A novel m-level modulation technique built on the spreading method for visible light communication

In this study, a novel spread-based optical OFDM waveform is proposed for intensity modulation/direct detection (IM/DD) communication systems. The proposed waveform is a combination of the spreading technique and the Flip OFDM waveform (Spread Flip OFDM, s-Flip OFDM). Simulation studies are carried out to evaluate the performance of the proposed waveform and compare it with optical OFDM waveforms such as Flip OFDM, DCO-OFDM and VLC-OFDM. In addition, the effect of the proposed spreading technique on other optical OFDM waveforms is analyzed in the presented study. It is understood that the proposed spreading technique provides a gain in the range of 5 to 10 dB SNR to the performance of optical OFDM waveforms in AWGN channel and diffused optical wireless channel environments, where ceiling bounce, exponential decay and exponential risen channel models are used. From the obtained numerical results, it is seen that the proposed s-Flip OFDM waveform is approximately 10 dB superior than the s-DCO-OFDM waveform and 15 dB superior than the s-VLC-OFDM waveform in both AWGN and diffused multipath optical environments.