Opportunistic relay selection for secure communication in AF multi-antenna relaying networks

In this paper, we investigate opportunistic relay (OR) selection in multi-antenna amplify-and-forward (AF) relay communication networks with secrecy constraints. To reveal the capability of the multiple-antenna relay in improving the secrecy performance, we proposed three selection criteria, namely, minimum selection (MS), conventional selection (CS) and optimal selection (OS). The first scheme tries to minimize the signal-to-noise ratio (SNR) received by the malicious eavesdropper, the second scheme seeks the relay which maximize SNR to the destination and the third one considers the ratio of received SNR between the destination and the eavesdropper. Then, we analyze the system performance in terms of the ergodic achievable secrecy capacity (EASC) in the view of physical-layer (PHY) security. Finally, the simulation results validate that the opportunistic relay selection schemes is effective to improve the EASC over the direct transmission in the multi-antenna amplify- and-forward relay networks.