upremacy has been undermined by the rising role of 3GPP and cellular networks. Starting with the support of telematics and infotainment services for connected cars, cellular networks are now noticeably involved at a much wider scope. The Cellular V2X (C-V2X) technology is part of the completed 3GPP Long-Term Evo- lution (LTE) Releases 14 and 15. It is intended to support ultrahigh reliable and ultralow 13 5G Network Slicing for V2X Communications: Technologies and Enablers latency V2X applications in the 5G Release 16 (e.g. autonomous driving, car platooning), with specifications to be frozen by the first half of 2020. C-V2X is meant to be a unified technology that will allow vehicles to communicate with other vehicles, pedestrians, infras- tructure nodes, and remote servers, to guarantee full coverage and service continuity. In 3GPP documents (3GPP TR 22.185, 2018) V2X communication types are classified as follows: (i) vehicle-to-vehicle (V2V) for direct communications between vehicular user equipments (VUEs) in close proximity; (ii) vehicle-to-infrastructure (V2I) for communica- tions between vehicles and the RSU in radio range, which can be implemented either in an eNodeB or in a standalone device (e.g. a traffic light); (iii) vehicle-to-pedestrian (V2P) between vehicles and VRUs (e.g. pedestrians, bikers); and (iv) vehicle-to-network (V2N) for communications with remote servers and cloud-based services reachable through the cellular infrastructure. 13.3.1 The C-V2X Technology C-V2X spans both the PC5 and LTE-Uu radio interfaces as well as core network (CN) func- tionalities, as discussed in the following. 13.3.1.1 The PC5 Radio Interface V2V, V2P, and V2I communications occur over the PC5 radio interface (sidelink) and bypass the cellular infrastructure. The 5.9 GHz band is used, independently or even in the absence of a cellular network, in order to ensure ultrahigh availability under all geographies, regard- less of the specific mobile network operator (MNO). 3GPP efforts resulted in the specifica- tions (3