Comparative Analysis of Different Modulation Schemes in Rician Fading Induced FSO Communication System

摘要

Free Space Optics is a optical communication technique which involves atmosphere or free space as the communication medium. This atmosphere may be turbulent in nature which causes fading of the signal. The channels which introduce the fading of signal are said to be fading channels. In this paper, Rician fading channel is considered, in which signal traverses through multiple paths before reaching the receiver end. The fading strength of this channel is derived in terms of noise variances for different modulation schemes (BPSK, QPSK and 16-QAM) and are figured into E_b/N_0 (energy per bit per unit noise) form. The performance of this channel is analyzed for BPSK, QPSK and 16-QAM modulation schemes with respect to channel parameters viz. BER, Electrical SNR, Outage Probability and Power margin for different E_b/N_0 values. From the results, it is observed that for efficiently transmitting signal in Rician channel with better BER performance, it should be modulated with M-PSK modulation techniques rather than M-QAM.