대규모 다중 입력 다중 출력 시스템의 훈련 오버헤드 감소를 위한 중계 기술

초록

In large-scale multiple-input multiple-output (MIMO) systems, the performance can be limited by the training overhead required to obtain extensive channel state information (CSI). To overcome this issue, in this study, a relaying strategy is proposed to reduce the high training overhead in massive MIMO systems by deploying a relay node (RN) with two antennas between the source node (SN) and the destination node (DN). During the training subphase, a two-antenna RN transmits two orthogonal pilot signals, enabling both SN and DN to acquire CSI. In the first-hop data transmission subphase, either space-time line coding or maximum ratio transmission is applied using the CSI at the transmitter (i.e., SN). For the second-hop data transmission (relaying) subphase, either space-time block coding or maximum ratio combining is employed based on the CSI at the receiver (i.e., DN). Combining two first- and two second-hop techniques yields four cooperative communication strategies. Because the training subphase consistently requires only two pilot transmissions regardless of the antenna numbers at the SN and DN, the proposed relaying techniques can substantially reduce the training overhead in large-scale MIMO systems that possibly have an enormous number of antennas. Simulation results verify the superior performance of the proposed relaying techniques owing to the effective reduction in training overhead.

키워드