Cognitive radio (CR) technology is regarded as a backbone for the future generation wireless systems. Using CR technology, secondary users (SUs), a.k.a. CR users, are allowed to access RF spectrum opportunistically provided that they are not causing harmful interference to primary users (PUs) and vacate the bands upon the arrival of licensed PUs. In this paper, we investigate waiting probability of SUs to get channel access based on PUs' ON–OFF activities. Multi–user cognitive radio system is considered where SUs contend for spectrum access using time division multiple access over idle PU channels. Using queue dynamics as Poisson driven stochastic process, we characterise the waiting probability of secondary users. Generally speaking, in practical systems, secondary users of cognitive radio network would have no knowledge of activities of other users, thus the probability of being idle or contention probabilities of SUs' in cognitive radio network have to be assigned according to the available local information. Our focus is on SUs' waiting probability analysis, for which a systematic understanding is lacking. Simulation results show that the use of multiple channels and/or multiple slots leads to significant delay reduction and transmission fairness.
Keywords: cognitive radio networks, CRN, opportunistic spectrum access, waiting probability analysis, secondary users, simulation