Method and apparatus for transmitting precoding martrix index and performing precoding
A method and an apparatus for sending a Precoding Matrix Index (PMI) and performing precoding are provided in the embodiments of the present invention. The method for sending the PMI comprises the following steps: a user equipment acquires the transmission channel capability of carrying the PMI; according to the transmission channel capability of carrying the PMI, the precoding matrices are selected from a locally-stored first codebook set to form a second codebook set; a first precoding matrix is selected from the second codebook set; an index corresponding to the first precoding matrix is sent to a base station over the transmission channel so as to make the base station can find out the first precoding matrix according to the index and precode the data according to the first precoding matrix. The embodiments of the present invention can realize the flexible configuration and use of the PMI.
1. A method for transmitting precoding matrix index (PMI), comprising:
selecting a first precoding matrix from a second codebook set by a user equipment (UE), wherein the second codebook set is selected from a first codebook set locally stored on the UE according to a capability of a transmission channel to carry PMI;
transmitting, by the UE, an index item corresponding to the first precoding matrix to a base station (BS) over the transmission channel, so as to enable the BS to search for the first precoding matrix according to the index item and perform precoding on data according to the first precoding matrix.
2. The method according to claim 1 , wherein that the second codebook set is a complete or a subset of the first codebook set locally stored on the UE.
3. The method according to claim 2 , wherein, when the second codebook set is a subset of the first codebook set, the second codebook set meets a criteria of uniformly partitioning the signal space.
4. The method according to claim 2 , wherein each precoding matrix in the first codebook set locally stored is represented as W=W 1 W 2 ,
W
1
=
(
DA
0
0
DA
Λ
)
,
W
2
=
(
1
X
)
,
wherein,
W 1 is a N t ×2R matrix,
W 2 is a 2R×R matrix,
I is a R×R identity matrix,
X is a R×R diagonal matrix,
D is a N t /2×N t /2 diagonal matrix,
A is a N t /2×R matrix,
Λ is a R×R diagonal matrix,
wherein N t is an even and represents the number of transmission antennas of the BS, R is the rank of the precoding matrix.
5. The method according to claim 4 , wherein, when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes, the method comprises:
representing Λ with 1 bit having a value range of 1 or −1.
6. The method according to claim 4 , wherein, when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes, the method comprises:
representing 8 uniform directions by A with 3 bits.
7. A method for precoding, comprising:
receiving, by a base station (BS), an index item corresponding to a first precoding matrix transmitted by a user equipment (UE) over a transmission channel, wherein the first precoding matrix is selected from a second codebook set by the UE, and the second codebook set is selected from a first codebook set locally stored on the UE according to the capability of the transmission channel to carry PMI;
searching for, by the BS, the first precoding matrix in a third codebook set locally stored according to the index item, and performing precoding on data according to the first precoding matrix, wherein the third codebook set is identical to the second codebook set.
8. The method according to claim 7 , wherein the second codebook set is a complete or a subset of the first codebook set locally stored on the UE.
9. The method according to claim 8 , wherein, when the second codebook set is a subset of the first codebook set, the second codebook set meets a criteria of uniformly partitioning the signal space.
10. The method according to claim 8 , wherein each precoding matrix in the first codebook set is represented as W=W 1 W 2 ,
W
1
=
(
DA
0
0
DA
Λ
)
,
W
2
=
(
1
X
)
,
wherein,
W 1 is a N t ×2R matrix,
W 2 is a 2R×R matrix,
I is a R×R identity matrix,
X is a R×R diagonal matrix,
D is a N t /2×N, /2 diagonal matrix,
A is a N t /2×R matrix,
Λ is a R×R diagonal matrix,
wherein N t is an even and represents the number of transmission antennas of the BS, R is the rank of the precoding matrix.
11. The method according to claim 10 , wherein, when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes, the method comprises:
representing Λ with 1 bit having a value range of 1 or −1.
12. The method according to claim 10 , wherein, when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes, the method comprises:
representing 8 uniform directions by A with 3 bits.
13. A user equipment (UE), comprising:
a selecting unit, configured to select a first precoding matrix from a second codebook set, wherein the second codebook set is selected from a first codebook set locally stored on the UE according to a capability of a transmission channel to carry PMI;
a transmitting unit, configured to transmit an index item corresponding to the first precoding matrix to a base station (BS) over the transmission channel, so as to enable the BS to search for the first precoding matrix according to the index item, and perform precoding on data according to the first precoding matrix.
14. The UE according to claim 13 , wherein the second codebook set is a complete or a subset of the first codebook set locally stored on the UE.
15. The UE according to claim 14 , wherein, when the second codebook set is a subset of the first codebook set, the second codebook set meets a criteria of uniformly partitioning the signal space.
16. The UE according to claim 14 , wherein, each precoding matrix in the first codebook set is represented as W=W 1 W 2 ,
W
1
=
(
DA
0
0
DA
Λ
)
,
W
2
=
(
1
X
)
,
wherein,
W 1 is a N t ×2R matrix,
W 2 is a 2R×R matrix,
I is a R×R identity matrix,
X is a R×R diagonal matrix,
D is a N t /2×N t /2 diagonal matrix,
A is a N t /2×R matrix,
Λ is a R×R diagonal matrix,
wherein N t is an even and represents the number of transmission antennas of the BS, R is the rank of the precoding matrix.
17. The UE according to claim 16 , wherein, when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes, the matrix Λ is represented with 1 bit having a value range of 1 or −1.
18. The UE according to claim 16 , wherein, when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes,
eight uniform directions are represented by A with 3 bits.
19. A base station (BS), comprising:
a receiving unit, configured to receive an index item corresponding to a first precoding matrix transmitted by a user equipment (UE) over a transmission channel, wherein the first precoding matrix is selected from a second codebook set by the UE, and the second codebook set is selected from a first codebook set locally stored on the UE according to a capability of the transmission channel to carry PMI;
a precoding unit, configured to search for the first precoding matrix in a third codebook set locally stored by the BS according to the index item received by the receiving unit, and perform precoding on data according to the first precoding matrix, wherein the third codebook set is identical to the second codebook set.
20. The BS according to claim 19 , wherein the second codebook set is a complete or a subset of the first codebook set locally stored for the UE.
21. The BS according to claim 20 , wherein, when the second codebook set is a subset of the first codebook set, the second codebook set meets a criteria of uniformly partitioning the signal space.
22. The BS according to claim 20 , wherein each precoding matrix in the first codebook set is represented as W=W 1 W 2 ,
W
1
=
(
DA
0
0
DA
Λ
)
,
W
2
=
(
1
X
)
,
wherein,
W 1 is a N t ×2R matrix,
W 2 is a 2R×R matrix,
I is a R×R identity matrix,
X is a R×R diagonal matrix,
D is a N t /2×N t /2 diagonal matrix,
A is a N t /2×R matrix,
Λ is a R×R diagonal matrix,
wherein N t is an even and represents the number of transmission antennas of the BS, R is the rank of the precoding matrix.
23. The BS according to claim 22 , characterized in that
when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes, the matrix Λ is represented with 1 bit having a value range of 1 or −1.
24. The BS according to claim 22 , characterized in that when the rank is 1, the second codebook set is a subset of the first codebook set, and D and X are identity matrixes,
eight uniform directions are represented by A with 3 bits.