Method for reporting channel state information, user equipment, and base station

1. A method for reporting channel state information, the method comprising:

receiving, by a user equipment (UE), a reference signal sent by a base station;

selecting, by the UE, based on the reference signal, a precoding matrix from a codebook, wherein a precoding matrix W comprised in the codebook is a product of three matrices w 1 , Z, and w 2 , wherein w=w 1 zw 2 , both w 1 and Z are block diagonal matrices, W 1 =diag{X 1 ,X 2 }, Z=diag{Z 1 , Z 2 }, and each column of each block matrix z i in the matrix Z has the following structure:

z i,k =(α i,k 2 +β i,k 2 ) 1/2 [α i,k e i,k T β i,k e jθ i,k e i,k T ] T

wherein i is an index variable of the block matrix Z i ; k is an index variable of the column z i,k ; [ ] T denotes matrix transpose; e i,k denotes an n i x1 selection vector, wherein in the vector, the k th element is 1 and all other elements are 0, and n i is a half of the number of columns of a matrix x i ; θ i,k is a phase shift, α i,k ≧0, and β i,k ≧0; w 2 is used to select one or more column vectors in the matrix W 1 Z and to perform a weighting combination to form the matrix W; and

sending, by the UE, a precoding matrix indicator (PMI) to the base station, wherein the PMI corresponds to the selected precoding matrix, and is used by the base station to obtain the selected precoding matrix W according to the PMI.

2. The method according to claim 1 , wherein the matrix X 1 and the matrix X 2 are equivalent.

3. The method according to claim 1 , wherein the matrix Z 1 and the matrix Z 2 are equivalent.

4. The method according to claim 1 , wherein the matrix W 1 satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein each column of the matrix X 1,1 and each column of the matrix X 1,2 are orthogonal to each other;

X 2 =[X 2,1 , X 2,2 ] wherein each column of the matrix X 2,1 and each column of the matrix X 2,2 are orthogonal to each other.

5. The method according to claim 1 , wherein the matrix W 1 satisfies at least one of the following:

[X 1,1 , X 1,2 ], wherein the matrix X 1,1 is a Kronecker product of matrices A 1,1 and B 1,1 , and X 1,2 is a Kronecker product of matrices A 1,2 and B 1,2 , wherein each column of the A 1,1 , the B 1,1 , the A 1,2 , and the B 1,2 is a DFT vector;

X 1 =[X 2,1 ,X 2,2 ], wherein the matrix X 2,1 is a Kronecker product of matrices A 2,1 and B 2,1 , and X 1,2 is a Kronecker product of matrices A 2,2 and B 2,2 wherein each column of the A 2,1 , the B 2,1 , the A 2,2 , and the B 2,2 is a DFT vector.

6. The method according to claim 1 , wherein sending a precoding matrix indicator (PMI) to the base station comprises:

sending a first PMI (PMI 1 ) and a second PMI (PMI 2 ) to the base station, wherein the PMI 1 is used to indicate the matrix w 1 z, and the PMI 2 is used to indicate the matrix w 2 .

7. The method according to claim 1 , wherein:

the matrix W 2 is used for column selection from W 1 Z 1 to form the matrix W; or

the matrix W 2 is used for weighted combination of the columns of W 1 Z 1 to form the matrix W.

8. A method for reporting channel state information, the method comprising:

sending, by a base station, a reference signal to user equipment (UE);

receiving, by the base station, a precoding matrix indicator (PMI) sent by the UE; and

determining, by the base station, a precoding matrix W in a codebook according to the PMI, wherein the precoding matrix W is a product of three matrices w 1 , Z, and w 2 , w=w 1 zw 2 , both w 1 and Z are block diagonal matrices, W 1 =diag{X 1 ,X 2 }, Z=diag{Z 1 , Z 2 }, and each column of each block matrix z, in the matrix Z has the following structure:

z i,k =(α i,k 2 +β i,k 2 ) 1/2 [α i,k e i,k T β i,k e jθ i,k e i,k T ]

wherein i is an index variable of the block matrix Z i : k is an index variable of the column z i,k ; [ ] T denotes matrix transpose; e i,k denotes an n i x1 selection vector, wherein in the vector, the k th element is 1 and all other elements are 0, and n i is a half of the number of columns of a matrix x i ; θ i,k is a phase shift, α i,k ≧0, and β i,k ≧0; w 2 is used to select one or more column vectors in the matrix W 1 Z and to perform a weighting combination to form the matrix W.

