What is a 5G core network (5GC)?
The 5G core network (5GC) is the brain of the 5G mobile communication network, which is responsible for managing and controlling the entire network.
The 5G core network is a collective name of many 5G NE equipment and is not specifically referred to as a network element device.
The 5G core network is divided into a 5G mobile core network and a 5G fixed network core network. The core network inside mobile communication is the mobile core network.
What are the 5G core network elements and what are the 5G core network functions?
What types of 5G core network functions are mainly from? Which 5G core network Normal or virtual Net elements are undertaken?
(1) AMF of the 5G core network elements
AMF (Access and Mobility Management Function Access and Mobility Management) supports a UE with different mobility management requirements. AMF can be classified as 4G MME.
Its 5G core network functions perform the following main tasks:
Non-access layer (NAS) signaling terminal;
NAS signaling security;
Access layer safety control;
A core network node signaling for mobility between 3GPP access networks;
Idle mode UE can be reached (including control and execution of paging retrans);
Registration Zone Management;
Support the mobility between the system and the system;
Access authentication;
Access authorization, including roaming permissions;
Mobility management control (subscriptions and policies);
Support network sections;
SMF selection;
The endpoint of the RAN Signaling Interface (N2), the endpoint of NAS (N1) signaling (MM message);
Responsible for the encryption and integrity protection of NAS messages, responsible for registration, access, mobility management, authentication, SMS, and other functions;
In addition, the assignment of the EPS BEARER ID is also responsible for interacting with the EPS network.
SMF of the 5G core network elements
SMF (Session Management Function, Session Management) is a session management function entity. The main functions of the SMF are:
The endpoint of the SM message of the NAS message;
Establishment, modification, release of the session;
Assignment management of UE IP;
DHCP function;
ARP Agent or IPv6 Neighbor Request Agent (Ethernet PDU Scene);
Select and control UPF for a session;
Collection of billing data and support charging interface;
Determines the SSC mode of a session;
Downlink data indication.
UPF of the 5G core network elements
UPF (user plane function, user plane management function) is a user plane functional entity, which is similar to GW (SGW + PGW) under 4G. The most important function is to be responsible for the routing of packets, and QoS stream mapping.
An anchor for mobility between RAT / RAT (when applicable);
External PDU and Data Network Interconnected Session Point;
Packet routing and forwarding (for example, support uplink classifier to support the business flow path to the data network, support the branch point to support the multi-hosted main PDU session);
Packet check (for example, the application flow detection based on the service data stream template and optional PFD received from SMF);
User plane partial policy rules implementation, such as gate control, redirect, and flow steering;
Legal interception (UP collection);
Traffic use report;
The QoS processing of the user plane, such as the UL / DL rate implementation, the reflection QoS mark in DL;
Uplink flow verification (SDF to QoS traffic mapping);
Transmission level group tag in uplink and downlink;
Downlink packet buffer and downlink data notification triggers;
Send one or more “end tags” and forward them to the source NG-RAN node.
Note: Not all UPF features need to be supported in an instance of the user plane function of the network segment.
PCF of the 5G core network elements
PCF (Policy Control Function, Policy Control) is the policy control function entity. Support a unified policy framework and manage network behavior, providing a policy rule to a network entity, accessing the Unified Data Warehouse (UDR) subscription information, and the PCF can only access the NDR of the same PLMN.
NEF of the 5G core network elements
NEF (Network Exposition Function, Network Service Rendering Function) is a network rendering function entity. The main functions of NEF are:
3GPP NEs are presented to other NEs through NEF;
NEF stores related information into NDR, or obtains relevant information from NDR, NEF can only access and its same PLMN NDR;
NEF provides appropriate security to ensure external applications to 3GPP networks;
The conversion of 3GPP internal and external related information, such as the conversion of DNN, S-NSSAI, and the like of AF-service-Identifier and 5G core network, especially network and user sensitive information must hide external network elements;
NEF can be accessed by accessing NDR to other network elements, and NEF can only access and its same PLMN UDR.
