Stable Throughput of Cooperative Cognitive Networks With Energy Harvesting: Finite Relay Buffer and Finite Battery Capacity

Abstract

This paper studies a generic model for cooperative cognitive radio networks where the secondary user is equipped with a finite relay queue as well as a finite battery queue. Our prime objective is to characterize the stable throughput region. Nevertheless, the complete characterization of the stable throughput region for such system is notoriously difficult, since the computation of the steady state distribution of the twodimensional Markov Chain (MC) model for both finite queues is prohibitively complex. We first propose an algorithm to characterize the stable throughput region numerically, and show its sheer computational complexity for large queue lengths. To lend tractability and explore the nature of design parameters optimization at the cognitive node, we next focus on two simpler systems, namely, finite battery queue with infinite relay queue and finite relay queue with infinite battery queue (referred henceforth as dominant system 1 and 2, respectively). For each proposed dominant system, we investigate the maximum service rate of the cognitive node subject to stability conditions. Despite the complexity of the formulated optimization problems, due to their non-convexity, we exploit the problems' structure to transform them into linear programs. Thus, we are able to solve them efficiently using standard linear programming solvers. Our numerical results demonstrate that, in practical systems, finite battery and relay queues achieve the same level of benefits of a system with infinite queue sizes, when their sizes are sufficiently large. They also reveal that the achievable stable throughput region significantly expands when the arrival rate of the energy harvesting process increases.

Cooperative Delay-Constrained Cognitive Radio Networks: Delay-Throughput Trade-Off With Relaying Full-Duplex Capability

“…This completes our stability region characterization; any pair (λ p , λ s ) that satisfies (9) and (12) belongs to the stability region of our proposed scheme. It is worth mentioning that a PU packet might experience two queuing delays; the delay in Q p and the delay in Q sp if it is relayed via the SU.…”

“…The cooperation policy in [18] was also simpler than ours since it restricted the SU to access the channel only when the PU is idle. Another work that has considered the case of finite queues is the work in [9]; it was shown in this work that the assumption of having infinite queues is good in many cases to analyze systems with finite queues. The reason was in most cases the queue lengths do not grow to infinity and even for short queues the assumption of having infinite queues can provide good approximations for the system performance measures in the case of finite queues.…”

“…They showed that cooperation is advantageous only when the channel condition between the PU and the common destination is worse than that between the SU and the destination (same restriction as in [6]). Recently, the scheme presented in [8] was modified by the authors in [9]. The SU is assumed to have a third battery queue to store harvested energy; the stability rate region of the network was derived subject to some SU energy harvesting constraints.…”

“…In [12], the model introduced in [11] was extended to the case of a full-duplex SU that has its own packets' queue in addition to the PU relaying queue; this is unlike [11] where the relay node is assumed not to have packets of its own; the SU throughput was maximized subject to some network stability constraints. It is worth mentioning that recent works presented in the context of cooperative cognitive radio, e.g., [9] and [13] have also considered only the case of half-duplex SUs.…”

Simultaneous Wireless Information and Power Transfer for Dynamic Cooperative Spectrum Sharing Networks

“…In [18], the outage probability of single-relay cooperation and multi-relay cooperation strategies in a CCRN with energy harvesting was investigated over Nakagami-m fading channels. Abd-Elmagid et al [19] introduced a generic model for CCRNs, where the relaying SUs is equipped with a finite capacity battery and a finite relay queue. Mukherjee et al [20] studied a SWIPT-enabled CCRN, where the secondary user transmitter assists bi-directional communication between a pair of PUs following the principle of two-way relaying.…”