Soft-Sensing CQI Feedback-Based Access Scheme in Cognitive Radio Networks

In this paper, an access scheme for cognitive radio networks is proposed in which secondary users (SUs) make use of the primary user(s) (PUs) channel quality feedback information. SUs decide their transmission strategy based on the PUs' channel quality indicator (CQI) feedback available in the PU network and the SUs' sensing of PUs' activity. We consider two energy sensing approaches, namely, hard-sensing, and soft-sensing. An SU accesses the primary channel with access probabilities which are selected to maximize the SU service rate while ensuring PUs' quality of service requirements defined as primary queues' stability. The proposed system is modeled using a multi-dimensional Markov chain. Closed-form expressions for secondary users' throughput and the average primary users' packet delays are derived. Moreover, SUs' access probabilities selection is formulated as a constrained optimization problem. Performance of the proposed scheme, in terms of the secondary user service rate and the primary user delay, is shown to be superior to other systems in which secondary users do not leverage PUs' CQI feedback information.