Cooperative Delay-Constrained Cognitive Radio Networks: Throughput Maximization with Full-Duplex Capability Impact

Abstract

In this paper, we study the problem of maximizing the secondary user (SU) throughput under a quality of service (QoS) delay requirement of the primary user (PU). In addition, we investigate the impact of having a full-duplex capability at the SU on the network performance, compared to the case of a half-duplex SU. We consider a cooperative cognitive radio (CR) network with multipacket reception (MPR) capabilities at the receiving nodes. In our proposed system, the SU not only exploits the idle time slots (i.e. when PU is not transmitting) but also chooses between cooperating or sharing the channel with the PU probabilistically. We formulate our optimization problem maximizing the SU throughput under a PU delay constraint; we optimize over the SU transmission modes’ selection probabilities. The resultant optimization problem turns out to be a non-convex quadratic constrained quadratic programming (QCQP) optimization problem, which is, in general, an NP-hard problem. An efficient approach is devised to solve it and characterize the stability region of the network under a delay constraint on the PU. Numerical results, surprisingly, reveal that the network performance with a full-duplex SU is not always better than that of a half-duplex SU. In fact, we show that a full-duplex capability at the SU can adversely affect the stability performance of the network especially if the channel condition between the SU and the destinations is weaker than that between the PU and the destinations.