U.S. patent application number 16/702051 was filed with the patent office on 2020-04-02 for method and apparatus for performing repetitive transmission of information in time division duplex based cell in wireless commun.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Tae-Han BAE, Seung-Hoon CHOI, Hee-Don GHA, Hyoung-Ju JI, Dong-Han KIM, Youn-Sun KIM, Young-Bum KIM, Young-Woo KWAK, Hyo-Jin LEE, Ju-Ho LEE, Hoon-Dong NOH, Jin-Young OH, Cheol-Kyu SHIN, Jeong-Ho YEO.
Application Number | 20200106561 16/702051 |
Document ID | / |
Family ID | 56356194 |
Filed Date | 2020-04-02 |
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United States Patent
Application |
20200106561 |
Kind Code |
A1 |
CHOI; Seung-Hoon ; et
al. |
April 2, 2020 |
METHOD AND APPARATUS FOR PERFORMING REPETITIVE TRANSMISSION OF
INFORMATION IN TIME DIVISION DUPLEX BASED CELL IN WIRELESS
COMMUNICATION SYSTEM
Abstract
Methods and apparatuses are provided in a wireless communication
system in which DCI is received from a base station and includes a
subband indicator indicating a subband among at least one subband
configured for the terminal as an active subband and information
indicating at least one frequency resource allocated for a PDSCH
within the active subband. The active subband is identified based
on the subband indicator. The PDSCH is received from the base
station in the active subband based on the information. A size of
the DCI is configured based on a size of the active subband.
Inventors: |
CHOI; Seung-Hoon;
(Gyeonggi-do, KR) ; KIM; Young-Bum; (Seoul,
KR) ; LEE; Hyo-Jin; (Gyeonggi-do, KR) ; OH;
Jin-Young; (Seoul, KR) ; KIM; Dong-Han;
(Gyeonggi-do, KR) ; LEE; Ju-Ho; (Gyeonggi-do,
KR) ; KIM; Youn-Sun; (Gyeonggi-do, KR) ; JI;
Hyoung-Ju; (Seoul, KR) ; GHA; Hee-Don;
(Gyeonggi-do, KR) ; BAE; Tae-Han; (Seoul, KR)
; YEO; Jeong-Ho; (Gyeonggi-do, KR) ; KWAK;
Young-Woo; (Gyeonggi-do, KR) ; NOH; Hoon-Dong;
(Gyeonggi-do, KR) ; SHIN; Cheol-Kyu; (Gyeonggi-do,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Gyeonggi-do |
|
KR |
|
|
Family ID: |
56356194 |
Appl. No.: |
16/702051 |
Filed: |
December 3, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15542609 |
Jul 10, 2017 |
10536242 |
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PCT/KR2016/000188 |
Jan 8, 2016 |
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16702051 |
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62101632 |
Jan 9, 2015 |
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62139347 |
Mar 27, 2015 |
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62145207 |
Apr 9, 2015 |
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62161398 |
May 14, 2015 |
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62174886 |
Jun 12, 2015 |
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62196585 |
Jul 24, 2015 |
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62204694 |
Aug 13, 2015 |
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62240270 |
Oct 12, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 1/1858 20130101;
H04L 1/189 20130101; H04L 1/08 20130101; H04L 1/1896 20130101; H04J
11/00 20130101; H04L 5/0055 20130101; H04L 5/1469 20130101; H04L
1/1887 20130101; H04L 1/1812 20130101; H04L 5/0044 20130101; H04L
1/18 20130101; H04L 5/0053 20130101; H04B 7/26 20130101 |
International
Class: |
H04L 1/18 20060101
H04L001/18; H04L 5/00 20060101 H04L005/00; H04L 5/14 20060101
H04L005/14; H04B 7/26 20060101 H04B007/26; H04J 11/00 20060101
H04J011/00; H04L 1/08 20060101 H04L001/08 |
Claims
1. A method performed by a terminal in a wireless communication
system, the method comprising: receiving, from a base station,
downlink control information (DCI) including a subband indicator
indicating a subband among at least one subband configured for the
terminal as an active subband and information indicating at least
one frequency resource allocated for a physical downlink shared
channel (PDSCH) within the active subband; identifying the active
subband based on the subband indicator; and receiving, from the
base station, the PDSCH in the active subband based on the
information, wherein a size of the DCI is configured based on a
size of the active subband.
2. The method of claim 1, further comprising: receiving, from the
base station, another DCI including another subband indicator
indicating another subband among the at least one subband as the
active subband; and receiving, from the base station, another PDSCH
in the another subband based on a predetermined time delay required
for active subband change in the terminal.
3. The method of claim 2, wherein the predetermined time delay is
determined based on a predetermined value that is set for the
terminal.
4. The method of claim 2, wherein further comprising: receiving,
from the base station, another information associated with the
predetermined time delay.
5. A method performed by a base station in a wireless communication
system, the method comprising: configuring downlink control
information (DCI) including a subband indicator indicating a
subband among at least one subband configured for a terminal as an
active subband and information indicating at least one frequency
resource allocated for physical downlink shared channel (PDSCH)
within the active subband; transmitting, to the terminal, the
configured DCI; and transmitting, to the terminal, the PDSCH in the
active subband based on the information, wherein a size of the DCI
is configured based on a size of the active subband.
6. The method of claim 5, further comprising: transmitting, to the
terminal, another DCI including another subband indicator
indicating another subband among the at least one subband as the
active subband; and transmitting, to the terminal, another PDSCH in
the another subband based on a predetermined time delay required
for active subband change in the terminal.
7. The method of claim 6, wherein the predetermined time delay is
determined based on a predetermined value that is set for the
terminal.
8. The method of claim 6, further comprising: transmitting, to the
terminal, another information associated with the predetermined
time delay.
9. A terminal in a wireless communication system, the terminal
comprising: a transceiver; and at least one processor configured
to: receive, from a base station, downlink control information
(DCI) including a subband indicator indicating a subband among at
least one subband configured for the terminal as an active subband
and information indicating at least one frequency resource
allocated for physical downlink shared channel (PDSCH) within the
active subband; identify the active subband based on the subband
indicator; and receive, from the base station, the PDSCH in the
active subband based on the information, wherein a size of the DCI
is configured based on a size of the active subband.
10. The terminal of claim 9, wherein the at least one processor is
further configured to: receive, from the base station, another DCI
including another subband indicator indicating another subband
among the at least one subband as the active subband; and receive,
from the base station, another PDSCH in the another subband based
on a predetermined time delay required for active subband change in
the terminal.
11. The terminal of claim 10, wherein the predetermined time delay
is determined based on a predetermined value that is set for the
terminal.
12. The terminal of claim 10, wherein at least one processor is
further configured to: receive, from the base station, another
information associated with the predetermined time delay.
13. A base station in a wireless communication system, the base
station comprising: a transceiver; and at least one processor
configured to: configure downlink control information (DCI)
including a subband indicator indicating a subband among at least
one subband configured for a terminal as an active subband and
information indicating at least one frequency resource allocated
for a physical downlink shared channel (PDSCH) within the active
subband; transmit, to the terminal, the configured DCI; and
transmit, to the terminal, the PDSCH in the active subband based on
the information, wherein a size of the DCI is configured based on
the size of the active subband.
14. The base station of claim 13, wherein the at least one
processor is further configured to: transmit, to the terminal,
another DCI including another subband indicator indicating another
subband among the at least one subband as the active subband; and
transmit, to the terminal, another PDSCH in the another subband
based on a predetermined time delay required for active subband
change in the terminal.
15. The base station of claim 14, wherein the predetermined time
delay is determined based on a predetermined value that is set for
the terminal.
16. The base station of claim 14, wherein the at least one
processor is further configured to: transmit, to the terminal,
another information associated with the predetermined time delay.
Description
PRIORITY
[0001] This application is a Continuation Application of U.S.
application Ser. No. 15/542,609, filed in the U.S. Patent and
Trademark Office (USPTO) on Jul. 10, 2017, which is a U.S. National
Phase Entry of International Application No. PCT/KR2016/000188,
filed on Jan. 8, 2016, which claims priority to U.S. Provisional
Application Nos. 62/101,632, 62/139,347, 62/145,207, 62/161,398,
62/174,886, 62/196,585, 62/204,694, and 62/240,270, which were
filed in the USPTO on Jan. 9, 2015, Mar. 27, 2015, Apr. 9, 2015,
May 14, 2015, Jun. 12, 2015, Jul. 24, 2015, Aug. 13, 2015, and Oct.
12, 2015, respectively, the contents of all of which are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to cellular wireless
communication systems, and more specifically, to schemes for
communicating control channels by low-cost terminals. Further, the
present disclosure relates to schemes for transmitting channel
information on serving cells to base stations in wireless
communication systems having multiple cells. Further, the present
disclosure relates to scheduling schemes for data communication by
lower-cost terminals.
DISCUSSION OF RELATED ART
[0003] To meet the demand for wireless data traffic having
increased since deployment of 4G (4.sup.th-Generation)
communication systems, efforts have been made to develop an
improved 5G (5.sup.th-Generation) or pre-5G communication system.
Therefore, the 5G or pre-5G communication system is also called a
`Beyond 4G Network` or a `Post LTE System`.
[0004] The 5G communication system is considered to be implemented
in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to
accomplish higher data rates. To decrease propagation loss of the
radio waves and increase the transmission distance, the
beamforming, massive multiple-input multiple-output (MIMO), Full.
Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming,
large scale antenna techniques are discussed in 5G communication
systems.
[0005] In addition, in 5G communication systems, development for
system network improvement is under way based on advanced small
cells, cloud Radio Access Networks (RANs), ultra-dense networks,
device-to-device (D2D) communication, wireless backhaul, moving
network, cooperative communication, Coordinated Multi-Points
(CoMP), reception-end interference cancellation and the like.
[0006] In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and
sliding window superposition coding (SWSC) as an advanced coding
modulation (ACM), and filter bank multi carrier (FBMC),
non-orthogonal multiple access (NOMA), and sparse code multiple
access (SCMA) as an advanced access technology have been
developed.
[0007] Generally, mobile communication systems have been developed
to guarantee user activity while providing voice services. Mobile
communication systems have been expanding service areas from voice
to data, and the systems have been grown to provide high-speed data
services. However, more evolved mobile communication systems are
required to live up to users' desire for higher-speed services and
lacking resources that are faced by the current mobile
communication systems.
[0008] Mobile communication system advances to broadband wireless
communication system to provide high data rate and high-quality
packet data services, such as 3rd generation partnership (3GPP)
high speed packet access (HSPA), long term evolution (LTE), or
evolved universal terrestrial radio access (E-UTRA), 3GPP2 high
rate packet data (HRPD), ultra mobile broadband (UMB), and
institute of electrical and electronics engineers (IEEE) 802.16e
communication standards.
[0009] The 3GPP LTE is now underway for standardization as a
next-generation communication system. LTE is the technology
implementing high-speed packet-based communication with a
transmission speed up to 100 Mbps. To that end, various approaches
are being discussed, and some examples include simplifying the
network architecture to reduce the number of nodes over a
communication path and making radio protocols as close to radio
channel as possible.
[0010] LTE system adopts orthogonal frequency division multiplexing
(OFDM) for downlink and single carrier frequency division multiple
access (SC-FDMA) for uplink. Such multiple access scheme allocates
and operates time-frequency resources carrying data or control
information per user not to overlap, i.e., to maintain
orthogonality, to thereby differentiate each user's data or control
information. The orthogonal frequency division multiple access
(OFDM) transmission scheme transmits data via multiple carriers,
and this is a sort of multi-carrier modulation scheme that
parallelizes symbols inputted in series and modulates the same into
multiple multi-carriers, i.e., multiple subcarrier channels with
mutual orthogonality and transmits the same.
[0011] The LTE system adopts HARQ (Hybrid Automatic Repeat request)
scheme that re-transmits corresponding data through the physical
layer in case decoding fails at the initial stage of transmission.
By the HARQ scheme, if the receiver fails to precisely decode data,
the receiver transmits information indicating the decoding failure
(NACK; Negative Acknowledgement) to the transmitter so that the
transmitter may re-transmit the corresponding data through the
physical layer. The receiver raises the data reception capability
by combining the data re-transmitted by the transmitter with the
data for which decoding has failed. Further, in case the receiver
precisely decode data, the receiver may transmit information
indicating decoding succeeds (ACK; Acknowledgement) to the
transmitter so that the transmitter may transmit new data.
[0012] FIG. 1 is a view illustrating a basic structure of
time-frequency domain which is radio resource domain where the data
or control channel is transmitted on downlink in the LTE
system.
[0013] In FIG. 1, the horizontal axis refers to the time domain,
and the vertical axis refers to the frequency domain. In the time
domain, the minimum transmission unit is an OFDM symbol, and
N.sub.symb 102 OFDM symbols come together to configure one slot
106, and two slots come together to configure one subframe 105. The
slot is 0.5 ms long, and the subframe is 1.0 ms long. One radio
frame 114 is a time domain unit consisting of ten subframes. In the
frequency domain, the minimum transmission unit is subcarrier, and
the bandwidth of the overall system transmission band consists of a
total of NBW (104) subcarriers.
[0014] In the OFDM scheme, a modulated signal is positioned in a
2-dimensional resource constituted of time and frequency. The
resources on the time axis are differentiated by different OFDM
symbols and they are orthogonal to each other. The resources on the
frequency axis are differentiated by different subcarriers and they
are also orthogonal to each other. That is, in the OFDM scheme, one
minimum unit resource may be indicated by designating a particular
OFDM symbol on the time axis and a particular subcarrier on the
frequency axis, and this is called a resource element (RE) 112.
Since different REs maintain the orthogonality even when undergoing
frequency selective channel, signals transmitted via different REs
may be received on the reception side without mutual
interference.
[0015] The physical channel is a channel of a physical layer
transmitting a modulated symbol obtained by modulating one or more
coded bit streams. The orthogonal frequency division multiple
access (OFDMA) system may configure and transmit a plurality of
physical channels depending on the receiver or the purpose of
information streams transmitted. The RE where one physical channel
should be disposed and transmitted should be previously agreed
between the transmitter and the receiver, and such rule is referred
to as mapping.
[0016] In the time-frequency domain, the basic unit of resources is
RE 112, and this may be represented with OFDM symbol indexes and
subframe indexes. Resource block (RB) 108 or physical resource
block (PRB) is defined with N.sub.symb (102) continuous OFDM
symbols in the time domain and N.sub.RB (110) continuous
subcarriers in the frequency domain. Accordingly, one RB 108
includes Nsymb.times.NRB REs (112). Generally, the minimum
transmission unit of data is RB. Generally, in the LTE system,
Nsymb=7, NRB=12, and, NBW and NRB are proportional to the bandwidth
of system transmission band. The data rate increases in proportion
to the number of RBs scheduled for terminal. The LTE system defines
and operates six transmission bandwidths. For the frequency
division duplex (FDD) system differentiating and operating downlink
and uplink with frequencies, downlink transmission bandwidth may
differ from uplink transmission bandwidth. The channel bandwidth
refers to a radio frequency (RF) bandwidth corresponding to the
system transmission bandwidth.
[0017] Table 1 represents the correlation between system
transmission bandwidth and channel bandwidth defined in the LTE
system. For example, the LTE system having a 10 MHz channel
bandwidth has a transmission bandwidth consisting of 50 RBs.
TABLE-US-00001 TABLE 1 Channel bandwidth BW.sub.Channel [MHz] 1.4 3
5 10 15 20 Transmission bandwidth 6 15 25 50 75 100 configuration
N.sub.RB
[0018] Downlink control information is transmitted within first N
OFDM symbols in the subframe. Generally, N={1, 2, 3}. Accordingly,
N is varied depending on the amount of control information to be
transmitted in the current subframe. The control information may
include a control channel transmission period indicator indicating
how many OFDM symbols the control information is transmitted over,
scheduling information on downlink data or uplink data, and HARQ
ACK/NACK signal.
[0019] In the LTE system, the scheduling information on downlink
data or uplink data is transferred through downlink control
information (DCI) from the base station to the terminal. Uplink
(UL) means radio link through which the terminal transmits data or
control signal to the base station, and downlink (DL) means radio
link through which the base station transmits data or control
signal to the terminal. DCI defines various formats, and a defined
DCI format applies and operates depending on whether scheduling
information (i.e., UL grant) for uplink data or scheduling
information (i.e., DL grant) for downlink data, whether control
information is small-sized compact DCI, whether spatial
multiplexing applies using multiple antennas, and whether DCI for
power control or not. For example, DCI format 1 that is scheduling
control information (DL grant) for downlink data may be configured
to include at least the following control information.
[0020] Resource allocation type 0/1 flag): notifies whether
resource allocation type is type 0 or type 1. Type 0 allocates
resources in RBG (resource block group) units by applying bitmap
scheme. In the LTE system, the basic unit of scheduling is RB
(resource block) represented in time and frequency domain
resources, and RBG consists of a plurality of RBs and becomes the
basic unit of scheduling in the type 0 scheme. Type 1 allows for
allocation of a particular RB in the RBG.
[0021] Resource block assignment: notifies RB allocated for data
transmission. resource represented according to system bandwidth
and resource allocation scheme is determined.
[0022] Modulation and coding scheme (MCS: notifies the size of
transport block that is data to be transmitted and modulation
scheme used for data transmission.
[0023] HARQ process number: notifies process number of HARQ.
[0024] New data indicator: notifies whether HARQ initial
transmission or re-transmission.
[0025] Redundancy version: notifies redundancy version of HARQ.
[0026] TPC (Transmit Power Control) command for PUCCH (Physical
Uplink Control CHannel): notifies transmit power control command
for uplink control channel PUCCH.
[0027] The DCI undergoes channel coding and modulation and is
transmitted through downlink physical control channel PDCCH
(Physical downlink control channel) or EPDCCH (Enhanced PDCCH). The
PDCCH region that is a control channel region and the ePDCCH region
transmitted in the data channel region are split in the time domain
and transmitted. This is for quickly receiving and demodulating
control channel signals.
[0028] Generally, the DCI is subject to channel coding
independently for each terminal and is then configured of
independent PDCCH and transmitted. PDCCH in the time domain is
mapped and transmitted during control channel transmission period.
The position of mapping of PDCCH in the frequency domain is
determined by the identifier (ID) of each terminal and spread over
the overall system transmission band. That is, in such form, one
control channel is split into smaller units of control channels
that are then distributed over the overall downlink transmission
band.
[0029] The downlink data is transmitted through physical channel
for downlink data transmission, PDSCH (physical downlink shared
channel). PDSCH is transmitted after the control channel
transmission period, and the specific mapping position in the
frequency domain, modulation scheme, or other scheduling
information are notified by the DCI transmitted through the
PDCCH.
[0030] Through the MCS consisting of five bits among the control
information constituting the DCI, the base station notifies the
terminal of the modulation scheme that has applied to the PDSCH to
be transmitted and the size of data to be transmitted, i.e.,
transport block size (TBS). The TBS corresponds to the size before
applying channel coding for error correction to the data (i.e.,
transport block (TB)) to be transmitted by the base station.
[0031] Physical uplink channels are generally divided into control
channels (PUCCH) and data channels (PUSCH). When there is no data
channel, a response channel to the downlink data channel and other
feedback information may be transmitted through the control
channel, and when the data channel is present, such channel and
data may be transmitted through the data channel.
[0032] The LTE system supports the following modulation schemes:
quadrature phase shift keying (QPSK), 16 quadrature amplitude
modulation (16QAM), 64QAM, and their respective modulation orders
(i.e., Qm) are 2, 4, and 6. That is, QPSK may transmit two bits per
symbol, 16QAM four bits per symbol, and 64QAM six bits per
symbol.
[0033] Generally, time division duplex (TDD) communication system
uses common frequency for downlink and uplink and operate
distinctively between communication of uplink signals and
communication of downlink signals in the time domain. LTE TDD
transmits uplink signals and downlink signals with the signals
differentiated per subframe. Depending on uplink and downlink
traffic load, uplink/downlink subframes may be evenly separated or
more subframes may be assigned for downlink than uplink or more
subframes may be assigned for uplink than downlink.
TABLE-US-00002 TABLE 2 Uplink-downlink Subframe number
configuration 0 1 2 3 4 5 6 7 8 9 0 D S U U U D S U U U 1 D S U U D
D S U U D 2 D S U D D D S U D D 3 D S U U U D D D D D 4 D S U U D D
D D D D 5 D S U D D D D D D D 6 D S U U U D S U U D
[0034] Table 2 shows TDD uplink-downlink configuration defined in
LTE. In Table 2, D denotes subframe configured for downlink
transmission, U denotes subframe configured for uplink
transmission, and S denotes special subframe consisting of downlink
pilot time slot (DwPTS) and guard period (GP), uplink pilot time
slot (UpPTS). In DwPTS, like normal subframe, control information
may be transmitted on downlink, and in case DwPTS is long enough
depending on the configuration of the special subframe, downlink
data transmission is also possible. GP is an interval to take
transmission shift from downlink to uplink and its length is
determined depending on network settings. UpPTS is used for random
access channel (RACH) transmission for random access or sounding
reference signal (SRS) transmission of terminal necessary to
estimate uplink channel status.
