and broadcast the broadcast
information. Here, the parameters are set for each cell, and
notified to the UEs being served by the cell. Alternatively, the
parameters may be notified via the RRC-dedicated signaling. The
parameters are set for each cell, and notified individually to each
of the UEs. Alternatively, the parameters may be set for each UE.
The parameters are set for each UE, and notified individually to
each of the UEs.
[0890] Upon notification of the parameters, the UE determines the
priorities by substituting the parameters for the algorithm for
determining the priorities.
[0891] Consequently, the parameters can be changed according to a
state of the cell, for example, a load state and a state in which
the MIMO is applied, so that settings appropriate for the state of
the cell can be made.
[0892] Consequently, both the cell and the UE can recognize which
one of the uplink control signal and the SRS is prioritized when
the uplink control signal conflicts with the SRS, by statically
predetermining which one is prioritized in, for example, a
standard. Thus, malfunctions in a system can be reduced. Since
notification of the priorities between the cell and the UE or
between eNBs is unnecessary, the signaling load can be reduced.
[0893] Although statically predetermining, in, for example, a
standard, the priorities as a method for determining the priorities
is disclosed, the priorities may be semi-statically or dynamically
determined.
[0894] The following (1) to (9) will be disclosed as specific
examples of a judgment indicator for determining the
priorities:
[0895] (1) whether the subframe is self-contained;
[0896] (2) whether precoding for the downlink MIMO using the SRS is
performed;
[0897] (3) channel quality information of the UE;
[0898] (4) the moving speed of the UE;
[0899] (5) acceleration (change in the speed) of the UE;
[0900] (6) the rotational speed of the UE;
[0901] (7) rotational acceleration of the UE;
[0902] (8) the number of multiplexed UEs; and
[0903] (9) combinations of (1) to (8) above.
[0904] Taking, as the judgment indicator, whether the subframe is
self-contained in (1), for example, when the subframe is
self-contained, Ack/Nack is prioritized. Specifically, the Ack/Nack
is given the highest priority. When the subframe is not
self-contained, another uplink control signal or the SRS is
prioritized. For example, the SRS is given the highest priority.
When the subframe is self-contained, Ack/Nack can be transmitted
earlier. Thus, prioritizing the Ack/Nack when the Ack/Nack is set
can lower the latency in the retransmission process.
[0905] Taking, as the judgment indicator, whether precoding for the
downlink MIMO using the SRS is performed in (2), for example, when
the precoding for the downlink MIMO using the SRS is performed, the
SRS is prioritized. Specifically, the SRS is given the highest
priority. When the precoding for the downlink MIMO using the SRS is
not performed, the SRS is not prioritized but the other uplink
control signal is prioritized. When the precoding for the downlink
MIMO using the SRS is performed, the cell can receive the SRS with
predefined timing by prioritizing the SRS. The SRS can be reflected
to derive a pre-coding weight for the downlink MIMO. Consequently,
the precoding performance can be improved.
[0906] Taking, as the judgment indicator, the channel quality
information of the UE in (3), for example, when the channel quality
is inferior, the SRS is prioritized. Specifically, the SRS is given
the highest priority. When the channel quality is superior, the SRS
is not prioritized but the other uplink control signal is
prioritized. When the channel quality is inferior, the cell can
receive the SRS with predefined timing by prioritizing the SRS. The
SRS can be reflected to derive a pre-coding weight for the downlink
MIMO. Consequently, the precoding performance can be improved.
[0907] Taking, as the judgment indicator, the moving speed of the
UE in (4), for example, when the moving speed is higher, the SRS is
prioritized. Specifically, the SRS is given the highest priority.
When the moving speed is lower, the SRS is not prioritized but the
other uplink control signal is prioritized. When the moving speed
is higher, the cell can receive the SRS with predefined timing by
prioritizing the SRS, and can reduce the influence of the Doppler
frequency due to the moving speed of the UE. Thus, precision of the
SRS can be increased, and the precoding performance can be
improved.
[0908] Taking, as the judgment indicator, the acceleration (change
in the speed) of the UE in (5), for example, when the acceleration
is greater, the SRS is prioritized. Specifically, the SRS is given
the highest priority. When the acceleration is less, the SRS is not
prioritized but the other uplink control signal is prioritized.
When the acceleration is greater, the cell can receive the SRS with
predefined timing by prioritizing the SRS, and can reflect change
in the moving speed of the UE earlier. Consequently, the precoding
performance can be improved.
[0909] Taking, as the judgment indicator, the rotational speed of
the UE in (6), for example, when the rotational speed is higher,
the SRS is prioritized. Specifically, the SRS is given the highest
priority. When the rotational speed is lower, the SRS is not
prioritized but the other uplink control signal is prioritized.
When the rotational speed is higher, the cell can receive the SRS
with predefined timing by prioritizing the SRS, and can reflect the
rotation of the UE earlier. Consequently, the precoding performance
can be improved.
[0910] Taking, as the judgment indicator, the rotational
acceleration (change in the rotational speed) of the UE in (7), for
example, when the rotational acceleration is greater, the SRS is
prioritized. Specifically, the SRS is given the highest priority.
When the rotational acceleration is less, the SRS is not
prioritized but the other uplink control signal is prioritized.
When the rotational acceleration is greater, the cell can receive
the SRS with predefined timing by prioritizing the SRS, and can
reflect change in the rotational speed of the UE earlier.
Consequently, the precoding performance can be improved.
[0911] Taking, as the judgment indicator, the number of multiplexed
UEs in (8), for example, when the number of multiplexed UEs is
many, the SRS is prioritized. Specifically, the SRS is given the
highest priority. When the number of multiplexed UEs is fewer, the
SRS is not prioritized but the other uplink control signal is
prioritized. When the number of multiplexed UEs in the MIMO is
many, the cell can receive the SRS with predefined timing by
prioritizing the SRS, and can increase the precision of the SRS for
each UE. Thus, even when the number of multiplexed UEs is many, the
precoding weight with higher precision can be derived, and the
precoding performance can be improved.
[0912] A method for determining the priorities will be disclosed.
The UE determines the priorities. When the UE determines the
priorities and the SRS conflicts with the uplink control signal,
the eNB does not know which one is to be transmitted. Here, the eNB
may demodulate all types of the signals. Although it takes time to
demodulate the signals, the eNB can demodulate any one of the
signals.
[0913] As an alternative method, the UE may notify the eNB of the
determined priorities. The notification method may be the RRC
signaling, the MAC signaling, or the L1/L2 control signaling.
Consequently, the eNB can demodulate the signals as predefined
signals according to the priorities determined by the UE. The
aforementioned judgment indicators may be appropriately applied as
the judgment indicators for the UE to determine the priorities. For
example, the UE may apply (3) to (7) above that can be evaluated by
its own UE. Alternatively, the UE may apply (1) above when the UE
can recognize whether the subframe is self-contained, from the
scheduling information.
[0914] A threshold for determination (hereinafter may be referred
to as a "determination threshold") may be provided as an
alternative method. The eNB may notify the UE of the determination
threshold. The determination threshold is, for example, a threshold
for determining the moving speed of the UE, etc. The disclosed
judgment indicators may have appropriate thresholds for
determination. The UE determines the priorities according to the
received determination thresholds. For example, when the moving
speed of the UE is higher than or equal to the determination
threshold, the SRS is prioritized. When the moving speed of the UE
is less than the determination threshold, the SRS is not
prioritized but the other uplink control signal is prioritized.
Consequently, which signal the eNB prioritizes can be controlled to
some extent.
[0915] Another method for determining the priorities will be
disclosed. The eNB determines the priorities. When the eNB
determines the priorities, the eNB obtains a judgment indicator for
the priorities. The eNB may evaluate the judgment indicator, or the
UE may evaluate the judgment indicator and notify it to the eNB.
Whether the eNB or the UE evaluates the judgment indicator may be
set according to the judgment indicator. The methods disclosed in
the second embodiment may be applied to a method for the UE to
evaluate the judgment indicator and notify it to the eNB.
[0916] The eNB notifies the UE of the priorities. When the eNB
determines the priorities, the UE does not know the priorities.
Thus, notification of the priorities from the eNB to the UE enables
the UE to recognize the priorities, which enables the same
priorities to be set between the eNB and the UE.
[0917] A method for notifying the priorities from the eNB to the UE
will be disclosed. The eNB determines the priorities for each cell.
The eNB includes the determined priorities in the broadcast
information to broadcast the broadcast information.
[0918] As an alternative method, the eNB determines the priorities
for each UE. The eNB notifies the determined priorities via the
UE-dedicated signaling. For example, the priorities are included in
the RRC-dedicated signaling and notified. Alternatively, the
priorities may be included in a MAC CE to be notified via the MAC
signaling. Since the HARQ is applied similarly as via the RRC
signaling, the setting can be made earlier at a lower error rate
than that via the RRC signaling. Alternatively, the priorities may
be included in the L1/L2 control signal to be notified via the
L1/L2 control signaling. Consequently, the setting can be made
earlier than that via the MAC signaling.
