Note: Descriptions are shown in the official language in which they were submitted.
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[DESCRIPTION]
[Invention Title]
METHOD AND DEVICE FOR RECEIVING DOWNLINK SIGNAL
[Technical Field]
The present invention relates to a radio communication
system, and more particularly, to a method and device for
receiving a downlink signal.
[Background Art]
Radio communication systems have been diversified in
order to provide various types of communication services such
as voice or data service. In general, a radio communication
system is a multiple access system capable of sharing
available system resources (bandwidth, transmit power or the
like) so as to support communication with multiple users.
Examples of the multiple access system include a Code
Division Multiple Access (CDMA) system, a Frequency Division
Multiple Access (FDMA) system, a Time Division Multiple
Access (TDMA) system, an Orthogonal Frequency Division
Multiple Access (OFDMA) system, a Single Carrier Frequency
Division Multiple Access (SC-FDMA) system, and the like.
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[Summary]
An object of some aspects of the present invention is
to provide a method and device for efficiently utilizing
downlink resources in a radio communication system.
The technical problems solved by embodiments of the
present invention are not limited to the above technical
problems .and other technical problems which are not described
herein will become apparent to those skilled in the art from
the following description.
According to one aspect, there is provided a method
for receiving a Relay Physical Downlink Control Channel (R-
PDCCH) signal at a relay in a wireless communication system,
the method comprising: receiving, by the relay, first control
information for downlink scheduling in a 1st slot of a set of
resource block (RB) pair, wherein the first control information
includes allocation information on one or more resource units;
monitoring, by the relay, second control information for uplink
scheduling in a 2nd slot of the set of RB pair; and performing,
by the relay, procedures for receiving data corresponding to
the first control information, wherein if the one or more
resource units overlap with a resource block pair where the
first control information is detected, the procedures for
receiving data are performed under an assumption that the data
exists on the 2'd slot of the resource block pair.
According to another aspect, there is provided a
relay used for a wireless communication system, the apparatus
comprising: a radio frequency unit; and a processor, wherein
the processor is configured: to receive first control
information for downlink scheduling in a 1st slot of a set of
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resource block (RB) pair, wherein the first control information .
includes allocation information on one or more resource units,
to monitor second control information for uplink scheduling in
a 2nd slot of the set of RB pair, and to perform procedures for
receiving data corresponding to the first control information,
wherein if the one or more resource units overlap with a
resource block pair where the first control information is
detected, the procedures for receiving data are performed under
an assumption that the data exists on the 2nd slot of the
resource block pair.
According to still another aspect of the present
invention, there is provided a method for receiving downlink
signal in a wireless communication system, the method
comprising: receiving first control information for downlink
scheduling in the first slot of a resource block (RB) pair,
wherein the first control information includes allocation
information on one or more resource units; receiving data at
the second slot of the RB pair when the allocation information
on a resource unit including the resource block pair with the
first control information has a first value; and attempting to
detect second control information for uplink scheduling at the
second slot of the RB pair when the allocation information on
the resource unit including the resource block pair with the
first control information has a second value.
According to other aspect of the present invention,
there is provided an user equipment configured to receive a
downlink signal in a wireless communication system, the
apparatus comprising: a radio frequency unit; and a processor,
wherein the processor is configured to receive first control
information for downlink scheduling in the first slot of a
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resource block (RB) pair, wherein the first control information
includes allocation information on one or more resource units,
and to receive data at the second slot of the RB pair when the
allocation information on a resource unit including the
resource block pair with the first control information has a
first value, and to attempt to detect second control
information for uplink scheduling at the second slot of the RB
pair when the allocation information on the resource unit
including the resource block pair with the first control
information has a second value.
Preferably, the resource unit allocation information
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includes bitmap for resource allocation, each bit indicating
resource allocation of a corresponding RB or a RBG(Resource
Block Group).
Preferably, the second control information exists on
the second slot of the RB pair when the allocation
information on the resource unit including the resource
block pair with the first control information has the second
value.
Preferably, the first value is 1, and the second value
is 0.
Preferably, the attempting to detect the second control
information is performed under an assumption that an
aggregation level of the second control information is less
than an aggregation level of the first control information.
Preferably, the attempting to detect the second control
information is performed only on resource overlapped between
pre-configured search space for the second control
information and the resource unit for which the allocation
information has the second value.
Preferably, further comprising: receiving information
related to arrangement of the second control information on
resources of the second slot via an upper layer signaling.
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According to a communication system of an embodiment of the present
invention, it is possible to efficiently utilize downlink
resources in a radio communication system.
The effects of embodiments of the present invention are not limited to
the above-described effects and other effects which are not
described herein will become apparent to those skilled in
=
the art from the following description.
=
[Description of Drawings]
The accompanying drawings, which are included to provide
a further understanding of the invention and are incorporated
in and constitute a part of this application, illustrate
embodiment(s) of the invention and together with the
description serve to explain the principle of the invention.
FIG. 1 is a diagram showing the structure of a radio
frame used in a 3rd Generation Partnership Project (3GPP)
system.
FIG. 2 is a diagram showing a resource grid of a
downlink slot.
FIG. 3 is a diagram showing the structure of a downlink
subframe.
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FIG. 4 is a diagram showing the structure of an uplink
subframe used in a system.
FIG. 5 is a diagram showing a process of transmitting a
signal using a multi-antenna scheme.
FIG. 6 is a diagram showing the structure of a
demodulation reference signal (DM RS).
FIG. 7 is a diagram showing a method of mapping a
virtual resource block (VRB) to a physical resource block
(PRB).
FIGs. 8 to 10 are diagrams showing Type 0 resource
allocation (RA), Type 1 RA and Type 2 RA, respectively.
FIG. 11 is a diagram showing a radio communication
system including a relay.
FIG. 12 is a diagram showing backhaul communication
using a multimedia broadcast over a single frequency network
(MBSFN) subframe.
FIGs. 13 to 14 are diagrams showing arbitrary division
of frequency-time resources.
FIGs. 15 to 17 are diagrams showing examples of placing
and demodulating an R-PDCCH/(R-)PDSCH.
FIGs. 18 to 19 are diagrams showing examples of dividing
an RB pair into a plurality of RE groups.
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FIG. 20 to 23 are diagrams showing other examples of
placing and demodulating R-PDCCHs/(R-)PDSCHs.
FIG. 24 is a diagram showing the case of transmitting UL
grant only in the case in which a DL RA bit is set to 0.
FIGs. 25 to 27 are diagrams showing a method of
indicating a resource use state of a second slot.
FIG. 28 is a diagram showing a downlink control
information (DCI) format.
FIGs. 29 to 42 are diagrams showing various methods of
indicating a resource use state of a second slot.
FIGs. 43 to 46 are diagrams showing a method of ordering
indexes of relay physical downlink control channels (R-
PDCCHs) and a resource allocation example thereof.
FIG. 47 is a diagram showing a base station, a relay
node and a user equipment (UE).
[Best Mode]
The configuration, the operation and the other features
of the embodiments of the present invention will be described
with reference to the accompanying drawings. The following
embodiments of the present invention may be utilized in
various radio access systems such as a Code Division Multiple
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Access (CDMA) system, a Frequency Division Multiple Access
(FDMA) system, a Time Division Multiple Access (TDMA) system,
an Orthogonal Frequency Division Multiple Access (OFDMA)
system, or a Single Carrier Frequency Division Multiple
Access (SC-FDMA) system. The CDMA system may be implemented
as radio technology such as Universal Terrestrial Radio
Access (UTRA) or CDMA2000.
The TDMA system may be
implemented as radio technology such as Global System for
Mobile communications (GSM)/General Packet Radio Service
(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE).
The
OFDMA system may be implemented as radio technology such as
IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20 or E-
UTRA (Evolved UTRA).
The UTRA system is part of the
Universal Mobile Telecommunications System (UMTS). A 3rd
Generation Partnership Project Long Term Evolution (3GPP LTE)
communication system is part of the E-UMTS (Evolved UMTS)
which employs the E-UTRA.
The LTE-Advanced (LTE-A) is an
evolved version of the 3GPP LTE.
The following embodiments focus on the 3GPP system to
which the technical features of the present invention are
applied, but the present invention is not limited thereto.
FIG. 1 is a diagram showing the structure of a radio
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frame of a 3rd Generation Partnership Project (3GPP) system.
Referring to FIG. 1, the radio frame has a length of 10
ms (307200=Ts) and includes 10 subframes with the same size.
Each of the subframes has a length of 1 ms and includes two
slots.
Each of the slots has a length of 0.5 ms (15360=Ts).
Ts denotes a sampling time, and is represented by
Ts=1/(15kHzx2048)=3.2552x10-8 (about 33 ns).
Each slot
includes a plurality of OFDM symbols or SC-FDMA symbols in a
time domain, and includes a plurality of resource blocks
(RBs) in a frequency domain. In
the LTE system, one RB
includes 12 subcarriersx7(6) OFDM symbols. A
Transmission
Time Interval (TTI) which is a unit time for transmission of
data may be determined in units of one or more subframes.
The structure of the radio frame is only exemplary and the
number of subframes, the number of subslots, or the number of
OFDM/SC-FDMA symbols may be variously changed in the radio
frame.
FIG. 2 is a diagram showing a resource grid of a
downlink slot.
Referring to FIG. 2, a downlink slot includes a
plurality of OFDM symbols (e.g., seven) in a time domain and
NDLRB RBs in a frequency domain.
Since each RB includes 12
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subcarriers, the downlink slot includes NDLRBx12 subcarriers in
the frequency domain.
Although FIG. 2 shows the case in
which the downlink slot includes seven OFDM symbols and the
RB includes 12 subcarriers, the present invention is not
limited thereto. For
example, the number of OFDM symbols
included in the downlink slot may be changed according to the
length of a cyclic prefix (CP). Each element of the resource
grid is referred to as a resource element (RE). The RE is a
minimum time/frequency resources defined in a physical
channel and is indicated by one OFDM symbol index and one
NDL
subcarrier index. One RB includes NDLsbxNRBsc REs . symb
denotes the number of OFDM symbols in the downlink slot and
NRBs, denotes the number of subcarriers included in the RB.
The number NDLRB of RBs included in the downlink slot depends
on a downlink transmission bandwidth set in a cell.
The downlink slot structure shown in FIG. 2 is equally
applied to an uplink slot structure. At this
time, the
uplink slot structure includes SC-FDMA symbols, instead of
the OFDM symbols.
FIG. 3 is a diagram showing the structure of a downlink
subframe in a 3GPP system.
Referring to FIG. 3, one or more OFDM symbols located in
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a front portion of the subframe are used as a control region
and the remaining OFDM symbols are used as a data region.
The size of the control region may be independently set per
subframe. The control region is used to transmit scheduling
information and layer 1/layer 2 (Ll/L2) control information.
The data region is used to transmit traffic. The
control
channel includes a Physical Control Format Indicator Channel
(PCFICH), a Physical Hybrid automatic repeat request (ARQ)
Indicator Channel (PHICH), a Physical Downlink Control
Channel (PDCCH), etc. The
traffic channel includes a
Physical Downlink Shared Channel (PDSCH).
The PDCCH may inform a UE or a UE group of resource
allocation information about resource allocation of a paging
channel (PCH) or a Downlink Shared Channel (DL-SCH) which is
a transport channel, uplink scheduling grant, HARQ
information, etc. The PCH
and the DL-SCH are transmitted
through a PDSCH. Accordingly, an eNode B and a UE generally
transmit and receive data through a PDSCH except for specific
control information or specific service data. Control
information transmitted through a PDCCH is referred to
downlink control information (DCI). The DCI indicates uplink
resource allocation information, downlink resource allocation
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information and an uplink transmit power control command for
arbitrary UE groups. The eNode
B decides a PDCCH format
according to DCI to be sent to the UE and attaches a cyclic
redundancy check (CRC) to control information. The CRC
is
masked with a unique identifier (e.g., a Radio Network
Temporary Identifier (RNTI)) according to an owner or usage
of the PDCCH.
