Multi-User Scheduling of the Full-Duplex Enabled Two-Way Relay Systems

In this paper, we address the multi-user scheduling problem of the multi-user two-way full-duplex (FD) decode-and-forward relay system. According to the availability of the channel state information (CSI) and system state information (SSI), three scheduling schemes are investigated in terms of the system outage performance. Specifically, for the non-CSI case, we analyze the random scheduling scheme, which serves as a baseline for comparison. For the full CSI case, we propose the Max-Min scheduling scheme, which is theoretically proved to be suboptimal in the low signal-to-interference-plus-noise ratio (SINR) regime but optimal in the high SINR regime. To minimize the outage probability, we propose the optimal scheduling scheme, which involves the full SSI. In addition, the exact closed-form outage probability expressions corresponding to different schemes are derived under the general independent but not identically distributed channels. The residual self-interference incurred by the FD mode is taken into account. Moreover, independent and identically distributed channels are also considered as special cases. Finally, numerical simulations are performed to corroborate the theoretical results. The results reveal that the Max-Min scheduling and optimal scheduling schemes significantly improve the outage performance compared with the random scheduling scheme.