Secrecy Capacity Bounds for Visible Light Communications With Signal-Dependent Noise

TL;DR

This paper derives tight bounds on the secrecy capacity of indoor visible light communication systems considering signal-dependent noise, providing insights into physical-layer security under various optical constraints.

Contribution

It introduces new bounds on secrecy capacity considering both signal-dependent noise and optical intensity constraints, advancing physical-layer security analysis for VLC systems.

Findings

Secrecy capacity bounds are tight and asymptotically close at high optical intensities.

Adding peak optical intensity constraints refines the capacity bounds.

Numerical results verify the theoretical bounds' accuracy.

Abstract

In physical-layer security, one of the most fundamental issues is the secrecy capacity. The objective of this paper is to determine the secrecy capacity for an indoor visible light communication system consisting of a transmitter, a legitimate receiver and an eavesdropping receiver. In such a system, both signal-independent and signal-dependent Gaussian noises are considered. Under non-negativity and average optical intensity constraints, lower and upper secrecy capacity bounds are first derived by the variational method, the dual expression of the secrecy capacity, and the concept of "the optimal input distribution that escapes to infinity". Numerical results show that the secrecy capacity upper and lower bounds are tight. By an asymptotic analysis at large optical intensity, there is a small performance gap between the asymptotic upper and lower bounds. Then, by adding a peak optical intensity constraint, we further analyze the exact and asymptotic secrecy capacity bounds. Finally, the tightness of the derived bounds is verified by numerical results.