U.S. patent application number 16/064144 was filed with the patent office on 2019-01-03 for user terminal, radio base station and radio communication method.
This patent application is currently assigned to NTT DOCOMO, INC.. The applicant listed for this patent is NTT DOCOMO, INC.. Invention is credited to Hiroki Harada, Satoshi Nagata, Kazuki Takeda.
Application Number | 20190007942 16/064144 |
Document ID | / |
Family ID | 59089526 |
Filed Date | 2019-01-03 |
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United States Patent
Application |
20190007942 |
Kind Code |
A1 |
Takeda; Kazuki ; et
al. |
January 3, 2019 |
USER TERMINAL, RADIO BASE STATION AND RADIO COMMUNICATION
METHOD
Abstract
The present invention is designed so that communication is
carried out properly even when shortened TTIs are used. A user
terminal has a control section that controls communication using a
first transmission time interval (TTI) and a second TTI shorter
than the first TTI, and a transmission section that transmits
information related to processing capability. The control section
controls communication using the second TTI according to a timing
determined based on the information.
Inventors: |
Takeda; Kazuki; (Tokyo,
JP) ; Harada; Hiroki; (Tokyo, JP) ; Nagata;
Satoshi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NTT DOCOMO, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
59089526 |
Appl. No.: |
16/064144 |
Filed: |
December 22, 2016 |
PCT Filed: |
December 22, 2016 |
PCT NO: |
PCT/JP2016/088260 |
371 Date: |
June 20, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/1268 20130101;
H04W 72/0446 20130101; H04W 72/048 20130101; H04B 7/0413 20130101;
H04W 72/0413 20130101; H04L 5/0055 20130101; H04W 8/22
20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04B 7/0413 20060101 H04B007/0413; H04L 5/00 20060101
H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2015 |
JP |
2015-255030 |
Claims
1. A user terminal comprising: a control section that controls
communication using a first transmission time interval (TTI) and a
second TTI shorter than the first TTI; and a transmission section
that transmits information related to processing capability, and
the control section controls communication using the second TTI
according to a timing determined based on the information.
2. The user terminal according to claim 1, wherein the information
specifies processing time corresponding to at least one of a data
block size, an amount of resources, an m-ary modulation level and a
number of MIMO (Multi-Input Multi-Output) layers of downlink data,
in the user terminal.
3. The user terminal according to claim 1, wherein the information
specifies processing time corresponding to at least one of amount
of ACK/NACK information of an uplink control channel and an amount
of resources allocated to the uplink control channel.
4. The user terminal according to claim 1, wherein the control
section controls transmission of ACK/NACK feedback in response to
downlink data in the second TTI according to the timing.
5. The user terminal according to claim 1, wherein the information
specifies processing time corresponding to at least one of a data
block size of the uplink data and an amount of resources allocated
to the uplink shared channel, in the user terminal.
6. The user terminal according to claim 1, wherein the information
specifies processing time corresponding to at least one of an m-ary
modulation level of the uplink shared channel, a number of MIMO
(Multi-Input Multi-Output) layers of the uplink shared channel,
whether or not uplink control information (UCI) is multiplexed on
the uplink shared channel, and when the UCI is multiplexed, a
payload of the UCI, in the user terminal.
7. The user terminal according to claim 1, wherein the control
section controls the transmission of uplink data in the second TTI
according to the timing.
8. The user terminal according to claim 1, wherein the control
section controls communication in the first TTI when the timing is
not decided.
9. A radio base station comprising: a receiving section that
receives, from a user terminal that controls communication using a
first transmission time interval (TTI) and a second TTI shorter
than the first TTI, information related to processing capability of
the user terminal; and a control section that determining a timing
in the second TTI based on the information, and reports this timing
to the user terminal.
10. A radio communication method in a user terminal that controls
communication using a first transmission time interval (TTI) and a
second TTI shorter than the first TTI, the radio communication
method comprising: transmitting information related to processing
capability of the user terminal; and controlling communication
using the second TTI according to a timing determined based on the
information.
11. The user terminal according to claim 2, wherein the control
section controls transmission of ACK/NACK feedback in response to
downlink data in the second TTI according to the timing.
12. The user terminal according to claim 3, wherein the control
section controls transmission of ACK/NACK feedback in response to
downlink data in the second TTI according to the timing.
13. The user terminal according to claim 5, wherein the control
section controls the transmission of uplink data in the second TTI
according to the timing.
14. The user terminal according to claim 6, wherein the control
section controls the transmission of uplink data in the second TTI
according to the timing.
Description
TECHNICAL FIELD
[0001] The present invention relates to a user terminal, a radio
base station and a radio communication method in next-generation
mobile communication systems.
BACKGROUND ART
[0002] In the UMTS (Universal Mobile Telecommunications System)
network, the specifications of long term evolution (LTE) have been
drafted for the purpose of further increasing high speed data
rates, providing lower delays and so on (see non-patent literature
1). Also, the specifications of LTE-A (also referred to as
"LTE-advanced," "LTE Rel. 10," "Rel. 11" or "Rel. 12, ", etc.) have
been drafted for further broadbandization and increased speed
beyond LTE (also referred to as "LTE Rel. 8" or "Rel. 9"), and
successor systems of LTE (also referred to as, for example, "FRA"
(Future Radio Access), "5G" (5th generation mobile communication
system), "LTE Rel. 13," "Rel. 14," and so on) are under study.
[0003] Carrier aggregation (CA) to integrate multiple component
carriers (CC) is introduced in LTE Rel. 10/11 in order to achieve
broadbandization. Each CC is configured with the system bandwidth
of LTE Rel. 8 as one unit. In addition, in CA, multiple CCs under
the same radio base station (eNB: eNodeB) are configured in a user
terminal (UE: User Equipment).
[0004] Meanwhile, in LTE Rel. 12, dual connectivity (DC), in which
multiple cell groups (CG) formed by different radio base stations
are configured in a user terminal, is also introduced. Each cell
group is comprised of at least one cell (CC). Since multiple CCs of
different radio base stations are integrated in DC, DC is also
referred to as "inter-eNB CA."
[0005] Also, in LTE Rel. 8 to 12, frequency division duplex (FDD),
in which downlink (DL) transmission and uplink (UL) transmission
are made in different frequency bands, and time division duplex
(TDD), in which DL transmission and UL transmission are switched
over time and made in the same frequency band, are introduced.
[0006] In above LTE Rel. 8 to 12, the transmission time intervals
(TTIs) that are applied to DL transmission and UL transmission
between radio base stations and user terminals are configured to
one ms and controlled. TTIs in existing systems (LTE Rel. 8 to 12)
are also referred to as "subframes" "subframe durations", etc.
CITATION LIST
Non-Patent Literature
[0007] Non-Patent Literature 1: 3GPP TS 36.300 Rel. 8 Evolved
Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal
Terrestrial Radio Access Network (E-UTRAN); Overall description;
Stage 2''
SUMMARY OF INVENTION
Technical Problem
[0008] Meanwhile, future radio communication systems such as LTE
after Rel. 13 and 5G are expected to communicate a relatively small
amount of data in high frequency bands such as several tens of GHz,
as in IoT (Internet of Things), MTC (Machine Type Communication),
M2M (Machine To Machine) or the like is performed. When applying
communication methods of existing systems (LTE Rel. 8 to 12) (such
as one-ms transmission time intervals (TTIs)) to such a future
radio communication system, there is a possibility that sufficient
communication services cannot be provided.
[0009] Therefore, in future radio communication systems, it may be
possible to make communication using TTIs (hereinafter referred to
as "shortened TTIs") that are shorter than one-ms TTIs (hereinafter
referred to as "normal TTIs"). However, in this case, how to
control the communication method to use shortened TTIs is the
problem.
[0010] The present invention has been made in view of the above
points, and it is therefore an object of the present invention to
provide a user terminal, a radio base station, and a radio
communication method whereby appropriate communication can be
carried out even when shortened TTIs are used.
Solution to Problem
[0011] One aspect of the user terminal of the present invention
provides a user terminal that has a control section that controls
communication using a first transmission time interval (TTI) and a
second TTI shorter than the first TTI, and a transmission section
that transmits information related to processing capability, and,
in this user terminal, the control section controls communication
using the second TTI according to a timing determined based on the
information).
Technical Advantage of the Invention
[0012] According to the present invention, even when shortened TTIs
are applied, communication can be performed appropriately.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a diagram to illustrate an example configuration
of a normal TTI;
[0014] FIG. 2A is a diagram to illustrate a first configuration
example of a shortened TTI, and FIG. 2B is a diagram to illustrate
a second configuration example of a shortened TTI;
[0015] FIG. 3A is a diagram to explain an example in which a normal
TTI and a shortened TTI coexist in the same CC, FIG. 3B is a
diagram to explain carrier aggregation (CA) or dual connectivity
(DC) using a normal TTI and a shortened TTI, and FIG. 3C is a
diagram to explain an example in which normal TTIs are configured
in UL and shortened TTIs are configured in DL in the TDD
system;
[0016] FIG. 4A is a diagram to illustrate an example of the
uplink/downlink transmission/receiving timing where normal TTIs are
applied, and FIG. 4B is a diagram to explain the uplink/downlink
transmission/receiving timing of the first embodiment where
shortened TTIs are applied to FDD;
[0017] FIG. 5A is a diagram to explain the processing procedure in
the case where HARQ-ACK feedback in response to DL data is
transmitted via the PUCCH in the user terminal, and FIG. 5B is a
diagram to explain the process from scheduling of UL data to the
transmission of the UL data;
[0018] FIG. 6 is a diagram to explain processing in the user
terminal;
[0019] FIG. 7A is a diagram to explain a process in which the
HARQ-ACK feedback transmission timing in response to UL data is
configured by higher layer signaling in the third embodiment, and
FIG. 7B is a diagram to explain a process in which feedback timing
is not configured in the third embodiment;
[0020] FIG. 8A is a diagram to explain the process influenced by
TBS and PRB after decoding of downlink control signals in the user
terminal, and FIG. 8B is a diagram to explain the process
influenced by TBS and PRB after decoding of UL grants in the user
terminal;
[0021] FIG. 9 is a diagram to explain processing in the user
terminal;
[0022] FIG. 10A and FIG. 10B are diagrams to explain the UE
capability information which the user terminal reports to the
network in the fourth embodiment;
[0023] FIG. 11A and FIG. 11B are diagrams to explain the UE
capability information which the user terminal reports to the
network in the fourth embodiment;
[0024] FIG. 12A and FIG. 12B are diagrams to explain the UE
capability information which the user terminal reports to the
network in the fourth embodiment;
[0025] FIG. 13 is a diagram to illustrate an example of a schematic
structure of a radio communication system according to the present
embodiment;
[0026] FIG. 14 is a diagram to illustrate an example of an overall
structure of a radio base station according to present
embodiment;
[0027] FIG. 15 is a diagram to illustrate an example of a
functional structure of a radio base station according to present
embodiment;
[0028] FIG. 16 is a diagram to illustrate an example of an overall
structure of a user terminal according to present embodiment;
[0029] FIG. 17 is a diagram to illustrate an example of a
functional structure of a user terminal according to present
embodiment; and
[0030] FIG. 18 is a diagram to illustrate an example hardware
structure of a radio base station and a user terminal according to
the present embodiment.
