Prospects of Differential Optical Receiver With Ambient Light Compensation in Vehicular Visible Light Communication Mohammad Rakibul Alam and Saleh Faruque Department of Electrical Engineering University of North Dakota, Grand Forks, ND 58202-7165 mohammadrakibul.alam@und.edu, saleh.faruque@engr.und.edu Abstract—Since the number of vehicles has been increasing and adding more complexity to the transportation infrastructure every day, safety and efficiency in transportation system are of utmost importance. Effective communication between vehicles and with traffic infrastructures (e.g. traffic signs, traffic lights, etc.) play a key role to ensure a safe and secure traffic system. Visible Light Communication being a very promising technology, can be an ideal solution to address the challenges in vehicle-to-vehicle (V2V) and vehicle-to- infrastructure (V2I) communication. A fundamental challenge in this regard is the design of a proper sensor to minimize the interference of the ambient light in daytime. Optical filters can be used to minimize the problem, but additional techniques are required to further optimization. In this paper, we discuss the prospect of using a differential optical receiver in vehicular VLC communication, which can cancel ambient light and other atmospheric noises. Keywords—visible light communication (VLC); vehicle to vehicle (V2V) communication; differential receiver; ambient noise I. INTRODUCTION Due to rapid urbanization, the number of vehicles has been increasing in a rate faster than ever. Need for a new transportation system to face critical traffic problems such as accidents and traffic congestion is more vital than ever [1]. A communication based vehicle system can offer next generation safety and security. For that regard, vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications are used in order to form a Vehicle Ad-hoc Network (VANET). Vehicles can talk with each other using optical signals and share traffic data (e.g. acceleration, velocity, position, electrical/ mechanical state, etc.), which vastly increases traffic safety [8]. In busy urban areas, traffic infrastructures (e.g. traffic signs, traffic lights, etc.) can also communicate with vehicles if it becomes a part of the optical network. VLC is a promising wireless communication technology where data is sent by modulating the data onto the instantaneous power of light [12]. It maintains a rate which is faster than human eye can detect and maintains the functionality of the light. The low cost and rapid adaptability of LED lights in road infrastructures and vehicle lighting systems are in favor for accepting VLC in transportation system. Vehicles can communicate with each other using their front and rear lights and share their status (e.g. velocity, acceleration, position, etc.). Even though VLC in vehicles saw a promising start [2], due to several challenges, it did not appear practical in nature. The main reason VLC stayed as a viable solution for vehicle safety until now is that it is capable of delivering very large number packet with very low latency. It is also immune to multipath effects, mutual interference and Doppler effect [3]. As of today, the applications for VLC are largely based on indoor usage and the vehicular applications are mostly theoretical rather than experimental. In this article, we address the issues concerning the design of an optimized VLC receiver and a review of existing receiver technologies. We focus our discussion on optical receivers which are mainly build for vehicular applications. The differential receiver design which we propose offers solution to some of the vital challenges in daytime optical communication. II. DIFFERENT TYPES OF VLC RECEIVERS The optical receivers which are used now-a-days have either a camera or an array of photodiodes. Each system has its own advantages and disadvantages. A. Camera-Based Receivers Most of the new generation cars have camera fitted in them, which can detect pedestrians, cars on side lanes and other roadside objects. Generally they have a large field of view (FOV), which is their biggest advantage. They can also minimize optical noises and detect optical signals from a long distance. Because most of the cameras fitted in the cars are low- cost cameras, they offer low frame rates and can communicate in limited distances [13]. Although fitting cars with high-speed camera is possible and they will generate high frame rates, they are very expensive and not practical for wide distribution. This option is only practical for laboratory testing.