FIG. 4 is a diagram showing the structure of an uplink
subframe used in a 3GPP system.
Referring to FIG. 4, a subframe 500 having a length of 1
ms which is a basic unit of LTE uplink transmission includes
two slots 501 each having a length of 0.5 ms. In the case of
a length of a normal Cyclic Prefix (CP), each slot includes
seven symbols 502 and one symbol corresponds to one Single
carrier-Frequency Division Multiple Access (SC-FDMA) symbol.
An RB 503 is a resource allocation unit corresponding to 12
subcarriers in a frequency domain and one slot in a time
domain. The
structure of the uplink subframe of the LTE
system is roughly divided into a data region 504 and a
control region 505. The data region refers to communication
resources used for data transmission, such as voice or
packets transmitted to each UE, and includes a physical
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uplink shared channel (PUSCH). The control region refers to
communication resources used to transmit an uplink control
signal such as a downlink channel quality report from each UE,
reception ACK/NACK of a downlink signal, an uplink scheduling
request or the like, and includes a Physical Uplink Control
Channel (PUCCH). A
sounding reference signal (SRS) is
transmitted through a last SC-FDMA symbol of one subframe on
a time axis.
SRSs of several UEs transmitted through the
last SC-FDMA of the same subframe are distinguished according
to a frequency position/sequence.
FIG. 5 is a diagram showing a process of transmitting a
signal using a multi-antenna scheme.
Referring to FIG. 5, codewords are scrambled by
scrambling modules 301. The codeword includes an encoded bit
stream corresponding to a transport block.
The scrambled
codewords are input to modulation mappers 302 and are
modulated into complex symbols using a Binary Phase Shift
Keying (BPSK), Quadrature Phase Shift Keying (QPSK) or 16-
Quadrature amplitude modulation (QAM) scheme according to the
kind of the transmitted signal and/or the channel state.
Thereafter, the modulated complex symbols are mapped to one
or more layers by a layer mapper 303.
Codeword-to-layer
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mapping may be changed according to a transmission scheme.
The layer-mapped signals may be multiplied by a predetermined
precoding matrix selected according to a channel state by a
precoding module 304 to be allocated to transmission antennas.
The signals to be transmitted by the antennas may be mapped
to time-frequency resource elements to be used for
transmission by the resource element mappers 305, and
transmitted via OFDMA signal generator 306 and antennas.
FIG. 6 is a diagram showing the structure of a
demodulation reference signal (DM RS).
The DM RS is a UE-
specific RS used to demodulate a signal of each layer when a
signal is transmitted using multiple antennas. The DM RS is
used to demodulate a PDSCH and an R-PDSCH. Since an LTE-A
system includes a maximum of eight transmission antennas, a
maximum of eight layers and DM RSs therefor are necessary.
For convenience, DM RSs for layers 0 to 7 are referred to as
DM RSs (layers) 0 to 7.
Referring to FIG. 6, the DM RSs for two or more layers
share the same RE and are multiplexed according to a code
division multiplexing (CDM) scheme.
More specifically, DM
RSs for layers are spread using spreading codes (e.g., Walsh
codes or orthogonal codes such as DFT codes) and are
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multiplexed on the same RE. For example, DM RSs for layers 0
and 1 share the same RE and are, for example, spread on two
REs of OFDM symbols 12 and 13 at a subcarrier 1 (k=1) using
orthogonal coding.
That is, in each slot, the DM RSs for
layers 0 and 1 are spread along a time axis using codes
having a spreading factor (SF) of 2 and are multiplexed on
the same REs. For example, the DM RS for the layer 0 may be
spread using [+1 +11 and the MD RS for the layer 1 may be
spread using [+1 -1]. Similarly, the DM RSs for layers 2 and
3 are spread on the RE using different orthogonal codes. The
DM RSs for layers 4, 5, 6 and 7 are spread on the REs
occupied by the DM RSs for layers 0, 1, 2 and 3 using codes
orthogonal to the layers 0, 1, 2 and 3. Codes having SF=2 is
used for the DM RS if four or less layers are used and codes
having SF=4 is used for the DM RS if five or more layers are
used.
In LTE-A, antenna ports for the DM RS is {7, 8, ...,
n+6} (n being the number of layers).
Table 1 shows a spread sequence for antenna ports 7 to
14 defined in LTE-A.
Table 1
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Antennaportp [IVA /71;p(I) Tp(2)/TpOd
7 ki +1 +1 +11
8 ki -1 +1 A
9 [+i +1 +1 +1]
lo ki -1 +1 -1]
11 [+i +1 -1 -1]
12 pi -1 +1 _IA
13 [+l -1 -1 +1]
14 pi +1 +1 -I]
Referring to Table 1, orthogonal code for antenna ports
7 to 10 has a structure in which orthogonal code having a
length of 2 is repeated. As a result, orthogonal code having
a length of 2 is used at a slot level if four or less layers
are used and orthogonal code having a length of 4 is used at
a subframe level if 5 or more layers are used.
Hereinafter, resource block mapping will be described.
A physical resource block (PRB) and a virtual resource block
(VRB) are defined. The PRB is equal to that shown in FIG. 2.
That is, the PRB is defined as 4,L0 contiguous OFDM symbols
in a time domain and AT contiguous subcarriers in a
frequency domain. PRBs are numbered from 0 to Na-1 in the
frequency domain. A relationship between a PRB number npu
and an RE (k, 1) in a slot is shown in Equation 1.
Equation 1
k
nPRB =[ RNB
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where, k denotes a subcarrier index and Nr denotes the
number of subcarriers included in one RB.
The VRB has the same size as the PRB. A localized VRB
(LVRB) of a localized type and a distributed VRB (DVRB) of a
distributed type are defined. Regardless of the type of the
VRB, a pair of RBs is allocated over two slots by a single
VRB number nvu.
FIG. 7 is a diagram showing a method of mapping a
virtual resource block (VRB) to a physical resource block
(PRB).
Referring to Fig. 7, since an LVRB is directly mapped to
a PRB, a VRB number nvu equally corresponds to a PRN number
nPRB(nPRB nVRB ) = The VRB
is numbered from 0 to AL-1 and
N1413.413- . The DVRB
is mapped to the PRB after being
interleaved. More
specifically, the DVRB may be mapped to
the PRB as shown in Table 2. Table 2 shows an RB gap value.
Table 2
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Gap ( N gap)
System BW (iv RDBL )
1"',
Gap ( Ngap,i) 2"d Gap ( Ngap,2)
6-10 [-NRBDL /21 N/A
11 4 N/A
12-19 8 N/A
20-26 12 N/A
27-44 18 N/A
45-49 27 N/A
60-63 27 9
64-79 32 16
80-110 48 16
Ngap denotes a frequency gap (e . g. , PRB unit) when VRBs
having the same number are mapped to PRBs of a first slot and
6<NDL <49
a second slot. In case of RB , only
one gap value is
defined ( NPaP = NPaP'I ) . In case
of 50N õDL 110 , two gap values
NPP.' and N83P'2 are defined. NgaP
NPaP.1 or NgaP = NgaP'2 is signaled
through downlink scheduling. DVRBs are
numbered from 0
NvD,BL =N1 = 2 = min(Ngap, - N gap)
to NB -1 , iswith respect to
VRB VRB,gaP2 -NRBDL gaP
/ 2N I 2N
N gap = N gaP'1 and is
Iwith respect to
Ngap = Ngap,2 min (A, B) denotes the smaller of A or B.
KT DL
Contiguous VRB VRB numbers configure a unit for VRB
D
number interleaving, is IV'TvRL 1'
B = Ni)R-13 in case of NPaP = N"P'l , and is
/V-vDRBL = 2Ngap
in case of NaP = NPaP'2 VRB number interleaving of each
interleaving unit may be performed using four columns and N ow
rows. Air w
NvDRLB "P)]. P and P denotes the size of a Resource
Block Group (RBG) . The RBG is defined by P contiguous RBs .
The VRB number is written in a matrix on a row-by-row basis
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and is read in a column-by-column basis. Nnun null values are
inserted into last Nnull / 2
rows of second and fourth columns
and Nnull = 4Nrow ¨ 1\2V')L
AB . The null value is ignored upon reading.
Hereinafter, resource allocation defined in LTE will be
described. FIGs. 8
to 10 are diagrams showing control
information formats for Type 0 resource allocation (RA), Type
1 RA and Type 2 RA and resource allocation examples thereof,
respectively.
A user equipment (UE) interprets a resource allocation
field based on a detected PDCCH DCI format. The
resource
allocation field in each PDCCH includes two parts: a resource
allocation header field and actual resource block allocation
information. PDCCH DCI
formats 1, 2 and 2A for Type 0 and
Type 1 RA have the same format and are distinguished via a
single bit resource allocation header field present according
to a downlink system bandwidth. More specifically, Type 0 RA
is indicated by 0 and Type 1 RA is indicated by 1. While
PDCCH DCI formats 1, 2 and 2A are used for Type 0 or Type 1
RA, PDCCH DCI formats 1A, lb, 1C and 1D are used for Type 2
RA. The PDCCH DCI format having Type 2 RA does not have a
resource allocation header field.
Referring to FIG. 8, in Type 0 RA, resource block
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allocation information includes a bitmap indicating an RBG
allocated to a UE. The RBG is a set of contiguous PRBs . The
size P of the RBG depends on a system bandwidth as shown in
Table 3.
Table 3
System Bandwidth RBG Size
(P)
510 1
11-26 2
27-63 3
64-110 4
In a downlink system bandwidth having NR , the total
number NRBG of RBGs is NRBG /Pi , the
size of [Nlia //)] RBGs
is P, and the size of one RBG is - P =[Na
/ Pi in case of
N: mod P > 0 . Mod
denotes a modulo operation, 11 denotes a
ceiling function, and Li denotes a flooring function. The
size of a bitmap is NRBG and each bit corresponds to one RBG.
All RBGs are indexed by 0 to NRBG - 1 in a frequency increase
direction and RBG 0 to RBG ATRBG -1 are mapped from a most
significant bit (MSB) to a least significant bit (LSB) of a
bitmap.
Referring to FIG. 9, in Type 1 RA, resource block
allocation information having the size of NRBG informs a
scheduled UE of resources in an RBG subset in PRB units. The
RBG subset p ( ) starts
from an RBG p and includes
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every P-th RBG. The resource block allocation information
includes three fields. A first field has Flog2(P)1 bits and
indicates an RBG subset selected from among P RBG subsets. A
second field has 1 bit and indicates resource allocation span
shift within a subset. Shift is triggered if a bit value is
1 and is not triggered if a bit value is 0. A third field
includes a bitmap and each bit indicates one PRB within a
selected RBG set. The size of a bitmap part used to indicate
a PRB within the selected RBG subset is 4El and is defined
by Equation 2.
Equation 2
6
TypEi = [Na / - Flog2(P)1 -1
An addressable PRB number in the selected RBG subset may
start from an offset 40,41(p) from a smallest PRB number within
the selected RBG subset and may be mapped to a MSB of a
bitmap. The offset is represented by the number of PRBs and
is applied within the selected RBG subset. If the bit value
within a second field for resource allocation span shift is
set to 0, an offset for an RBG subset p is Asmt(p)=0. In the
other case, an offset for an RBG subset p is
Ashift(P) = NRRB3G subset (p) NRBTYPE I NRBRBG sub ) set (p.
denotes the number of PRBs
within the RBG subset p and may be obtained by Equation 3.
