New Radio connected to 5G Core Network

Description

NR/5GC denotes the complete 5G system architecture as standardized by 3GPP, comprising the New Radio (NR) Radio Access Network (RAN) and the 5G Core (5GC) network. This is the definitive, standalone 5G deployment where the gNB (the 5G base station) connects via the NG interface to the 5G Core's control plane (AMF, SMF) and user plane (UPF) functions. The architecture is fundamentally different from previous generations, built on a cloud-native, service-based design. Key interfaces include N1 (UE-AMF), N2 (gNB-AMF), N3 (gNB-UPF), and N4 (SMF-UPF).

How it works begins with the UE attaching to the network. The gNB routes the initial registration request to an Access and Mobility Management Function (AMF). The AMF acts as the single entry point for control plane signaling, handling registration, connection, and mobility management. For session management, the AMF interacts with the Session Management Function (SMF), which selects User Plane Functions (UPFs) to establish Protocol Data Unit (PDU) Sessions. User data then flows from the UE through the gNB and the UPF to the data network (DN), bypassing the control plane for efficiency. The gNB and 5GC communicate using the NG Application Protocol (NGAP) over the N2 interface.

Key components on the RAN side include the gNB, which handles all radio-related functions like scheduling, beamforming, and radio resource control (RRC). On the core side, the 5GC is decomposed into modular Network Functions (NFs) like the AMF, SMF, UPF, Unified Data Management (UDM), and Policy Control Function (PCF). These NFs communicate via standardized service-based interfaces (e.g., Namf, Nsmf) within a common framework. The role of NR/5GC is to deliver the full suite of 5G capabilities: enhanced Mobile Broadband (eMBB) with extreme data rates, Ultra-Reliable Low-Latency Communications (URLLC) for critical applications, and massive Machine-Type Communications (mMTC) for IoT. It enables network slicing, where multiple logical networks with specific characteristics are created on a common physical infrastructure, and supports edge computing by allowing UPFs to be deployed close to the user.

Purpose & Motivation

The NR/5GC architecture was created to address the limitations of previous network generations, particularly the 4G Evolved Packet Core (EPC), which was not designed to support the diverse and demanding requirements of 5G. The EPC had a monolithic, point-to-point interface architecture that was inflexible and slow to adapt to new services. The primary motivation was to build a core network that was inherently flexible, scalable, and capable of supporting a wide variety of services with vastly different needs—from high-speed video to low-power sensors to mission-critical industrial control.

Historically, early 5G deployments (often called 'Non-Standalone' or NSA) used the NR radio but still relied on the 4G EPC (EPC+NR), which acted as a bridge but could not unlock 5G's full potential. The creation of the native NR/5GC system (Standalone or SA) solves this by providing a clean-slate design. It introduces a service-based architecture (SBA) where network functions offer and consume services via APIs, enabling easier integration, automation, and network slicing. This solves the problem of operational complexity and allows for rapid service innovation.

Furthermore, NR/5GC addresses the need for network programmability and support for edge computing. By separating the user plane (UPF) from the control plane (SMF), the UPF can be deployed flexibly at the network edge, reducing latency for applications like autonomous vehicles or augmented reality. The architecture also inherently supports network exposure, allowing third-party applications to interact with network capabilities in a controlled manner. In essence, NR/5GC exists to transform the mobile network from a connectivity pipe into a programmable platform for digital services.