Method of transceiving feedback information in wireless communication system and apparatus therefor

1. A method of transmitting feedback information to a network entity by a base station supporting multi-user multi-input multi-output (MU-MIMO), the method comprising:

measuring channel information for multiple channels between antennas of the base station and each of user equipments;

obtaining a projection matrix based on the measured channel information;

projecting one of the channel information or uplink data received from the user equipments to a second space from a first space using the projection matrix; and

transmitting feedback information containing one of the projected channel information or the projected uplink data to the network entity;

receiving, from the network entity, downlink data for the user equipments on which a precoding is performed based on a predetermined transmit power, wherein the predetermined transmit power is determined based on the feedback information,

wherein the first space corresponds to a complex space, the second space corresponds to a real number space and a size of the channel information or a size of the uplink data projected to the second space is reduced after the channel information or the uplink data is projected.

2. The method of claim 1 , further comprising:

selecting at least one user equipment from the user equipments based on average reception power or a channel estimation error,

wherein the projecting the one of the channel information or the uplink data comprises projecting a channel estimation value corresponding to the selected at least one user equipment among the channel information to the second space from the first space.

3. The method of claim 2 ,

wherein the projecting the one of the channel information or uplink data comprises obtaining K 1 *K 1 channel estimation values of a real number from K 1 *M complex channel estimation values selected from K*M complex channel estimation values contained in the channel information, and

wherein the K corresponds to a number of user equipments transmitting signals, wherein the K 1 corresponds to a number of the at least one selected user equipment and wherein the M corresponds to a number of the antennas of the base station.

4. The method of claim 1 , wherein the projecting the one of the channel information or the uplink data comprises eliminating a fading component having smaller coherence time from among a first fading component and a second fading component for the multiple channels, the first fading component and the second fading component are contained in the channel information or the uplink data in the first space.

5. The method of claim 1 , wherein obtaining the projection matrix comprises obtaining the projection matrix using at least one of:

a first scheme based on a Hermitian matrix of the estimated channel information;

a second scheme based on a Hermitian matrix of a short-term fading component obtained from the estimated channel information; or

a third scheme based on a multiple of the Hermitian matrix of the short-term fading component obtained from the estimated channel information and a long-term fading component.

6. The method of claim 1 , further comprising:

clustering the user equipments to virtual user equipments based on the estimated channel information,

wherein first precoding is performed on downlink data for the user equipments by a first precoding matrix according to a result of the clustering and second precoding is performed on the downlink data on which the first precoding is performed by a second precoding matrix.

7. The method of claim 6 , wherein the first precoding is configured to eliminate interference from between user equipments clustered as an identical virtual user equipment and the second precoding is configured to eliminate interference from between the virtual user equipments.

8. The method of claim 6 , wherein the first precoding matrix is determined based on a short-term fading component contained in the channel information estimated by the base station and a short-term fading component contained in channel information estimated by other base station performing coordinated transmission with the base station and wherein the second precoding matrix is determined based on a long-term fading component contained in the channel information estimated by the base station.

9. The method of claim 6 , wherein the feedback information further comprises information on a long-term fading component among the estimated channel information and the result of the clustering, and

the method further comprises:

receiving, from the network entity, the downlink data for the user equipments on which the first precoding is performed using the information on the long-term fading component; and

performing the second precoding on the downlink data for the user equipments on which the first precoding is performed, using a short-term fading component among the estimated channel information.

10. A base station transmitting feedback information to a network entity, comprising:

multiple antennas configured to perform multi-user multi-input multi-output (MU-MIMO);

a processor configured to measure channel information for multiple channels between antennas of the base station and each of user equipments, to obtain a projection matrix based on the measured channel information, to project one of the channel information or uplink data received from the user equipments to a second space from a first space using the projection matrix; and

a backhaul interface configured to

transmit feedback information containing one of the projected channel information or the projected uplink data to the network entity, and

receive, from the network entity, downlink data for the user equipments on which a precoding is performed based on a predetermined transmit power, wherein the predetermined transmit power is determined based on the feedback information,

wherein the first space corresponds to a complex space, the second space corresponds to a real number space and a size of the channel information or a size of the uplink data projected to the second space is reduced after the channel information or the uplink data is projected.