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Equation 3
1N: -11 [N: -I]
mod P
p 2
NDL -1
NRRir subset (p) RB p N RDBL 1)modP +1 ____ ,p= NRDBL modP
p2
NRBDL _1
.p>[1\1: -limodP
= P
[ _______________ D 2
Referring to FIG. 10, in Type 2 RA, resource block
allocation information indicates an LVRB or DVRB set
contiguously allocated to a scheduled UE. If resource
allocation is signaled in PDCCH DCI format 1A, 1B or 1C, a 1-
bit flag indicates whether an LVRB or DVRB is allocated (e.g.,
0 denotes LVRB allocation and 1 denotes DVRB allocation). In
contrast, if resource allocation is signaled in PDCCH DCI
format 1C, only DVRB is always allocated. A Type 2 RA field
includes a resource indication value (RIV) and the RIV
corresponds to a start resource block RBõõ, and a length. The
length denotes the number of virtually and contiguously
allocated resource blocks.
FIG. 11 is a diagram showing a communication system
including a relay (or a relay node (RN)). The relay is
installed in a shadow area so as to extend a service area of
a base station and to improve a service. Referring to FIG.
11, a radio communication system includes a base station (BS),
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a relay and a UE. The UE
performs communication with the
base station or the relay. For
convenience, a UE which
performs communication with the base station is referred to
as a macro UE and a UE which performs communication with the
relay is referred to as a relay UE. A
communication link
between the base station and the macro UE is referred to as a
macro access link and a communication link between the relay
and the relay UE is referred to as a relay access link. In
addition, a communication link between the base station and
the relay is referred to as a backhaul link.
The relay may be divided into an Li (layer 1) relay, an
L2 (layer 2) relay and an L3 (layer 3) relay depending on how
many functions are performed in multi-hop transmission.
These relays will be briefly described. The Ll
relay
functions as a general repeater, amplifies a signal from a
BS/UE and transmits the amplified signal to a UE/BS. Since
the relay does not perform decoding, transmission delay is
short, but a signal and noise cannot be distinguished and
thus noise may be also amplified. In order to overcome this
problem, an advanced repeater or a smart repeater having a UL
power control function or a self-interference cancellation
function may be used. The operation of the L2 relay may be
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represented by decode-and-forward and user plane traffic may
be transmitted by the L2 relay. Noise is not amplified, but
delay is increased due to decoding. The L3
relay is also
referred to as self-backhauling and IP packets may be
transmitted by the L3 relay. The L3
relay has a radio
resource control functions as a small base station.
The Ll and L2 relay is a part of a donor cell covered by
a BS. If the
relay is a part of the donor cell, since the
relay cannot control a cell thereof and UEs of the cell, the
relay cannot have a cell ID thereof. However, the relay may
have a relay ID. In
this case, some functions of radio
resource management (RRM) are controlled by the BS of the
donor cell and a part of RRM may be located at the relay.
The L3 relay can control a cell thereof. In this case, the
relay may manage one or more cells and each cell managed by
the relay may have a unique physical-layer cell ID. The
relay may have the same RRM mechanism as the BS. From the
viewpoint of the UE, it makes no difference whether the UE
accesses the cell managed by the relay or the cell managed by
the BS.
In addition, the relay is divided as follows according
to mobility.
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- Fixed RN: This relay is permanently fixed and is used
to increase cell coverage or to eliminate a shadow area and
may function as a repeater.
- Nomadic RN: This relay is temporarily installed when
the number of users is abruptly increased and may be
arbitrarily moved within a building.
- Mobile RN: This relay may be installed in public
transportation such as a bus or a subway and may be moved.
In addition, a link between a relay and a network is
divided as follows.
- In-band connection: A network-to-relay link and a
network-to-UE link share the same frequency band within a
donor cell.
- Out-band connection: A network-to-relay link and a
network-to-UE link use different frequency bands within a
donor cell.
The relay is divided depending on whether a UE
recognizes presence of the relay.
- Transparent relay: The UE is not aware of whether
communication with the network is performed via a relay.
- Non-transparent relay: The UE is aware of whether
communication with the network is performed via a relay.
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FIG. 12 is a diagram showing backhaul communication
using a multimedia broadcast over a single frequency network
(MBSFN) subframe. In an in-band relay mode, a BS-relay link
(that is, a backhaul link) and a relay-UE link (that is, a
relay access link) operate in the same frequency band. If a
relay transmits a signal to a UE while receiving a signal
from a BS and vice versa, since a transmitter and a receiver
of the relay cause interference,
simultaneous
transmission/reception of the relay may be prevented. In
order to prevent simultaneous transmission/reception, a
backhaul link and a relay access link are partitioned using a
TDM scheme. In LTE-A,
a backhaul link is set in an MBSFN
subframe in order to support a measurement operation of a
legacy LTE UE present in a relay zone (a fake MBSFN method).
If an arbitrary subframe is signaled as an MBSFN subframe,
since a UE receives only a control (ctrl) region of the
subframe, a relay may configure a backhaul link using a data
region of the subframe. For example, a relay PDCCH (R-PDCCH)
is transmitted using a specific resource region from a third
OFDM symbol to a last OFDM symbol of an MBSFN subframe.
Embodiment
FIGs. 13 to 14 are diagrams showing arbitrary division
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of frequency-time resources. FIG. 13 shows the case of using
a single antenna port and FIG. 14 shows the case of using
multiple antenna ports.
These figures show part of a
downlink subframe.
In FIG. 13, the size of a frequency-time domain denoted
by X-Y may be variously configured.
In an LTE system, a
resource region X-1 (X=1, 2, 3) may include 12 subcarriers in
a frequency domain and four OFDM symbols in a time domain. A
resource region X-2 (X=1, 2, 3) may include 12 subcarriers in
a frequency domain and seven OFDM symbols in a time domain.
The number of symbols may be changed according to the length
of a cyclic prefix. The number of symbols and the number of
subcarriers may have different values according to system.
In other words, the resource region X-1 may be part of a
first slot and the resource region X-2 may be part of a
second slot.
Such a resource configuration may typically
appear in a backhaul subframe between a BS and a relay. In
this case, FIG. 13 shows the remaining part of the MBSFN
subframe of FIG. 12 except for the control information region.
FIG. 13 shows a resource block (RB) and a resource block
group (RBG) in order to represent a resource size in a
frequency domain. The RB is defined in slot units as shown
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in FIG. 2. Accordingly, X-Y corresponds to one RB and [X-1,
X-2] corresponds to an RB pair. Unless specifically stated,
the RB may be [X-1], [X-2] or [X-1, X-2] according to context.
The RBG includes one or more contiguous RBs. Although the
number of RBs configuring the RBG is 3 in FIG. 13, the number
of RBs configuring the RBG may be changed according to a
system bandwidth as shown in Table 3. The RB means a PRB or
a VRB.
In FIG. 14, the size of the frequency domain and the
size of the time domain in a resource region denoted by Px-yy
(x, y = 0, 1, 2, 3) may be variously configured. The
basic
resource configuration is equal to that described with
reference to FIG. 13. In the
figure, Pn (n=0, 1, 2, 3, ...)
denotes a port or layer used in a multi-layer transmission
system (e.g., an MIMO system). The
port or layer means a
distinguishable resource region capable of transmitting
different information. The meaning of the port or layer may
be differently interpreted according to system. For example,
in a 3GPP LTE system, if P0-12 is one RB, P0-12 may include
12 subcarriers in the frequency domain and seven OFDM symbols
in the time domain. If P0-
12 is one RBG (e.g., RBG=4), the
size of P0-12 in the frequency domain quadruples. A Px-yl
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region includes REs, the number of which is equal to or less
than the number of REs of a Px-y2 region. For example, if
the Px-yl resource region is one RB, the Px-yl resource
region may include 12 subcarriers and four OFDM symbols. If
the Px-yl resource region is one RBG, the size of the Px-yl
resource region in the frequency domain is increased by a
multiple of the RBG unit. The Px-yl region may mean a first
slot or a part thereof and the Px-y2 region may mean a second
slot or a part thereof. The number of symbols may be changed
according to cyclic prefix length. The number of symbols and
the number of subcarriers may have different values according
to system.
Hereinafter, how control information and data are
allocated and transmitted in the resource configuration shown
in FIGs. 13 to 14 will be described.
Unless specifically
stated, a single antenna port will be focused upon and a
resource region is represented by the method of FIG. 13, for
convenience of description. It is apparent to those skilled
in the art that the description of the single antenna port is
applicable to multiple antenna ports.
Control information (e.g., R-PDCCH) used in a link
between a BS and a relay is preferably transmitted in a
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predetermined specific resource region. In one
example of
the present invention, if Type 0 RA of LTE is used, a
specific resource region (which is referred to as an R-PDCCH
search space) in which control information may be transmitted
may be restricted to K-th RBs of allocated RBG(s). Here, K
denotes an integer less than the number of RBs configuring an
RBG. In this
case, the K-th RBs of all allocated RBGs may
transmit an R-PDCCH. K may be a first RB or a last RB of an
RGB group. Even in Type 1 or 2 RA, the concept of the RBG
may be used and a specific RB of an RBG may be used as a
resource region for R-PDCCH transmission in the tautological
sense.
In addition, a method of separating RB(s) for the R-
PDCCH search space from each other by the square of P within
the RBG set if the R-PDCCH search space is set to one subset
of an RBG set is proposed. Here, P
is the number of RBs
within an RBG. For example, assuming that the number of RBs
is 32, 11 RBGs may be defined and one RBG may include three
RBs (P=3). Accordingly, the RBs for the R-PDCCH search space
may be placed at an interval of 3A2=9 RBs. The above-
described example corresponds to the case in which one RBG
subset is used and an interval of RBs within the subset is
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the square of P if the number of RBG subsets is 2. The
interval between subsets may be changed depending on how many
subsets are selected.
R-PDCCH/(R-)PDSCH allocation and demodulation
Control information is transmitted via an R-PDCCH and
data is transmitted via an (R-)PDSCH. The R-PDCCH is roughly
classified into two categories. One
category is DL grant
(DG) and the other category is UL grant (UG). The DL grant
contains information about time/frequency/space resources of
the R-PDSCH corresponding to data which should be received by
a relay and information (scheduling information) for decoding.
The UL grant contains information about time/frequency/space
resources of the R-PUSCH corresponding to data which should
be transmitted by a relay in uplink and information
(scheduling information) for decoding. Hereinafter, a method
of placing DL/UL grant in a resource region of a backhaul
subframe and demodulating the DL/UL grant will be described.
FIG. 15 shows an example of placing and demodulating an
R-PDCCH/(R-)PDSCH. In this
example, it is assumed that
resources for the (R-)PDSCH are allocated using Type 0 RA
(RBG unit allocation) of the LTE.
However, this example is
merely exemplary and is equally/similarly applied to even the
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case in which Type 1 RA (RB unit allocation) of LTE is used.
Although the case in which an RBG including DL grant is
allocated to a relay is shown in FIG. 15, this is merely
exemplary and the RBG including DL grant may not be allocated
to the relay.
FIG. 15 shows the case in which (a) data ((R-)PDSCH) is
present, (b) UL grant is present, or (c) UL grant for another
relay is present in a resource region 1-2 in the case in
which DL grant of RN#1 is present in a resource region 1-1.
In FIG. 15, a determination as to which information of
(a) to (c) is present in the resource region 1-2 may be made
using RA information (e.g., RBG or RB allocation information).
For example, if all RBGs are allocated to RN#1, RN#1 may
interpret RA information of DL grant and determine whether
the resource region 1-2 corresponds to (a) or (b). More
specifically, if data is present in an RB or an RBG in which
a first R-PDCCH (e.g., DL grant) thereof is detected is
present in the resource region X-1, RN#1 may assume that data
thereof is present in resources other than resources occupied
by the first R-PDCCH. Accordingly, if RA information
indicates that data is present in the RB or RBG, RN#1 may
determine that another R-PDCCH is not present in the RB or
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RBG except for DL grant.
That is, the relay may determine
that the resource region 1-2 corresponds to (a).
