On the Queue Dynamics of Multiuser Multichannel Cognitive Radio Networks

For protocol and system design in cognitive radio networks (CRNs), it is essential to identify which system settings or environmental conditions have great impacts on the quality-of-service (QoS) performance for secondary users (SUs) and how they influence it, which are still open issues. In this paper, an analytical framework to quantify the queue dynamics of a multi-SU multichannel CRN is developed. In the analytical framework, we consider the important lower-layer mechanisms and settings, including spectrum sensing errors, medium-access control (MAC) protocols, link adaptation technologies such as adaptive modulation and coding (AMC) and automatic repeat request (ARQ), and limited buffer size. By modeling the queue dynamics as a discrete-time finite-state Markov chain (FSMC), we derive the analytical expressions of the average queue length, packet-dropping rate, and packet-collision rate. Based on these expressions, the QoS metrics including average queueing delay, packet-loss rate, and effective throughput are obtained. Simulation and numerical results are presented to verify the accuracy of the proposed analytical framework and investigate the QoS performance of SUs.