Average Capacity and Power Optimization for Full-Duplex DF Relaying with Large-Scale Antenna Array at the Destination

Full-duplex relaying system, which allows the relay node to transmit and receive at the same time and over the same frequency, can realize a significant enhancement of spectral efficiency. Besides residual self-interference, there exists another challenge for the full-duplex relaying system, i.e., the destination always treats the source-to-destination link as interference. To overcome this challenge, the large-scale antenna array is employed at the destination. By using the characteristic that the channel vectors of source-to-destination and relay-to-destination become asymptotically orthogonal, the system average capacity is derived and the optimal transmit power of the relay is obtained by maximizing the average capacity. Numerical results show that the system average capacity can be enhanced significantly compared to direct transmission and the optimal transmit power of the relay is determined by the residual self-interference.