Performance Analysis Of Different Modulation Techniques In SIM Based FSO Using Different Receivers Over Turbulent Channel

This research work has carried out a theoretical analysis on various subcarrier-intensity modulation (SIM) based modulation techniques employed for free space optical (FSO) wireless communication systems. A comprehensive analysis of several modulation schemes has been considered. Those are including binary phase shift keying subcarrier intensity modulation (BPSK-SIM), M-ary phase shift keying subcarrier intensity modulation (MPSK-SIM), differential phase shift keying subcarrier intensity modulation (DPSK-SIM) and M-ary quadrature amplitude modulation subcarrier intensity modulation (M-QAM-SIM), non-coherent frequency shift keying (NCFSK-SIM), etc. In FSO wireless communication both PIN and APD receivers are included to get a comparative analysis of the system bit error rate (BER) performance. Moreover in this work, a detailed investigation considering the link attenuation factor has been included. The BER expressions are theoretically derived for the case of weak and moderate turbulent conditions using log-normal channel modeling. A detailed analysis of BER performance for the aforementioned modulation techniques is observed by varying the link distance, strength of turbulence and bit rate. Also, a thorough observation of the capacity of the BPSK-SIM in the lognormal channel model is being taken for different turbulent states.