Delay analysis and optimal access strategy in multichannel dynamic spectrum access system

In this paper, we consider a hierarchical cognitive radio scenario where the secondary users (SUs) may access the licensed spectrum opportunistically, whenever it is not occupied by the primary users (PUs). Our work focuses on the delay performance analysis of the SU system and the optimal access strategy for the case of sharing multiple licensed channels among SUs. By merging the PU traffic with SU traffic, we propose the model of priority virtual queue on licensed channels. Based on this model, we obtain the expected system delay expression of SU traffic through M/G/1 preemptive repeat priority queuing analysis. For the case of multiple licensed channel access, the access strategy is further investigated to minimize the expected transmission delay of SU traffic. The optimal access strategy is modeled as a nonlinear programming problem, which can be resolved by means of classic Genetic Algorithm (GA). Numerical results validate our analysis and optimal access strategy design.