Oblivious Rendezvous in Cognitive Radio Networks

Rendezvous is a fundamental process in the operation of a Cognitive Radio Network (CRN), through which a secondary user can establish a link to communicate with neighbors on the same frequency band (channel). The licensed spectrum is supposed to be divided into N non-overlapping channels and most previous works assume all users have the same label for the same channel. However, this might be impractical in distributed systems such as CRN where there is no central controller. Thus we propose Oblivious Rendezvous where the users may have different labels for the same frequency band. In this paper, we study the oblivious rendezvous problem forM users (ORP-M for short) in a multihop network with diameter D . In order to tackle ORP-M, we focus on the rendezvous process between two users (ORP-2) and extend the algorithms to ORP-M. First, we derive an Ω(N) lower bound for ORP-2 in a constructive way. Second, we propose two deterministic distributed algorithms solving ORP-2. The first one is ID Hopping (IDH) algorithm which generates a fixed length sequence and guarantees rendezvous in O(N max{N,M}) time slots, which meets the lower bound when M = O(N). The other one is Multi-Step Hopping (MSH) algorithm which guarantees rendezvous in O(N logN M) time slots by combing ID scaling and hopping with different steps. This result meets the lower bound if M can be bounded by a polynomial function of N , which suits better for large scale networks. The two algorithms are also applicable to non-oblivious rendezvous and is comparable to the state-of-the-art results. Third, we extend the algorithms to ORP-M with bounded rendezvous time by increasing a factor of the diameterD. Moreover, extensive simulation results compared with the state-of-the-art rendezvous algorithms corroborate our theoretical analyses.