Waveform and Beamforming Design for Intelligent Reflecting Surface Aided Wireless Power Transfer: Single-User and Multi-User Solutions

TL;DR

This paper proposes joint waveform and passive beamforming strategies for IRS-assisted wireless power transfer, demonstrating significant power gains by leveraging IRS deployment schemes, energy harvester nonlinearity, and multi-user optimization.

Contribution

It introduces novel joint waveform and beamforming algorithms for IRS-aided WPT, considering energy harvester nonlinearity and two IRS deployment schemes, enhancing power transfer efficiency.

Findings

IRS provides extra passive beamforming gain over conventional WPT.

Joint design significantly boosts output DC power in single-user and multi-user systems.

Frequency selective IRS outperforms frequency flat IRS in power transfer efficiency.

Abstract

In this paper, we study the waveform and passive beamforming design for intelligent reflecting surface (IRS)-aided wireless power transfer (WPT). Generalized multi-user and low complexity single-user algorithms are derived based on alternating optimization (AO) framework to maximize the weighted sum output DC current, subject to transmit power constraints and passive beamforming phases unit modulus constraints. The input signal waveform and IRS passive beamforming phase shifts are jointly designed as a function of users' individual frequency-selective channel state information (CSI). The energy harvester nonlinearity is explored and two IRS deployment schemes, namely frequency selective IRS (FS-IRS) and frequency flat IRS (FF-IRS), are modeled and analyzed. This paper highlights the fact that IRS can provide an extra passive beamforming gain on output DC power over conventional WPT designs and significantly influence the waveform design by leveraging the benefit of passive beamforming, frequency diversity and energy harvester nonlinearity. Even though FF-IRS exhibits lower output DC current than FS-IRS, it still achieves substantially increased DC power over conventional WPT designs. Performance evaluations confirm the significant benefits of a joint waveform and passive beamforming design accounting for the energy harvester nonlinearity to boost the performance of single-user and multi-user WPT system.