NRF of the 5G core network elements
NRF (NF Repository Function, NF Storage Function) is a network storage function entity. The main fuctions of NRF are:
Support business discovery functions, that is, NF-Discovery-Request sent by the network element and then provides the discovered network element information to the requester; maintain the features of the available NE instances and its supported business capabilities;
The characteristic parameters of a network element mainly include NE example ID, network element type, PLMN, network shard associated ID (such as S-NSSAI, NSIID), network element’s IP or domain name, network element capability information, support Business capability name, etc.
UDM of the 5G core network elements
The main functions of UDM (Unified Data Manager, Unified Data Management) are:
Generate 3GPP authentication certificate / authentication parameters;
Store and manage the permanent user ID (SUPI) of the 5G system;
Subscribe to information management;
MT-SMS submit;
SMS management;
Users’ service network element registration management (such as AMF, SMF, etc.) of the current terminal provides services.
AUSF of the 5G core network elements
AUSF (Authentication Server Function, Authentication Server Function) is an authentication server network element; supporting the authentication of 3GPP access and the authentication of Untrusted NON3GPP access.
UDR of the 5G core network elements
UDR (Unified Data Repository, Unified Data Warehouse), the responsible main functions are:
UDM stores subscription data or read subscription data;
PCF storage policy data or read policy data;
The disclosed data is stored or the disclosed data is read; the NF of the UDR and the UDR have the same PLMN, which is the same network, that is, the NUDR interface is a PLMN internal interface.
SMSF of the 5G core network elements
SMSF is an SMS function;
AN of the 5G core network elements
UPF of the 5G core network elements
UPF (User Plane Function User Function) Execute the following main functions:
Anchor points in the system and inter-system;
Connect to the external PDU session point of the data network;
Packet routing and forwarding;
Package check and user plane policy rule execution section;
Traffic use report;
Uplink classifier for supporting traffic routes to data networks;
Support for the branch point of the multi-homed main PDU session;
QoS processing for the user plane, such as packet filtering, gate, up and down speed implementation;
Uplink Service Verification (SDF to QoS Stream Mapping);
Downlink packet buffering and downlink data notification trigger.
5G core network architecture main features
Comparing the 5G core network with the 4G core network EPC, it can be seen that 5G compared to 4G is unchanged in basic functions such as authentication, mobility management, connection, and route, the method and technical means have changed, more flexible.
Mainly reflected in:
Mobility Management (AMF) and Session Management (SMF) separation, deployment of AMF and SMF levels;
Carrying and control separation, deployment hierarchies of UPF and SMF can also be separated;
AMF and UPF are based on business needs, signaling, and traffic, and the transmission resource is flexibly deployed; the service structure design is used, the network element function has made modules decompose coupling, and the interface is simplified.
Overall, the 5G core network has more flexible, but the deployment flexibility also has higher requirements for transmission, and network planning, network operation management.
5G core network architecture provides users with a data connection and data service services, based on NFV (Network Function Virtualization, Network Function Virtualization) and SDN (Software Defined Network, Software Definition Network), using services between control network elements The interface interacts.
The main features of the 5G core network system architecture are as follows:
Carrying and control separation: bearer and control can be extended and evolved independently centralized or distributed flexible deployment;
Modular function design: web sections can be made flexible and efficient;
NE interactive flow service: call on-demand, and serve repeatedly;
Each network element can directly interact with other network elements, or the message routing of the control plane can also be accepted by the intermediate network element;
The weak connection between wireless access and core network: 5G core network is an architecture associated with access and a convergence role, 3GPP and non-3GPP access 5G core network through the universal interface;
Support unified authentication framework;
Support stateless network features, that is, calculate resources and storage resource decoupling deployments;
Based on streaming QoS: Simplified the QoS architecture to improve network processing power;
Support for large concurrency access of the business that is deployed in local centralized deployment, a user-face feature can be deployed near access network to support low delay services, local service network access.
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