A Dynamic Channel Access Strategy for Underlay CRNs: Markov Modeling and Performance Evaluation

Unlike in overlay cognitive radio networks, secondary users (SUs) in underlay cognitive radio networks can access licensed spectrum even at the presence of a primary user (PU), given that the interference caused by the secondary transmission is lower than a pre-specified threshold. Based on this underlay access principle, we propose in this paper a dynamic channel access strategy for multi-channel cognitive radio networks. Different from existing underlay access techniques, channel assembling, spectrum adaptation and restricted channel occupancy are also considered in the proposed strategy in order to achieve better performance in the secondary network. Accordingly, a partial channel occupancy (PCO) mode, which allows SUs to access a portion of a channel when co-existing with a PU, is introduced in this study. The size of this portion is adjusted by selecting an appropriate value of a configurable parameter α in the PCO mode. The system performance is evaluated for both primary and secondary networks and a comparison analysis is carried out to assess the cost against the gain. Numerical results demonstrate that the proposed underlay channel access strategy outperforms the corresponding overlay strategy in terms of secondary network capacity, blocking probability and dropping probability. The cost and gain analysis identifies appropriate traffic conditions under which the overall system performance could be improved by employing the proposed underlay strategy. Copyright © 0000 John Wiley & Sons, Ltd. ∗Correspondence I. A. M. Balapuwaduge, Department of Information and Communication Technology, University of Agder (UiA), N-4898 Grimstad, Norway. E-mail: [email protected]