Method and apparatus for efficient feedback in a wireless communication system supporting multiple antennas
A method and apparatus for performing effective feedback in a wireless communication system supporting multiple antennas. A method for transmitting CSI of downlink transmission via uplink in a wireless communication system includes transmitting a joint-coded rank indicator (RI) and a first wideband (WB) precoding matrix indicator (PMI) at a first subframe, and transmitting a wideband channel quality indicator (WB CQI) and a second WB PMI at a second subframe. A user equipment (UE) preferred precoding matrix is indicated by a combination of the first PMI and the second PMI. If the RI is Rank-1 or Rank-2, the first PMI indicates one of subsets each having 8 indexes from among 16 indexes of the first PMI of a precoding codebook.
1. A method for transmitting channel status information (CSI) of downlink transmission via uplink in a wireless communication system, the method comprising:
transmitting a joint-coded rank indicator (RI) and a first wideband (WB) precoding matrix indicator (PMI) at a first subframe; and
transmitting a wideband channel quality indicator (WB CQI) and a second WB PMI at a second subframe;
wherein a user equipment (UE) preferred precoding matrix is indicated by a combination of the first WB PMI and the second WB PMI, and
if an RI of the joint-coded RI and the first WB PMI is Rank-1 or Rank-2, the first WB PMI of the joint-coded RI and the first WB PMI indicates one index of a subset having 8 indexes from among 16 indexes of the first WB PMI of a precoding codebook.
2. The method according to claim 1 , wherein the 8 indexes contained in the subset of the first WB PMI in the precoding codebook are indexes other than overlapped beams from among beams generated by a precoding matrix applied to the downlink transmission.
3. The method according to claim 1 , wherein:
if the precoding codebook for the Rank-1 is represented by the following table:
TABLE
i 2
i 1
0
1
2
3
0-15
W 2i 1 ,0 (1)
W 2i 1 ,1 (1)
W 2i 1 ,2 (1)
W 2i 1 ,3 (1)
i 2
i 1
4
5
6
7
0-15
W 2i 1 +1,0 (1)
W 2i 1 +1,1 (1)
W 2i 1 +1,2 (1)
W 2i 1 +1,3 (1)
i 2
i 1
8
9
10
11
0-15
W 2i 1 +2,0 (1)
W 2i 1 +2,1 (1)
W 2i 1 +2,2 (1)
W 2i 1 +2,3 (1)
i 2
i 1
12
13
14
15
0-15
W 2i 1 +3,0 (1)
W 2i 1 +3,1 (1)
W 2i 1 +3,2 (1)
W 2i 1 +3,3 (1)
where
W
m
,
n
(
1
)
=
1
8
[
ν
m
φ
n
ν
m
]
where φ n is denoted by φ n =e jπn/2 and ν m is denoted by ν m =[1 e j2πm/32 e j4πn/32 e j6πm/32 ] T , and and
if the precoding codebook for the Rank-2 is represented by the following table:
TABLE
i 2
i 1
0
1
2
3
0-15
W 2i 1 ,2i 1 ,0 (2)
W 2i 1 ,2i 1 ,1 (2)
W 2i 1 +1,2i 1 +1,0 (2)
W 2i 1 +1,2i 1 +1,1 (2)
i 2
i 1
4
5
6
7
0-15
W 2i 1 +2,2i 1 +2,0 (2)
W 2i 1 +2,2i 1 +2,1 (2)
W 2i 1 +3,2i 1 +3,0 (2)
W 2i 1 +3,2i 1 +3,1 (2)
i 2
i 1
8
9
10
11
0-15
W 2i 1 ,2i 1 +1,0 (2)
W 2i 1 ,2i 1 +1,1 (2)
W 2i 1 +1,2i 1 +2,0 (2)
W 2i 1 +1,2i 1 +2,1 (2)
i 2
i 1
12
13
14
15
0-15
W 2i 1 ,2i 1 +3,0 (2)
W 2i 1 ,2i 1 +3,1 (2)
W 2i 1 +1,2i 1 +3,0 (2)
W 2i 1 +1,2i 1 +3,1 (2)
where
W
m
,
m
′
,
n
(
2
)
=
1
4
[
ν
m
ν
m
′
φ
n
ν
m
-
φ
n
ν
m
′
]
where φ n is denoted by n =e jπn/2 and ν m is denoted by ν m =[1 e j2πm/32 e j4πm/32 e j6πm/32 ] T ,
the first WB PMI is set to any one of 0, 2, 4, 6, 8, 10, 12, or 14,
values 0 to 15 i 1 corresponds to the 16 indexes of the first WB PMI, and
values 0 to 15 i 2 corresponds to 16 indexes of the second WB PMI.
