Receiver Optimization in Turbulent Free-Space Optical MIMO Channels With APDs and Q-ary PPM

We propose an accurate, robust avalanche photodiode (APD) receiver optimization scheme for multiple-input/multiple-output (MIMO) free-space optical links withQ-ary pulse position modulation in the presence of atmospheric turbulence. Through extensive error probability(Pₑ)analysis, we show that selecting the APD gain such that the nonfading receiver-array signal-to-noise ratio is maximized essentially minimizesPₑin turbulent MIMO channels with$M = 2$transmitters and$N = 2$receivers, for several turbulence and background-radiation levels of interest.