New upper and lower bounds are presented on the capacity of the
free-space optical intensity channel. This channel is characterized by
inputs that are nonnegative (representing the transmitted optical
intensity) and by outputs that are corrupted by additive white
Gaussian noise (because in free space the disturbances arise from many
independent sources). Due to battery and safety reasons the inputs
are simultaneously constrained in both their average and peak
power. For a fixed ratio of the average power to the peak power the
difference between the upper and the lower bounds tends to zero as the
average power tends to infinity, and the ratio of the upper and lower
bounds tends to one as the average power tends to zero.

The case where only an average-power constraint is imposed on the
input is treated separately. In this case, the difference of the upper
and lower bound tends to 0 as the average power tends to infinity, and
their ratio tends to a constant as the power tends to zero.

-||-   _|_ _|_     /    __|__   Stefan M. Moser
[-]     --__|__   /__\    /__   Senior Researcher & Lecturer, ETH Zurich, Switzerland
_|_     -- --|-    _     /  /   Adj. Professor, National Chiao Tung University (NCTU), Taiwan
/ \     []  \|    |_|   / \/    Web: http://moser-isi.ethz.ch/

Last modified: Sat Oct 13 06:41:50 UTC+8 2007