Constellation design for color space-based modulation in visible light communications

Abstract

In this paper, we present a new strategy to design the constellation symbols in a visible light communication (VLC) system by considering multiple LED transmitters at different wavelengths. For this purpose, the LED transmitters are modeled as fixed points in a color space, and the constellation symbols are obtained by convex combinations of these points. In our formulation, the resulting constellation symbols have to reproduce on average a desired white tonality. Hence, the constellation design strategy is defined as a constrained optimization problem that seeks to maximize the minimum distance among the resulting symbols, but at the same time, to yield a desired white tonality on average. For evaluation purposes, we consider the CIE 1931 color space with 3 and 5 LED transmitters, and constellations with 4, 8 and 16 symbols. Our proposed methodology is compared with a previous work in the state of the art, where an important improvement is achieved with respect to the resulting Euclidean distance among constellation symbols.