Performance analysis of optical spatial modulation over a correlated gamma–gamma turbulence channel

In this paper, theoretical closed expressions for the symbol error rate (SER) of two optical spatial modulation (OSM) schemes in a free-space optical (FSO) communication system—optical spatial pulse amplitude modulation (OSPAM) and optical spatial pulse position modulation (OSPPM)—over correlated gamma–gamma fading channels are derived. To study practical optical channels affected by atmospheric eddies, the effect of arbitrary atmospheric channel correlation is considered particularly, and it is shown that the correlation can degrade system performance. The parameters of atmospheric turbulence and the number of optical antennas are also under consideration in performance analysis of the FSO multiple input, multiple output system. All analytical results are validated with Monte Carlo simulations, which clearly illustrate the effect of spatial constellation and signal constellation on the average SER. In addition, it is shown by comparison that turbulence fluctuation and channel correlation have less influence on the OSPPM system than the OSPAM system. Overall, the framework proposed in this paper is proven to be effective and conducive to algorithm research on reducing the effect of correlated channels on OSM FSO systems.