DESCRIPTION OF EMBODIMENTS
[0031] FIG. 1 is a diagram to illustrate an example of a TTI
(normal TTI) in existing systems (LTE Rel. 8 to 12). As illustrated
in FIG. 1, a normal TTI has a time duration of one ms. A normal TTI
is also referred to as a "subframe," and is comprised of two time
slots. In existing systems, a normal TTI is a transmission time
unit of one channel-encoded data packet, and is the processing unit
of scheduling and link adaptation.
[0032] As illustrated in FIG. 1, when a normal cyclic prefix (CP)
is used in the downlink (DL), a normal TTI includes 14 OFDM
(Orthogonal Frequency Division Multiplexing) symbols (seven OFDM
symbols per slot). Each OFDM symbol has a time duration (symbol
duration) of 66.7 .mu.s, and a normal CP of 4.76 .mu.s is appended.
Since the symbol duration and the subcarrier period are in
reciprocal relationship to each other, the subcarrier period is 15
kHz when the symbol duration 66.7 .mu.s.
[0033] Also, when normal a cyclic prefix (CP) is used in the uplink
(UL), a normal TTI is configured to include 14 SC-FDMA (Single
Carrier Frequency Division Multiple Access) symbols (seven SC-FDMA
symbols per slot). Each SC-FDMA symbol has a time duration (symbol
duration) of 66.7 .mu.s, and a normal CP of 4.76 .mu.s is appended.
Since the symbol duration and the subcarrier period are in
reciprocal relationship to each other, the subcarrier period is 15
kHz when the symbol duration 66.7 .mu.s.
[0034] Incidentally, when an extended CP is used, a normal TTI may
include 12 OFDM symbols (or 12 SC-FDMA symbols). In this case, each
OFDM symbol (or each SC-FDMA symbol) has a time duration of 66.7
.mu.s, and an extended CP of 16.67 .mu.s is appended. Also, OFDM
symbols may be used in the UL. Hereinafter, when OFDM symbols and
SC-FDMA symbols are not distinguished, they will be collectively
referred to as "symbols."
[0035] Meanwhile, in future radio communication systems such as LTE
of Rel. 13 and later versions and 5G, a radio interface that is
suitable for a high frequency bands such as several tens of GHz,
and/or a radio interface that minimizes delay by reducing the
packet size are desired, so that communication with a relatively
small amount of data such as IoT (Internet of Things), MTC (Machine
Type Communication) and M2M (Machine To Machine) can be suitably
performed.
[0036] When TTIs of a shorter time duration than normal TTIs
(hereinafter referred to as "shortened TTIs") are used, the time
margin for processing (for example, encoding and decoding) in user
terminals and radio base stations increases, so that the processing
delay can be reduced. Also, when shortened TTIs are used, it is
possible to increase the number of user terminals that can be
accommodated per unit time (for example, one ms). For this reason,
for future radio communication system, a study is in progress to
use shortened TTIs, which are shorter than normal TTIs, as one
channel-encoded data packet transmission time unit and/or as the
scheduling or link adaptation processing unit.
[0037] Referring to FIGS. 2 and 3, shortened TTI will be explained.
FIGS. 2 provide diagrams to illustrate example configurations of
shortened TTIs. As illustrated in FIG. 2A and FIG. 2B, shortened
TTIs have a time duration (TTI duration) shorter than one ms. A
shortened TTI may be one TTI duration or multiple TTI durations,
whose multiples are one ms, such as 0.5 ms, 0.25 ms, 0.2 ms and 0.1
ms, for example. Alternatively, when a normal CP is used, a normal
TTI contains 14 symbols, so that one TTI duration or multiple TTI
durations, whose multiples are integral multiples of 1/14 ms, such
as 7/14 ms, 4/14 ms, 3/14 ms and 1/14 ms, may be used. Also, when
an extended CP is used, a normal TTI contains 12 symbols, so that
one TTI duration or multiple TTI durations, whose multiples are
integral multiples of 1/12 ms, such as 6/12 ms, 4/12 ms, 3/12 ms
and 1/12 ms, may be used. Also in shortened TTIs, as in
conventional LTE, whether to use a normal CP or use an extended CP
can be configured with higher layer signaling such as broadcast
information and RRC signaling. By this means, it is possible to
introduce shortened TTIs, while maintaining compatibility
(synchronization) with one-ms normal TTIs.
[0038] FIG. 2A is a diagram to illustrate a first example
configuration of shortened TTIs. As illustrated in FIG. 2A, in the
first example configuration, a shortened TTI is comprised of the
same number of symbols (here, 14 symbols) as a normal TTI, and each
symbol has a symbol duration shorter than the symbol duration of a
normal TTI (for example, 66.7 .mu.s).
[0039] As illustrated in FIG. 2A, when maintaining the number of
symbols in a normal TTI and shortening the symbol duration, the
physical layer signal configuration (arrangement of REs, etc.) of
normal TTIs can be reused. In addition, when maintaining the number
of symbols in a normal TTI, it is possible to include, in a
shortened TTI, the same amount of information (the same amount of
bits) as in a normal TTI. On the other hand, since the symbol time
duration differs from that of normal TTI symbols, it is difficult,
as illustrated in FIG. 2A, to frequency-multiplex a signal with
shortened TTIs and a signal with normal TTIs in the same system
band (or the cell, the CC, etc.).
[0040] Also, since the symbol duration and the subcarrier period
are each the reciprocal of the other, as illustrated in FIG. 2A,
when shortening the symbol duration, the subcarrier period is wider
than the 15-kHz subcarrier period of normal TTIs. When the
subcarrier period becomes wider, it is possible to effectively
suppress the inter-channel interference caused by the Doppler shift
when the user terminal moves and the communication quality
degradation due to phase noise in the receiver of the user
terminal. In particular, in high frequency bands such as several
tens of GHz, the deterioration of communication quality can be
effectively suppressed by expanding the subcarrier period.
[0041] FIG. 2B is a diagram to illustrate a second example
configuration of a shortened TTI. As illustrated in FIG. 2B, in the
second example configuration, a shortened TTI is comprised of a
smaller number of symbols than a normal TTI, and each symbol has
the same symbol duration (for example, 66.7 .mu.s) as a normal TTI.
For example, referring to FIG. 2B, if a shortened TTI is half the
time duration (0.5 ms) of a normal TTI, the shortened TTI is
comprised of half the symbols (here, seven symbols) of a normal
TTI.
[0042] As illustrated in FIG. 2B, when reducing the symbol duration
and reducing number of symbols, the amount of information (the
amount of bits) included in a shortened TTI can be reduced lower
than in a normal TTI. Therefore, the user terminal can perform the
receiving process (for example, demodulation, decoding, etc.) of
the information included in a shortened TTI in a shorter time than
a normal TTI, and therefore the processing delay can be shortened.
Also, since the shortened-TTI signal illustrated in FIG. 2B and a
normal-TTI signal can be frequency-multiplexed within the same
system band (or the cell, the CC, etc.), compatibility with normal
TTIs can be maintained.
[0043] Although FIG. 2A and FIG. 2B illustrate examples of
shortened TTIs assuming that a normal CP is applied (where a normal
TTI is comprised of 14 symbols), the configuration of shortened
TTIs is not limited to those illustrated in FIGS. 2A and 2B. For
example, when an extended CP is used, the shortened TTI of FIG. 2A
may be comprised of 12 symbols, and the shortened TTI of FIG. 2B
may be comprised of six symbols. A shortened TTI needs only be a
shorter time duration than a normal TTI, and the number of symbols
in the shortened TTI, the duration of symbols, the duration of the
CP and suchlike configurations can be determined freely.
[0044] Referring to FIG. 3, an example of the configuration of a
shortened TTI will be described. Future radio communication systems
may be configured so that both normal TTIs and shortened TTIs can
be configured in order to maintain compatibility with existing
systems.
[0045] For example, as illustrated in FIG. 3A, normal TTIs and
shortened TTIs may coexist in time in the same CC (frequency
field). To be more specific, shortened TTIs may be configured in
specific subframes (or specific radio frames) of the same CC. For
example, in FIG. 3A, shortened TTIs are configured in five
consecutive subframes in the same CC, and normal TTIs are
configured in the other subframes. Note that the number and
locations of subframes where shortened TTIs are configured are not
limited to those illustrated in FIG. 3A.
[0046] Also, carrier aggregation (CA) or dual connectivity (DC) may
be performed by integrating CCs with normal TTIs and CCs with
shortened TTIs, as illustrated in FIG. 3B. To be more specific,
shortened TTIs may be configured in specific CCs (to be more
specific, in the DL and/or the UL of particular CCs). For example,
in FIG. 3B, shortened TTIs are configured in the DL of a particular
CC and normal TTIs are configured in the DL and UL of another CC.
Note that the number and locations of CCs where shortened TTIs are
configured are not limited to those illustrated in FIG. 3B.
[0047] In the case of CA, shortened TTIs may also be configured in
specific CCs (the primary (P) cell and/or secondary (S) cells) of
the same radio base station. Meanwhile, in the case of DC,
shortened TTIs may be configured in specific CCs (P cell and/or S
cells) in the master cell group (MCG) formed by the first radio
base station, or shortened TTIs may be configured in specific CCs
(primary secondary (PS) cells and/or S cells) in a secondary cell
group (SCG) formed by a second radio base station.
