Secure Communications with a Full-Duplex Relay Network under Residual Self-Interference

Abstract

This letter studies secure communications in a full-duplex relay (FDR) network when an eavesdropper overhears communications between legitimate parties. In a FDR network, both the amplify-and-forward relay and the destination operate in full-duplex for the purpose of achieving a higher secrecy rate and/or improving security. In particular, the destination is capable of receiving the relayed signal and simultaneously emitting a cooperative jamming signal. This work is motivated by an intriguing question: how much residual self-interference (SI) in a FDR network is allowed to achieve a superiority of secrecy performance over conventional half-duplex relay (HDR) networks? To answer the question, the secrecy outage probability (SOP) of the FDR network is derived as a function of residual SI. The analytic results enable us to compare the SOPs of existing HDR networks and the FDR network at various levels of residual SI. In addition, this work allows one to opportunistically select either FD or HD, which leads to a significant performance improvement.