[0035] For example, in case of TDD UL-DL configuration #6, downlink
data and control information may be transmitted in subframes #0,
#5, and #9, and uplink data and control information may be
transmitted in subframes #2, #3, #4, #7, and #8. In subframes #1
and #6 corresponding to the special subframe, downlink control
information, and in some cases, downlink data, may be transmitted,
and SRS or RACH transmission is possible on uplink.
[0036] In TDD system, downlink or uplink signal transmission is
permitted only for a particular time period, and thus, specific
timing relations between uplink/downlink physical channels mutually
related, such as control channel for data scheduling, data channel
scheduled, and HARQ ACK/NACK channel corresponding to data channel
need to be defined.
[0037] Further, 3GPP LTE Rel-10 adopted bandwidth expanding
technology to support more data traffic than LTE rel-8. The above
technology which is called bandwidth extension or Carrier
Aggregation (CA) may extend band to increase the volume of data
transmitted as much as the band extended as compared with LTE rel-8
terminal transmitting data within a single band. Each of the bands
is called component carrier (CC), and LTE rel-8 terminal has been
specified to have one component carrier for each of downlink and
uplink. Further, downlink component carrier and uplink component
carrier connected thereto via system information block (SIB)-2 are
collectively called cell. The SIB-2 connection between the downlink
component carrier and the uplink component carrier is transmitted
through a terminal-dedicated signal. CA-supporting terminal may
receive downlink data through multiple serving cells and transmit
uplink data.
[0038] In Rel-10, when the base station has difficulty sending
PDCCH (physical downlink control channel) in a particular serving
cell to a particular terminal, a carrier indicator field (CIF) may
be configured as a field to indicate that PDCCH is transmitted
through other serving cell and the corresponding PDCCH indicates
the PDSCH (physical downlink shared channel) or PUSCH (physical
uplink shared channel) of other serving cell. The CIF may be
configured in CA-supporting terminal. The CIF has been defined to
be able to indicate other serving cell by adding three bits to the
PDCCH information in the particular serving cell, and the CIF is
included only upon cross carrier scheduling, and in case CIF is not
included, cross-carrier scheduling is not performed. When CIF is
present in downlink allocation information (DL assignment), the CIF
indicates the serving cell where the PDSCH scheduled by DL
assignment is to be transmitted, and when the CIF is present in
uplink resource allocation information (UL grant), the CIF
indicates the serving cell where the PUSCH scheduled by the UL
grant is to be transmitted.
[0039] As such, LTE-10 defines the CA, enabling multiple serving
cells to be configured for a terminal. The terminal periodically or
aperiodically transmits channel information on multiple serving
cells to the base station in order for data scheduling on the base
station.
[0040] Meanwhile, the concept of expanding the number of serving
cells up to 32 using unlicensed bands for LTE-13 is now in
discussion. In such case, transmissions of channel information on
multiple serving cells in one subframe may conflict with each
other. Accordingly, highlighted is a need for a method for
supporting an operation of the terminal that may periodically
transmit channel information on as many serving cells as possible
in one subframe.
[0041] Further, for low-cost terminals having the maximum bandwidth
limited to less than 20 MHz (e.g., 1.4 MHz), there is a need for
communication operations differentiated from those of typical
legacy LTE terminals because the low-cost terminals support only
some subband in the whole channel bandwidth.
SUMMARY
[0042] According to the present disclosure, there are provided a
control channel transmission method and apparatus for low-cost
terminals supporting repetitive transmission to enhance
coverage.
[0043] According to the present disclosure, there are provided a
method and apparatus for transmitting channel information on
multiple serving cells by a terminal without wasting transmission
resources of downlink control channels in a wireless communication
system supportive of carrier aggregation. According to the present
disclosure, there are provided a method and apparatus for
increasing transmission by performing scheduling optimized for
serving cells by receiving channel information periodically
transmitted from a terminal.
[0044] According to the present disclosure, there are provided
schemes for transmitting channel information on multiple serving
cells by a terminal without wasting transmission resources of
downlink control channels in a wireless communication system
supportive of carrier aggregation.
[0045] There are proposed a method for configuring periodic channel
information transmission for multiple serving cells without wasting
PDCCH transmission resources by the base station under the CA
situation and a method for transmitting channel information for the
serving cells.
[0046] According to the present disclosure, described is a method
for configuring UCI PUSCH (uplink control information PUSCH)
transmission for allowing the terminal to perform periodic channel
information transmission operation on multiple serving cells
without the base station wasting PDCCH transmission resources.
[0047] According to the present disclosure, there are provided
scheduling methods and communication methods for operating both
normal LTE terminal and low-cost terminal in the same system.
[0048] According to the present disclosure, a method performed by a
terminal in a wireless communication system is provided. DCI is
received from a base station and includes a subband indicator
indicating a subband among at least one subband configured for the
terminal as an active subband and information indicating at least
one frequency resource allocated for a PDSCH within the active
subband. The active subband is identified based on the subband
indicator. The PDSCH is received from the base station in the
active subband based on the information. A size of the DCI is
configured based on a size of the active subband.
[0049] According to the present disclosure, a method performed by a
base station in a wireless communication system is provided. DCI is
configured including a subband indicator indicating a subband among
at least one subband configured for a terminal as an active subband
and information indicating at least one frequency resource
allocated for PDSCH within the active subband. The configured DCI
is transmitted to the terminal. The PDSCH is transmitted to the
terminal in the active subband based on the information. A size of
the DCI is configured based on a size of the active subband.
[0050] According to the present disclosure, a terminal is provided
in a wireless communication system. The terminal includes a
transceiver and at least one processor. The at least one processor
is configured to receive, from a base station, DCI including a
subband indicator indicating a subband among at least one subband
configured for the terminal as an active subband and information
indicating at least one frequency resource allocated for PDSCH
within the active subband. The at least one processor is also
configured to identify the active subband based on the subband
indicator, and receive, from the base station, the PDSCH in the
active subband based on the information. A size of the DCI is
configured based on a size of the active subband.
[0051] According to the present disclosure, a base station is
provided in a wireless communication system. The base station
includes a transceiver and at least one processor. The at least one
processor is configured to configure DCI including a subband
indicator indicating a subband among at least one subband
configured for a terminal as an active subband and information
indicating at least one frequency resource allocated for a PDSCH
within the active subband. The at least one processor is also
configured to transmit, to the terminal, the configured DCI, and
transmit, to the terminal, the PDSCH in the active subband based on
the information. A size of the DCI is configured based on the size
of the active subband.
[0052] The present disclosure provides communication methods for
low-cost terminals to allow LTE terminals and low-cost terminals to
efficiently co-exist in the system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a view illustrating a basic structure of
time-frequency domain which is radio resource domain where the data
or control channel is transmitted on downlink in the LTE
system;
[0054] FIG. 2 is a view illustrating an operation example of
subframes in a TDD frame;
[0055] FIG. 3 is a view illustrating another operation example of
subframes in a TDD frame;
[0056] FIG. 4 is a view illustrating a problematic situation to be
solved according to the present disclosure;
[0057] FIG. 5 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0058] FIG. 6a is a flowchart illustrating an operation by a base
station for a control channel transmission method according to an
embodiment of the present disclosure;
[0059] FIG. 6b is a flowchart illustrating an operation by a
terminal for a control channel transmission method according to an
embodiment of the present disclosure;
[0060] FIG. 7 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0061] FIG. 8a is a view illustrating a method for transmitting a
control channel by a base station according to an embodiment of the
present disclosure;
[0062] FIG. 8b is a view illustrating a method for transmitting a
control channel by a terminal according to an embodiment of the
present disclosure;
[0063] FIG. 9 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0064] FIG. 10a is a flowchart illustrating an operation by a base
station for a control channel transmission method according to an
embodiment of the present disclosure;
[0065] FIG. 10b is a flowchart illustrating an operation by a
terminal for a control channel transmission method according to an
embodiment of the present disclosure;
[0066] FIG. 11 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0067] FIG. 12 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0068] FIG. 13 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0069] FIG. 14 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure;
[0070] FIG. 15a is a view illustrating a communication network
including an LAA cell to which the present disclosure applies;
[0071] FIG. 15b is a view illustrating a communication network
including an LAA cell to which the present disclosure applies;
[0072] FIG. 16 is a view illustrating a method for transmitting
channel information by grouping serving cells according to an
embodiment of the present disclosure;
[0073] FIG. 17 is a view illustrating a method for communicating
periodic channel information by a base station and a terminal
according to an embodiment of the present disclosure;
[0074] FIG. 18 is a concept view illustrating an example of
configuring and operating subband where the low-cost terminal
operates within the system transmission bandwidth according to an
embodiment of the present disclosure;
[0075] FIG. 19 is a concept view illustrating an example in which
DCI size is varied depending on the type of terminal according to
an embodiment of the present disclosure;
[0076] FIG. 20 is a view illustrating a scheduling procedure by a
base station when a normal LTE terminal and a low-cost terminal
co-exist in the same system according to an embodiment of the
present disclosure;
[0077] FIG. 21 is a view illustrating a procedure of obtaining DCI
by a low-cost terminal operating according to an embodiment of the
present disclosure;
[0078] FIG. 22 is a concept view illustrating an example of
operating without explicitly configuring a subband where a low-cost
terminal operates in a system transmission bandwidth according to
an embodiment of the present disclosure;
[0079] FIG. 23 is a concept view illustrating a method for
determining a DCI size according to an embodiment of the present
disclosure;
[0080] FIG. 24 is a view illustrating a scheduling procedure by a
base station when a normal LTE terminal and a low-cost terminal
co-exist in the same system according to an embodiment of the
present disclosure;
[0081] FIG. 25 is a view illustrating a procedure of obtaining DCI
by a low-cost terminal operating according to an embodiment of the
present disclosure;
[0082] FIG. 26 is a concept view illustrating an example of
previously configuring and dynamically varying a subband where a
low-cost terminal operates in a system transmission bandwidth
according to an embodiment of the present disclosure;
[0083] FIG. 27 is a concept view illustrating an example of a
method for indicating a subband in an FDD system according to an
embodiment of the present disclosure;
[0084] FIG. 28 is a view illustrating an exemplary configuration of
a base station for implementing an embodiment of the present
disclosure; and
[0085] FIG. 29 is a view illustrating an exemplary configuration of
a terminal for implementing an embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0086] Hereinafter, embodiments of the present disclosure are
described in detail with reference to the accompanying drawings.
When determined to make the subject matter of the present
disclosure unclear, the detailed of the known functions or
configurations may be skipped. The terms as used herein are defined
considering the functions in the present disclosure and may be
replaced with other terms according to the intention or practice of
the user or operator. Therefore, the terms should be defined based
on the overall disclosure.
[0087] Hereinafter, according to this disclosure, the long term
evolution (LTE) system and the LTE-advanced (LTE-A) system are
described as examples, but the present disclosure may also apply to
other communication systems adopting base station scheduling
without limited thereto. The description of embodiments of the
present disclosure primarily targets advanced E-UTRA (or LTE-A)
supporting carrier aggregation but the subject matter of the
present disclosure may also be applicable to other communication
systems with a similar technical background with minor changes
without significantly departing from the scope of the present
disclosure, and this may be possible under the determination of
those skilled in the art to which the present disclosure pertains.
For example, the subject matter of the present disclosure may be
applicable to multicarrier HSPA supporting carrier aggregation.
[0088] Before detailing the present disclosure, some terms as used
herein may be interpreted as follows, for example. However, it
should be noted that the present disclosure is not limited
thereto.
[0089] The base station is an entity communicating with a UE and
may be denoted BS, NodeB (NB), eNodeB (eNB), or AP (Access
Point).
[0090] The user equipment is an entity communicating with a base
station, may be denoted UE, mobile station (MS), mobile equipment
(ME), device, or terminal.
[0091] Reference signal (RS) is a signal that enables the terminal
to estimate channel, and this reference signal may be received from
the base station. The reference signals for the LTE communication
system include the common reference signal (CRS) and the
demodulation reference signal (DMRS), a dedicated reference
signal.
[0092] The CRS is a reference signal transmitted over the overall
downlink band and receivable by all the UEs and is used for channel
estimation, configuring feedback information by the UE, and
demodulation of data channel. The DMRS is a reference signal
transmitted over the overall downlink band. The DMRS is used for
demodulation of a data channel by a particular UE and channel
estimation, but not used for configuring feedback information
unlike the CRS. Accordingly, the DMRS is transmitted through a PRB
resource that is to be scheduled by the UE.
[0093] HARQ-ACK signal refers to an acknowledge (ACK) or negative
ACK (HACK) signal transmitted in the HARQ procedure and is simply
referred to as `HARQ-ACK.`
[0094] Hereinafter, according to the present disclosure, a scheme
for supporting repetitive transmission by a low-cost terminal is
described with reference to FIGS. 2 to 14, a periodic channel
information transmission scheme in a system supporting multiple
serving cells is described in connection with FIGS. 15 to 17, a
resource allocation and communication scheme by a low-cost terminal
is described in connection with FIGS. 18 to 27, and devices for
supporting embodiments of the present disclosure are described in
connection with FIGS. 28 and 29.
[0095] In LTE TDD system, first, the uplink/downlink timing
relation of physical downlink shared channel (PDSCH), which is a
physical channel for downlink data transmission, and its
corresponding physical uplink control channel (PUCCH) or physical
uplink shared channel (PUSCH) which is a physical channel through
which uplink HARQ ACK/NACK is transmitted is as follows.
[0096] The terminal, if receiving PDSCH that has been transmitted
in subframe n-k from the base station, may transmit uplink HARQ
ACK/NACK for the PDSCH in uplink subframe n. Here, k is a component
of set K, and K is defined in Table 3.
TABLE-US-00003 TABLE 3 UL-DL Subframe n Configuration 0 1 2 3 4 5 6
7 8 9 0 -- -- 6 -- 4 -- -- 6 -- 4 1 -- -- 7, 6 4 -- -- -- 7, 6 4 --
2 -- -- 8, 7, 4, 6 -- -- -- -- 8, 7, 4, 6 -- -- 3 -- -- 7, 6, 11 6,
5 5, 4 -- -- -- -- -- 4 -- -- 12, 8, 7, 11 6, 5, 4, 7 -- -- -- --
-- -- 5 -- -- 13, 12, 9, 8, 7, 5, 4, 11, 6 -- -- -- -- -- -- -- 6
-- -- 7 7 5 -- -- 7 7 --
[0097] Table 4 re-summarizes, according to the definitions in Table
3, subframes where uplink HARQ ACK/NACK is transmitted for PDSCH
when the PDSCH is transmitted in each downlink subframe (D) or
special subframe (S) n in each TDD UL-DL configuration.
TABLE-US-00004 TABLE 4 UL-DL Subframe n Configuration 0 1 2 3 4 5 6
7 8 9 0 D S U U U D S U U U 4 6 4 6 1 D S U U D D S U U D 7 6 4 7 6
4 2 D S U D D D S U D D 7 6 4 8 7 6 4 8 3 D S U U U D D D D D 4 11
7 6 6 5 5 4 D S U U D D D D D D 12 6 8 7 7 6 5 4 5 D S U D D D D D
D D 12 6 9 8 7 6 5 4 13 6 D S U U D D S U U D 7 7 8 7 7 5
[0098] FIG. 2 is a view illustrating an operation example of
subframes in a TDD frame.
[0099] Table 4 is described below with reference to FIG. 2. Here,
FIG. 2 is a view exemplifying, as per the definitions in Table 4,
the subframe where uplink HARQ ACK/NACK corresponding to PDSCH is
transmitted when the PDSCH is transmitted in each downlink or
special subframe in TDD UL-DL configuration #6 of Table 4.
[0100] For example, the uplink HARQ ACK/NACK corresponding to the
PDSCH 201 transmitted from the base station in subframe #0 211 of
radio frame i is transmitted by the terminal in subframe #7 of
radio frame i (203). Here, the downlink control information DCI
including scheduling information on PDSCH 201 is transmitted
through PDCCH in the same subframe 211 as the subframe transmitted
where the PDSCH is transmitted. As another example, the uplink HARQ
ACK/NACK corresponding to the PDSCH 205 transmitted from the base
station in subframe #9 215 of radio frame i is transmitted by the
terminal in subframe #4 of radio frame i+1 (207). Likewise, the
downlink control information DCI including scheduling information
on PDSCH 205 is transmitted through PDCCH in the same subframe 215
as the subframe transmitted where the PDSCH is transmitted.
[0101] In LTE system, downlink HARQ adopts asynchronous HARQ
scheme, which is a scheme where the data retransmission time is not
fixed. As used herein, downlink HARQ refers to an HARQ (initial
transmission, ACK/NACK, or retransmission) whose transmission
direction is downlink. The reason why downlink HARQ adopts
asynchronous HARQ scheme is that not fixing transmission time would
make little trouble even because in the LTE TDD system downlink
transmission generally use more subframes than uplink transmission.
That is, in case the base station receives feedback of HARQ NACK
from the terminal for the transmitted HARQ initial transmission
data, the base station freely determines the transmission time of
next HARQ retransmission data by scheduling operation. The terminal
buffers the HARQ data determined to have an error as a result of
determining the received data for HARQ operation and then performs
combining with next HARQ retransmission data. Here, in order to
maintain the reception buffer capacity of the terminal within a
predetermined range, the maximum number of downlink HARQ processes
per TDD UL-DL configuration is defined as in Table 5. One HARQ
process is mapped to one subframe in the time domain.
TABLE-US-00005 TABLE 5 TDD UL/DL Maximum number of configuration
HARQ processes 0 4 1 7 2 10 3 9 4 12 5 15 6 6
[0102] Referring to the example shown in FIG. 2, the terminal, if
determining that the PDSCH 201 transmitted from the base station
subframe #0 211 of radio frame i has an error, transmits HARQ NACK
in subframe #7 of radio frame i (203). When receiving the HARQ NACK
203, the base station may configure retransmission data for the
PDSCH 201 with the PDSCH 209 and transmit together with PDCCH.
Referring to FIG. 2, the maximum number of downlink HARQ processes
in TDD UL-DL configuration #6 is six as per the definitions shown
in Table 5 above. That is, there are a total of six downlink HARQ
processes 211, 222, 213, 214, 215, and 216 between the initial
transmission PDSCH 201 and the retransmission PDSCH 209.
[0103] Unlike downlink HARQ, in LTE system, uplink HARQ adopts
synchronous HARQ scheme, which is a scheme where the data
retransmission time is fixed. As used herein, uplink HARQ refers to
an HARQ (initial transmission, ACK/NACK, or retransmission) whose
transmission direction is downlink. The reason why uplink HARQ
adopts synchronous HARQ scheme is that in the LTE TDD system uplink
transmission generally use fewer subframes than downlink
transmission, and thus the terminal cannot freely choose and use
uplink resources. That is, the timing relation in uplink/downlink
timing between the physical channel for uplink data transmission,
PUSCH (physical uplink shared channel), and its precedent downlink
control channel, PDCCH, and the physical channel where HARQ
ACK/NACK corresponding to the PUSCH is transmitted, PHICH (physical
hybrid indicator channel) is fixed by the following rule.
[0104] The terminal, when receiving PDCCH including uplink
scheduling information transmitted from the base station in
subframe n or PHICH where downlink HARQ ACK/NACK is transmitted
from, transmits uplink data corresponding to the control
information through PUSCH in subframe n+k. Here, k is as defined in
Table 6.
TABLE-US-00006 TABLE 6 TDD UL/DL DL subframe number n Configuration
0 1 2 3 4 5 6 7 8 9 0 4 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 4 4 5 4 6 7
7 7 7 5
[0105] If the terminal receives PHICH carrying downlink HARQ
ACK/NACK from the base station in subframe i, the PHICH corresponds
to the PUSCH transmitted from the terminal in subframe i-k. Here, k
is as defined in Table 7.
TABLE-US-00007 TABLE 7 TDD UL/DL DL subframe number i Configuration
0 1 2 3 4 5 6 7 8 9 0 7 4 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6
4 7 4 6
[0106] FIG. 3 is a view illustrating an operation example of
subframes in a TDD frame. FIG. 3 is a view illustrating an example
according to the definitions in Tables 6 and 7, as to the subframe
where uplink PUSCH corresponding to PDCCH or PHICH is transmitted
when the PDCCH or the PHICH is transmitted in each downlink or
special subframe in case of TDD UL-DL configuration #1, and the
subframe where PHICH is transmitted corresponding to the PUSCH.