[0048] As illustrated in FIG. 3C, shortened TTIs may be configured
in either the DL or the UL. For example, in FIG. 3C, a case is
illustrated in which, in a TDD system, normal TTIs are configured
in the UL and shortened TTIs are configured in the DL.
[0049] Also, specific DL or UL channels or signals may be assigned
to (configured in) shortened TTIs. For example, an uplink control
channel (PUCCH: Physical Uplink Control Channel) may be allocated
to normal TTIs, and an uplink shared channel (PUSCH: Physical
Uplink Shared Channel) may be allocated to shortened TTIs. In this
case, for example, the user terminal transmits the PUCCH in normal
TTIs and transmits the PUSCH in shortened TTIs.
[0050] In FIGS. 3, the user terminal configures (and/or detects)
the shortened TTIs based on implicit or explicit reporting from the
radio base station. Below, (1) an example of implicit reporting and
examples of explicit reporting using (2) broadcast information or
RRC (Radio Resource Control) signaling, (3) MAC (Medium Access
Control) signaling, and (4) PHY (Physical) signaling will be
explained.
[0051] (1) When implicit reporting is used, the user terminal may
configure shortened TTIs (including, for example, judging that the
communicating cell, channel, signal, etc. use shortened TTIs) based
on the frequency band (for example, a band for 5G, an unlicensed
band, etc.), the system bandwidth (for example, 100 MHz, etc.),
whether or not LBT (Listen Before Talk) is employed in LAA (License
Assisted Access), the type of data to be transmitted (for example,
control data, voice, etc.), the logical channel, the transport
block, the RLC (Radio Link Control) mode, the C-RNTI (Cell-Radio
Network Temporary Identifier) and so on. Also, when control
information (DCI) addressed to the subject terminal is detected in
a PDCCH mapped to the first one, two, three or four symbols in a
normal TTI and/or in a one-ms EPDCCH, the user terminal may judge
that the one ms where the PDCCH/EPDCCH are included is a normal
TTI, and, when control information (DCI) addressed to the subject
terminal is detected in a PDCCH/EPDCCH configured otherwise (for
example, a PDCCH mapped to symbols other than the first one to four
symbols in a normal TTI and/or an EPDCCH that is less than one ms),
the user terminal may then judge that a predetermined time period
including the PDCCH/EPDCCH is a shortened TTI. Here, the control
information (DCI) addressed to the subject terminal can be detected
based on the CRC check result of blind-decoded DCI.
[0052] (2) When broadcast information or RRC signaling (higher
layer signaling) is used, shortened TTIs may be configured based on
configuration information that is reported from the radio base
station to the user terminal via broadcast information or RRC
signaling. The configuration information indicates, for example,
which CCs and/or subframes are to be used as shortened TTIs, which
channels and/or signals are transmitted/received in shortened TTIs,
and so on. The user terminal configures shortened TTIs
semi-statically based on configuration information from the radio
base station. Note that mode switching between shortened TTIs and
normal TTIs may be performed in the RRC reconfiguration step or may
be performed in intra-cell handover (HO) in P cells or in the
removal/addition steps of CCs (S cells) in S cells.
[0053] (3) When MAC signaling (L2(Layer 2) signaling) is used,
shortened TTIs that are configured based on configuration
information reported through RRC signaling may be activated or
deactivated by MAC signaling. To be more specific, the user
terminal activates or de-activates shortened TTIs based on L2
control signals (for example, MAC control elements) from the radio
base station. The user terminal may be preconfigured with a timer
that indicates the activation period of shortened TTIs, by higher
layer signaling such as RRC signaling, and, if, after shortened
TTIs are activated by an L2 control signal, there is no UL/DL
allocation in the shortened TTIs for a predetermined period, the
shortened TTIs may be de-activated if. This shortened TTI
deactivation timer may count normal TTIs (one ms) as units, or
count shortened TTIs (for example, 0.25 ms) as units. Note that,
when the mode is switched between shortened TTIs and normal TTIs in
an S cell, the S cell may be de-activated once, or it may be
possible to consider that the TA (Timing Advance) timer has
expired. By this means, it is possible to provide a
non-communicating period when switching the mode.
[0054] (4) When PHY signaling (L1 (Layer 1) signaling) is used,
shortened TTIs that are configured based on configuration
information reported by RRC signaling may be scheduled by PHY
signaling. To be more specific, the user terminal detects shortened
TTIs based on information included in L1 control signals that are
received and detected (for example, a downlink control channel
(PDCCH (Physical Downlink Control Channel) or EPDCCH (Enhanced
Physical Downlink Control Channel), which hereinafter will be
referred to as "PDCCH/EPDCCH").
[0055] For example, it is assumed that control information (DCI)
for assigning transmission or reception in normal TTIs and
shortened TTIs includes different information elements, and, (4-1)
when the user terminal detects control information (DCI) including
an information element that assigns transmission and reception in
shortened TTIs, the user terminal identifies a predetermined time
period including the timing where the PDCCH/EPDCCH is detected as a
shortened TTI. The user terminal can blind-decode control
information (DCI) for assigning transmission or reception in both
normal TTIs and shortened TTIs in the PDCCH/EPDCCH. Alternatively,
(4-2) when the user terminal detects control information (DCI)
including an information element that assigns
transmission/reception in shortened TTIs, the user terminal may
identify a predetermined time period, in which the timing the PDSCH
or the PUSCH scheduled by the PDCCH/EPDCCH (downlink control
information (DCI) communicated in the PDCCH/EPDCCH) is
transmitted/received is included, as a shortened TTI.
Alternatively, (4-3) when the user terminal detects control
information (DCI) including an information element that assigns
transmission/reception in shortened TTIs, the user terminal may
identify a predetermined a predetermined time period, in which the
timing to transmit or receive retransmission control information
(also referred to as "HARQ-ACKs" (Hybrid Automatic Repeat
reQuest-Acknowledgements), "ACKs/NACKs," "A/Ns,", etc.) for the
PDSCH or the PUSCH scheduled by the PDCCH/EPDCCH (DCI communicated
in the PDCCH/EPDCCH) is included, as a shortened TTI.
[0056] Further, the user terminal may detect shortened TTIs based
on the state of the user terminal (for example, the idle state or
the connected state). For example, if the user terminal is in the
idle state, the user terminal may identify all the TTIs as normal
TTIs and blind-decode only the PDCCHs included in the first to
fourth symbols of the normal TTIs of one ms. Also, if the user
terminal is in the connected state, the user terminal may configure
(and/or detect) shortened TTIs based on the reporting of at least
one of (1) to (4) described above as examples.
[0057] As mentioned above, the main purpose of applying
(introducing) shortened TTIs is to increase the temporal margin for
processing (for example, encoding, decoding, etc.) in user
terminals and radio base stations, and realize reduction of
processing latency (latency reduction)). For example, latency in
the radio lower layer occurs by transmitting data, decoding that
data, and feeding back ACK). However, even if the above shortened
TTIs are applied on an as-is basis, sufficient processing latency
reduction cannot be achieved in some cases.
[0058] So-called processing latency reduction focuses on the
following points:
[0059] (1) Shorten the time it takes to send HARQ-ACK in response
to DL data (HARQ RTT (Round Trip Time)).
[0060] Such reduction of processing latency is realized by the user
terminal quickly decoding DL data and quickly generating HARQ-ACK).
Note that RTT refers to the time it takes for a response to be
returned after transmitting a signal or data to a communicating
party.
[0061] (2) Shorten the time from the scheduling of UL data to the
transmission of the UL data.
[0062] Such reduction of processing latency is realized by the user
terminal decoding UL grant quickly and encoding UL data
quickly.
[0063] (3) Shorten the time from transmission of UL data to
HARQ-ACK feedback.
[0064] Such reduction of processing latency is realized by the
network (for example, radio base station) quickly decoding UL data
and quickly generating HARQ-ACK.
[0065] When normal TTIs are applied in the case of FDD for the
above three points, it is stipulated that transmission or reception
operation is performed four ms later (=four TTIs). Further, in the
case of TDD, it is specified that transmission or reception
operation is performed (4+k) ms later (=(4+k) TTIs). Note that the
value of k depends on the TDD UL-DL configuration and the subframe
index.
[0066] The inventors of the present invention have come up with the
idea of applying shortened TTIs to the above three points.
First Embodiment
[0067] First, the first embodiment will be described. In the first
embodiment, shortened TTIs are applied, and communication is
controlled along normal TTIs. To be more specific, the first
embodiment relates to communication control when FDD is used, and
this control is executed as follows.
[0068] (1-1) HARQ-ACK in response to DL data is controlled to be
transmitted four TTIs later.
[0069] (1-2) UL data in response to UL grant is controlled to be
transmitted four TTIs later.
[0070] (1-3) HARQ-ACK in response to UL data is controlled to be
received four TTIs later.
[0071] Also, when TDD is used, the following communication control
is executed.
[0072] (2-1) HARQ-ACK in response to DL data is controlled to be
transmitted (4+k) TTIs later.
[0073] (2-2) UL data in response to UL grant is controlled to be
transmitted (4+1) TTIs later.
[0074] (2-3) HARQ-ACK in response to UL data is controlled to be
received (4+m) TTIs later.
[0075] Note that "k," "l" and "m" are determined by the UL-DL
configuration and the subframe index.
[0076] FIG. 4A illustrates an example of communication control
where normal TTIs are applied when FDD is used. When DL data and UL
grant are transmitted in TTI #0 (subframe #0), the user terminal is
controlled so that HARQ-ACK in response to the DL data or UL data
in response to the UL grant is transmitted in TTI #4 (subframe #4)
four TTIs later. Further, the radio base station (network side) is
controlled so that HARQ-ACK in response to the UL data transmitted
in TTI #4 is transmitted in TTI #8 four TTIs later.
[0077] On the other hand, when shortened TTIs are applied, as
illustrated in FIG. 4B, when DL data and UL grant are transmitted
in TTI #0, the user terminal is controlled so that HARQ-ACK in
response to the DL data or UL data in response to the UL grant is
transmitted in TTI #4 four TTIs later. Further, the radio base
station (network side) is controlled so that HARQ-ACK in response
to the UL data transmitted in TTI #4 is transmitted in TTI #8 four
TTIs later.
