Contention Window-Based Deadlock-Free MAC for Blind Rendezvous in Cognitive Radio Ad Hoc Networks

Cognitive radio (CR) technology is a promising solution to the spectrum scarcity problem. Due to the spectrum varying nature of CR networks, unlicensed users are required to perform channel hopping to realize blind rendezvous. However, blind rendezvous can easily cause deadlock in the network. Moreover, due to the nature of blind rendezvous, a deadlock cannot be detected by either the suffering users or other users. Consequently, a deadlock will eventually cause the whole network stuck and prohibit the network throughput. In this paper, the challenge of deadlock-free blind rendezvous in CR networks is addressed for the first time. By analyzing the deadlock issues in both two-user and multi-user scenarios, we propose a novel MAC protocol with an optimal contention window size which can avoid deadlock and provide high network throughput. In addition, we also propose a probabilistic model for analyzing the network performance with our MAC. Simulation results validate our analytical model and demonstrate that our proposed protocol outperforms other possible attempts.