Hybrid DCT-DST precoding techniques for PAPR reduction in Flip-OFDM-based visible light communication systems

Visible light communication (VLC) systems have become the frontrunner of communication, and optical orthogonal frequency division multiplexing (O-OFDM), particularly its specific version called Flip-OFDM, is one of the modulation schemes of high data rate VLC. Nevertheless, one major obstacle to O-OFDM is that it has a large peak-to-average power ratio (PAPR) that causes nonlinear distortion in light emitting diodes and reduces energy efficiency. This paper offers three precoding techniques: discrete cosine transform (DCT), discrete sine transform (DST), and a combined DCT and DST, as a precoding method in reducing PAPR in Flip-OFDM-based VLC systems. We have simulated the bit error rate (BER) and PAPR for multimetric modulation orders (4–256 QAM) and the VLC channel. At 4-QAM, the DST method significantly reduces PAPR by 4.5 dB, but the DCT peak-to-average power ratio is lower. The PAPR saving was 2.8 dB at the same QAM using the hybrid DCT and DST precoding method. Additionally, hybrid precoding at 256-QAM provided the best performance BER (10 −5 dB) since it enhances power distribution and effectively lowers noise and inter-symbol interference at large constellation mapping like 256-QAM. These improvements indicate that the three precoding methods can perform well and are easy to use in VLC systems.