[0919] Application of such methods enables flexible setting of the
priorities according to, for example, a state of a frame structure,
the number of multiplexed UEs in the downlink MIMO, and a state of
the UE as described in the examples of the judgment indicators. The
priorities can be semi-statically or statically set according to
time fluctuations in such a state. Furthermore, the latency in
retransmission can be reduced and the precoding performance can be
improved, according to the time fluctuations in a state.
[0920] Setting the priorities eliminates the need for using symbols
for new frequency resources and the other information as described
in the third embodiment and the first modification of the third
embodiment. Thus, the use efficiency of the radio resources and the
transmission rate can be increased. Increase in the required number
of sequences and the CSs can be suppressed as described in the
second modification of the third embodiment. Consequently, many
cells and many UEs are operable.
[0921] The methods disclosed in the third modification may be used
when the third embodiment, and the first and the second
modifications of the third embodiment are not applicable. The eNB
may determine whether the third embodiment, and the first and the
second modifications of the third embodiment are applicable
according to a use state of the radio resources in the cell and use
states of a sequence and a CS, and may determine application of the
third modification of the third embodiment when the third
embodiment, and the first and the second modifications of the third
embodiment are not applicable.
[0922] For example, the time-division multiplexing method is
performed if the time-division multiplexing can be performed, and a
method based on the priorities is performed if the time-division
multiplexing cannot be performed. The UE does not transmit either
the uplink control signal or the SRS according to the set
priorities. For example, the frequency-division multiplexing method
is performed if the frequency-division multiplexing can be
performed, and the method based on the priorities is performed if
the frequency-division multiplexing cannot be performed. The UE
does not transmit either the uplink control signal or the SRS
according to the set priorities.
[0923] Without being limited to this, the time-division
multiplexing method may be performed if the time-division
multiplexing can be performed, and the frequency-division
multiplexing may be performed if the time-division multiplexing
cannot be performed. Alternatively, the frequency-division
multiplexing method may be performed if the frequency-division
multiplexing can be performed, and the frequency-division
multiplexing method may be performed if the frequency-division
multiplexing cannot be performed.
[0924] The eNB may semi-statically notify the UE of a method for
avoiding a conflict. The notification may be made via the RRC
signaling. Alternatively, the eNB may dynamically notify the UE of
the method for avoiding a conflict. The notification may be made
via the L1/L2 control signaling or the MAC signaling. The method
for avoiding a conflict may be set when a subframe structure of the
SRS or a structure of the uplink control signal is set.
[0925] The eNB may determine the priorities and notify the UE of
the determined priorities when determining to apply the third
modification of the third embodiment. Consequently, the UE can
determine that the setting according to the priorities has been
made. The UE performs transmission according to the received
priorities. Consequently, the eNB can apply the third modification
according to a state of the cell.
[0926] Specific examples of the judgment indicators (1) to (10)
will be described as follows:
[0927] (1) the number of UL symbols in one subframe;
[0928] (2) the number of DL symbols in one subframe;
[0929] (3) the number of symbols of gaps in one subframe;
[0930] (4) the number of RBs for transmitting the SRS;
[0931] (5) the number of RBs that are not used for transmitting the
SRS;
[0932] (6) a system bandwidth;
[0933] (7) the number of symbols necessary for an uplink control
signal;
[0934] (8) the number of symbols necessary for the SRS;
[0935] (9) a period of the SRS; and
[0936] (10) combinations of (1) to (9) above.
[0937] For example, when the number of UL symbols in one subframe
is fewer than a predetermined number of symbols, it is determined
that the time-division multiplexing cannot be performed. For
example, when the number of symbols necessary for an uplink control
signal is more than a predetermined number of symbols, it is
determined that the time-division multiplexing cannot be performed.
For example, when the number of RBs for transmitting the SRS is
more than a predetermined number of RB s, it is determined that the
frequency-division multiplexing cannot be performed. The
predetermined number may be of a predetermined value.
Alternatively, the eNB may notify the UE of the predetermined
value. The predetermined value may be notified together with a
method for setting combinations of the methods for avoiding a
conflict.
[0938] Although the judging entity is the eNB in the previous
examples, the judging entity may be the UE. The UE may obtain a
judgment indicator and make the determination.
[0939] The methods disclosed in the third embodiment, and the first
to the third modifications of the third embodiment may be
appropriately combined and used. Even in such a case, the same
advantages as those according to the third modification can be
produced.
[0940] It is possible to select which one of the methods disclosed
in the third embodiment, and the first to the third modifications
of the third embodiment is applied and set the selected one. The
method may be changed.
[0941] Information indicating which method in the third embodiment,
and the first to the third modifications of the third embodiment
may be provided. The eNB may select which method is to be applied,
and notify the UE of the information. The methods disclosed in the
third modification of the third embodiment may be applied to a
method for notifying the information. Consequently, the eNB can
select the method according to a state of the cell, and a radio
propagation situation and a state of the UE.
[0942] An identifier may be assigned to each of the methods for
avoiding a conflict, and may be notified to the UE. This can reduce
the amount of signaling information.
Fourth Embodiment
[0943] The 3GGP proposes measuring an uplink signal from the UE on
the NW side as a technique of the NR (see 3GPP R1-167200
(hereinafter referred to as "Reference 7"), 3GPP R1-166393
(hereinafter referred to as "Reference 8"), 3GPP R1-166387
(hereinafter referred to as "Reference 9"), and 3GPP R1-165213
(hereinafter referred to as "Reference 10")). In the NR, for
example, a transmission reception point (TRP) or a distributed unit
(DU) (see 3GPP R3-161013 (hereinafter referred to as "Reference
11")) is proposed as a device or a node on the NW side. The
proposal includes that the TRP and the DU receive and measure an
uplink signal.
[0944] Although the UE performs transmission and reception with one
TRP (will be referred to as a "serving TRP"), a plurality of TRPs
receive an uplink signal for measurement that has been transmitted
from the UE. FIG. 54 illustrates the uplink signal from the UE when
an eNB is configured by a plurality of TRPs.
[0945] Each of a TRP1 5101, a TRP2 5102, a TRP3 5103, a TRP4 5104,
and a TRPS 5105 is connected to an eNB 5106, and has at least a
transmission/reception function. The transmission/reception timings
of the TRP 5101 to the TRP 5105 are synchronized with each other. A
UE1 5107 is communicating with the TRP3 5103. The TRP3 5103 is a
serving TRP of the UE1 5107. Since the UE1 5107 performs
transmission and reception with the serving TRP 5103, the UE1 5107
follows a preset timing advance (TA) (see Reference 4) with the
serving TRP 5103 as the timing of the uplink signal.
[0946] When the other TRPs, specifically, the TRP1 5101, the TRP2
5102, the TRP4 5104, and the TRPS 5105 receive the uplink signal
transmitted from the UE1 5107 using the TA set with the serving TRP
5103, the other TRPs have differences in the reception timings.
[0947] This is because, for example, a distance and a radio
propagation environment between the UE1 5107 and each of the TRP
5101 to the TRP 5105 differ, and thus, the radio propagation time
between the UE1 5107 and the serving TRP 5103 is different from the
radio propagation time between the UE1 5107 and each of the other
TRP 5101, the TRP 5102, the TRP 5104, and the TRP 5105. Thus, the
other TRPs may not be able to receive the uplink signal for
measurement that has been transmitted from the UE1 5107 using the
TA set with the serving TRP 5103.
[0948] FIG. 55 illustrates the timing of receiving, by the TRPs,
the uplink signal transmitted from the UE 1. FIG. 55 illustrates
the case where the TRP 3 is the serving TRP. FIG. 55 illustrates
the TDD. FIG. 55 illustrates one subframe including a downlink
signal (DL), a gap (Gap) without any transmission and reception,
and an uplink signal (UL). In FIG. 55, Rw denotes a reception
duration of the uplink signal by the TRP. Tw denotes a duration of
the uplink signal, and Tw=Rw holds herein.
[0949] T1 denotes a radio propagation time from the UE 1 to the TRP
1. T2 denotes a radio propagation time from the UE 1 to the TRP 2.
T3 denotes a radio propagation time from the UE 1 to the TRP 3. T4
denotes a radio propagation time from the UE 1 to the TRP 4. T5
denotes a radio propagation time from the UE 1 to the TRP 5. Each
of the radio propagation times T1, T2, T3, T4, and T5 represents a
time from transmission of the uplink signal by the UE 1 to the
arrival at the corresponding TRP. The TA3 is the TA set between the
serving TRP and the UE 1. The TA3 is set twice the radio
propagation time T3 from the UE 1 to the TRP 3.
[0950] The UE 1 transmits the uplink signal earlier in timing by
the TA3 preset with the serving TRP from the downlink reception
timing. Consequently, the TRP 3 can receive the uplink signal from
the UE 1 in synchronization with the reception timing of the uplink
signal.
[0951] The radio propagation time between the UE 1 and the TRP 1 or
the TRP 2 is shorter than that between the UE 1 and the TRP 3.
[0952] Thus, the arrival timing of the uplink signal from the UE 1
at the TRP 1 is earlier than the reception timing of the uplink
signal. The arrival timing is earlier by T3-T1 in the example of
FIG. 55.
