Filtered OFDM for underwater wireless optical communication

Underwater optical wireless communication (UOWC) has been a promising high data rate communication system. The performance of UOWC has numerous constraints in terms of maximum attainable distance, absorption, and scattering of the intensity, which vary depending on the quality of the water environment. This paper proposes a UOWC system based on filtered orthogonal frequency division multiplexing (F-OFDM). It has achieved large bandwidth while also addressing the issue of intersymbol interference (ISI). F-OFDM has attained lower out-of-band emission (OOB) while preserving bit error rate (BER) performance. Furthermore, to permit many users to share the entire UOWC system, non-orthogonal multiple access (NOMA) is adopted with F-OFDM, taking advantage of filtering subcarriers that reduce user interference. NOMA F-OFDM has been examined across harbor water channels under different power coefficients and modulation. Simulations have shown that F-OFDM is better than DC-biased optical OFDM (DCO-OFDM), with an OOB improvement of about 120 dB and a signal-to-noise ratio (SNR) gain of about 13 dB for BER = 10–3 using 4-QAM modulation. As well, NOMA F-OFDM has better BER performance than NOMA DCO-OFDM.