Abstract
Visible light communication (VLC) systems often rely on uniformly distributed constellations, which can lead to suboptimal performance and a reduction in spectral efficiency (SE). To address this limitation, we propose a novel spectrally efficient modulation scheme that leverages probabilistic shaping (PS) to enhance the SE of VLC systems. The proposed scheme is based on the color-shift keying (CSK) modulation format for a quadrichromatic LED (QLED)-based system. We derive both the capacity and transmission rate (TR) for the proposed scheme, and adapt the TR based on the optical signal-to-noise ratio (OSNR) by optimizing the distribution of constellation symbols and forward error correction (FEC) coding rate, thus ensuring optimal system performance under varying channel conditions. Furthermore, we introduce an algorithm to compute the optimal capacity-approaching input distribution. To validate the proposed scheme, a QLED CSK system prototype was developed and experimentally tested. We evaluated the performance of the proposed scheme in terms of SE and frame error rate (FER) under different OSNR levels, and compare it against the conventional uniform-based scheme. The results demonstrated that the proposed scheme achieves a 20% improvement in SE over the uniform-based scheme.