9. The method according to claim 8 , wherein the matrix X 1 and the matrix X 2 are equivalent.

10. The method according to claim 8 , wherein the matrix Z i and the matrix Z 2 are equivalent.

11. The method according to claim 8 , wherein the matrix W 1 satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein each column of the matrix X 1,1 and each column of the matrix X 1,2 are orthogonal to each other;

X 2 =[X 2,1 ,X 22 ] wherein each column of the matrix X 2,1 and each column of the matrix X 2,2 are orthogonal to each other.

12. The method according to claim 8 , wherein the matrix W i satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein the matrix X 1,1 is a Kronecker product of matrices A 1,1 and B 1,1 , and X 1,2 is a Kronecker product of matrices A 1,2 and B 1,2 , wherein each column of the A 1,1 , the B 1,1 , the A 1,2 , and the B 1,2 is a DFT vector;

X 1 =[X 2,1 ,X 2,2 ], wherein the matrix X 2,1 is a Kronecker product of matrices A 2,1 and B 2,1 , and X 1,2 is a Kronecker product of matrices A 2,2 and B 2,2 , wherein each column of the A 2,1 , the B 2,1 , the A 2,2 , and the B 2,2 is a DFT vector.

13. The method according to claim 8 , wherein receiving a PMI sent by the UE comprises:

receiving a first PMI (PMI 1 ) and a second PMI (PMI 2 ) sent by the UE, wherein the PMI 1 is used to indicate the matrix w 1 z, and the PMI 2 is used to indicate the matrix w 2 .

14. The method according to claim 8 , wherein:

the matrix W 2 is used for column selection from W 1 Z 1 to form the matrix W; or

the matrix W 2 is used for weighted combination of the columns of W 1 Z 1 to form the matrix W.

15. User equipment (UE) comprising:

a receiver, configured to receive a reference signal sent by a base station;

a processor, configured to select, based on the reference signal, a precoding matrix from a codebook, wherein a precoding matrix W comprised in the codebook is a product of three matrices being w 1 , Z, and w 2 , w=w 1 zw 2 , both w 1 and Z are block diagonal matrices, w 1 =diag{X 1 ,X 2 }Z=diag{Z 1 ,Z 2 }, and each column of each block matrix z, in the matrix Z has the following structure:

z i,k =(α i,k 2 +β i,k 2 ) 1/2 [α i,k e i,k T β i,k e jθ i,k e i,k T ] T

wherein i is an index variable of the block matrix Z i ; k is an index variable of the column z i,k ; [ ] T denotes matrix transposition; e i,k denotes an n i x1 selection vector, wherein in the vector, the k th element is 1 and all other elements are 0, and n i is a half of the number of columns of a matrix x i ; θ i,k is a phase shift, α i,k ≧0, and β i,k ≧0; w 2 is used to select one or more column vectors in the matrix W 1 Z and to perform a weighting combination to form the matrix W; and

a transmitter, configured to send a precoding matrix indicator (PMI) to the base station, wherein the PMI corresponds to the selected precoding matrix, and is used by the base station to obtain the selected precoding matrix W according to the PMI.

16. The method according to claim 15 , wherein the matrix X 1 and the matrix X 2 are equivalent.

17. The method according to claim 15 , wherein the matrix Z 1 and the matrix Z 2 are equivalent.

18. The method according to claim 15 , wherein the matrix W 1 satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein each column of the matrix X 1,1 and each column of the matrix X 1,2 are orthogonal to each other;

X 2 =[X 2,1 ,X 2,2 ] wherein each column of the matrix X 2,1 and each column of the matrix X 2,2 are orthogonal to each other.

