Wireless physical layer security enhancement with buffer-aided relaying

We consider utilizing a buffer-aided relay to enhance security for two-hop half-duplex relay networks with an external eavesdropper. We propose a link selection scheme that adapts reception and transmission time slots based on the channel quality, while considering both the two-hop transmission efficiency and the security. Closed-form expressions for the secrecy throughput and the secrecy outage probability (SOP) are derived, and the selection parameters are optimized to maximize the secrecy throughput or minimize the SOP. We also study two sub-optimal link selection schemes that only require a line search to solve the optimization problem. Numerical results show that buffer-aided relaying provides a significant improvement in security compared to conventional unbuffered relaying.