If the RA
information indicates that data is not present in the RB or
RBG, the relay may determine that a second R-PDCCH is present
as in (b) or (c) and detect an appropriate data start point
(e.g., a resource region 2-1). At this time, the BS and the
relay may assume that the size of the second R-PDCCH is
constant. In case of (c), by attempting CRC detection based
on an RN ID, it may be determined that the second R-PDCCH is
not UL grant for RN#1. Although RA information is used to
distinguish among (a), (b) and (c), it may be implicitly set
that the RBG including DL grant is always resources allocated
for data of RN#1 in advance.
Although FIG. 15 shows the case in which DL grant is
present in the whole resource region X-1 (e.g., 1-1), this is
merely exemplary and the above-described method may be
equally applied to the case in which DL grant is present in a
part of the resource region 1-1. Although FIG. 15 shows the
case in which DL grant is present in the resource region X-1,
UL grant may be present in the resource region X-1 instead of
DL grant. In this case, the relay may first decode UL grant
instead of DL grant. Although the second R-PDCCH is UL grant
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in FIG. 15, this is merely exemplary and the second R-PDCCH
may be DL grant.
FIGs. 16 to 17 show other examples of placing and
demodulating an R-PDCCH/(R-)PDCCH.
In this example, it is
assumed that resources for the (R-)PDSCH are allocated using
Type 0 RA (RBG unit allocation) of LTE.
However, this
example is merely exemplary and is equally/similarly applied
to even the case in which Type 1 RA (RB unit allocation) of
LTE is used. Although the case in which an RBG including DL
grant is allocated to a relay is shown in FIGs. 16 and 17,
this is merely exemplary and the RBG including DL grant may
not be allocated to the relay.
FIGs. 16 and 17 show the case in which (a) data ((R-
)PDSCH) is present in the resource region 2-1/2-2 (not shown),
(b) UL grant for RN#1 is present in the resource region 2-1
(FIG. 16), or (c) UL grant for RN#1 is present in a resource
region 2-1/2-2 (FIG. 17), in the case in which DL grant for
RN#1 is present in the resource region 1-1/1-2.
In this case, RN#1 performs blind decoding so as to
distinguish among (a), (b) and (c).
Data or control
information of RN#1 is preferably present in the resource
region 2-X.
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In addition, RN#1 may distinguish among (a), (b) and (c)
using RA information (e.g., RBG allocation bit) of the DL
grant. For example, RN#1 may determine whether data of RN#1
or UL grant restrictively allocated to the resource region 2-
1 is present in the resource region 2-1 using RA information
(that is, (a) or (b))(case A). In
addition, RN#1 may
determine whether data of RN#1 or UL grant restrictively
allocated to the resource region 2-1/2-2 is present in the
resource region 2-1/2-2 using RA information (that is, (a) or
(c))(case B). The base station-relay operation is set to one
of case A or case B. That is, RN#1 may distinguish between
(a) and (b) or (a) and (c) using RA information (e.g., RBG
allocation bit). The RBG allocation bit indicating which of
(a) and (b) or (a) and (c) is used is set in advance. For
example, it is assumed that UL grant is restricted to the
resource region 2-1 or the resource region 2-1/2-2 in advance.
In addition, in the case in which DL grant for RN#1 is
present in the resource region 1-1/1-2, (a) data of RN4f1 is
present in the resource region 2-1/2-2 (not shown), (b) DL or
UL grant for another RN is present in the resource region 2-1
(FIG. 16), or (c) DL or UL grant for another RN is present in
a resource region 2-1/2-2 (FIG. 17). In this
case, (a) and
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(b) or (a) or (b) may be distinguished using the RBG
allocation bit. A determination as to which of (a) and (b)
or (a) and (c) is used should be set using the RBG allocation
bit in advance.
In the above-described method, assuming that that only
the same DL/UL grant size as the DL grant size is present,
the RBG allocation bit is used to determine whether the value
present in the resource region 2-1 or 2-1/2-2 is data or
control information and the size of the DL/UL grant (that is,
the resource region 2-1 or 2-1/2-2) may be determined
according to the size of the detected DL grant.
The above-described method is equally applied to the
case in which DL grant is present in the resource regions 1-1,
1-2 and 1-3. The above-described method is equally applied
to the case in which all or part of the UL grant is present
in the resource regions 1-1, 2-1 and 3-1 instead of DL grant.
In this case, in the above-described method, the relay first
blind-decodes UL grant instead of DL grant.
Demodulation method using the same DM RS port
A method of demodulating a DL transmission signal of
another resource region using a DM RS corresponding to a
successful DM RS port if demodulation of grant (e.g., DL
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grant) for RN#1 is successful in the resource region 1-1 and,
otherwise, demodulating a DL transmission signal of another
resource region using a DM RS different from the DM RS used
in the resource region 1-1 is proposed. For example, if
demodulation of DL grant of RN#1 is successful in the
resource region 1-1, a DL transmission signal (e.g., UL
grant) of the resource region 1-2 may be demodulated using
the DM RS corresponding to the successful DM RS port and,
otherwise, the DL transmission signal (e.g., UL grant) of the
resource region 1-2 may be demodulated using a DM RS
different from the DM RS port used in the resource region 1-1.
More specifically, if demodulation is successful in the
resource region 1-1 using DM RS port 0, the DL transmission
signal (e.g., UL grant) of the resource region 1-2 may be
demodulated using the DM RS of the same DM RS port 0 and,
otherwise, if demodulation fails, decoding may be performed
using the DM RS of DM RS port 1.
Method of filling RB pair with UL grant (or DL grant) in
TDM+FDM
If UL grant of RN# is present in the resource region 1-1
(that is, if DL grant of RN #1 is not present), the resource
region 1-2 may not be used. In order to solve such a problem,
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a method of filling the resource region 1-2 with UL grant of
the relay(s) including only UL grant is proposed.
If a
plurality of relays including only UL grant is present, it is
possible to minimize resource waste by filling the resource
regions X-1 and X-2 with UL grant.
Similarly, even in the case in which only DL grant is
present, a method of allocating DL grant to the resource
region 1-1 and the resource region 1-2 is proposed.
RS port allocation method
FIGs. 18 to 19 are diagrams showing examples of dividing
an RB pair into a plurality of RE groups. In the examples of
FIGs. 18 and 19, it is assumed that all or part of symbols of
a subframe is defined in a start and end part of a resource
region.
FIG. 18 shows the case of dividing one RB pair into two
RE groups (X-a and X-b). In FIG. 18, the sizes of X-a and X-
b (X=1, 2, 3) may be the same or different.
It is assumed
that the resource regions 1-a and 1-b are used to forward DL
grant and UL grant of RN#1, the resource region 2-a is used
to forward DL grant of RN#2, the resource regions 2-b and 3-a
are used to forward DL grant of RN#3, and the resource region
3-b is used to forward UL grant of RN#3. In this case, the
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resource regions 1-a and 1-b are configured to perform
demodulation based on one DM RS port, the resource regions 2-
a and 2-b are configured to perform demodulation based on
different DM RS ports, and the resource regions 3-a and 3-b
are configured to perform demodulation based on the same DM
RS port. By this configuration, it is possible to obtain a
better performance using the same DM RS port in case of DL/UL
grant forwarded to the same RN and to suitably allocate a DM
RS port to each RN in case of DL/UL grant forwarded to
different RNs.
FIG. 19 shows the case of dividing one RB pair into
three RE groups (X-a, X-b and X-c). FIG. 19 is equal to FIG.
18 except that the number of RE groups is changed. Thus, for
a description thereof, refer to FIG. 18.
R-PDCCH mapping and detection in case of high
aggregation level
In the relay, an R-CCE aggregation level (e.g., 1, 2, 4,
8, ...) of an R-PDCCH may be changed according to channel
environment. This is similar to a CCE set of an LTE PDCCH.
The R-CCE is defined in order to represent a CCE for a relay,
for convenience. In the following description, R-CCE and CCE
are used interchangeably. It is assumed that DL grant of the
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R-PDCCH is present in three RBs as shown in FIG. 20 and UL
grant is transmitted in a second slot of two RB pairs.
In
this case, when DL grant is blind-decoded to check R-CCE
aggregation shown in FIG. 20, the relay may not be aware of
whether UL grant or data is present in the second slot.
A method similar to the above-described method is
applicable. That is, it is possible to indicate whether UL
grant is present in the second slot using an RBG allocation
bit. Preferably, it may be assumed that an RBG including DL
grant is allocated to the relay. Accordingly, if DL grant is
present in a first slot, a resource allocation bit of the RBG
may indicate whether an R-PDSCH or UL grant is present in a
second slot. The following cases are possible.
(a) Presence of the R-PDSCH in the second slot, or
(b) Presence of UL grant for a relay or UL grant for
another relay in the second slot. UL grant of another RN may
be CRC checked using an RN ID.
It is necessary to determine in which RB(s) UL grant is
present. The number of RB pairs including UL grant may be
changed according to R-CCE aggregation level.
The number/positions of RB pairs including UL grant may
be checked by generating a simple relationship between a DL
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grant size and a UL grant size, which will be described with
reference to FIGs. 21 to 22.
Referring to FIG. 21, UL grant may always be present in
an RB pair including DL grant. Accordingly, if DL grant is
present in two RB pairs, UL grant may be equally present in
two RB pairs.
Accordingly, if DL grant is successfully
detected, the relay may check where UL grant is present. At
this time, the aggregation level of UL grant may be set to be
greater than the aggregation level of DL grant.
Alternatively, it may be defined that a difference between
the aggregation level of DL grant and the aggregation level
of UL grant is N_level in advance.
In one embodiment, it may be defined that one R-CCE is
present in a first slot of an RB pair and two R-CCEs are
present in a second slot.
In this case, the R-CCE of the
first slot and the R-CCE of the second slot are different in
size.
According to the present example, it may be defined
that the aggregation level of DL grant x 2 = the aggregation
level of UL grant in advance.
Referring to FIG. 21, the
aggregation level of DL grant for RN#1 is 1 and the
aggregation level of UL grant is 4.
Similarly, the
aggregation level of DL grant for RN#2 is 3 and the
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aggregation level of UL grant is 6.
As another example, it may be defined that an R-CCE size
may be defined in slot units. That is, one R-CCE is present
in a first slot of an RB pair and one R-CCE is present in a
second slot. In this case, the R-CCE of the first slot and
the R-CCE of the second slot are different in size.
According to this example, it may be defined that the
aggregation level of DL grant = the aggregation level of UL
grant in advance. Referring to FIG. 21, in case of RN#1, the
aggregation level of DL grant = the aggregation level of UL
grant = 2. Similarly, in case of RN#2, the aggregation level
of DL grant = the aggregation level of UL grant = 3.
Referring to FIG. 22, an R-CCE size is set to 1 and the
aggregation level of DL grant is equal to the aggregation
level of UL grant. For example, the R-CCE size may be 32 REs.
In this case, since the resource region of the second slot is
larger, the placement shown in FIG. 22 is obtained. In case
of RN#2, only some resources of the second slot of the second
RB pair are used to transmit UL grant.
In this case, an
empty space of the second slot may be used to transmit data
(FIG. 22(a)) or may not be used to transmit data (FIG. 22(b)).
As another method, the number of RBs occupied by UL
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grant may be restricted. For example, as in the case of RN#1
of FIG. 22, there is a restriction that UL grant may always
be transmitted in the second slot of one RB pair.
Such a
restriction may be fixed in the standard and may be
transmitted from a BS to an RN through a higher layer signal.
If such a restriction is present, the RN may easily check the
position of the region occupied by UL grant by reinterpreting
the above-described RA information and thus check the
position of a data signal.
In the above description, the RBG allocation bit may be
reinterpreted and used to distinguish between UL grant and
data (R-PDSCH) because of the assumption that the RBG is used
only for the RN.
However, if the RBG is used as original
meaning thereof, a separate signal may be generated. Such a
signal may be present in the R-PDCCH. A determination as to
whether a separate signal is used or the RBG is reinterpreted
and used may be set in advance or may be configured through
semi-static signaling.
If decoding of UL grant fails in spite of indicating
that UL grant is present in the above-described methods, data
(including UL grant) present in the slot may be combined with
data retransmitted via HARQ.
