Benchmarking Mitigation Techniques for SISO OOK-FSO Links Under Gamma-Gamma Turbulence, Pointing Errors and Temporal Correlation

Abstract

On-off keying (OOK) based free-space optical (FSO) links can provide the fiber-like capacity of wireless backhaul, but their performance is severely degraded by the scintillation of irradiance, misalignment and time persistence of fading. It presents a benchmarking system based on impairment consistency of SISO OOK-FSO transmission through Gamma-Gamma turbulence, and explicitly considers the Rayleigh pointing jitter, and AR(1)temporal correlation. We measure the reliability effect of fixed-threshold (FT) detection and compare it to three popular countermeasures by the receiver (adaptive thresholding (AT), aperture averaging (AA), and diversity combining (SC/EGC/MRC)). Under the same link/noise assumptions, we compare the reliability effect of each of these countermeasures. To effectively sample low-error regimes without any intimidatingly long bit-level simulations, we use a conditional-BER averaging (semi-analytical Monte Carlo) scheme on a large number of realizations of channels (e.g., NMC=50,000). The findings prove that FT detection gets strong error floors in a joint impairment case (e.g., ≈2.5×10−4even in weak turbulence), whereas AT suppresses the floor and attains ∼10−6around ∼28 dB for Cn2=5×10−15. In Gamma-Gamma fading, AA achieves a definite SNR gain (about 8–9 dB at 10−5for Cn2=10−15) and can be used in regimes where a point receiver cannot function, whereas MRC can give improvement of up to ∼11 dB improvement at 10−5at moderate turbulence. In general, the experiment has shown useful selection-based guidelines in selecting mitigation strategies to terrestrial SISO OOK-FSO links under combined realistic impairments.