Cognitive Access Protocol for Alleviating Sensing Errors in Cognitive Multiple-Access Systems

This letter studies a time-slotted multiple-access system with a primary user (PU) and a secondary user (SU) sharing the same channel resource. We propose a novel secondary access protocol which alleviates sensing errors and detects the availability of primary channels with the highest ability of detection. Under the proposed protocol, the SU may access the channel at one of a predefined instants within the time slot each of which associated with a certain access probability that changes based on the sensing outcome. There is also a possibility of accessing the channel at the beginning of the time slot without channel sensing. The optimization problem is stated such that the secondary throughput is maximized under stability of the primary queue and a constraint on the primary queueing delay. Numerical results demonstrate the beneficial gains of the proposed protocol in terms of secondary throughput.