[0078] According to the first embodiment described above, the
processing latency can be reduced in proportion to the amount by
which the shortened TTI duration is reduced with respect to the
normal TTI duration. As an example, in FIGS. 4, since the shortened
TTI duration is half of the normal TTI duration, the HARQ RTT
becomes half. In addition, in the first embodiment, existing LTE
FDD/TDD mechanism can be used, so that the circuit implementation
in the user terminal can be simplified.
Second Embodiment
[0079] Next, a second embodiment will be described. In the second
embodiment, communication is controlled under a condition different
from that in the first embodiment, and there are roughly two
controls as explained below.
Embodiment 2.1
[0080] Embodiment 2.1 relates to communication control executed
when FDD is used, and this control is executed as follows.
[0081] (3-1) HARQ-ACK in response to DL data is transmitted x ms
later (where x<4) (or in the first UL-TTI after x ms).
[0082] (3-2) UL data in response to UL grant is transmitted x ms
later (where x<4) (or in the first UL-TTI after x ms).
[0083] (3-3) HARQ-ACK in response to UL data is received x ms later
(where x<4) (or in the first DL-TTI after x ms).
Embodiment 2.2
[0084] When FDD is used in embodiment 2.2, the following
communication control is executed.
[0085] (4-1) HARQ-ACK for DL data is transmitted a x TTIs
later.
[0086] (4-2) UL data in response to UL grant is transmitted a x
TTIs later.
[0087] (4-3) HARQ-ACK in response to UL data is received a x TTIs
later.
[0088] In the above (4-1)-(4-3), the value of "x" or "a" may be
configured by way of higher layer signaling or the like. Also, the
configurable value of "x" or "a" supported by the user terminal may
be reported to the network (for example, radio base station) as UE
capability information in advance.
[0089] According to the second embodiment, the processing latency
can be reduced. Furthermore, it is possible to allow implementation
of multiple user terminals capable of different processing latency
reductions in the network (system)). That is, even if the
processing latency to be reduced differs among a plurality of user
terminals due to differences in manufacturing cost or the like,
communication with these user terminals can be realized. A highly
scalable network (system) can be realized.
[0090] In the user terminal, the time required for each processing
step (or processing) differs depending on the contents of the
transmission/receiving process. Here, the time taken for the
transmission/receiving process in the user terminal will be
described.
[0091] FIG. 5A is a diagram to explain the processing procedure
when HARQ-ACK feedback in response to DL data is transmitted via
the PUCCH. As illustrated in the figure, when DL data is received,
downlink control information (DL assignment) is decoded, and DL
data is demodulated and decoded based on the decoded downlink
control information. After this, HARQ-ACK is generated based on
whether or not the DL data has been successfully decoded. The
generated HARQ-ACK is mapped to an uplink control channel and
transmitted to the network.
[0092] FIG. 5B is a diagram to explain the processing procedure
from the scheduling of UL data to the transmission of the UL data.
However, in this processing procedure, transmission of UL data is
not accompanied by transmission of uplink control information
(UCI). A UL grant transmitted from the network is decoded, and UL
data is encoded and modulated based on the UL grant. Thereafter,
the UL data is mapped to an uplink data channel and transmitted to
the network.
[0093] FIG. 6 is a diagram to explain the processing procedure from
the scheduling of UL data to the transmission of the UL data. In
this processing procedure, at least one of HARQ-ACK and channel
state information (CSI) accompanies transmission of UL data.
[0094] Similar to the processing procedure of FIG. 5A, downlink
control information (DL assignment) is decoded and DL data is
demodulated and decoded based on the decoded downlink control
information. After this, HARQ-ACK is generated based on whether or
not the DL data has been successfully decoded.
[0095] On the other hand, as in FIG. 5B, the UL grant is decoded
and the UL data is coded and modulated based on this UL grant.
Also, channel state information is measured (CSI measurement) based
on the UL grant, and CSI is generated based on the measurement
result. The generated CSI is multiplexed in the encoded and
modulated UL data. UL data and HARQ-ACK are mapped to an uplink
data channel and transmitted to the network.
[0096] Noe that the processes from UL data transmission to HARQ-ACK
feedback (above (3)), which is noted processing latency reduction,
includes demodulation and decoding of UL data, generation of
HARQ-ACK in response to UL data, generation of HARQ-ACK in response
to UL data, mapping of HARQ-ACK, and the like. However, these
processes are performed on the network side (for example, radio
base station), and are not directly related to the process in the
user terminal.
[0097] The inventors of the present invention have focused on the
fact that the processes from the transmission of UL data to
HARQ-ACK feedback (above (3)) depends on the processing capability
of the radio base station and does not depend on the processing
capability of the user terminal, and have come up with the idea of
configuring the timing to transmit HARQ-ACK feedback in response to
UL data by higher layer signaling and applying asynchronous HARQ
without using the PHICH.
Third Embodiment
Embodiment 3.1
[0098] First, embodiment 3.1 will be explained. In embodiment 3.1,
the timing at which HARQ-ACK feedback in response to UL data is
sent is configured by higher layer signaling (see FIG. 7A)).
Examples of timing to be configured are one TTI later, two TTIs
later, four TTIs later and eight TTIs later.
[0099] The user terminal attempts to receive the PHICH at the
configured timing. Then, if a NACK is received in the PHICH, the
user terminal performs non-adaptive retransmission according to the
PHICH. Also, if a UL grant is detected at the configured timing,
the user terminal may perform adaptive retransmission according to
the UL grant. In this case, different resources and different
modulation can be specified in the UL grant. Making the HARQ-ACK
feedback timing in response to UL data configurable as above is
equivalent to making the number of HARQ processes to be executed in
parallel configurable. However, since synchronous HARQ is used as
in existing LTE, the indices of HARQ processes (HARQ process
numbers) to be executed in parallel are uniquely determined by the
UL data transmission/receiving timing and the HARQ-ACK feedback
timing. Note that, if a NACK is returned simply, the user terminal
may perform adaptive retransmission or non-adaptive
retransmission.
[0100] As described above, according to embodiment 3.1, since it is
possible to designate multiple transmission timings, communication
control can be performed according to the capability of the radio
base station. That is, radio base stations with different
processing capabilities can be accommodated in the network. For
example, a radio base station with a low processing capability can
suppress an increase in processing load by configuring relatively
large values (for example, values corresponding to three to four
ms) in the user terminal. On the other hand, a radio base station
with high processing capability can provide low-delay services by
configuring relatively small values (for example, values
corresponding to 0.5 to 1 ms) in the user terminal.
[0101] Note that, although the HARQ-ACK feedback timing in response
to UL data in the above description is configured by higher layer
signaling, the user terminal may employ HARQ-ACK feedback timing
(for example, 4 ms later in the case of FDD) based on existing LTE,
especially when there is no configuration by this signaling. By
doing this, overhead can be reduced because signaling does not need
to be sent to user terminals that do not require particularly low
delay. Even when there is configuration by this signaling, HARQ-ACK
feedback timing based on existing LTE (for example, four ms later
in the case of FDD) can be applied under predetermined conditions
(for example, UL data is scheduled by a UL grant transmitted and
received in the common search space of the PDCCH). By doing this,
even during the process of changing the configuration of the
HARQ-ACK feedback timing, scheduling can be continued by applying
HARQ-ACK feedback timing based on existing LTE (for example, four
ms later in case of FDD). Even if there is configuration by this
signaling, if at least one HARQ process (UL data transmission) to
which the HARQ-ACK feedback timing based on existing LTE (for
example, four ms later in the case of FDD) is applied is included
(the HARQ process is stored in the HARQ buffer and processing is in
progress), the user terminal may apply the HARQ-ACK feedback timing
based on existing LTE (for example, four ms later in the case of
FDD) to all the HARQ processes (UL data transmission). This can
prevent timing mismatch between HARQ processes and the resulting
reduction the efficiency of the use of in radio resources.
Embodiment 3.2
[0102] In embodiment 3.2, the PHICH is not used, and asynchronous
HARQ is used. This eliminates the need to configure the feedback
timing. User terminal does not attempt to receive the PHICH--that
is, the user terminal operates in the same manner as when an ACK is
received in the PHICH. The user terminal performs asynchronous
retransmission based on the HPN indicator included in a UL
grant.
[0103] In addition, when the user terminal performs asynchronous
retransmission based on the HPN indicator included in a UL grant,
an RV indicator to specify the redundancy version (RV) may be
further included in the UL grant. The user terminal selects the
HARQ process to transmit based on the HPN indicator included in the
UL grant, and, furthermore, the user terminal determines which RV
of the HARQ process is transmitted, based on the RV indicator.
[0104] Also, even if asynchronous retransmission is performed based
on the HPN indicator included in a UL grant, the UL grant
transmitted and received in the common search space of the PDCCH
does not need to include control information bits necessary for
applying asynchronous HARQ, such as HPN indicators and RV
indicators. In this case, the user terminal can perform blind
decoding of the UL grants based on the assumption that there are no
HPN indicators or RV indicators in the common search space of the
PDCCH.
[0105] Also, when a UL grant is detected in the common search space
of the PDCCH, the user terminal can transmit new data or
retransmission UL data at the timing based on existing LTE (for
example, four ms later in case of FDD).
[0106] According to the third embodiment described above,
<Embodiment 3.1> is equivalent to performing retransmission
at the timing specified by higher layer, and <Embodiment 3.2>
is equivalent to making retransmission at the timing specified by
the physical layer.
[0107] Here, again, the point that the time required for each
processing step (or processing) differs depending on the contents
of the transmission/receiving process will be described. In various
processes illustrated in FIG. 5A, FIG. 5B and FIG. 6, the
processing time may fluctuate depending on the size of data (TBS:
Transport Block Size) and the amount of frequency resources (the
number of PRBs (Physical Resource Blocks)). For example, the larger
the TBS, the longer it may take for the error correction decoding
process and the CRC check process (for example, the chain-lined
blocks in FIG. 8A, FIG. 8B and FIG. 9). Further, as the number of
PRBs increases, there is a possibility that it may take a longer
time to perform rate matching and resource mapping considering RSs
and so on, and the precoding process according to transmission beam
forming (for example, the chain-lined blocks in FIG. 8A, FIG. 8B
and FIG. 9)). For example, the final step (mapping) in FIG. 8A,
FIG. 8B or FIG. 9 includes the process of performing data mapping,
determining transmission power and making transmission.
