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

1. A method for reporting channel state information (CSI), comprising:

receiving a first reference signal set from a base station, wherein the first reference signal set comprises at least two reference signals;

sending first CSI to the base station, wherein the first CSI is determined according to the first reference signal set, and the first CSI comprises at least one of a first rank indicator (RI) and a first precoding matrix indicator (PMI);

receiving a second reference signal set from the base station, wherein antenna port information of the second reference signal set is determined based on the first CSI, and the second reference signal set comprises at least one reference signal, wherein the antenna port information of the second reference signal set comprises at least one of following information: quantity of antenna ports corresponding to the second reference signal set, antenna port number of each of the antenna ports, or reference signal sequence initialization ID corresponding to each of the antenna ports; and

sending second CSI to the base station, wherein the second CSI is determined according to the second reference signal set,

wherein each reference signal comprised in the first reference signal set corresponds to an antenna in an antenna subarray of the base station, and each reference signal comprised in the second reference signal set corresponds to an antenna subarray of multiple antenna subarrays comprised in the base station.

2. The method according to claim 1 , wherein the receiving a second reference signal, comprises:

receiving the second reference signal set from the base station, wherein the second reference signal set is determined based on the first PMI comprised in the first CSI and a preset quantity of layers of a precoding matrix.

3. The method according to claim 1 , wherein the first RI is 2 raised to the power of an integer.

4. The method according to claim 1 , wherein a sending period of the first reference signal set is longer than a sending period of the second reference signal set.

5. The method according to claim 1 , wherein the sending first CSI, comprises:

determining a first precoding matrix from a first codebook according to the first reference signal set; and

sending the first CSI to the base station, wherein the first CSI comprises at least one of the first RI and the first PMI, and the first PMI is used to indicate the first precoding matrix, wherein

a precoding matrix comprised in the first codebook is a discrete Fourier transform (DFT) matrix, a Hadamard matrix, a Householder matrix, a Kronecker product of two DFT matrixes, a Kronecker product of a DFT matrix and a Hadamard matrix, or a Kronecker product of a DFT matrix and a Householder matrix.

6. The method according to claim 1 , wherein the sending second CSI, comprises:

determining a second precoding matrix from a second codebook according to the second reference signal set; and

sending the second CSI to the base station, wherein the second CSI comprises at least one of a second RI and a second PMI, and the second PMI is used to indicate the second precoding matrix, wherein

the second codebook comprises at least one precoding matrix W, and the precoding matrix W has a structure determined according to the following equation:

W

=

(

2

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NM

)

-

1

2

⁡

[

w

⊗

v

e

j

⁢

⁢

φ

⁢

w

⊗

v

]

⁢

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or

W

=

(

4

⁢

NM

)

-

1

2

⁡

[

w

⊗

v

w

⊗

v

e

j

⁢

⁢

φ

⁢

w

⊗

v

-

e

j

⁢

⁢

φ

⁢

w

⊗

v

]

,

wherein

w=[1 e jϕ . . . e j(N-1)ϕ ] T , v=[1 e jθ . . . e j(M-1)θ ] T , [ ] T denotes a matrix transpose, ⊗ denotes a Kronecker product, M and N are positive integers, and θ, ϕ, and φ are phases.

7. The method according to claim 6 , wherein the phase θ=mπ/16, and m=0, . . . , 15; or the phase ϕ=nπ/32 and n=0, . . . , 31; or the phase φ=lπ/2, and l=0, . . . , 3 or l==0, 1.

8. User equipment, comprising:

a receiver, configured to receive a first reference signal set from a base station, wherein the first reference signal set comprises at least two reference signals;

a transmitter, configured to send first channel state information (CSI) to the base station, wherein the first CSI is determined according to the first reference signal set, and the first CSI comprises at least one of a first rank indicator (RI) and a first precoding matrix indicator (PMI);

the receiver is further configured to receive a second reference signal set from the base station, wherein antenna port information of the second reference signal set is determined based on the first CSI, and the second reference signal set comprises at least one reference signal, wherein the antenna port information of the second reference signal set comprises at least one of following information: quantity of antenna ports corresponding to the second reference signal set, antenna port number of each of the antenna ports, or reference signal sequence initialization ID corresponding to each of the antenna ports; and

the transmitter is further configured to send second CSI to the base station, wherein the second CSI is determined according to the second reference signal set,

wherein each reference signal comprised in the first reference signal set corresponds to an antenna in an antenna subarray of the base station, and each reference signal comprised in the second reference signal set corresponds to an antenna subarray of multiple antenna subarrays comprised in the base station.

