Performance enhancement of BPSK-SIM- and DPSK-SIM-based FSO downlink over atmospheric turbulence using aperture averaging and receiver diversity

Abstract

In this paper, we evaluate the bit error rate (BER) performance of a free-space optical satellite downlink by considering the atmospheric turbulence effects using binary shift keying subcarrier intensity modulation and differential phase shift keying subcarrier intensity modulation (DPSK-SIM). The performance of the link is enhanced using aperture averaging and receiver diversity. The closed form mathematical expressions of BER for BPSK-SIM and DPSK-SIM schemes are derived and analyzed. It is observed that on varying the turbulence level, the performance of the link degrades when the turbulence level increases. The improved BER of 10?12 and 10?10 at signal-to-noise ratio of 30 dB of the link for both BPSK-SIM and DPSK-SIM is obtained by using aperture averaging (aperture diameter, D = 10 cm) and receiver diversity with optimal combining. 2019, Springer Science+Business Media, LLC, part of Springer Nature.