Performance Analysis of Millimeter Wave Wireless Power Transfer With Imperfect Beam Alignment

TL;DR

This paper analyzes how imperfect beam alignment affects millimeter wave wireless power transfer, using realistic antenna models and error sources, providing new analytical expressions for coverage probability and harvested energy.

Contribution

It introduces two beam alignment error models, derives their impact on antenna gain distributions, and provides analytical formulas for energy coverage and harvesting performance under these errors.

Findings

Beam alignment errors significantly degrade WPT performance.

Gaussian antenna model offers more accurate analysis than flat-top model.

Derived analytical expressions match simulation results, confirming the impact of BAE.

Abstract

In this paper, the impact of imperfect beam alignment (IBA) on millimeter wave (mmWave) wireless power transfer (WPT) is investigated. We consider a mmWave WPT network, where the location of the energy transmitters follows a Poisson point process. Instead of the mostly used flat-top antenna model, we adopt the Gaussian antenna model suggested by the 3rd Generation Partnership Project (3GPP) for better accuracy. Two beam alignment error (BAE) models, i.e., truncated Gaussian and uniform models, are introduced to represent different BAE sources. We derive the probability density functions (PDFs) of the cascaded antenna gain with both BAE models and then provide the approximated PDFs for tractability. With the help of Fox's H function, the analytic expression for the energy coverage probability with nonlinear energy harvesting model is derived. Besides, we deduce a closed-form expression of the average harvested radio frequency (RF) energy. The simulation results verify our theoretical results and demonstrate the performance degradation incurred by BAE. It also shows that the flat-top antenna model cannot always provide accurate performance evaluation in the presence of BAE.