The automotive world is rapidly innovating to achieve full automation in all possible driving scenarios, maneuvers, and situations. It has been established as a fact that wireless connectivity will be required as one of the fundamental technologies in enabling not only full automation but also lower levels of automation. In particular, safety critical applications of self-driving vehicles will heavily rely on wireless connectivity. It is essential to perform safe maneuvers with ultimate (99.999%) reliability in the presence of entities that share the driving space or traffic system. Such entities may include other vehicles, persons, transport systems on the road, or a traffic management network. Hence it is essential to equip every vehicle with wireless connectivity for the purpose of information exchange, cooperation, and coordination with other entities in the system.
For this purpose, the foundations of automotive intelligent transportation systems (ITS) have been laid by the governing bodies in Europe (for example, ETSI). Similar systems have been developed all over the world, in America and Asia Pacific. ITS has defined and specified communication nodes, architecture, protocols, and messages for a diversity of applications and use cases. New infrastructure is required to enhance the DSRC-based applications in unlicensed or dedicated frequency bands. The infrastructure deployment process is already active in many regions under smart highways and smart cities initiatives. In the case of C-V2X, the existing cellular infrastructure is used. Figure 1 shows the interfaces with which an ITS vehicle can communicate with other vehicles or other entities in the transportation system. The following is a description of each interface:
V2V (Vehicle-to-Vehicle) Communications: Initially it was only for broadcast messages, but now vehicles can also perform unicast or multicast messaging. This interface could be used for any information propagation directly from one vehicle to another in the range of communication—for example, in case of emergency braking.
V2P (Vehicle-to-Pedestrian) Communications: Using this interface, vehicles and roadside users could communicate assuming the smartphone has a V2X application. For example, a vulnerable roadside user could be warned of an approaching vehicle.
V2N/V2I (Vehicle-to-Network or Vehicle-to-Infrastructure) Communications: This interface could be used for any information facilitating smart transportation.