Virtual MIMO Based Self-Interference Utilization for a Full-Duplex AF Relay OFDM System

Time-dispersive loopback self-interference (SI) is a challenging issue for a full-duplex (FD) amplify-and-forward (AF) relay assisted orthogonal frequency division multiplexing (OFDM) system. In this paper, a utilization scheme is proposed for the uplink. A virtual multiple-input multiple-output (MIMO) system is modeled to enhance the receive diversity, by regarding the residual loopback SI after partial cancellation at relay as additional sources rather than noise. A gain control algorithm is proposed for the FD relay to enable the virtual MIMO modeling, and the optimal target transmission power at relay is derived to maximize the receive signal-to-interference-and-noise ratio (SINR) at base station. The proposed system is more practical as the main computational load is shifted from relay to BS to help the AF relay maintain a low running cost, compared to the previous relay-centric systems with complex SI cancellation at relay. The proposed system significantly outperforms the relay-centric system.