[0108] Focusing on the possibility of processing time fluctuation
due to the TBS and the number of PRBs, the present inventors have
come up with the idea of specifying more fragmented UE capability
signaling.
Fourth embodiment
Embodiment 4.1
[0109] In embodiment 4.1, the UE capability signaling reported when
HARQ-ACK feedback in response to DL data is sent in PUCCH
transmission is defined. That is, when HARQ-ACK feedback in
response to DL data is transmitted via PUCCH transmission,
different processing latencies are reported as UE capability
information according to the following conditions:
[0110] (1) TBS of DL data;
[0111] (2) the number of allocation PRBs of DL data;
[0112] (3) m-ary modulation value (level) of DL data;
[0113] (4) the number of MIMO (Multi-Input Multi-Output) layers of
DL data;
[0114] (5) the number of HARQ-ACK bits of the PUCCH; and
[0115] (6) the number of allocation PRBs of the PUCCH.
[0116] In general, the larger the TBS/the number of PRBs of DL
data, the longer it takes for the receiving/decoding process. Also,
the larger the number of HARQ-ACK bits/the number of PRBs of the
PUCCH, the longer it takes for the transmission/encoding process.
Therefore, the user terminal reports the UE capability information
as illustrated in FIG. 10A and FIG. 10B to the network). In FIG.
10A and FIG. 10B (and FIG. 11 and FIGS. 12), successive values are
illustrated in graph representations as UE capabilities, but these
are merely examples, and UE capabilities may be represented in
discrete values as well. In addition, the processing latency may be
specified in relationship to one of the above conditions (1) to
(6), or may be specified (stipulated) for a combination of two or
more conditions.
[0117] UE capability type 1 in FIG. 10A indicates that the TBS or
the number of PRBs of DL data is proportional to the processing
time). UE capability type 2 indicates that the processing time
(long processing time) is constant regardless of the TBS or the
number of PRBs. UE capability type 3 indicates that a certain
processing time (short) can be realized until the TBS or the number
of PRBs reaches a predetermined value, and that, when the TBS or
the number of PRBs exceeds a predetermined value, the TBS or the
number of PRBs is proportional to the processing time. In FIG. 10B,
the TBS or the number of PRBs can be replaced by the number of
HARQ-ACK bits of the PUCCH or the number of allocation PRBs of the
PUCCH, and each type indicates the same characteristics.
[0118] The network configures the timing to send HARQ-ACK feedback
to the user terminal via PUCCH transmission based on the received
UE capability information. At this time, different timing may be
configured according to the capability of the target user terminal
and the conditions (1) to (6)). Also, if there is a combination of
two or more of the conditions (1) to (6), different timing may be
configured.
[0119] In the state where the PUCCH transmission timing of HARQ-ACK
feedback is not configured (state with no configuration) as
described above, HARQ-ACK may be transmitted at the same timing as
in existing LTE (normal TTI). This means, in other words, existing
LTE operation will be performed by default.
[0120] According to embodiment 4.1, the network can know the
processing time for HARQ-ACK feedback in response to DL data in the
user terminal from the TBS and the number of PRBs. Therefore, even
when a user terminal with a relatively low processing capability is
accommodated, the network is still able to configure HARQ-ACK
feedback in a short time. For example, if user terminal A can send
feedback within one ms if the TBS is less than or equal to X and
the number of PRBs is less than or equal to Y, and user terminal B
can send feedback within one ms regardless of the TBS or the number
of PRBs, the network can apply scheduling restrictions to these
user terminals so that feedback within one ms is configured in both
user terminals, and, in user terminal A, the TBS of DL data is X or
less and the number of PRBs is Y or less. In this manner,
throughput reduction due to scheduling restrictions is also allowed
for a user terminal (user terminal A) having relatively low
processing capability, so that it is possible to provide the same
low delay service as by a user terminal (user terminal B) with high
processing capability.
Embodiment 4.2
[0121] In embodiment 4.2, UE capability signaling that is reported
when UL data is transmitted in response to UL grants is defined.
When UL data is sent in response to a UL grant, different
processing latencies are reported as UE capability information
according to the following conditions:
[0122] (7) TBS of UL data;
[0123] (8) the number of allocation PRBs of the PUSCH;
[0124] (9) m-ary modulation value of the PUSCH;
[0125] (10) the number of MIMO layers of the PUSCH; and
[0126] (11) whether or not UCI is multiplexed on the PUSCH or its
payload.
[0127] In general, the larger the TBS/the number of PRBs of the UL
data, the longer it takes for the transmission/encoding process.
Also, the larger the number of HARQ-ACK bits/the number of PRBs of
the PUCCH, the longer it takes for the transmission/encoding
process. For this reason, the UE capability information as
illustrated in FIG. 11A and FIG. 11B is reported to the
network.
[0128] Note that in each type in FIG. 11A, DL data in FIG. 10A is
replaced by UL data, and, in each type in FIG. 11B, the number of
HARQ-ACK bits of the PUCCH or the number of allocation PRBs of the
PUCCH in FIG. 10B is replaced by the above conditions (7) to (11),
and therefore their detailed explanation will be omitted. In FIG.
11A and FIG. 11B, successive values are illustrated in graph
representations as UE capabilities, but these are merely examples,
and UE capabilities may be represented in discrete values as well.
In addition, the processing latency may be specified in
relationship to one of the above conditions (7) to (11), or may be
specified (stipulated) for a combination of two or more
conditions.
[0129] The network configures the uplink data transmission timing
for a user terminal based on the received UE capability
information. At this time, different timings may be configured
according to the capability of the target user terminal and the
conditions (7) to (11). Also, different timing may be configured
for a combination of two or more of the conditions (7) to (11).
[0130] In addition, UL data may be transmitted at the same timing
as in existing LTE in the state where no configuration is provided.
In other words, default means performing existing LTE (normal TTI)
operation.
[0131] In embodiment 4.2, for example, communication control can be
performed so that the processing time is one mm or less only when
the TBS of uplink data is not less than a first specific value and
not more than a second specific value. In addition to this,
communication control can be performed to reduce the processing
time to one mm or less only when UCI is not multiplexed on the
PUSCH, or it is possible to perform communication control to
specify the uplink data TBS and the number of PRBs.
[0132] According to embodiment 4.2, the network can know the
processing time of UL data in the user terminal from the TBS and
the number of PRBs. Therefore, even when a user terminal with a
relatively low processing capability is accommodated, the network
is still able to configure UL data transmission in a short time.
For example, if user terminal A can send UL data within one ms if
the TBS is less than or equal to X and the number of PRBs is less
than or equal to Y, and user terminal B can send UL data within one
ms regardless of the TBS or the number of PRBs, the network can
apply scheduling restrictions to these user terminals so that UL
data within one ms is configured in both user terminals, and, in
user terminal A, the TBS of UL data is X or less and the number of
PRBs is Y or less. In this manner, throughput reduction due to
scheduling restrictions is also allowed for a user terminal (user
terminal A) having relatively low processing capability, so that it
is possible to provide the same low delay service as by a user
terminal (user terminal B) with high processing capability.
[0133] Next, a specific example of communication control will be
described with reference to FIG. 12. When the user terminal reports
UE capability as illustrated in FIGS. 12 (FIG. 12A and FIG. 12B),
the network can configure the UE so that the DL HARQ timing and the
UL scheduling timing are reduced to 50%. In this case, the network
schedules DL/UL data so that the TBS/PRB of DL/UL do not exceed a
predetermined value (50% in FIGS. 12). Also, the user terminal
applies the configured HARQ/scheduling timing (50% in FIGS. 12)
unless the TBS/PRB of the DL/UL exceed a predetermined value (50%
in FIGS. 12)). If TBS/PRB of DL/UL exceeds the predetermined value
(50%), control at a later timing may be allowed, instead of the
configured HARQ/scheduling timings.
[0134] As described above, according to the fourth embodiment,
shortened TTIs can be appropriately used according to the
processing capability of the user terminal, so that it is possible
to achieve reduction of processing latency.
[0135] It is also possible to combine above embodiments 4.1 and
4.2. For example, the UE capability information may be a
combination of the UE capability information of the embodiment 4.1
(which specifies (stipulates) the processing time corresponding to
at least one of the conditions (1) to (6)) and the UE capability
information of embodiment 4.2 (which specifies (stipulates) the
processing time corresponding to at least one of the conditions (7)
to (11)). In this case, the timing of HARQ-ACK feedback in response
to DL data is appropriately controlled, and the timing of transmit
UL data is appropriately controlled.
[0136] According to the first to fourth embodiments described
above, communication can be appropriately performed even when
shortened TTIs are applied.
[0137] (Radio Communication System)
[0138] Now, the structure of the radio communication system
according to an embodiment of the present invention will be
described below. In this radio communication system, the radio
communication methods of the above-described embodiment are
employed. Note that the radio communication methods of the
above-described embodiments may be applied individually or may be
applied in combination.
[0139] FIG. 13 is a diagram to illustrate an example of a schematic
structure of a radio communication system according to an
embodiment of the present invention. The radio communication system
1 can adopt carrier aggregation (CA) and/or dual connectivity (DC)
to group a plurality of fundamental frequency blocks (component
carriers) into one, where the LTE system bandwidth (for example, 20
MHz) constitutes one unit. Note that the radio communication system
1 may be referred to as "SUPER 3G," "LTE-A" (LTE-Advanced),
"IMT-Advanced," "4G," "5G," "FRA" (Future Radio Access) and so
on.
[0140] The radio communication system 1 illustrated in FIG. 13
includes a radio base station 11 that forms a macro cell Cl, and
radio base stations 12a to 12c that form small cells C2, which are
placed within the macro cell C1 and which are narrower than the
macro cell C1. Also, user terminals 20 are placed in the macro cell
C1 and in each small cell C2.
[0141] The user terminals 20 can connect with both the radio base
station 11 and the radio base stations 12. The user terminals 20
may use the macro cell C1 and the small cells C2, which use
different frequencies, at the same time, by means of CA or DC.
Also, the user terminals 20 can execute CA or DC by using a
plurality of cells (CCs) (for example, six or more CCs).
