A Comparative Performance Analysis of Different Modulations in IM/DD Wireless Communication Systems

In this paper, the performances of the ACO-OFDM waveform, one of the optical OFDM waveforms developed for IM/DD wireless communication systems, are analyzed in the multipath fading ceiling bounce optical channel environment with different modulations such as M-CSK and M-QAM modulations. Channel coding techniques such as Reed Solomon (RS) and 1/2 rate convolutional encoder (CC) are utilized to improve the bit error rate (BER) performance of the ACO-OFDM waveform. The performances of the RS and 1/2 CC encoded ACO-OFDM waveform using M-CSK and M-QAM modulations are compared over the BER-SNR performance metric in the 5-tap ceiling bounce wireless optical channel environment. From the produced numerical results, it is seen that nearly 2.5 dB SNR difference occurs between M-CSK and M-QAM modulations. Also, it is observed that 1/2 CC channel coding is approximately 2-3 dB better than RS channel coding.