Performance analysis of radio-over-free-space optical communication system with spatial diversity over combined channel model

Abstract

Radio over Free Space Optical (RoFSO) communication is accepted as one of the promising technologies in communication systems that can fulfill the demands of high bandwidth and high data rate because it has an inherent quality of transmission capacity significantly more than what is provided by radio transmission technologies. It is a low power, high data rate, unlicensed spectrum, and large bandwidth wireless technology. Nevertheless, the full potential of the RoFSO communication system can be utilized only by overcoming the adverse effects of the atmospheric channel, which are scattering, absorption, and turbulence. Pointing error is also another factor responsible for the deterioration of the performance of the RoFSO system. In this paper, spatial diversity at the transmitting and receiving ends is used to improve the performance of the RoFSO system in various turbulence and weather conditions. The Malaga distribution has been used to model atmospheric turbulence. For single input single output (SISO), single input Multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO) configurations, closed form expressions for average bit error rate (BER) have been estimated. To improve the performance of the proposed system, the two combining techniques, Optimal Combining and Equal Gain Combining, are being considered. The results obtained are compared to various configurations such as SISO, SIMO, MISO, and MIMO cases. The result shows that MIMO offers better average BER performance compared with SISO, SIMO and MISO cases. The 4 × 4 MIMO case has an average BER of 10 - 9 at an average SNR of 25 dB, but the SISO case has an average BER of 10 - 1 at the same average SNR. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.