Performance Analysis of FSO Modulation Schemes with Diversity Reception Over Atmospheric Turbulence Channel
Free space optical (FSO) communication is a cost effective, high bandwidth access systems. The fading of the transmitted signal that induced by the channel atmospheric turbulence is the major impairment in the FSO communication link which caused severe performance degradation for different optical modulation schemes. Spatial diversity is one of the atmospheric turbulence mitigation techniques that used for improving the FSO system performance. In this paper, the BER expressions of the PPM, PAM and OOK modulation schemes over FSO atmospheric turbulence channel with log-normal distribution are derived. A significant performance improvement of the system with a proposed receiver spatial diversity technique is observed with increasing the number of receiver photodetectors for various channel turbulence level. The performance comparison analysis of the PPM and PAM schemes is shown that for the same signal intensity power, PPM offered better BER performances, although PAM scheme is shown better bandwidth performances.