Directional Antenna Based Distributed Blind Rendezvous in Cognitive Radio Ad-Hoc Networks

Abstract

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 communication link between two SUs through a common available channel is defined as the channel rendezvous problem. Channel hopping is a widely used method to solve the channel rendezvous problem under which two SUs hop according to a designed channel hopping sequence until they meet on a common available channel. Existing works on the rendezvous problem focus on designing the channel hopping schemes based on omni-directional antennas. However, omni-directional antennas can cause interference to the PUs within the entire transmission range of a SU. In this paper, we consider the rendezvous problem if SUs are equipped with directional antennas which can generate interference to less PUs. We address the sector rendezvous problem for the first time and analyze the indexing problem and the different sector number problem which make the sector rendezvous problem different from the channel rendezvous problem. We propose fully distributed sector rendezvous schemes for each SU that can guarantee a successful sector rendezvous and channel rendezvous simultaneously within a bounded time. Our proposed schemes can execute in a distributed way without information exchange between SUs, which is very practical. To the best of our knowledge, this is the first paper on designing fully distributed rendezvous schemes for SUs equipped with directional antennas.