[0107] For example, the uplink PUSCH corresponding to the PDCCH or
PHICH 301 transmitted from the base station in subframe #1 of radio
frame i is transmitted by the terminal in subframe #7(=1+6) of
radio frame i (303). The base station transmits the PHICH
corresponding to the PUSCH to the terminal in subframe #1 of radio
frame i+1 (305). As another example, the uplink PUSCH corresponding
to the PDCCH or PHICH 307 transmitted from the base station in
subframe #6 of radio frame i is transmitted by the terminal in
subframe #2 of radio frame i+1 (309). The base station transmits
the PHICH corresponding to the PUSCH to the terminal in subframe #6
of radio frame i+1 (311).
[0108] Further, LTE TDD system may pose limitations, regarding
PUSCH transmission, the downlink transmission of PDCCH or PHICH
corresponding to the PUSCH in a particular downlink subframe,
guaranteeing minimum transmission/reception processing time of base
station and terminal. For example, in case of TDD UL-DL
configuration #1 of Tables 6 and 7, PDCCH for scheduling the PUSCH
or PHICH corresponding to the PUSCH is not transmitted in subframe
#0 #5.
[0109] The LTE system operating as above may support
lower-cost/lower-complexity terminals (UEs) by limiting some
functions of the terminal. Such low-cost terminals are anticipated
to be appropriate for machine-type communication (MTC) or
machine-to-machine (M2M services for remote metering, security, or
logistics. Further, low-cost terminals are expected as means to
implement cellular-based Internet of things (cIoT).
[0110] For low costs or low complexity, the number of of receive
antennas of terminal may be limited to one, to reduce costs of RF
components of terminal or TBS processable by the present disclosure
may be set with an upper cap to reduce costs of data receiving
buffer of the terminal. Common LTE terminals are equipped with
broadband signal communication functionality for a minimum of 20
MHz band regardless of the system transmission bandwidth, and by
comparison, low-cost terminals are limited as having 20 MHz or less
maximum bandwidth to leead to additional cost savings and reduced
complexity. For example, in the 20 MHz channel bandwidth LTE
system, low-cost terminals only supportive of 1.4 MHz channel
bandwidth may be defined for their operation. Further, low-cost
terminals may have limited coverage when they are located at a
particular position, e.g., cell boundary, and for enhanced coverage
for low-cost terminals, repetitive transmission is taken into
account. Such repetitive transmission is apparently applicable to
enhanced coverage for normal LTE terminals. Here, there is a need
for defining HARQ communication operation for low-cost terminals
performing repetitive transmission in a coverage enhancing mode
differentiated from normal LTE terminals with no coverage limit,
and a specific method is proposed according to the present
disclosure.
[0111] To achieve the goals set forth above, the following
embodiments are proposed.
[0112] According to an embodiment of the present disclosure,
repetitive transmission of information for uplink data scheduling
to a low-cost terminal in a TDD cell is performed (only) in
downlink subframes having an uplink HARQ process defined, and
uplink data for the repetitive transmission is transmitted based on
the HARQ timing of the HARQ process defined in a downlink subframe
where the repetitive transmission is complete, and HARQ-ACKs for
the uplink data may be repeatedly transmitted based on the HARQ
timing of the HARQ process defined in the uplink subframe where the
repetitive transmission of uplink data is complete.
[0113] According to an embodiment of the present disclosure,
repetitive transmission of downlink signals for uplink data
scheduling to a low-cost terminal in a TDD cell is performed in all
downlink subframes, uplink data is transmitted based on the HARQ
timing of the subframe where the repetitive transmission is
complete or the closest downlink subframe having an uplink HARQ
process defined which comes after the downlink subframe where the
repetitive transmission is complete, and the HARQ-ACKs for the
uplink data may be transmitted based on the HARQ timing of the HARQ
process defined in the uplink subframe where the repetitive
transmission of uplink data is complete.
[0114] According to an embodiment of the present disclosure,
repetitive transmission for uplink data scheduling to a low-cost
terminal in a TDD cell is performed in all downlink subframes,
transmission of uplink data is started in the closest (earliest)
uplink subframe coming p1 subframes from the downlink subframe
where the repetitive transmission is complete, repetitive
transmission of uplink data is performed in all subsequent uplink
subframes, transmission of HARQ-ACKs is started in the closest
downlink subframe coming p2 subframes after the uplink subframe
where the repetitive transmission of the UCI PUSCH data is
complete, and HARQ-ACKs may be repeatedly transmitted in all
subsequent downlink subframes.
[0115] According to an embodiment of the present disclosure,
repetitive transmission for uplink data scheduling to a low-cost
terminal in a TDD cell is transmitted to be complete in the
downlink subframe having an uplink HARQ process defined,
transmission of uplink data is started in the uplink subframe
according to the HARQ timing of the HARQ process defined in the
downlink subframe where the repetitive transmission is complete,
repetitive transmission of uplink data is performed in all
subsequent uplink subframes, transmission of HARQ-ACKs is started
in the downlink subframe according to the HARQ timing of the HARQ
process defined in the uplink subframe where repetitive
transmission of the uplink data is complete, and HARQ-ACKs may be
repeatedly transmitted in all subsequent subframes.
[0116] According to an embodiment of the present disclosure,
repetitive transmission for downlink data scheduling to a low-cost
terminal in a TDD cell is performed in all downlink subframes,
transmission of downlink data is started in the closest downlink
subframe coming k1 subframes after the downlink subframe where the
repetitive transmission is complete, repetitive transmission of
downlink data is performed in all subsequent downlink subframes,
transmission of HARQ-ACKs is started in the closest uplink subframe
coming k2 subframes after the downlink subframe where the
repetitive transmission of the downlink data is complete, and
HARQ-ACKs may be repeatedly transmitted in all subsequent uplink
subframes.
[0117] According to an embodiment of the present disclosure,
repetitive transmission for uplink data scheduling to a low-cost
terminal in a FDD cell is performed in all downlink subframes,
transmission of uplink data is started in the uplink subframe
coming k1 subframes from the downlink subframe where the repetitive
transmission is complete, repetitive transmission of uplink data is
performed in all subsequent uplink subframes, transmission of
HARQ-ACKs is started in the closest downlink subframe coming k2
subframes after the uplink subframe where the repetitive
transmission of the UCI PUSCH data is complete, and HARQ-ACKs may
be repeatedly transmitted in all subsequent downlink subframes.
[0118] According to an embodiment of the present disclosure,
repetitive transmission for downlink data scheduling to a low-cost
terminal in an FDD cell is performed in all downlink subframes,
repetitive transmission of downlink data is started in the downlink
subframe coming ml subframes after the downlink subframe where the
repetitive transmission is complete, repetitive transmission of the
downlink data is performed in all subsequent downlink subframes,
transmission of HARQ-ACKs is started in the uplink subframe coming
k2 subframes after the downlink subframe where the repetitive
transmission of downlink data is complete, and HARQ-ACKs may be
repeatedly transmitted in all subsequent uplink subframes.
[0119] FIG. 4 is a view illustrating a problematic situation to be
solved according to the present disclosure.
[0120] FIG. 4 exemplifies a static TDD-based LTE cell 401.
[0121] It is assumed that the terminal (e.g., a low-cost terminal)
is always set in coverage enhancing mode, and in case it is set in
the coverage enhancing mode, it may communicate data through
reception transmission/reception. Downlink subframes and uplink
subframes are configured in the cell 401 according to TDD UL-DL
configuration #4. The terminal may obtain TDD UL-DL configuration
for the cell from system information or higher layer information.
The coverage enhancing mode of the terminal may be set by a higher
layer signaling from the base station, and the terminal always
operating in the coverage enhancing mode may signal to the base
station that it is always operating in the coverage enhancing
mode.
[0122] A TDD-based downlink subframe and uplink subframe configure
one HARQ process. That is, the subframes having such pattern as
shown in FIG. 4 are subframes configuring one HARQ process. For
example, uplink subframe #2 421 and downlink subframe #8 423
configure one uplink HARQ process, and uplink subframe #3 422 and
downlink subframe #9 424 configure one uplink HARQ process.
[0123] Further, the terminal receiving uplink scheduling
information in downlink subframe #8 423 of radio frame i transmits
uplink data in uplink subframe #2 425 of next radio frame (radio
frame i+1) based on the uplink HARQ timing according to the uplink
HARQ process configuration. Further, the terminal receiving uplink
scheduling information in downlink subframe #9 424 of radio frame i
transmits uplink data in uplink subframe #3 426 of next radio frame
(radio frame i+1) based on the uplink HARQ timing according to the
uplink HARQ process configuration.
[0124] However, in FIG. 4, downlink subframes #0, #1, #4, #5, #6,
and #7 of radio frame i do not configure uplink HARQ process, and
it may be seen that downlink subframes #0, #1, #4, #5, #6, and #7
have no uplink HARQ timing defined based on uplink HARQ
process.
[0125] A channel reception method between base station and terminal
for repetitive transmission/reception may be defined depending on
channel types as follows.
TABLE-US-00008 TABLE 8 Channel and signal Receiving method (e)PDCCH
Chase Combining (e)PHICH Chase Combining PUSCH Incremental
Redundancy PDSCH Incremental Redundancy PUCCH Chase Combining PRACH
Chase Combining PBCH Chase Combining PSS/SSS Chase Combining SRS
Chase Combining CRS/CSI-RS/PRS Chase Combining
[0126] Configuration information related to repetitive transmission
of the terminal, i.e., repetitive transmission start subframe,
repetitive transmission count, or frequency resource information
where repetitive transmission channel is transmitted, may be
previously transmitted to the terminal. In FIG. 4, it is assumed
that a total of four times of repetitive transmission is set. The
base station transmits uplink data scheduling information 411, 412,
413, and 414 to the terminal in subframe #4, subframe #5, subframe
#6, and subframe #7. At this time, downlink subframe #7 has not
uplink HARQ process defined. Accordingly, the terminal faces the
situation where it cannot be aware of the uplink subframe which
uplink data 415 (e.g., PUSCH) for the scheduling information 411,
412, 413, and 414 repeatedly transmitted should be transmitted
through.
[0127] FIG. 5 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0128] FIG. 5 exemplifies a static TDD-based LTE cell 501. In the
exemplified scheme, the base station performs repetitive
transmission on the uplink data scheduling information (only) in
downlink subframes having LTE cell uplink HARQ process defined so
that the terminal performs uplink HARQ transmission according to
the defined uplink HARQ process timing.
[0129] It is assumed that the terminal (e.g., a low-cost terminal)
is always set in coverage enhancing mode, and in case it is set in
the coverage enhancing mode, it may communicate data through
reception transmission/reception. Downlink subframes and uplink
subframes are configured in the cell 501 according to TDD UL-DL
configuration #1. The terminal may obtain TDD UL-DL configuration
for the cell 501 from system information (e.g., system information
block (SIB) information) or higher layer information (i.e., higher
layer signaling). The coverage enhancing mode of the terminal may
be set by a higher layer signaling from the base station, and the
terminal always operating in the coverage enhancing mode may signal
to the base station that it is always operating in the coverage
enhancing mode. Or, the terminal may set itself to operate in the
coverage enhancing mode through reception of system information or
a random access procedure or the terminal may be set to operate in
the coverage enhancing mode by the base station.
[0130] A TDD-based downlink subframe and uplink subframe may
configure one uplink HARQ process. The subframes having such
pattern as shown in FIG. 5 configure one HARQ process. However,
since the number of uplink subframes is not always the same as the
number of downlink subframes, all of the subframes included in one
radio frame do not configure HARQ process. For example, in FIG. 5,
downlink subframes #0 and #5 do not configure uplink HARQ process,
and it may be seen that no uplink HARQ timing is defined for
downlink subframes #0 and #5. Accordingly, the HARQ transmission
scheme shown in FIG. 5 may advantageously apply to the situations
where the number of downlink subframes configuring no uplink HARQ
process in the radio frame is smaller as compared with other UL-DL
configurations (i.e., among the UL-DL configurations, ones having
relatively more downlink subframes configuring HARQ processes). For
a reason, many of the subframes configuring a radio frame configure
uplink HARQ process, and thus, even when repetitive transmission is
performed only with the subframes configuring the uplink HARQ
process, not much time is consumed for transmission, and there is
no need of specifying an additional rule for HARQ process, thus
leading to minimized influence on the standards.
[0131] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal. In FIG. 5, it is assumed that a
total of four times of repetitive transmission is set. Although
FIG. 5 illustrates an example in which the uplink scheduling
information, uplink data, and HARQ-ACK are set to have the same
number of times of repetition, such pieces of information may be
set to be different from each other by a higher layer signal or may
be adjusted to be different dynamically by an L1 signal.
[0132] The base station transmits uplink data scheduling
information to the terminal through repetitive transmission in
subframe #1, subframe #4, subframe #6, and subframe #9 of radio
frame k 502 (511, 512, 513, and 514). Subframe #1, subframe #4,
subframe #6, and subframe #9 are subframes having uplink HARQ
process defined therein, and the base station does not perform
repetitive transmission in subframe #0 and subframe #5 having no
uplink HARQ process defined.
[0133] After repetitive transmission of uplink scheduling
information as many times as the repetition count as set, the
terminal may perform repetitive transmission for uplink data
transmission based on the uplink HARQ timing defined in subframe #9
of radio frame k 502 that is the last subframe of repetitive
transmission. The subframe forming HARQ process with subframe #9 of
radio frame k 502 is subframe #3. Accordingly, the terminal may
perform repetitive transmission on uplink data from subframe #3 of
radio frame k+1 503 by following the uplink HARQ process defined in
subframe #9 (521). Subsequently, the terminal performs repetitive
transmission on uplink data in subframe #2 of radio frame k+2 504
and subframes #7 and #8 of radio frame k+1 503 as many times as the
remaining repetition count (522, 523, and 524). Here, it may be
seen that the uplink subframes where uplink data transmission is
performed have uplink HARQ process defined therein (the subframes
having a pattern as shown in FIG. 5).
[0134] Next, repetitive transmission of HARQ-ACKs (through EPDCCH
or ePHICH) may be performed from subframe #6 of radio frame k+2 504
according to the uplink HARQ timing based on the uplink HARQ
process defined in subframe #2 of radio frame k+2 504 (531). The
HARQ-ACK through ePDCCH or ePHICH is an HARQ signal transmitted
from the base station for the PUSCHs 521, 522, 523, and 524
transmitted on uplink from the terminal. Subsequently, the base
station may perform repetitive transmission of HARQ-ACKs in
subframe #9 of radio frame k+2 504, subframe #1 of radio frame k+3
505, and subframe #4 of radio frame k+3 505 as many times as the
remaining repetition count (532, 533, and 534). Additionally, if
there is uplink data retransmission, the terminal may perform
uplink data repetitive transmission based on the uplink HARQ timing
defined in subframe #4 of radio frame k+2 504.
[0135] As exemplified in FIG. 5, determining the uplink
transmission start subframe based on the subframes where uplink
data scheduling information is transmitted (i.e., determining
ePDCCH-to-PUSCH HARQ timing) and determining HARQ-ACK transmission
start subframe based on the subframes where uplink data is
transmitted (i.e., determining PUSCH-to-HARQ-ACK timing) may apply
to both the base station and the terminal, or any one of the
ePDCCH-to-PUSCH HARQ timing determination and the PUSCH-to-HARQ-ACK
timing determination may apply thereto. For example, since the
subframes for downlink HARQ-ACK transmission are not insufficient
in the radio frame (unlike the subframes for uplink data
transmission), a subframe for HARQ-ACK transmission may be
dynamically determined by the base station, and in such case, the
PUSCH-to-HARQ-ACK timing determination scheme might not apply.
[0136] FIG. 6a is a flowchart illustrating an operation by a base
station for a control channel transmission method according to an
embodiment of the present disclosure.
[0137] FIG. 6a exemplifies a method for performing repetitive
transmission on an uplink HARQ process by a base station as shwon
in FIG. 5.
[0138] In step 601, the base station transmits information on LTE
cell to the terminal, configures repetitive transmission-related
information, and transmits the same to the terminal.
[0139] The information on LTE cell may be UL-DL configuration
information or special subframe configuration information. The
information on LTE cell may be transmitted to the terminal through
system information (e.g., SIB information) or higher layer
information (i.e., higher layer signaling). The repetitive
transmission-related information, e.g., repetitive transmission
start subframe, repetitive transmission count, information on
frequency resources for transmitting repetitive transmission
channel, or information on groups of (downlink or uplink) subframes
where repetitive transmission may be conducted, may be transmitted
to the terminal via system information, higher layer information,
or L1 signal. Here, it is assumed that the terminal (e.g., a
low-cost terminal) is always set in coverage enhancing mode, and in
case it is set in the coverage enhancing mode, it may communicate
data through reception transmission/reception. The coverage
enhancing mode of the terminal may be set by a higher layer
signaling from the base station, and the terminal always operating
in the coverage enhancing mode may signal to the base station that
it is always operating in the coverage enhancing mode. Or, the
terminal may set itself to operate in the coverage enhancing mode
through reception of system information or a random access
procedure or the terminal may be set to operate in the coverage
enhancing mode by the base station.
[0140] In step 602, the base station repeatedly transmits the
uplink scheduling information (only) in downlink subframes having
uplink HARQ process defined based on the configured repetitive
transmission-related information.
[0141] In step 603, the base station repeatedly receives uplink
data based on the configured repetitive transmission-related
information in the uplink subframe according to the uplink HARQ
timing based on the uplink HARQ process of the downlink subframe
where the repetitive transmission of uplink scheduling information
is complete. Taking an example as shown in FIG. 5, when the base
station completes the repetitive transmission of uplink scheduling
information in subframe #9 of radio frame k 502, the subframe
according to the uplink HARQ timing based on the uplink HARQ
process of subframe #9 is subframe #3. Accordingly, the base
station may start repetitive reception from subframe #3 of radio
frame k+1 503.
[0142] In step 604, the base station repeatedly transmits HARQ-ACKs
(through ePDCCH or ePHICH) based on the configured repetitive
transmission-related information in the downlink subframe according
to the uplink HARQ timing based on the uplink HARQ process of the
uplink subframe where the repetitive reception of uplink data is
complete. Taking an example as shown in FIG. 5, when the base
station completes the repetitive reception of uplink data in
subframe #2 of radio frame k+2 504, the downlink subframe according
to the uplink HARQ timing based on the uplink HARQ process of
subframe #2 is subframe #6. Accordingly, the base station may start
repetitive transmission of HARQ-ACKs from subframe #6 of radio
frame k+2 504.
[0143] FIG. 6b is a flowchart illustrating an operation by a
terminal for a control channel transmission method according to an
embodiment of the present disclosure.
[0144] FIG. 6b exemplifies a method for performing repetitive
transmission on an uplink HARQ process by a terminal as shwon in
FIG. 5.
[0145] In step 611, the terminal receives information on LTE cell
from the base station and receives repetitive transmission-related
information configured by the base station.
[0146] The information on LTE cell may be UL-DL configuration
information or special subframe configuration information. The
information on LTE cell may be received from the base station
through system information (e.g., SIB information) or higher layer
information (i.e., higher layer signaling). The repetitive
transmission-related configuration information, e.g., repetitive
transmission start subframe, repetitive transmission count,
information on frequency resources for transmitting repetitive
transmission channel, or information on groups of downlink or
uplink subframes where repetitive transmission may be conducted,
may be received from the base station via system information,
higher layer information, or L1 signal. The repetitive
transmission-related information, e.g., repetitive transmission
start subframe, repetitive transmission count, information on
frequency resources for transmitting repetitive transmission
channel, or information on groups of (downlink or uplink) subframes
where repetitive transmission may be conducted, may be transmitted
to the terminal via system information, higher layer information,
or L1 signal. Here, it is assumed that the terminal (e.g., a
low-cost terminal) is always set in coverage enhancing mode, and in
case it is set in the coverage enhancing mode, it may communicate
data through reception transmission/reception. The coverage
enhancing mode of the terminal may be set by a higher layer
signaling from the base station, and the terminal always operating
in the coverage enhancing mode may signal to the base station that
it is always operating in the coverage enhancing mode. Or, the
terminal may set itself to operate in the coverage enhancing mode
through reception of system information or a random access
procedure or the terminal may be set to operate in the coverage
enhancing mode by the base station.
[0147] In step 612, the terminal repeatedly receives uplink
scheduling information based on the received repetitive
transmission-related information in (only) downlink subframes
having the uplink HARQ process defined.
[0148] In step 613, the terminal repeatedly transmits uplink data
based on the received repetitive transmission-related information
in the uplink subframe according to the uplink HARQ timing based on
the uplink HARQ process of the downlink subframe where the
repetitive reception of uplink scheduling information is complete.