In this case, since serious
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error may be generated in HARQ-combined data due to UL grant,
previous data which may be included in UL grant may not be
used in a HARQ combining process.
FIG. 23 shows a method of enabling DL grant to indicate
presence of UL grant in a second slot by locating DL grant in
a first slot even when only UL grant is present.
Referring to FIG. 23, even in the case in which there is
no downlink data (e.g., (R-)PDSCH) to be transmitted from a
BS to an RN (that is, UL grant only case), null DL grant (or
dummy DL grant) may be transmitted in order to inform the RN
that UL grant is present in the second slot of the same RB
pair. According
to the present example, regardless of
presence/absence of downlink data for the RN, blind decoding
for UL grant may be omitted and thus blind decoding
complexity of the RN is reduced. In the case in which both
DL grant and UL grant are transmitted but there is no
downlink data for the RN as in this example, it should be
indicated that there is no data corresponding to DL grant
(that is, null DL grant).
Therefore, null DL grant may
indicate that all downlink transport blocks or codewords are
disabled. In
addition, null DL grant may indicate that a
downlink transport block size (TBS) is TBS=0 or TBS<K (e.g.,
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4 RBs). In
addition, null DL grant may indicate that there
is no RB allocated for downlink transmission. In addition, a
specific field within null DL grant may be set to "0" or "1".
If null DL grant is detected, the relay interprets that data
corresponding to null DL grant is not transmitted and checks
presence of UL grant in the second slot from null DL grant.
Method of indicating use state of second slot (e.g., RA
bit use)
Hereinafter, a method of indicating presence/absence of
UL grant or presence/absence of an (R-)PDSCH using a bit (or
similar information) of a DCI resource allocation (RA) field
so as to accurately perform PDSCH data decoding will be
described. For
convenience, resource allocation technology
used in the description is LTE technology. An RA
bit
indicates whether an RB or an RBG is allocated for PDSCH
transmission. It is
assumed that the RB or RBG is not
allocated for (R-)PDSCH transmission in case of RA bit = 0
and is allocated for R-PDSCH in case of RA bit = 1. The
meaning of the RA bit may be inversely interpreted. The
meaning of the RB bit may be differently interpreted
according to DL grant and UL grant.
DL grant and UL grant may be present in RBs of different
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slots. For example, DL grant may be present in an RB of a
first slot and UL grant may be present in an RB of a second
slot.
In this case, a resource region for DL data and a
region for UL grant coexist.
Resources used to actually
transmit DL data are indicated by RA of DL grant and
resources used to actually transmit UL grant are checked
blind decoding.
Accordingly, if UL grant is detected in a
resource region to which DL data is allocated, an RN
receives/decodes DL data from resources other than resources
in which UL grant is detected (that is, rate matching). For
this reason, non-detection or misdetection of UL grant
unpreferably influences on DL data decoding.
In order to solve this problem, the following
restrictions are applicable to BS-RN communication.
- The RN may assume that there is no UL grant in an RB
or RBG in which a DL RA bit is set to 1. That is, the RN may
assume that UL grant may be transmitted only in an RB or RBG
in which a DL resource allocation bit is 0. In this example,
some resources may be used to transmit data in an RBG in
which a DL resource allocation bit is 0.
- The above restriction may guarantee accurate rate
matching upon DL data (that is, (R)-PDSCH) decoding even when
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UL grant detection fails (that is, a non-detection case) or
UL grant is misdetected (that is, a false alarm case).
- Accordingly, the BS does not transmit UL grant in an
RB or RBG in which a DL resource allocation bit is set to 1.
For example, in case of Type 0 RA, the BS does not transmit
UL grant in an RBG to which DL data for the RN is allocated,
except for an RBG in which DL grant and UL grant coexist.
FIG. 24 is a diagram showing the case of transmitting UL
grant only in the case in which a DL RA bit is set to 0. For
convenience, this example is described using Type 0 RA of LTE.
RA=1 means that an RBG is allocated for DL data transmission
according to normal RA interpretation.
However, RA=0 may
have meaning different from normal RA interpretation.
In
this example, it is assumed that a DL grant search space and
a UL grant search space are respectively present.
Referring to FIG. 24, if DL grant is successfully
detected and an RA bit is, for example, "0", UL grant may be
designed to be present at an arbitrary place of an RB or RBG
in which the RA bit is "0" within a UL grant search space (UL
SS).
Although the UL grant search space is configured
regardless of the RA bit, a BS scheduler may intentionally
allow UL grant to be present only in a place where an RA bit
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is "0". That is, RA bit = 0 means an RBG in which UL grant
may be transmitted and resources in which UL grant may be
transmitted may be restricted to resources satisfying both UL
SS and RA bit = 0. In this case, RA bit = 0 indicates some
subsets in an R-PDCCH search space. Accordingly, the RN may
restrict a UL grant search position to resources set to RA
bit = 0 within the UL SS if DL grant is detected. Therefore,
it is possible to prevent unnecessary UL grant misdetection.
In other words, an RB or RBG with RA bit = 1 may be excluded
from a UL grant search space.
If RA bit = 1, the RN may assume that UL grant is not
transmitted in the RB or the RBG. In contrast, RA bit = 0,
the RN may assume that UL grant may be transmitted in the RB
or RBG. The BS transmits UL grant in the RB or RBG with RA
bit = 0. The RN may perform blind decoding when being
unaware of presence/position of UL grant and decode UL grant
at a specified position when being aware of the position of
UL grant. According to interpretation of RA bit . 0, since a
UL Grant search space (UL SS) can be dynamically restricted
(or allocated) using DL RA, it is possible to reduce the
number of times of blind decoding for UL grant.
In the above description, RA bit = 0 is interpreted as
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resources used to transmit UL grant. However, RA bit = 0 may
mean an RB or RBG in which UL grant is actually transmitted
within UL SS. In this case, interpretation of RA bit = 0 may
be restricted to a specific RB (pair) or RBG. For example,
interpretation of RA bit = 0 may be restricted to an RB
(pair) or RBG in which DL grant is present.
In consideration of data transmission, interpretation of
RA bit = 0 may further include the following cases.
For
example, an RBG with RA=0 may include data transmission if DL
grant or an arbitrary R-PDCCH is present in the RBG ((a) to
(b)). As another example, there may not be data transmission
in an RBG with RA=0 regardless of presence/absence of an R-
PDCCH ((c) to (d)).
In FIG. 24, a dotted line shows the case in which Type 1
RA is used.
In Type 1 RA, interpretation of an RA bit is
applied in RB units.
In the following description, if an aggregation level of
DL and UL grant is increased, it is assumed that R-PDCCHs are
sequentially and contiguously extended and allocated to
neighboring VRBs (non-interleaving).
In this case, R-PDCCHs
are not non-contiguously allocated. Actual PRB mapping may
be different.
Although RA information within DL grant is
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described based on Type 0 of LTE in the following description,
the RA information within DL grant is not limited to a
specific type in the present invention.
FIG. 25 shows a method of indicating an RA state (e.g.,
presence/absence of UL grant) of a second slot according to
the present invention. FIG. 25 shows the case of RBG=3RBs, 1
CCE DL grant and 1 CCE UL grant. For convenience, one RBG,
in which DL grant is present, among three RBGs allocated by
DL RA is shown. If interleaving is applied, DL grant may be
present in a plurality of RBs or RBGs.
Referring to FIG. 25, if 1-CCE DL grant is transmitted,
a method of indicating whether UL grant is present in a
resource region of a next slot is performed by reinterpreting
the existing RA bit (an RB indicator or an RBG indicator).
For example, in case of RA bit = 0, UL grant may be present
in a next slot of an RB pair in which DL grant is present in
the RBG and an R-PDSCH is allocated from a next RB pair. In
contrast, in case of RA bit = 1, UL grant is not present in a
next slot of an RB pair in which DL grant is present in the
RBG and the resource region is filled with an R-PDSCH or an
R-PDSCH is not present in the resource region.
Presence/absence of the R-PDSCH is set in advance as shown in
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FIG. 24. Interpretation of the RB bit shown in FIG. 25 may
be restricted to an RB (pair) or RBG in which DL grant is
present.
In LTE, DCI formats 0 and 1A are equal in size and are
distinguished using a 1-bit type indication field.
If DL
grant and UL grant are respectively configured in independent
spaces, a field for distinguishing DL/UL grant is not
necessary.
Accordingly, although not shown, as another
example, a type indication field for distinguishing between
DCI formats 0 and 1A may be used as described above.
For
example, a type indication field may indicate
presence/absence of UL grant or presence/position/placement
of UL grant (e.g., a second slot of an RB pair in which DL
grant is present, 1 CCE).
In this example, the type
indication field may be used additionally to or independently
of the existing RA bit.
Since a resource region of a second slot is greater that
a resource region of a first slot within an RB pair, the
number of CCEs included in an RB of each slot may be
differently defined.
For example, the RB of the first slot
may include one CCE and the RB of the second slot may include
two CCEs.
In this case, UL grant may occupy only one CCE
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between two CCEs of the second slot. In addition, UL grant
may be predetermined or signaled so as to completely fill the
resource region of the second slot (2 CCEs).
The CCE
aggregation level of UL grant is preferably extended to 2, 4
or 6 because of simple signaling.
FIGs. 26a to 26c show UL grant transmission according to
a DL grant CCE aggregation level. FIGs. 26a to 26c show the
cases in which the DL grant CCE aggregation level is 1, 2 and
3, respectively. Although RBG=3RB5 is shown, the number of
REs configuring the RBG is not limited thereto.
For
convenience, one RBG, in which DL grant is present, among
three RBGs allocated by DL RA is shown. If interleaving is
applied, DL grant may be present in a plurality of RBs or
RBGs.
Referring to FIG. 26a, if 1-CCE DL grant is detected by
blind decoding (BD), it is important to check how UL grant is
placed in a second slot/resource region of an RB pair in
which DL grant is detected.
If decoding of UL grant fails
and this UL grant is misrecognized as data and is decoded,
(R-)PDSCH decoding error may be generated.
Accordingly, it
is necessary to accurately detect the position of UL grant in
terms of error case handling. If 1-CCE DL grant is detected
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in a first resource region, a method of indicating UL grant
or (R-)PDSCH (including empty) in a second resource region
may use an RA bit (RB indicator) for an RB or an RA bit (RBG
indicator) for an RBG. Since
only two cases are indicated,
1-bit information is sufficient.
Referring to FIG. 26b, if 2-CCE DL grant is detected,
the number of cases of placing UL grant and R-PDSCHs in a
second resource region of an RB pair is large, but may be
restricted to three if the above-description assumption is
applied as shown.
Accordingly, instead of 1 bit, a 2-bit
indication is required. All cases may be indicated by adding
additional 1 bit to the 1-bit RBG indication of FIG. 26a.
The additional 1 bit may be obtained from a DCI format. For
example, in a DCI field, a bit left by reducing the size of a
field which may be restricted in backhaul may be used. More
specifically, if a field is used in backhaul, a method of
slightly reducing the width of the existing RA information
and using the remaining bit may be used. In an LTE-
A DCI
format, a bit of a field, significance of which is not
present or is reduced with respect to backhaul, in an
additionally defined field of an LTE-A DCI may be borrowed
and used. For example, a CIF field has 3 bits, but a maximum
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number of carriers in LTE-A is 5 and the number of actually
used carriers may be less than the maximum number of carriers.
Accordingly, 1 bit or a plurality of states may be borrowed
from the CIF field. In
addition, a combination of RRC
signaling and an RA bit may be used. More specifically, the
number of cases may be partially restricted through RRC
signaling and one of the remaining cases may be indicated by
an RA bit. For example, a UL grant transmission case may be
restricted to (a) and (c) through RRC signaling and (a) or
(c) may be indicated by an RA bit. The above description is
commonly applied to all subsequent figures.
