Wireless Energy Harvesting in a Cognitive Relay Network (1601.02223v1)

Abstract: Wireless energy harvesting is regarded as a promising energy supply alternative for energy-constrained wireless networks. In this paper, a new wireless energy harvesting protocol is proposed for an underlay cognitive relay network with multiple primary user (PU) transceivers. In this protocol, the secondary nodes can harvest energy from the primary network (PN) while sharing the licensed spectrum of the PN. In order to assess the impact of different system parameters on the proposed network, we first derive an exact expression for the outage probability for the secondary network (SN) subject to three important power constraints: 1) the maximum transmit power at the secondary source (SS) and at the secondary relay (SR), 2) the peak interference power permitted at each PU receiver, and 3) the interference power from each PU transmitter to the SR and to the secondary destination (SD). To obtain practical design insights into the impact of different parameters on successful data transmission of the SN, we derive throughput expressions for both the delay-sensitive and the delay-tolerant transmission modes. We also derive asymptotic closed-form expressions for the outage probability and the delay-sensitive throughput and an asymptotic analytical expression for the delay-tolerant throughput as the number of PU transceivers goes to infinity. The results show that the outage probability improves when PU transmitters are located near SS and sufficiently far from SR and SD. Our results also show that when the number of PU transmitters is large, the detrimental effect of interference from PU transmitters outweighs the benefits of energy harvested from the PU transmitters.

• The paper analyzes a wireless energy harvesting protocol for cognitive relay networks, providing analytical expressions for secondary network outage probability and throughput.
• Numerical results show that primary user placement impacts secondary network outage probability and identify an optimal number of primary users for best performance.
• The findings offer practical insights for designing cognitive relay networks by balancing energy harvesting benefits and primary user interference to optimize performance.

Wireless Energy Harvesting in a Cognitive Relay Network: A Study

This paper presents a detailed analysis of a wireless energy harvesting protocol within an underlay cognitive relay network, which includes multiple primary user (PU) transceivers. The authors propose a novel protocol that allows secondary nodes to harvest energy from the primary network while collaboratively utilizing the licensed spectrum of the latter. The research focuses on understanding the impact of varying system parameters on network performance, with a primary aim of deriving conditions for minimizing outage probability and optimizing throughput in the secondary network.

Analytical Developments

The paper introduces an exact analytical expression for the outage probability of the secondary network, which is affected by three key power constraints: the maximum transmit power at both the secondary source and the secondary relay, the peak permissible interference power at each PU receiver, and the interference power from each PU transmitter to the secondary relay and destination. By dissecting the complex interaction of these constraints, the authors derive throughput expressions for both delay-sensitive and delay-tolerant transmission modes, crucially providing asymptotic behavior analysis as the number of PU transceivers approaches infinity. The analytical development encompasses the utilization of Rayleigh fading channel models and the investigation of power splitting (PS) and time switching (TS) receiver architectures, enabling secondary nodes to efficiently harvest energy from RF signals while maintaining effective information transmission.

Numerical Results

Numerical simulations reveal that the outage probability decreases when PU transmitters are positioned close to the secondary source and adequately distant from the secondary relay and destination. Furthermore, the detrimental interference effects from PU transmitters can outweigh the benefits of energy harvesting when their number grows significantly. The results underscore an optimal trade-off between energy harvesting benefits and interference drawbacks, highlighting an optimal number of PU transceivers that minimizes outage probability and maximizes throughput.

Implications and Future Work

The findings of this paper have substantial implications for the integration of energy harvesting technologies in cognitive radio networks. The dual benefits of energy harvesting—enhanced energy efficiency and prolonged network lifetime—are evident, alongside the adaptive management of interference constraints which broadens spectrum utilization strategies. Practically, these insights encourage the deployment of cognitive relay networks with strategic energy harvesting protocols that optimize wireless communication performance.

The paper suggests future research directions including the application of stochastic geometry to model PU distributions and the exploration of spatial parameters impacting energy harvesting efficiencies. Advanced analytical methods could further refine the optimal configurations for cognitive relay network deployments.

In conclusion, the paper makes a significant contribution to the evolving field of energy harvesting within cognitive radio networks by delivering deep analytical perspectives and robust numerical validations that inform both theoretical insights and practical implementations.