Study of relay selection for dual-hop networks under secrecy constraints with multiple eavesdroppers

This study deals with opportunistic relay selection in cooperative networks with secrecy constraints, where a number of eavesdropper nodes try to overhear the source message. To avoid this problem, we consider three opportunistic relay selection strategies to maximize the capacity to the destination and also minimize that to the eavesdroppers. The first scheme tries to reduce the overheard information at the eavesdroppers by choosing the relay having the lowest instantaneous SNR to them. The second is a conventional selection relaying one which seeks the relay having the highest SNR to the destination. In the third scheme, we consider about the approximate secrecy channel gain at each relay, and then choose the best one to forward the signal to the destination. The secrecy capacities of three schemes which are analyzed and confirmed by the Monte Carlo simulation method, show that the third scheme is the best one to maximize secrecy capacity of the network.