Taking an example as shown in FIG. 5, when the terminal completes
the repetitive reception of uplink scheduling information in
subframe #9 of radio frame k 502, the subframe according to the
uplink HARQ timing based on the uplink HARQ process of subframe #9
is subframe #3. Accordingly, the terminal may start repetitive
transmission of uplink data from subframe #3 of radio frame k+1
503.
[0149] In step 614, the terminal repeatedly receives HARQ-ACKs
(through ePDCCH or ePHICH) based on the received repetitive
transmission-related information in the downlink subframe according
to the uplink HARQ timing based on the uplink HARQ process of the
uplink subframe where the repetitive transmission of uplink data is
complete. Taking an example as shown in FIG. 5, when the terminal
completes the repetitive transmission of uplink data in subframe #2
of radio frame k+2 504, the downlink subframe according to the
uplink HARQ timing based on the uplink HARQ process of subframe #2
is subframe #6. Accordingly, the terminal may start repetitive
reception of HARQ-ACKs from subframe #6 of radio frame k+2 504.
[0150] FIG. 7 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0151] FIG. 7 exemplifies a static TDD-based LTE cell 701. The base
station may perform repetitive transmission of uplink data
scheduling information in all the downlink subframes regardless of
the uplink HARQ process defined in the LTE cell. Accordingly,
according to this embodiment, there is exemplified a scheme in
which a new uplink HARQ timing is defined, and the base station and
the terminal performs uplink HARQ communication according to the
new uplink HARQ timing.
[0152] It is assumed that the terminal (e.g., a low-cost terminal)
is always set in coverage enhancing mode, and in case it is set in
the coverage enhancing mode, it may communicate data through
reception transmission/reception. Downlink subframes and uplink
subframes are configured in the cell 701 according to TDD UL-DL
configuration #2. The terminal may obtain TDD UL-DL configuration
for the cell 501 from system information (e.g., SIB information) or
higher layer information (i.e., higher layer signaling). The
coverage enhancing mode of the terminal may be set by a higher
layer signaling from the base station, and the terminal always
operating in the coverage enhancing mode may signal to the base
station that it is always operating in the coverage enhancing mode.
Or, the terminal may set itself to operate in the coverage
enhancing mode through reception of system information or a random
access procedure or the terminal may be set to operate in the
coverage enhancing mode by the base station.
[0153] A TDD-based downlink subframe and uplink subframe may
configure one uplink HARQ process. The subframes having such
pattern as shown in FIG. 7 configure one HARQ process. In FIG. 7,
downlink subframes #0, #1, #4, #5, #6, and #9 of radio frame i do
not configure uplink HARQ process, and it may be seen that
subframes #0, #1, #4, #5, #6, and #9 have no uplink HARQ timing
defined based on uplink HARQ process. Accordingly, the HARQ
transmission scheme shown in FIG. 7 may advantageously apply to the
situations where the number of downlink subframes configuring no
uplink HARQ process in the radio frame is larger as compared with
other UL-DL configurations (i.e., among the UL-DL configurations,
ones having relatively fewer downlink subframes configuring HARQ
processes). For a reason, many of the subframes configuring a radio
frame do not configure uplink HARQ process, and thus, it would take
long to perform repetitive transmission only with the subframes
configuring uplink HARQ process. Accordingly, it is advantageous in
minimizing transmission time to perform repetitive transmission in
all the downlink subframes regardless of whether HARQ process is
configured in the example shown in FIG. 7, and there is a need of
introducing a new uplink HARQ timing. Although the introduction of
such new uplink HARQ timing might influence the standards, it would
be advantageous in leading to minimized transmission time to
perform repetitive transmission in all the downlink subframes in
the example shown in FIG. 7.
[0154] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal.
[0155] A group of uplink or downlink subframes may be a group of
downlink subframes for transmission of, e.g., uplink or downlink
scheduling. If the repetitive transmission-related information is
transmitted to the terminal and configured, the terminal may
attempt to detect PDCCH (or ePDCCH) for uplink or downlink
scheduling only in at least one downlink subframe in the group of
downlink subframes. Further, the terminal may also try to detect
PDCCH (or ePDCCH) for uplink or downlink scheduling only in at
least one downlink subframe within the group of downlink subframes
also for the PDCCH (or ePDCCH) for scheduling retransmission data
after repetitive transmission of uplink data by the uplink
scheduling or repetitive transmission of downlink data by downlink
scheduling.
[0156] In FIG. 7, it is assumed that a total of four times of
repetitive transmission is set. Although the instant embodiment
illustrates an example in which the uplink scheduling information,
uplink data, and HARQ-ACK are set to have the same number of times
of repetition, such pieces of information may be set to be
different from each other by a higher layer signal or may be
adjusted to be different dynamically by an L1 signal.
[0157] The base station transmits uplink data scheduling
information to the terminal through repetitive transmission in
subframe #1, subframe #3, subframe #4, and subframe #5 of radio
frame k 702 (711, 712, 713, and 714). Although FIG. 7 illustrates
an example in which uplink scheduling information is transmitted in
consecutive downlink subframes, repetitive transmission of uplink
scheduling information may also be performed only in the downlink
subframes configured by the higher signal in the group of downlink
subframes where repetitive transmission may be performed.
[0158] Since the repetitive transmission of scheduling information
has been complete in downlink subframe #5 of radio frame k 702
which has no uplink HARQ process defined, there is a need of
defining a new uplink HARQ transmission timing in downlink subframe
#5. In the instant embodiment, the base station or the terminal may
determine uplink HARQ transmission timing under the assumption that
the repetitive transmission has been complete in subframe #5 or the
closest (or earliest coming) downlink subframe coming after
subframe #5 and having an uplink HARQ process defined and may
perform uplink data transmission based on the determined HARQ
transmission timing (715).
[0159] Referring to FIG. 7, the repetitive transmission of
scheduling information (ePDCCH) is complete in the downlink
subframe having no uplink HARQ process defined, like subframe #5.
The terminal starts the repetitive transmission of uplink data in
subframe #2 of radio frame k+1 703 according to the HARQ
transmission timing of subframe #8 under the assumption that the
repetitive transmission has been complete in the closest subframe
(i.e., subframe #8 of radio frame k 702) of the downlink subframes
having uplink HARQ process defined and coming after subframe #5
(721). However, if the repetitive transmission of the scheduling
information is complete in the subframe (e.g., subframe #3 or
subframe #8) having an uplink HARQ process defined, the terminal
may be able to perform uplink data transmission based on the HARQ
transmission timing in the subframe where it has been complete.
Subsequently, the terminal performs uplink data transmission in
subframe #7 of radio frame k+1 703, subframe #2 of radio frame k+2
704, and subframe #7 of radio frame k+2 704 to perform repetitive
transmission as many as the repetition count as set (i.e., four
times) (722, 723, and 724). Here, the uplink subframes where uplink
data transmission is performed are always subframes having uplink
HARQ process defined therein.
[0160] Next, repetitive transmission of HARQ-ACKs (through EPDCCH
or ePHICH) is started from the subframe according to the uplink
HARQ timing based on the uplink HARQ process defined in subframe #7
of radio frame k+2 704 (i.e., subframe #3 of radio frame k+3 705)
(731). That is, the base station performs HARQ-ACK repetitive
transmission from subframe #3 of radio frame k+3 705 (731). The
base station performs HARQ-ACK transmission in subframe #4,
subframe #5, and subframe #6 of radio frame k+3 705 (732, 733, and
734). Alternatively, repetitive transmission of HARQ-ACKs (through
ePDCCH or ePHICH) may be performed from the closest subframe in the
group of downlink subframes where repetitive transmission may be
performed, as configured by a higher signal, among the subframes
coming after subframe #3 as per the uplink HARQ timing based on the
uplink HARQ process, and the terminal may perform detection on the
HARQ-ACKs only in some subframes of the subframe group.
[0161] If there is additional uplink data retransmission, the
terminal may perform uplink data retransmission. Since no HARQ
process is defined in subframe #6 of radio frame k+3 705, the
terminal should determine the HARQ timing for retransmission. Here,
the terminal may perform uplink data retransmission based on the
uplink HARQ timing according to the uplink HARQ process of the
closest downlink subframe under the assumption that the repetitive
transmission of HARQ-ACKs 734 has been complete in the closest
downlink subframe (i.e., subframe #8 of radio frame k+3 705) having
an uplink HARQ process defined and coming after subframe #6 of
radio frame k+3 705. That is, the terminal may repeatedly perform
uplink data retransmission based on the uplink HARQ timing of
subframe #8 (i.e., in subframe #2 of the next radio frame) under
the assumption that HARQ-ACK (ePDCCH or ePHICH) transmission has
been complete in subframe #8.
[0162] As exemplified in FIG. 7, determining the uplink
transmission start subframe based on the subframes where uplink
data scheduling information is transmitted (determining
ePDCCH-to-PUSCH HARQ timing) and determining HARQ-ACK transmission
start subframe based on the subframes where uplink data is
transmitted (i.e., determining PUSCH-to-HARQ-ACK timing) may apply
to both the base station and the terminal, or any one of the
ePDCCH-to-PUSCH HARQ timing determination and the PUSCH-to-HARQ-ACK
timing determination may apply thereto. For example, since the
subframes for downlink HARQ-ACK transmission are not insufficient
in the radio frame (unlike the subframes for uplink data
transmission), a subframe for HARQ-ACK transmission may be
dynamically determined by the base station, and in such case, the
PUSCH-to-HARQ-ACK timing determination scheme might not apply.
[0163] FIG. 8a is a view illustrating a method for transmitting a
control channel by a base station according to an embodiment of the
present disclosure.
[0164] FIG. 8a exemplifies operations by the base station to
perform repetitive transmission on uplink HARQ process shown in
FIG. 7.
[0165] In step 801, the base station transmits information on LTE
cell to the terminal, configures repetitive transmission-related
information, and transmits the same to the terminal.
[0166] The information on LTE cell may be UL-DL configuration
information and special subframe configuration information. The
information on LTE cell may be transmitted to the terminal through
system information (e.g., SIB information) or higher layer
information (i.e., higher layer signaling). The repetitive
transmission-related information, e.g., repetitive transmission
start subframe, repetitive transmission count, information on
frequency resources for transmitting repetitive transmission
channel, or information on groups of (downlink or uplink) subframes
where repetitive transmission may be conducted, may be transmitted
to the terminal via system information, higher layer information,
or L1 signal. Here, it is assumed that the terminal (e.g., a
low-cost terminal) is always set in coverage enhancing mode, and in
case it is set in the coverage enhancing mode, it may communicate
data through reception transmission/reception. The coverage
enhancing mode of the terminal may be set by a higher layer
signaling from the base station, and the terminal always operating
in the coverage enhancing mode may signal to the base station that
it is always operating in the coverage enhancing mode. Or, the
terminal may set itself to operate in the coverage enhancing mode
through reception of system information or a random access
procedure or the terminal may be set to operate in the coverage
enhancing mode by the base station.
[0167] In step 802, the base station repeatedly transmits uplink
scheduling information based on the configured repetitive
transmission-related information in all the downlink subframes or
downlink subframes in a group of downlink subframes where the
configured repetitive transmission may be performed by a higher
layer signal.
[0168] In step 803, the base station determines whether uplink HARQ
process is defined in the downlink subframe where repetitive
transmission of uplink scheduling information is complete. If the
uplink HARQ process is defined, the base station repeatedly
receives uplink data based on the configured repetitive
transmission-related information from the uplink subframe according
to the uplink HARQ timing based on the uplink HARQ process in step
804. In step 805, the base station repeatedly transmits HARQ-ACKs
(through ePDCCH or ePHICH) based on the configured repetitive
transmission-related information in the downlink subframe according
to the uplink HARQ timing based on the uplink HARQ process of the
uplink subframe where the repetitive reception of uplink data is
complete. Alternatively, in step 805, the base station may
repeatedly transmit HARQ-ACKs (through ePDCCH or ePHICH) based on
the configured repetitive transmission-related information from the
closest subframe in the group of downlink subframes where the
configured repetitive transmission may be performed by a higher
layer signal among the subframes coming after the downlink subframe
according to the uplink HARQ timing based on the uplink HARQ
process.
[0169] If the uplink HARQ process is not defined, the base station
repeatedly receives uplink data based on the configured repetitive
transmission-related information in the uplink subframe according
to the uplink HARQ timing based on the uplink HARQ process of the
closest downlink subframe having an uplink HARQ process defined and
coming after the downlink subframe where the repetitive
transmission of uplink scheduling information is complete, in step
806. In step 807, the base station repeatedly transmits HARQ-ACKs
(through ePDCCH or ePHICH) based on the configured repetitive
transmission-related information in the downlink subframe according
to the uplink HARQ timing based on the uplink HARQ process of the
uplink subframe where the repetitive reception of uplink data is
complete. Alternatively, in step 807, the base station may
repeatedly transmit HARQ-ACKs (through ePDCCH or ePHICH) as
specified in the configured repetitive transmission-related
information from the closest subframe in the group of downlink
subframes where the configured repetitive transmission may be
performed by a higher layer signal among the subframes coming after
the downlink subframe according to the uplink HARQ timing based on
the uplink HARQ process.
[0170] FIG. 8b is a view illustrating a method for transmitting a
control channel by a terminal according to an embodiment of the
present disclosure.
[0171] FIG. 8b exemplifies operations by the terminal to perform
repetitive transmission on uplink HARQ process shown in FIG. 7.
[0172] In step 811, the terminal receives information on LTE cell
from the base station and receives repetitive transmission-related
configuration information configured by the base station.
[0173] The information on LTE cell may be UL-DL configuration
information and special subframe configuration information. The
information on LTE cell may be received from the base station
through system information (e.g., SIB information) or higher layer
information (i.e., higher layer signaling). The repetitive
transmission-related information, e.g., repetitive transmission
start subframe, repetitive transmission count, information on
frequency resources for transmitting repetitive transmission
channel, or information on groups of (downlink or uplink) subframes
where repetitive transmission may be conducted, may be transmitted
to the terminal via system information, higher layer information,
or L1 signal. Here, it is assumed that the terminal (e.g., a
low-cost terminal) is always set in coverage enhancing mode, and in
case it is set in the coverage enhancing mode, it may communicate
data through reception transmission/reception. The coverage
enhancing mode of the terminal may be set by a higher layer
signaling from the base station, and the terminal always operating
in the coverage enhancing mode may signal to the base station that
it is always operating in the coverage enhancing mode. Or, the
terminal may set itself to operate in the coverage enhancing mode
through reception of system information or a random access
procedure or the terminal may be set to operate in the coverage
enhancing mode by the base station.
[0174] In step 812, the terminal repeatedly receives uplink
scheduling information based on the received repetitive
transmission-related information in all the downlink subframes or
downlink subframes in a group of downlink subframes where the
configured repetitive transmission may be performed by a higher
layer signal.
[0175] In step 813, the terminal determines whether uplink HARQ
process is defined in the downlink subframe where repetitive
transmission of uplink scheduling information is complete. If the
uplink HARQ process is defined, the terminal repeatedly transmits
uplink data based on the received repetitive transmission-related
information from the uplink subframe according to the uplink HARQ
timing based on the uplink HARQ process in step 814. In step 815,
the terminal repeatedly receives HARQ-ACKs (through ePDCCH or
ePHICH) as specified in the received repetitive
transmission-related information in the downlink subframe according
to the uplink HARQ timing based on the uplink HARQ process of the
uplink subframe where the repetitive transmission of uplink data is
complete. Alternatively, in step 815, the terminal may repeatedly
receive HARQ-ACKs (through ePDCCH or ePHICH) as specified in the
received repetitive transmission-related information from the
closest subframe in the group of downlink subframes where the
configured repetitive transmission may be performed by a higher
layer signal among the subframes coming after the downlink subframe
according to the uplink HARQ timing based on the uplink HARQ
process.
[0176] If the uplink HARQ process is not defined, the terminal
repeatedly transmits uplink data as specified in the received
repetitive transmission-related information in the uplink subframe
according to the uplink HARQ timing based on the uplink HARQ
process of the closest downlink subframe having an uplink HARQ
process defined and coming after the downlink subframe where the
repetitive transmission of uplink scheduling information is
complete, in step 816. In step 817, the terminal repeatedly
receives HARQ-ACKs (through ePDCCH or ePHICH) as specified in the
received repetitive transmission-related information in the
downlink subframe according to the uplink HARQ timing based on the
uplink HARQ process of the uplink subframe where the repetitive
transmission of uplink data is complete. Alternatively, in step
817, the terminal may repeatedly receive HARQ-ACKs (through ePDCCH
or ePHICH) as specified in the received repetitive
transmission-related information from the closest subframe in the
group of downlink subframes where the configured repetitive
transmission may be performed by a higher layer signal among the
subframes coming after the downlink subframe according to the
uplink HARQ timing based on the uplink HARQ process.
[0177] FIG. 9 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0178] FIG. 9 exemplifies a static TDD-based LTE cell 901. The base
station may perform repetitive transmission of uplink data
scheduling information in all the downlink subframes regardless of
the uplink HARQ process defined in the LTE cell. Accordingly,
according to this embodiment, there is exemplified a scheme in
which a new uplink HARQ timing is defined, and the base station and
the terminal performs uplink HARQ communication according to the
new uplink HARQ timing.
[0179] It is assumed that the terminal (e.g., a low-cost terminal)
is always set in coverage enhancing mode, and in case it is set in
the coverage enhancing mode, it may communicate data through
reception transmission/reception. Downlink subframes and uplink
subframes are configured in the cell 901 according to TDD UL-DL
configuration #2. The terminal may obtain TDD UL-DL configuration
for the cell from system information (e.g., SIB information) or
higher layer information (i.e., higher layer signaling). The
coverage enhancing mode of the terminal may be set by a higher
layer signaling from the base station, and the terminal always
operating in the coverage enhancing mode may signal to the base
station that it is always operating in the coverage enhancing mode.
Or, the terminal may set itself to operate in the coverage
enhancing mode through reception of system information or a random
access procedure or the terminal may be set to operate in the
coverage enhancing mode by the base station.
[0180] A TDD-based downlink subframe and uplink subframe may
configure one uplink HARQ process. The subframes having such
pattern as shown in FIG. 9 configure one HARQ process. In FIG. 9,
downlink subframes #0, #1, #4, #5, #6, and #9 of radio frame i do
not configure uplink HARQ process, and it may be seen that
subframes #0, #1, #4, #5, #6, and #9 have no uplink HARQ timing
defined based on uplink HARQ process. Accordingly, the HARQ
transmission scheme shown in FIG. 9 may advantageously apply to the
situations where the number of downlink subframes configuring no
uplink HARQ process in the radio frame is larger as compared with
other UL-DL configurations (i.e., among the UL-DL configurations,
ones having relatively fewer downlink subframes configuring HARQ
processes). For a reason, many of the subframes configuring a radio
frame do not configure uplink HARQ process, and thus, it would take
long to perform repetitive transmission only with the subframes
configuring uplink HARQ process. Accordingly, it is advantageous in
minimizing transmission time to perform repetitive transmission in
all the downlink subframes regardless of whether HARQ process is
configured in the example shown in FIG. 9, and there is a need of
introducing a new uplink HARQ timing. Although the introduction of
such new uplink HARQ timing might influence the standards, it would
be advantageous in leading to minimized transmission time to
perform repetitive transmission in all the downlink subframes in
the example shown in FIG. 9.
[0181] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal.
[0182] A group of uplink or downlink subframes may be a group of
downlink subframes for transmission of, e.g., uplink or downlink
scheduling. If the repetitive transmission-related information is
transmitted to the terminal and configured, the terminal may
attempt to detect PDCCH (or ePDCCH) for uplink or downlink
scheduling only in at least one downlink subframe in the group of
downlink subframes. Further, the terminal may also try to detect
PDCCH (or ePDCCH) for uplink or downlink scheduling only in at
least one downlink subframe within the group of downlink subframes
also for the PDCCH (or ePDCCH) for scheduling retransmission data
after repetitive transmission of uplink data by the uplink
scheduling or repetitive transmission of downlink data by downlink
scheduling.
[0183] In FIG. 9, it is assumed that a total of four times of
repetitive transmission is set. Although the instant embodiment
illustrates an example in which the uplink scheduling information,
uplink data, and HARQ-ACK are set to have the same number of times
of repetition, such pieces of information may be set to be
different from each other. by a higher layer signal or may be
adjusted to be different dynamically by an L1 signal.
[0184] The base station transmits uplink data scheduling
information to the terminal through repetitive transmission in
subframe #1, subframe #3, subframe #4, and subframe #5 of radio
frame k 902 (911, 912, 913, and 914). Although FIG. 9 illustrates
an example in which uplink scheduling information is transmitted in
consecutive downlink subframes, repetitive transmission of uplink
scheduling information may also be performed only in the downlink
subframes configured by the higher signal in the group of downlink
subframes where repetitive transmission may be performed.
