Method and apparatus for efficient feedback in a wireless communication system supporting multiple antenna
A method for transmitting channel status information (CSI) via uplink in a wireless communication system includes transmitting a first precoding matrix indicator (PMI) and a second PMI at a subframe. A subsampled codebook for each of a precoding codebook for Rank-1 and a precoding codebook for Rank-2 is determined based on at least the first PMI or the second PMI. In case of the Rank-1 or the Rank-2, a number of elements for the first PMI is 8.
1. A method for transmitting channel status information (CSI) via uplink in a wireless communication system, the method comprising:
calculating a first precoding matrix indicator (PMI) and a second PMI; and
transmitting the first PMI and the second PMI at a subframe,
wherein:
a subsampled codebook for each of a precoding codebook for Rank-1 and a precoding codebook for Rank-2 is determined based on at least the first PMI or the second PMI, and
in case of the Rank-1 or the Rank-2, a number of elements for the first PMI is 8.
2. The method according to claim 1 , wherein:
in case of the Rank-1 or the Rank-2, the first PMI indicates one index of a subset having 8 indexes from among 16 indexes of the first PMI of the precoding codebook for Rank-1 or the precoding codebook for Rank-2.
3. The method according to claim 1 , wherein:
a subsampled codebook for each of a precoding codebook for Rank-3 and a precoding codebook for Rank-4 is determined based on at least the first PMI or the second PMI, and
in case of the Rank-3 or the Rank-4, a number of elements for the first PMI is 2.
4. The method according to claim 1 , wherein:
a channel quality indicator (CQI) is transmitted at the subframe at which the first PMI and the second PMI are transmitted; and
a rank indicator (RI) is transmitted at a subframe that is different from the subframe at which the first PMI and the second PMI are transmitted.
5. The method according to claim 2 , wherein:
in case of the Rank-1 or the Rank-2, a number of elements for the second PMI is 2.
6. The method according to claim 3 , wherein:
in case of the Rank-3 or the Rank-4, the first PMI indicates one index of a subset having 2 indexes from among 4 indexes of the first PMI of the precoding codebook for Rank-3 or the precoding codebook for Rank-4.
7. The method according to claim 3 , wherein:
a total bits of the first PMI and the second PMI for each of Rank-1 to Rank-4 is 4 bits.
8. The method according to claim 4 , wherein:
the RI is transmitted over a physical uplink control channel (PUCCH) according to a first report cycle, and
the first PMI, the second PMI, and the CQI are transmitted over a PUCCH according to a second report cycle.
9. The method according to claim 5 , wherein:
in case of the Rank-1 or the Rank-2, the second PMI indicates one index of a subset having 2 indexes from among 16 indexes of the second PMI of the precoding codebook for Rank-1 or the precoding codebook for Rank-2.
10. The method according to claim 6 , wherein:
in case of the Rank-3 or the Rank-4, a number of elements for the second PMI is 8.
11. The method according to claim 9 , wherein:
in case of the Rank-1 or the Rank-2, a size of the first PMI is 3 bits and a size of the second PMI is 1 bit.
12. The method according to claim 9 , wherein the precoding codebook for Rank-1 is represented by the following table:
i 2
0
1
2
3
0-15
W
2
i
1
,
0
(
1
)
W
2
i
1
,
1
(
1
)
W
2
i
1
,
2
(
1
)
W
2
i
1
,
3
(
1
)
i 2
i 1
4
5
6
7
0-15
W
2
i
1
+
1
,
0
(
1
)
W
2
i
1
+
1
,
1
(
1
)
W
2
i
1
+
1
,
2
(
1
)
W
2
i
1
+
1
,
3
(
1
)
i 2
i 1
8
9
10
11
0-15
W
2
i
1
+
2
,
0
(
1
)
W
2
i
1
+
2
,
1
(
1
)
W
2
i
1
2
,
2
(
1
)
W
2
i
1
+
2
,
3
(
1
)
i 2
i 1
12
13
14
15
0-15
W
2
i
1
+
3
,
0
(
1
)
W
2
i
1
+
3
,
1
(
1
)
W
2
i
1
+
3
,
2
(
1
)
W
2
i
1
+
3
,
3
(
1
)
where
W
m
,
n
(
1
)
=
1
8
[
v
m
φ
n
v
m
]
where φ n is denoted by φ n =e jπn/2 and v m is denoted by v m =[1 e j2πm/32 e j4πm/32 e j6πm/32 ] T ,
where values 0 to 15 of i 1 correspond to the 16 indexes of the first PMI,
where values 0 to 15 of i 2 correspond to the 16 indexes of the second PMI, and
in case of the Rank-1, the first PMI indicates an index having a value of any one of 0, 2, 4, 6, 8, 10, 12 or 14, and the second PMI indicates an index having a value of any one of 0 or 2.
