# A Study of 5G Edge-Central Core Network Split Options
## 5 Testbed Implementation and Evaluation Results  
In this section, we present the implementation in the form of a testbed of the proposed functional split models for the core network and for the network management. As the proposed alternatives are significantly complex in number of components to be deployed, we have implemented only a very limited set of these elements which provided significant results. Furthermore, although most of the implementation elements were executed on top of the same infrastructure, the tests were executed in isolation as not to have side effects from parallel running functionality. Figure 4: Network management and orchestration split options. For assessing the network characteristics of the three proposed deployment models, a testbed was developed including an edge and a central node on top of which three slices were deployed, i.e., parallel running software networks with its own configurations using the same hardware and virtualization infrastructure, as illustrated in Figure 5. As the measurements were targeted at the behavior of the system in uncongested situations, the exact performance of the infrastructure elements did not highly impact the overall measurements. As such, the edge and the central nodes were implemented using small capacity PCs. The edge and the central network were connected using an Ethernet and a satellite backhaul. The Ethernet backhaul represents the potentially shortest and highest capacity path. The satellite network was implemented using a real Over-The-Air (OTA) capacity provided by the space communication company SES on a GEO satellite and ST Engineering satellite equipment [9, 10]. The two networks were selected to represent the extreme cases for lowest and highest network delay to underline the effects of the communication between the edge and the central nodes. Other backhaul options such as the connectivity through a wireless or fixed network of a wide area network operator or directional wireless links can be seen as intermediary alternatives in terms of delay and capacity. The testbed implementation was based on the Fraunhofer FOKUS Open5 GCore [11], a reference 3 GPP standard-based toolkit, addressing the R&D market and implementing the core network functionality and other network functions in a highly flexible way. Although the Open5 GCore was integrated with a large number of commercially available base stations and UEs, for the presented measurements, we have used it with its own UE and gNB software emulations as it was simpler to monitor the status of the testbed and to maintain the RAN related side effects to a minimum. Instead, the link between the UE and the emulated gNB was implemented using an Ethernet connection. Furthermore, as we have used the same testbed setup for multiple demonstrations especially towards showcasing the advantages of the satellite network backhauling, a Data Network (DN) virtual machine with different domain specific applications. To simply change between the satellite and the ethernet backhaul, we added a Gateway (GW) virtual machine acting as a software access router for both the edge and the central infrastructure [12]. For the 5G core networks, the different procedures for the 5G registration, Packet Data Unit (PDU) session establishment and 5G deregistration were measured during functional tests. The measurements are presented for each of the deployment models together with the delay of communication between the SMF and UPF using the Packet Forwarding Control Protocol (PFCP). An additional control column was added including the median RTT across the backhaul as a control element. For the evaluation of the end-to-end network management, a similar setup with the one used for the control plane split was used having an edge and a central node  
Figure 5: Testbed implementation. connected this time with Ethernet and with a simulated satellite link.