Joint user-antenna selection scheme in multiuser two-way relaying system with TDBC protocol

This paper considers a multiuser two-way relaying system with time division broadcast (TDBC) protocol, where one multiantenna base station (BS) and one out of N single-antenna mobile stations (MSs) exchange information with the aid of one single-antenna amplify-and-forward (AF) relay. We first propose an optimal joint user-antenna selection scheme, which minimizes the system outage probability. Then by fixing the power allocation factor at the relay, a low-complexity suboptimal scheme is proposed and compared with the optimal scheme. Simulation results show that the proposed schemes can achieve full diversity order and there is a small performance gap between them. Furthermore, the suboptimal scheme is more robust to the channel estimation errors than the optimal counterpart.