Exploring Relay Cooperation Scheme for Load-Balance Control in Two-hop Secure Communication System

This work considers load-balance control among the relays under the secure transmission protocol via relay cooperation in two-hop wireless networks without the information of both eavesdropper channels and locations. The available two-hop secure transmission protocols in physical layer secrecy framework cannot provide a flexible load-balance control, which may significantly limit their application scopes. This paper proposes a secure transmission protocol in case that the path-loss is identical between all pairs of nodes, in which the relay is randomly selected from the first $k$ preferable assistant relays. This protocol enables load-balance among relays to be flexibly controlled by a proper setting of the parameter $k$, and covers the available works as special cases, like ones with the optimal relay selection ($k=1$) and ones with the random relay selection ($k = n$, i.e. the number of system nodes). The theoretic analysis is further provided to determine the maximum number of eavesdroppers one network can tolerate by applying the proposed protocol to ensure a desired performance in terms of the secrecy outage probability and transmission outage probability.