Performance Characterization of Vehicular Visible Light Communication in the Presence of Sunlight

Vehicular visible light communication (VLC) has emerged as a promising alternative to radio-based vehicular communication and aims to utilize the widely available light emitting diode (LED) based vehicle exterior lighting for dual-purpose illumination and data transmission. While VLC has thrived in indoor environments and has already been commercialized, its adoption in outdoor settings faces unique challenges. In particular, solar irradiance significantly impacts the performance of vehicular VLC systems and exhibits its effect by increasing background noise and elevating the direct current (DC) level in the photodetector output. In this paper, we conduct a comprehensive performance characterization of vehicular VLC in the presence of sunlight. We utilize the empirical ASHRAE clear-sky solar irradiation model to estimate background noise, incorporating geographical, temporal, and vehicular mobility factors to account for changing sunlight conditions. We derive a closed-form expression for signal-to-noise ratio (SNR) as a function of solar irradiance, receiver parameters (e.g. aperture diameter, responsivity, and bandwidth), and vehicular positions relative to each other. We conduct an experimental study in outdoor vehicular environments to validate the theoretical models, demonstrating their practical applicability under varying sunlight conditions.