# Slicing on the Road: Enabling the Automotive Vertical through 5G Network Softwarization
## 1 Introduction
A slice for eMBB services requires very high data rates to ensure access to multimedia contents, services and data such as ultra-high definition video streaming and augmented reality. A slice supporting mMTC should sustain the traffic load generated by massively connected devices (e.g., sensors enabling smart home and smart building monitoring), typically transmitting a relatively low volume of non-delay-sensitive information. mMTC traffic is mainly concentrated in the Radio Access Network (RAN) segment, thus most of the information flow should not pass through the core network both for security and communication efficiency. Reliability, low-latency and security will be critical for the URLLC slice to provide services that are extremely sensitive to latency such as emergency services and tactile Internet. They would greatly benefit from dedicated functions instantiated at the edge. The need for a dedicated V2X slice has been early argued in [6], and is currently under debate in 3 GPP [4]. Indeed, the unique challenges of the vehicular environment [17] and the peculiarities of V2X services do not easily allow a straightforward mapping into the aforementioned reference slices. The major V2X issues that need to be addressed when designing a network slicing framework supporting the automotive vertical are the following:  
* Localized broadcast communications and edge-dominated access should be considered as crucial slice behaviors to support cooperative driving applications demanding ultra-low latency and ultra-reliable connectivity over the RAN. * Besides safety applications, having as ultimate goal autonomous driving, multiple heterogeneous services with diversified requirements should also be simultaneously supported (e.g., high-bandwidth infotainment services and diagnostics services) pushing for strict slice isolation. * The high mobility of vehicles makes frequent roaming events calling for multi-operator slice coordination. To guarantee a consistent user experience in case of roaming, a basic set of functionalities of a V2X slice that cover the main requirements (e.g., mobility and authorization/authentication) should be agreed among operators and proper interfaces conceived for their interactions. In so doing, slices composed of the same network functions/behaviors could be available for the user when moving to a visited network, while ensuring service continuity. In such a challenging context, this paper aims at providing the following main contributions:
* Design of an architectural framework to support V2X network slicing, aligned with the latest 5G specifications. The framework neatly points out the role and impact of the MEC paradigm and the potential of its interplay with other network softwarization technologies, i.e., SDN and NFV. The behavior is analyzed with special focus on the roaming procedures for a V2X slice supporting the challenging cooperative driving use case. * Experimentally demonstrate the capabilities of a programmable, multi-access, edge-dominated network infrastructure to support V2X slices, through Proof-of-Concept (PoC) experiments based on the Mininet-WiFi [18] wireless SDN emulator. We overhauled Mininet-WiFi to resemble the main components and mechanisms of the conceived network slicing framework. The results of the reproducible experiments point to the viability of the proposal and the potential benefits. The remainder of the manuscript is organized as follows. In Section 2, background material for our work is provided, while scanning the related 3 GPP C-V2X and 5G specifications and the literature on network slicing for V2X. Section 3 provides a general overview of the proposed network slicing framework. Details about the design of a V2X slice for cooperative driving on top of the conceived framework are given in Section 4. Section 5 reports the description of the mobility management procedures in the proposed framework. A reference use case is practically showcased in Section 6, where achieved results are discussed.