Method for transmitting and receiving channel state information in multi-antenna wireless communication system, and apparatus therefor

1. A method for reporting, by a user equipment (UE), channel state information (CSI) in a multi-antenna wireless communication system, the method comprising:

receiving a channel state information reference signal (CSI-RS) on x multiple antenna ports from a base station, where x is a natural number;

selecting y multi-antenna ports among the x multi-antenna ports, where y is a natural number; and

reporting to the base station a precoding matrix indicator (PMI) indicating a precoding matrix selected from a codebook for the y multi-antenna ports,

wherein the x multi-antenna ports are grouped into a first antenna port group and a second antenna port group in units of the y multi-antenna ports,

wherein the precoding matrix is selected based on a weighted summation of a first channel measured based on the CSI-RS transmitted on the antenna port in the first antenna port group and a second channel measured based on the CSI-RS transmitted on the antenna port in the second antenna port group, and

wherein the precoding matrix is similarly applied to the first antenna port group and the second antenna port group.

2. The method of claim 1 , wherein the precoding matrix is selected to maximize a channel quality indicator (CQI) derived based on the CSI-RS transmitted on the y multi-antenna ports.

3. The method of claim 1 , wherein the y multi-antenna ports are selected with the same antenna port as the antenna port layout applicable to the codebook for the y multi-antenna ports among the x multi-antenna ports.

4. The method of claim 1 , wherein the first channel and the second channel are summed by a first weight and a second weight, respectively, and

wherein the first weight and the second weight are predetermined or provided from the base station to the UE through radio resource (RRC) signaling.

5. The method of claim 1 , wherein the first channel and the second channel are summed by the first weight and the second weight, respectively, and

wherein the first weight and the second weight are determined by the UE and reported to the base station.

6. The method of claim 5 , wherein the first weight and the second weight are determined from a predetermined weight vector codebook.

7. The method of claim 6 , wherein the entirety or a subset of the weight vector codebook is used according to the number of feedback bits for reporting the first weight and the second weight.

8. The method of claim 1 , further comprising:

receiving a codebook configuration from the base station,

wherein the y multi-antenna ports are selected according to the codebook configurations.

9. The method of claim 1 , wherein the CSI for the y multi-antenna ports is calculated by multiplying by a power compensation coefficient at the time of the CSI calculation, and

wherein the power compensation coefficient is predetermined or provided from the base station to the UE by radio resource control (RRC) signaling.

10. The method of claim 9 , wherein whether the CSI for the y multi-antenna ports is calculated by multiplying by the power compensation coefficient is provided from the base station through the radio resource control (RRC) signaling.

11. The method of claim 1 , wherein only in the case of a specific rank, the y multi-antenna ports are selected among the x multi-antenna ports, and

wherein the specific rank is predetermined or provided from the base station to the UE by the radio resource control (RRC) signaling.

12. A user equipment (UE) for reporting channel state information (CSI) in a multi-antenna wireless communication system, the UE comprising:

a transceiver configured to transmit and receive a radio signal; and

a processor configured to control the transceiver,

wherein the processor;

receives a channel state information reference signal (CSI-RS) on x multiple antenna ports from a base station, where x is a natural number,

selects y multi-antenna ports among the x multi-antenna ports, where y is a natural number, and

reports to the base station a precoding matrix indicator (PMI) indicating a precoding matrix selected from a codebook for the y multi-antenna ports,

wherein the x multi-antenna ports are grouped into a first antenna port group and a second antenna port group in units of the y multi-antenna ports,

wherein the precoding matrix is selected based on a weighted summation of a first channel measured based on the CSI-RS transmitted on the antenna port in the first antenna port group and a second channel measured based on the CSI-RS transmitted on the antenna port in the second antenna port group, and

wherein the precoding matrix is similarly applied to the first antenna port group and the second antenna port group.