PERFORMANCE GAINS FOR SPECTRUM UTILIZATION IN COGNITIVE RADIO NETWORKS WITH SPECTRUM HANDOFF

Cognitive radio (CR) can improve spectrum utilization by allowing the secondary users to temporarily access the primary users’ unutilized licensed spectrum. In order to guarantee quality of service (QoS) of the secondary users, spectrum handoff mechanism must be implemented in CR networks. Spectrum handoff procedures aim to help the secondary users vacate the spectrum and search the target channels to resume the unfinished transmission when the primary user appears at the occupied licensed band. In such a system, the most basic issue is how much CR technique can improve spectrum utilization. In order to quantify this gain, we propose a preemptive resume priority (PRP) M/G/1 queueing network model to characterize the spectrum usage behavior with multiple spectrum handoffs between the primary and the secondary users. Based on this model, we show how to evaluate spectrum utilization factor under different traffic loads. From the numerical results, we find that the utilization improvement on the channel with lower arrival rate of the primary connections is larger than the channel with higher arrival rate of the primary connections.1