Impact on IMS NSA#4 / SA#2 Needs to retain the EPC No CS interworking from 5GS Core migration 5GC deployment Figure 9.11 - High-level overview of migration step analysis 5G Deployment Options Now, we have evaluated the different network deployment options. We either referred to the 4G core as the EPC or 5GC for 5G. In the next section, we will cover some of the motivations for the evolution of the EPC to 5GC at a high level and will compare the main differences between the EPC and 5GC. The evolution of the EPC to 5GC Let's now talk about 5GC and understand how the evolution of 5GC happened. We will first look at the main points that have driven the evolution of 5GC. After that, we will analyze the different functions that are defined in 5GC. So, at first glance, the 5GC architecture looks very different from that of the EPC, but this is not the case. 5GC evolved from the EPC. The first step of this evolution involved Control and User Plane Separation (CUPS) for the EPC. The EPC's CUPS functions were reorganized into a Service-Based Architecture (SBA). You should also know that there are three principles behind the evolution of the 5GC network. The first one is a smooth evolution, the second one involves maximizing the future value of 5G, and, finally, the third one is maintaining service continuity. CUPS and SBA have already been introduced throughout the book in relevant chapters. Now, we will just summarize the main differences between the EPC and 5GC within the context of NSA and SA deployments. A comparison of the EPC and 5GC The following table depicts the main differences between the EPC and 5GC from the perspective of 5G deployments and use cases (https ://www.gsma.com/futurenetworks/wp-content/ aploads/2018/04/Road-to-5G-Introduction-and-Migration_FINAL.pdf) The evolution of the EPC to 5GC Feature EPC (4G Core) 5GC (5G Core) S1 with per UE-assigned MME & SGW (in case of CUPS: single SGW-C and multiple SGW-U) & N2/3 common to all access with per UE-assigned Access network interface multiple PDN GWs ePDG an