Queueing analysis for preemptive transmission in underlay CRNs

In many cognitive radio applications, there are multiple types of message queues. Existing queueing analysis works in underlay CR networks failed to discuss packets heterogeneity. Therefore high priority packets with impatient waiting time that have preemptive transmission opportunities over low class are investigated. We model the system behavior as a M/M/1+GI queue which is represented by a two dimensional state transition graph. The reneging probability of high priority packets and the average waiting time in two-class priority queues is analyzed. Simulation results demonstrate that the average waiting time of high priority packets decreases with the growing interference power threshold and the average waiting time of the low priority packet is proportional to the arrival rate of the high priority packet. This work may lay the foundation to design efficient MAC protocols and optimize long term system performance by carefully choosing system parameters.