A Generalized Three-Dimensional Path Loss Model for Vehicle-to-Vehicle Visible Light Communications

In this paper, we present a novel three-dimensional (3D) path loss model for vehicle-to-vehicle visible light communication (VLC) systems. The proposed model is a function of various system and channel parameters including the longitudinal distance separating the vehicles, horizontal (lateral) shifts, vertical displacement between the headlight and photodetector, angular rotation differences, the spacing of the vehicle's headlights, photodetector aperture diameter, and the weather-dependent extinction coefficient. We validate the proposed path loss model through extensive non-sequential ray tracing simulations and explore how various system and channel parameters influence path loss. Our findings show that while lateral shifts mainly impact path loss at shorter distances, vertical displacement has a substantial effect over both short and long ranges. Moreover, the results indicate that angular rotation significantly affects path loss, especially for angles greater than $5^{\circ }$, which commonly occur during lane changes and turns.