Performance analysis of an LDPC coded FSO communication system with different modulation technique under turbulent condition

Free-space optical (FSO) communication is an attractive and cost-effective solution for high-rate image, voice, and data transmission than an RF channel. Atmospheric turbulence-induced fading is one of the main impairments affecting FSO communications. To design a high performance communication link for the atmospheric FSO channel, it is of great importance to characterize the link with proper model. Different modulation techniques have already been proposed for FSO communication in various publications. In this paper, an analytical approach is presented to evaluate the bit error rate performance of an LDPC coded FSO communication employing on-off keying (OOK), binary phase-shift keying (BPSK) and Q-ary pulse position (QPPM) as modulation technique. The performance results are evaluated in terms of bit error rate (BER). It is found that LDPC coded FSO system with QPPM provides significant coding gain over uncoded system compare than other modulation techniques.