A Dual - One Dimensional Queuing Model for Cognitive Radio Network Transmission

Abstract

This paper formulates the semi-passive backscatter transmission combined mode as a preemptive priority queueing system in two modes of hybrid transmission. In this mode, it is assumed that when there is no active primary user (PU) signal on the licensed channel, the secondary user (SU) signal can access this free channel in interweave mode. The PU has preemptive priority, i.e. when servicing the SU, the low-priority user is given low priority. If a primary user joins the system, the low-priority user's service is stopped and will resume when there are no high-priority users in the system. Conversely, when the licensed channel is busy with the PU's signal, the SU can access the channel in underlay mode at a lower transmission rate. Consequently, the performance of the SU, as well as the utilization of the spectrum, can be enhanced. Transmission between primary and secondary users is formulated as a dual one-dimensional queuing system. The system is governed by transient state equations and, using the generating function technique, the steady state probabilities, expected queue length and variance of both the primary and secondary users are obtained. Finally, some numerical calculations are carried out to investigate the relationship between the expected queue size and variance for various parameters.