Optimal time sharing in underlay cognitive radio systems with RF energy harvesting

TL;DR

This paper introduces an online method to optimize time sharing between energy harvesting and information transmission in underlay cognitive radio systems, enhancing spectrum and energy efficiency by leveraging RF energy harvesting from primary systems.

Contribution

It presents a novel online solution for optimal time allocation in RF energy harvesting cognitive radios, maximizing average achievable rate while protecting primary system performance.

Findings

Optimal time sharing significantly improves achievable rate.

The proposed method outperforms equal time allocation.

Protection criteria for primary systems are maintained.

Abstract

Due to the fundamental tradeoffs, achieving spectrum efficiency and energy efficiency are two contending design challenges for the future wireless networks. However, applying radio-frequency (RF) energy harvesting (EH) in a cognitive radio system could potentially circumvent this tradeoff, resulting in a secondary system with limitless power supply and meaningful achievable information rates. This paper proposes an online solution for the optimal time allocation (time sharing) between the EH phase and the information transmission (IT) phase in an underlay cognitive radio system, which harvests the RF energy originating from the primary system. The proposed online solution maximizes the average achievable rate of the cognitive radio system, subject to the $\varepsilon$-percentile protection criteria for the primary system. The optimal time sharing achieves significant gains compared to equal time allocation between the EH and IT phases.