13. The method according to claim 9 , wherein the precoding codebook for Rank-2 is represented by the following table:
i 2
i 1
0
1
2
3
0-15
W
2
i
1
,
2
i
1
,
0
(
2
)
W
2
i
1
,
2
i
1
,
1
(
2
)
W
2
i
1
+
1
,
2
i
1
+
1
,
0
(
2
)
W
2
i
1
+
1
,
2
i
1
+
1
,
1
(
2
)
i 2
i 1
4
5
6
7
0-15
W
2
i
1
+
2
,
2
i
1
+
2
,
0
(
2
)
W
2
i
1
+
2
,
2
i
1
+
2
,
1
(
2
)
W
2
i
1
+
3
,
2
i
1
+
3
,
0
(
2
)
W
2
i
1
+
3
,
2
i
1
+
3
,
1
(
2
)
i 2
i 1
8
9
10
11
0-15
W
2
i
1
,
2
i
1
+
1
,
0
(
2
)
W
2
i
1
,
2
i
1
+
1
,
1
(
2
)
W
2
i
1
+
1
,
2
i
1
+
2
,
0
(
2
)
W
2
i
1
+
1
,
2
i
1
+
2
,
1
(
2
)
i 2
i 1
12
13
14
15
0-15
W
2
i
1
,
2
i
1
+
3
,
0
(
2
)
W
2
i
1
,
2
i
1
+
3
,
1
(
2
)
W
2
i
1
+
1
,
2
i
1
+
3
,
0
(
2
)
W
2
i
1
+
1
,
2
i
1
+
3
,
1
(
2
)
where
W
m
,
m
′
,
n
(
2
)
=
1
4
[
v
m
v
m
′
φ
n
v
m
-
φ
n
v
m
′
]
where φ n is denoted by φ n =e jπn/2 and v m is denoted by v m =[1 e j2πm/32 e j4πm/32 e jπm/32 ] T ,
where values 0 to 15 of i 1 correspond to the 16 indexes of the first PMI,
where values 0 to 15 of i 2 correspond to the 16 indexes of the second PMI, and
in case of the Rank-2, the first PMI indicates an index having a value of any one of 0, 2, 4, 6, 8, 10, 12 or 14, and the second PMI indicates an index having a value of any one of 0 or 1.
14. The method according to claim 10 , wherein:
in case of the Rank-3, the second PMI indicates one index of a subset having 8 indexes from among 16 indexes of the second PMI of the precoding codebook for Rank-3 or the precoding codebook for Rank-4.
15. The method according to claim 14 , wherein:
in case of the Rank-3 or the Rank-4, a size of the first PMI is 1 bit, and a size of the second PMI is 3 bits.
16. The method according to claim 14 , wherein the precoding codebook for Rank-3 is represented by the following table:
i 2
i 1
0
1
2
3
0-3
W
8
i
1
,
8
i
1
,
8
i
1
+
8
(
3
)
W
8
i
1
+
8
,
8
i
1
,
8
i
1
+
8
(
3
)
W
~
8
i
1
,
8
i
1
+
8
,
8
i
1
+
8
(
3
)
W
~
8
i
1
+
8
,
8
i
1
,
8
i
1
(
3
)
i 2
i 1
4
5
6
7
0-3
W
8
i
1
+
2
,
8
i
1
+
2
,
4
i
1
+
10
(
3
)
W
8
i
1
+
10
,
8
i
1
+
2
,
8
i
1
+
10
(
3
)
W
~
8
i
1
+
2
,
8
i
1
+
10
,
8
i
1
+
10
(
3
)
W
~
8
i
1
+
10
,
8
i
1
+
2
,
8
i
1
+
2
(
3
)
i 2
i 1
8
9
10
11
0-3
W
8
i
1
+
4
,
8
i
1
+
4
,
8
i
1
+
12
(
3
)
W
8
i
1
+
12
,
8
i
1
+
4
,
8
i
1
+
12
(
3
)
W
~
8
i
1
,
4
,
8
i
1
+
12
,
8
i
1
+
12
(
3
)
W
~
8
i
1
+
12
,
8
i
1
+
4
,
8
i
1
+
4
(
3
)
i 2
i 1
12
13
14
15
0-3
W
8
i
1
+
6
,
8
i
1
+
6
,
8
i
1
+
14
(
3
)
W
8
i
1
+
14
,
8
i
1
+
6
,
8
i
1
+
14
(
3
)
W
~
8
i
1
+
6
,
8
i
1
+
14
,
8
i
1
+
14
(
3
)
W
~
8
i
1
+
14
,
8
i
1
+
6
,
8
i
1
+
6
(
3
)
where
W
m
,
m
′
,
m
″
(
3
)
=
1
24
[
v
m
v
m
′
v
m
″
v
m
-
v
m
′
-
v
m
″
]
,
W
m
,
m
′
,
m
″
(
3
)
=
1
24
[
v
m
v
m
′
v
m
″
v
m
v
m
′
-
v
m
″
]
where φ n is denoted by φ n =e jπn/2 and v m is denoted by v m =[1 e j2πm/32 e j4πm/32 e j6πm/32 ] T ,
where values 0 to 3 of i 1 correspond to the 4 indexes of the first PMI,
where values 0 to 15 of i 2 correspond to the 16 indexes of the second PMI, and
