Frequency-Gateway Based Differential Rendezvous Algorithm for Cognitive Radio Networks

Cognitive radio (CR) is considered a promising technology to alleviate the spectrum shortage problem. In cognitive radio networks (CRNs), rendezvous is a fundamental function for users to exchange control information before communication. Since the dynamic and distributed characteristics of CRNs, the blind channel rendezvous algorithm based on channel-hopping (CH) is considered to be the most effective and practicable scheme. In this paper, we model the time to rendezvous (TTR) by considering the rendezvous diversity and successful probability. Based on the analysis of this model, we propose a novel blind rendezvous algorithm called frequency-gateway based differential (FGBD) algorithm. Different from the most existing works pursuing full rendezvous diversity, a portion of available channels is used to dynamically generate CH sequence in our proposed algorithm according to the channels occupancy ratio (COR). We denote this channel set as frequency-gateway. In this way, we can get an efficient rendezvous and enough rendezvous diversity to guarantee a bounded maximum TTR (MTTR) under any CORs. Moreover, FGBD has two modes with different channel hopping rates, which can get fast rendezvous after determining the frequency-gateway. The simulation results show that our proposed algorithm outperforms the other rendezvous schemes in different conditions.