[0185] In FIG. 9, repetitive transmission of uplink scheduling
information has been complete in subframe #5, and the terminal may
perform repetitive transmission of uplink data from the closest
uplink subframe (i.e., subframe coming earliest) among uplink
subframes coming after a predetermined number (i.e., p1) of
subframes. p1 may be set as one of multiple values by a higher
layer signal (higher layer signaling) or may be fixed to a
particular value by a standard (an agreement previously defined).
For example, p1 may be fixed to 4. Here, repetitive transmission of
uplink data by the terminal may be initiated from the closest
uplink subframe coming p1 subframes after subframe #5 of radio
frame k 902, i.e., subframe #2 of radio frame k+1 903 (921).
[0186] That is, in the embodiment shown in FIG. 9, the terminal
performs uplink data transmission in the closest uplink subframe
coming after p1 subframes after the downlink subframe where the
repetitive transmission is complete, regardless of whether the
uplink HARQ process is defined in the subframe where repetitive
transmission is complete. Although repetitive transmission of
uplink data scheduling is complete in subframes having uplink HARQ
process defined like subframe #3 or subframe #8, the terminal may
perform uplink data transmission in the uplink subframe first
coming p1 subframes after the subframe where it is complete
regardless of the defined HARQ process.
[0187] After the repetitive transmission 921 of uplink data is
started by the terminal in subframe #2 of radio frame k+1 903, the
terminal performs uplink data repetitive transmission as many times
as the repetition count as set. That is, the terminal performs
uplink data repetitive transmission in subframe #7 of radio frame
k+1 903 and subframe #2 and subframe #7 of radio frame k+2 904
(922, 923, and 924).
[0188] Next, repetitive transmission of HARQ-ACKs (through ePDCCH
or ePHICH) is performed from subframe #1 of radio frame k+3 905,
which is the closest downlink subframe coming a predetermined
number (i.e., p2) subframes after subframe #7 of radio frame k+2
904.
[0189] Alternatively, repetitive transmission of HARQ-ACKs (ePDCCH
or ePHICH) may also be performed from the closest subframe in the
group of downlink subframes where the configured repetitive
transmission may be performed by a higher layer signal among the
subframes coming p2 subframes after subframe #7. Here, the terminal
may detect HARQ-ACK (ePDCCH or ePHICH) in the subframes within the
group of downlink subframes. p2 may be set as one of multiple
values by a higher layer signal (higher layer signaling) or may be
fixed to a particular value by a standard (an agreement previously
defined). For example, p2 may be fixed to 4. Here, repetitive
transmission of HARQ-ACKs (ePDCCH or ePHICH) by the terminal may be
initiated from the closest downlink subframe coming p2 subframes
after subframe #5 of radio frame k+2 904, i.e., subframe #1 of
radio frame k+3 905 (931).
[0190] After the repetitive transmission (931) of HARQ-ACKs (ePDCCH
or ePHICH) is initiated by the base station in subframe #1 of radio
frame k+3 905, the base station performs repetitive transmission of
HARQ-ACKs (ePDCCH or ePHICH) in subframe #3, subframe #4, and
subframe #5 of radio frame k+3 905 as many times as the repetition
count as set (932, 933, and 934).
[0191] Additionally, if there is retransmission of uplink data, the
repetitive transmission of uplink data may be performed in the
closest uplink subframe coming p1 subframes after subframe #5 of
radio frame k+3 905. As described in connection with FIG. 9,
determining the uplink transmission start subframe based on the
subframes where uplink data scheduling information is transmitted
(determining ePDCCH-to-PUSCH HARQ timing) and determining HARQ-ACK
transmission start subframe based on the subframes where uplink
data is transmitted (i.e., determining PUSCH-to-HARQ-ACK timing)
may apply to both the base station and the terminal, or any one of
the ePDCCH-to-PUSCH HARQ timing determination and the
PUSCH-to-HARQ-ACK timing determination may apply thereto. For
example, the ePDCCH-to-PUSCH HARQ timing determination may apply
while the PUSCH-to-HARQ-ACK timing determination does not.
[0192] FIG. 10a is a flowchart illustrating an operation by a base
station for a control channel transmission method according to an
embodiment of the present disclosure.
[0193] FIG. 10a exemplifies operations by the base station to
perform repetitive transmission on uplink HARQ process shown in
FIG. 9.
[0194] In step 1001, the base station transmits information on LTE
cell to the terminal and configures and transmits at least one of
repetitive transmission-related information and HARQ timing
information to the terminal.
[0195] The information on LTE cell may be UL-DL configuration
information and special subframe configuration information. The
information on LTE cell may be transmitted to the terminal through
system information (e.g., SIB information) or higher layer
information (i.e., higher layer signaling). The repetitive
transmission-related information, e.g., repetitive transmission
start subframe, repetitive transmission count, information on
frequency resources for transmitting repetitive transmission
channel, or information on groups of (downlink or uplink) subframes
where repetitive transmission may be conducted, may be transmitted
to the terminal via system information, higher layer information,
or L1 signal. The HARQ timing information may be information
indicating p1 and p2 as shown in FIG. 9, and this information may
be transmitted through system information (e.g., SIB information)
or higher layer information (i.e., higher layer signaling).
Alternatively, the HARQ timing information may be fixed to a
particular following the standard, and in such case, this
information might not be transmitted to the terminal. It is assumed
that the terminal (e.g., a low-cost terminal) is always set in
coverage enhancing mode, and in case it is set in the coverage
enhancing mode, it may communicate data through reception
transmission/reception. The coverage enhancing mode of the terminal
may be set by a higher layer signaling from the base station, and
the terminal always operating in the coverage enhancing mode may
signal to the base station that it is always operating in the
coverage enhancing mode. Or, the terminal may set itself to operate
in the coverage enhancing mode through reception of system
information or a random access procedure or the terminal may be set
to operate in the coverage enhancing mode by the base station.
[0196] In step 1002, the base station repeatedly transmits uplink
scheduling information based on the configured repetitive
transmission-related information in all the downlink subframes or
downlink subframes in a group of downlink subframes where the
configured repetitive transmission may be performed by a higher
layer signal.
[0197] In step 1003, the base station repeatedly receives uplink
data based on the configured repetitive transmission-related
information in the closest uplink subframe coming p1 subframes
after the downlink subframe where the repetitive transmission of
uplink scheduling information is complete.
[0198] In step 1004, the base station repeatedly transmits
HARQ-ACKs (ePDCCH or ePHICH) based on the configured repetitive
transmission-related information in the closest subframe within the
group of downlink subframes where the configured repetitive
transmission may be performed by a higher layer signal among the
subframes coming after the p2 subframes or the closest downlink
subframe coming p2 subframes after the uplink subframe where the
repetitive reception of uplink data is complete.
[0199] FIG. 10b is a flowchart illustrating an operation by a
terminal for a control channel transmission method according to an
embodiment of the present disclosure.
[0200] FIG. 10b describes operations by the terminal to perform
repetitive transmission on uplink HARQ process shown in FIG. 9.
[0201] In step 1011, the terminal receives information on LTE cell
from the base station and receives at least one of HARQ timing
information and repetitive transmission-related configuration
information configured by the base station.
[0202] The information on LTE cell may be UL-DL configuration
information and special subframe configuration information. The
information on LTE cell may be received from the base station
through system information (e.g., SIB information) or higher layer
information (i.e., higher layer signaling). The repetitive
transmission-related information, e.g., repetitive transmission
start subframe, repetitive transmission count, information on
frequency resources for transmitting repetitive transmission
channel, or information on groups of (downlink or uplink) subframes
where repetitive transmission may be conducted, may be transmitted
to the terminal via system information, higher layer information,
or L1 signal. The HARQ timing information may be information
indicating p1 and p2 as shown in FIG. 9, and this information may
be transmitted through system information (e.g., SIB information)
or higher layer information (i.e., higher layer signaling).
Alternatively, the HARQ timing information may be fixed to a
particular following the standard, and in such case, this
information might not be transmitted to the terminal. It is assumed
that the terminal (e.g., a low-cost terminal) is always set in
coverage enhancing mode, and in case it is set in the coverage
enhancing mode, it may communicate data through reception
transmission/reception. The coverage enhancing mode of the terminal
may be set by a higher layer signaling from the base station, and
the terminal always operating in the coverage enhancing mode may
signal to the base station that it is always operating in the
coverage enhancing mode. Or, the terminal may set itself to operate
in the coverage enhancing mode through reception of system
information or a random access procedure or the terminal may be set
to operate in the coverage enhancing mode by the base station.
[0203] In step 1012, the terminal repeatedly receives uplink
scheduling information based on the received repetitive
transmission-related information in all the downlink subframes or
downlink subframes in a group of downlink subframes where the
configured repetitive transmission may be performed by a higher
layer signal.
[0204] In step 1013, the terminal repeatedly transmits uplink data
based on the configured repetitive transmission-related information
in the closest uplink subframe coming p1 subframes after the
downlink subframe where the repetitive reception of uplink
scheduling information is complete.
[0205] In step 1014, the terminal repeatedly receives HARQ-ACKs
(ePDCCH or ePHICH) based on the received repetitive
transmission-related information in the closest subframe within the
group of downlink subframes where the configured repetitive
transmission may be performed by a higher layer signal among the
subframes coming after the p2 subframes or the closest downlink
subframe coming p2 subframes after the uplink subframe where the
repetitive transmission of uplink data is complete.
[0206] FIG. 11 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0207] FIG. 11 exemplifies a static TDD-based LTE cell 1101. The
base station performs transmission so that the repetitive
transmission of uplink data scheduling information is finished in
the downlink subframe having the uplink HARQ process of LTE cell
defined. That is, the base station may have the repetitive
transmission of uplink data scheduling information ended in the
downlink subframe having the uplink HARQ process defined by
adjusting the subframe where the repetitive transmission of uplink
data scheduling information is initiated or dynamically adjusting
(reducing or increasing) the number of times of repetitive
transmission. Accordingly, the terminal may perform uplink HARQ
repetitive transmission according to the uplink HARQ timing of the
subframes having the uplink HARQ process defined.
[0208] Downlink subframes and uplink subframes are configured in
the cell 1101 according to TDD UL-DL configuration #4. The terminal
may obtain TDD UL-DL configuration for the cell from system
information (e.g., SIB information) or higher layer information
(i.e., higher layer signaling). It is assumed that the terminal
(e.g., a low-cost terminal) is always set in coverage enhancing
mode, and in case it is set in the coverage enhancing mode, it may
communicate data through reception transmission/reception. The
coverage enhancing mode of the terminal may be set by a higher
layer signaling from the base station, and the terminal always
operating in the coverage enhancing mode may signal to the base
station that it is always operating in the coverage enhancing mode.
Or, the terminal may set itself to operate in the coverage
enhancing mode through reception of system information or a random
access procedure or the terminal may be set to operate in the
coverage enhancing mode by the base station.
[0209] A TDD-based downlink subframe and uplink subframe may
configure one uplink HARQ process. The subframes having such
pattern as shown in FIG. 11 configure one HARQ process. In FIG. 11,
downlink subframes #0, #1, #4, #5, #6, and #7 of radio frame i do
not configure uplink HARQ process, and it may be seen that
subframes #0, #1, #4, #5, #6, and #7 have no uplink HARQ timing
defined based on uplink HARQ process. Accordingly, the HARQ
transmission scheme shown in FIG. 11 may advantageously apply to
the situations where the number of downlink subframes configuring
no uplink HARQ process in the radio frame is larger as compared
with other UL-DL configurations (i.e., among the UL-DL
configurations, ones having relatively fewer downlink subframes
configuring HARQ processes). For a reason, many of the subframes
configuring a radio frame do not configure uplink HARQ process, and
thus, it would take long to perform repetitive transmission only
with the subframes configuring uplink HARQ process.
[0210] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal.
[0211] A group of uplink or downlink subframes may be a group of
downlink subframes for transmission of, e.g., uplink or downlink
scheduling. If the repetitive transmission-related information is
transmitted to the terminal and configured, the terminal may
attempt to detect PDCCH (or ePDCCH) for uplink or downlink
scheduling only in at least one downlink subframe in the group of
downlink subframes. Further, the terminal may also try to detect
PDCCH (or ePDCCH) for uplink or downlink scheduling only in at
least one downlink subframe within the group of downlink subframes
also for the PDCCH (or ePDCCH) for scheduling retransmission data
after repetitive transmission of uplink data by the uplink
scheduling or repetitive transmission of downlink data by downlink
scheduling.
[0212] In FIG. 11, it is assumed that a total of four times of
repetitive transmission is set. Although the instant embodiment
illustrates an example in which the uplink scheduling information,
uplink data, and HARQ-ACK are set to have the same number of times
of repetition, such pieces of information may be set to be
different from each other by a higher layer signal or may be
adjusted to be different dynamically by an L1 signal.
[0213] The base station transmits uplink data scheduling
information to the terminal through repetitive transmission in
subframe #5, subframe #6, subframe #7, and subframe #8 of radio
frame k 1102 (1111, 1112, 1113, and 1114). The base station
performs repetitive transmission four times from subframe #5 so
that the repetitive transmission of scheduling information is
complete in subframe #8 of radio frame k 1102. subframe #8 of radio
frame k 1102 is the subframe having an uplink HARQ process
defined.
[0214] Next, the terminal repeatedly transmits uplink data (PUSCH)
based on the uplink HARQ timing defined in subframe #8 of radio
frame k 1102, which is the last subframe of the repetitive
transmission of scheduling information. That is, the terminal
starts the repetitive transmission of uplink data from subframe #2
of radio frame k+1 1103 based on the uplink HARQ process defined in
subframe #8 of radio frame k 1102 (1121). Subsequently, the
terminal performs repetitive transmission in subframe #3 of radio
frame k+1 1103, subframe #2 of radio frame k+2 1104, and subframe
#3 of radio frame k+2 1104 as many times as the remaining
repetition count (1122, 1123, and 1124).
[0215] Next, repetitive transmission of HARQ-ACKs (ePDCCH or
ePHICH) is started from the subframe according to the uplink HARQ
timing based on the uplink HARQ process defined in subframe #3 of
radio frame k+2 1104 (i.e., subframe #9 of radio frame k+2 1104).
That is, the base station starts HARQ-ACK repetitive transmission
from subframe #9 of radio frame k+2 1104 (1131). The base station
repeatedly transmits HARQ-ACKs in subframe #0, subframe #1, and
subframe #4 of radio frame k+3 (1105) as many times as the
remaining repetition count (1132, 1133, and 1134).
[0216] Additionally, if there is repetitive transmission for uplink
data retransmission, transmission HARQ timing needs to be
determined. Since no uplink HARQ timing is defined in subframe #4
of radio frame k+3 1105 where the HARQ-ACK repetitive transmission
has been complete, the terminal is assumed to perform repetitive
transmission of HARQ-ACKs more than the repetition count indicated
by an L1 signal or the repetition count as set. The additional
repetitive transmission assumed above may have a level value next
to the number of times of repetitive transmission (i.e., the
repetition count) set by the higher layer signal. For example, if
the repetition count may be set to 1, 2, 4, or 8 by a higher layer
signal, and the repetition count as set is 4, the terminal may
assume that the repetition count is 8 while assuming that
four(=8-4) times of repetitive transmission is additionally
performed. Or, the additional repetitive transmission assumed may
have a count of repetitive transmission up to the subframe having a
next uplink HARQ timing defined. For example, the base station may
repeatedly transmit HARQ-ACKs (ePDCCH or ePHICH) up to subframe #8
of radio frame k+3 1105, which is the subframe having the next
uplink HARQ timing defined (1141, 1142, 1143, and 1144), and the
terminal may attempt to receive HARQ-ACKs (ePDCCH or ePHICH) up to
subframe #8 of radio frame k+3 1105. The additional repetition
count may have a level (or resolution) value that cannot be set by
higher layer signals. That is, the additional repetition count may
have any other value than 1, 2, 4, or 8. Resultantly, the terminal
may perform uplink data repetitive transmission based on the uplink
HARQ timing defined in subframe #8 of radio frame k+3 1105, and the
base station may repeatedly receive uplink data that is
retransmitted based on the uplink HARQ timing.
[0217] Alternatively, when the base station performs the HARQ-ACK
repetitive transmission from subframe #9 of radio frame k+2 1104,
the base station may perform such HARQ-ACK repetitive transmission
assuming such a repetition count as to allow the repetitive
transmission to be ended in the subframe having an uplink HARQ
timing defined, and the terminal may attempt to decode the
HARQ-ACKs repeated transmitted in consistence with the operation.
Here, the terminal may operate in two ways. First, the terminal may
attempt decoding at a repetition count of 1, 2, 4, or 8 that may be
set by a higher layer signal or L1 signal while assuming that the
repetitive transmission is finished in the subframe having the
uplink HARQ timing defined. In the first case, the subframe
corresponding to the set repetition count may be always defined as
the subframes having the uplink HARQ timing defined. Second, the
terminal may attempt to receive the HARQ-ACK repetitive
transmission under the assumption that the repetitive transmission
is finished in the subframe where the closest uplink HARQ timing is
defined, which comes a predetermined number (e.g., 4) subframes
after subframe #9. In the second case, the base station and the
terminal recognize that repetitive transmission may be performed at
any other repetition count than 1, 2, 4, or 8 as settable by a
higher layer signal or L1 signal.
[0218] Any one or both of the determination of uplink transmission
start subframe based on the uplink data scheduling information
transmission subframes upon initial transmission as described in
connection with FIG. 11 (ePDCCH-to-PUSCH HARQ timing determination)
and the determination of uplink data transmission start subframe
based on uplink data scheduling information transmission subframes
upon retransmission (retransmission ePDCCH-to-PUSCH HARQ timing
determination) may apply to the base station and the terminal.
[0219] FIG. 12 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0220] FIG. 12 exemplifies a static TDD-based LTE cell 1101.
Although an example has been described in which the base station
transmits uplink data scheduling information, an example where
downlink data scheduling information is transmitted is described in
connection with FIG. 12. Described is a scheme in which the base
station performs repetitive transmission on downlink data
scheduling information on LTE cell, the base station performs
repetitive transmission of downlink data according to the data
transmission timing after the repetitive transmission of the
scheduling information, and the terminal repeatedly transmits
HARQ-ACKs according to HARQ-ACK transmission timings after the
repetitive transmission of the downlink data. Specifically, the
base station performs repetitive transmission of downlink data in
the closest downlink subframe coming a predetermined number (n1) of
subframes after the subframe where the repetitive transmission of
downlink data scheduling information has been complete.
[0221] Downlink subframes and uplink subframes are configured in
the cell 1201 according to TDD UL-DL configuration #2. The terminal
may obtain TDD UL-DL configuration for the cell from system
information (e.g., SIB information) or higher layer information
(i.e., higher layer signaling). It is assumed that the terminal
(e.g., a low-cost terminal) is always set in coverage enhancing
mode, and in case it is set in the coverage enhancing mode, it may
communicate data through reception transmission/reception. The
coverage enhancing mode of the terminal may be set by a higher
layer signaling from the base station, and the terminal always
operating in the coverage enhancing mode may signal to the base
station that it is always operating in the coverage enhancing mode.
Or, the terminal may set itself to operate in the coverage
enhancing mode through reception of system information or a random
access procedure or the terminal may be set to operate in the
coverage enhancing mode by the base station.
[0222] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal.
[0223] A group of uplink or downlink subframes may be a group of
downlink subframes for transmission of, e.g., uplink or downlink
scheduling. If the repetitive transmission-related information is
transmitted to the terminal and configured, the terminal may
attempt to detect PDCCH (or ePDCCH) for uplink or downlink
scheduling only in at least one downlink subframe in the group of
downlink subframes. Further, the terminal may also try to detect
PDCCH (or ePDCCH) for uplink or downlink scheduling only in at
least one downlink subframe within the group of downlink subframes
also for the PDCCH (or ePDCCH) for scheduling retransmission data
after repetitive transmission of uplink data by the uplink
scheduling or repetitive transmission of downlink data by downlink
scheduling.
[0224] In FIG. 12, it is assumed that a total of four times of
repetitive transmission is set. Although the instant embodiment
illustrates an example in which the uplink scheduling information,
uplink data, and HARQ-ACK are set to have the same number of times
of repetition, such pieces of information may be set to be
different from each other by a higher layer signal or may be
adjusted to be different dynamically by an L1 signal.
[0225] The base station transmits downlink data scheduling
information to the terminal through repetitive transmission in
subframe #1, subframe #3, subframe #4, and subframe #5 of radio
frame k 1202 (1211, 1212, 1213, and 1214). Although examples 1211,
1211, 1213, and 1214 have been described in connection with FIG.
12, where downlink scheduling information is transmitted in
continuous downlink subframes, repetitive transmission of downlink
scheduling information may also be performed in only downlink
subframes within the group of downlink subframes where the
configured repetitive transmission may be performed by a higher
signal.
