CSK-Based DCO-OTFS for Visible Light Communications

Abstract

This paper investigates a color shift keying (CSK)-based direct-current-biased optical orthogonal time frequency space (DCO-OTFS) waveform for visible light communica-tions (VLC) systems. In the proposed structure, red-green-blue (RGB) intensity components generated by 8CSK modulation are mapped onto a Hermitian-symmetric DCO-OTFS frame to obtain an intensity modulation/direct detection (IM/DD)-compatible non-negative optical signal. After evaluating differ-ent direct-current (DC) bias levels, the bit error rate (BER) and peak-to-average power ratio (PAPR) analyses are performed at a 10 dB bias level. Simulation results show that DCO-OTFS-8CSK achieves comparable BER performance to direct-current-biased optical orthogonal frequency division multiplex-ing (DCO-OFDM) in additive white Gaussian noise (AWGN) channels, while providing clear signal-to-noise ratio (SNR) gains under static multipath optical channels. The results also include quadrature amplitude modulation (QAM)-based benchmarks and show that DCO-OTFS-8CSK significantly reduces PAPR compared with DCO-OFDM-based schemes. These results in-dicate that CSK-based DCO-OTFS is a promising waveform candidate for reliable and power-efficient VLC systems.