Performance Analysis of Cognitive Radio Networks with a Two-part Queue

In a cognitive radio network (CRN), a preempted secondary user (SU) is placed in a call level queue to wait for accessing another free channel. If the availability of channels is transparent to SUs, packets will be generated during their waiting time and the performance of the CRN will be influenced by which way to handle these packets. In this paper, the call level queue is departed into two parts, delay queue and discard queue. Here, an analytical model is developed to derive the formulas for both call level performance measures (i.e., call blocking probability) and packet level performance measures (i.e., packet delay, packet loss ratio and throughput). Numerical results show that theoretical models are consistent with simulation results. The major observations include (i) The performances of an SU degrade as the call arrival rate increases. (ii) With the increase of the delay queue length, the SU call blocking probability and packet delay increase, while the packet loss ratio and throughput decrease. (iii) Adopting different delay queue length causes a smaller effect on call blocking probability and throughput than on packet loss ratio and packet delay.