BER Performance of Free-Space Optical Transmission with Spatial Diversity

TLDR

Free‑space optical communication offers cost‑effective, high‑bandwidth access, yet turbulence‑induced fading severely degrades link performance. The study investigates how deploying multiple laser transmitters and receivers (spatial diversity) can mitigate turbulence‑induced fading and improve the bit‑error‑rate performance of FSO links over log‑normal atmospheric turbulence channels. Analytical BER expressions are derived using an approximation to the sum of correlated log‑normal random variables to model spatially correlated and independent channel scenarios. The resulting BER formulas quantify how spatial diversity and spatial correlation affect performance in log‑normal turbulence channels.

Abstract

Free space optical (FSO) communications is a cost-effective and high bandwidth access technique, which has been receiving growing attention with recent commercialization successes. A major impairment in FSO links is the turbulence- induced fading which severely degrades the link performance. To mitigate turbulence-induced fading and, therefore, to improve the error rate performance, spatial diversity can be used over FSO links which involves the deployment of multiple laser transmitters/receivers. In this paper, we investigate the bit error rate (BER) performance of FSO links with spatial diversity over log- normal atmospheric turbulence fading channels, assuming both independent and correlated channels among transmitter/receiver apertures. Our analytical derivations build upon an approximation to the sum of correlated log-normal random variables. The derived BER expressions quantify the effect of spatial diversity and possible spatial correlations in a log-normal channel.