Abstract
The capacity of the multiple-input single-output (MISO) free-space
optical channel with a per-antenna peak-power constraint and a sum
(over all antennas) average-power constraint is studied. The
asymptotic low-signal-to-noise-ratio (low-SNR) capacity is
determined exactly and close upper and lower bounds are presented
in the low- and moderate-SNR regimes. The asymptotic low-SNR
limit is achieved by having each transmit antenna signal either
with zero or with the maximally allowed peak power, and the latter
only if all stronger antennas also send at maximum peak power. In
particular, for almost all channel gains, the input to achieve the
asymptotic low-SNR capacity is such that its projection on the
channel-gain vector has only two or three positive probability
point masses, one of them being at zero. The lower bounds at
finite SNR are numerical and are obtained using input
distributions whose projection on the channel-gain vector has
either two, three, or four positive probability masses. Finally,
the paper presents two analytic upper bounds on the capacity of
the MISO channel: the first one closely follows the proposed
numerical lower bounds in the low-SNR regime, and the second one
can improve on previous bounds in the moderate-SNR regime.
-||- _|_ _|_ / __|__ 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 13:50:42 CET 2020