4. The method according to claim 1 , wherein the second WB PMI indicates one of 16 indexes of the second WB PMI in the precoding codebook.
5. The method according to claim 1 , wherein:
the joint-coded RI and the first WB PMI are transmitted over a physical uplink control channel (PUCCH) of the first subframe; and
the WB CQI and the second WB PMI are transmitted over a PUCCH of the second subframe.
6. The method according to claim 1 , wherein the RI, the first WB PMI, the second WB PMI, and the WB CQI are contained in the CSI of downlink 8 transmission (Tx) antennas.
7. The method according to claim 1 , wherein:
the joint-coded RI and the first WB PMI are transmitted according to a first report cycle; and
the WB CQI and the second WB PMI are transmitted according to a second report cycle.
8. A method for receiving channel status information (CSI) of downlink transmission via uplink in a wireless communication system, the method comprising:
receiving a joint-coded rank indicator (RI) and a first wideband (WB) precoding matrix indicator (PMI) at a first subframe; and
receiving a wideband channel quality indicator (WB CQI) and a second WB PMI at a second subframe,
wherein a user equipment (UE) preferred precoding matrix is indicated by a combination of the first WB PMI and the second WB PMI, and
if an RI of the joint-coded RI and the first WB PMI is Rank-1 or Rank-2, the first WB PMI of the joint-coded RI and the first WB PMI indicates one index of a subset having 8 indexes from among 16 indexes of the first WB PMI of a precoding codebook.
9. The method according to claim 8 , wherein the 8 indexes contained in the subset of the first WB PMI in the precoding codebook are indexes other than overlapped beams from among beams generated by a precoding matrix applied to the downlink transmission.
10. The method according to claim 8 , wherein:
if the precoding codebook for the Rank-1 is represented by the following table:
TABLE
i 2
i 1
0
1
2
3
0-15
W 2i 1 ,0 (1)
W 2i 1 ,1 (1)
W 2i 1 ,2 (1)
W 2i 1 ,3 (1)
i 2
i 1
4
5
6
7
0-15
W 2i 1 +1,0 (1)
W 2i 1 +1,1 (1)
W 2i 1 +1,2 (1)
W 2i 1 +1,3 (1)
i 2
i 1
8
9
10
11
0-15
W 2i 1 +2,0 (1)
W 2i 1 +2,1 (1)
W 2i 1 +2,2 (1)
W 2i 1 +2,3 (1)
i 2
i 1
12
13
14
15
0-15
W 2i 1 +3,0 (1)
W 2i 1 +3,1 (1)
W 2i 1 +3,2 (1)
W 2i 1 +3,3 (1)
where
W
m
,
n
(
1
)
=
1
8
[
ν
m
φ
n
ν
m
]
where φ n is denoted by φ n =e jπn/2 and ν m is denoted by ν m =[1 e j2πm/32 e j4πm/32 e j6πm/32 ] T , and and
if the precoding codebook for the Rank-2 is represented by the following table:
TABLE
i 2
i 1
0
1
2
3
0-15
W 2i 1 ,2i 1 ,0 (2)
W 2i 1 ,2i 1 ,1 (2)
W 2i 1 +1,2i 1 +1,0 (2)
W 2i 1 +1,2i 1 +1,1 (2)
i 2
i 1
4
5
6
7
0-15
W 2i 1 +2,2i 1 +2,0 (2)
W 2i 1 +2,2i 1 +2,1 (2)
W 2i 1 +3,2i 1 +3,0 (2)
W 2i 1 +3,2i 1 +3,1 (2)
i 2
i 1
8
9
10
11
0-15
W 2i 1 ,2i 1 +1,0 (2)
W 2i 1 ,2i 1 +1,1 (2)
W 2i 1 +1,2i 1 +2,0 (2)
W 2i 1 +1,2i 1 +2,1 (2)
i 2
i 1
12
13
14
15
0-15
W 2i 1 ,2i 1 +3,0 (2)
W 2i 1 ,2i 1 +3,1 (2)
W 2i 1 +1,2i 1 +3,0 (2)
W 2i 1 +1,2i 1 +3,1 (2)
where
W
m
,
m
′
,
n
(
2
)
=
1
4
[
ν
m
ν
m
′
φ
n
ν
m
-
φ
n
ν
m
′
]
where φ n is denoted by φ n =e jπn/2 and ν m is denoted by ν m [1 e j2πn/32 e j4πm/32 e j6πm/32 ] T ,