[0953] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 2 is earlier than the reception timing of the
uplink signal. The arrival timing is earlier by T3-T2 in the
example of FIG. 55. T2 denotes the radio propagation time from the
UE 1 to the TRP 2.
[0954] On the other hand, the radio propagation time between the UE
1 and the TRP 4 or the TRP 5 is longer than that between the UE 1
and the TRP 3.
[0955] Thus, the arrival timing of the uplink signal from the UE 1
at the TRP 4 is later than the reception timing of the uplink
signal. The arrival timing is later by T4-T3 in the example of FIG.
55.
[0956] Similarly, the reception timing of the uplink signal from
the UE 1 at the TRP 5 is later than the arrival timing of the
uplink signal. The arrival timing is later by T5-T3 in the example
of FIG. 55.
[0957] Thus, when the arrival timing of the uplink signal from the
UE 1 is earlier or later than the reception timing of the uplink
signal at each of the TRPs, the uplink signal does not fall within
the uplink signal reception duration Rw at the TRP, and a duration
for actually receiving the uplink signal is shortened.
Consequently, the uplink signal cannot be sometimes accurately
demodulated.
[0958] Thus, when not only the serving TRP but also the other TRPs
measure a uplink signal for measurement from the UE such as the
uplink signal for measurement that has been proposed in the NR, the
other TRPs will have a problem of failing to accurately receive and
demodulate the uplink signal for measurement.
[0959] The fourth embodiment will disclose a method for solving
such a problem.
[0960] An adjustment value is set to the TA. The TA not only for
the serving TRP but also for the UE that transmits an uplink signal
receivable at neighboring TRPs, for example, an uplink signal for
measurement may have an adjustment value. The adjustment value is
denoted by .alpha.. The UE delays the uplink transmission timing by
the adjustment value .alpha. for the TA set with the serving TRP.
The UE may set TA-.alpha. as the TA including the adjustment
value.
[0961] The TA may include an offset value indicating a switching
duration between transmission and reception in the eNB or the UE if
the offset value is present as in the TDD. Assuming the offset
value as TAoff, (TA+TAoff-.alpha.) may be set as the TA including
the adjustment value.
[0962] For example as conventionally described in Reference 4
(Section 8), the UE sets the uplink transmission timing earlier
than the downlink reception timing by (NTA+NTAoffset).times.TS
seconds. Here, NTA represents a value of the TA set in units of TS.
NTAoffset represents a value of the TAoffset set in units of TS. A
fixed value is preset to the TAoffset in a standard. In contrast,
the UE may set the uplink transmission timing earlier than the
downlink reception timing by (NTA+NTAoffset-.alpha.).times.TS
seconds. .alpha. denotes the adjustment value set in units of
TS.
[0963] Provision of the adjustment value .alpha. in setting the
uplink transmission timing of the UE enables adjustment of a
duration during which the serving TRP and the other TRPs actually
receive the uplink signal transmitted from the UE, specifically, a
duration of the uplink signal in the uplink signal reception
duration Rw. Setting the adjustment value .alpha. to an appropriate
value enables not only the serving TRP but also the other TRPs to
receive the uplink signal transmitted from the UE. The TA may be a
value obtained by including an adjustment value in the conventional
TA, without separately providing the adjustment value. Even in such
a case, the same advantages can be produced.
[0964] FIG. 56 illustrates the timing of receiving, by the TRPs,
the uplink signal transmitted from the UE 1 when the adjustment
value .alpha. is provided. FIG. 56 illustrates the case where the
TRP 3 is the serving TRP. FIG. 56 illustrates the TDD. Since FIG.
56 is similar to FIG. 55, the differences will be mainly described.
Unlike FIG. 55, TA 1 is 0 in FIG. 56. In other words, T1=0. This
assumes a case where the distance between the TRP 1 and the UE 1 is
the shortest.
[0965] The TA is preset between the UE 1 and the serving TRP. The
adjustment value .alpha. is set to the UE 1 in consideration of
radio propagation times with the serving TRP and the neighboring
TRPs, here, the TRP 1 to the TRP 5. The UE 1 transmits, using the
TA3 and the adjustment value .alpha. that have been set, the uplink
signal earlier than the downlink reception timing by TA3-.alpha..
The TA3 is set twice the radio propagation time T3 from the UE 1 to
the TRP 3. TA3 may include the TAoffset. TA3=2.times.T3+TAoff may
hold.
[0966] Here, the arrival timing of the uplink signal from the UE 1
at the TRP 3 is later than the reception timing of the uplink
signal by the adjustment value .alpha..
[0967] In contrast, the arrival timing of the uplink signal from
the UE 1 at the TRP 1 is earlier than the reception timing of the
uplink signal by T3-T1. However, the arrival timing is later than
the arrival timing using only the conventional TA3 by the
adjustment value .alpha.. Thus, the duration during which the
uplink signal from the UE 1 can be received by the TRP 1 is
increased by the adjustment value .alpha..
[0968] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 2 is earlier than the reception timing of the
uplink signal by T3-T2. However, the arrival timing is later than
the arrival timing using only the conventional TA3 by the
adjustment value .alpha.. Thus, the duration during which the
uplink signal from the UE 1 can be received by the TRP 2 is
increased by the adjustment value .alpha..
[0969] The arrival timing of the uplink signal from the UE 1 at the
TRP 4 is later than the reception timing of the uplink signal by
T4-T3. Moreover, the arrival timing is later than the arrival
timing using only the conventional TA3 by the adjustment value
.alpha.. Thus, the duration during which the uplink signal from the
UE 1 can be received by the TRP 4 is decreased by the adjustment
value .alpha..
[0970] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 5 is later than the reception timing of the uplink
signal by T5-T3. Moreover, the arrival timing is later than the
arrival timing using only the conventional TA3 by the adjustment
value .alpha.. Thus, the duration during which the uplink signal
from the UE 1 can be received by the TRP 4 is decreased by the
adjustment value .alpha..
[0971] Setting the adjustment value .alpha. to the UE in such a
manner enables adjustment of the arrival timing of the uplink
signal from the UE at the neighboring TRPs. The actual reception
duration of the uplink signal from the UE at the neighboring TRPs
can be adjusted. Thus, provision of the appropriate adjustment
value .alpha. enables not only the serving TRP but also the
neighboring TRPs to receive and demodulate the uplink signal
transmitted from the UE.
[0972] Examples of deriving the adjustment value .alpha. will be
disclosed. The adjustment value .alpha. for the UE may be derived
using the TA of the neighboring TRPs for the UE. Examples of the
derivation using the TA of the serving TRP and the neighboring TRPs
will be disclosed. Here, Tw=Rw holds. The serving TRP of the UE is
the TRP 3. Assuming an uplink-signal receivable duration from the
UE at the closest TRP as "a", .alpha.=Tw-(T3-.alpha.-min(Tj))
holds. Assuming an uplink-signal receivable duration from the UE at
the farthest TRP as "b", a signal can be received during
b=Tw-(max(Tj)-T3+.alpha.). Here, j denotes the TRP number. Tj=TAj/2
holds.
[0973] The uplink-signal receivable duration from the UE at the
closest TRP is set equal to the uplink-signal receivable duration
from the UE at the farthest TRP. .alpha.=T3-(max(Tj)+min(Tj))/2 may
hold. Here, .alpha.=b=Tw-(max(Tj)-min(Tj))/2.
[0974] FIG. 57 illustrates an example structure of the uplink
signal. The uplink signal consists of signals such as sequences and
Cyclic Prefix (CP). The uplink-signal receivable duration "a" is a
duration (Tw-CP duration) during which at least the signals such as
sequences in the uplink signal are to be transmitted. The
uplink-signal receivable duration may be any duration in the Tw
because of the presence of the CP.
[0975] The CP may be set to satisfy CP=(max(Tj)-min(Tj))/2 so that
.alpha.=Tw-CP holds. The CP length may be set according to a
distance to the TRP at which the uplink signal from the UE can be
received. Under the setting of .alpha.=b, the uplink-signal
receivable duration at the farthest TRP from the UE is also Tw-CP.
Consequently, reception at the closest TRP and at the farthest TRP
from the UE is possible for a duration corresponding to at least
data such as the sequences in the uplink signal.
[0976] When the duration of the uplink signal is fixed and the CP
is set, the duration of the uplink signal may be maintained
constant by changing the ratio of Tw-CP.
[0977] The CP may be set to an uplink signal that can be desirably
received by the neighboring TRPs. Alternatively, the CP may be set
to a symbol including the uplink signal that can be desirably
received by the neighboring TRPs. Consequently, the serving TRP and
the neighboring TRPs can receive the uplink signal from the UE.
[0978] The CP may be set to a transmission unit including an uplink
signal that can be desirably received by the neighboring TRPs, for
example, to each symbol in a slot or a subframe. This is effective
when uplink signals to be consecutively transmitted are present in
the uplink signal that can be desirably received by the neighboring
TRPs.
[0979] Tj may be set to satisfy CP=(max(Tj)-min(Tj))/2 as an
alternative method to achieve .alpha.=Tw-CP. The TRP that can
receive the uplink signal from the UE is set according to the CP
length. This is effective when the CP length is of a fixed value.
