QoS Performance Analysis for the Second User in the Overlay Cognitive Radio Networks

In the cognitive radio networks (CRNs), the reliability, the efficiency and the fairness of the spectrum allocation is highly related to the quality of service (QoS) performance for the users. But in the overlay CRNs the QoS performance for the SUs is difficult to obtain due to the inherent opportunistic property of the spectrum resources for the SU´s data transmission. Since the spectrum occupancy states by the PUs are often characterized by Markov models, Markov-chain based analysis is commonly performed to analyze the QoS performance for the SUs. In this paper we consider an overlay CRN with multi-PUs where each PU´s data transmission follows M/M/c model and the SU has little limitation on the choice of the channels. An approximate estimation method of the average queue length for the SU is proposed here. Numerical simulations show that this method can achieve pretty accurate estimation in some scenarios.