A feedback-based access scheme for cognitive radio networks over interference channels with primary queue guarantees

In this paper, we consider a cognitive relaying network in which the secondary user exploits the primary user feedback. Depending on the primary user feedback information and sensing the secondary user accesses the channel with random access probabilities. These access probabilities are smaller when the primary user is sensed to be active or if a negative acknowledgement is overheard over the feedback link. The access probabilities are determined so that the secondary user throughput is maximized without violating certain primary user quality of service (QoS) constraint(s). We consider two QoS constraints, namely, requiring the primary user queue stability and a limit on the average primary user packet delay. We thus consider an interference-based communication model which allows simultaneous transmissions from the primary user and the secondary user. Our scheme provides improvements in the secondary user throughput while maintaining the primary user QoS constraint when compared to a collision-based scheme in which the secondary user backs off when the primary user is either sensed to be active or indicated to be active based on the overheard primary feedback.