Method and apparatus for efficient feedback in a wireless communication system that supports multiple antennas
The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for efficient feedback in a wireless communication system that supports multiple antennas. A method for transmitting, via an uplink, channel state information for downlink transmission in a wireless communication system according to one embodiment of the present invention, comprises the following steps: receiving a downlink signal via a downlink channel; generating an RI for the downlink channel, selecting a first PMI and a second PMI on the basis of the rank indicated by the generated RI, and calculating a CQI on the basis of precoding information determined by the combination of the selected first and second PMIs; and transmitting the RI, the first PMI, the second PMI, and/or the CQI via an uplink channel, wherein said first PMI and second PMI can be transmitted on different uplink subframes if the uplink channel is a PUCCH.
1. A method for transmitting channel state information on downlink transmission through an uplink in a wireless communication system, the method comprising:
receiving, by a user equipment (UE) from an eNB, a downlink signal through a downlink channel;
generating, by the UE, a rank indicator (RI) corresponding to the downlink channel, selecting a first precoding matrix indicator (PMI) and a second PMI on the basis of a rank indicated by the generated RI, and calculating a channel quality indicator (CQI) on the basis of precoding information determined by a combination of the selected first and second PMIs; and
transmitting, by the UE to the eNB, one or more of the RI, the first PMI, the second PMI and the CQI through an uplink channel,
wherein the first PMI and the second PMI are transmitted in different uplink subframes when the uplink channel corresponds to a physical uplink control channel (PUCCH),
wherein the first PMI indicates precoding matrix candidates applied to the downlink transmission and the second PMI indicates one of the precoding matrix candidates,
wherein each of the first PMI and the second PMI is generated by the UE for the downlink transmission from the eNB to the UE,
wherein a precoding codebook for rank-1 is represented by the following 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
(
i
)
=
1
8
[
v
m
φ
n
v
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
where a value of the first PMI corresponds to i 1 of the precoding codebook, and a value of the second PMI corresponds to i 2 of the precoding codebook.
2. The method according to claim 1 , wherein the first PMI and the second PMI are transmitted in the same uplink subframe when the uplink channel corresponds to a physical uplink shared channel (PUSCH).
3. The method according to claim 1 , wherein a first PMI transmission period is shorter than an RI transmission period and longer than a second PMI transmission period when the uplink channel corresponds to a PUCCH.
4. The method according to claim 1 , wherein, when the uplink channel corresponds to a PUCCH, a predetermined PMI is used as the second PMI when the first PMI and the CQI are transmitted in the same uplink subframe.
5. The method according to claim 4 , wherein the RI is transmitted in a first uplink subframe, a wideband (WB) first PMI and a WB CQI are transmitted in a second uplink subframe following the first uplink subframe, and a subband (SB) second PMI and an SB CQI are transmitted in a third uplink subframe following the second uplink subframe.
6. The method according to claim 1 , wherein a WB CQI for a first codeword, a WB CQI for a second codeword, a WB first PMI, and a WB second PMI are transmitted in the same subframe when the uplink channel corresponds to a PUSCH.
7. The method according to claim 1 , wherein a WB CQI for a first codeword, a selected band CQI for the first codeword, a WB CQI for a second codeword, a selected band CQI for the second codeword, a WB first PMI, a WB second PMI, and a selected band second PMI are transmitted in the same subframe when the uplink channel corresponds to a PUSCH.
