BER Performance Improvement using Spatial Diversity Combining in an Atmospheric Turbulent Channel with Satellite Vibration-Induced Fading

Atmospheric turbulence is a major impediment in the successful establishment of free space optical (FSO) communication from satellite to ground. To mitigate its effects, spatial diversity is considered as a solution wherein receivers are placed far enough such that atmospheric turbulence influence is uncorrelated between them. Most studies, however, treat the effect of atmospheric turbulence and internal satellite vibrations separately which might underestimate the expected beam fading. In the paper, we assess multiple diversity combining techniques in satellite-to-ground optical communications where both atmospheric turbulence and satellite-induced pointing errors are present. A model encompassing the influence of afore-mentioned error sources to the bit error rate (BER) is proposed. Furthermore, the performance is evaluated in different atmospheric turbulence conditions to examine the robustness of spatial diverse systems compared to the no diversity case.