Comparison of Bit Error Rate Performance of Different Modulation Techniques over Turbulent FSO Link

Abstract

Free space optical (FSO) communication link is a line of sight (LOS) wireless link between the nodes separated by an unguided medium such that visible and infrared bands of the spectrum are used as data carrier. Recent past has witnessed huge revival of research interest in this field so as to make FSO commercially viable and looking into this prospective, data modulation techniques are one of the primary ways to enhance link sustainability. In this paper, comparison of modulation techniques like M-ary QAM, BPSK and DPSK has been studied by creating turbulent atmospheric conditions using gamma-gamma turbulence model. During this link analysis, BPSK performed far better in comparison to DPSK and M-ary QAM in terms of BER for similar SNR values and interestingly, higher the order of M-QAM and higher the link range, greater was the degradation of link performance observed.