[0142] Between the user terminals 20 and the radio base station 11,
communication can be carried out using a carrier of a relatively
low frequency band (for example, 2 GHz) and a narrow bandwidth
(referred to as, for example, an "existing carrier," a "legacy
carrier" and so on). Meanwhile, between the user terminals 20 and
the radio base stations 12, a carrier of a relatively high
frequency band (for example, 3.5 GHz, 5 GHz and so on) and a wide
bandwidth may be used, or the same carrier as that used in the
radio base station 11 may be used. Note that the configuration of
the frequency band for use in each radio base station is by no
means limited to these.
[0143] A structure may be employed here in which wire connection
(for example, means in compliance with the CPRI (Common Public
Radio Interface) such as optical fiber, the X2 interface and so on)
or wireless connection is established between the radio base
station 11 and the radio base station 12 (or between two radio base
stations 12).
[0144] The radio base station 11 and the radio base stations 12 are
each connected with a higher station apparatus 30, and are
connected with a core network 40 via the higher station apparatus
30. Note that the higher station apparatus 30 may be, for example,
an access gateway apparatus, a radio network controller (RNC), a
mobility management entity (MME) and so on, but is by no means
limited to these. Also, each radio base station 12 may be connected
with higher station apparatus 30 via the radio base station 11.
[0145] Note that the radio base station 11 is a radio base station
having a relatively wide coverage, and may be referred to as a
"macro base station," a "central node," an "eNB" (eNodeB), a
"transmitting/receiving point" and so on. Also, the radio base
stations 12 are radio base stations having local coverages, and may
be referred to as "small base stations," "micro base stations,"
"pico base stations," "femto base stations," "HeNBs" (Home
eNodeBs), "RRHs" (Remote Radio Heads), "transmitting/receiving
points" and so on. Hereinafter the radio base stations 11 and 12
will be collectively referred to as "radio base stations 10,"
unless specified otherwise.
[0146] The user terminals 20 are terminals to support various
communication schemes such as LTE, LTE-A and so on, and may be
either mobile communication terminals or stationary communication
terminals.
[0147] In the radio communication system 1, as radio access
schemes, OFDMA (Orthogonal Frequency Division Multiple Access) is
applied to the downlink, and SC-FDMA (Single-Carrier Frequency
Division Multiple Access) is applied to the uplink. OFDMA is a
multi-carrier communication scheme to make communication by
dividing a frequency bandwidth into a plurality of narrow frequency
bandwidths (subcarriers) and mapping data to each subcarrier.
SC-FDMA is a single-carrier communication scheme to mitigate
interference between terminals by dividing the system bandwidth
into bands formed with one or continuous resource blocks per
terminal, and allowing a plurality of terminals to use mutually
different bands. Note that the uplink and downlink radio access
schemes are not limited to these combinations, and OFDMA may be
used in the uplink.
[0148] In the radio communication system 1, a downlink shared
channel (PDSCH: Physical Downlink Shared CHannel), which is used by
each user terminal 20 on a shared basis, a broadcast channel (PBCH:
Physical Broadcast CHannel), downlink L1/L2 control channels and so
on are used as downlink channels. User data, higher layer control
information and predetermined SIBs (System Information Blocks) are
communicated in the PDSCH. Also, the MIB (Master Information Block)
is communicated in the PBCH.
[0149] The downlink L1/L2 control channels include a PDCCH
(Physical Downlink Control CHannel), an EPDCCH (Enhanced Physical
Downlink Control CHannel), a PCFICH (Physical Control Format
Indicator CHannel), a PHICH (Physical Hybrid-ARQ Indicator CHannel)
and so on. Downlink control information (DCI) including PDSCH and
PUSCH scheduling information is communicated by the PDCCH. The
number of OFDM symbols to use for the PDCCH is communicated by the
PCFICH. HARQ delivery acknowledgement signals (ACKs/NACKs) in
response to the PUSCH are communicated by the PHICH. The EPDCCH is
frequency-division-multiplexed with the PDSCH (downlink shared data
channel) and used to communicate DCI and so on, like the PDCCH.
[0150] In the radio communication system 1, an uplink shared
channel (PUSCH: Physical Uplink Shared CHannel), which is used by
each user terminal 20 on a shared basis, an uplink control channel
(PUCCH: Physical Uplink Control CHannel), a random access channel
(PRACH: Physical Random Access CHannel) and so on are used as
uplink channels. User data and higher layer control information are
communicated by the PUSCH. Uplink control information (UCI: Uplink
Control Information), including at least one of delivery
acknowledgment information (ACK/NACK) and radio quality information
(CQI), is transmitted by the PUSCH or the PUCCH. By means of the
PRACH, random access preambles for establishing connections with
cells are communicated.
[0151] <Radio Base Station>
[0152] FIG. 14 is a diagram to illustrate an example of an overall
structure of a radio base station according to an embodiment of the
present invention. A radio base station 10 has a plurality of
transmitting/receiving antennas 101, amplifying sections 102,
transmitting/receiving sections 103, a baseband signal processing
section 104, a call processing section 105 and a communication path
interface 106. Note that one or more transmitting/receiving
antennas 101, amplifying sections 102 and transmitting/receiving
sections 103 may be provided.
[0153] User data to be transmitted from the radio base station 10
to a user terminal 20 on the downlink is input from the higher
station apparatus 30 to the baseband signal processing section 104,
via the communication path interface 106.
[0154] In the baseband signal processing section 104, the user data
is subjected to a PDCP (Packet Data Convergence Protocol) layer
process, user data division and coupling, RLC (Radio Link Control)
layer transmission processes such as RLC retransmission control,
MAC (Medium Access Control) retransmission control (for example, an
HARQ (Hybrid Automatic Repeat reQuest) transmission process),
scheduling, transport format selection, channel coding, an inverse
fast Fourier transform (IFFT) process and a precoding process, and
the result is forwarded to each transmitting/receiving section 103.
Furthermore, downlink control signals are also subjected to
transmission processes such as channel coding and an inverse fast
Fourier transform, and forwarded to each transmitting/receiving
section 103.
[0155] Baseband signals that are pre-coded and output from the
baseband signal processing section 104 on a per antenna basis are
converted into a radio frequency band in the transmitting/receiving
sections 103, and then transmitted. The radio frequency signals
having been subjected to frequency conversion in the
transmitting/receiving sections 103 are amplified in the amplifying
sections 102, and transmitted from the transmitting/receiving
antennas 101.
[0156] The transmitting/receiving sections 103 can be constituted
by transmitters/receivers, transmitting/receiving circuits or
transmitting/receiving devices that can be described based on
common understanding of the technical field to which the present
invention pertains. Note that a transmitting/receiving section 103
may be structured as a transmitting/receiving section in one
entity, or may be constituted by a transmitting section and a
receiving section.
[0157] Meanwhile, as for uplink signals, radio frequency signals
that are received in the transmitting/receiving antennas 101 are
each amplified in the amplifying sections 102. The
transmitting/receiving sections 103 receive the uplink signals
amplified in the amplifying sections 102. The received signals are
converted into the baseband signal through frequency conversion in
the transmitting/receiving sections 103 and output to the baseband
signal processing section 104.
[0158] In the baseband signal processing section 104, user data
that is included in the uplink signals that are input is subjected
to a fast Fourier transform (FFT) process, an inverse discrete
Fourier transform (IDFT) process, error correction decoding, a MAC
retransmission control receiving process, and RLC layer and PDCP
layer receiving processes, and forwarded to the higher station
apparatus 30 via the communication path interface 106. The call
processing section 105 performs call processing such as setting up
and releasing communication channels, manages the state of the
radio base station 10 and manages the radio resources.
[0159] The communication path interface section 106 transmits and
receives signals to and from the higher station apparatus 30 via a
predetermined interface. Also, the communication path interface 106
may transmit and/or receive signals (backhaul signaling) with other
radio base stations 10 via an inter-base station interface (for
example, an interface in compliance with the CPRI (Common Public
Radio Interface), such as optical fiber, the X2 interface,
etc.).
[0160] FIG. 15 is a diagram to illustrate an example of a
functional structure of a radio base station according to the
present embodiment. Note that, although FIG. 15 primarily
illustrates functional blocks that pertain to characteristic parts
of the present embodiment, the radio base station 10 has other
functional blocks that are necessary for radio communication as
well. As illustrated in FIG. 15, the baseband signal processing
section 104 has a control section 301, a transmission signal
generation section 302, a mapping section 303 and a received signal
processing section 304.
[0161] The control section 301 controls the entire radio base
station 10. The control section 301 controls, for example, the
generation of downlink signals by the transmission signal
generation section 302, the mapping of signals by the mapping
section 303, the signal receiving process by the received signal
processing section 304, and the like.
[0162] To be more specific, the control section 301 controls the
transmission of downlink (DL) signals (including, for example,
controlling the modulation scheme, the coding rate, the allocation
of resources (scheduling), etc.) based on channel state information
(CSI) that is reported from the user terminals 20.
[0163] Furthermore, the control section 301 controls the carrier
aggregation (CA) of the user terminal 20. To be more specific, the
control section 301 may control the transmission signal generation
section 302 to determine application of CA/changes in the number of
CCs and so on, based on CSI or the like reported from the user
terminals 20, and generate information to indicate such
application/changes. Note that the information to indicate the
application/changes may be included in control information sent by
higher layer signaling.
[0164] Further, the control section 301 controls the transmission
time intervals (TTIs) used for receiving downlink signals and/or
transmitting uplink signals. The control section 301 configures
one-ms normal TTIs and/or shortened TTIs that are shorter than
normal TTIs. Example structures and configurations of shortened
TTIs have been explained with reference to FIGS. 2 and 3. The
control section 301 may command configuration of shortened TTIs to
the user terminal 20 by way of (1) implicit reporting, or by way of
explicit reporting using at least one of (2) RRC signaling, (3) MAC
signaling and (4) PHY signaling.
[0165] In the first embodiment, the control section 301 performs
control so that HARQ-ACK in response to UL data is transmitted four
TTIs later. The control section 301 may perform control so that
HARQ-ACK in response to UL data is transmitted (4+m) TTIs
later.
[0166] In the second embodiment, the control section 301 performs
control so that HARQ-ACK in response to UL data is transmitted x ms
later (where x<4) (or in the first DL-TTI after x ms)).
Alternatively, the control section 301 may perform control so that
HARQ-ACK in response to UL data is received a x TTIs later.
