Cluster-Based Distributed MAC Protocol for Multichannel Cognitive Radio Ad Hoc Networks

This paper proposes a cluster-based distributed medium access control (CDMAC) protocol for multichannel and multihop mobile cognitive radio ad hoc networks (CRAHNs). Secondary users (SUs) of the CRAHNs sense the spectrum to obtain licensed channels opportunistically from primary users (PUs) according to the channel-sensing model. The CRAHN is divided into clusters, with cluster heads determined according to the degree of importance of the nodes. The control and data channels are dynamically selected based on the success probability and stability of the idle PU channels. The traffic adaptively determines the contention window size, and a dynamic contention window mechanism is proposed to reduce the MAC contention delay. Furthermore, this mechanism achieves high throughput for a given contention window size. We also develop a Markov chain model to characterize the performance of our proposed CDMAC protocol for a saturated network. The Markov chain is also characterized by initial-state probabilities and a state-transition probability matrix. We perform extensive simulations to verify that the proposed CDMAC protocol can achieve higher performance in the mobile CRAHNs than other approaches.