Opportunistic Transmission Scheduling for Secure Wireless Links: An Optimal Stopping Approach

Secure communications constitute a major concern in wireless networks' design. Toward this direction, physical layer security can achieve confidential data transmission from an information-theoretic viewpoint. This paper focuses on investigating the secure transmission of information over Nakagami-m fading channels in the presence of an eavesdropper. Specifically, we propose a distributed scheduler that opportunistically exploits the time-varying fading channel characteristics with a view to maximizing the expected secrecy throughput of a wireless link. The proposed multi-threshold scheduling policy postpones the communication up to an acceptable deadline until the secure-optimal time instant is found, based on the optimal stopping theory. The performance of the proposed scheduler is evaluated through simulations for various link parameters, while its achieved secrecy gain is examined and compared with other heuristic schemes.