Physical-layer Security for Indoor Visible Light Communications: Secrecy Capacity Analysis

TL;DR

This paper derives and analyzes the secrecy capacity bounds for indoor visible light communication networks under various optical intensity constraints, providing insights into secure communication performance at high SNR.

Contribution

It presents the first closed-form bounds on secrecy capacity for VLC with intensity constraints and analyzes their asymptotic behavior at high SNR.

Findings

Bounds on secrecy capacity are tight and validated by numerical results.

Asymptotic bounds coincide when both average and peak constraints are considered.

High SNR analysis reveals small gaps or exact bounds depending on constraints.

Abstract

This paper investigates the physical-layer security for an indoor visible light communication (VLC) network consisting of a transmitter, a legitimate receiver and an eavesdropper. Both the main channel and the wiretapping channel have nonnegative inputs, which are corrupted by additive white Gaussian noises. Considering the illumination requirement and the physical characteristics of lighting source, the input is also constrained in both its average and peak optical intensities. Two scenarios are investigated: one is only with an average optical intensity constraint, and the other is with both average and peak optical intensity constraints. Based on information theory, closed-form expressions of the upper and lower bounds on secrecy capacity for the two scenarios are derived. Numerical results show that the upper and lower bounds on secrecy capacity are tight, which validates the derived closed-form expressions. Moreover, the asymptotic behaviors in the high signal-to-noise ratio (SNR) regime are analyzed from the theoretical aspects. At high SNR, when only considering the average optical intensity constraint, a small performance gap exists between the asymptotic upper and lower bounds on secrecy capacity. When considering both average and peak optical intensity constraints, the asymptotic upper and lower bounds on secrecy capacity coincide with each other. These conclusions are also confirmed by numerical results.