 JavaScript Object Notation (JSON) Data Interchange Format, IETF RFC 8259. Available at: https://tools.ietf.org/html/rfc8259 (accessed August 28, 2019). 3 5G System Overview Draves, R. and Thaler, D. (2005). Default router preferences and more-specific routes. IETF RFC 4191. Available at: https://tools.ietf.org/html/rfc4191 (accessed August 28, 2019). Fajardo, V., Arkko, J., Loughney, J., and Zorn, G. (2012). Diameter Base Protocol. IETF RFC 6733. Available at: https://tools.ietf.org/html/rfc6733 (accessed August 28, 2019). International Telecommunication Union (ITU), Standardization Bureau (2018). Operational Bulletin No. 1156. Available at: http://handle.itu.int/11.1002/pub/810cad63-en (accessed August 28, 2019). 3.3 NG Radio Access Network NG Radio Access Network Sasha Sirotkin Intel Corporation, Israel 3.3.1 Introduction In the present section we provide an overview of the RAN part of the 5G System. In order to support 5GC and NR, 3GPP have developed a new RAN, referred to as NG-RAN. Conceptually, it resides between a UE and a 5GC, as shown in Figure 3.3.1.5 NG-RAN is a collection of base stations, or gNBs and ng-eNBs, interconnected by the Xn interface and connected to the 5GC via the NG6 interface. NG-RAN terminates the Uu air interface toward a UE and therefore supports the NR physical layer (PHY) and protocol stacks, described in Sections 3.5 and 3.4, respectively. Both ng-eNBs and gNBs are part of NG-RAN, as they terminate NG-RAN network inter- faces (e.g. Xn and NG7), however they provide different air interface accesses - Long-Term Evolution (LTE) and NR, respectively. This is different compared to all other technologies previously defined by 3GPP (e.g. LTE), where a RAN only supports one air interface and interworking with other technologies is only supported using handovers via the core network or specific dual-connectivity technologies (e.g. LTE-Wi-Fi interworking using LTE-WLAN Radio Level Integration with IPsec tunnel [LWIP]). 5G supports not only AMF/UPF AMF/UPF ((q)) ((q)) NG-RAN ((q)) ((p)) ng-