Patent ID: 8542776

Claim:
A method for receiving/transmitting data in a closed-loop multi-antenna system that defines multiple antenna groups by antenna grouping on multiple antennas, and performs data transmission individually via each of the multiple antenna groups, the method comprising: receiving, by a transmitter, feedback information from a receiver; calculating, by the transmitter, each of a sum rate (R_MU) in a multi-user mode and a sum rate (R_SU) in a single-user mode using the feedback information; selecting, by the transmitter, the single-user mode or the multi-user mode as a transmission mode using a comparison result between the sum rate (R_MU) in the multi-user mode and the sum rate (R_SU) in the single-user mode; and transmitting, by the transmitter, a data stream according to the selected transmission mode; acquiring, by the receiver, channel quality information (CQI) for each data stream transmitted individually via each antenna group corresponding to the selected transmission mode; determining, by the receiver, the CQI associated information from the CQI acquired individually for each antenna group; and transmitting, by the receiver, the determined CQI associated information to the transmitter as the feedback information, wherein the CQI associated information includes maximum CQI, an antenna group index associated with the maximum CQI, rank information, and remaining CQI associated the rank information.