Rendezvous Scheme without a Predetermined Sender or Receiver in Cognitive Radio Ad-Hoc Networks

Cognitive radio emerges as a promising technology to improve the utilization of the allocated spectrum. In a cognitive radio network, secondary users (SUs) need to sense the spectrum to obtain currently available channels and have to vacate the occupied channels when primary users (PUs) return. In cognitive radio networks, establishing a link through a common available channel is defined as the rendezvous process between two SUs. Channel hopping is a widely used method to solve the rendezvous problem that two SUs hop according to a designed channel hopping sequence until they meet on a common available channel. Past works on rendezvous focus on designing the channel hopping sequence while ignoring the necessary RTS-and-CTS exchange process to build a link when two SUs hop to a common available channel. However, during the initialization phase of a cognitive radio network (CRN), each SU may try to rendezvous with other SUs to exchange control information. There is no explicit role for an SU, since it cannot determine if other SUs are senders or receivers currently. Therefore, in this paper, we define a send-or-receive problem in a rendezvous process of SUs during the initialization phase of a CRN and propose a new rendezvous problem as the link rendezvous problem. We also propose a blind rendezvous scheme to solve the link rendezvous problem considering practical scenarios in a CRN. Simulation results show that our proposed schemes can achieve a fast successful link rendezvous considering the send-or-receive problem. To the best of our knowledge, this is the first paper that addresses the link rendezvous problem in a cognitive radio ad-hoc network.