Consequently, the serving TRP and the neighboring TRPs can receive
the uplink signal from the UE.
[0980] The reception duration at the serving TRP for receiving the
uplink signal can be equal to a reception duration when the
conventional TA (TA3) is set. The reception duration at the
neighboring TRPs can be equal to a reception duration for receiving
the uplink signal form the UEs being served thereby.
[0981] The uplink signal of the UE that can be received by the
neighboring TRPs may be frequency multiplexed, time multiplexed, or
code multiplexed with the uplink signals of the other UEs including
the UEs being served by the other TRPs. For example, the eNB maps
the uplink signal of the UE that can be received by the neighboring
TRPs to frequency-time resources different from those for the
uplink signals of the other UEs including the UEs being served by
the other TRPs. In other words, the uplink signals of the other UEs
including the UEs being served by the other TRPs are not mapped to
the frequency-time resources to which the uplink signal of the UE
that can be received by the neighboring TRPs is mapped.
[0982] For another example, the uplink signal of the UE that can be
received by the neighboring TRPs is mapped using an orthogonal code
different from those for the uplink signals of the other UEs
including the UEs being served by the other TRPs. In other words,
the uplink signals of the other UEs including the UEs being served
by the other TRPs may be mapped to the frequency-time resources to
which the uplink signal of the UE that can be received by the
neighboring TRPs is mapped. These signals should maintain the
orthogonality using different orthogonal codes.
[0983] For example, different cyclic shifts may be used when a
Zadoff-Chu (ZC) sequence is used as an uplink signal.
[0984] Consequently, the neighboring TRPs can receive, without any
conflict, the uplink signal of the UE that can be received by the
neighboring TRPs, and the uplink signals of the other UEs including
the UEs being served by the other TRPs.
[0985] The uplink signal of the UE that can be received by the
neighboring TRPs may be mapped to the frequency resources different
from those for the other data in the same subframe, for example,
the downlink data. Since a degree of freedom in allocating the
radio resources for the uplink signal of the UE that can be
received by the neighboring TRPs increases, the use efficiency of
the radio resources can be increased.
[0986] An example method for deriving the TA by the neighboring
TRPs will be disclosed.
[0987] The PRACH may be used. Studies have been made to apply, in
the NR, the PRACH for initial uplink access. Thus, the PRACH may be
used. A TRP notifies the neighboring TRPs of a PRACH configuration
that is dedicated to the TRP. The PRACH configuration includes
timing, allocation, and a sequence. Although disclosed is the
notification from the TRP to the neighboring TRPs, the TRP may make
the notification to the eNB, and then the eNB may make the
notification to the neighboring TRPs. Alternatively, when the eNB
sets each PRACH configuration, the eNB may notify each of the TRPs
of the PRACH configuration of the neighboring TRPs.
[0988] When the PRACH configuration for each TRP is used, the PRACH
of the UE for the serving TRP may conflict with the uplink
transmission of the UEs being served by the neighboring TRPs. As a
method for solving such a problem, the PRACH configuration
dedicated to the TRP may be consistent among a plurality of TRPs (a
TRP group). The PRACH configuration may be consistent among all the
TRPs. The serving TRP and the neighboring TRPs receive the PRACH
configuration.
[0989] The PRACHs even with such a PRACH configuration may conflict
with each other among the UEs being served by the TRPs. When the
serving TRP has the conflict, no RA response is notified to the UE.
Thus, the UE retransmits the PRACH. However, when not the
neighboring TRPs but the serving TRP can receive the PRACH from the
UE, the serving TRP transmits the RAR to the UE. Consequently, the
UE does not retransmit the PRACH. Thus, the neighboring TRPs cannot
receive the PRACH from the UE.
[0990] A method for solving such a problem will be disclosed.
[0991] The eNB determines whether the PRACH from the UE can be
received. Alternatively, each TRP may determine whether the PRACH
from the UE can be received, and notify the eNB of information
indicating whether the PRACH from the UE can be received. If any of
the neighboring TRPs cannot receive the PRACH, the eNB instructs
the serving TRP not to transmit the RAR to the UE. Alternatively,
the eNB notifies the serving TRP that the neighboring TRPs cannot
receive the PRACH. Then, the serving TRP determines not to transmit
the RAR to the UE.
[0992] Consequently, the UE cannot receive the RAR, and thus
retransmits the PRACH. Until the neighboring TRPs can receive the
PRACH from the UE, the UE can retransmit the PRACH.
[0993] Such a process of transmitting the PRACH to the neighboring
TRPs may be separately provided from the normal process of
transmitting the PRACH to the serving TRP. For example, when the
uplink signal from the UE is desirably received by the neighboring
TRPs, the UE may be set to perform the process of transmitting the
PRACH to the neighboring TRPs. The PRACH configuration may be
notified to the UE via the RRC signaling. The PRACH configuration
may be included in the SIB to be broadcast. Alternatively, the
PRACH configuration may be notified individually to each UE.
[0994] Provision of the process of transmitting the PRACH to the
neighboring TRPs separately from the normal process of transmitting
the PRACH to the serving TRP can simplify the control, because the
normal process of transmitting the PRACH will suffice when the
uplink signal is not measured.
[0995] The maximum value may be set to the number of
retransmissions of the PRACH in the process of transmitting the
PRACH to the neighboring TRPs. The neighboring TRPs may not be able
to receive the PRACH from the UE not due to the conflict but due to
the worse radio propagation environment. Here, repeating the
retransmission of the PRACH from the UE is useless. Here, the TRP
that cannot receive the PRACH may be excluded from the neighboring
TRPs in the setting.
[0996] Consequently, wasteful transmission of the PRACH can be
eliminated, and the power consumption of the UE and the uplink
interference power can be reduced.
[0997] Another example method will be disclosed. A PRACH dedicated
to the UE is configured. Configuring the PRACH dedicated to the UE
enables each TRP to receive the PRACH from the UE. For example, the
frequency-time resources different from each UE are set as the
PRACH configuration. Consequently, each TRP can receive the PRACH
from the UE without any conflict, and recognize of which UE the
PRACH is, from the received frequency-time resources.
[0998] The serving TRP may set the PRACH dedicated to the UE while
the serving TRP is in an RRC connected state with the UE. The
serving TRP notifies the UE of the setting. The notification may be
made via the RRC signaling. The serving TRP may instruct the UE to
transmit the PRACH dedicated to the UE. The instruction may be
given via the L1/L2 control signal. Consequently, the serving TRP
can make the UE transmit the PRACH dedicated to the UE.
[0999] The serving TRP may notify the neighboring TRPs of the PRACH
configuration dedicated to the UE. The serving TRP may notify the
UE identifier together with the PRACH configuration. Alternatively,
the serving TRP may notify the identifier of its own TRP.
Notification of the identifier of its own TRP enables the
neighboring TRPs to recognize that the TRP that notifies the
identifier is the serving TRP of the UE. The methods for notifying
the neighboring TRPs of the PRACH configuration may be applied to a
method for notifying these pieces of information.
[1000] The TRP to which the PRACH configuration has been notified
from the neighboring TRPs receives the PRACH from the UE with the
timing of the PRACH. When the PRACH is transmitted from the UE,
TA=0. The neighboring TRPs measure the latency from the
transmission timing of the PRACH to derive the TA in the uplink
transmission of the UE.
[1001] Consequently, the TA in the neighboring TRPs for the UE can
be derived.
[1002] The serving TRP may make the UE appropriately transmit the
PRACH dedicated to the UE. Since the position of the UE varies with
time, the TA not only in the serving TRP but also in the
neighboring TRPs also vary. Thus, the serving TRP makes the UE
appropriately transmit the PRACH dedicated to the UE, so that the
serving TRP and the neighboring TRPs can measure and derive the
varied TA. Consequently, the TA corresponding to the position of
the UE that varies with time can be derived.
[1003] The TRP that has derived the TA notifies the neighboring
TRPs of the derived TA. The TRP may notify not the TA but a radio
propagation time T from the UE to the TRP. TA=2.times.T holds. The
TRP may make the notification together with the identifier of its
own TRP. The TRP may make the notification together with the UE
identifier. When recognizing the serving TRP of the UE, the TRP may
notify the derived TA only to the serving TRP of the UE.
[1004] Although disclosed is the notification from the TRP to the
neighboring TRPs, the TRP may make the notification to the eNB, and
then the eNB may make the notification to the neighboring TRPs.
Alternatively, when the eNB sets the adjustment value .alpha. to
each UE, the TRP may notify the eNB of the derived TA. The eNB may
derive the adjustment value .alpha. using the obtained TA of the
neighboring TRPs, and notify it to the serving TRP. The eNB may
make the notification together with the UE identifier.
[1005] A method for notifying the UE of the adjustment value
.alpha. will be disclosed. The serving TRP notifies the UE of the
adjustment value .alpha.. The serving TRP may make the notification
via the UE-dedicated signaling. Since an appropriate value
corresponding to the position of the UE can be derived as the
adjustment value .alpha., the notification via the UE-dedicated
signaling enables setting and use of the adjustment value .alpha.
for each UE.
