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Zero-Energy Reconfigurable Intelligent Surfaces (zeRIS)

Dimitrios Tyrovolas, Sotiris A. Tegos, Vasilis K. Papanikolaou, Yue Xiao, Prodromos-Vasileios Mekikis, Panagiotis D. Diamantoulakis, Sotiris Ioannidis, Christos K. Liaskos, George K. Karagiannidis

TL;DR

This paper addresses designing energy-efficient wireless networks using zero-energy RISs (zeRIS) that harvest energy from RF signals to power themselves while enabling beam-steering. It introduces three harvest-and-reflect methods—power splitting (PS), time switching (TS), and element splitting (ES)—and analyzes two deployment scenarios (BS-side and UE-side zeRIS). It derives closed-form, tractable expressions for the joint energy-data rate outage probability $P_{q_1}^{q_2}$ and the energy efficiency $\mathcal{E}_{q_1}^{q_2}$, employing moment-matching and distributional approximations (erf, incomplete gamma, and Nakagami) and validates them with simulations. The results reveal that the optimal HaR strategy depends on zeRIS placement and channel conditions, with PS often providing higher energy efficiency in LoS BS-side deployments, while TS/ES offer robustness in UE-side or challenging channels. These findings offer design guidelines for deploying zeRISs in future programmable wireless environments and point to directions for extending the framework to active RIS configurations.

Abstract

A primary objective of the forthcoming sixth generation (6G) of wireless networking is to support demanding applications, while ensuring energy efficiency. Programmable wireless environments (PWEs) have emerged as a promising solution, leveraging reconfigurable intelligent surfaces (RISs), to control wireless propagation and deliver exceptional quality-ofservice. In this paper, we analyze the performance of a network supported by zero-energy RISs (zeRISs), which harvest energy for their operation and contribute to the realization of PWEs. Specifically, we investigate joint energy-data rate outage probability and the energy efficiency of a zeRIS-assisted communication system by employing three harvest-and-reflect (HaR) methods, i) power splitting, ii) time switching, and iii) element splitting. Furthermore, we consider two zeRIS deployment strategies, namely BS-side zeRIS and UE-side zeRIS. Simulation results validate the provided analysis and examine which HaR method performs better depending on the zeRIS placement. Finally, valuable insights and conclusions for the performance of zeRISassisted wireless networks are drawn from the presented results.

Zero-Energy Reconfigurable Intelligent Surfaces (zeRIS)

TL;DR

This paper addresses designing energy-efficient wireless networks using zero-energy RISs (zeRIS) that harvest energy from RF signals to power themselves while enabling beam-steering. It introduces three harvest-and-reflect methods—power splitting (PS), time switching (TS), and element splitting (ES)—and analyzes two deployment scenarios (BS-side and UE-side zeRIS). It derives closed-form, tractable expressions for the joint energy-data rate outage probability and the energy efficiency , employing moment-matching and distributional approximations (erf, incomplete gamma, and Nakagami) and validates them with simulations. The results reveal that the optimal HaR strategy depends on zeRIS placement and channel conditions, with PS often providing higher energy efficiency in LoS BS-side deployments, while TS/ES offer robustness in UE-side or challenging channels. These findings offer design guidelines for deploying zeRISs in future programmable wireless environments and point to directions for extending the framework to active RIS configurations.

Abstract

A primary objective of the forthcoming sixth generation (6G) of wireless networking is to support demanding applications, while ensuring energy efficiency. Programmable wireless environments (PWEs) have emerged as a promising solution, leveraging reconfigurable intelligent surfaces (RISs), to control wireless propagation and deliver exceptional quality-ofservice. In this paper, we analyze the performance of a network supported by zero-energy RISs (zeRISs), which harvest energy for their operation and contribute to the realization of PWEs. Specifically, we investigate joint energy-data rate outage probability and the energy efficiency of a zeRIS-assisted communication system by employing three harvest-and-reflect (HaR) methods, i) power splitting, ii) time switching, and iii) element splitting. Furthermore, we consider two zeRIS deployment strategies, namely BS-side zeRIS and UE-side zeRIS. Simulation results validate the provided analysis and examine which HaR method performs better depending on the zeRIS placement. Finally, valuable insights and conclusions for the performance of zeRISassisted wireless networks are drawn from the presented results.
Paper Structure (18 sections, 6 theorems, 56 equations, 6 figures, 1 table)

This paper contains 18 sections, 6 theorems, 56 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. State-of-the-art and Motivation
  3. Contribution
  4. Structure
  5. Zero-Energy Reconfigurable Intelligent Surface (zeRIS)
  6. zeRIS Architecture
  7. System Model
  8. zeRIS-HaR Methods
  9. Power splitting
  10. Time switching
  11. Element splitting
  12. zeRIS Deployment
  13. Theoretical Analysis
  14. BS-side zeRIS
  15. UE-side zeRIS
  16. ...and 3 more sections

Key Result

Proposition 1

The joint energy-data rate outage probability for a BS-side zeRIS that applies the PS technique can be approximated as with where $\mathrm{erf}(\cdot)$ is the error function. Moreover, where $K\approx \frac{\sqrt{m^2 - m}}{m - \sqrt{m^2-m}}$ is the Rice factor, and $\kappa\in \left[0, \infty\right)$ is the von Mises concentration parameter.

Figures (6)

  • Figure 1: zeRIS-HaR methods
  • Figure 2: Joint energy-data rate outage probability for BS-side zeRIS with $R_{\mathrm{thr}}$=$3.46$ bit/s/Hz
  • Figure 3: Joint energy-data rate outage probability for UE-side zeRIS with $R_{\mathrm{thr}}$=$3.46$ bit/s/Hz
  • Figure 4: Analysis of minimum reflecting elements for: (a) BS-side zeRIS with $d_2=60-d_1$ and $R_{\mathrm{thr}}=1$ bit/s/Hz, (b) UE-side zeRIS with $d_1=60-d_2$ and $R_{\mathrm{thr}}=1$ bit/s/Hz.
  • Figure 5: Energy efficiency versus transmit power for a BS-side zeRIS with $N=275$ and $R_{\mathrm{thr}}=3.46$ bit/s/Hz.
  • ...and 1 more figures

Theorems & Definitions (13)

  • Definition 1
  • Definition 2
  • Remark 1
  • Proposition 1
  • Proposition 2
  • Remark 2
  • Proposition 3
  • Remark 3
  • Proposition 4
  • Remark 4
  • ...and 3 more