On Two-Way Communications for Cooperative Multiple Source Pairs Through a Multi-Antenna Relay

The authors study Amplified-and-Forward (AF)-based Two-Way Relaying (TWR) with multiple source pairs, which are exchanging information through the relay. Each source has single antenna and the relay has multi-antenna. The optimal beamforming matrix structure that achieves maximum Signal-to-Interference-plus-Noise Ratio (SINR) for TWR with multiple source pairs is derived. They then present two new non-zero-forcing based beamforming schemes for TWR, which take into consideration the tradeoff between preserving the desired signals and suppressing inter-pair interference between different source pairs. Joint grouping and beamforming scheme is proposed to achieve a better Signal-to-Interference-plus-Noise Ratio (SINR) when the total number of source pairs is large and the Signal-to-Noise Ratio (SNR) at the relay is low.