Upper bounds on the capacity for optical intensity channels with AWGN

Abstract

The channel capacity of the optical wireless communication (OWC) systems is still a problem that has not an optimal and close-form expression, in spite of OWC can be used to achieve high data rates. This paper presents novel upper bounds on the channel capacity of an optical intensity modulated and directed detection (IM/DD) system under peak-power and average-power constraints. The channel is modeled as an additive white Gaussian noise (AWGN) optical channel. The bounds are derived based on sphere-based signal space argument. Simulation results show the proposed bounds are tight at both high and low signal-to-noise ratios (SNRs). Compared to those reported bounds, the derived bounds are better at high SNRs region in particular, and the expressions are simpler and unique for the whole range of average-to-peak-power ratio.