the first WB PMI is set to any one of 0, 2, 4, 6, 8, 10, 12, or 14,
values 0 to 15 of i 1 corresponds to the 16 indexes of the first WB PMI, and
values 0 to 15 of i 2 corresponds to the 16 indexes of the second WB PMI.
11. The method according to claim 8 , wherein the second WB PMI indicates one of 16 indexes of the second WB PMI in the precoding codebook.
12. The method according to claim 8 , wherein:
the joint-coded RI and the first WB PMI are transmitted over a physical uplink control channel (PUCCH) of the first subframe; and
the WB CQI and the second WB PMI are transmitted over a PUCCH of the second subframe.
13. The method according to claim 8 , wherein the RI, the first WB PMI, the second WB PMI, and the WB CQI are contained in the CSI of downlink 8 transmission (Tx) antennas.
14. The method according to claim 8 , wherein:
the joint-coded RI and the first WB PMI are transmitted according to a first report cycle; and
the WB CQI and the second WB PMI are transmitted according to a second report cycle.
15. A user equipment (UE) for transmitting channel status information (CSI) of downlink transmission via uplink in a wireless communication system, the UE comprising:
a reception module for receiving a downlink signal from a base station (BS);
a transmission module for transmitting an uplink signal to the BS; and
a processor for controlling the UE including the reception module and the transmission module,
wherein:
the processor causes the transmission module to transmit a joint-coded rank indicator (RI) and a first wideband (WB) precoding matrix indicator (PMI) at a first subframe, and to transmit a wideband channel quality indicator (WB CQI) and a second WB PMI at a second subframe;
a UE preferred precoding matrix is indicated by a combination of the first WB PMI and the second WB PMI; and
if an RI of the joint-coded RI and the first WB PMI is Rank-1 or Rank-2, the first WB PMI of the joint-coded RI and the first WB PMI indicates one index of a subset having 8 indexes from among 16 indexes of the first WB PMI of a precoding codebook.
16. A base station (BS) for receiving channel status information (CSI) of downlink transmission via uplink in a wireless communication system, the BS comprising:
a reception module for receiving an uplink signal from a user equipment (UE);
a transmission module for transmitting a downlink signal to the UE; and
a processor for controlling the BS including the reception module and the transmission module,
wherein:
the processor causes the reception module to receive a joint-coded rank indicator (RI) and a first wideband (WB) precoding matrix indicator (PMI) at a first subframe, and to receive a wideband channel quality indicator (WB CQI) and a second WB PMI at a second subframe;
a UE preferred precoding matrix is indicated by a combination of the first WB PMI and the second WB PMI; and
if an RI of the joint-coded RI and the first WB PMI is Rank-1 or Rank-2, the first WB PMI of the joint-coded RI and the first WB PMI indicates one index of a subset having 8 indexes from among 16 indexes of the first WB PMI of a precoding codebook.