5G Core Network Architecture

5G Core Architecture Overview

• The session focuses on the 5G core architecture as detailed in 3GPP technical specification 23.501.
• The session reviews 5G network functions and their architecture as well as the differences in service-based interfaces compared to older generations such as 2G, 3G and 4G.
• Differences in subscriber and user equipment identities between 5G, 4G and 3G are reviewed.

Core Components of a 5G System

• A 5G system consists of three key parts including a mobile phone/user equipment, a radio access network, and a core network.
• A 5G access network uses new radio technology.
• The 5G core network connects to the 5G access network and is specified in technical specification 23.501.
• 5G RAN refers to any 3GPP specified standalone or non-standalone 5G radio access network, typically the new radio or GnodeB.

5G Architecture and Design Principles

• 5G system architecture enables data connectivity and services using network function virtualization and software-defined networking.
• The architecture uses service-based interactions between control plane network functions.
• The control plane of the 5G core is based on service-based interfaces.
• A 5G core network can support multiple access technologies, including 4G LTE, 5G radio, Wi-Fi, and fixed access.
• The 5G core architecture separates the user plane and control plane functions.
• Scalability is possible in the user plane, allowing for user plane functions close to the user for delay-sensitive services and centralized functions for non-delay-sensitive services.
• A core network should allow user access, manage mobility and handle end-to-end session management from start to termination.
• Authentication is a crucial feature to prevent unauthorized network access.
• User data management stores subscriber information, services, and quality of service details in a database.
• Policy control manages the end-to-end user experience and enforces policies related to quality of service and usage.
• The user plane handles user traffic, acting as a pipeline for internet connectivity.

Evolution from 4G EPC to 5G

• In 4G EPC, MME managed access, mobility and session management.
• Serving and packet gateways managed session management for the control plane part.
• HSS handled authentication, user data, and subscription data.
• PCRF implemented policy control.
• Serving and PDN gateways managed the user plane and end-to-end data traffic.

5G Network Functions

• The access and mobility management function handles access and mobility of users.
• The session management function manages sessions.
• The authentication server function handles authentication separately.
• User data management (UDM) manages subscriber data, subscriptions, and services.
• Policy control function (PCF) takes care of policy control, replacing PCRF in 5G.
• User plane function manages user plane traffic.
• Network functions in 5G are more modular where single network function handles session management.

Principles of 5G Core Design

• Separation of user plane and control plane functions, similar to 4G and 5G EPC.
• Modular function design.
• Each function should manage specific functionality, avoiding overlap.
• Dedicated network functions should handle specific requirements.
• Procedures are defined as a service, which means there is no point-to-point connectivity between network functions.
• Network functions interact with each other as needed to request services.
• Access networks and core networks are not interdependent where any access network can be used with 5G, unlike previous architecture.
• A unified authentication framework is supported, for both 3GPP and non-3GPP devices.
• The architecture supports stateless network functions.
• Network functions are stateless due to network function virtualization (NFV) and cloud technologies.
• Network functions are decoupled from hardware.
• 5G core network exposes capabilities to external applications through APIs.
• Support for concurrent access to local and centralized services.
• Support for roaming, including home routed and local breakout options is supported.

Key Features of 5G Core

• Supports standalone and non-standalone NR capabilities.
• Supports non-SIM based devices and non-3GPP accesses like Wi-Fi.
• Utilizes a service-based architecture where network functions connect through a service bus.
• 5G core is cloud native.
• User equipment can connect to multiple network slices simultaneously.
• User equipment can access both local and centralized user planes.

Fixed Line Access through 5G Core

• Addresses how telecom operators can provide high speed wireline broadband using a 5G core network.
• Wireline internet or fixed broadband connects devices through a Wi-Fi router (CPE).
• The Wi-Fi router connects to a gateway and then to AMF and the user plane.
• Covered in 3GPP release 16 as part of 5G core phase 2 deployment.

5G Core Architecture Representations

• Representation of the 5G core system with point-to-point connections between network functions or service-based architecture.
• 3GPP supports service-based architecture where the control part is service-based.
• The control plane functions use service-based interfaces, while user plane functions are point-to-point connected.

Benefits of 5G

• Provides standalone and non-standalone capabilities for new radio.
• Supports network slicing and distributed cloud.
• Offers mobility on demand with service differentiation.
• Supports fixed wireless access.
• Supports devices without SIM cards.
• Supports non-3GPP access.

Network Interfaces

• Wireless devices connect to 5G RAN, which connects to AMF for the control plane and UPF for the user plane.
• N1 interface is used for the connection between UE and AMF.
• N2 interface connects the GnodeB or new radio part to AMF.
• N3 interface connects the radio access network to the user plane or UPF.