A Comparative Analysis of Different Modulation Techniques Based on Subcarrier Intensity Modulation in Free Space Optics Using Log-Normal Turbulence Model

Abstract

In this paper, the error rate performance of free space optics (FSO) is analyzed by employing different subcarrier-intensity modulation (SIM) based techniques like binary phase shift keying(BPSK-SIM), quadrature amplitude modulation(QAM-SIM), differential phase shift keying (DPSK-SIM). So a comparative study is presented based on bit error rate (BER) plots with respect to signal-to-noise ratio (SNR), average irradiance, scintillation index etc. The analysis has been performed by considering log-normal channel model. The simulation results are verified in Matlab with the mathematical analysis. In our work we have used Gauss-Hermite integration approximation for the BER analysis. The simulation results show that BPSK-SIM is superior to other techniques but QAM-SIM and DPSK-SIM have other advantages. So from this comparative analysis, the appropriate technique can be chosen according to the desired applications.