Referring to FIG. 26c, if 3-CCE DL grant is detected,
the number of cases of placing UL grant and R-PDSCHs in a
second resource region of an RB pair is large, but may be
restricted to four if the above-description assumption is
applied as shown.
Accordingly, as shown in FIG. 26b, all
cases may be indicated by 1 bit + 1 bit = 2 bits.
Alternatively, 3-CCE DL grant allocation may not be performed.
By restricting a CCE aggregation level to 2An (n=0, 1, 2,
it is possible to reduce DL grant BD complexity. For example,
the RN may perform BD only with respect to 1-, 2- or 4-CCE DL
grant.
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FIGs. 27a to 27d show UL grant transmission according to
a DL grant CCE aggregation level if an RBG includes four RBs.
FIGs. 27a to 27d show the case in which the DL grant CCE
aggregation level is 1, 2, 3 and 4, respectively. For
convenience, one RBG, in which DL grant is present, among
three RBGs allocated by DL RA is shown. If interleaving is
applied, DL grant may be present in a plurality of RBs or
RBGs. Since the basic conditions are equal to FIGs. 27a to
27c, refer to FIGs. 27a to 27c, for detailed description
thereof.
Referring to FIG. 27a, if 1-CCE DL grant is detected,
two transmission cases may be applied and may be indicated by
an RA bit (1 bit) of an RBG. Referring to FIG. 27b, if 2-CCE
DL grant is detected, three transmission cases may be applied
and indicated by 2 bits. As described with reference to FIG.
26b, three cases may be indicated by adding additional 1 bit
to the RA bit (1 bit) of the RBG. For
example, the
additional 1 bit may be obtained from a DCI format. For
example, a bit left by slightly reducing the width of the
existing RA information may be used. In addition, 1 bit or a
plurality of states may be borrowed from the CIF field. In
addition, a combination of RRC signaling and an RA bit may be
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used. In this
case, the number of cases may be restricted
through RRC signaling and one of the remaining cases may be
indicated by an RA bit.
Referring to FIG. 27c, if 3-CCE DL grant is detected,
four transmission cases may be applied.
Accordingly, all
cases may be indicated by 2 bits. Similarly to RBG=3RB5 of
FIG. 26c, the 3-CCE DL grant case may be excluded. Referring
to FIG. 27d, if 4-CCE DL grant is detected, five transmission
cases may be applied.
Accordingly, all cases may not be
indicated by 2 bits. However, an additional assumption may
be given. For
example, in FIG. 27d, 3-CCE UL grant (c) in
which the CCE aggregation level is an odd number may not be
used. Alternatively, in FIG. 27d, 4-CCE UL grant may not be
used. Since
resources of the second slot are more than
resources of the first slot, the CCE aggregation level of DL
grant may be set to be lower than the CCE aggregation level
of UL grant. By excluding one or more cases from (a) to (d),
all cases may be indicated by 2 bits.
In the above-described case, all cases may be indicated
by 2 bits by restricting the UL grant aggregation level. For
example, the UL grant aggregation level may be restricted to
1 and 2 or 1, 2 and 4. In
particular, since a second
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resource region in which UL grant is located is large, it is
assumed that only 1 RB (e.g., 1-CCE) or 2 RBs (2-CCE) is used.
Since the CCE of the second slot includes REs which
correspond to about twice those of the CCE of the first slot,
even when the UL grant aggregation level is restricted to 1
or 2, UL grant may substantially have a code rate
corresponding to DL grant of an aggregation level of 2 or 4.
If a boundary between the first resource region and the
second resource region is adjusted such that the resource
regions are identical, a method of setting the UL grant
aggregation level to 1, 2 and 4 is advantageous.
In this
case, the DL grant aggregation is preferably restricted to 1,
2 and 4.
CCEs having the same size may be defined or several CCE
having a restricted size may be defined. The above-described
CCE conceptually represents a unit for allocating DL/UL grant
as shown in each figure.
In the above description, an example of providing
information about a use state (e.g., presence/placement of UL
grant) of a second slot was described by differently
interpreting the RA bit.
However, instead of differently
interpreting the RA bit, a new bit field may be added to DCI
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in order to provide information about the use state of the
second slot. The new bit field may be part (e.g., 2 bits) of
a bit field previously defined for another purpose or a
dedicated bit field newly defined for this purpose.
FIG. 28 shows an example of using a field of a DCI
format in order to provide information about a use state
(e.g., presence/placement of UL grant) of a second slot. The
method of FIG. 28 may be used along with or separately from
interpretation of the RA bit.
Referring to FIG. 28, DCI format 0/1A includes a 1-bit
flag field (0/1A) for distinguishing the DCI format 0/1A.
DCI format 0 is for UL grant and DCI format lA is for DL
grant. As shown in the above figures, if resources used to
transmit DL grant and UL grant are divided in a time domain
or a UL grant size is different from a DL grant size, the
flag field for distinguishing the DCI format 0/1A is not
necessary. Accordingly, the flag field for distinguishing
the DCI format 0/1A may be used to provide information about
the use state (e.g., presence/placement of UL grant) of the
second slot.
In addition, DCI format 1A/1B/1C includes an
L/DVRB indication field (L/DVRB). In case of an RN, if DVRB
is always disabled (OFF) and only LVRB is supported, the
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L/DVRB indication field may be used to provide information
about the use state (e.g., presence/placement of UL grant) of
the second slot. DCI
format 1/2/2A/2B includes a resource
allocation header field RA Hdr indicating RA type 0/1. If
the RA type is semi-statically signaled by a higher layer
(e.g., RRC), a field indicating the RA type may be used to
provide information about the use state (e.g.,
presence/placement of UL grant) of the second slot.
RRC signal + RBG indication
Next, a method of using an RRC signal in order to
provide information about the use state (e.g.,
presence/placement of UL grant) of the second slot will be
described in detail. A method of maintaining each field of
the existing DCI format and indicating information associated
with a DL grant aggregation level or a UL grant aggregation
level through RRC may be used. In
particular, information
associated with the DL/UL grant aggregation level may be
transmitted on a RN-specific basis. Since each RN has unique
channel quality and a channel is not rapidly changed due to
the nature of backhaul, at least the aggregation level may be
signaled through RRC.
Information associated with the
aggregation level may mean a DL/UL grant aggregation level
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(e.g., 1 CCE, 2 CCEs, etc.) or even a resource region (or
resource placement) occupied by DL/UL grant. The existing RA
bit (e.g., an RBG indication bit) may be reinterpreted and
used. By using the RRC signal and reinterpretation of the RA
bit, a specific bit does not need to be borrowed from the
existing DCI format. For
example, a CCE aggregation level
may be indicated by the RRC signal and presence/absence of UL
grant, presence/absence of data, etc. may be indicated by a
DL RA bit in a second slot. This has
an advantage that
presence/absence of UL grant or (R-)PDSCH is dynamically
indicated on a subframe basis.
FIG. 29 shows an example of indicating placement of UL
grant by an RRC signal. FIG. 29 shows the case of RBG=4RB5
and 4-CCE DL grant. Although FIG. 29 shows a total of five
UL grant placement combinations, there may be more various
combinations. If the
number of UL grant placement
combinations is restricted to 5, 5 pieces of placement
information may be signaled to each RN through RRC. The RA
bit (that is, RBG indication bit) may be used to check
presence/absence of UL grant in the RBG. For example, if one
of (a) to (d) is indicated through RRC signaling, the RN may
interpret the use state of the second slot as (a) or (e) by
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the RA bit.
If the size of the RRC signaling bit is not
problematic, placement of all cases may be signaled.
Thus,
optimized resource allocation is possible. In this case, if
the relay may attempt to perform blind decoding with respect
to (a) to (d) in the RBG if the RA bit is 0.
As another
method, along with or separately from interpretation of the
RA bit, placement of actually transmitted UL grant may be
indicated using the DCI field (or bit) (e.g., a type
indication bit) described with reference to FIG. 28.
FIG. 30 shows all cases in which UL grant may be placed
in case of RBG=3RB5 and 2-CCE DL grant. Similarly to FIG. 29,
a UL grant position is restricted using an RRC signal and
presence/absence of UL grant may be checked using an RBG
indication bit.
FIG. 31 shows all cases in which UL grant may be placed
in case of RBG=1RB and 1-CCE DL grant. Unlike FIGs. 29 to 30,
FIG. 31 shows the case in which a UL grant allocation unit is
decreased. FIGs. 29 to 30 show the case in which one CCE is
present in the RB of the second slot, and FIG. 31 shows the
case in which two CCEs are present in the RB of the second
slot.
Even in this case, similarly to FIG. 29, a UL grant
position is restricted using an RRC signal and
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presence/absence of UL grant may be checked using an RBG
indication bit.
Although an RRC signal is an RN-specific signal in the
above description, the RRC signal may be defined as an RN-
common signal. This is possible if an RN-common channel is
present. In addition, the RN-common signal is preferable if
the channel properties of all RN-BS links are substantially
similar.
RA bit interpretation
FIG. 32 shows more various methods of RA bit
interpretation. Referring to FIG. 32, the following four
methods may be considered with respect to RA bit
interpretation (Alt#1 to Alt4*4).
Method #1 (A1t4f1)
- An RB pair which does not include DL grant (or a
frequency domain) in an RBG in which DL grant is detected is
always used for data (e.g., (R-)PDSCH) transmission of an RN
which is a destination of DL grant.
- An RA bit of an RBG indicates usage of a second slot
in an RB pair including DL grant. As shown in FIG. 32, UL
grant may be transmitted in the resource region (UL
grant/empty) if the RA bit is 0 and data may be transmitted
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in the resource region if the RA bit is 1. The RA bit may be
inversely interpreted. In some cases, it may be assembled
that UL grant may always be transmitted in the second slot of
the RB pair including DL grant if the RA bit is 0.
Method #2 (Alt #2)
- An RB pair which does not include DL grant (or a
frequency domain) in an RBG in which DL grant is detected is
not always used for data (e.g., R-PDSCH) transmission of an
RN which is a destination of DL grant.
- An RA bit of an RBG indicates usage of a second slot
in an RB pair including DL grant. As shown in FIG. 32, UL
grant may be transmitted in the resource region (UL
grant/empty) if the RA bit is 0 and data may be transmitted
in the resource region if the RA bit is 1. The RA bit may be
inversely interpreted.
Method #3 (Alt #3)
- Resources of a second slot in an RB pair including DL
grant in an RBG in which DL grant is detected are not always
used for data transmission of an RN which is a destination of
DL grant.
- An RA bit of an RBG indicates usage of a second slot
in an RB pair (or the frequency domain) which does not
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include DL grant. As
shown in FIG. 32, data is not
transmitted in the resource region if the RA bit is 0 and
data is transmitted if the RA bit is 1. The RA bit may be
inversely interpreted.
Method #4 (Alt #4)
- An RA bit of an RBG indicates usage of the resource
region except for DL grant in the RBG in which DL grant is
detected.
- As shown in FIG. 32, data is not transmitted in the
resource region if the RA bit is 0. In this case, a second
slot of an RB pair in which DL grant is present may be used
to transmit UL grant. If the
RA bit is 1, data is
transmitted in the whole resource region except for DL grant
within the RBG. The RA bit may be inversely interpreted.
The method of FIG. 32 may be independently used and may
be set by a higher layer (e.g., RRC) signal or a physical
layer signal. In addition, fallback may be performed using a
specific method according to a frequency domain occupied by
DL grant. For example, if the number of RB pairs occupied by
DL grant is equal to or greater than a predetermined value
(e.g., 3), an operation may be performed using one previously
selected from between method #1 and method #2 (that is,
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fallback mode).
In addition, a method may be selected and
used according to a transmission mode, whether or not
interleaving is performed (that is, an interleaving mode or a
non-interleaving mode), an R-PDCCH RS type (e.g., a DM RS or
a CRS). In this case, a basic method is set as in a fallback
operation and a specific method may be automatically applied
according to configuration mode.
