## 1 Introduction  
Visible Light Communications (VLC) represent a new wireless communication technology which transforms a basic LED lighting device into an intelligent dual purpose tool used for lighting and communications simultaneously [1, 2, 3, 4]. VLC is based on the solid-state lighting devices' fast switching ability, which enables them to be used in communication purposes as well. So, in VLC, the communication feature is achieved by modulating the data onto the instantaneous power of the optical carrier at rates that are imperceptible for the human eye [5]. The data communication is thus achieved without perturbing in any way the primary function of the lighting device and without using any extra power to generate the carrier wave. In these conditions, the VLC technology is favored by the wide distribution of light sources. Due to the incontestable competitive advantages, existing research forecast that LED lighting sources are on the way to totally replacing classical lighting devices [6, 7, 8]. Consequently, from a hardware point of view, the VLC technology can be viewed as half implemented worldwide, since a data processing unit and a digital power switch are all that an LED illumination source needs in order to be transformed into a data broadcasting device for indoor and outdoor applications. Regarding the usage of VLC technology in automotive applications, this domain is favored by the integration of the LED light sources as part of the traffic infrastructure (i.e., traffic lights, street lighting system, traffic signs, traffic panels) and also within vehicle lighting systems [2; 9]. This fact is very important because the performance and efficiency of an intelligent transportation system based on wireless communications are given by the technology's geographical distribution and penetration rate [10]. From this point of view, VLC is able to provide a low-cost solution for fast deployment and wide area distribution. Thus, the VLC technology could be used to enable both traffic Infrastructure-to-Vehicle (IZV) and Vehicle-to-Vehicle (V2V) communications [11; 12; 13; 14; 15]. Nevertheless, supporting vehicular communications is rather challenging due to the strict requirements (i.e., latencies below 20 ms and high packet delivery ratio) [2; 5]. Major challenges are related to the noisy outdoor VLC channel [16; 17; 15] and the characteristics of vehicular communications [2]. In the outdoor scenario, the light incident on the VLC sensor contains not only the data optical signal, but also other strong sources of natural and artificial light [17]. Thus, in the worst-case scenario, when the sun is directly facing the VLC sensor, the irradiance of the incident sunlight can reach a very high level which strongly affects the packet delivery ratio. Although influence of the parasitic light can be reduced using different solutions [2; 18; 19; 20; 21; 22], a proportional shot noise component is still introduced in the system. Consequently, in daytime conditions, the background light represents the most important perturbing element for VLC usage in vehicular applications, especially when medium range communications are envisioned. Vehicular VLC applications require communication ranges up to few tens of meters or even more, [2], whereas the irradiance of the received data signal decrease proportionally to the square of the distance. In such circumstances, the irradiance of the received light can decrease at nW/cm\({}^{2}\) levels. Furthermore, unlike in other technologies, the emitted power cannot be increased as much as necessary because it is strictly dependent on the VLC emitter's primary purpose [5]. Thus, a data broadcasting LED traffic light or a vehicle LED tail lamp should have the same optical power as they were initially designed and limited by automotive lighting standards, even though they had been enhanced with data transmitting capabilities. In this context, automotive VLC systems should be able to provide highly resilient communications under very low Signal to Noise Ratio (SNR) conditions.