# A Review-Unguided Optical Communications: Developments, Technology Evolution, and Challenges
## 5 Advancements in Optical Wireless Communications
### Vehicular Visible Light Communication (V\({}^{2}\)Lc)  
Driverless vehicles, having several built-in sensors such as ultrasonic transducers, cameras, lasers, LEDs, lidars and radars, etc., are emerging nowadays. VLC can also be integrated in such vehicles and this is known as vehicular VLC (V\({}^{2}\)LC). There is a rapid increment every day in the number of vehicles being used for transportation; thus, traffic and the number of accidents/victims are also increasing, relatively. Most of the automotive industries, government agencies, and the scientific community work together to improve driving safety, automatic control, inter/intra vehicle communication, traffic information sharing, early warning and accident prevention, etc. Therefore, the efficiency and safety of the transportation system will increase when exchanging data, in real-time, between vehicles and traffic network infrastructures [301]. V\({}^{2}\)LC also refers to communication between vehicle and persons/pedestrians, vehicles and devices, vehicles and grids, vehicles and traffic signals, vehicles and homes, vehicles and traffic infrastructure networks, and between vehicles [302]. Figure 35a shows the possibility of using V\({}^{2}\)LC for different scenarios. Vehicular networking is required to exchange safety messages, reduce crashes between vehicles, and prevent accidents on the road. Accident prevention is one of the most important requirements since it is related to life saving, reducing family, eyewitness, and rescuer trauma, emergency callouts, vehicle repair costs, medical costs, and associated traffic congestions. Vehicle networking allows each vehicle to inform all surrounding vehicles of its location, distance, and other parameters. Networked vehicles can estimate the trajectories of all nearby vehicles and thus can avoid crashes [303]. Vehicles may also warn each other of dangers such as falling trees, ice, vehicles broken down, traffic congestion, etc. With the emergence of V\({}^{2}\)LC and vehicular ad-hoc networks (VANETs), its realization becomes a reality [304; 305]. All vehicles will have these features to function in the most secure and reliable manner possible. The transport vehicle industry/manufacturers are slowly introducing these solutions in the vehicles. As shown in Figure 35a, V\({}^{2}\)C is a vehicle-to-vehicle communication method for exchanging information between nearby vehicles. VPC is a vehicle-to-pedestrian communication system which is particularly useful for school children, and physically disabled and elderly people. To prevent collisions, VPC establishes a connection between vehicles and the smart devices of pedestrians. VDC is a vehicle-to-device communication system that connects automobiles to a wide range of external receiving devices, and it will be especially useful for bikes. Vehicles can communicate with the bike with the VDC application software installed on their mobile or on the bike to warn the driver about the possible hazard to prevent accidents. A vehicle health check (VHC) requires the connection of a vehicle with the home of its driver/owner, sharing the condition of the engine, energy supply, and fuel requirements. A vehicle information center (VIC) establishes a link between vehicles and traffic infrastructure to obtain traffic-related information and dynamically shows a route map to reach one's destination with the optimal distance and efficiency. VGC stands for vehicle-to-grid communication, which allows the car's charging rate to be adjusted by communicating with the power grid. This will be a standard feature on some electric vehicles, and it will be used as a power grid modulator to react to changing electricity demand dynamically [306]. V\({}^{2}\)LC systems are less complicated and more highly secured than RF systems, provide LoS communication with a better FoV, and the cost associated with the implementation of V\({}^{2}\)LC systems is relatively low.