Self-Interference Cancellation with Optimal Feedback Path Selection on Full-Duplex Relay Systems

Full-duplex relay systems in wireless communication utilize the same time and frequency resources for transmission and reception at the relay node to improve spectral efficiency. This paper proposes a scheme that reduces residual self-interference significantly in the analog-circuit domain on full-duplex relay systems. The proposed scheme measures multiple responses of the feedback path by changing the direction of the main beam of the transmitter at the relay, and then selects the optimal direction that minimizes the residual self-interference. Analytical residual self-interference is derived as the criterion to select the optimal direction. In addition, analytical probability that the residual interference exceeds the target is derived, that helps determine the number of measured responses of the feedback path. Computer simulations show the superiority of the proposed scheme, and validate the analytical results.