Color-Selective Channel Modeling For Visible Light Communication (VLC)

Abstract

Color-selective attenuation, a specific case of wavelength- or frequency-selective attenuation, is an under-investigated but significant factor affecting the performance of color-modulated systems, particularly in Non-Line-of-Sight (NLOS) links. Therefore, it must be mitigated to provide reliable links for the Visible Light Communications (VLC) technology. In this sense, this article proposes a novel color-selective channel model, covering multiple time and space (in)variability scenarios for Color-Shift Keying (CSK) modulation. This paper also derives the ergodic capacity of color-selective channels for the high Signal-to-Noise Ratio (SNR) regime. Numerical analysis evaluates the effects of color-selective attenuation on received symbol color, signal space mapping, and channel condition degradation. Additionally, this article evaluates the impact of particular cases of color-selective attenuation – monochromatic, bichromatic, and trichromatic – on 4-CSK systems, comparing them to non-selective attenuation. Simulations also compare the performance of the Color-Hopping Space-Time (CHST) scheme to conventional CSK systems for color-selective channels. Results show that color-selective attenuation causes significant color imbalance and severe performance loss compared to non-selective attenuation, limiting achievable diversity gains and reducing channel capacity. However, the CHST coding scheme mitigates these effects, providing diversity, coding, and channel capacity gains compared to conventional 4-CSK systems.