In the context of an increasing number of road fatalities, enhancing the safety and the efficiency of the transportation system represents a crucial challenge for governmental agencies, the automotive industry and the scientific community. One of the most promising solutions in this area are the communication-based vehicle safety applications, which can address up to 81% of the crashes [1]. This concept envisions that intelligent vehicles equipped with state of the art sensors and wireless communication technologies are able to exchange relevant safety data (i.e. location, velocity, acceleration, etc.) in order to cooperate toward traffic accidents prevention. Furthermore, the vehicles are also exchanging information with the transportation infrastructure. Visible Light Communications (VLC) are an emerging wireless data transfer technology in which the data is modulated onto the instantaneous power of the LED produced light (380-780 nm). Thus, a first advantage of VLC is that the data transfer is achieved as an additional function, besides lighting or signalling with limited power consumption, whereas in the context of limited spectrum availability, it provides world-wide unlicensed and almost unlimited bandwidth (400 THz). Due to their energy efficiency, reliability and decreasing fabrication costs, LED lighting systems are on the way of replacing classical public street lighting, traffic lights, traffic signs and in vehicle lighting systems [2], and consequently, provide the foundation for using the VLC technology for various smart cities applications, including the intelligent transportation system (ITS). Thus, the omnipresent character, the high performance to cost ratio, and huge bandwidth available make VLC a promising wireless communication technology for the automotive applications [3-16], especially in high vehicle density scenarios [9].

The Project Director has been involved in early developments of Visible Light Communication systems in important industry – university collaborative projects such as $18.5 million NSF ERC Smart Lighting Systems (as associate professor at Howard University) or $6.8 million Co-Pilot for an intelligent road and vehicular communication system (as invited professor at University of Versailles St. Quentin, grant which also funded the PhD research of a post-doctoral researcher from the team). These experiences and expertise, along the expressed interest of Romanian branch of General Electric in this research direction have generated the initiative to develop this proposal for the implementation of the innovative concepts that were presented by our team in two subsequent articles published last month in the IEEE Sensors Journal [6,7].

In the upper-mentioned context, this project aims at developing, implementing and testing a high-performance VLC system suited for automotive safety applications. The envisioned system englobes intelligent VLC emitters and receivers capable of adapting to various environmental conditions. The VLC emitters will be developed based on elements that are already part of the road transportation system (traffic lights, street lights or vehicle lights) and will enhance their data transmission capabilities. The VLC receivers will be developed by taking into consideration their future integration on commercial vehicles (e.g. low cost, EMC compatible). In addition to the novelty of the automotive VLC area itself [4-8], the originality of the proposed development comes from the innovative concept of environment-adaptive automotive VLC system. As we have theoretically demonstrated in publication [7], the overall performances of a VLC system could be significantly enhanced by developing a system able to evaluate the environment perturbing factors and to self-adjust its settings in order to maximize the efficiency for that given context.

As the automotive (outdoor) VLC channel is very unpredictable, highly dynamic and extremely noisy, a central problem in the area of VLC automotive applications is the design of a suitable VLC system able to face these problems (for example, strong sunlight can saturate the photosensitive element). Therefore, the VLC receiver should be able to enhance the low-power signal and to avoid disturbances due to the environmental conditions, in order to ensure a robust communication. As one can have no control over the external conditions, the existing VLC systems are designed in order to face the worst possible scenario and still support communication [8-9]. Nevertheless, it is obvious that under normal conditions, this method limits the system performances. For example, the receiver we described in [15], was designed in order to be able to support communication without saturating even in case of direct sun exposure (up to 100 000 lux). However, the experimental verification has revealed that the limited gain of the pre-amplification stage leads to a significant decrease in communication distances, no matter the power of the parasitic light. In a next step of the Co-Drive project, funded by automotive company VALEO (France), we narrowed the receiver’s Field Of View (FOV) to ± 10°, limiting the amount of parasitic light incident on the photosensitive element. Therefore the influence of sunlight was reduced and a longer communication distance has been experimentally achieved [8]. Although the system had remarkable results, the narrow FOV negatively affected the mobility limiting its applicability. Thus, it can be observed that in order to counteract a particular situation, such as the one in which the sun is directly facing the VLC receiver, the sensor qualities are deteriorated for all the other possible situations. Other research groups decided to enhance the resilience to noise with the help of a robust modulation technique based on Direct Sequence Spread Spectrum (DSSS) using sequence inverse keying. Although the resilience to noise is greatly enhanced, the modulation’s large bandwidth requirement decreases the data rate by 10 times [16]. Even if the enumeration can continue, we provided three examples that show how the VLC system performances are strongly affected by a drastic response to a specific problem caused by the environment conditions. It is obvious that the response to mitigate the parasitic sunlight affected in turn the communication distance, the mobility, and the data rate. In a similar way, a strong response to mitigate other particular negative situations further limits the overall system performances. The solution we propose has the potential to change the paradigm regarding the development of automotive VLC systems, opening new opportunities in this area.

In order to achieve the scope of the project, 5 specific objectives were established:

The first objective is to fully demonstrate the viability and the benefits that could be provided with the usage of environment-adaptive VLC system in automotive applications and to identify the benefits that could be delivered by each adaptive function (analytically and by simulations).

The second objective is to develop and implement an enhanced VLC emitter, able to evaluate the external conditions and the specific requirements, and auto-adapt its broadcasting parameters in order to maximize the communication performances, while still maintaining a robust link.

The third objective is to develop and implement an environment-adaptive VLC receiver, capable of self-adapting to the changing outdoor conditions. The receiver will be able to receive, identify and properly decode messages transmitted using different configurations and in diverse environments. The forth objective towards the development of the autoVLC system consists in its testing, optimization and experimental validation. This step will allow us to provide a general perspective on the system performances to make further enhancements.

The fifth objective of the project is to improve the research capability at the host institution and provide interested regional companies with adequate solutions of the above-mentioned problems, to develop human resources for advanced research and to gain international visibility for our research.

The feasibility of the project is guaranteed by the team extensive experience and expertise in the field of VLC automotive applications or related proposed areas, by the fact that we were part on another VLC project that has ended with an experimental demonstration of one of the best existing VLC systems [8], and by international recognition of our fundamental concepts, as reflected by the recent publications in the prestigious IEEE Sensors Journal [6-7]. Thus, their performances have been partially confirmed analytically and by simulations - Technology Readiness Level 2 (TRL2). At the end of this research project we are expecting to have a functional autoVLC system, able to evaluate the environment conditions and to optimally auto-adjust its settings in order to maximize its performances. This system will be tested and validated in laboratory conditions (TRL4). Reliability and robustness to noise will be the main priorities in developing the system, rather than data rate. Also, at this stage, it is more important for us to demonstrate the auto-adaptive character instead of establishing a record in communication distance.

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