Method for reporting channel state information in wireless communication system, and device for same

1. A method for transmitting channel state information (CSI) by a user equipment (UE) in a wireless communication system, comprising:

receiving configuration information for CSI reporting from a base station,

wherein the configuration information includes a plurality of codebook parameters related to a configuration of linear combination codebook for the CSI reporting;

receiving, from the base station, a reference signal for the CSI reporting;

calculating, based on a compression method in a frequency domain, CSI including a precoding matrix indicator (PMI) for beams linearly combined based on (i) the plurality of codebook parameters and (ii) the reference signal,

wherein the CSI consists of a first part and a second part; and

reporting the calculated CSI to the base station,

wherein a size of a payload of the second part is determined based on at least one parameter among the plurality of codebook parameters,

wherein based on a capacity of a resource allocated to report the CSI being smaller than a size of a payload of the CSI calculated based on the plurality of codebook parameters, the size of the payload of the second part is reduced until the size of the payload of the CSI becomes less than or equal to the capacity of the resource, and

wherein the size of the payload of the second part is reduced by reducing a number of co-efficients generated based on the at least one parameter.

2. The method of claim 1 ,

wherein the PMI is included in the second part.

3. The method of claim 2 ,

wherein the PMI includes (i) information related to a beam group including the beams linearly combined and (ii) information related to the co-efficients.

4. The method of claim 3 ,

wherein a size of the PMI is reduced by reducing the number of co-efficients, and

wherein the size of the payload of the second part is reduced as the size of the PMI is reduced.

5. The method of claim 3 ,

wherein the beams included in the beam group determined based on the information related to the beam group are linearly combined by applying the co-efficients determined based on the information related to the the co-efficients.

6. The method of claim 5 ,

wherein the co-efficients include (i) a phase co-efficient for a phase combination on the beams included in the beam group and (ii) an amplitude co-efficient for an amplitude combination on the beams included in the beam group.

7. The method of claim 1 ,

wherein the number of the co-efficients is reduced based on a priority order among the co-efficients.

8. The method of claim 3 ,

wherein the plurality of codebook parameters consist of (i) a first parameter for determining a number of the beams included in the beam group, (ii) a second parameter for determining a number of subbands in which the CSI is reported, and (iii) a third parameter for determining a maximum value of the number of the co-efficients.

9. The method of claim 8 , further comprising:

determining a value of the at least one parameter that causes the size of the payload of the CSI to be less than or equal to the capacity of the resource,

wherein the value of the at least one parameter is reduced based on the determination, and

wherein the number of the co-efficients is reduced based on a reduction of the value of the at least one parameter.

10. The method of claim 9 , further comprising:

recalculating the CSI based on the reduced number of the co-efficients; and

reporting the recalculated CSI to the base station,

wherein the recalculated CSI includes information on the at least one parameter whose value is reduced.

11. The method of claim 10 ,

wherein the at least one parameter whose value is reduced is the third parameter.

12. The method of claim 6 ,

wherein the amplitude co-efficient includes an amplitude co-efficient for a subband,

wherein values of the amplitude co-efficient for the subband are quantized into 8 values, and

wherein the quantized values of the amplitude co-efficient for the subband are configured based on (i) a maximum value ‘1’ and (ii) values obtained by multiplying the maximum value ‘1’ by √{square root over (½)}.

13. The method of claim 1 ,

wherein the compression method in the frequency domain is a method in which the CSI is reported through only some subbands among all subbands configured for reporting the CSI report of the UE.

14. The method of claim 13 , further comprising:

determining a number of subbands that cause the size of the payload of the CSI to be less than or equal to the capacity of the resource,

wherein the determined number of the subbands is less than a number of the some subbands, and

wherein the number of co-efficients is reduced based on the CSI being reported through only subbands as many as the determined number of the subbands.

15. A user equipment (UE) for transmitting channel state information (CSI) in a wireless communication system, the UE comprising:

a radio frequency (RF) module for transmitting and receiving radio signals; and

a processor for controlling the RF module, wherein the processor configured to:

receive configuration information for CSI reporting from the base station,

wherein the configuration information includes a plurality of codebook parameters related to a configuration of linear combination codebook for the CSI reporting;

receive, from the base station, a reference signal for the CSI reporting;

calculate, based on a compression method in a frequency domain, CSI including a precoding matrix indicator (PMI) for beams linearly combined based on (i) the plurality of codebook parameters and (ii) the reference signal,

wherein the CSI consists of a first part and a second part; and

report the calculated CSI to the base station,

wherein a size of a payload of the second part is determined based on at least one parameter among the plurality of codebook parameters,

wherein based on a capacity of a resource allocated to report the CSI being smaller than a size of a payload of the CSI calculated based on the plurality of codebook parameters, the size of the payload of the second part is reduced until the size of the payload of the CSI becomes less than or equal to the capacity of the resource, and

wherein the size of the payload of the second part is reduced by reducing a number of co-efficients generated based on the at least one parameter.

16. A method for receiving channel state information (CSI) by a base station in a wireless communication system, comprising:

transmitting configuration information for CSI reporting to a user equipment (UE),

wherein the configuration information includes a plurality of codebook parameters related to a configuration of linear combination codebook for the CSI reporting;

transmitting, to the UE, a reference signal for the CSI reporting; and

receiving, from the UE, the CSI including a precoding matrix indicator (PMI) for beams linearly combined,

wherein the CSI consists of a first part and a second part,

wherein a size of a payload of the second part is determined based on at least one parameter among the plurality of codebook parameters,

wherein based on a capacity of a resource allocated to report the CSI being smaller than a size of a payload of the CSI calculated based on the plurality of codebook parameters, the size of the payload of the second part is reduced until the size of the payload of the CSI becomes less than or equal to the capacity of the resource, and

wherein the size of the payload of the second part is reduced by reducing a number of co-efficients generated based on the at least one parameter.

17. A base station for receiving channel state information (CSI) in a wireless communication system, the base station comprising:

a radio frequency (RF) module for transmitting and receiving radio signals; and

a processor for controlling the RF module, wherein the processor configured to:

transmit configuration information for CSI reporting to a user equipment (UE),

wherein the configuration information includes a plurality of codebook parameters related to a configuration of linear combination codebook for the CSI reporting;

transmit, to the UE, a reference signal for the CSI reporting; and

receive, from the UE, the CSI including a precoding matrix indicator (PMI) for beams linearly combined,

wherein the CSI consists of a first part and a second part,

wherein a size of a payload of the second part is determined based on at least one parameter among the plurality of codebook parameters,

wherein based on a capacity of a resource allocated to report the CSI being smaller than a size of a payload of the CSI calculated based on the plurality of codebook parameters, the size of the payload of the second part is reduced until the size of the payload of the CSI becomes less than or equal to the capacity of the resource, and

wherein the size of the payload of the second part is reduced by reducing a number of co-efficients generated based on the at least one parameter.