9. The user equipment according to claim 8 , wherein the receiver is configured to:

receive the second reference signal set from the base station, wherein the second reference signal set is determined based on the first PMI comprised in the first CSI and a preset quantity of layers of a precoding matrix.

10. The user equipment according to claim 9 , wherein the first RI is 2 raised to the power of an integer.

11. The user equipment according to claim 9 , wherein a sending period of the first reference signal set is longer than a sending period of the second reference signal set.

12. The user equipment according to claim 9 , wherein the transmitter is configured to:

determine a first precoding matrix from a first codebook according to the first reference signal set; and send the first CSI to the base station, wherein the first CSI comprises at least one of the first RI and the first PMI, and the first PMI is used to indicate the first precoding matrix, wherein

a precoding matrix comprised in the first codebook is a discrete Fourier transform (DFT) matrix, a Hadamard matrix, a Householder matrix, a Kronecker product of two DFT matrixes, a Kronecker product of a DFT matrix and a Hadamard matrix, or a Kronecker product of a DFT matrix and a Householder matrix.

13. The user equipment according to claim 9 , wherein the transmitter is configured to:

determine a second precoding matrix from a second codebook according to the second reference signal set; and send the second CSI to the base station, wherein the second CSI comprises at least one of the second RI and the second PMI, and the second PMI is used to indicate the second precoding matrix, wherein

the second codebook comprises at least one precoding matrix W, and the precoding matrix W has a structure determined according to the following equation:

W

=

(

2

⁢

NM

)

-

1

2

⁡

[

w

⊗

v

e

j

⁢

⁢

φ

⁢

w

⊗

v

]

⁢

⁢

or

W

=

(

4

⁢

NM

)

-

1

2

⁡

[

w

⊗

v

w

⊗

v

e

j

⁢

⁢

φ

⁢

w

⊗

v

-

e

j

⁢

⁢

φ

⁢

w

⊗

v

]

,

wherein

w=[1 e jϕ . . . e j(N-1)ϕ ] T , v=[1 e jθ . . . e j(M-1)θ ] T , [ ] T denotes a matrix transpose, ⊗ denotes a Kronecker product, M and N are positive integers, and θ, ϕ, and φ are phases.

14. The user equipment according to claim 13 , wherein the phase θ=mπ/16 and m=0, . . . , 15; or the phase ϕ=nπ/32, and n=0, . . . , 31; or the phase ϕ=lπ/2, and l=0, . . . , 3 or l=0, 1.

15. A base station, comprising:

a transmitter, configured to send a first reference signal set to user equipment, wherein the first reference signal set comprises at least two reference signals;

a receiver, configured to receive first channel state information (CSI) from the user equipment, wherein the first CSI is determined based on the first reference signal set, and the first CSI comprises at least one of a first rank indicator (RI) and a first precoding matrix indicator (PMI);

a processor, configured to determine antenna port information of a second reference signal set according to the first CSI, wherein the second reference signal set comprises at least one reference signal, and the antenna port information of the second reference signal set comprises at least one of following information: quantity of antenna ports corresponding to the second reference signal set, antenna port number of each of the antenna ports, or reference signal sequence initialization ID corresponding to each of the antenna ports;

the transmitter is further configured to send the second reference signal set to the user equipment according to the antenna port information of the second reference signal; and

the receiver is further configured to receive second CSI from the user equipment, wherein the second CSI is determined based on the second reference signal set,

wherein each reference signal comprised in the first reference signal set corresponds to an antenna in an antenna subarray of the base station, and each reference signal comprised in the second reference signal set corresponds to an antenna subarray of multiple antenna subarrays comprised in the base station.

16. The base station according to claim 15 , wherein the processor is configured to:

determine the second reference signal set according to the first PMI and a preset quantity of layers of a precoding matrix when the first CSI comprises the first PMI.

17. The base station according to claim 15 , wherein a sending period of the first reference signal set is longer than a sending period of the second reference signal set.