Performance Comparison between OOK, PPM and PAM Modulation Schemes for Free Space Optical (FSO) Communication Systems: Analytical Study

Abstract

As wireless communication systems become ever-more important and pervasive parts of our everyday life; system capacity and quality of service issues are becoming more critical. In order to increase the system capacity and improve the quality of service, it is necessary that we pay closer attention to bandwidth and power efficiency issues. In this paper, the bandwidth and power efficiency issues in Free Space Optics (FSO) transmissions are addressed under Pulse Position Modulation (L-PPM) and Pulse Amplitude Modulation (M-PAM) schemes, and their performance in terms of power and bandwidth efficiencies and the Bit Error Rate (BER) versus Signal-to-Noise Ratio (SNR) are compared analytically. The comparative study of the L-PPM and MPAM schemes is discussed, and showed that for similar SNR, L-PPM scheme offered improved performance. For FSO communication systems, although the power efficiency is inferior to L-PPM scheme, On-Off Keying (OOK) modulation scheme is more commonly used due to its efficient bandwidth usage, but M-PAM is the bandwidth efficient modulation scheme in this research for more than “2” bits of information can be sent, while L-PPM is the power efficient modulation scheme for more number of bits can be sent, and it may be able to improve performance by increasing the number of bits in L-PPM scheme. General Terms Optical Communications, Modulation schemes, Bit Error Rate (BER), Signal to Noise Ratio (SNR), Bandwidth Efficiency, Power Efficiency.