Authors:
Keshav Kumar,Mohit Kumar Srivastava,Man Mohan Shukla,Biky Chouhan,Raghav Dwivedi,DOI NO:
https://doi.org/10.26782/jmcms.2026.08.00007Keywords:
Visible Light Communication,Micro-LED,Colour-Shift Keying,Probabilistic Shaping,Human-Centric Lighting,Blue-Light Safety,CIE Colorimetry,Block Successive Upper-Bound Minimization,Flicker Power Spectral Density,and Indoor Optical Wireless.,Abstract
Background: Visible light communication (VLC) based on red-green-blue (RGB) micro-light-emitting diode arrays can support high-speed indoor links while preserving the illumination function of the luminaire. However, the communication waveform may disturb the perceived colour point, the correlated colour temperature, the dimming level and the photobiological safety margin, so lighting quality cannot be treated as an external constraint. Objective: This study proposes a colorimetric-constrained probabilistic amplitude and colour-shift shaping (CC-PAS-CSK) framework for human-centric RGB micro-LED VLC, in which the information rate is maximized jointly with colour stability and blue-light safety. Methods: Unlike conventional colour-shift keying, which assigns symbols uniformly inside the RGB gamut, the proposed scheme selects nonuniform symbol probabilities and drive amplitudes so that the mean chromaticity remains near the target white point. A three-branch optical channel model, a CIE tristimulus transformation, a blue-light weighted exposure model and a filtered photodiode receiver are integrated into a single optimization problem, solved by an alternating colour-rate-safety algorithm. The alternation is formulated as block successive upper-bound minimization, for which monotonic improvement, subsequence convergence to a stationary point and a sufficient uniqueness condition are established. A second-order remainder bound is derived for the linearized chromaticity projection and used to tighten the linearized constraint, so that every iterate is feasible on the exact nonlinear CIE manifold. The temporal power spectral density of the shaped luminous waveform is derived in closed form and imposed as an additional convex constraint. Results: For a 5 m x 5 m indoor room, the proposed design reduces the chromaticity error by more than 50% compared with uniform colour-shift keying and improves the bit-error rate over clipped DCO-OFDM at the same lighting operating point. The algorithm converges within about 20 iterations and, at 20 dB average electrical signal-to-noise ratio, achieves a mean chromaticity error of 0.0019 with a blue-light safety margin of 0.96. Over 45 random initializations and five operating points, the objective is non-decreasing at every iteration, the measured contraction factor stays below 0.47, the first-order projection deviates from the exact projection by less than 0.3% of the colour tolerance, and the percentage modulation at 90 Hz falls from 2.4% to 0.6%, placing the design inside the IEEE 1789 low-risk region. Conclusions: Colour quality should be treated as a physical-layer resource in future VLC systems rather than as an external lighting constraint. Among the compared schemes, CC-PAS-CSK provides the best overall balance of data rate, chromaticity stability and photobiological safety.Refference:
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