# A Study of 5G Edge-Central Core Network Split Options
## 2 Related Work  
In this section, we concisely present the 5G architecture. To present such a complex system, a very large number of functional selections and simplifications are made. The architecture presented (Figure 2) is based on a combination of a minimal 3 GPP Packet Core and a simplified network management and orchestration as this presents enough functional diversity. The 5G system, as standardized by 3 GPP ([3,4]), is composed of a User Equipment (UE) representing the mobile device, of a Radio Access Network (RAN), and of the Core Network (CN). The core network enables the connectivity of the subscribers with the following components. The Access and Mobility Function (AMF) includes the functionality for communication with both the UE and the RAN. It performs access and registration procedures, mobility management, and acts as a proxy for other management layers handled by other network functions. For authentication and authorization specific algorithms, the AMF uses the functionality provided by the Authentication User Service Function (AUSF). The Session Management Function (SMF) controls the User Plane Functions (UPF)  
Figure 1: Major Trends in 5G Networks. to execute data path operations and set QoS parameters. Next to the subscriber state maintained in each network function, a centralized subscription profile is maintained in the Unified Data Management (UDM) for synchronization reasons. Much of the state information is replicated and, in many procedures, the UDM must be queried and updated to maintain this synchronization. For the end-to-end data plane, the UE is connected to the RAN over the radio interface and then from the RAN through one or more UPFs to the Data Network (DN). In general, the UE is executing different procedures with the core network for authentication, authorization and access control including session establishment and mobility management resulting into end-to-end data paths through which the communication is executed. As illustrated in Figure 2, potentially the core network functionality can be placed either at the edge or at the central infrastructure of the network. Due to resource consumption and synchronization reasons, only one network function should be used for each subscriber, be it at the edge or central. It is generally assumed that the edge infrastructure has significantly less compute resources and thus capacity to deploy applications than the central infrastructure. Additionally, the edge and the central infrastructure are interconnected via a backhaul network which could be based on optic fibers, wireless, satellite or a combination of them, resulting in different capacity and delay levels. The backhaul characteristics are translated directly into the control plane procedures as well as into the data plane delivery, thus mattering where the network functions are placed. The 5G system has a standardized management system [5]. It is composed of many monitoring probes at different levels from infrastructure, software network components enabling a comprehensive understanding of the system's performance including resources consumed, failures and reliability limitations, security breaches as well as related to the subscribers. The information from these probes is gathered in a monitoring server where it is further distributed to the network management elements in charge of interpreting the different data and making decisions on how to adapt the system. Based on the decision, the network management communicates with different Element Managers modifying the different network functions. Through its orchestration part, the network management also enables the deployment and the configuration of network functions and their introduction into the system. For these operations the same monitoring system and commands are used, however more oriented to the virtual infrastructure managers then to the network functions themselves. Figure 2: Simplified 5G Architecture.