In Methods #1 to #4 of FIG. 32, a signal for
distinguishing between 0 and 1 may be an RA bit. As another
example, in methods #1 to #4, a signal for distinguishing
between 0 and 1 may be some bits (e.g., see the description
of FIG. 28) within the DCI. As another example, in methods
#1 to #4, a signal for distinguishing between 0 and 1 may be
an RRC bit.
As another example, in methods #1 to #4, a
signal for distinguishing each state may be an indicator of a
new format composed of an RA bit and an RRC bit. For example,
four states may be indicated by combining 1 RA bit + 1 RRC
signal bit. In this case, an additional state may be defined
with respect to each method. In addition, in methods #1 to
#4, a signal for distinguishing each state may be a 2-bit
signal composed of an RA bit + an additional bit (e.g., a
type indication bit, etc.).
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In FIG. 32, the position of UL grant means UL grant or
an empty state. If UL grant decoding fails, a corresponding
region is not used for data transmission, UL grant
transmission is not different from the empty state upon (R-
)PDSCH decoding, from the viewpoint of the RN. However, from
the viewpoint of the BS, there is a difference between
transmission of UL grant and non-transmission of UL grant.
Accordingly, denotation of the figure may be changed
according to viewpoint.
In FIG. 32, it is assumed that the size of DL grant (an
aggregation level or a resource region) and the size of UL
grant are identical.
FIG. 32 is merely exemplary and the
same method is applied to the case in which the DL grant
aggregation level and the UL grant aggregation level are
different.
In this case, there are more cases with respect
to each method and thus a signal of 2 bits or more may be
necessary.
RA bit interpretation considering asymmetric or
symmetric subframe allocation
FIGs. 33 to 34 show the case in which a pair of DL grant
and UL grant is always present and the case in which DL grant
and UL grant are separately present. Referring to FIGs. 33
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to 34, the following six methods may be considered with
respect to RA bit interpretation (Alt#5 to Alt#10). An RA
bit (or another bit or a new bit) may be used to indicate the
position/placement of DL/UL grant and data.
In Method #5 (Alt #5), it is assumed that DL grant is
detected in two RB pairs (e.g., aggregation level = 2) and UL
grant is transmitted in a second slot (e.g., aggregation
level = 2) of two RB pairs. In this case, an indication bit
(e.g., an RA bit) of 0 means that data is not present in the
remaining resource region of the RBG and an indication bit
(e.g., an RA bit) of 1 means that data is present in the
remaining resource region of the RBG.
Method #6 (Alt #6) and Method #7 (Alt #7) may be applied
to the case in which only DL grant is present, that is, the
case in which UL grant is not present. Method #6 means that
up to a second slot of an RB pair in which DL grant is
present is filled with data if an indication bit (e.g., an RA
bit) is 1. In
contrast, Method #7 (Alt #7) indicates that
data is not present in a second slot of an RB pair in which
DL grant is present if an indication bit (e.g., an RA bit) is
1 and data is present only in the remaining RB pair in which
DL grant is not present. In
Method #6/#7, if an indication
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bit (e.g., an RA bit) is 0, it means that data is not present
in resources except for resources in which DL grant is
present within the RBG.
Method #8 (Alt #8), Method #9(Alt #9) and Method #10
(Alt#10) of FIG. 34 show the case in which the aggregation
levels or the resource regions of DL grant and UL grant are
not identical.
Although the DL and UL grant aggregation
levels are identical due to a single CCE size, DL grant may
be placed in two RBs and UL grant may be placed in one RB.
In this case, this example means RB mapping rather than
aggregation level.
The above-described RA interpretation method may be
differently applied according to backhaul subframe allocation.
For example, if a pair of a DL subframe and an UL subframe is
allocated to backhaul (that is, UL grant for UL backhaul is
transmitted in a DL backhaul subframe), RA interpretation is
applicable on the assumption that UL grant is always
transmitted, as in method #5 or #8.
In contrast, in a DL
subframe which does not accompany a UL subframe in which UL
grant will be transmitted on a HARQ timeline (which may be
referred to as a DL standalone subframe), RA interpretation
may be applied on the assumption that UL grant is not present
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as in Methods #6, #7, #9 and #10. That is, according to the
present method, the signal 0/1 may be interpreted in the
subframe in which DL grant and UL grant are present and the
DL standalone subframe. For example, even when there is no
separate signal, the RN may automatically apply
interpretation of Methods #5 and #8 in a normal subframe and
interpretation of Methods #6, #7, #9 and #10 in the DL
standalone subframe.
RA interpretation considering various aggregation levels
FIG. 35 illustrates the role of an RA bit in a blind
decoding process if the aggregation levels of DL grant and UL
grant are changed.
Referring to FIG. 35, if the RA bit is 1, it indicates
that the RBG is composed of only DL grant and (R-)PDSCH data.
That is, a place except for an RB in which DL grant is
detected through blind decoding is filled with data to be
transmitted. If the RA bit is 0, it indicates that UL grant
is necessarily present.
The aggregation level of UL grant
may be checked through blind decoding.
That is, if blind
decoding of DL grant is successful, RA bit = 0 or RA bit = 1
is applied to the region except for the RB.
In case of RA
bit = 0, the RN may check the region occupied by UL grant
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through blind decoding.
Accordingly, if only one RB is
occupied by UL grant through blind decoding, the remaining
region is filled with data to be transmitted. Similarly, if
UL grant extends over a plurality of RBs, the region except
for the RBs, in which UL grant is present, obtained through
blind decoding is used as data.
However, if the number of
RBs over which DL grant extends is greater than the number of
RBs over which UL grant extends, the region except for the
region in which DL grant is transmitted in a first region may
be empty. That is, when only UL grant is transmitted in a
second slot within an RB pair, a first slot of the RB pair
may be always empty.
That is, resources of a first slot
within the RB pair in which UL grant is transmitted may be
used only for DL grant and may not used for data.
Even when the RA bit is 0, blind decoding of UL grant in
the second slot may fail. In this case, the RN should decode
data in a state of being unaware of up to which region UL
grant is present and thus data decoding may fail.
Since
blind decoding failure of UL grant does not frequently occur,
data decoding may be abandoned.
That is, if UL grant
decoding fails, data may be discarded.
FIG. 36 illustrates the role of an RA bit in a blind
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decoding process in the case in which it is assumed that DL
grant and UL grant are always transmitted.
Referring to FIG. 36, the case in which the RA bit is 1
does not occur in FIG. 35.
Although UL grant is present,
since it is impossible to guarantee that the UL and DL grant
aggregation levels are identical, the four cases in which the
RA bit is 0 in FIG. 35 are valid.
Accordingly, in the
present example, the RA bit may be used to divide the cases
in which the RA bit is 0 into two groups in FIG. 35.
For
example, the case in which the RB occupied by UL grant is
equal to or greater than the RB occupied by DL grant is
indicated by RA bit = 0 and the opposite case thereof is
indicated by RA bit = I.
In case of RA bit = 1, a
combination of DL grant and data may always be present in at
least one RB pair. A determination as to over how many RBs
UL grant extend (that is, an aggregation level) may be made
by blind decoding.
Accordingly, if blind decoding of UL
grant fails, a method of discarding data of RBG may be used.
If an additional bit (e.g., a type indication bit) is used,
all four cases may be distinguished (RA bit + type bit = 2
bits).
Accordingly, it is possible to detect UL grant
without blind decoding. Meanwhile, if there is a restriction
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in placement of DL grant and UL grant, a 1 bit may be
signaled without an additional bit.
For example, two cases
among the cases shown in FIG. 36 may be excluded by
restricting a size ratio of DL grant and UL grant or
restricting an aggregation level.
Signaling indicating one of resource use methods
FIG. 37 shows an example of a resource use method of a
second slot.
For convenience, FIG. 37 shows Method #1 to
Method #4 shown in FIG. 32.
Accordingly, for Method #1 to
Method #4, refer to FIG. 32.
Method #1 (Alt #1) will be briefly described with
reference to FIG. 37. In Method #1, if DL grant is present,
data thereof is always present. Here, it is assumed that the
size of UL grant is decided according to the size of DL grant.
For example, it may be assumed that the size of UL grant is
equal to or less than the size of DL grant, in terms of the
size of the actual resource region or the CCE aggregation
level. Method #1 is preferable in terms of resource use and
UL grant decoding error case handling.
However, in some
cases, Method #4 or Method #3 may be advantageous when taking
RS format and interleaving into consideration. Accordingly,
a method of selecting and using each method according to
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circumstances is proposed. For example, both Method #1 and
Method #4 may be used and signaling (e.g., RRC) for
distinguishing between both methods may be used. If DL grant
is transmitted in several RBGs, there is
an
assumption/restriction that an assumption that RBs in which
DL grant is not included in one RBG are used as data is
equally applied to all RBGs. Otherwise, whenever the RBG is
increased by one, additional signaling information of 1 bit
is required.
The restriction in the number of bits is not
problematic in case of RRC signaling.
As another example, Methods #1, #3 and #4 may be
configured, respectively.
Method #3 may be used if
interleaving is applied. In case of interleaving, a resource
region is not used to transmit data regardless of whether or
not part of UL grant is present in the second slot.
Accordingly, if interleaving is applied, Method #3 is
preferably used.
In addition, a method of automatically
determining a method according to a transmission mode may be
used.
In addition, each method may be selected and used
depending on whether interleaving is applied (that is, an
interleaving mode or a non-interleaving mode) or an R-PDCCH
RS type (e.g., a DM RS or a CRS).
In this case, a basic
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method is set as in a fallback operation and a specific
method may be automatically applied according to
configuration mode.
Association between DL/UL grant DCI formats
DL/UL grant DCI formats which may be transmitted
together via one RB pair may be restricted in consideration
association therebetween. Association may be set according
to various criteria, for example, using a DCI format size.
For example, if DCI format 1 is used in DL grant, DCI format
0 is used in UL grant and, if DCI formats 2 and 2x are used
in DL grant, DCI format 3 (new UL MIMO format) may be used in
UL grant. Therefore, it is possible to substantially equally
maintain the size of DL grant and the size of UL grant. In
particular, since the resource region of the second slot in
which UL grant is present is large, the size of UL grant does
not exceed the size of DL grant.
Error case handling
FIG. 38 shows an error case handling method in FIG. 29.
Referring to FIG. 38, presence/absence of data is indicated
using 1 RA bit and blind decoding is performed with respect
to UL grant.
In this case, in order to accurately indicate
the size of UL grant, an additional bit (Ll/L2, RRC
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signaling) may be used.
FIGs. 39 to 40 show error case handling methods with
reference to FIG. 35.
Referring to FIG. 39, if a DL grant size is M, the
number of cases for placing UL grant may be restricted by
setting a UL grant size N to be less than M. For example, if
a UL grant size is set to 2 (=N) or less (that is, 1 or 2)
when a DL grant size is 3 (=M), it is possible to reduce
blind decoding complexity.
More specifically, as shown,
assuming that an aggregation level of UL grant is 2 CCEs or
less when an aggregation level of DL grant is 3 CCEs, the
number of cases is decreased using (c) or (d) among (a) to
(d) when a signaling or RB bit is 0. Thus, it is possible to
reduce blind decoding complexity.
FIG. 40 shows the case where a transmitter and a
receiver promise to exclude the case in which a signaling bit
(e.g., an RA bit) is 1 (left figure) in FIG. 39 in addition
to restriction of the UL grant size described with reference
to FIG. 39.
In this case, since a relay distinguishes
between only two cases (that is, (c) and (d)), a 1-bit
indication is possible. In other words, it is assumed that,
when a DL grant size is M, a UL grant size N should be less
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than M and the number of cases for placing UL grant is
restricted to two. For example, if a UL grant size is less
than 2 (=N) when a DL grant size is 3 (=M) (that is, 1 or 2),
a 1-bit indication is possible.
