Performance analysis of secure buffer-aided cognitive radio network

The paper investigates a buffer-aided relay selection scheme for an underlay cognitive radio network in the presence of an eavesdropper. Eavesdropper can intercept the information transmission from the secondary source or the relay to the corresponding receiver. Relay is equipped with a buffer of finite buffer size so that it can store packets. We propose a max-ratio secure link selection scheme which can optimize the secrecy transmission performance by selecting the link which maximizes the secrecy capacity. It incorporates the instantaneous strength of the wireless links as well as the status of the finite relay buffers, and adapts the relay selection decision on the strongest available link by dynamically switching between relay reception and transmission. A closed-form expression for the secrecy outage probability is obtained based on the Markov chain to validate the proposed scheme. Simulation and theoretical results demonstrate that the proposed scheme can significantly enhance the secure performance compared to the conventional max-min-ratio secure relay selection schemes.