[1006] The following (1) to (3) will be disclosed as specific
examples of the UE-dedicated signaling:
[1007] (1) the RRC signaling: the adjustment value .alpha. may be
included in RRC message information and notified;
[1008] (2) the MAC signaling: the adjustment value .alpha. may be
included in the MAC control information and notified; and
[1009] (3) the L1/L2 signaling: the adjustment value .alpha. may be
included in the downlink L1/L2 control information and
notified.
[1010] A method for deriving the adjustment value .alpha. using the
TA of the neighboring TRPs for the UE is disclosed as an example of
deriving the adjustment value .alpha.. As an alternative derivation
example, the adjustment value .alpha. may be derived not for each
UE but for each TRP. For example, the adjustment value .alpha. is
derived using a distance between a TRP and a TRP surrounding the
TRP. The TRP surrounding the TRP may be a TRP that can receive the
uplink signal from the UE. The adjustment value .alpha. is set for
each TRP. The adjustment value .alpha. is set regardless of the
position of the UE.
[1011] A method for notifying the UE of the adjustment value
.alpha. for each TRP will be disclosed. The serving TRP broadcasts
the adjustment value .alpha. to the UEs being served thereby. The
adjustment value .alpha. may be included in the system information
to be broadcast. The identifier of the serving TRP may be broadcast
together with the adjustment value .alpha.. Consequently, the UEs
being served by the serving TRP can obtain the adjustment value
.alpha..
[1012] Alternatively, the adjustment value .alpha. may be notified
via the UE-dedicated signaling. The aforementioned examples may be
applied as examples of the signaling to be notified. The
notification via the UE-dedicated signaling enables notification
only to the UE subject to the uplink transmission for measurement.
This eliminates the need for broadcasting to all the UEs being
served by the serving TRP, which can reduce the broadcast
information to be broadcast.
[1013] Consequently, the adjustment value .alpha. can be set
regardless of the position of the UE, and the process of
transmitting an uplink transmission signal can be simplified.
[1014] Another method for notifying the UE of the adjustment value
.alpha. will be disclosed. The serving TRP may notify the UE of the
adjustment value .alpha. together with the TA for the UE. For
example, the method may be used for notification of the initial
setting of the adjustment value .alpha.. In the aforementioned
description, when the UE transmits the PRACH upon start of the
uplink access, the eNB derives the TA. Here, the neighboring TRPs
may derive the TA upon receipt of the PRACH, and the eNB may derive
the adjustment value .alpha..
[1015] The serving TRP may notify the UE of the derived adjustment
value .alpha. together with the TA. Upon initial access, the
serving TRP notifies the UE of the TA in the RA response. The
adjustment value .alpha. may be included in the RA response and
notified. The adjustment value .alpha. may be an initial value of
the adjustment value .alpha. to be set to the uplink signal that
can be received by the neighboring TRPs.
[1016] An uplink serving TRP may notify the UE of the adjustment
value .alpha. together with a TA command. The TA command is
notified via the MAC signaling. The MAC control information (MAC
CE) may include information on the adjustment value .alpha., and
the adjustment value .alpha. may be notified together with the TA
via the MAC signaling. The adjustment value .alpha. may be updated
according to the update of the TA in an RRC connected state.
[1017] The serving TRP may set the uplink signal for measurement to
the UE, and notify the UE of the setting information on the uplink
signal for measurement. The method for notifying the UE of the
adjustment value .alpha. may be applied to the notification method.
Examples of the setting information on the uplink signal for
measurement include the scheduling information on the uplink
signal. The examples also include the sequence number information
on reference signals when the reference signals are used. The
examples also include the CS information on ZC sequences when the
ZC sequences are used. The examples also include orthogonal code
information when the orthogonal codes are used.
[1018] The serving TRP may notify the UE of an instruction for
transmitting the uplink signal for measurement. The instruction
method includes instructing periodic or aperiodic transmission of
the uplink signal for measurement. The method for notifying the UE
of the adjustment value .alpha. may be applied to the notification
of this instruction. Since the notification via the L1/L2 signaling
can expedite a response, the time from the instruction to the
transmission of the uplink signal for measurement can be shortened
for the UE. This enables operations with low latency.
[1019] The serving TRP may notify the UE of two or more pieces of
information from among the adjustment value .alpha., the setting
information on the uplink signal for measurement, and instruction
information for transmitting the uplink signal for measurement
together. For example, the serving TRP notifies the UE of the
sequence number information and the CS information in the setting
information on the uplink signal for measurement first, and then
notifies together the scheduling information, the adjustment value
.alpha., and an instruction for transmitting the uplink signal for
measurement in the setting information on the uplink signal for
measurement. Consequently, the optimal adjustment value .alpha. can
be notified to the UE upon instruction of the uplink signal for
measurement.
[1020] FIGS. 58 to 60 illustrate an example sequence for setting an
adjustment value for the uplink transmission timing according to
the fourth embodiment. FIGS. 58 and 59 are connected across a
location of a border BL16. FIGS. 59 and 60 are connected across a
location of a border BL17. Here, the eNB sets a PRACH configuration
common among the TRPs in a cell.
[1021] In Step ST5501 to Step ST5505, the eNB notifies each of the
TRPs in the cell of the PRACH configuration common in the cell from
a node of the eNB with a function of setting the PRACH
configuration. In Step ST5506, the TRP 3 that is the serving TRP of
the UE 1 notifies the UE 1 of the PRACH configuration common among
the TRPs in the cell. The PRACH configuration may be included in
the system information to be broadcast.
[1022] In Step ST5507, the UE 1 determines the uplink access.
[1023] In Step ST5508, the UE 1 transmits the PRACH using the PRACH
configuration received in Step ST5506. Although the UE 1 transmits
the PRACH to the TRP 3, the UE 1 also transmits the PRACH to the
TRP 1, the TRP 2, the TRP 4, and the TRP 5 that are the neighboring
TRPs in Step ST5509, Step ST5510, Step ST5511, and Step ST5512,
respectively.
[1024] The TRP 3, and the TRP 1, the TRP 2, the TRP 4, and the TRP
5 that are the neighboring TRPs receive the PRACH using the PRACH
configuration common among the TRPs in the cell. Upon receipt of
the PRACH from the UE 1, the TRP 1 to the TRP 5 derive T1 to T5
that are radio propagation times each between the UE 1 and the
corresponding one of the TRP 1 to the TRP 5 in Step ST5513 to Step
ST5517, respectively.
[1025] In Step ST5518, Step ST5519, Step ST5520, Step ST5521, and
Step ST5522, the TRP 5, the TRP 4, the TRP 3, the TRP 2, and the
TRP 1 notify a node of the eNB with a function of deriving the TA
and the adjustment value of T5, T4, T3, T2, and T1,
respectively.
[1026] In Step ST5523, the node of the eNB with the function of
deriving the TA and the adjustment value derives TA3 that is timing
advance between the UE and the TRP 3 and the adjustment value
.alpha., using T3 of the TRP 3, and T1, T2, T4, and T5 of the
neighboring TRPs.
[1027] In Steps ST5524 and ST5525, the node of the eNB with the
function of deriving the TA and the adjustment value notifies,
through the TRP 3, the UE 1 of the TA3 and the adjustment value
.alpha. that have been derived. The RA response may be used for
notifying the TA3 and the adjustment value .alpha.. This enables
the earlier setting of the TA and the adjustment value .alpha..
[1028] In Step ST5526, the UE 1 derives uplink transmission timings
using the TA3 and the adjustment value .alpha. that have been
notified. Here, the uplink transmission timings of two types are
derived. One of them is the uplink transmission timing that is used
for transmitting the uplink signal not for measurement. The other
is the uplink transmission timing that is used for transmitting the
uplink signal for measurement. The uplink signal for measurement
may be an uplink signal that can be received by the neighboring
TRPs.
[1029] The uplink transmission timing that is used for transmitting
the uplink signal not for measurement is derived using the TA3. The
uplink transmission timing that is used for transmitting the uplink
signal for measurement is derived using the TA3 and the adjustment
value .alpha.. The uplink transmission timing may be derived
according to the methods previously disclosed.
[1030] In Step ST5527 to Step ST5532, the UE 1 performs the RRC
connection processes for the eNB through the TRP 3.
[1031] In Steps ST5527 and ST5528, the UE 1 notifies the eNB of an
RRC connection Request message through the TRP 3.
[1032] In Steps ST5529 and ST5530, the eNB notifies the UE 1 of an
RRC Connection setup message through the TRP 3.
[1033] In Steps ST5531 and ST5532, the UE 1 notifies the eNB of an
RRC Connection setup complete message through the TRP 3.
[1034] The UE 1 transmits the uplink signal with the uplink
transmission timing that is used for transmitting the uplink signal
not for measurement and that has been derived in Step ST5526,
starting from the notification of the RRC connection Request
message in Step ST5527.
[1035] In Step ST5533, a node of the eNB with a function of
performing a moving process sets the uplink signal for measurement
to the UE 1. The uplink signal for measurement in an RRC connected
state may be set.
