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Location-Driven Programmable Wireless Environments through Light-emitting RIS (LeRIS)

Dimitrios Bozanis, Dimitrios Tyrovolas, Vasilis K. Papanikolaou, Sotiris A. Tegos, Panagiotis D. Diamantoulakis, Christos K. Liaskos, Robert Schober, George K. Karagiannidis

TL;DR

This work tackles the challenge of real-time, orientation-robust RIS operation in indoor PWEs by introducing a light-emitting RIS (LeRIS) that pairs ceiling LEDs with RIS-mounted LEDs to create diverse optical paths. A closed-form optical RSS-based localization framework is derived to estimate the UE position under arbitrary orientation, accompanied by geometric constraints on LED placement to guarantee a unique solution, enabling a localization-driven LATC approach. The LATC framework then uses the estimated UE location to configure RIS phase shifts for precise beam steering, and simulations show high spectral efficiency and resilience to hardware imperfections and position offsets, especially when larger RISs are used. The proposed LED+LeRIS deployment provides a scalable, adaptive solution for real-time PWE operation in 6G networks, addressing practical localization and misalignment challenges while enabling robust RIS control.

Abstract

As 6G wireless networks seek to enable robust and dynamic programmable wireless environments (PWEs), reconfigurable intelligent surfaces (RISs) have emerged as a cornerstone for controlling electromagnetic wave propagation. However, realizing the potential of RISs for demanding PWE applications depends on precise and real-time user localization, especially in scenarios with random receiver orientations and inherent hardware imperfections. To address this challenge, we propose a novel optical localization framework that integrates conventional ceiling-mounted LEDs with light-emitting reconfigurable intelligent surfaces (LeRISs). By leveraging the spatial diversity offered by the LeRIS architecture, the framework introduces robust signal paths that improve localization accuracy and reduce errors under varying orientations. To this end, we derive a system of equations for received signal strength-based localization that accounts for random receiver orientations and imposes spatial constraints on LED placement, ensuring unique and reliable solutions. Finally, our simulation results demonstrate that the proposed framework achieves precise beam control and high spectral efficiency even for RISs with large number of reflecting elements, establishing our solution as scalable and adaptive for PWEs that require real-time accuracy and flexibility.

Location-Driven Programmable Wireless Environments through Light-emitting RIS (LeRIS)

TL;DR

This work tackles the challenge of real-time, orientation-robust RIS operation in indoor PWEs by introducing a light-emitting RIS (LeRIS) that pairs ceiling LEDs with RIS-mounted LEDs to create diverse optical paths. A closed-form optical RSS-based localization framework is derived to estimate the UE position under arbitrary orientation, accompanied by geometric constraints on LED placement to guarantee a unique solution, enabling a localization-driven LATC approach. The LATC framework then uses the estimated UE location to configure RIS phase shifts for precise beam steering, and simulations show high spectral efficiency and resilience to hardware imperfections and position offsets, especially when larger RISs are used. The proposed LED+LeRIS deployment provides a scalable, adaptive solution for real-time PWE operation in 6G networks, addressing practical localization and misalignment challenges while enabling robust RIS control.

Abstract

As 6G wireless networks seek to enable robust and dynamic programmable wireless environments (PWEs), reconfigurable intelligent surfaces (RISs) have emerged as a cornerstone for controlling electromagnetic wave propagation. However, realizing the potential of RISs for demanding PWE applications depends on precise and real-time user localization, especially in scenarios with random receiver orientations and inherent hardware imperfections. To address this challenge, we propose a novel optical localization framework that integrates conventional ceiling-mounted LEDs with light-emitting reconfigurable intelligent surfaces (LeRISs). By leveraging the spatial diversity offered by the LeRIS architecture, the framework introduces robust signal paths that improve localization accuracy and reduce errors under varying orientations. To this end, we derive a system of equations for received signal strength-based localization that accounts for random receiver orientations and imposes spatial constraints on LED placement, ensuring unique and reliable solutions. Finally, our simulation results demonstrate that the proposed framework achieves precise beam control and high spectral efficiency even for RISs with large number of reflecting elements, establishing our solution as scalable and adaptive for PWEs that require real-time accuracy and flexibility.

Paper Structure

This paper contains 14 sections, 4 theorems, 42 equations, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. State of the Art
  3. Motivation and Contribution
  4. Structure of Paper
  5. System Model
  6. LED-empowered PWE
  7. LATC Scheme for LED-powered PWEs
  8. Localization-Driven Beam Steering
  9. Optical RSS-based LATC Scheme
  10. System Model for Optical Localization
  11. RSS-based Positioning
  12. LATC-based RIS Configuration
  13. Simulation Results
  14. Conclusions

Key Result

Lemma 1

The UE position can be determined using the optical RSS-based method if it has LoS links with four LEDs placed on a plane, provided that no two LEDs are equidistant from the UE when this plane is parallel to the UE plane.

Figures (6)

  • Figure 1: Programmable wireless environment with ceiling LEDs and Light-emitting RIS (LeRIS).
  • Figure 2: Localization error $\Delta d$ for varying azimuth angle $\theta_\mathrm{UE}$.
  • Figure 3: Localization error $\Delta d$ versus $K_{\mathrm{PWE}}$ for various $m_l$ values.
  • Figure 4: Achievable spectral efficiency $R$ versus $K_{\mathrm{PWE}}$ for various LeRIS sizes.
  • Figure 5: Effect of LeRIS hardware imperfection on (a) Achievable spectral efficiency $R$ for various $K_{\mathrm{PWE}}$ values, (b) LeRIS gain $G$ for $N=1600$, and (c) LeRIS gain $G$ for $N=100$.
  • ...and 1 more figures

Theorems & Definitions (7)

  • Lemma 1
  • Remark 1
  • Remark 2
  • Proposition 1
  • Remark 3
  • Proposition 2
  • Proposition 3