[0167] In the third embodiment, the control section 301 configures
the HARQ-ACK feedback transmission timing in response to UL data by
higher layer signaling (see FIG. 7A). Examples of timing to be
configured are one
[0168] TTI later, two TTIs later, four TTIs later or eight TTIs
later. When asynchronous HARQ is used, feedback timing is not
configured.
[0169] In the fourth embodiment, the control section 301 configures
the transmission timing according to the capability information of
the user terminal reported by UE capability signaling.
[0170] The control section 301 can be constituted by a controller,
a control circuit or a control device that can be described based
on common understanding of the technical field to which the present
invention pertains.
[0171] The transmission signal generation section 302 generates DL
signals (downlink control signals, downlink data signals, downlink
reference signals and so on) based on commands from the control
section 301, and outputs these signals to the mapping section 303.
To be more specific, the transmission signal generation section 302
generates downlink data signals (PDSCH) including the
above-mentioned reporting information (control information) to be
sent in higher layer signaling, user data and so on, and outputs
the generated downlink data signals (PDSCH) to the mapping section
303. Further, the transmission signal generation section 302
generates a downlink control signal (PDCCH/EPDCCH), including
above-mentioned DCI, and outputs this to the mapping section 303.
Further, the transmission signal generation section 302 generates
downlink reference signals such as CRS and CSI-RS, and outputs them
to the mapping section 303.
[0172] For the transmission signal generation section 302, a signal
generator, a signal generating circuit or a signal generating
device that can be described based on common understanding of the
technical field to which the present invention pertains can be
used.
[0173] The mapping section 303 maps the downlink signals generated
in the transmission signal generation section 302 to predetermined
radio resources based on commands from the control section 301, and
outputs these to the transmitting/receiving sections 103. For the
mapping section 303, mapper, a mapping circuit or a mapping device
that can be described based on common understanding of the
technical field to which the present invention pertains can be
used.
[0174] The received signal processing section 304 performs the
receiving process (for example, demapping, demodulation, decoding
and so on) of uplink signals that are transmitted from the user
terminals 20. The processing results are output to the control
section 301.
[0175] The receiving process section 304 can be constituted by a
signal processor, a signal processing circuit or a signal
processing device, and a measurer, a measurement circuit or a
measurement device that can be described based on common
understanding of the technical field to which the present invention
pertains.
[0176] <User Terminal>
[0177] FIG. 16 is a diagram to illustrate an example of an overall
structure of a user terminal according to one embodiment of the
present invention. The user terminal 20 includes a plurality of
transmitting/receiving antennas 201 for MIMO (Multi-Input
Multi-Output) transmission, amplifying sections 202,
transmitting/receiving sections 203, a baseband signal processing
section 204 and an application section 205.
[0178] Radio frequency signals that are received in a plurality of
transmitting/receiving antennas 201 are each amplified in the
amplifying sections 202. Each transmitting/receiving section 203
receives the downlink signals amplified in the amplifying sections
202. The received signal is subjected to frequency conversion and
converted into the baseband signal in the transmitting/receiving
sections 203, and output to the baseband signal processing section
204.
[0179] In the baseband signal processing section 204, the baseband
signal that is input is subjected to an FFT process, error
correction decoding, a retransmission control receiving process,
and so on. Downlink user data is forwarded to the application
section 205. The application section 205 performs processes related
to higher layers above the physical layer and the MAC layer, and so
on. Furthermore, in the downlink data, broadcast information is
also forwarded to the application section 205.
[0180] Meanwhile, uplink user data is input from the application
section 205 to the baseband signal processing section 204. The
baseband signal processing section 204 performs a retransmission
control transmission process (for example, an HARQ transmission
process), channel coding, pre-coding, a discrete Fourier transform
(DFT) process, an IFFT process and so on, and the result is
forwarded to each transmitting/receiving section 203. The baseband
signal that is output from the baseband signal processing section
204 is converted into a radio frequency bandwidth in the
transmitting/receiving sections 203 and transmitted. The radio
frequency signals that are subjected to frequency conversion in the
transmitting/receiving sections 203 are amplified in the amplifying
sections 202, and transmitted from the transmitting/receiving
antennas 201.
[0181] For the transmitting/receiving sections 203,
transmitters/receivers, transmitting/receiving circuits or
transmitting/receiving devices that can be described based on
common understanding of the technical field to which the present
invention pertains can be used. Furthermore, transmitting/receiving
sections 203 may be structured as one transmitting/receiving
section, or may be formed with a transmitting section and a
receiving section.
[0182] FIG. 17 is a diagram to illustrate an example of a
functional structure of a user terminal according to the present
embodiment. Note that, although FIG. 17 primarily illustrates
functional blocks that pertain to characteristic parts of the
present embodiment, the user terminal 20 has other functional
blocks that are necessary for radio communication as well. As
illustrated in FIG. 17, the baseband signal processing section 204
provided in the user terminal 20 has a control section 401, a
transmission signal generation section 402, a mapping section 403,
a received signal processing section 404 and a measurement section
405.
[0183] The control section 401 controls the whole of the user
terminal 20. The control section 401 controls, for example, the
generation of signals in the transmission signal generation section
402, the mapping of signals in the mapping section 403, the signal
receiving process in the received signal processing section 404,
and so on.
[0184] Further, the control section 401 controls the transmission
time intervals (TTI) used to receive downlink (DL) signals and/or
to transmit of uplink (UL) signals. The control section 301
configures one-ms normal TTIs and/or shortened TTIs that are
shorter than normal TTIs. Example structures and configurations of
shortened TTIs have been explained with reference to FIGS. 2 and 3.
The control section 401 may configure (detect) shortened TTIs based
on (1) implicit reporting, or based on explicit reporting using at
least one of (2) RRC signaling, (3) MAC signaling and (4) PHY
signaling, from the radio base station 10.
[0185] In the first embodiment, the control section 401 performs
control so that HARQ-ACK in response to DL data is transmitted four
TTIs later, and UL data in response to UL grant is transmitted four
TTIs later. Alternatively, control may be performed so that
HARQ-ACK in response to DL data is transmitted (4+k) TTIs later,
and UL data in response to UL grant is transmitted (4+1) TTIs
later.
[0186] In the second embodiment, the control section 401 performs
control so that HARQ-ACK in response to DL data is transmitted x ms
later (where x<4) (or in the first UL-TTI after x ms), and UL
data in response to UL grant is transmitted x ms later (where
x<4) (or in the first UL-TTI after x ms). Alternatively, control
may be performed so that HARQ-ACK in response to DL data is
transmitted a x TTIs later, and UL data in response to UL grant is
transmitted a x TTIs later.
[0187] In the third embodiment, when the PHICH is received at a
configured timing, the control section 401 performs control so that
non-adaptive retransmission is performed according to the PHICH.
Also, if a UL grant is detected at a configured timing, adaptive
retransmission may be performed according to the UL grant. Also, if
a NACK is returned simply, adaptive retransmission or non-adaptive
retransmission may be performed.
[0188] Also, when asynchronous HARQ is applied without using the
PHICH, it is not necessary to try receiving the PHICH--that is, the
same operation as when an ACK is received in the PHICH may be
performed. The control section 401 performs asynchronous
retransmission based on the HPN indicator included in a UL
grant.
[0189] In accordance with embodiment 4.1, if HARQ-ACK feedback in
response to DL data is sent via PUCCH transmission, the control
section 401 performs control so that different processing latencies
are reported as UE capability information according to specific
condition. In addition, in embodiment 4.2, when UL data is
transmitted in response to UL grant, control is performed so that
different processing latencies are reported as UE capability
information according to specific conditions.
[0190] For the control section 401, a controller, a control circuit
or a control device that can be described based on common
understanding of the technical field to which the present invention
pertains can be used.
[0191] The transmission signal generation section 302 generates DL
signals (downlink control signals, downlink data signals, downlink
reference signals and so on) based on commands from the control
section 301, and outputs these signals to the mapping section 303.
For example, the transmission signal generation section 402
generates uplink control signals (PUCCH) including UCI (at least
one of HARQ-ACK, CQI, and SR).
[0192] For the transmission signal generation section 402, a signal
generator, a signal generating circuit or a signal generating
device that can be described based on common understanding of the
technical field to which the present invention pertains can be
used.
[0193] The mapping section 403 maps the UL signals (uplink control
signals and/or uplink data signals) generated in the transmission
signal generation section 402 to radio resources based on commands
from the control section 401, and output the result to the
transmitting/receiving sections 203. For the mapping section 403,
mapper, a mapping circuit or a mapping device that can be described
based on common understanding of the technical field to which the
present invention pertains can be used.
[0194] The received signal processing section 404 performs the
receiving process (for example, demapping, demodulation, decoding,
etc.) of downlink signals (including downlink control signals and
downlink data signals). The received signal processing section 404
outputs the information received from the radio base station 10, to
the control section 401. The received signal processing section 404
outputs, for example, broadcast information, system information,
control information by higher layer signaling such as RRC
signaling, DCI, and the like, to the control section 401.
[0195] The received signal processing section 404 can be
constituted by a signal processor, a signal processing circuit or a
signal processing device that can be described based on common
understanding of the technical field to which the present invention
pertains. Also, the received signal processing section 404 can
constitute the receiving section according to the present
invention.
[0196] The measurement section 405 measures channel states based on
reference signals (for example, CSI-RS) from the radio base station
10, and outputs the measurement results to the control section 401.
Measurement of the channel state may be performed for each CC.
[0197] The measurement section 405 can be constituted by a signal
processor, a signal processing circuit or a signal processing
device, and a measurer, a measurement circuit or a measurement
device that can be described based on common understanding of the
technical field to which the present invention pertains.
[0198] (Hardware structure)
[0199] Note that the block diagrams that have been used to describe
the above embodiments illustrate blocks in functional units. These
functional blocks (components) may be implemented in arbitrary
combinations of hardware and/or software. Also, the means for
implementing each functional block is not particularly limited.
That is, each functional block may be implemented with one
physically-integrated device, or may be implemented by connecting
two physically-separate devices via radio or wire and by using
these multiple devices.
[0200] That is, the radio base stations, user terminals and so
according to embodiments of the present invention may function as a
computer that executes the processes of the radio communication
method of the present invention. FIG. 18 is a diagram to illustrate
an example hardware structure of a radio base station and a user
terminal according to an embodiment of the present invention.
