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Leveraging IRS Induced Time Delay for Enhanced Physical Layer Security in VLC Systems

Rashid Iqbal, Mauro Biagi, Ahmed Zoha, Muhammad Ali Imran, Hanaa Abumarshoud

TL;DR

The paper addresses security in indoor VLC by leveraging IRS-induced time delay to enhance physical layer security. It models a downlink VLC system with a single LED, legitimate user, eavesdropper, and a grid of IRS elements, incorporating LoS and NLoS paths and the resulting time delays into the channel response. The authors formulate a secrecy-rate maximization problem $C_s = R_B - R_E$ with a binary IRS allocation vector and solve it using a binary genetic algorithm, demonstrating significant secrecy gains (up to 253.7% at low power) and rapid convergence. The approach reveals that constructive and destructive ISI patterns created by time-delayed IRS reflections can decisively improve PLS in VLC, even when the eavesdropper is close to the LED, highlighting practical potential for secure VLC deployments.

Abstract

Indoor visible light communication (VLC) is considered secure against attackers outside the confined area where the light propagates, but it is still susceptible to interception from inside the coverage area. A new technology, intelligent reflecting surfaces (IRS), has been recently introduced, offering a way to enhance physical layer security (PLS). Most research on IRS-assisted VLC assumes the same time of arrival from all reflecting elements and overlooks the effect of time delay and the associated intersymbol interference. This paper tackles, for the first time, the effect of time delay on the secrecy rate in VLC systems. Our results show that, at a fixed light-emitting diode (LED) power of 3W, the secrecy rate can be enhanced by up to 253\% at random positions for the legitimate user when the eavesdropper is located within a 1-meter radius of the LED. Our results also show that careful allocation of the IRS elements can lead to enhanced PLS even when the eavesdropper has a more favourable position and, thus, a better channel gain than the legitimate user.

Leveraging IRS Induced Time Delay for Enhanced Physical Layer Security in VLC Systems

TL;DR

The paper addresses security in indoor VLC by leveraging IRS-induced time delay to enhance physical layer security. It models a downlink VLC system with a single LED, legitimate user, eavesdropper, and a grid of IRS elements, incorporating LoS and NLoS paths and the resulting time delays into the channel response. The authors formulate a secrecy-rate maximization problem with a binary IRS allocation vector and solve it using a binary genetic algorithm, demonstrating significant secrecy gains (up to 253.7% at low power) and rapid convergence. The approach reveals that constructive and destructive ISI patterns created by time-delayed IRS reflections can decisively improve PLS in VLC, even when the eavesdropper is close to the LED, highlighting practical potential for secure VLC deployments.

Abstract

Indoor visible light communication (VLC) is considered secure against attackers outside the confined area where the light propagates, but it is still susceptible to interception from inside the coverage area. A new technology, intelligent reflecting surfaces (IRS), has been recently introduced, offering a way to enhance physical layer security (PLS). Most research on IRS-assisted VLC assumes the same time of arrival from all reflecting elements and overlooks the effect of time delay and the associated intersymbol interference. This paper tackles, for the first time, the effect of time delay on the secrecy rate in VLC systems. Our results show that, at a fixed light-emitting diode (LED) power of 3W, the secrecy rate can be enhanced by up to 253\% at random positions for the legitimate user when the eavesdropper is located within a 1-meter radius of the LED. Our results also show that careful allocation of the IRS elements can lead to enhanced PLS even when the eavesdropper has a more favourable position and, thus, a better channel gain than the legitimate user.
Paper Structure (7 sections, 14 equations, 6 figures, 1 table, 1 algorithm)

This paper contains 7 sections, 14 equations, 6 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model
  3. LoS Channel
  4. NLoS Channel
  5. Problem Formulation and Proposed Solution
  6. Simulation Results
  7. Conclusion

Figures (6)

  • Figure 1: System model of an indoor irs-assisted VLC system with one legitimate user and one eavesdropper.
  • Figure 2: Convergence rate of Algorithm \ref{['alg:GA']} for different IRS sizes.
  • Figure 3: The average data rate of Bob and Eve for random locations across the room.
  • Figure 4: Average secrecy capacity for uniformly distributed location.
  • Figure 5: Average data rate at random positions with Eve positioned within the LED's inner zone
  • ...and 1 more figures