Quantized Zero-Energy RIS: Residual Phase Modeling and Outage Analysis

TL;DR

This paper develops an analytical framework for quantized zero-energy reconfigurable intelligent surfaces, analyzing their impact on energy harvesting, signal reflection, and outage performance under practical hardware constraints.

Contribution

It introduces a comprehensive model considering residual phase errors due to quantization, enabling accurate performance evaluation and guiding design trade-offs in zeRIS systems.

Findings

Quantization affects both energy harvesting and signal reflection.

Residual phase errors significantly influence outage probability.

The framework helps optimize phase resolution and HaR schemes.

Abstract

Zero-energy reconfigurable intelligent surfaces (zeRISs) have recently emerged as a promising solution for enabling energy-efficient and scalable programmable wireless environments (PWEs) by harvesting their operational energy from impinging radio-frequency signals. However, the operation of zeRIS-assisted systems is inherently constrained by the coupling between energy harvesting and signal reflection, a dependency that becomes more intricate under practical hardware limitations such as finite-resolution phase control. In this paper, we develop a comprehensive analytical framework for zeRIS-assisted communication systems operating under quantized phase shifts and harvest-and-reflect (HaR) schemes. Specifically, we analyze the joint energy-data rate outage probability and the energy efficiency under time switching and element splitting schemes, considering both transmitter-side and user-side deployment scenarios. By explicitly modeling the residual phase error induced by quantization and incorporating its statistical properties into the analysis, we show that quantization jointly affects energy harvesting and signal reflection, thereby inducing non-trivial trade-offs. As a result, the presented framework enables accurate performance evaluation and reveals critical design trade-offs for the selection of the phase resolution, and the applied HaR scheme in zeRIS-assisted wireless networks.