[0226] In FIG. 12, the repetitive transmission of downlink data
scheduling information has been complete in subframe #5 of radio
frame k 1202, and the base station starts the transmission of
downlink data in the closest downlink subframe coming n1 subframes
after subframe #5 of radio frame k 1202 (i.e., subframe #8 of radio
frame k 1202) (1215). n1 may be set as one of multiple values by a
higher layer signal or may be fixed to a particular value by a
standard. For example, n1 may be fixed to 3.
[0227] After the repetitive transmission (1215) of downlink data is
initiated by the base station in subframe #8 of radio frame k 1202,
the base station performs repetitive transmission of downlink data
in subframe #9 of radio frame k 1202 and subframe #0 and subframe
#1 of radio frame k+1 1203 as many times as the remaining
repetition count (1216, 1217, and 1218).
[0228] The following two schemes are proposed for timings for
performing HARQ-ACK repetitive transmission by the terminal for the
downlink data transmission.
[0229] A first scheme is to perform HARQ-ACK repetitive
transmission from subframe #7 of radio frame k+1 1203, which is the
closest uplink subframe coming n2 subframes after subframe #1 of
radio frame k+1 1203. n2 may be set as one of multiple values by a
higher layer signal or may be fixed to a particular value by a
standard. For example, n2 may be fixed to 4. Accordingly, the
terminal may start HARQ-ACK repetitive reception from subframe #7
of radio frame k+1 1203 (1219). The terminal may perform HARQ-ACK
repetitive transmission in subframe #2 and subframe #7 of radio
frame k+2 1204 and subframe #2 of radio frame k+3 1205 as many
times as the remaining repetition count (1220, 1221, and 1222).
[0230] The second scheme is that the terminal determines an uplink
subframe for HARQ-ACK transmission from the subframe where downlink
data repetitive transmission is complete based on DL-reference
UL/DL configuration. The DL-reference UL/DL configuration is a TDD
UL-DL configuration received from system information when no
enhanced interference management and traffic adaption (eIMTA) is
configured or when the terminal does not support the eIMTA or may
be eimta-HarqReferenceConfig-r12 defining an uplink HARQ-ACK timing
for repetitive transmission of downlink data received from a higher
signal when the eIMTA is supported and configured. For example, in
case the terminal does not support the eIMTA or has no eIMTA
configured, when the DL-reference UL/DL configuration is #2, n2
defined in subframe #1 is 6. Accordingly, HARQ-ACK repetitive
transmission may be performed from subframe #7 that is the subframe
coming six subframe #s after subframe #1 (1219). The terminal may
perform HARQ-ACK repetitive transmission in subframe #2 and
subframe #7 of radio frame k+2 1204 and subframe #2 of radio frame
k+3 1205 as many times as the remaining repetition count (1220,
1221, and 1222). As another example, in case the eIMTA is
configured in the terminal and supported, when the DL-reference
UL/DL configuration is #5, n2 defined in subframe #1 is 11.
Accordingly, repetitive transmission of HARQ-ACKs may be performed
from uplink subframe #2 of radio frame k+2 1204, which is the
subframe coming 11 subframes after subframe #1 of radio frame k+1
1203 (1220).
[0231] Further, in the embodiment shown in FIG. 12, since
repetitive transmission of the same downlink data is performed in
each subframe, there is no need of HARQ-ACK multiplexing
transmission through time domain bundling in the TDD cell, and the
terminal may transmit PUCCH format 1a/1b upon transmission of
HARQ-ACK. The transmission resource of PUCCH format 1a/1b may be
determined in association with the PRB or subband index of the
(E)PDCCH first transmitted or PRB or subband index of the (E)PDCCH
transmitted last. Or, the transmission resource of PUCCH format
1a/1b may also be determined through the PRB or subband index of
all (E)PDCCHs transmitted repeatedly.
[0232] FIG. 13 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0233] FIG. 13 exemplifies a FDD-based LTE cell 1301. FIG. 13
illustrates an example in which in the FDD cell the base station
transmits downlink data scheduling information. The cell 1301 is of
FDD type and has a downlink frequency f1 and an uplink frequency
f2. The base station performs repetitive transmission of downlink
data scheduling information in the downlink subframe of DL cell f1,
after the repetitive transmission of scheduling information is
ended, performs downlink data repetitive transmission according to
the data transmission timing, and after the transmission of
downlink data is ended, repeatedly transmits HARQ-ACKs in uplink
subframes of UL cell f2 depending on the HARQ-ACK transmission
timing. Specifically, the base station performs downlink data
transmission in the downlink subframe k1 subframes after the
subframe where the repetitive transmission of the scheduling
information has been complete.
[0234] The terminal may obtain the downlink frequency f1 while
performing cell search and may obtain the uplink frequency f2 by
receiving system information from the base station. It is assumed
that the terminal (e.g., a low-cost terminal) is always set in
coverage enhancing mode, and in case it is set in the coverage
enhancing mode, it may communicate data through reception
transmission/reception. The coverage enhancing mode of the terminal
may be set by a higher layer signaling from the base station, and
the terminal always operating in the coverage enhancing mode may
signal to the base station that it is always operating in the
coverage enhancing mode. Or, the terminal may set itself to operate
in the coverage enhancing mode through reception of system
information or a random access procedure or the terminal may be set
to operate in the coverage enhancing mode by the base station.
[0235] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal.
[0236] A group of uplink or downlink subframes may be a group of
downlink subframes for transmission of, e.g., uplink or downlink
scheduling. If the repetitive transmission-related information is
transmitted to the terminal and configured, the terminal may
attempt to detect PDCCH (or ePDCCH) for uplink or downlink
scheduling only in at least one downlink subframe in the group of
downlink subframes. Further, the terminal may also try to detect
PDCCH (or ePDCCH) for uplink or downlink scheduling only in at
least one downlink subframe within the group of downlink subframes
also for the PDCCH (or ePDCCH) for scheduling retransmission data
after repetitive transmission of uplink data by the uplink
scheduling or repetitive transmission of downlink data by downlink
scheduling.
[0237] In FIG. 13, it is assumed that a total of four times of
repetitive transmission is set. Although the instant embodiment
illustrates an example in which the uplink scheduling information,
uplink data, and HARQ-ACK are set to have the same number of times
of repetition, such pieces of information may be set to be
different from each other by a higher layer signal or may be
adjusted to be different dynamically by an L1 signal.
[0238] The base station transmits downlink data scheduling
information to the terminal through repetitive transmission in
subframe #0, subframe #1, subframe #2, and subframe #3 of radio
frame k 1302 (1311, 1312, 1313, and 1314). Although examples 1311,
1312, 1313, and 1314 have been described herein, where downlink
scheduling information is transmitted in continuous downlink
subframes, repetitive transmission of downlink scheduling
information may also be performed in only downlink subframes within
the group of downlink subframes where the configured repetitive
transmission may be performed by a higher signal.
[0239] In FIG. 13, the repetitive transmission of downlink data
scheduling information has been complete in subframe #3 of radio
frame k 1302, and the transmission of downlink data is started in
the downlink subframe coming k1 subframes after subframe #3 of
radio frame k 1302 (i.e., subframe #6 of radio frame k 1302)
(1315). k1 may be set as one of multiple values by a higher layer
signal or may be fixed to a particular value by a standard. For
example, k1 may be fixed to 3.
[0240] After the repetitive transmission (1315) of downlink data is
initiated by the base station in subframe #6 of radio frame k 1302,
the base station performs repetitive transmission of downlink data
in subframe #7, subframe #8, and subframe #9 of radio frame k 1302
as many times as the remaining repetition count (1316, 1317, and
1318).
[0241] Next, repetitive transmission of HARQ-ACKs is started from
subframe #3 of radio frame k+1 1303 which is the uplink subframe
coming k2 subframes after subframe #9 of radio frame k 1302. k2 may
be set as one of multiple values by a higher layer signal or may be
fixed to a particular value by a standard. For example, k2 may be
fixed to 4. Here, the terminal may perform HARQ-ACK repetitive
transmission from subframe #3 of radio frame k 1302 (1319). The
terminal may perform HARQ-ACK repetitive transmission in subframe
#4, subframe #5, and subframe #6 of radio frame k+1 1303 as many
times as the remaining repetition count (1320, 1321, and 1322).
[0242] FIG. 14 is a view illustrating a method for transmitting a
control channel according to an embodiment of the present
disclosure.
[0243] FIG. 14 exemplifies a FDD-based LTE cell 1401. FIG. 14
illustrates an example in which in the FDD cell the base station
transmits uplink data scheduling information. The cell 1301 is of
FDD type and has a downlink frequency f1 and an uplink frequency
f2. Described is a scheme in which the base station performs
repetitive transmission of uplink data scheduling information in
the downlink subframe of DL cell f1, the terminal performs uplink
data repetitive transmission in the uplink subframe of UL cell f2
according to the new uplink HARQ timing, and the base station
performs HARQ transmission according to the new uplink HARQ timing.
Specifically, the base station performs uplink data repetitive
transmission in the uplink subframe m1 subframes after the subframe
where the repetitive transmission of the uplink data scheduling
information has been complete.
[0244] The terminal may obtain the downlink frequency f1 while
performing cell search and may obtain the uplink frequency f2 by
receiving system information from the base station. It is assumed
that the terminal (e.g., a low-cost terminal) is always set in
coverage enhancing mode, and in case it is set in the coverage
enhancing mode, it may communicate data through reception
transmission/reception. The coverage enhancing mode of the terminal
may be set by a higher layer signaling from the base station, and
the terminal always operating in the coverage enhancing mode may
signal to the base station that it is always operating in the
coverage enhancing mode. Or, the terminal may set itself to operate
in the coverage enhancing mode through reception of system
information or a random access procedure or the terminal may be set
to operate in the coverage enhancing mode by the base station.
[0245] Repetitive transmission-related information on the base
station and the terminal, e.g., repetitive transmission start
subframe, repetitive transmission count, information on frequency
resources for transmitting repetitive transmission channel, or
information on groups of downlink or uplink subframes where
repetitive transmission may be conducted, may be previously
transmitted to the terminal or transmitted to the terminal via a L1
(Layer 1, physical layer) signal.
[0246] A group of uplink or downlink subframes may be a group of
downlink subframes for transmission of, e.g., uplink or downlink
scheduling. If the repetitive transmission-related information is
transmitted to the terminal and configured, the terminal may
attempt to detect PDCCH (or ePDCCH) for uplink or downlink
scheduling only in at least one downlink subframe in the group of
downlink subframes. Further, the terminal may also try to detect
PDCCH (or ePDCCH) for uplink or downlink scheduling only in at
least one downlink subframe within the group of downlink subframes
also for the PDCCH (or ePDCCH) for scheduling retransmission data
after repetitive transmission of uplink data by the uplink
scheduling or repetitive transmission of downlink data by downlink
scheduling.
[0247] In FIG. 14, it is assumed that a total of four times of
repetitive transmission is set. Although the instant embodiment
illustrates an example in which the uplink scheduling information,
uplink data, and HARQ-ACK are set to have the same number of times
of repetition, such pieces of information may be set to be
different from each other by a higher layer signal or may be
adjusted to be different dynamically by an L1 signal.
[0248] The base station transmits uplink data scheduling
information to the terminal through repetitive transmission in
subframe #0, subframe #1, subframe #2, and subframe #3 of radio
frame k 1402 (1411, 1412, 1413, and 1414). Although examples 1411,
1412, 1413, and 1414 have been described herein, where uplink
scheduling information is transmitted in continuous downlink
subframes, repetitive transmission of uplink scheduling information
may also be performed in only downlink subframes within the group
of downlink subframes where the configured repetitive transmission
may be performed by a higher signal.
[0249] In FIG. 14, the repetitive transmission has been complete in
subframe #3 of radio frame k 1402, and the terminal performs the
repetitive transmission of uplink data in the uplink subframe
coming ml subframes after subframe #3 of radio frame k 1402 (i.e.,
subframe #7 of radio frame k 1402) (1415). m1 may be set as one of
multiple values by a higher layer signal or may be fixed to a
particular value by a standard. For example, ml may be fixed to
4.
[0250] After the repetitive transmission (1415) of uplink data is
initiated by the terminal in subframe #7 of radio frame k 1402, the
terminal performs repetitive transmission of uplink data in
subframe #8 and subframe #9 of radio frame k 1402 and subframe #0
of radio frame k+1 1403 as many times as the remaining repetition
count (1416, 1417, and 1418).
[0251] Next, repetitive transmission of HARQ-ACKs (ACKs/NACKs for
UL grants which are transmitted through ePDCCH, MPDCCH, or M-PDCCH)
is started from the downlink subframe (i.e., subframe #4 of radio
frame k+1 1403) coming m2 subframes after subframe #0 of radio
frame k+1 1403. Or, repetitive transmission of HARQ-ACKs (ePDCCH)
may be performed from the closest subframe in the group of downlink
subframes where the configured repetitive transmission may be
performed by a higher layer signal among the subframes coming m2
subframes after subframe #0 of radio frame k+1 1403. Here, the
terminal will detect HARQ-ACK (ePDCCH) only in the subframes within
the subframe group. m2 may be set as one of multiple values by a
higher layer signal or may be fixed to a particular value by a
standard. For example, m2 may be fixed to 4. Accordingly, the base
station performs HARQ-ACK (ePDCCH) repetitive transmission from
subframe #4 of radio frame k+1 1403 (1419). The base station
performs HARQ-ACK (ePDCCH) repetitive transmission in subframe #5,
subframe #6, and subframe #7 of radio frame k+1 1403 as many times
as the remaining repetition count (1420, 1421, and 1422).
[0252] Any one or both of the determination of uplink transmission
start subframe based on the uplink data scheduling information
transmission subframes as described in connection with FIG. 14
(ePDCCH-to-PUSCH HARQ timing determination) and the determination
of HARQ-ACK transmission start subframe based on uplink data
transmission subframes (PUSCH-to-HARQ-ACK timing determination) may
apply to the base station and the terminal.
[0253] In all of the above-described embodiments (FIGS. 5 to 14),
since the same data is repeatedly transmitted in each subframe, the
`DL/UL downlink assignment index (DAI)` field and the `HARQ process
number` field defined in the (E)PDCCH of TDD cell may be reserved,
fixed to a particular value (e.g., `0`), or the fields may be
disregarded by the terminal regardless of what values are set
thereto. Or, the (E)PDCCH may be configured without the fields, and
the terminal may decode the (E)PDCCH assuming that the payload size
of the (E)PDCCH except the fields.
[0254] In all of the above-described embodiments (FIGS. 5 to 14),
since the same data may be repeatedly transmitted in each subframe,
the `redundancy version` field defined in the (E)PDCCH may be
reserved, fixed to a particular value (e.g., `0`), or may be
disregarded regardless of what values are set thereto. Or, the
(E)PDCCH may be configured without the field, and the terminal may
decode the (E)PDCCH assuming that the payload size of the (E)PDCCH
except at least the `redundancy version` field. During each
repetitive transmission, the `redundancy version` may be configured
by a higher layer signal or fixed by a standard, and the terminal
may decode data according to the redundancy version.
[0255] In all of the above-described embodiments (FIGS. 5 to 14),
the value set for initial repetitive transmission may be reused as
the `redundancy version` for each retransmission, and the terminal
may decode data according to the reused `redundancy version.`
[0256] In all of the above-described embodiments (FIGS. 5 to 14),
the number of times of repetitive transmission upon each
retransmission may be set by a higher layer signal, and in case
data reception fails upon initial repetitive transmission, a larger
repetition count may be used upon repetitive transmission through
retransmission. That is, the base station may set a repetition
count that may be used upon repetitive transmission through
retransmission for the terminal by a higher layer signal. Or, in
case a larger repetition count is determined by a standard to be
used upon repetitive transmission through retransmission, the base
station may automatically perform repetitive transmission through
retransmission at a larger repetition count, and the terminal may
automatically attempt to decode using a larger repetition count
upon repetitive reception through retransmission.
[0257] FIGS. 15a and 15b are views illustrating a communication
network including an LAA cell to which the present disclosure
applies.
[0258] Considering that the number of licensed bands, such as LTE
(this term is used to collectively refer to LTE-A or other advanced
versions of LTE) frequency, is limited, it is being researched to
provide LTE services on an unlicensed band such as 5 GHz band, and
this is called licensed assisted access (LAA). In case LAA is
adopted, what is considered is that carrier aggregation (CA) for
LTE-A applies so that licensed band LTE cell is operated as a
primary serving cell (Pcell), and unlicensed band LAA cell is
operated as a secondary serving cell (Scell). Accordingly, like in
LTE-A, feedbacks generated in the LAA cell that is an S Cell should
be transmitted only from the P cell, and the FDD and TDD1 may apply
to the LAA cell.
[0259] FIG. 15a illustrates an example in which an LTE cell 1502
and an LAA cell 1503 coexist in a single small-sized base station
1501 over a communication network.
[0260] The terminal 1504 communicates data with the base station
through the LTE cell 1502 and the LAA cell 1503. In this case,
there is no limitation on the duplex scheme (i.e., whether FDD or
TDD) of the LTE cell 1502 or LAA cell 1503. However, uplink
transmission may be performed only through the LTE cell 1502 in
case the LTE cell 1502 is a Pcell.
[0261] FIG. 15b illustrates an example in which an LTE macro base
station 1511 for larger coverage and an LAA small-sized base
station 1512 for increasing data transmission are installed in a
communication network.
[0262] There is no limitation on the duplex scheme of the LTE macro
base station 1511 or LAA small-sized base station 1512. However,
uplink transmission is performed only through the LTE base station
1511 in case the LTE base station 1511 is a Pcell. At this time,
the LTE base station 1511 and the LAA base station 1512 are assumed
to have an ideal backhaul network. Accordingly, fast inter-base
station X2 communication 1513 is possible, and even when uplink
transmission is made only to the LTE base station 1511, the LAA
base station 1512 may receive relevant control information from the
LTE base station 1511 in real-time via the X2 communication 1513.
In the systems shown in FIGS. 15A and 15B, the LTE cell and LAA
cell each may have a plurality of serving cells and they together
may support up to 32 serving cells. Accordingly, the schemes
proposed according to the present disclosure may apply to both the
system of FIG. 15a and the system of FIG. 15b.
[0263] Meanwhile, in LTE Rel-12, up to five serving cells may be
configured in the terminal by CA. The terminal is configured by
higher layer information to periodically transmit channel
information for data scheduling for the base station.
[0264] In the embodiment of the present disclosure, the operation
of periodically transmitting control information is called
`periodic channel information transmission`, and the `periodic
channel information` is transmitted through uplink control channel
(physical uplink control channel, PUCCH) of Pcell. Further, each
serving cell independently defines a periodic channel information
transmission operation for terminals having CA configured. Types of
information to be transmitted in the periodic channel information
transmission operation include subband CQI, subband CQI and second
PMI, wideband CQI and PMI (precoding matrix indicator), wideband
first PMI, wideband CQI and second PMI, wideband CQI and first PMI
and second PMI, RI (rank indicator), wideband CQI, RI and first
PMI, RI and PTI (precoder type indicator).
[0265] Among the pieces of information, information to be
transmitted according transmission modes by higher layer
information is determined, and transmission information is set to
have a period and offset by higher layer information.
[0266] In the periodic channel information transmission operation,
in case in one subframe periodic channel information transmission
times are the same, one subframe has been designed to transmit only
periodic channel information for one serving cell through PUCCH of
Pcell. Further, also in one serving cell, in case the transmission
times of multiple pieces of channel information are identical in
one subframe, only one piece of channel information has been
designed to be transmitted. In this case, priority is set by the
type of information to be transmitted or with a serving cell index,
so that among the periodic channel information configured to be
transmitted for multiple serving cells, only periodic channel
information for one serving cell is transmitted while the periodic
channel information for the other serving cells is discarded.
[0267] For example, in case transmission times for multiple pieces
of channel information for one serving cell are identical,
information including RI (rank indication) has a highest priority,
and in case transmission times for channel information for multiple
serving cells are identical, the one including RI or first PMI has
a highest priority, and channel information of the serving cell
including wideband CQI has a second highest priority. Further, in
case pieces of channel information having the same priority are
transmitted for different serving cells, the channel information of
serving cell having a lower serving cell index has a higher
priority. Indeed, since Rel-10 assumes scenario with two serving
cell configurations, periodic channel information transmissions for
multiple serving cells would not be highly likely to conflict with
each other, and collision may be easily avoided as the base station
sets different periodic channel information transmission periods or
offsets for serving cells.
