# Enhancing Route Guidance with Integrated V2X Communication and Transportation Systems: A Review
## 4 V2X Communication Architecture  
Recent advancements in communication technologies are transforming the transportation industry, presenting new opportunities to enhance safety, efficiency, and sustainability in ways that were once beyond imagination. Autonomous vehicles, for instance, has been increasing in number in the last few years. It has become an integral part of self-driving cars and the future of smart cities [79], as well as cooperative communication systems, which are one of the fundamental components of an intelligent transportation system. \"Cooperative\" indicates that wireless networks are used to communicate and cooperate between moving objects and the supporting infrastructure. Cooperative communication supports the use of vehicle-to-everything (V2X), which provides vehicle links with various recipients. V2X is a new generation of information and communication of a vehicle to units such as other vehicles and roadside units (RSUs) [80]. According to the CAR2 CAR Communication Consortium, V2X communication can offer various services such as safety alerts, enhanced route guidance and navigation, green-light optimal speed guidance, V2V merging assistance, Internet access, and remote vehicle diagnostics [81]. It improves the transportation environment's efficiency and reduces pollution and accident rates by improving traffic flow and reducing congestion. This can be achieved through real-time data sharing between vehicles and infrastructure, enabling drivers to avoid congested routes and reducing the amount of time spent idling in traffic. To grant reliable and autonomous operation of a road network, it is essential to implement a reliable V2X communication system. V2X communication encompasses four primary components: vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-pedestrian (V2P), and vehicle-to-network (V2N) communication. V2V is vehicle-to-vehicle communication on the road that aims to reduce travel time, avoid collisions, and support autonomous driving [82]. V2I is vehicle-to-infrastructure communications to exchange data between vehicles and road infrastructure. V2I aims for collision avoidance, traffic control, and congestion avoidance. V2P is vehicle-to-pedestrians communication, which helps avoid accidents. V2N, vehicle-to-network communication, is between vehicles, networks, servers, or data centers. V2X communication enables vehicles to connect to an onboard unit (OBU) or any wireless-enabled device [83]. In V2X communication, moving vehicles interact with their surrounding using processors and transceivers known as roadside units (RSUs). The processing unit processes the data, sends it with the transceiver, and shares the data between vehicles and RSUs. Thus, accidents can be avoided, and the optimal path can be calculated. The four V2X applications--Vehicle-to-Vehicle (V2V), Vehicle-to-Network (V2N), Vehicle-to-Pedestrian (V2P), and Vehicle-to-Infrastructure (V2I)--utilize \"cooperative awareness\" to offer sophisticated services. These improvements include better collision warnings and enhanced autonomous driving features. Vehicles, roadside infrastructure, application servers, and pedestrians can all gather information about their local environment and share details about their surroundings with other vehicles and infrastructure. It involves the use of communication protocols and systems that enable real-time exchange of information between vehicles and infrastructure. This information can include data on traffic conditions, road hazards, weather conditions, and other factors that affect driving conditions. By sharing this information between vehicles and infrastructure, drivers can make well-informed decisions and take appropriate actions to avoid accidents and improve traffic flow. This, in turn, enables intelligent transportation services, including route guidance. Each identified use case type outlines a specific subset of operations required for a cooperative vehicle as follows.