19. The method according to claim 15 , wherein the matrix W 1 satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein the matrix X 1,1 is a Kronecker product of matrices A 1,1 and B 1,1 , and X 1,2 is a Kronecker product of matrices A 1,2 and B 1,2 , wherein each column of the A 1,1 , the B 1,1 , the A 1,2 , and the B 1,2 is a DFT vector;

X 1 =[X 2,1 ,X 2,2 ], wherein the matrix X 2,1 is a Kronecker product of matrices A 2,1 and B 2,1 , and X 1,2 is a Kronecker product of matrices A 2,2 and B 2,2 wherein each column of the A 2,1 , the B 2,1 , the A 2,2 , and the B 2,2 is a DFT vector.

20. The method according to claim 15 , wherein the transmitter is further configured to:

send a first PMI (PMI 1 ) and a second PMI (PMI 2 ) to the base station, wherein the PMI 1 is used to indicate the matrix w 1 z, and the PMI 2 is used to indicate the matrix w 2 .

21. The method according to claim 15 , wherein:

the matrix W 2 is used for column selection from W 1 Z 1 to form the matrix W; or

the matrix W 2 is used for weighted combination of the columns of W 1 Z 1 to form the matrix W.

22. A base station, comprising:

a transmitter, configured to send a reference signal to user equipment (UE);

a receiver, configured to receive a precoding matrix indicator (PMI) sent by the UE; and

a processor, configured to determine a precoding matrix W in a codebook according to the PMI, wherein the precoding matrix W is a product of three matrices being w 1 , Z, and w 2 , w=w 1 zw 2 , both w 1 and Z are block diagonal matrices, W 1 =diag{X 1 ,X 2 }, Z=diag{Z 1 ,Z 2 }, and each column of each block matrix z, in the matrix Z has the following structure:

z i,k =(α i,k 2 +β i,k 2 ) 1/2 [α i,k e i,k T β i,k e jθ i,k e i,k T ] T

wherein i is an index variable of the block matrix Z i ; k is an index variable of the column z i,k ; [ ] T denotes matrix transposition; e i,k denotes an n i x1 selection vector, wherein in the vector, the k th element is 1 and all other elements are 0, and n i is a half of the number of columns of a matrix x i ; θ i,k is a phase shift, α i,k ≧0, and β i,k ≧0; w 2 is used to select one or more column vectors in the matrix W 1 Z and to perform weighting combination to form the matrix W.

23. The method according to claim 22 , wherein the matrix X 1 and the matrix X 2 are equivalent.

24. The method according to claim 22 , wherein the matrix Z 1 and the matrix Z 2 are equivalent.

25. The method according to claim 22 , wherein the matrix W 1 satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein each column of the matrix X 1,1 and each column of the matrix X 1,2 are orthogonal to each other;

X 2 =[X 2,1 ,X 2,2 ] wherein each column of the matrix X 2,1 and each column of the matrix X 2,2 are orthogonal to each other.

26. The method according to claim 22 , wherein the matrix W 1 satisfies at least one of the following:

X 1 =[X 1,1 ,X 1,2 ], wherein the matrix X 1,1 is a Kronecker product of matrices A 1,1 and B 1,1 , and X 1,2 is a Kronecker product of matrices A 1,2 and B 1,2 , wherein each column of the A 1,1 , the B 1,1 , the A 1,2 , and the B 1,2 is a DFT vector;

X 1 =[X 2,1 ,X 2,2 ], wherein the matrix X 2,1 is a Kronecker product of matrices A 2,1 and B 2,1 , and X 1,2 is a Kronecker product of matrices A 2,2 and B 2,2 , wherein each column of the A 2,1 , the B 2,1 , the A 2,2 , and the B 2,2 is a DFT vector.

27. The method according to claim 22 , wherein the receiver is further configured to:

receive a first PMI (PMI 1 ) and a second PMI (PMI 2 ) sent by the UE, wherein the PMI 1 is used to indicate the matrix w 1 z, and the PMI 2 is used to indicate the matrix w 2 .

28. The method according to claim 22 , wherein:

the matrix W 2 is used for column selection from W 1 Z 1 to form the matrix W; or

the matrix W 2 is used for weighted combination of the columns of W 1 Z 1 to form the matrix W.