Flexible relay selection for secure communication in two-hop wireless networks

This work considers two-hop wireless networks in the presence of eavesdroppers with unknown channels and locations, and proposes a new transmission protocol with flexible relay selection to achieve secure and reliable communication in such networks. For a two-hop network with n system nodes, the new protocol first identifies the k (1 ≤ k ≤ n) relay candidate nodes with the best links to both source and destination and then randomly selects one among them for message relay, such that a flexible tradeoff between eavesdropper tolerance capability and load-balance capability can be controlled by a proper setting of parameter k. Theoretical analysis is further provided to help us understand the eavesdropper tolerance capability of the new protocol. While previous works mainly focus on exploring the asymptotic behavior and scaling law results for infinitely large networks, this paper considers a more practical network with finite number of system nodes, and provides a theoretical analysis to determine the exact results on the number of eavesdroppers one network can tolerate when the new protocol is adopted to ensure a desired performance in terms of the maximum allowed secrecy outage probability and transmission outage probability.