Abstract

This paper studies the capacity of a general multiple-input
multiple-output (MIMO) free-space optical intensity channel under
a per-input-antenna peak-power constraint and a total
average-power constraint over all input antennas. The focus
is on the scenario with more transmit than receive antennas. In
this scenario, different input vectors can yield identical
distributions at the output, when they result in the same image
vector under multiplication by the channel matrix. We first
determine the most energy-efficient input vectors that attain each
of these image vectors. Based on this, we derive an equivalent
capacity expression in terms of the image vector, and establish
new lower and upper bounds on the capacity of this channel. The
bounds match when the signal-to-noise ratio (SNR) tends to
infinity, establishing the high-SNR asymptotic capacity. We also
characterize the low-SNR slope of the capacity of this channel.

Keywords

Average- and peak-power constraint, channel capacity, direct
detection, Gaussian noise, infrared communication, multiple-input
multiple-output (MIMO) channel, optical communication.

-||-   _|_ _|_     /    __|__   Stefan M. Moser
[-]     --__|__   /__\    /__   Senior Scientist, ETH Zurich, Switzerland
_|_     -- --|-    _     /  /   Adjunct Professor, National Yang Ming Chiao Tung University, Taiwan
/ \     []  \|    |_|   / \/    Web: https://moser-isi.ethz.ch/

Last modified: Tue Feb 4 13:49:37 CET 2020