## 2 Literature Review
### Connected Vehicles (CV)
#### 2.2.2 Expected Benefits and Challenges of CV  
Connected vehicles are practical, up-to-date and synchronized. For instance, according to [PERSON] & Valkama [33], V2X communication has a potential to improve traffic efficiency, road safety, and the availability of infotainment services. Wireless communication technology has been developed in order to make vehicles capable of communicating with road side units (RSU) and with one another in order to solve traffic-related problems, by monitoring traffic in real-time and identifying the best route for the drivers. This can reduce high traffic volumes, numbers of accidents especially in urban areas, and can help drivers find the best route by providing them with on-line traffic data. Such technological advancements would also assist with several applications for road safety (like, lane change warning, collision detection or prevention and cooperative merging), green and smart transportation (for example; intelligent traffic signal controlling and scheduling, better fleet management, etc.). CVs would also offer location dependent services (like, POI and route optimization, etc.) and access to the internet in-vehicle [25]. Furthermore, reliable V2V communication is a key technology to realize the advanced intelligent transport system (AITS) that supports safe driving and enhances automated driving systems [34]. For V2V technology to work seamlessly, each vehicle is assumed to be equipped with an on-board unit (OBU), GPS receiver, a DSRC radio, and enough computing power to track other vehicles [35]. The OBU is responsible for storing the real identity of the vehicle and synchronizing the diversified information [36]. Any helpful information collected from sensors on a vehicle may be sent to neighboring vehicles [37]. It is unquestionable that the number of vehicles on the roads is permanently increasing, especially in urban areas. Since traffic congestions have mostly negative consequences, such as increasing travel time, fuel consumption, and air pollution, vehicle-to-infrastructure (V2I) communication has been developed to mitigate all these problems [38]. V2I communication is able to estimate the traffic density in a certain areas, which represents a key parameter to perform efficient traffic redirection, thereby reducing travel time [39]. Moreover, [PERSON] et al. [40] suggests, a connected network of vehicles and its surroundings enable V2I communication to keep track of the vehicular environment and disburse real-time traffic, road conditions, vehicle density and weather updates, thus improving the overall traffic situation. However, every technology comes at certain cost and so do connected vehicles. While research on connected vehicle networks has progressed remarkably, there are still significant obstacles presented by connected vehicle networks. One such issue is the spectrum scarcity problem [41]. High vehicle speed and high user density, especially in an urban environment, lead to high carrier frequency which leads to frequency error, inter-carrier interference and insufficient channel estimation due to shorter coherence time [42]. The issue of spectrum shortage in wireless communication, the spectrum scarcity and channel overcrowding will apparently pose a difficulty for existing and upcoming vehicular applications [43]. There are numerous other threats highlighted by researchers in the field and one such critical threat is cyber-crime. The communication between devices is achieved with the help of sensors, tags and radio frequency identification (RFID), that put in danger data authentication and integrity. This kind of wireless communication is still vulnerable to cyber-attacks. Improving the security of the IoT technology should be one of the priorities in the further development of this network, as only by achieving top security of data, IoT could be used at its full potential [44]. According to [PERSON] et al.