Contrasting MISO schemes for IM/DD FSO communications with photon-counting receivers

Abstract

In this paper, we consider the problem of Multiple-Input-Single-Output (MISO) Free-Space Optical (FSO) communications with intensity-modulation and direct-detection (IM/DD). Unlike the commonly adopted Gaussian-noise approximation, we adopt the exact Poisson statistics for the number of photons falling on the receiver. In particular, we compare three popular MISO schemes; namely, repetition coding (RC), optical spatial modulation (OSM) and spatial multiplexing (SMux). For each one of these schemes, we derive the optimal maximum-Iikelihood (ML) decoder and we contrast the schemes in terms of rate, performance, complexity, channel state information requirements and tolerance to channel estimation errors.