[1036] In Steps ST5534 and ST5535, the eNB notifies the UE 1 of the
setting of the uplink signal for measurement. The notification may
be made via the UE-dedicated signaling. For example, the RRC
signaling may be used.
[1037] In Step ST5536, the node of the eNB with the function of
performing the moving process determines an instruction for
transmitting the uplink signal for measurement for the UE 1.
[1038] In Steps ST5537 and ST5538, the eNB notifies the UE 1 of the
instruction for transmitting the uplink signal for measurement. The
notification may be made via the UE-dedicated signaling. For
example, the L1/L2 control signaling may be used.
[1039] Upon receipt of the setting of the uplink signal for
measurement and the instruction for transmitting the uplink signal
for measurement, the UE sets the notified uplink signal for
measurement in Step ST5539. In Step ST5540, the UE 1 transmits the
uplink signal for measurement to the TRP 3. The UE 1 uses the
uplink transmission timing that is used for transmitting the uplink
signal for measurement and that has been derived in Step ST5526 to
transmit the uplink signal for measurement.
[1040] Although the UE 1 transmits the uplink signal for
measurement to the TRP 3, the UE 1 also transmits the uplink signal
for measurement to the TRP 1, the TRP 2, the TRP 4, and the TRP 5
that are the neighboring TRPs in Step ST5541, Step ST5542, Step
ST5543, and Step ST5544, respectively.
[1041] In Step ST5547, Step ST5545, Step ST5546, Step ST5548, and
Step ST5549, the TRP 3, and the TRP 1, the TRP 2, the TRP 4, and
the TRP 5 that are the neighboring TRPs, respectively, receive the
uplink signal for measurement transmitted from the UE 1.
[1042] Since the UE 1 uses, in Step ST5540, the uplink transmission
timing that is used for transmitting the uplink signal for
measurement using the adjustment value .alpha. to transmit the
uplink signal for measurement, the TRP 3, and the TRP 1, the TRP 2,
the TRP 4, and the TRP 5 that are the neighboring TRPs can receive
and demodulate the uplink signal for measurement. Thus, the uplink
signal from the UE 1 can be measured.
[1043] In Step ST5552, Step ST5550, Step ST5551, Step ST5553, and
Step ST5554, the TRP 3, and the TRP 1, the TRP 2, the TRP 4, and
the TRP 5 that are the neighboring TRPs, respectively, derive
measurement results of the uplink signal for measurement
transmitted from the UE 1. Examples of the measurement results of
the uplink signal include the received power, the reception
quality, and the SINR of a reference signal.
[1044] In Step ST5555, Step ST5556, Step ST5557, Step ST5558, and
Step ST5559, the TRP 5, the TRP 4, the TRP 3, the TRP 2, and the
TRP 1, respectively, notify the node of the eNB with the function
of performing the moving process of the results of the uplink
signal of the UE 1 measured by its own TRP.
[1045] In Step ST5560, the node of the eNB with the function of
performing the moving process performs movement determination.
Specifically, the node of the eNB with the function of performing
the moving process judges and determines whether the TRP connected
to the UE 1 is moved and to which TRP the UE 1 is moved, using the
results of the uplink signal of the UE 1 measured by the TRPs which
have been notified.
[1046] The node of the eNB with the function of performing the
moving process that has determined to move the TRP for the UE 1 in
Step ST5560 notifies the UE 1 of an instruction for changing the
TRP through the TRP 3 in Steps ST5561 and ST5562. The instruction
may be notified together with the identifier of the changed TRP.
Here, the TRP is changed to the TRP 1. The TA of the changed TRP
may be notified together with the instruction for changing the TRP.
The adjustment value .alpha. at the changed TRP may be notified.
The notification may be made via the UE-dedicated signaling. For
example, the RRC signaling may be used.
[1047] Upon receipt of the notification of the instruction for
changing the TRP, the UE 1 makes the setting for changing the TRP
for communication in Step ST5563. Here, the TRP 3 is changed to the
TRP 1 in the setting for communication. In Step ST5564 and Step
ST5565, the UE 1 communicates with the eNB through the TRP 1.
[1048] Consequently, the neighboring TRPs can receive and
demodulate the uplink signal for measurement from the UE to enable
the uplink measurement. Thus, the node of the eNB with the function
of performing the moving process can judge and determine whether
the UE 1 is moved to the TRP and to which TRP the UE 1 is
moved.
[1049] Measuring not the downlink signal in the UE but the uplink
signal on the NW side enables the moving process to be performed
earlier since the measurement on the NW side, which can reduce the
latency in the moving process.
[1050] The nodes with the respective functions in the eNB may be
different from each other, though setting the PRACH configuration
common among the TRPs in the cell, deriving the TA and the
adjustment value .alpha., setting the uplink signal for
measurement, the instruction for transmitting the uplink signal for
measurement, and judging and determining the moving process are
similarly described as the processes of the eNB in FIGS. 58 to 60.
For example, a part of the nodes may be the same, and another part
thereof may be different.
[1051] For example, the TRP or the DU may judge and determine the
moving process, and a node of the eNB that is not the TRP may
perform the other processes. The measurement result may be notified
between the TRPs or between the DUs. Consequently, the latency in
the moving process can be further reduced.
[1052] Not only the serving TRP but also the neighboring TRPs can
receive the uplink signal from the UE with application of the
methods disclosed in the fourth embodiment. Each of the TRPs can
receive the uplink signal transmitted from the UE in the normal
reception duration of the uplink signal. Since each of the TRPs can
receive and measure the uplink signal for measurement from the UE,
it can omit the measurement of the downlink signal. Thus, the need
for the reference signal for measuring the downlink signal can be
eliminated, and the radio resources to be spent for the reference
signal can be reduced. Thus, the spare radio resources can be used
for data communication. This can increase the use efficiency of the
radio resources.
[1053] Application of a measurement value of the uplink signal on
the NW side in the movement between the TRPs or between the DUs
eliminates the need for transmitting the measurement result to the
NW side, as in the case when a measurement value of the downlink
signal is used. This enables the NW side to determine the TRP or
the DU at a destination earlier and to determine the moving
process. Thus, the movement with low latency is possible. In 5G,
the TRP or the DU is assumed to configure a narrow coverage. Since
the movement with low latency is possible under such a
circumstance, the communication can be continued.
First Modification of Fourth Embodiment
[1054] The first modification will disclose another method for
solving the problems disclosed in the fourth embodiment.
[1055] The CP is added to the uplink signal that can be received by
the neighboring TRPs. The CP to be added will be referred to as a
guard CP (gCP). The gCP is added consecutively to the uplink
signal. The method for configuring the gCP is the same as that for
the conventional CP. When transmitting the uplink signal that can
be received by the neighboring TRPs, the UE adds the gCP to the
uplink signal to transmit the uplink signal.
[1056] Increase in an uplink signal duration with the addition of
the gCP can increase an uplink signal duration during which the
uplink signal can be received and which is included in the uplink
signal reception duration in each TRP. Thus, the TRP can make
measurement with high precision.
[1057] The gCP length may be statically predetermined in, for
example, a standard. Alternatively, the serving TRP may
semi-statically or dynamically notify the UE of the gCP length. The
methods for notifying the UE of the adjustment value .alpha. that
are disclosed in the fourth embodiment may be appropriately applied
to a method for notifying the UE of the gCP length.
[1058] Even with the addition of the gCP, the TA may have an
adjustment value. The TA for the UE that transmits the uplink
signal for measurement may have an adjustment value. The adjustment
value is denoted by .beta.. The UE delays the uplink transmission
timing by the adjustment value .beta. for the TA set with the
serving TRP. In other words, the UE sets TA-.beta. as the TA
including the adjustment value.
[1059] The methods for setting and notifying the adjustment value
.alpha. that are disclosed in the fourth embodiment may be
appropriately applied to methods for setting the adjustment value
.beta. and notifying the UE of the adjustment value .beta..
Provision of the adjustment value .beta. in setting the uplink
transmission timing of the UE enables adjustment of a duration
during which the serving TRP and the other TRPs actually receive
the uplink signal transmitted from the UE, specifically, a duration
of the uplink signal in the uplink signal reception duration Rw.
Setting the appropriate adjustment value .beta. enables not only
the serving TRP but also the other TRPs to receive the uplink
signal transmitted from the UE. The TA may be a value obtained by
including an adjustment value in the conventional TA, without
separately providing the adjustment value. Even in such a case, the
same advantages can be produced.
[1060] FIG. 61 illustrates the reception timing by the TRPs when
the adjustment value .beta. is provided for the uplink signal which
is transmitted from the UE 1 and to which the gCP has been added.
Since FIG. 61 is similar to FIG. 56, the differences will be mainly
described.
[1061] The TA is preset between the UE 1 and the serving TRP. The
adjustment value .beta. is set to the UE 1 in consideration of the
radio propagation times with the serving TRP and the neighboring
TRPs, here, the TRP 1 to the TRP 5. The UE 1 adds the gCP to the
uplink signal that can be received by the neighboring TRPs. For
example, the gCP is added before the uplink signal, in addition to
the structure of the uplink signal disclosed in FIG. 57. The UE 1
transmits, using the TA3 and the adjustment value .beta. that have
been set, the uplink signal to which the gCP has been added earlier
than the downlink reception timing by TA3-.beta..
