## 1 Introduction
The wide distribution facilitates the usage of the visible light communications (VLC) technology. Within this context, this article presents a new VLC communication system that is designed for communication-based vehicle safety applications. The proposed design is an enhanced version of VLC system that is able to achieve performances that further demonstrate the viability of VLC-based solutions in automotive applications. The transimpedance circuit is one of the most important elements of a VLC receiver, as it determines the resilience to optical noise sources. In almost every case, VLC systems use the linear transimpedance circuit. Nevertheless, it has been demonstrated that a logarithmic transimpedence circuit provides improved resilience to optical noise and an extended working range [31]. However, other factors must also be addressed in order to be fully compatible to automotive VLC systems. Thus, this article presents an enhanced VLC design by providing a VLC receiver solution capable to adapt the communication parameters to the specific context. Thus, unlike in [22; 31], this new design is able to communicate while using different modulation techniques, coding techniques, and data rates (3-50 kb/s). Additionally, the novelty of this article comes from a more realistic approach on addressing the design of automotive VLC systems. In most of the existing works, custom made VLC emitters are used to demonstrate the potential of the technology [21; 32], although they do not comply with the lighting requirements. Thus, in the real-world scenario, comparable results are rather difficult to be reproduced. Regarding the VLC sensors, most of the existing works report performances achieved under narrow field of view (FOV) conditions [16; 32; 33]. Although a narrow FOV VLC sensor is fully justified, as this approach significantly reduces the amount of parasitic light incident on the photosensitive element, the mobility of the system is reduced (especially in short range conditions). As the vehicular environment is defined as highly dynamic, such VLC systems are less compliant to the mobility requirements [17]. The proposed VLC emitter is developed using a standard compliant LED traffic light to address these issues. Thus, the results achieved by the system are like the ones obtained after the implementation of the concept in a real intersection and not overestimated by an increase of the emitted power. Furthermore, a wide angle FOV sensor has been used to enhance the system's mobility and to maximize the compatibility with automotive applications instead of using a narrow angle VLC sensor to minimize the effect of parasitic light. Of course, these two approaches significantly decrease the signal to noise ratio (SNR) and complicate the data reconstructing process. The proposed system was tested under different working scenarios. The experimental testing has confirmed the system's performances, its ability to work under noisy conditions, and its capacity to achieve communications distances up to 50 m. Thus, the proposed design represents a simple, low-cost, and easy to implement solution for a safer road network. Another aspect that is addressed in this article is related to the modulation and coding techniques that are suitable in vehicular VLC applications. Hence, this work investigates the performances of a spread spectrum based modulation suitable for poor SNR scenarios or for high priority data, the performances of a classical modulation and coding technique suitable for general purpose applications/scenarios, and the performances of a third coding technique that could be more appropriate in multiple input multiple output (MIMO) applications in order to path the way toward context adaptive VLC systems [17; 34]. All of these techniques are investigated through intensive experimental evaluation performed in laboratory conditions and in outdoor uncontrolled conditions.