Outage-driven link selection for secure buffer-aided networks

In this paper, we investigate secure communication in a two-hop wireless network, where multiple buffer-aided relays assist to securely forward data from the sender to the destination threatened by a passive eavesdropper. To satisfy the security and delay requirements, we propose a novel link selection policy without the instantaneous wiretap channel state information. Different from the most current link selection policies, the proposed link selection policy is designed by joint considering the link secrecy outage probability and the buffer states. To evaluate the secrecy performance, we first characterize the system state transition matrix and the stationary state probability, and then derive the closed-form expressions for the secrecy outage probability and the secrecy rate. Moreover, we formulate a framework based on the queuing theory to analyze the end-to-end information delay at the source, the relays, and the queues, and derive the closed-form expression for the information delay. Finally, we conduct simulations to validate our theoretical performance analysis, and verify the performance improvement of the proposed outage-driven secure transmission scheme in terms of secrecy outage probability and information delay.