# Slicing on the Road: Enabling the Automotive Vertical through 5G Network Softwarization
## 2 Background, Motivation, and Contributions  
### From Cellular-V2X to the 5G Service-Based Architecture  
3 GPP is pushing the C-V2X technology as a solution enabling vehicles to communicate with everything, i.e., other vehicles (V2V), vulnerable road users (vehicle-to-pedestrian, V2P), roadside infrastructure (vehicle-to-infrastructure, V2I), and the cloud/edge servers (vehicle-to-network, V2N). The technology uses the cellular network infrastructure to provide service to vehicular user equipments (VUEs) and enable enhanced direct V2V connectivity (be it network-assisted or unassisted) through the PC5 sidelink interface [19; 20]. The following entities have been added to extend the cellular architecture in Release 14 [21] and to specifically manage V2X communications:  
* The V2X Control Function is the logical function for V2X network-related actions. It provides configuration parameters for VUEs located under the coverage of an eNodeB as well as out-of-coverage, i.e., without the cellular infrastructure service. * The V2X Application Server (AS) has a wide range of functionalities including: the reception of uplink unicast data from the VUEs; the delivery of data to the VUEs in a target area using unicast and/or multicast interfaces. It may also provide centralized control and distribution of traffic, road, and service information. The C-V2X standard is still evolving and it is expected to embrace upcoming 5G specifications to support more advanced driving assistance services. The latter ones are classified by 3 GPP in four categories [22]. Vehicles platooning, which dynamically forms a group of vehicles travelling together at short inter-vehicle distances. Advanced driving, which we call here cooperative driving, enables vehicles to share local sensor data and driving intentions with vehicles in proximity, thus coordinating trajectories and maneuvers. Extended sensors services, which foresee the exchange of raw/processed sensor data or live video among VUEs, RSUs, pedestrians and V2X ASs. Remote driving, which allows a remote driver or a cloud application to tele-operate a (private or public) vehicle; this is useful for those passengers who cannot drive themselves or when the vehicle is located in dangerous or uncomfortable environments. The 5G architecture, recently specified by 3 GPP [23], is natively conceived with softwarization in mind. The Core Network (CN) consists of various NFs, with a clear separation of CP functions and UP functions (UPF), as depicted in Figure 1. The Access and Mobility Management Function (AMF) provides UE-based authentication, authorization, mobility management, etc. The Authentication Server Function (AUSF) stores data for authentication of UEs, while the Unified Data Management (UDM) stores UEs subscription data. The Session Management Function (SMF) is responsible for session management and also selects and controls the UPF for data transfer. The Policy Control Function (PCF) may instruct different routing policies. To specifically address the cloud-native design and the paradigm shift from a network of entities to a network of functions, the following functionalities have been designed. The Network Repository Function (NRF) provides registration and discovery functionality, allowing NFs to discover each other and communicate via open Application Programming Interfaces (APIs), in contrast with LTE that uses predefined interfaces between the elements. For instance, the AMF service exposes to other NFs the information regarding mobility-related events and relevant statistics [24]. The Network Exposure Function (NEF) provides the means to collect, store and securely expose the services and capabilities provided by 3 GPP network functions (e.g., to third parties or amongst NFs themselves). The Application Function (AF) represents any additional CP functions which might be required, e.g., to implement network slicing. 3 GPP is investigating in [4], as part of Release 16, potential architecture enhancements of the 5G system design to support advanced V2X services.