Energy-Efficient Cooperative Cognitive Relaying Protocols for Full-Duplex Cognitive Radio Users and Delay-Aware Primary Users

This paper considers a network in which a primary user (PU) may cooperate with a cognitive radio (CR) user for transmission of its data packets. The PU is assumed to be a buffered terminal operating in a time-slotted fashion. We develop two protocols which involve cooperation between primary and secondary users. To satisfy certain quality of service requirements, users share time slot duration and frequency bandwidth. Moreover, the secondary user (SU) may leverage the primary feedback signal. The proposed protocols are designed such that the secondary rate is maximized and the primary queueing delay is maintained less than the queueing delay in case of non-cooperative PU. In addition, the proposed protocols guarantee the stability of the primary queue and maintain the average energy emitted by the CR user below a certain value. The proposed protocols also provide more robust and potentially continuous service for SUs compared to the conventional practice in cognitive networks where SUs transmit in the spectrum holes and silence sessions of the PUs. We include primary source burstiness, sensing errors, and feedback reception errors to the analysis of the proposed cooperative cognitive protocols. Numerical results show the beneficial gains of the cooperative protocols in terms of secondary rate and primary throughput, queueing delay, and average energy savings.