Modeling the Behavior of Contending Opportunistic Cognitive Radios

In this paper, we propose a new model to evaluate the behavior of cognitive radios (CRs). In this model, we consider a specific number of primary users having independent probabilistic on-off behavior. In addition, a specific number of opportunistic cognitive radios in saturation mode is assumed. We consider contention for CRs in order to occupy an inactive primary channel independently according to a simple MAC scheme. Our model is based on a closed BCMP state-dependent queueing network. We map contention of the CRs and the behavior of primary users on suitable parameters of the queueing network. By solving the network, we obtain the steady state behavior of CRs, then we find the efficient number of CRs. Moreover, the utilization increase for a typical primary channel has been computed. In the last part of the paper, we obtain the behavior of CRs for two cases and confirm our results by simulation.