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.