Performance analysis of FSO using relays and spatial diversity under log-normal fading channel

TL;DR

This paper analyzes the performance of multi-hop MISO and SISO FSO systems with relays and spatial diversity under log-normal fading, showing significant BER and SNR improvements with M-QAM modulation validated by simulations.

Contribution

It provides exact closed-form BER expressions for M-QAM in multi-hop MISO FSO systems and compares their performance with other modulation schemes under atmospheric turbulence.

Findings

Multi-hop MISO and SISO FSO systems with M-QAM outperform other schemes in BER and SNR.

Analytical results are validated through Monte-Carlo simulations.

Spatial diversity and relays significantly enhance FSO system performance.

Abstract

The performance analysis of free space optical communication (FSO) system using relays and spatial diversity at the source is studied in this paper. The effect of atmospheric turbulence and attenuation, caused by different weather conditions and geometric losses, has also been considered for analysis. The exact closed-form expressions are presented for bit error rate (BER) of M-ary quadrature amplitude modulation (M-QAM) technique for multi-hop multiple-input single-output (MISO) FSO system under log-normal fading channel. Furthermore, the link performance of multi-hop MISO and multi-hop single-input and single-output (SISO) FSO systems are compared to the different systems using on-off keying (OOK), repetition codes (RCs) and M-ary pulse amplitude modulation (M-PAM) techniques. A significant performance enhancement in terms of BER analysis and SNR gains is shown for multi-hop MISO and multi-hop SISO FSO systems with M-QAM over other existing systems with different modulation schemes. Moreover, Monte-Carlo simulations are used to validate the accuracy and consistency of the derived analytical results. Numerical results show that M-QAM modulated multi-hop MISO and multi-hop SISO FSO system with relays and spatial diversity outperforms other systems while having the same spectral efficiency of each system.