[1062] Here, the arrival timing at the TRP 3 of the uplink signal
from the UE 1 to which the gCP has been added is later than the
reception timing of the uplink signal at the TRP 3 by the
adjustment value .beta..
[1063] In contrast, the arrival timing at the TRP 1 of the uplink
signal from the UE 1 to which the gCP has been added is earlier
than the reception timing of the uplink signal by T3-T1. However,
the arrival timing is later than the arrival timing using only the
conventional TA3 by the adjustment value .beta.. An uplink signal
duration Tw to which the gCP has been added is increased by the
gCP. Thus, the duration during which the uplink signal from the UE
1 can be received by the TRP 1 is increased by gCP+.beta..
[1064] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 2 is earlier than the reception timing of the
uplink signal by T3-T2. However, the arrival timing is later than
the arrival timing using only the conventional TA3 by the
adjustment value .beta.. The uplink signal duration Tw to which the
gCP has been added is increased by the gCP. Thus, the duration
during which the uplink signal from the UE 1 can be received by the
TRP 2 is increased by gCP+.beta..
[1065] The arrival timing of the uplink signal from the UE 1 at the
TRP 4 is later than the reception timing of the uplink signal by
T4-T3. The arrival timing is later than the arrival timing using
only the conventional TA3 by the adjustment value .beta.. Thus, the
duration during which the uplink signal from the UE 1 can be
received by the TRP 4 is decreased by the adjustment value
.beta..
[1066] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 5 is later than the reception timing of the uplink
signal by T5-T3. Since the arrival timing is later than the arrival
timing using only the conventional TA3 by the adjustment value
.beta., the duration during which the uplink signal from the UE 1
can be received by the TRP 4 is decreased by the adjustment value
.beta..
[1067] Setting the adjustment value .beta. to the UE in such a
manner enables adjustment of the arrival timing of the uplink
signal from the UE at the neighboring TRPs. The reception duration
of the uplink signal from the UE by the neighboring TRPs can also
be adjusted. Thus, setting the appropriate adjustment value .beta.
enables not only the serving TRP but also the neighboring TRPs to
receive the uplink signal transmitted from the UE.
[1068] According to the methods disclosed in the first
modification, the addition of the gCP to the uplink signal can
increase the uplink signal duration during which the uplink signal
can be received by the serving TRP and the neighboring TRPs more
than that according to the fourth embodiment. For example in FIG.
61, the duration during which the uplink signal can be actually
received by the TRP 1 and the TRP 2 is increased more than that
according to the fourth embodiment. Thus, each of the TRPs can
receive the uplink signal with high precision. If the uplink signal
is an uplink signal for measurement, each of the TRPs can measure
the uplink signal with high precision.
[1069] Although the gCP is added before the uplink signal in FIG.
61, the gCP may be added after the uplink signal, not limited to
before the uplink signal. Alternatively, the gCP may be divided
into two to be added before and after the uplink signal. The method
for configuring the gCP when the gCP is added before or after the
uplink signal or added before and after the uplink signal may be
the same as that for the conventional CP.
[1070] The transmission of the uplink signal from the UE may span
the next subframe, depending on a portion corresponding to the
added gCP, or the adjustment value R. Here, the eNB may perform a
method for, for example, preventing scheduling in the next subframe
for the UE, etc. Consequently, the uplink signal which spans the
next subframe and to which the gCP has been added can be
transmitted.
Second Modification of Fourth Embodiment
[1071] In the first modification of the fourth embodiment, the gCP
is added to the uplink signal that can be received by the
neighboring TRPs. Depending on the setting of the adjustment value
.beta., addition of the gCP may require a gap before or after the
uplink signal. This is because an overlap between the timing for
adding the gCP to the uplink signal and transmitting the uplink
signal and for example, the reception timing of downlink data to be
received before the uplink signal in the UE is prevented.
[1072] Conventionally, when reception of the downlink data is
followed by transmission of an uplink signal, a gap is formed in
between. However, when an additional uplink signal exists before or
after the uplink signal, a gap is not provided in between. Thus,
when the gCP has been set to a configuration in which the
additional uplink signal exists before or after the uplink signal,
a new gap will waste the radio resources.
[1073] The second modification will disclose a method for solving
such a problem.
[1074] When uplink signals are consecutively configured before or
after the uplink signal that can be received by the neighboring
TRPs, the gCP is set to a part of the consecutive uplink
signals.
[1075] FIG. 62 illustrates an example of setting the gCP to a part
of the consecutive uplink signals. FIG. 62 illustrates a case where
each of the uplink signals consists of the CP and data such as a
sequence. The uplink signals are consecutively configured before
and after the uplink signal that can be received by the neighboring
TRPs. FIG. 62 illustrates an example of setting the gCP to a part
of the prior uplink signal.
[1076] The gCP is set to a part of the uplink signals consecutively
configured before the uplink signal that can be received by the
neighboring TRPs. The gCP length is less or equal to the CP length.
Although data such as the sequence is reduced from the prior uplink
signal configured before the uplink signal that can be received by
the neighboring TRPs, the CP exists in the prior uplink signal.
Thus, the serving TRP receives and demodulates the data such as the
sequence including the CP, and thus can obtain the data such as the
sequence.
[1077] The gCP length may be shortened to increase a probability of
accurately receiving and demodulating the uplink signals
consecutively configured before the uplink signal that can be
received by the neighboring TRPs. Setting the gCP length according
to radio propagation environments between the UE and the serving
TRP and between the UE and the neighboring TRPs enables the serving
TRP to obtain the uplink signals and also enables the neighboring
TRPs to obtain the uplink signal that can be received by the
neighboring TRPs.
[1078] FIG. 63 illustrates another example of setting the gCP to a
part of the consecutive uplink signals. FIG. 63 illustrates a case
where each of the uplink signals consists of CPs and data such as a
sequence, and the CPs are added before and after the data such as
the sequence. The uplink signals are consecutively configured
before and after the uplink signal that can be received by the
neighboring TRPs. FIG. 63 illustrates an example of changing, into
the gCP, the CP at the end of the prior uplink signal.
[1079] The CP at the end of the uplink signal consecutively
configured before the uplink signal that can be received by the
neighboring TRPs is changed into the gCP. Although the CP is
reduced from the prior uplink signal configured before the uplink
signal that can be received by the neighboring TRPs, the data such
as the sequence and the CP at the beginning exist in the prior
uplink signal. Thus, the serving TRP receives and demodulates the
data such as the sequence including the CP, and thus can obtain the
data such as the sequence. The same advantages as those in the
example of FIG. 62 can be produced.
[1080] The same holds true for another case where each of the
uplink signals consists of the CP and data such as a sequence, and
the CP is added after the data such as the sequence. A part or the
entirety of the CP at the end of the prior uplink signal may be
changed into the gCP. The same advantages as those in the
previously disclosed examples will be produced.
[1081] With application of the methods disclosed in the second
modification, the gCP eliminates the need for newly configuring a
gap even in the presence of an additional uplink signal before or
after the uplink signal. This can suppress decrease in the use
efficiency of the radio resources.
Third Modification of Fourth Embodiment
[1082] In the fourth embodiment to the second modification of the
fourth embodiment, the uplink signal from the UE may span the next
subframe in a TRP whose radio propagation time from the UE is long.
In the next subframe, the TRP transmits the downlink signal, and
the UEs being served by the TRP receive the downlink signal. Thus,
when the uplink signal from the UE spans the next subframe, the
uplink signal from the UE interferes with reception of the downlink
signal by the UEs being served by the TRP.
[1083] The third modification will disclose another method for
solving the problems disclosed in the fourth embodiment and further
solving the aforementioned problem.
[1084] A guard time (hereinafter referred to as a "GT") is provided
for the reception timing of the uplink signal that can be received
by the neighboring TRPs. A GT is added consecutively to the
reception timing of the uplink signal. In the GT, no other signals
are transmitted or received. Each of the TRPs receives the uplink
signal for a reception duration of the uplink signal that includes
the GT.
[1085] Consequently, the uplink signal reception duration in each
of the TRPs can be increased by the GT. Thus, even when the uplink
signal reception timing in each of the TRPs is prior to or
subsequent to the normal uplink signal reception timing, the TRP
can receive the uplink signal. Consequently, the TRP can make
measurement with high precision.
[1086] The structure of the GT may be statically predetermined in,
for example, a standard. Alternatively, the serving TRP may
semi-statically or dynamically notify the UE of the structure of
the GT. The methods for notifying the UE of the adjustment value
.alpha. that are disclosed in the fourth embodiment may be
appropriately applied to a method for notifying the UE of the
structure of the GT.
[1087] Even when the GT is provided, the TA may have an adjustment
value. The TA for the UE that transmits the uplink signal for
measurement may have an adjustment value. The adjustment value is
denoted by .gamma.. The UE delays the uplink transmission timing by
the adjustment value .gamma. for the TA set with the serving TRP.
In other words, the UE sets TA+.gamma. as the TA including the
adjustment value.
