# A Virtualization Infrastructure Cost Model for 5G Network Slice Provisioning in a Smart Factory
## 2 Background
### Industrial Requirements for Network Slicing  
Compared to previous generations, 5G provides higher data rates, better reliability, lower latencies, and support for massive connectivity. Industry verticals such as manufacturing, automotive, healthcare, public safety, and energy consist of many potential slice customers. A smart factory includes multiple device types with use-case-dependent technical and architectural requirements [25, 26]. For example, an augmented reality device requires high data rates and low latencies, while a traditional broadband device does not have strict requirements for latency. Similarly, a logistics monitoring device requires low data rates and does not have strict latency requirements; however, the network should be able to support connectivity for a massive number of such devices. Furthermore, a V2X device requires low latencies, and the network should be able to support a varying density of devices depending on the amount of vehicular traffic. Moreover, the number of connected devices has been increasing with the increase in the level of automation. The different device types for different use cases can be provisioned with required slices and managed accordingly over local and wide area networks [27]. The edge cloud must be scalable for reliable service provisioning, and ad hoc networks can be deployed depending on the latency constraints [28, 29]. Deploying the virtualized core network functions locally can significantly reduce the latencies; however, depending on the use cases, it is possible to deploy resources up to a maximum geographic distance if it still satisfies the latency requirements, as studied for the augmented reality use case in [30]. Thus, it is possible to deploy the VNFs in a central, distributed, or local cloud, given that the latency requirements can be satisfied.  
The reliability and availability of the network are crucial to ensure uninterrupted factory operations. Reliability in communications can be defined in terms of the maximum amount of allowed packet loss in a given time, and availability as the time the connectivity service should be available to the devices [25]. Regarding the smart factory under study, the costs of the communication network make up a very small portion of the overall factory expenses, and the communication network must be reliable as well as available in order to enable uninterrupted communication services for factory processes. Redundant networking and power equipment are employed to ensure high reliability and availability for factory processes; for example, redundant switches, servers, and power backups are utilized so that in the case of a failure, the redundant equipment can continue providing the requested communication services. Additionally, different power areas are defined to isolate power sources and backups. The security of the processes, generated data, and trustworthiness for stakeholders are other crucial aspects in factories and are typically handled by deploying private networks or through logical isolation in order to safeguard critical network infrastructures. Thus, network isolation through network slicing plays a pivotal role, not just for allocating required network resources but also for maintaining the reliability, latency, and security of factory processes.