[0268] However, assuming a scenario with up to 32 serving cell
configurations as in Rel-13, it is difficult to avoid collision
between periodic channel information transmissions in multiple
serving cells simply by allowing the base station to set different
periodic channel information transmission periods or offsets for
serving cells. Accordingly, the probability that channel
information transmission times are identical in one subframe is
well larger than that in Rel-12 Further, if the terminal transmits
only one periodic channel information only in one serving cell
while discarding periodic channel information for the remaining
serving cells as defined in Rel-12, the Rel-13-based base station
has difficulty doing optimal scheduling on the remaining serving
cells, and this negative affects the volume of data transmitted to
the terminal.
[0269] In case the base station transmits a UL grant including a
non-periodic channel information request for transmission of
channel information for multiple serving cells, it needs transmit
UL grant whenever periodic channel information transmission times
become identical in multiple serving cells or in one serving cell,
this results in waste of PDCCH transmission resources and
resultantly reduced PDCCH resources for scheduling other terminals
in the base station. Accordingly, in case up to 32 serving cell
configurations are supported for CA in Rel-13, a need comes along
for a method for supporting periodic channel information
transmission for as many serving cells as possible in one subframe
without the need of PDCCH transmission resources.
[0270] According to the present disclosure, there are provided
schemes for transmitting channel information on multiple serving
cells by a terminal without wasting transmission resources of
downlink control channels in a wireless communication system
supportive of carrier aggregation.
[0271] In an embodiment of the present disclosure, UCI PUSCH
transmission is described.
[0272] The transmission scheme proposed in this disclosure is
called UCI PUSCH transmission in order to prevent loss of lots of
channel information due to being identical in transmission time
between multiple pieces of channel information when transmitting
periodic channel information through PUCCH. The UCI PUSCH
transmission according to the present disclosure is a method by
which multiple pieces of channel information are transmitted
through PUSCH.
[0273] The mode in which the terminal performs UCI PUSCH
transmission may be set by a higher layer signal. According to an
embodiment of the present disclosure, the higher layer signal is
defined as UCIPUSCHmode. If UCIPUSCHmode is 0, i.e., if UCI PUSCH
transmission mode is not configured, the terminal transmits only
one channel information through PUCCH in one subframe when
transmitting periodic channel information (it follows the Rel-12
operation). If UCIPUSCHmode is 1, i.e., if UCI PUSCH transmission
mode is configured, UCI PUSCH transmission is configured in the
terminal so that many pieces of channel information may be
transmitted through PUSCH in one subframe. The higher layer signal
UCIPUSCHmode may be replaced as the transmission resource for
transmitting channel information (UCI) being configured by a higher
layer signal. That is, the UCI PUSCH operation mode for the
terminal may be configured by having the transmission resource for
transmitting periodic channel information through PUSCH configured
by a higher layer signal.
[0274] The UCI PUSCH operation by the terminal after the UCI PUSCH
operation mode has been set by higher layer signal is activated as
follows. First, in case the transmission times of two or more
different pieces of channel information for one serving cell in one
subframe are identical, UCI PUSCH is activated instead of PUCCH
transmission. Next, in case the transmission times of two or more
pieces of channel information for different serving cells in one
subframe are identical, UCI PUSCH is activated instead of PUCCH
transmission. At this time, the two or more pieces of channel
information for different serving cells may be the same type of
channel information or different types of channel information.
[0275] If UCI PUSCH is activated, the terminal multiplexes channel
information for preset at least one or more serving cells by a
preset method for transmitting through PUSCH. Here, the pieces of
channel information may include all of the pieces of channel
information according to the periodic transmission configuration
made to be transmitted for each serving cell. As another example,
it may include pieces of channel information that could not be
transmitted as the channel information transmission times are
identical, together with one piece of channel information that may
be originally transmitted. The pieces of channel information may be
multiplexed in the sequence depending on the type of channel
information and serving cell index. That is, the terminal may sort
the pieces of channel information per serving cell index, and the
sorted pieces of channel information per serving cell index may be
resorted and then multiplexed depending on the type of channel
information. Or, the terminal may sort the pieces of channel
information per type of channel information, and the sorted pieces
of channel information per type may be resorted and multiplexed per
serving cell index.
[0276] The channel information may be multiplexed, coded and
modulated with a preset coding rate and modulation scheme, and may
be transmitted to the base station through PUSCH over preset
transmission resources. The coding rate, modulation scheme, and
transmission resource, together with UCI PUSCH operation mode, may
be set by higher layer signals. As another example, the coding
rate, modulation scheme, and the position of initial resource,
i.e., initial PRB start position, may be set by a higher layer
signal, and the position of resource, i.e., the start position of
PRB, may be set to be different by a predefined hopping pattern
whenever each channel information transmission time comes
identical. As inputs of the hopping pattern, radio network
temporary identity (RNTI), subframe number, and position of initial
resource may be used.
[0277] According to an embodiment of the present disclosure,
serving cells performing UCI PUSCH transmission are described.
[0278] The serving cell for transmission of UCI PUSCH may be a
Pcell. Since Pcell is set to transmit PUCCH, when two or more
periodic channel information transmissions conflict, UCI PUSCH
instead of PUCCH may be transmitted from Pcell, and pieces of
uplink control information (UCI) transmitted through PUCCH when UCI
PUSCH is transmitted may be transmitted through PUSCH (rather than
through PUCCH), reducing PUCCH transmit power.
[0279] Alternatively, serving cell for UCI PUSCH transmission may
be secondary cell (Scell). In this case, one Scell of multiple
Scells may be chosen as the serving cell for transmission of UCI
PUSCH based on the cell index. As an example, the Scell having the
lowest cell index may be chosen as the serving cell for
transmission of UCI PUSCH. If UCI PUSCH is transmitted in Scell,
the UCI transmission procedure by the terminal may be simply
defined. For example, when different TDD UL-DL configurations apply
between different bands in inter-band TDD CA, since UCI
transmission timings in Scell and Pcell differ, a new terminal
procedure should be defined to have UCIs for Scell transmitted in
Pcell. However, if UCIs for Scell are transmitted in Scell, no new
terminal procedure needs to be defined.
[0280] Subsequently, described is a method for grouping serving
cells and transmitting through uplink control channel.
[0281] FIG. 16 is a view illustrating a method for transmitting
channel information by grouping serving cells according to an
embodiment of the present disclosure.
[0282] This method (rather than used when channel transmission
times of different serving cells are identical) is a method in
which serving cells are grouped to transmit the grouping
information to the terminal through a higher layer signal, and the
terminal transmits the same, together with channel information on
the grouped serving cells, through uplink control channel.
[0283] The grouping information may indicate a group ID and at
least one serving cell included in the group. The uplink control
channel through which control information is transmitted may be a
PUSCH that is an uplink data channel to transmit a great amount of
feedback, and it may also be transmitted from the terminal through
a new uplink control format.
[0284] Resource information on the PUSCH channel is previously
transmitted from the base station to the terminal through a higher
layer signal (higher layer signaling), and since the number of
serving cells included in each group is already determined, the
transmission resource information may be previously configured and
transmitted to the terminal by a higher layer signal, and the
terminal transmits channel information on the serving cell using
the resource information. Accordingly, the transmission resource
occupancy may be optimized without waste of transmission resources.
The base station may set different transmission periods and offsets
for different serving cell groups. As an example, the base station
may choose and determine one of offsets and transmission periods of
CQI transmission used in PUCCH transmission for the transmission
periods and offsets of different serving cell groups. Accordingly,
when PUSCH channel is transmitted, PUSCH transmissions including
different groups of channel information may be avoided from being
identical.
[0285] FIG. 16 illustrates an example in which a total of eight
serving cell groups (e.g., 1601, 1602, 1603, 1604, and 1605) are
configured for the terminal. The example shows that each cell group
includes a different number of cells. Further, LAA cell which is
unlicensed cell and LTE cell which is licensed cell may be bundled
into one cell group, or they may be put in different cell groups.
For example, the method of transmitting channel information through
PUSCH by the cell grouping method may apply when the number of
cells exceeds five, and in case there are five or less cells,
channel information is transmitted through PUCCH, and in case at
least two or more channel information transmission times are
identical, one channel information may be transmitted while the
others may be dropped.
[0286] Further, the transmission may be performed in different
PUCCH formats depending on the amount of channel information
supposed to be transmitted in one subframe. For example, in case
the pieces of channel information supposed to be transmitted in one
subframe may be transmitted in (legacy) PUCCH format 2, the
terminal may transmit the channel information in PUCCH format 2,
and in case the pieces of channel information supposed to be
transmitted in one subframe are for multiple serving cells, the
terminal may use a new PUCCH format or may perform the transmission
through the PUSCH channel.
[0287] In case the pieces of channel information supposed to be
transmitted by the terminal in one subframe exceeds the payload
size in which the new PUCCH format may send out or the payload size
that may be included in the PUSCH PRB upon transmission through the
PUSCH channel, the terminal may drop the pieces of channel
information regarding a particular cell group while transmitting
only the pieces of channel information regarding the remaining cell
groups. The selection of the cell group to be dropped may be
performed based on the cell group index. As an example; there may
be selected k cell groups (k is equal or larger than 1) having
lower indexes including the cell group having the lowest cell group
index among the cell groups where channel information should be
transmitted or k cell groups having higher indexes including the
cell group having the highest cell group index. k may be
transmitted to the terminal through a higher layer signal,
determined by an equation or table, or may be previously determined
as a constant. For example, when there is a group of serving cells
whose cell group indexes are 1, 2, and 3, if the payload size in
which the new PUCCH format may be sent out may include two cell
groups, and a higher cell group index is rendered to be dropped,
the pieces of channel information on the serving cells with cell
group indexes 1 and 2 may be transmitted in the new PUCCH format
(or through PUSCH), and the pieces of channel information on the
serving cells with cell group index 3 may be dropped.
[0288] If the payload size in which transmission may be performed
in the new PUCCH format (or through PUSCH) may include channel
information on some serving cells of the cell group to be dropped,
the channel information on some serving cells of the cell group to
be dropped may be additionally transmitted. The selection of some
serving cells may be performed depending on the importance of
channel information (e.g., RI>wideband CQI>subband CQI), and
if the pieces of channel information have the same importance, the
selection may be performed depending on serving cell indexes (e.g.,
a lower index indicates a higher importance). Channel information
on serving cells that cannot be transmitted is dropped.
[0289] FIG. 17 is a view illustrating a method for communicating
periodic channel information by a base station and a terminal
according to an embodiment of the present disclosure.
[0290] Described with reference to FIG. 17 is a method for setting
a transmission period and offset for periodic channel information
transmission of each serving cell according to an embodiment of the
present disclosure. The base station may have the same effect as
that obtained by grouping serving cells in the embodiment described
in connection with FIG. 16 by setting a transmission period and
offset for periodic channel information transmission of a serving
cell.
[0291] This embodiment is a method of making the channel
information transmission times of different serving cells
consistent with one another, so that when the pieces of channel
information of the serving cells collide with each other in one
subframe, the terminal also transmits the pieces of channel
information of the serving cells through uplink control
channel.
[0292] In the method according to this embodiment, the operations
exemplified in FIG. 17 may be selectively included, and this
embodiment need not be practiced in such a way that all of the
operations are included.
[0293] The base station 1700 may allocate resources for
transmission of periodic channel information of each serving cell
(1720). At this time, the base station 1700 may make the channel
information transmission times of some serving cells consistent
with one another.
[0294] Although the base station makes a configuration so that
channel information transmission periods and offsets of different
serving cells are the same, the base station may transmit at least
one higher layer signal to the terminal to prevent the terminal to
transmit only channel information of one cell while dropping the
others (1722 and 1724). The higher layer signal is a signal
instructing the terminal to together multiplex and transmit all
pieces of channel information even when the base station makes a
configuration so that channel information transmission periods and
offsets of different serving cells are the same. The higher layer
signal transmitted from the base station may be either or both of a
configuration of uplink control format allowing a great amount of
feedback to be transmitted through uplink control channel
(including resource configuration, channel information transmission
period, and offset information for transmission of uplink control
format) and a configuration of uplink control channel having an
uplink data channel structure (including resource configuration,
channel information transmission period, and offset information for
transmission of uplink control channel), or it may be a particular
signal through a higher layer signal.
[0295] The terminal 1710 having received the higher layer signal
may select at least one serving cell among multiple serving cells
and generate periodic channel information of the selected serving
cell (1726).
[0296] The terminal 1710 may transmit the control information (UCI)
including the generated periodic channel information on uplink
through the resource indicated by the higher layer signal
(1728).
[0297] According to the present disclosure, the higher layer signal
for configuration of uplink control channel having the uplink data
channel structure is referred to as
CQI-ReportPeriodicForNewPUCCHFormat 1724, and the higher layer
signal for configuration of uplink control format is referred to as
CQI-ReportPeriodic 1722. CQI-ReportPeriodicForNewPUCCHFormat 1724
may be configured in addition to the higher layer signal
(CQI-ReportPeriodic 1722 including the resource configuration for
PUCCH format 2 transmission) for PUCCH format 2, which is an uplink
control format allowing the terminal to transmit the channel
information of only one cell.
[0298] In case CQI-ReportPeriodicForNewPUCCHFormat 1724 and
CQI-ReportPeriodic 1722 are simultaneously configured (or on and
activated at the same time), the terminal 1710 may determine
whether the pieces of channel information of multiple cells should
be simultaneously transmitted in one subframe. In case the pieces
of channel information of multiple cells are not required to be
simultaneously transmitted and rather the channel information of
only one cell should be transmitted, the terminal 1710 transmits
the periodic channel information of the single cell according to
the transmission resource of PUCCH format 2 configured in
CQI-ReportPeriodic 1722, and in case the pieces of channel
information of the multiple cells should be simultaneously
transmitted, the terminal 1710 may multiplex and transmit the
pieces of channel information of the multiple cells according to
the transmission resource of the `new PUCCH format` configured in
CQI-ReportPeriodicForNewPUCCHFormat 1724.
[0299] Further, in case only CQI-ReportPeriodicForNewPUCCHFormat
1724 is configured (or on and activated), and CQI-ReportPeriodic
1722 is not (or off and deactivated), the terminal 1710 may always
transmit pieces of channel information according to the
transmission resource of the new PUCCH format configured in
CQI-ReportPeriodicForNewPUCCHFormat 1724 regardless of whether the
pieces of channel information of the multiple cells should be
simultaneously transmitted in one subframe or the channel
information of only one cell should be transmitted.
[0300] Further, in case CQI-ReportPeriodicForNewPUCCHFormat 1724 is
not configured (or set to be off and deactivated), and
CQI-ReportPeriodic 1722 is configured (or on and activated), if the
pieces of channel information of multiple cells should be
simultaneously transmitted in one subframe, the terminal 1710 may
select and transmit the channel information of a cell with the
highest priority according to the transmission resource of PUCCH
format 2 configured in CQI-ReportPeriodic 1722. In case the pieces
of channel information of multiple cells are not required to be
simultaneously transmitted and the channel information of only one
cell should be transmitted, the terminal 1710 may transmit the
channel information of the single cell according to the
transmission resource of PUCCH format 2 configured in
CQI-ReportPeriodic 1722.
[0301] The base station 1700 may make a setting using the
above-exemplified higher layer signal 1724 or 1722 so that the
periods and offsets of transmission of periodic pieces of channel
information of different serving cells which should together
receive pieces of channel information in one subframe are the same
(1720). The base station 1700 allows the periodic channel
information transmission times (i.e., periods and offsets) of the
serving cells to be consistent, allowing for such an effect as if
the base station 1700 intentionally grouped the serving cells that
desire to simultaneously receive the pieces of channel information.
The uplink control channel through which control information is
transmitted may be a PUSCH that is an uplink data channel to
transmit a great amount of feedback, and it may also be transmitted
through a new uplink control format defined by the higher layer
signal.
[0302] The resource information of PUSCH channel may be previously
transmitted from the base station 1700 to the terminal 1710 via the
higher layer signal 1724 or 1722. Since the number of serving cells
whose periodic channel information transmission times have been
intentionally rendered to be identical is previously determined by
the base station 1700, it is possible to previously configure
resource information of PUSCH channel and to transmit the resource
information to the terminal 1710 via the higher layer signal 1724
or 1722. Accordingly, the terminal 1710 may transmit periodic
channel information of the serving cells using the resource
information. Accordingly, the base station 1700 may optimize the
transmission resource occupancy without waste of transmission
resources.
[0303] As an example, the base station 1700 may make a setting so
that the Pcell 1611, the Scell1 1612, the Scell3 1613, and the
Scell4 1614 which are intended to be together received in one
subframe as shown in FIG. 16 have the same period and offset of the
periodic channel information transmission. Here, if the periodic
channel information pieces of the serving cells are set to have the
same transmission period and offset, the terminal 1710 does not
drop depending on the priority of the periodic channel information
pieces even when the periodic channel information pieces have the
same transmission time, and may use a control channel format or
PUSCH by which a great amount of control information may be
transmitted to transmit together the periodic channel information
pieces in one subframe.
[0304] In case the pieces of channel information supposed to be
transmitted by the terminal 1710 in one subframe exceeds the
payload size in which the new PUCCH format may send out or the
payload size that may be included in the PUSCH PRB upon
transmission through the PUSCH channel, the terminal 1710 may
select a particular serving cell and may transmit the channel
information of only the selected serving cell. The selection of the
serving cell whose periodic channel information is to be
transmitted by the terminal 1710 may be performed depending on the
importance of channel information (e.g., RI>wideband
CQI>subband CQI), and accordingly, if the pieces of channel
information have the same importance, the selection may be
performed depending on serving cell indexes (e.g., a lower index
indicates a higher importance). The terminal 1710 may drop the
channel information pieces of the serving cells which cannot be
transmitted, rather than transmitting.
[0305] Now, the present disclosure proposes a specific method for
defining transmission/reception operations by a low-cost terminal
with a limited bandwidth regarding the bandwidth maximally
processable within the whole channel bandwidth or system
transmission bandwidth and operating normal LTE terminal and
low-cost terminal in the same system.
[0306] Hereinafter, the frequency region defined by the bandwidth
available by a low-cost terminal is referred to as a subband or
narrowband.
[0307] FIG. 18 is a concept view illustrating an example of
configuring and operating subband where the low-cost terminal
operates within the system transmission bandwidth according to an
embodiment of the present disclosure.
[0308] FIG. 18 illustrates a scheme of previously configuring and
operating a subband where a low-cost terminal operates in the
system transmission bandwidth.
[0309] The size 1804 of subband where the low-cost terminal
operates cannot be larger than the system transmission bandwidth
1802, and is generally assumed as the minimum transmission
bandwidth supported by the LTE system, i.e., 1.4 MHz (six
consecutive PRBs). The subband is relatively a narrow band, and
thus, the number of low-cost terminals supported with one subband
may be limited. If the number of low-cost terminals to be supported
by the system increases, a number of low-cost terminals may be
simultaneously served by configuring/operating a plurality of
subbands. FIG. 18 illustrates an example in which three subbands,
i.e., subband A 1810, subband B 1812, and subband C 1814 are
configured in the system transmission bandwidth.
[0310] The low-cost terminal performs data or control signal
communication operation through one subband at some moment. Since
control channels for normal terminals are broadband-transmitted
over the system transmission bandwidth in the control channel
region 1808 of each subframe, the low-cost terminal cannot receive
the control channels for normal terminals. Here, the normal
terminal is a terminal with its used transmission bandwidth not
limited to the subband region and may refer to a normal LTE
terminal. Control channels and data channels for low-cost terminal
may be transmitted, mapped to the subband region except the control
channel region 1808. Here, the control channel and data channel for
low-cost terminal may be transmitted in the same or different
subframes. In case the control channel and data channel for
low-cost terminal are transmitted in different subframes, a
relative time relation may be previously defined as a fixed value
or may be known to the terminal through signaling by the base
station.
[0311] Control channels for normal LTE terminal are spread over the
system transmission bandwidth in the control channel region 1808,
mapped, and transmitted, and data channels and EPDCCH for normal
LTE terminal may be mapped and transmitted according to the
scheduling operation by the base station in the remaining region
except the subband where the low-cost terminal operates and the
control channel region 1808. However, although a subband is
assigned for low-cost terminal, in case control channel or data
channel for low-cost terminal is not transmitted at some moment,
the base station may use the subband as data channel for normal LTE
terminal in order to efficiently utilize radio resources.
[0312] Subband control information such as the number or position
of subbands may be previously configured and operated. The subband
control information may be configured independently for downlink
and uplink. Although FIG. 18 primarily illustrates for downlink, it
would not harm the representation of overall concept for uplink.
However, uplink does not include a separate control channel region
like the control region 1808. The base station gives the subband
control information to the low-cost terminal through signaling. The
subband control information may be included in MIB (master
information block) or SIB (system information block) for low-cost
terminal or radio resource control (RRC) signaling for low-cost
terminal. The signaling may be commonly known to a plurality of
low-cost terminals. Accordingly, the base station need inform each
low-cost terminal of the subband the terminal should specifically
operate among the known subbands through individual additional
signaling to each low-cost terminal. For example, low-cost terminal
A may be set to operate on subband A 1810, low-cost terminal B on
subband B 1812, and low-cost terminal C on subband C 1814.
