Secrecy outage analysis of buffer-aided multi-antenna relay systems without eavesdropper's CSI

This work studies the secrecy outage performance of buffer-aided dual-hop multi-antenna relay systems without eavesdropper's channel state information (CSI). By modeling the dynamic buffer state transitions with the Markov chain, the secrecy outage probability at each state is investigated and the stationary distribution probabilities of all states are subsequently derived. Using the total probability theorem, the closed-form expression of the secrecy outage probability of the system is finally obtained. It demonstrates that due to the fully exploitation of the available channels, the buffer-aided relay selection yields to better performance than Best Relay Selection (BRS), even when less relays and antennas are utilized. It is also shown that the buffer-aided relaying only results in a small performance degradation when the buffers are constrained to finite size, thus can be well applied to practical relaying cooperative networks. Simulation results are given to verify the theoretical analysis.