Physically, a radio base station 10 and a user terminal 20, which
have been described above, may be formed as a computer apparatus
that includes a processor 1001, a memory 1002, a storage 1003, a
communication apparatus 1004, an input apparatus 1005, an output
apparatus 1006 and a bus 1007.
[0201] Note that, in the following description, the word
"apparatus" may be replaced by "circuit," "device," "unit" and so
on. Note that the hardware structure of the radio base station 10
and the user terminal 20 may be designed to include one or more of
each apparatus illustrated in the drawings, or may be designed not
to include part of the apparatuses.
[0202] Each function of the radio base station 10 and the user
terminal 20 is implemented by reading predetermined software
(programs) on hardware such as the processor 1001 and the memory
1002, and by controlling the calculations in the processor 1001,
the communication in the communication apparatus 1004, and the
reading and/or writing of data in the memory 1002 and the storage
1003.
[0203] The processor 1001 may control the whole computer by, for
example, running an operating system. The processor 1001 may be
configured with a central processing unit (CPU) including an
interface with a peripheral device, a control device, a computing
device, a register, and the like. For example, the above-described
baseband signal process section 104 (204), call processing section
105 and so on may be implemented by the central processing
apparatus 1001.
[0204] Further, the processor 1001 reads a program (program code),
a software module or data from the storage 1003 and/or the
communication device 1004 to the memory 1002, and executes various
processes according to these. As for the programs, programs to
allow the computer to execute at least part of the operations of
the above-described embodiments may be used. For example, the
control section 401 of the user terminals 20 may be stored in the
memory 1002 and implemented by a control program that operates on
the processor 1001, and other functional blocks may be implemented
likewise.
[0205] The memory 1002 is a computer-readable recording medium, and
may be constituted by, for example, at least one of a ROM (Read
Only Memory), an EPROM (Erasable Programmable ROM), a RAM (Random
Access Memory) and so on. The memory 1002 may be referred to as a
"register," a "cache," a "main memory" (primary storage apparatus)
or the like. The memory 1002 can store executable programs (program
codes), software modules, and the like for implementing the radio
communication methods according to embodiments of the present
invention.
[0206] The storage 1003 is a computer readable recording medium,
and is configured with at least one of an optical disk such as a
CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a
magneto-optical disk, a flash memory and so on. The storage 1003
may be referred to as a "secondary storage apparatus."
[0207] The communication apparatus 1004 is hardware
(transmitting/receiving device) for allowing inter-computer
communication by using wired and/or wireless networks, and may be
referred to as, for example, a "network device," a "network
controller," a "network card," a "communication module" and so on.
For example, the above-described transmitting/receiving antennas
101 (201), amplifying sections 102 (202), transmitting/receiving
sections 103 (203), communication path interface 106 and so on may
be implemented by the communication apparatus 1004.
[0208] The input apparatus 1005 is an input device for receiving
input from the outside (for example, a keyboard, a mouse, etc.).
The output apparatus 1006 is an output device for allowing sending
output to the outside (for example, a display, a speaker, etc.).
Note that the input apparatus 1005 and the output apparatus 1006
may be provided in an integrated structure (for example, a touch
panel).
[0209] Further, the respective devices such as the processor 1001
and the memory 1002 are connected by a bus 1007 for communicating
information. The bus 1007 may be formed with a single bus, or may
be formed with buses that vary between the apparatuses.
[0210] Also, the radio base station 10 and the user terminal 20 may
be structured to include hardware such as a microprocessor, an ASIC
(Application-Specific Integrated Circuit), a PLD (Programmable
Logic Device), an FPGA (Field Programmable Gate Array) and so on,
and part or all of the functional blocks may be implemented by the
hardware. For example, the processor 1001 may be implemented with
at least one of these hardware.
[0211] Note that the terminology used in this description and the
terminology that is needed to understand this description may be
replaced by other terms that convey the same or similar meanings.
For example, "channels" and/or "symbols" may be replaced by
"signals" (or "signaling"). Also, "signals" may be "messages."
Furthermore, "component carriers" (CCs) may be referred to as
"cells," "frequency carriers," "carrier frequencies" and so on.
[0212] Further, a radio frame may be comprised of one or more
periods (frames) in the time domain. Each of one or more periods
(frames) constituting a radio frame may be referred to as a
"subframe." Further, a subframe may be comprised of one or more
slots in the time domain. Further, a slot may be comprised of one
or more symbols (OFDM symbols, SC-FDMA symbols, etc.) in the time
domain.
[0213] A radio frame, a subframe, a slot and a symbol all represent
the time unit in signal communication. Radio frames, subframes,
slots and symbols may be called by other names. For example, one
subframe may be referred to as a "transmission time interval"
(TTI), or a plurality of consecutive subframes may be referred to
as a "TTI," and one slot may be referred to as a "TTI." That is, a
subframe and a TTI may be a subframe (one ms) in existing LTE, may
be a shorter period than one ms (for example, 1 to 13 symbols), or
may be a longer period of time than one ms.
[0214] Here, a TTI refers to the minimum time unit of scheduling in
wireless communication, for example. For example, in LTE systems,
the radio base station schedules the allocation radio resources
(such as the frequency bandwidth and transmission power that can be
used by each user terminal) to each user terminal in TTI units. The
definition of TTIs is not limited to this.
[0215] A TTI having a time duration of one ms may be referred to as
a "normal TTI" (TTI in LTE Rel. 8 to 12), a "long TTI," a "normal
subframe," a "long subframe," etc. A TTI that is shorter than a
normal TTI may be referred to as a "shortened TTI," a "short TTI,"
a "shortened subframe," a "short subframe," or the like.
[0216] A resource block (RB) is a resource allocation unit in the
time domain and the frequency domain, and may include one or a
plurality of consecutive subcarriers in the frequency domain. Also,
an RB may include one or more symbols in the time domain and may be
one slot, one subframe or one TTI in length. One TTI and one
subframe each may be comprised of one or more resource blocks. Note
that an RB may be referred to as a "physical resource block" (PRB:
Physical RB), a "PRB pair," an "RB pair," or the like.
[0217] Further, a resource block may be comprised of one or more
resource elements (REs). For example, one RE may be a radio
resource field of one subcarrier and one symbol.
[0218] Note that the structures of radio frames, subframes, slots,
symbols and the like described above are merely examples. For
example, configurations such as the number of subframes included in
a radio frame, the number of slots included in a subframe, the
number of symbols and RBs included in a slot, the number of
subcarriers included in an RB, the number of symbols in a TTI, the
symbol duration and the cyclic prefix (CP) length can be variously
changed.
[0219] Also, the information and parameters described in this
description may be represented in absolute values or in relative
values with respect to a predetermined value, or may be represented
in other information formats. For example, radio resources may be
specified by predetermined indices.
[0220] The information, signals and/or others described in this
description may be represented by using a variety of different
technologies. For example, data, instructions, commands,
information, signals, bits, symbols and chips, all of which may be
referenced throughout the description, may be represented by
voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or photons, or any combination of
these.
[0221] Also, software and commands may be transmitted and received
via communication media. For example, when software is transmitted
from a website, a server or other remote sources by using wired
technologies (coaxial cables, optical fiber cables, twisted-pair
cables, digital subscriber lines (DSL) and so on) and/or wireless
technologies (infrared radiation and microwaves), these wired
technologies and/or wireless technologies are also included in the
definition of communication media.
[0222] Further, the radio base station in this specification may be
read by a user terminal. For example, each aspect/embodiment of the
present invention may be applied to a configuration in which
communication between a radio base station and a user terminal is
replaced with communication between a plurality of user terminals
(D2D: Device-to-Device). In this case, the user terminal 20 may
have the functions of the radio base station 10 described above. In
addition, wording such as "uplink" and "downlink" may be
interpreted as "side." For example, an uplink channel may be
interpreted as a side channel.
[0223] Likewise, a user terminal in this specification may be
interpreted as a radio base station. In this case, the radio base
station 10 may have the functions of the user terminal 20 described
above.
[0224] The examples/embodiments illustrated in this description may
be used individually or in combinations, and the mode of may be
switched depending on the implementation. Also, a report of
predetermined information (for example, a report to the effect that
"X holds") does not necessarily have to be sent explicitly, and can
be sent implicitly (by, for example, not reporting this piece of
information).
[0225] Reporting of information is by no means limited to the
example s/embodiments described in this description, and other
methods may be used as well. For example, reporting of information
may be implemented by using physical layer signaling (for example,
DCI (Downlink Control Information) and UCI (Uplink Control
Information)), higher layer signaling (for example, RRC (Radio
Resource Control) signaling, broadcast information (the MIB (Master
Information Blocks) and SIBs (System Information Blocks) and so on)
and MAC (Medium Access Control) signaling, other signals or
combinations of these
[0226] The examples/embodiments illustrated in this description may
be applied to LTE (Long Term Evolution), LTE-A (LTE-Advanced),
LTE-B (LTE-Beyond), SUPER 3G, IMT-Advanced, 4G (4th generation
mobile communication system), 5G (5th generation mobile
communication system), FRA (Future Radio Access), New-RAT (Radio
Access Technology), CDMA 2000, UMB (Ultra Mobile Broadband), IEEE
802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX
(registered trademark)), IEEE 802.20, UWB (Ultra-WideBand),
Bluetooth (registered trademark), and other adequate systems,
and/or next-generation systems that are enhanced based on
these.
[0227] The order of processes, sequences, flowcharts and so on that
have been used to describe the examples/embodiments herein may be
re-ordered as long as inconsistencies do not arise. For example,
although various methods have been illustrated in this description
with various components of steps in exemplary orders, the specific
orders that illustrated herein are by no means limiting.
[0228] Now, although the present invention has been described in
detail above, it should be obvious to a person skilled in the art
that the present invention is by no means limited to the
embodiments described herein. For example, the above-described
embodiments may be used individually or in combinations. The
present invention can be implemented with various corrections and
in various modifications, without departing from the spirit and
scope of the present invention defined by the recitations of
claims. Consequently, the description herein is provided only for
the purpose of explaining example s, and should by no means be
construed to limit the present invention in any way.
[0229] The disclosure of Japanese Patent Application No.
2015-255030, filed on Dec. 25, 2015, including the specification,
drawings and abstract, is incorporated herein by reference in its
entirety.
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