Transmit beamforming aided amplify-and-forward MIMO full-duplex relaying with limited dynamic range

• A joint analog and digital self-interference cancellation model is considered.
• Joint source and relay precoding is proposed for different setups.
• Optimal rank-one precoding is derived using convex optimization.
• Alternating optimization is proposed to achieve a multiple-stream transmission.
• Proposed precoding methods provide significant gain as the dynamic range decreases.

In this paper we address the design of a relay-assisted communication system where two half-duplex (HD) users communicate with each other via the help of an amplify-and-forward (AF) and full-duplex (FD) relay node. We design joint user beamforming and relay transmit strategies to deal with the self-interference signal at the FD relay node. Our approach is to maximize the system sum rate via linear transmit strategies by exploiting multiple antennas at all the involved nodes. Convex optimization based sub-optimal and optimal solutions are developed. More specifically, an alternating optimization for self-interference aware FD relaying (AO) is devised when the transmission of multiple streams is considered. Moreover, a unified approach via gradient projections is proposed as a benchmark. It can be applied regardless of the number of antennas at each node but has a significantly higher computational complexity than the AO algorithm. Simulation results show that the proposed algorithms can achieve a good performance compared to the benchmark algorithm. Moreover, a significant FD gain is achieved in terms of the sum rate when the residual self-interference power is smaller than the noise.

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