# Slicing on the Road: Enabling the Automotive Vertical through 5G Network Softwarization
## 1 Introduction  
The automotive vertical market is undergoing key technological transformations. Thanks to advancements in automation, sensing, and positioning techniques, self-driving vehicles are no longer science fiction but they are set to become a reality. Merging the local perception provided by on-board sensors, e.g., Global Positioning System (GPS), Light Detection and Ranging (LIDAR), Radio Detection and Ranging (RADAR), and cameras, of automated vehicles with information provided by other vehicles' sensors and by the roadside infrastructure (e.g., about obstacles, road surface conditions, and planned maneuvers) will improve the perception of the surroundings and the overall vehicle safety. This is known as cooperative driving and includes both cooperative sensing and cooperative manoeuvring services, raising challenging demands in terms of coverage and connectivity in order to guarantee ultra-low latency (below 10 ms), ultra-high reliability (near 100%) and high data rate (in the order of Gbps) under high mobility and density conditions. Such strict demands cannot be met by current technologies, neither the IEEE 802.11 variants nor the Long Term Evolution (LTE); this is why the research and industrial communities have struggled to come out with the specifications of a new technology, which has a clear and forward compatible evolution path towards the fifth generation (5G) system. Efforts toward this direction are being promoted by key players in the automotive and telecommunications industries within the 5G Automotive Association (5 GAA) initiative [1]. The Third Generation Partnership Project (3 GPP) specified a set of technical enablers in Releases14 and 15 to provide a spectral-efficient air interface, with a focus on localized vehicle-to-vehicle (V2V) communications. The new technology, called Cellular V2X (C-V2X), targets advanced driving assistance services, such as cooperative driving [2] and platooning [3]. Such results alone cannot fully address the challenges of the V2X ecosystem. The entire end-to-end chain of radio, networks, applications and (cloud) services of upcoming 5G systems requires customization and architecture enhancements to meet the highly demanding V2X performance requirements, currently under debate within 3 GPP Release 16 [4]. For this reason, _network slicing_ has been recognized by the standardization bodies and the research community as a prominent solution to fulfill the stringent V2X requirements [4; 5; 6]. By logically isolating control plane (CP) and user plane (UP) network functions (NFs), network slicing [7] can tailor resources to specific vertical markets' needs on a common programmable network infrastructure. This is viable through network softwarization technologies [8] such as Network Function Virtualization (NFV) [9] and Software-defined Networking (SDN) [10], and through Multi-access Edge Computing (MEC) principles [11]. Thanks to NFV, UP and CP functionalities of different slices can be virtualized, independently scaled and displaced in convenient locations to flexibly support various services. For instance, UP functions can be located close to the user, in edge cloud facilities, by exploiting MEC deployments [12] to reduce service access latency. Edge nodes can also be exploited by verticals and over-the-top providers for storage, processing and dynamic service creation within a given network slice, thus introducing another multi-tenancy dimension [13]. SDN allows the remote configuration of the physical network to reserve on demand networking resources for the slices and to steer network traffic accordingly [14]. A set of references slices are typically considered, where each of them represents categories of use cases identified by the International Telecommunication Union (ITU) [15] and by the Fifth Generation Public-Private Partnership (5G-PPP) [16], i.e, enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and critical communications (CriC), also known as ultra-reliable and ultra-low latency communications (URLLC).