Optimal relay assignment for secrecy capacity maximization in cooperative ad-hoc networks

Physical layer security has emerged as a key technique for providing trustworthy and reliable future wireless networks and has witnessed a significant growth in the past few years. In this paper, we aim to improve the physical layer security and provide secure cooperative communication through cooperative relay assignment. By characterizing the security performance of the system by secrecy capacity, we study the secrecy capacity maximization problem in cooperative ad hoc networks with the involvement of multiple malicious eavesdroppers. Specifically, we propose a system model where a set of relay nodes can be exploited by multiple source-destination pairs to achieve physical layer security. We theoretically present a corresponding formulation for the secrecy capacity maximization problem. Then we develop an optimal relay assignment algorithm to solve the problem in polynomial time. The basic idea behind our proposed algorithm is to boost the capacity of the primary channel by simultaneously decreasing the capacity of the eavesdropping channel. Through extensive experiments, we validate that our proposed relay assignment algorithm significantly increase the system secrecy capacity under various network settings.