8. A method for receiving channel state information on downlink transmission through an uplink in a wireless communication system, the method comprising:
transmitting, by an eNB to a user equipment (UE), a downlink signal through a downlink channel; and
receiving, by the eNB from the UE, through an uplink channel, one or more of a rank indicator (RI) corresponding to the downlink channel, a first precoding matrix indicator (PMI) and a second PMI selected on the basis of a rank indicated by the generated RI, and a channel quality indicator (CQI) calculated on the basis of precoding information determined by a combination of the selected first and second PMIs,
wherein the first PMI and the second PMI are transmitted in different uplink subframes when the uplink channel corresponds to a physical uplink control channel (PUCCH),
wherein the first PMI indicates precoding matrix candidates applied to the downlink transmission and the second PMI indicates one of the precoding matrix candidates,
wherein each of the first PMI and the second PMI is generated by the UE for the downlink transmission from the eNB to the UE,
wherein a precoding codebook for rank-1 is represented by the following table:
i 2
i 1
0
1
2
3
4
5
6
7
0-15
W 2i 1 ,0 (1)
W 2i 1 ,1 (1)
W 2i 1 ,2 (1)
W 2i 1 ,3 (1)
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
12
13
14
15
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)
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
(
i
)
=
1
8
[
v
m
φ
n
v
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
where a value of the first PMI corresponds to i 1 of the precoding codebook, and a value of the second PMI corresponds to i 2 of the precoding codebook.
9. A user equipment (UE) transmitting channel state information on downlink transmission through an uplink in a wireless communication system, the UE comprising:
a reception module for receiving a downlink signal from an eNB;
a transmission module for transmitting an uplink signal to the eNB; and
a processor for controlling the UE including the reception module and the transmission module,
wherein the processor is configured to receive a downlink signal over a downlink channel through the reception module, to generate a rank indicator (RI) corresponding to the downlink channel, to select a first precoding matrix indicator (PMI) and a second PMI on the basis of a rank indicated by the generated RI, and to calculate a channel quality indicator (CQI) on the basis of precoding information determined by a combination of the selected first and second PMIs,
wherein the processor is configured to transmit one or more of the RI, the first PMI, the second PMI and the CQI through an uplink channel,
wherein the first PMI and the second PMI are transmitted in different uplink subframes when the uplink channel corresponds to a physical uplink control channel (PUCCH),
wherein the first PMI indicates precoding matrix candidates applied to the downlink transmission and the second PMI indicates one of the precoding matrix candidates,
wherein each of the first PMI and the second PMI is generated by the UE for the downlink transmission from the eNB to the UE,
wherein a precoding codebook for rank-1 is represented by the following table:
i 2
i 1
0
1
2
3
4
5
6
7
0-15
W 2i 1 ,0 (1)
W 2i 1 ,1 (1)
W 2i 1 ,2 (1)
W 2i 1 ,3 (1)
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
12
13
14
15
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)
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
(
i
)
=
1
8
[
v
m
φ
n
v
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
where a value of the first PMI corresponds to i 1 of the precoding codebook, and a value of the second PMI corresponds to i 2 of the precoding codebook.
10. An eNB receiving channel state information on downlink transmission through an uplink in a wireless communication system, the eNB comprising:
a reception module for receiving an uplink signal from a UE;
a transmission module for transmitting a downlink signal to the UE; and
a processor for controlling the eNB including the reception module and the transmission module,
wherein the processor is configured to transmit the downlink signal over a downlink channel through the transmission module and to receive, through an uplink channel, one or more of a rank indicator (RI) corresponding to the downlink channel, a first precoding matrix indicator (PMI) and a second PMI selected on the basis of a rank indicated by the generated RI, and a channel quality indicator (CQI) calculated on the basis of precoding information determined by a combination of the selected first and second PMIs, through the reception module,
wherein the first PMI and the second PMI are transmitted in different uplink subframes when the uplink channel corresponds to a physical uplink control channel (PUCCH),
wherein the first PMI indicates precoding matrix candidates applied to the downlink transmission and the second PMI indicates one of the precoding matrix candidates,
wherein each of the first PMI and the second PMI is generated by the UE for the downlink transmission from the eNB to the UE,
wherein a precoding codebook for rank-1 is represented by the following table:
i 2
i 1
0
1
2
3
4
5
6
7
0-15
W 2i 1 ,0 (1)
W 2i 1 ,1 (1)
W 2i 1 ,2 (1)
W 2i 1 ,3 (1)
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
12
13
14
15
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)
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
(
i
)
=
1
8
[
v
m
φ
n
v
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
where a value of the first PMI corresponds to i 1 of the precoding codebook, and a value of the second PMI corresponds to i 2 of the precoding codebook.