CCH: a clique based asymmetric rendezvous scheme for cognitive radio ad-hoc networks

Rendezvous (RDV) in cognitive radio ad-hoc networks (CRAHNs) is one of the key ways for a pair of unknown cognitive radio users to initiate communications. CRAHN is a multi-channel environment where channel status changes over time depending on primary users’ (PUs) activities. Thus, achieving RDV in CRAHNs cannot be guaranteed on a predetermined common control channel (CCC). However, CCC results channel saturation, extreme transmission overhead of control information, and a point of vulnerability. To address this problem, channel hopping (CH) protocols have proposed for enabling RDV. This research presents a CH protocol based on clique system, called clique based channel hopping (CCH) for the purpose of RDV establishment. The proposed CCH is a role based blind RDV CH system where sender and receiver generates CH sequence based on h-clique and v-clique respectively. The CCH employs channel-ranking information for allocating more slots to high-rank channels than low-rank ones. The system dynamically updates the CH sequence by replacing channels from both the licensed and unlicensed bands to protect intermittent PUs. The CCH protocol satisfies the following requirements: (1) guaranteed RDV; (2) no synchronisation; and (3) symmetric and asymmetric channel model. Simulation results show that the proposed CCH scheme outperforms similar CH schemes in terms of average time-to-rendezvous and the degree of overlap in both symmetric and asymmetric channel scenario.