# A Study of 5G Edge-Central Core Network Split Options
## 1 Introduction  
To be able to meet the requirements of diverse applications coming from the vertical markets, 5G networks need to provide customized functionality and deployment options. For the three service classes defined, enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communications (URLLC) and massive Machine Type Communication (mMTC) [1], along with the new functionality, it became important where the network functions are placed in the network as it directly reflects in the connectivity service characteristics. For example, multimedia use cases based on eMBB can use edge network functionality for local content distribution and to relieve the backhaul of extensive communication. Similarly, mMTC applications, such as sensor based smart cities applications, can acquire and process information from many devices locally and transmit only reduced insight to central entities reducing the number of needed connections. The movement of the functionality to the edge provides a privacy-aware, low delay and higher reliability network, two main features in the focus of the URLLC vertical markets like enterprise networks, Industry 4.0 or Public Protection and Disaster Relief (PPDR) [2]. Services on the 4G network were able to offer a ubiquitous and uniform connectivity service to the devices by fully centralizing the core network functionality and binding it with the Radio Access Networks (RAN) through high capacity backhauls. After, 5G proposed a more distributed and localized approach. It presumes that part of the functionality can be moved towards the edge of the network and integrated with a local access network as illustrated in Figure 1. This direction is also enforced by the drastic decrease in infrastructure costs enabling affordable edge cloud deployments and by the softwarization of the network functions, enabling their deployment on any compute node available. The 3 GPP network standards factor the softwareization, providing an optimized Service-Based Architecture (SBA) [3; 4] in which the network functions are communicate using highly adaptable and easy to develop interfaces using web service protocols. However, the standard leaves open how the 5G system should be deployed. This article proposes a comprehensive set of 5G network deployment models and analyzes their benefits for a varied number of infrastructure and backhaul situations. Our main contribution is the analysis of different network function placement models and functional splits as blueprints to deploy the standard 3 GPP 5G architecture. With this, the 5G network architecture can be customized to meet the specific use case requirements while at the same time being aware of the implications of the underneath system. The opportunities brought by each deployment are practically evaluated through a comprehensive 5G testbed implementation, giving an indication on the opportunities of each deployment for the use cases. Furthermore, a set of considerations followed by a practical evaluation is made on the end-to-end network management for such a distributed infrastructure being a significant feature for the further administration of the deployed 5G networks. The centralized and the distributed network management approaches are assessed as the two major options to handle such an infrastructure. Through the practical evaluation, it is proven that many of the proposed functional split models are feasible for deployment, each with specific advantages for specific use cases. This provides a reliable basis for the further trials and customizations of the 5G networks in the direction of vertical markets deployments and further beyond-5G standardization. The rest of this paper is structured as follows. Section 2 provides a concise overview of the 5G system and related work. Section 3 presents the different core split options and assesses their characteristics while Section 4 presents the equivalent for network management. Section 5 provides the testbed description and the evaluation results.