Accordingly, each low-cost terminal may perform
transmission/reception operation only in designated subband.
[0313] While the low-cost terminal proceeds with initial access,
the terminal may receive primary synchronization signal
(PSS)/secondary synchronization signal (SSS) and physical broadcast
channel (PBCH) that are transmitted, mapped with a middle 1.4 MHz
band (e.g., the band corresponding to subband B 1812 in FIG. 18) in
the system bandwidth. The low-cost terminal may detect the PSS/SSS
to obtain time-frequency sync and cell ID and obtain necessary
system information, MIB, through PBCH decoding. After the initial
access is complete, the low-cost terminal switches frequency to the
subband designated to the terminal and performs
transmission/reception operation.
[0314] After the initial access is complete, the low-cost terminal
may also perform time-frequency syncing, or to obtain MIB, it may
perform PSS/SSS detection and PBCH decoding. For example, low-cost
terminal A operating on subband A 1810, in order to obtain
additional time-frequency sync or MIB after initial access, may
stop operating on subband A 1810 and perform PSS/SSS detection and
PBCH decoding on the middle 1.4 MHz band. Low-cost terminal A,
after obtaining time-frequency sync or PBCH decoding, may resume
operation on subband A 1810.
[0315] FIG. 18 illustrates an example in which the subband
configuration for each low-cost terminal is maintained for a
relatively long time. For example, subband configuration for
low-cost terminal B remains at subband B 1812 without change from
subframe i 1803 to subframe i+k 1806 (k>0). When desiring to
change the subband configuration, the base station informs the
terminal of change in subband configuration through the
above-described MIB, SIB, RRC signaling or individual signaling to
each low-cost terminal.
[0316] Although the low-cost terminal communicates data and control
signals within a relatively small subband relative to the system
transmission bandwidth, it may obtain system transmission bandwidth
information and information on the number of CRS antenna ports for
exact RE mapping of transmitted/received signals. CRS
(cell-specific reference signal) is the reference signal (RS) that
the base station transmits to the terminal to allow the terminal to
reference in measuring downlink channel status or the base station
transmits to the terminal to support operations by the terminal,
such as channel estimation, upon transmission of downlink signals,
and downlink data channel and control channel are mapped to other
REs except the RE (resource element) where the CRS is mapped. The
mapping pattern of CRS is determined depending on the number of
transmit antennas of the base station and is defined as a logical
antenna port. The low-cost terminal may be aware of the system
transmission bandwidth information and the information on the
number of CRS antenna ports through PBCH decoding.
[0317] Generally, in the LTE system, DCI per terminal has the same
size if in the same DCI format. However, even if in the same DCI
format, the size of DCI for low-cost terminal may be different from
the size of DCI for normal terminal. That is, DCI for low-cost
terminal may be configured compact to fit the size of subband where
low-cost terminal operates. Accordingly, in case DCI for normal
terminal and DCI for low-cost terminal are mapped to time-frequency
resource of the same size, a relatively lower coding rate applies
to the DCI for low-cost terminal (that is, error correction by
channel coding is strongly reinforced), and thus, DCI for low-cost
terminal may enjoy relatively more benefit in reception capability.
Thus, the low-cost terminal assumes the DCI size determined
depending on the size of subband, not the system transmission
bandwidth, when performing DCI decoding. By contrast, the normal
terminal assumes the DCI size determined depending on the system
transmission bandwidth.
[0318] FIG. 19 is a concept view illustrating an example in which
DCI size is varied depending on the type of terminal according to
an embodiment of the present disclosure.
[0319] The DCI size may be determined to be different depending on
the type of terminal (i.e., low-cost terminal or normal terminal).
For normal terminal, DCI size 1906 is determined by DCI format 1902
or transmission bandwidth information 1904, and for low-cost
terminal, DCI size 1910 is determined by DCI format 1902 or subband
size 1908. The size 1908 of subband where the low-cost terminal
operates is operated to be smaller than the system bandwidth 1904.
Resultantly, even with the same DCI format, the DCI size 1910 of
low-cost terminal is smaller than the DCI size 1906 of normal
terminal.
[0320] FIG. 20 illustrates an example of a scheduling procedure by
a base station when a normal LTE terminal and a low-cost terminal
co-exist in the same system according to an embodiment of the
present disclosure.
[0321] The procedure of base station described in connection with
FIG. 18 is described in connection with FIG. 20.
[0322] In step 2000, the base station configures a subband where
the low-cost terminal operates within the system transmission
bandwidth and informs the low-cost terminal of that. The base
station may configure and operate a plurality of subbands, and may
notify the low-cost terminal of subband control information such as
the number and position of subbands through higher layer signaling,
such as MIB, SIB, or RRC signaling. Further, the base station may
inform the low-cost terminal of the subband where each low-cost
terminal operates through individual additional signaling.
[0323] In step 2002, when determining the scheduling for the
terminal, the base station may determine whether the scheduling is
for low-cost terminal or normal LTE terminal.
[0324] If the scheduling is for low-cost terminal, the base station
configures DCI for low-cost terminal by referring to DCI format or
subband size in step 2004. In step 2006, the base station transmits
the configured DCI for low-cost terminal to the low-cost terminal
through downlink control channel. The downlink control channel for
the low-cost terminal may be transmitted, mapped to the
time-frequency resource except the control channel region for
normal LTE terminal within the subband where the low-cost terminal
operates. The base station may configure and transmit downlink data
for the low-cost terminal depending on the scheduling information
indicated by the DCI.
[0325] If the scheduling is for normal LTE terminal, the base
station configures DCI for normal LTE terminal by referring to DCI
format or system transmission bandwidth in step 2008. Further in
step 2010, the base station transmits the configured DCI to the
normal LTE terminal through PDCCH or EPDCCH which is a downlink
control channel for normal LTE terminal. The base station may
configure and transmit downlink data for the normal LTE terminal
depending on the scheduling information indicated by the DCI. PDCCH
may be spread over the overall system transmission bandwidth 1802
during the control channel transmission period 1808 shown in FIG.
18 and may be mapped not overlapping for each terminal and may then
be transmitted.
[0326] FIG. 21 is a view illustrating a procedure of obtaining DCI
by a low-cost terminal operating according to an embodiment of the
present disclosure.
[0327] The procedure of the terminal exemplified in FIG. 18 is
described in connection with FIG. 21.
[0328] In step 2100, the low-cost terminal obtains subband
configuration information on the subband where the low-cost
terminal operates from the base station and identifies the subband
through which it performs transmission/reception operation with the
base station.
[0329] In step 2102, the low-cost terminal attempts to obtain DCI
through blind decoding on the downlink control channel for low-cost
terminal within the subband obtained in step 2100.
[0330] If the low-cost terminal succeeds in the blind decoding, the
low-cost terminal obtains detailed control information configuring
the DCI in step 2104. If the obtained control information is
downlink scheduling information, the low-cost terminal may receive
downlink data channel for low-cost terminal by the scheduling
information indicated by the DCI. If the obtained control
information is uplink scheduling information, the low-cost terminal
may transmit uplink data channel for low-cost terminal by the
scheduling information indicated by the DCI.
[0331] If the low-cost terminal fails in the blind decoding, it may
perform operation 2102 at the next time of blind decoding.
[0332] FIG. 22 is a concept view illustrating an example of
operating without explicitly configuring a subband where a low-cost
terminal operates in a system transmission bandwidth according to
an embodiment of the present disclosure.
[0333] Referring to FIG. 22, a method of operating a low-cost
terminal with a limited maximum processable bandwidth within the
system transmission bandwidth without explicitly configuring a
subband where the low-cost terminal operates is exemplified.
[0334] The low-cost terminal performs data or control signal
communication operation within a maximally processable bandwidth at
some moment. The size of the maximally processable bandwidth by the
low-cost terminal cannot be larger than the system transmission
bandwidth 2202, and is generally assumed as the minimum
transmission bandwidth supported by the LTE system, i.e., 1.4 MHz
(six consecutive PRBs). The base station, upon scheduling for the
low-cost terminal, should not allocate RBs exceeding the maximally
processable bandwidth of the low-cost terminal. If the low-cost
terminal is allocated RBs exceeding the maximally processable
bandwidth, the low-cost terminal determines that the scheduling
information is wrong and disregards it. Since control channels for
normal terminal are broadband transmitted over the system
transmission bandwidth 2202 in the control channel region 2208 of
each subframe, the low-cost terminal cannot receive the control
channels for normal terminals. Control channels and data channels
for low-cost terminal may be transmitted, mapped to the remaining
region except the control channel region 2208. Although FIG. 22
primarily illustrates for downlink, it would not harm the
representation of overall concept for uplink. However, uplink does
not include a separate control channel region like the control
channel region 2208.
[0335] In the instant embodiment, no separate subband is previously
configured for low-cost terminal, and (in case the limitations for
RB allocation are met), the freedom of resource utilization is
advantageously larger than that in the embodiment described in
connection with FIG. 18.
[0336] The low-cost terminal, while proceeding with initial access,
may receive the PSS/SSS and PBCH transmitted, mapped with the
middle 1.4 MHz band (e.g., the band corresponding to 2210 of FIG.
22) in the system bandwidth. The low-cost terminal may detect the
PSS/SSS to obtain time-frequency sync and cell ID and obtain
necessary system information, MIB, through PBCH decoding. After the
initial access is complete, the low-cost terminal may also perform
time-frequency syncing, or to obtain MIB, it may perform PSS/SSS
detection and PBCH decoding.
[0337] As described in connection with the embodiment of FIG. 18,
although the low-cost terminal communicates data and control
signals within a relatively small bandwidth relative to the system
transmission bandwidth, it may obtain system transmission bandwidth
information and information on the number of CRS antenna ports for
exact RE mapping of transmitted/received signals.
[0338] Unlike in FIG. 18, DCI size for low-cost terminal and DCI
size for normal terminal if they are in the same DCI format are
kept the same in FIG. 22. That is, the base station applies the
consistent DCI configuration method regardless of the type of
terminal (that is, regardless of whether the terminal is normal
terminal or low-cost terminal), leading to minimized changes to the
implementation of legacy base station and reduced complexity of
base station implementation. The low-cost terminal assumes DCI size
determined system transmission bandwidth, but not the maximum
processable bandwidth of low-cost terminal when performing DCI
decoding.
[0339] The resource information in the frequency domain which is
mapped with downlink data or uplink data of the low-cost terminal
may be provided from the base station to the low-cost terminal
through `resource block assignment` information 2216 configuring
the DCI.
[0340] Referring to FIG. 22, the base station maps and transmits
the DCI for the low-cost terminal in the DCI region 2210 of
subframe i 2204 and maps and transmits the downlink data for the
low-cost terminal in the PDSCH region 2212 of subframe i+k 2206
(k>0). The frequency band size of the DCI region 2210 and the
PDSCH region 2212 cannot exceed the maximum processable bandwidth
of the low-cost terminal.
[0341] The position of the PDSCH region 2212 which is mapped to the
DCI region 2210 and transmitted may be indicated by `resource block
assignment` information 2216 transmitted through the DCI region
2210. The information on the DCI region 2210 which is in the
frequency domain where the DCI is mapped and transmitted may be
previously known to the low-cost terminal by the base station. k is
determined considering the time taken for the low-cost terminal to
change frequencies, and it may be a fixed value or may be known to
the terminal by the base station through separate signaling. In
case k=0, that is, in case the DCI and downlink data (PDSCH) are
mapped to the same subframe and transmitted, the bandwidth sum of
the DCI region 2210 and the PDSCH region 2212 cannot exceed the
maximum processable bandwidth of the low-cost terminal.
[0342] FIG. 23 is a concept view illustrating a method for
determining a DCI size according to an embodiment of the present
disclosure.
[0343] Based on the embodiment exemplified in FIG. 22, in FIG. 23,
for both normal terminal and low-cost terminal, DCI size 2306 is
determined by DCI format 2302 and transmission bandwidth 2304.
Resultantly, if in the same DCI format, DCI size for low-cost
terminal and DCI size for normal terminal are the same.
[0344] FIG. 24 illustrates an example of a scheduling procedure by
a base station when a normal LTE terminal and a low-cost terminal
co-exist in the same system according to an embodiment of the
present disclosure.
[0345] The procedure of base station described as an example in
connection with FIG. 22 is described in connection with FIG.
24.
[0346] In step 2400, the base station configures a subband where
the DCI of the low-cost terminal is mapped and transmitted in the
system transmission bandwidth of the base station and informs the
low-cost terminal of the subband. The subband control information
such as the position of the configured may be known to the low-cost
terminal through higher layer signaling, such as MIB, SIB, or RRC
signaling. Further, the base station may individually provide the
subband control information to the low-cost terminal through
additional signaling.
[0347] In step 2402, when determining the scheduling for the
terminal, the base station may determine whether the scheduling to
be determined is for low-cost terminal or normal LTE terminal.
[0348] If the scheduling is for low-cost terminal, the base station
configures DCI for low-cost terminal by referring to DCI format or
transmission bandwidth in step 2404. In step 2406, the base station
may map the configured DCI of the low-cost terminal to the
time-frequency resources except the control channel region for the
normal LTE terminal in the subband configured in step 2400 and
transmit to the low-cost terminal. The base station may configure
downlink data (PDSCH) for the low-cost terminal according to the
scheduling information (i.e., the resource block allocation
information) informed by the DCI and transmit the same.
[0349] If the scheduling is for normal LTE terminal, the base
station configures DCI for the normal LTE terminal by referring to
DCI format or transmission bandwidth in step 2408. In step 2410,
the base station may transmit the configured DCI to the normal LTE
terminal through PDCCH or EPDCCH which is a downlink control
channel for normal LTE terminal. The base station may configure and
transmit downlink data for the normal LTE terminal depending on the
scheduling information known by the DCI. The PDCCH may be spread
over the overall system transmission bandwidth 2202 during the
control channel region 2208 shown in FIG. 22 and may be mapped
without overlapping for each terminal and may then be
transmitted.
[0350] FIG. 25 is a view illustrating a procedure of obtaining DCI
by a low-cost terminal operating according to an embodiment of the
present disclosure.
[0351] The procedure of the terminal exemplified in FIG. 22 is
described in connection with FIG. 25.
[0352] In step 2500, the low-cost terminal obtains subband
configuration information on the subband which is mapped with the
DCI for low-cost terminal and transmitted from the base station and
identifies the subband through which it should receive the DCI from
the base station.
[0353] In step 2502, the low-cost terminal attempts to obtain DCI
through blind decoding on the downlink control channel for low-cost
terminal within the subband obtained in step 2500.
[0354] If the low-cost terminal succeeds in the blind decoding, the
low-cost terminal obtains detailed control information configuring
the DCI in step 2504. If the obtained control information is
downlink scheduling information, the low-cost terminal may receive
downlink data channel for low-cost terminal by the scheduling
information indicated by the DCI. If the obtained control
information is uplink scheduling information, the low-cost terminal
may transmit uplink data channel for low-cost terminal by the
scheduling information indicated by the DCI.
[0355] If the low-cost terminal fails in the blind decoding, it may
perform operation 2502 at the next time of blind decoding.
[0356] FIG. 26 is a concept view illustrating an example of
previously configuring and dynamically varying a subband where a
low-cost terminal operates in a system transmission bandwidth
according to an embodiment of the present disclosure.
[0357] Described with reference to FIG. 26 is an exemplary method
for previously configuring and operating subbands where the
low-cost terminal operates in the system transmission bandwidth
while dynamically changing the subbands where the low-cost terminal
operates.
[0358] The size of subband where the low-cost terminal operates
cannot be larger than the system transmission bandwidth 2602, and
is generally assumed as the minimum transmission bandwidth
supported by the LTE system, i.e., 1.4 MHz (six consecutive PRBs).
The base station may simultaneously serve a number of low-cost
terminals by configuring/operating a plurality of subbands. FIG. 26
illustrates an example in which three subbands A, B, and C 1010,
1012, and 1014 are configured in the system transmission bandwidth
2602. The low-cost terminal may perform data or control signal
communication operation through one subband of the subbands at some
moment.
[0359] In this embodiment, the base station may designate one of
the subbands, maps it with DCI for low-cost terminal and transmits,
and dynamically indicate the subband mapped with the data for
low-cost terminal by including a subband indicator 2616 in the DCI.
The `subband indicator` may be included in, e.g., the resource
block assignment information included in the DCI. The subband
mapped with the DCI may be previously known to the low-cost
terminal by the base station, leading to reduced complexity of DCI
decoding of low-cost terminal. The `subband indicator` 2616 is
information indicating the subband where the data of the low-cost
terminal is mapped and transmitted among the subbands configured
for use by the low-cost terminal. The subband indicator may also be
called a `subband index,` narrowband indicator,' or `narrowband
index.` The `subband indicator` 2616 may also be configured in
various methods as follows.
[0360] Method 1. adding to existing DCI as additional control
information.
[0361] Method 2. switching some control information of existing DCI
into `subband indicator.` For example, the carrier indicator field
(CIF) defined for carrier aggregation (CA) may be switched and used
as a subband indicator for low-cost terminal. (this is why the CA
does not apply to low-cost terminals.)
[0362] Method 3. combining `subband indicators` for several
terminals to configure group control information. In this case,
unlike in methods 1 and 2, DCI for scheduling is required
separately from the `subband indicator.`
[0363] The information on the frequency domain 2612 where the
`subband indicator` is mapped and transmitted is previously
designated and known to the low-cost terminal by the base station.
Referring to FIG. 26, the base station maps and transmits the
`subframe indicator` for the low-cost terminal in subframe B 2612
of subframe i 2604 and maps and transmits the downlink data for the
low-cost terminal in subband A 2610 of subframe i+k 2606 (k>0).
k is determined considering the time taken for the low-cost
terminal to change frequencies, and it may be a fixed value or may
be known to the terminal by the base station through separate
signaling. In case k=0, that is, in case the `subband indicator`
and downlink data are mapped and transmitted in the same subframe,
the subband where the subband indicator is delivered is the same as
the subband where the downlink data is delivered. After completing
the reception of downlink data, the low-cost terminal may take the
following approaches.
[0364] Method A. The low-cost terminal goes back to the subband
where the `subband indicator` is mapped and transmitted (i.e.,
changes frequencies) to attempt to detect a next `subband
indicator.`
[0365] Method B. The low-cost terminal, without changing subbands,
prepares to receive next downlink data or transmit uplink data
within the subband indicated by the `subband indicator.`
[0366] Regardless of method A or B, the low-cost terminal may
obtain time-frequency sync or change frequency into the center
frequency of the system transmission bandwidth to obtain MIB to
detect PSS/SSS and decode PBCH.
[0367] Although the low-cost terminal communicates data and control
signals within a relatively small bandwidth relative to the system
transmission bandwidth, it may obtain system transmission bandwidth
information and information on the number of CRS antenna ports for
exact RE mapping of transmitted/received signals.
[0368] The scheduling procedure of the base station according to
FIG. 26 may be described with reference to FIG. 20. However,
according to the embodiment shown in FIG. 26, upon configuring DCI
for low-cost terminal in step 2004 of FIG. 20, an additional
subband indicator may be configured by method 1 or method 2 or
separate group control information obtained by combining subband
indicators for several terminals may be configured by method 3.
[0369] The procedure of obtaining the DCI by the low-cost terminal
according to FIG. 26 may be described with reference to FIG. 21.
However, according to the embodiment shown in FIG. 26, in step 2102
or previous steps of FIG. 21, the low-cost terminal may
additionally perform the procedure of receiving the `subband
indicator.`
[0370] FIG. 27 is a concept view illustrating an example of a
method for indicating a subband in an FDD system according to an
embodiment of the present disclosure.
[0371] In the frequency division duplex (FDD) system where uplink
and downlink are separately operated in the frequency domain, the
interval in center frequency between uplink frequency and downlink
frequency (TX-RX carrier centre frequency separation) is defined
for each frequency band where LTE system operates. Described with
respect to FIG. 27 is described, as an example, a scheme of
utilizing the center frequency interval (subband Tx-Rx centre
frequency separation) between uplink subband and downlink subband
in case the uplink subband and downlink subband of the low-cost
terminal are each operated within each of uplink and downlink
transmission bandwidths.
[0372] FIG. 27 illustrates the interval between uplink center
frequency (UL center frequency) 2708 and downlink center frequency
(DL center frequency) 2710, i.e., `TX-RX carrier centre frequency
separation` 2700 between the uplink frequency and the downlink
frequency, uplink bandwidth (BW.sub.UL) 2704, downlink bandwidth
(BW.sub.DL) 2706, low-cost terminal's uplink subband bandwidth
(BW.sub.UL,subband) 2712, low-cost terminal's downlink subband
bandwidth (BW.sub.