Modeling and Analysis of Spectrum Handoffs for Real-Time Traffic in Cognitive Radio Networks

In this paper, we present an analytical framework to evaluate the effects of spectrum handoffs on the performance of the real-time traffic in cognitive radio (CR) networks. In CR networks, CR users (CUs) are secondary users to the licensed spectrum and they are required to vacate the spectrum when a primary user (PU) reclaims it. We consider a general setting in which multiple PU interruptions may occur during the transmission period of CU traffic. Therefore, spectrum handoffs are provided to protect both the PU´s and CU´s transmission. In order to characterize the channel usage behaviors of primary traffic and CR real-time traffic with spectrum handoffs, we develop a queuing model which consists of preemptive resume priority M/G/1 and M/G/1/1 queues. Based on this queuing model, channel utilization factor can be derived. Besides, the blocking and forced termination probabilities for real-time traffic are also derived. Simulation results are given to validate the proposed analytical model.