Codebook sub-sampling for CSI feedback on PUCCH for 4Tx MIMO
Channel state information (CSI) feedback in a wireless communication system is disclosed. User equipment transmits a CSI feedback signal via a Physical Uplink Control CHannel (PUCCH). If the UE is configured in a first feedback mode, the CSI comprises a first report jointly coding a Rank Indicator (RI) and a first precoding matrix indicator (PMI1), and a second report coding Channel Quality Indicator (CQI) and a second precoding matrix indicator (PMI2). If the UE is configured in a second feedback mode, the CSI comprises a first report coding RI, and a second report coding CQI, PMI1 and PMI2. The jointly coded RI and PMI1 employs codebook sub-sampling, and the jointly coding PMI1, PMI2 and CQI employs codebook sub-sampling.
1. A method of channel state information (CSI) feedback between a base station and at least a user equipment, comprising:
transmitting, by the user equipment, a CSI feedback signal having:
a first report coding a Rank Indicator (RI), and
a second report coding a first precoding matrix indicator (PMI1) associated with the index of a first precoding matrix (W1), a second precoding matrix indicator (PMI2) associated with the index of a second precoding matrix (W2), and a Channel Quality Indicator (CQI), and
wherein coding the PMI2 employs codebook sub-sampling as follows, for RI=3 and 4:
Relationship between the second
PMI value and W2 index (i 2 )
Value of the
Chosen W2 index
second PMI
for sub-sampling
RI
(I PMI2 )
(i 2 )
3
0-15
I PMI2
4
0-15
I PMI2 .
2. The method of claim 1 , wherein indices of precoding matrices W1 and W2 are jointly encoded with CQI.
3. The method of claim 1 , wherein the index of W1 is jointly encoded with the index of W2.
4. The method of claim 1 , wherein indicators PMI1 and PMI2 are jointly encoded with CQI.
5. The method of claim 1 , wherein PMI1 is jointly encoded with PMI2.
6. The method of claim 1 , wherein the transmitted first and second reports comprise a CSI feedback signal.
7. The method of claim 6 , wherein the CSI feedback signal is transmitted in a Physical Uplink Control CHannel (PUCCH) transmission.
8. The method of claim 1 , wherein coding the PMI1 employs codebook sub-sampling as follows, for RI=3 and 4:
Relationship between the first PMI
value and W1 index (i 1 )
Value of the first
Chosen W1 index
PMI
for sub-sampling
RI
(I PMI1 )
(i 1 )
3
0
0
4
0
0.
9. A user equipment (UE), for transmitting channel state information (CSI) feedback, comprising:
circuitry for generating a first report comprising a Rank Indicator (RI);
circuitry for generating a second report comprising a first precoding matrix indicator (PMI1) associated with the index of a first precoding matrix (W1), a second precoding matrix indicator (PMI2) associated with the index of a second precoding matrix (W2), and a Channel Quality Indicator (CQI),
wherein coding the PMI2 employs codebook sub-sampling as follows, for RI=3 and 4:
Relationship between the second
PMI value and W2 index (i 2 )
Value of the
Chosen W2 index
second PMI
for sub-sampling
RI
(I PMI2 )
(i 2 )
3
0-15
I PMI2
4
0-15
I PMI2 ;
and
circuitry for transmitting the first and second reports.
10. The UE of claim 9 , wherein indices of precoding matrices W1 and W2 are jointly encoded with CQI.
11. The UE of claim 9 , wherein the index of W1 is jointly encoded with the index of W2.
12. The UE of claim 9 , wherein indicators PMI1 and PMI2 are jointly encoded with CQI.
13. The HE of claim 9 , wherein PMI1 is jointly encoded with PMI2.
14. The UE of claim 9 , wherein the transmitted first and second reports comprise a CSI feedback signal.
15. The UE of claim 14 , wherein the CSI feedback signal is transmitted in a Physical Uplink Control CHannel (PUCCH) transmission.
16. The UE of claim 9 , wherein coding the PMI1 employs codebook sub-sampling as follows, for RI=3 and 4:
Relationship between the first PMI
value and W1 index (i 1 )
Value of the first
Chosen W1 index
PMI
for sub-sampling
RI
(I PMI1 )
(i 1 )
3
0
0
4
0
0.