Abstract
In this paper, the problem of maximizing the secondary user (SU) throughput under a primary user (PU) quality of service (QoS) delay requirement is studied. Moreover, the impact of having a full-duplex capability at the SU on the network performance is investigated compared to the case of a SU with half-duplex capability. We consider a cooperative cognitive radio (CR) network in which the receiving nodes have multi-packet reception (MPR) capabilities. In our proposed model, the SU not only benefits from the idle time slots (i.e. when PU is idle), but also chooses between sharing the channel or cooperating with the PU in a probabilistic manner. We formulate our optimization problem to maximize the SU throughput under a PU QoS, defined by a delay constraint; the optimization is performed over the transmission modes selection probabilities of the SU. The resultant optimization problem is found to be a non-convex quadratic constrained quadratic programming (QCQP) optimization problem, which is, generally, an NP-hard problem. We devise an efficient approach to solve it and to characterize the network stability region under a delay constraint set on the PU. Numerical results, surprisingly, reveal that the network performance when full-duplex capability exists at the SU is not always better compared to that of a half-duplex SU. In fact, we demonstrate that a full-duplex capability at the SU can, in some cases, adversely influence the network stability performance, especially if the direct channel conditions between the SU and the destinations are worse than that between the PU and the destinations. In addition, we formulate a multi-objective programming (MOP) optimization problem to investigate the trade-off between the PU delay and the SU throughput. Our MOP approach allows for assigning relative weights for our two conflicting performance metrics, i.e., PU delay and SU throughput. Numerical results also demonstrate that our cooperation policy outperforms conventional cooperative and non-cooperative policies presented in previous works.
Highlights
Cooperative communications have gained a growing interest over the years due to the important key role they can play in enabling efficient exploitation of wireless resources [2]
We investigate the trade-off between the primary user (PU) delay and the secondary user (SU) throughput using our multi-objective programming (MOP) formulation approach
In this paper, a cooperative cognitive radio (CR) network has been studied with the objective of maximizing the SU throughput subject to a PU delay constraint
Summary
Cooperative communications have gained a growing interest over the years due to the important key role they can play in enabling efficient exploitation of wireless resources [2]. It is worth mentioning that recent works presented in the context of cooperative cognitive radio, e.g., [9] and [13] have considered only the case of half-duplex SUs. The significance of our presented framework stems from the emergence of various real-time applications that should be supported by cooperative CR networks e.g., gaming, video streaming, and other multimedia applications; these applications require high throughput with firm delay constraints. The significance of our presented framework stems from the emergence of various real-time applications that should be supported by cooperative CR networks e.g., gaming, video streaming, and other multimedia applications; these applications require high throughput with firm delay constraints This aspect is mostly ignored or not investigated in all of the above-cited works [7], [8], [11], [12], [14], which mainly concentrated on improving certain performance measures subject to some network stability and/or energy harvesting constraints, with no explicit delay provisioning.
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