in case of the Rank-3, the first PMI indicates an index having a value of any one of 0 or 2, and the second PMI indicates an index having a value of any one of 0, 1, 2, 3, 8, 9, 10 or 11.
17. The method according to claim 14 , wherein the precoding codebook for Rank-4 is represented by the following table:
i 2
i 1
0
1
2
3
0-3
W
8
i
1
,
8
i
1
+
8
,
0
(
4
)
W
8
i
1
,
8
i
1
+
8
,
1
(
4
)
W
8
i
1
+
2
,
8
i
1
+
10
,
0
(
4
)
W
8
i
1
+
2
,
8
i
1
+
10
,
1
(
4
)
i 2
i 1
4
5
6
7
0-3
W
8
i
1
+
4
,
8
i
1
+
12
,
0
(
4
)
W
8
i
1
+
4
,
8
i
1
+
12
,
1
(
4
)
W
8
i
1
+
6
,
8
i
1
+
14
,
0
(
4
)
W
8
i
1
+
6
,
8
i
1
+
14
,
1
(
4
)
where
W
m
,
m
′
,
n
(
4
)
=
1
32
[
v
m
v
m
′
v
m
v
m
′
φ
n
v
m
φ
n
v
m
′
-
φ
n
v
m
-
φ
n
v
m
′
]
where φ n is denoted by φ n =e jπn/2 and v m is denoted by v m =[1 e j2πm/32 e j4πm/32 e j6πm/32 ] T ,
where values 0 to 3 of i 1 correspond to the 4 indexes of the first PMI,
where values 0 to 7 of i 2 correspond to the 8 indexes of the second PMI, and
in case of the Rank-4, the first PMI indicates an index having a value of any one of 0 or 2, and the second PMI indicates an index having a value of any one of 0, 1, 2, 3, 4, 5, 6 or 7.
18. A method for receiving channel status information (CSI) via uplink in a wireless communication system, the method comprising:
receiving a first precoding matrix indicator (PMI) and a second PMI at a subframe; and
determining a precoding matrix based on the received first PMI and the received second PMI
wherein:
a subsampled codebook for each of a precoding codebook for Rank-1 and a precoding codebook for Rank-2 is determined based on at least the first PMI or the second PMI, and
in case of the Rank-1 or the Rank-2, a number of elements for the first PMI is 8.
19. A user equipment (UE) for transmitting channel status information (CSI) 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 is configured to calculate a first precoding matrix indicator (PMI) and a second PMI and to control the transmission module to transmit the first PMI and the second PMI at a subframe,
wherein:
a subsampled codebook for each of a precoding codebook for Rank-1 and a precoding codebook for Rank-2 is determined based on at least the first PMI or the second PMI, and
in case of the Rank-1 or the Rank-2, a number of elements for the first PMI is 8.
20. A base station (BS) for receiving channel status information (CSI) 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 is configured to control the reception module to receive a first precoding matrix indicator (PMI) and a second PMI at a subframe and to determine a precoding matrix based on the received first PMI and the received second PMI,
wherein:
a subsampled codebook for each of a precoding codebook for Rank-1 and a precoding codebook for Rank-2 is determined based on at least the first PMI or the second PMI, and
in case of the Rank-1 or the Rank-2, a number of elements for the first PMI is 8.