An overview of outdoor visible light communications

Abstract

Abstract: In visible light communications (VLC) technology, the outdoor applications are less explored when compared to those indoors. This is due to the fact that: (i) the dual use of light emitting diodes (LEDs) is not always practicable in the outdoor VLC environment; (ii) the level of interference and noise is considerably higher in outdoor VLC; (iii) many other communication technologies are available to be used which, due to their specific characteristics, adapt better to the outdoor environment when compared to VLC technology. Nevertheless, several outdoor VLC applications have been identified. They include and are not limited to building-to-building (B2B), vehicle-to-vehicle (V2V) and road-to-vehicle (R2V) communications. Deploying light fidelity (Li-Fi) using street and park lights is also feasible. Finally, some applications exploit the ability of solar panels to simultaneously harvest the electrical energy and serve as a VLC receiving antenna. The implementation of these communication systems faces lots of challenges. Most of them are related to environmental factors such as fog, rain, sunlight, haze, snow, dust, and atmospheric disturbances. Some challenges are based on parameters such as the geometrical aspect of the light diffusion, which is Lambertian in most cases. These challenges contribute to lower interest in outdoor VLC to date. However, the environment presents several opportunities. In this article, we explore the outdoor VLC environment, review and present some promising applications selected from the literature. Furthermore, we underline likely research opportunities based on the actual state-of-the-art and our outdoor VLC characterisation experiments