A Discrete Time-Switching Protocol for Wireless-Powered Communications with Energy Accumulation

TL;DR

This paper proposes a discrete time-switching protocol for wireless-powered communication networks with energy harvesting, optimizing energy use and transmission based on channel conditions, and demonstrates improved throughput over existing protocols.

Contribution

The paper introduces a novel discrete time-switching protocol that adaptively switches between energy harvesting and information transmission based on channel state information.

Findings

The proposed protocol outperforms existing harvest-then-transmit protocols with large battery capacity.

A closed-form expression for average throughput is derived.

Numerical results validate the theoretical analysis.

Abstract

This paper investigates a wireless-powered communication network (WPCN) setup with one multi-antenna access point (AP) and one single-antenna source. It is assumed that the AP is connected to an external power supply, while the source does not have an embedded energy supply. But the source could harvest energy from radio frequency (RF) signals sent by the AP and store it for future information transmission. We develop a discrete time-switching (DTS) protocol for the considered WPCN. In the proposed protocol, either energy harvesting (EH) or information transmission (IT) operation is performed during each transmission block. Specifically, based on the channel state information (CSI) between source and AP, the source can determine the minimum energy required for an outage-free IT operation. If the residual energy of the source is sufficient, the source will start the IT phase. Otherwise, EH phase is invoked and the source accumulates the harvested energy. To characterize the performance of the proposed protocol, we adopt a discrete Markov chain (MC) to model the energy accumulation process at the source battery. A closed-form expression for the average throughput of the DTS protocol is derived. Numerical results validate our theoretical analysis and show that the proposed DTS protocol considerably outperforms the existing harvest-then-transmit protocol when the battery capacity at the source is large.