Support of "DL grant only case" and "DL grant + UL grant
case"
FIGs. 41 and 42 show other rules for placing an R-
PDCCH/data. In particular, if DL grant and UL grant are
simultaneously present, Method #5 (Alt #5) and Method #8 (Alt
#8) may be applied and, if only DL grant is present (that is,
UL is not present), Method #6 (Alt #6), Method #7 (Alt #7),
Method #9 (Alt #9) and Method #10 (Alt #10) may be applied.
Two cases will be described as follows:
(a) Case in which DL grant is present and UL grant is
always present
(b) Case in which only DL grant is present and UL grant
is not present
Method #5 (Alt #5) and Method #8 (Alt #8) are used in
case of (a) and Method #6 (Alt #6), Method #7 (Alt #7),
Method #9 (Alt #9) and Method #10 (Alt #10) are used in case
of (b). Assuming that (a) and (b) coexist, a set is defined
in advance such that one of the methods applied to (a) is
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used in a specific subframe in which (a) occurs and one of
the methods applied to (b) is used in a specific subframe in
which (b) occurs, and is configured through signaling.
For
example, placement of R-PDCCHs and data is checked according
to Method #5 in case of (a) and placement of R-PDCCHs is
checked according to Method #6 in case of (b). At this time,
Method #5 and Method #6 may be grouped to one set and may be
configured through signaling.
As another method, Mode 1
using only (a) and Mode 2 using both (a) and (b) may be set
and configured through signaling.
In general, in
consideration of symmetric subframe allocation, a possibility
wherein (a) occurs is high.
In a TDD structure, (b) may
frequently occur. In addition, a method of using both Mode 1
(e.g., Method #5) and Mode 2 (e.g., Methods #5 and Method #6)
may be used. Mode 1 and Mode 2 may be automatically applied
according to subframe type. The subframe may be implicitly
checked according to a subframe allocation pattern or a
subframe index. If various methods are applied (e.g., Mode 2
- Method #5 and Method #6) in one mode, Method #5 and Method
#6 may be distinguished in Mode 2 depending on blind decoding.
In Mode 2, Method #5 and Method #6 may be distinguished
through L1/L2 or higher layer signaling or may be implicitly
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checked according to subframe allocation pattern or subframe
index.
Index ordering for maximizing backhaul resources
In the following description, the following assumption
is given in order to use backhaul resources. For description,
it is assumed that R-PDCCH (or relay) groups 0, 1 and 2 are
present. In this case, since a relay assumes that an R-PDCCH
is always present in a first slot of an RB pair in a group
(e.g., the group 1) to which the relay belongs, only a second
slot of the RB pair may be used to transmit the R-PDCCH. If
the R-PDCCH is transmitted using an RB pair of another group
(the group 0 or 2) (that is, if an RA indication is present),
it is assumed that not only the second slot but also the
first slot may be used to transmit the R-PDCCH.
This is
because the relay interprets an RA indication bit while
distinguishing between the group to which the relay belongs
and the group to which the relay does not belong.
FIG. 43 shows an example of placing R-PDCCHs according
to group index order. In FIG. 43, it is assumed that an RBG
is composed of four RBs and a total number of R-PDCCHs is 8.
Referring to FIG. 43, eight R-PDCCHs (RN1 to RN8) may be
contiguously placed from an RB index 0 according to group
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index order (e.g., logical RB index order).
In this case,
RN4 belonging to a group 1 may not use a first slot of an RB
pair belonging to a group 0. This is because RBs (RB indexes
0 to 2) before RN4 of the group 1 are filled with R-PDCCHs of
other RNs (RN1 to RN3).
In this case, the above-described
assumption (that is, the assumption that an R-PDCCH begins to
be transmitted from the first slot if an RA indication is
present in groups other than the group 1 to which RN4
belongs) is not suitable. Accordingly, as shown, a new rule
is necessary if group index ordering is applied.
A group
index ordering method should be decided.
As one method, a high index value may be given to an RN
to which a BS should transmit a relatively large amount of
data (e.g., a group 2).
In contrast, a relatively low index
value may be given to an RN to which a BS should transmit a
relatively small amount of data or an RN to which data is not
transmitted (e.g., a DL grant only case).
At this time, in
order to accurately apply the rule, group index ordering may
be preferentially performed according to the amount of data.
In such alignment, the relay may differently interpret RA
indication bits when resources allocated to an RB index lower
than that of the relay are present and when resources
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allocated to an RB index higher than that of the relay are
present, which are shown in FIGs. 44 to 46.
FIGs. 44 to 46
show different states.
FIG. 44 shows a method of the case in which each RB
means a logical RB and index or the case of allocating
resources in units of one RB.
FIG. 45 shows a method
suitable for the case of allocating resources in RBG units.
FIG. 45 shows the case in which UL grant is separately packed
and is interleaved at a time or in group units having a
predetermined size.
FIG. 44 shows the case in which a second slot of an RB
pair in which DL grant of RN2 is present is empty (e.g., a DL
grant alone case) and the case in which empty resources are
used for RN6. FIG. 44 shows the case in which data for RN6
is transmitted even in an RB pair which is not used by an RN
different from a second slot of an RB pair in which DL grant
of RN6 is present, in addition to the above-described empty
resources. That is, a larger amount of data is transmitted
to RN6 as compared to RN1 or RN2.
This is because it is
assumed that group index ordering is performed according to
the size of data to be transmitted to the relay.
In this
case, RA bit interpretation is differently set. That is, RA
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bits for RBs (RBs of the left direction) present before RN6
indicates only whether data is present in a second slot.
This is because a first slot is occupied by RNs having low
group indexes as in RN2. When the
R-PDSCH of RN6 is
allocated to RBs (RBs of the right direction) greater than an
RB index in which RN6 is present, an RA bit indicates whether
an R-PDCCH is present in both a first slot and a second slot.
That is, the relay may perform decoding on the assumption
that R-PDCCHs are transmitted at the second slot of the PR
pair or all slots in consideration of a group index. The
above assumption may be summarized as follows:
1. If an RA bit indicates data (e.g., (R-)PDSCH)
allocation with respect to RB pair(s) occupied by an R-PDCCH
(or an R-PDCCH group) of a relay and previous R-PDCCH(s) (or
R-PDCCH group(s) in a search space, the relay assumes that DL
grant is transmitted at the first slot of the RB pair and
data thereof is transmitted at the second slot. Accordingly,
the relay performs (R-)PDSCH decoding on the assumption that
data is not transmitted in the first slot of the RB pair.
2. If an RA bit indicates data (e.g., (R-)PDSCH
allocation with respect to RB pair(s) next to the RB pair(s)
occupied by the R-PDCCH of the relay in the search space, the
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relay assumes that data is transmitted in both the first and
second slots of the RB pair. Accordingly, the relay performs
(R-)PDSCH decoding on the assumption that data is transmitted
in both the first and second slots of the RB pair.
According to the present proposal, the relay does not
need to know how many RBs are used by the R-PDCCHs in a given
subframe or how many R-PDCCHs are present.
FIG. 45 shows the case of introducing the RBG concept.
If resources are allocated in RBG units, only PRBs belonging
to the RBG may not be used. As the number of unusable RBs is
increased, the above method enables efficient use of backhaul
resources. FIG. 45 shows the case in which 1 RB of an RBG to
which RN belongs is used for RN2 and R-PDSCHs for RN2 are
transmitted in an RB pair in which an R-PDCCH of the RN as
well as an RBG to which RN2 belongs are not present. In this
case, RA bit interpretation for the RBG index having an index
lower than that of an RBG to which RN2 belongs and RA bit
interpretation for a PRB having an index grater than that of
the RBG to which RN2 belongs are different.
FIG. 46 shows an example of packing UL grant with lower
indexes if UL grant is less than DL grant. By
this
configuration, all RBs except for RBs occupied by UL grant
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may be used for the proposed rule.
The above description focuses upon a relationship
between a BS and an RN, but is equally/similarly applied to a
relationship between an RN and a UE.
For example, in the
above description, a BS may be replaced with an RN and an RN
may be replaced with a UE.
FIG. 47 shows a BS, an RN and a UE to which the present
invention is applicable.
Referring to FIG. 47, a radio communication system
includes a BS 110, an RN 130 and a UE 130. For convenience,
although the UE is connected to the RN, the UE may be
connected to the BS.
The BS 110 includes a processor 112, a memory 114 and a
radio frequency (RF) unit 116. The processor 112 is
configured to implement the procedures and/or methods of the
present invention.
The memory 114 is connected to the
processor 112 so as to store a variety of information
associated with the operation of the processor 112. The RF
unit 116 is connected to the processor 112 so as to transmit
and/or receive an RF signal. The RN 120 includes a processor
122, a memory 124 and a radio frequency (RF) unit 126. The
processor 122 is configured to implement the procedures
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and/or methods of the present invention. The memory 124 is
connected to the processor 122 so as to store a variety of
information associated with the operation of the processor
122. The RF unit 126 is connected to the processor 122 so as
to transmit and/or receive an RF signal. The UE 130 includes
a processor 132, a memory 134 and a radio frequency (RF) unit
136.
The processor 132 is configured to implement the
procedures and/or methods of the present invention.
The
memory 134 is connected to the processor 132 so as to store a
variety of information associated with the operation of the
processor 132. The RF unit 136 is connected to the processor
132 so as to transmit and/or receive an RF signal. The BS
110, the RN 120 and/or the UE 130 may have a single antenna
or multiple antennas.
The aforementioned embodiments are achieved by
combination of structural elements and features of the
present invention in a predetermined manner. Each of the
structural elements or features should be considered
selectively unless specified separately. Each of the
structural elements or features may be carried out without
being combined with other structural elements or features.
Also, some structural elements and/or features may be
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combined with one another to constitute the embodiments of
the present invention. The order of operations described in
the embodiments of the present invention may be changed. Some
structural elements or features of one embodiment may be
included in another embodiment, or may be replaced with
corresponding structural elements or features of another
embodiment. Moreover, it will be apparent that some claims
referring to specific claims may be combined with other
claims referring to the other claims other than the specific
claims to constitute the embodiment or add new claims by
means of amendment after the application is filed.
The embodiments of the present invention are disclosed
on the basis of a data communication relationship among a
base station, an RN and a UE.
Specific operations to be
conducted by the base station in the present invention may
also be conducted by an upper node of the base station as
necessary.
In other words, it will be obvious to those
skilled in the art that various operations for enabling the
base station to communicate with the terminal in a network
composed of several network nodes including the base station
will be conducted by the base station or other network nodes
other than the base station.
The term "Base Station (BS)"
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may be replaced with a fixed station, Node-B, eNode-B (eNB),
or an access point as necessary.
The term "terminal" may
also be replaced with a User Equipment (UE), a Mobile
Station (MS) or a Mobile Subscriber Station (MSS) as
necessary.
The embodiments of the present invention can be
implemented by a variety of means, for example, hardware,
firmware, software, or a combination thereof. In the case of
implementing the present invention by hardware, the present
invention can be implemented with application specific
integrated circuits (ASICs), Digital signal processors (DSPs),
digital signal processing devices (DSPDs), programmable logic
devices (PLDs), field programmable gate arrays (FPGAs), a
processor, a controller, a microcontroller, a microprocessor,
etc.
If operations or functions of the present invention are
implemented by firmware or software, the present invention
can be implemented in the form of a variety of formats, for
example, modules, procedures, functions, etc. Software code
may be stored in a memory unit so that it can be driven by a
processor. The memory unit is located inside or outside of
the processor, so that it can communicate with the
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aforementioned processor via a variety of well-known parts.
It will be apparent to those skilled in the art that
various modifications and variations can be made in the present
invention without departing from the scope of the invention.
Thus, it is intended that the present invention cover the
modifications and variations of this invention provided they
come within the scope of the appended claims and their
equivalents. The scope of the claims should not be limited by
the embodiments set forth herein, but should be given the
broadest interpretation consistent with the description as a
whole.
[Industrial Applicability]
The present invention relates to a radio
communication system and is applicable to a base station, a
relay node and a user equipment.
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