A distributed multichannel MAC protocol for rendezvous establishment in cognitive radio ad hoc networks

Rendezvous in cognitive radio ad-hoc networks is an essential step for a pair of unknown cognitive radio (CR) users to initiate a communication. Most of the existing studies address rendezvous problems as a design of a search strategy to meet on the same channel at the same time. However, in a multi-user environment, a rendezvous cannot guarantee even if two users are on the same channel at the same time due to channel contention and the multi-channel hidden node problem. To overcome problems, we propose a novel cognitive radio rendezvous (CR-RDV) protocol by integrating the rendezvous and medium access control (MAC) issues. We modify the traditional backoff strategy based on remaining transmission time and packet length to avoid the concurrent transmission with the primary users (PUs). Moreover, an additional sensing period is introduced immediately after the RTS packet to solve the blocking problem in the multi-user environment. The proposed CR-RDV protocol is analysed based on the modified Bianchi model and an absorbing Markov chain model to capture the multi-user and rendezvous channel contention. Through extensive simulations, we show that the proposed CR-RDV protocol outperforms the existing methods with respect to throughput, delay, and packet dropping.