Enhanced Filterless Multi-Color VLC via QCT

Color shift keying (CSK) in visible light communication (VLC) often suffers from filter-induced crosstalk and reduced brightness. This paper proposes using quartered composite transform (QCT) with multi-color light-emitting diodes (LEDs) to improve both illumination and communication. The proposd DC-biased QCT scheme eliminates receiver optical filters, thereby removing crosstalk and significantly increasing signal-to-noise ratio (SNR). Simulations demonstrate QCT maintains high illumination quality (CRI 79.72, CCT 3462 K) while achieving over double the average illuminance compared to CSK under the same power budget. QCT also shows better bit error rate (BER) performance in low-to-moderate SNR regimes and has ability to convert multi-tap frequency-selective channel into an equivalent single-tap flat-fading channel to mitigate inter-symbol interference (ISI), proving a promising technique for brighter, high-performance, filter-less VLC.