High-performance beamforming and spatial channel pairing schemes at relay station for AF-based multi-pair two-way relay networks

This paper proposes a high-sum-rate maximum signal-to-interference and noise ratio (Max-SINR) plus maximum signal-to-leakage and noise ratio (Max-SLNR) beamforming per user (Max-SINR plus Max-SLNR per user) at the relay station (RS) for multi-pair two-way relay system with multi-antenna users. The proposed beamformer applies Max-SINR and Max-SLNR to uplink and downlink channels, respectively. It beam-forms all antennas per user together not individually (called Max-SINR plus Max-SLNR per antenna). Following this, three spatial channel pairing (SCP) schemes including maximum sum-rate (Max-SR), random and minimum sum-rate (Min-SR) at RS are developed. Simulation results show the proposed Max-SINR plus Max-SLNR per user achieves appreciable sum-rate gains over existing Max-SINR plus Max-SLNR per antenna, zero-forcing and block diagonalization beamformers while the proposed Max-SR-SCP achieves substantial sum-rate gains over Min-SR-SCP and random SCP.