Filterless Multi-Color VLC via DC-Biased QCT

Abstract

Multi-color visible light communication (VLC) can increase throughput and enable joint lighting and communication operation, but practical color-based schemes such as color shift keying (CSK) typically rely on receiver optical filters whose nonideal passbands and spectral overlap introduce color crosstalk and significant SNR loss. This paper proposes a DC-biased quartered composite transform (QCT) transmission framework for quadrichromatic red, amber, green, blue (RAGB) luminaires that enables filterless multiple streams reception with a single photodiode. The method partitions the information symbols into four parallel real-valued streams and applies a set of mutually orthogonal QCT synthesis matrices designed from the invariances of the matched-filtered circulant channel; at the receiver, matched filtering and QCT-domain projection yield four decoupled scalar subchannels that admit single-tap equalization. A unified evaluation is carried out under common illumination constraints (CCT/CRI and illuminance uniformity) and throughput-matched configurations against RAGB-CSK and conventional DCO-OFDM baselines. In an indoor scenario, QCT attains up to 48.95 dB average effective SNR, providing 15.1-22.7 dB gain over CSK and 15.6-26.4 dB gain over DCO-OFDM, while achieving essentially identical BER to DCO-OFDM in linear AWGN. Under matched mean optical power, QCT also yields near zero clipping distortion and a consistent 0.7-1 dB PAPR reduction relative to DCO-OFDM, supporting power efficient and robust filterless multi-color VLC without sacrificing lighting quality.