Joint transceiver and relay beamforming design for multi-pair two-way relay systems

In this work, we propose a simple yet effective beam-forming technique for multiple-input multiple-output (MIMO) multi-pair two-way relay channels. Two key ingredients in our technique are adoption of signal space alignment (SSA) for transmit and receive beamforming and amplify-and-forward (AF) relay beamforming based on advanced zero-forcing (ZF) criterion. From the sum-rate analysis on MIMO multi-pair two-way relay channels, we show that the proposed method achieves full multiplexing gain and substantial beamforming gain in realistic multi-pair two-way relay scenario.