Covert transmission performance for visible light communications under optical intensity and covert constraints

Abstract

This paper investigates the fundamental performance limit for an indoor covert visible light communication (VLC) system consisting of a transmitter, a receiver, and a warden. In the system, the input signal of VLC is constrained by nonnegativity, peak optical intensity constraint, average optical intensity constraint and covertness constraint. We derive the optimal distribution of the input signal by using the variational method and the entropy power inequality. The allowable maximum peak optical intensity is obtained by substituting the optimal input signal into the covertness constraint. Then, by substituting the maximum peak optical intensity into the lower bound of the maximum mutual information, we derive an upper bound of the information bits that can be covertly transmitted. The asymptotic analysis shows that the upper bound on the transmittable covert information bits tends to a constant when the number of channel uses tends to infinity. These conclusions are also confirmed by numerical results.