Local sequence based rendezvous algorithms for Cognitive Radio Networks

Rendezvous process plays an important role in constructing Cognitive Radio Networks (CRNs), through which a user establishes a link on a common licensed channel for communication with its neighbors. Generally, the licensed spectrum is divided into N channels and most blind rendezvous algorithms are realized by the 'channel hopping' method where each user repeats a Global Sequence constructed on top of all the N channels. This global sequence based method may contain lots of redundant channels resulting in large rendezvous time especially when the number of available channels each user has only accounts for a small fraction of all the N channels. In this paper, we introduce the Local Sequence based rendezvous algorithms where the local sequence is only constructed on top of each user's available channels and different user's local sequence could be different. Our first local sequence based algorithm called LS can guarantee rendezvous in O(N) time slots for symmetric users (both users have the same set of available channels) and in O(N²) time slots for asymmetric users, which matches the best known results [11]. Our major contribution is the Modified Local Sequence (MLS) based algorithm which can guarantee an exponentially shorter rendezvous time than the best known results when the number of available channels each user has is relatively small. Extensive simulation results comparing with the state-of-the-art rendezvous algorithms corroborate our theoretical analyses.