[1088] The methods for setting and notifying the adjustment value
.alpha. that are disclosed in the fourth embodiment may be
appropriately applied to methods for setting the adjustment value
.gamma. and notifying the UE of the adjustment value .gamma..
Provision of the adjustment value .gamma. in setting the uplink
transmission timing of the UE enables adjustment of a duration
during which the serving TRP and the other TRPs actually receive
the uplink signal transmitted from the UE, specifically, a duration
of the uplink signal in the uplink signal reception duration Rw.
Setting the appropriate adjustment value .gamma. enables not only
the serving TRP but also the other TRPs to receive the uplink
signal transmitted from the UE. The TA may be a value obtained by
including an adjustment value in the conventional TA, without
separately providing the adjustment value. Even in such a case, the
same advantages can be produced.
[1089] The duration for one subframe is predetermined. Thus,
durations for the other signals need to be reduced when the GT is
provided. The following (1) and (2) will be disclosed as specific
examples of the reduction method:
[1090] (1) a duration for a gap is reduced; and
[1091] (2) a duration for the DL is reduced.
[1092] Since the duration for the gap is reduced in (1), the
duration for data can be maintained. Thus, reduction in the data
transmission rate can be suppressed. This is effective when
suppressing reduction in the data transmission rate is desired.
[1093] Since the duration for the DL is reduced in (2), the
duration for the gap can be maintained. Since the duration for the
gap is determined from, for example, the cell coverage and the
demodulation performance of the UE, the duration for the gap is
sometimes desirably fixed. The method (2) is effective in such a
case.
[1094] The duration described in the aforementioned example may be
replaced with a symbol. Since the number of symbols in one subframe
is predetermined, symbols of the other signals are reduced when the
GT is provided. The specific examples may include reducing a symbol
of a gap and reducing a symbol of the DL, each of which can produce
the same advantages.
[1095] FIG. 64 illustrates the timing of receiving, by the TRPs,
the uplink signal transmitted from the UE 1 when the adjustment
value .gamma. is provided in a structure with GTs. Since FIG. 64 is
similar to FIG. 56, the differences will be mainly described.
[1096] In addition to the uplink signal reception duration
disclosed in the fourth embodiment, the GTs are provided in a TRP.
The duration of the GTs is denoted by Ta+Tb. The TRP sets the
uplink signal reception duration including the duration of the GTs
as a new uplink signal reception duration Rw. Thus, the uplink
signal reception duration in the TRP is longer than the
conventional uplink signal reception duration by the GTs.
[1097] The TA is preset between the UE 1 and the serving TRP. The
adjustment value .gamma. is preset to the UE 1 in consideration of
the GTs and the radio propagation times with the serving TRP and
the neighboring TRPs, here, the TRP 1 to the TRP 5. The UE 1
transmits, using the TA3 and the adjustment value .gamma. that have
been set, the uplink signal earlier than the downlink reception
timing by TA3+.gamma..
[1098] Here, the arrival timing of the uplink signal from the UE 1
at the TRP 3 is earlier than the reception timing of the uplink
signal at the TRP 3 by the adjustment value .gamma.. However, since
the GTs are provided, reception of the uplink signal from the UE 1
can be started earlier by the shortened time through setting each
of the GTs to an appropriate value. Thus, the TRP 3 can receive the
entirety of the uplink signal from the UE 1.
[1099] The arrival timing of the uplink signal from the UE 1 at the
TRP 1 is earlier than the reception timing of the uplink signal by
T3-T1. Moreover, the arrival timing is earlier than the arrival
timing using only the conventional TA3 by the adjustment value
.gamma.. However, since the GTs are provided, reception of the
uplink signal from the UE 1 can be started earlier by the shortened
time through setting each of the GTs to an appropriate value. Thus,
the TRP 1 can receive the entirety of the uplink signal from the UE
1.
[1100] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 2 is earlier than the reception timing of the
uplink signal by T3-T2. Moreover, the arrival timing is earlier
than the arrival timing using only the conventional TA3 by the
adjustment value .gamma.. However, since the GTs are provided,
reception of the uplink signal from the UE 1 can be started earlier
by the shortened time through setting each of the GTs to an
appropriate value. Thus, the TRP 2 can receive the entirety of the
uplink signal from the UE 1.
[1101] The arrival timing of the uplink signal from the UE 1 at the
TRP 4 is later than the reception timing of the uplink signal by
T4-T3. However, the arrival timing is earlier than the arrival
timing using only the conventional TA3 by the adjustment value
.gamma.. Since the GTs are provided, reception of the uplink signal
from the UE 1 can be started earlier by the shortened time through
setting each of the GTs to an appropriate value. Thus, the TRP 4
can receive the entirety of the uplink signal from the UE 1.
[1102] Similarly, the arrival timing of the uplink signal from the
UE 1 at the TRP 5 is later than the reception timing of the uplink
signal by T5-T3. However, the arrival timing is earlier than the
arrival timing using only the conventional TA3 by the adjustment
value .gamma.. Since the GTs are provided, reception of the uplink
signal from the UE 1 can be started earlier by the shortened time
through setting teach of the GTs to an appropriate value. Thus, the
TRP 5 can receive the entirety of the uplink signal from the UE
1.
[1103] Setting the adjustment value .gamma. to the UE in such a
manner enables adjustment of the arrival timing of the uplink
signal from the UE at the neighboring TRPs. The reception duration
of the uplink signal from the UE by the neighboring TRPs can also
be adjusted. Thus, setting the appropriate adjustment value .beta.
enables not only the serving TRP but also the neighboring TRPs to
receive the uplink signal transmitted from the UE.
[1104] According to the method disclosed in the third modification,
the GTs are added consecutively to the reception timing of the
uplink signal, and each of the TRPs receives the uplink signal for
the reception duration of the uplink signal that includes the GTs.
Thus, the uplink signal duration during which the uplink signal can
be received by the serving TRP and the neighboring TRPs can be
increased more than that according to the fourth embodiment. Thus,
each of the TRPs can receive the uplink signal with high precision.
If the uplink signal is an uplink signal for measurement, each of
the TRPs can measure the uplink signal with high precision.
[1105] Although the GTs are added before and after the uplink
signal in FIG. 64, the GT may be added only before or after the
uplink signal. When the GT is added after the uplink signal, the
subsequent subframe may have a GT. Here, each of the TRPs receives
the uplink signal from the UE for a duration until the GT in the
subsequent subframe.
[1106] When the normal uplink signal reception timing is at the end
of a subframe, a GT may be added front. The GT may be added in an
appropriate subframe. Since the GT can be configured without
changing the other subframe structures, the communication can be
established in the normal subframe structure without omitting any
signals to be mapped to the other subframes. Thus, the complexity
in the control can be suppressed both on the NW side and on the UE
side.
[1107] The uplink signal for measurement may be the SRS in the NR.
The methods disclosed in the fourth embodiment to the third
modification of the fourth embodiment may be applied to the SRS.
Since the neighboring TRPs can receive the SRS in the NR, the SRS
can be used as the uplink signal for measurement. The SRS can be
used as a signal for the moving process.
[1108] The uplink signal for measurement may be an uplink Ack/Nack
signal in response to a downlink signal. A measurement function is
provided for the uplink Ack/Nack signal. For example, the Ack/Nack
signal may be configured using an uplink RS. Since functions of the
Ack/Nack and the RS are multiplexed, the methods for multiplexing
the Ack/Nack with the SRS that are disclosed in the second
modification of the third embodiment may be applied. Consequently,
a node on the NW side can measure the uplink signal from the UE
with transmission of Ack/Nack in response to the downlink data,
even without transmission of the uplink data.
[1109] Although the fourth embodiment to the third modification of
the fourth embodiment describe the methods for enabling the
neighboring TRPs and the neighboring DUs to receive the uplink
signal from the UE, the uplink signal may not be received by the
TRPs and the DUs. The methods may be applied to devices or nodes to
be operated at different installation points. Consequently, the
uplink signal from the UE can be received and measured at the
different installation points.
[1110] For example, the methods may be applied to cells.
Consequently, the neighboring cells can receive the uplink signal
from the UE. Alternatively, the methods may be applied to eNB s
Consequently, the neighboring eNB s can receive the uplink signal
from the UE. Alternatively, the methods may be applied to one or
more TRPs in the eNB where the UE is communicating and to one or
more TRPs in the neighboring eNBs. Consequently, the neighboring
TRPs in different eNBs can receive the uplink signal from the
UE.
[1111] The embodiments and the modifications are merely
illustrations of the present invention, and can be freely combined
within the scope of the present invention. Any constituent elements
of the embodiments and the modifications can be appropriately
modified or omitted. A subframe is an example time unit in
communication in the fifth-generation base station communication
system in the embodiments and the modifications. The process
described per subframe may be performed per TTI, per slot, or per
mini-slot in the embodiments and the modifications.
[1112] While the invention has been described in detail, the
foregoing description is in all aspects illustrative and not
restrictive. It is therefore understood that numerous modifications
and variations can be devised without departing from the scope of
the invention.
DESCRIPTION OF REFERENCES
[1113] 701 coverage of macro cell, 702 coverage of small cell, 703
user equipment (UE).
* * * * *
References