This paper investigates the bit-error probability of several color shift keying (CSK) constellations in a visible light communications (VLC) scenario with a camera-based receiver. A novel VLC communication constellation set, the extended circular CSK, is presented and analyzed. Its performance is compared to the CSK constellation described in the IEEE 802.15.7 standard, in addition to other constellations that were introduced previously, namely the geometric and circular CSK constellations. The bit-error rate (BER) of the proposed extended circular CSK constellation is studied. Simulation results show that the extended circular CSK significantly outperforms the other constellations and deserves further research attention in the future.

This paper introduces circular color shift keying (CSK) constellations in a visible light communications (VLC) system using a camera-based receiver with applications to vehicular communications, where vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications are required to improve the safety of vehicles in high traffic density. The circular CSK constellations are shown to outperform the geometric and IEEE 802.15.7 constellations in terms of bit-error probability. Afterward, the noise at the receiver is investigated and transferred from the spatial domain to an angular noise in the International Commission on Illumination (CIE) color domain, where it is shown to behave similarly to a Gaussian distribution. Based on this noise model, a closed-form expression of the bit-error rate (BER) of circular CSK constellations is derived and shown to be accurate for BER ranges corresponding to VLC applications of practical interest. Diversity techniques are also investigated, and interesting differences are noted during the analysis compared to traditional radio frequency (RF) communication scenarios. Finally, the design of a link adaptation approach maximizing the number of bits per transmitted symbol, while meeting a target BER, is proposed. Hence, this paper presents a detailed design and analysis of a novel VLC modulation technique and demonstrates its efficiency and superiority.