5G Network Architecture

5G Network Architecture:


            In this blog, we will see 5G network architecture nodes, their functionality and interfaces between different nodes. it is vary important to know about all the nodes and their functionality to understand the whole concept of 5G architecture.
Below description is taken from 3gpp TS.

In Detailed:

Core network service based architecture:

AMF: Access and Mobility Management Function:- 
             Like in LTE MME, In NR AMF provide the similar services to the access network and core network component. general functions of AMF are to provide the mobility management, Authentication management, NAS related management to UE and SMF selection types of services.

=>Termination point for RAN Control Plane interfaces (NG2).
=>UE Authentication and Access Security procedures.
=>Mobility Management (handover Reach-ability, Idle/Active Mode mobility state. handling)
=>Registration Area management.
=>Access Authorization including check of roaming rights; 
=>Session Management Function (SMF) selection
=>NAS(non access stratum) signaling including NAS Ciphering and Integrity protection, termination of MM NAS and forwarding of SM NAS (NG1).
=>AMF obtains information related to MM from UDM.
=>May include the Network Slice Selection Function (NSSF) 
=>Attach procedure without session management adopted in CIoT implemented in EPC is defined also in 5GCN (registration management procedure) 
=>User Plane (UP) selection and termination of NG4 interface (AMF has part of the MME and PGW functionality from EPC.

AUSF: services Authentication Server Function:  The main function of AUSF is to provide the services for Authentication procedure and communicate directly with UDM and AMF for accessing and providing the subscriber information.

=>Contains mainly the EAP authentication server functionality 
=>Storage for Keys (part of HSS from EPC) 
=>Obtains authentication vectors from UDM and achieves UE authentication. 72 NF Repository Function (NRF) 
=>Provides profiles of Network Function (NF) instances and their supported services within the network 
=>Service discovery function, maintains NF profile and available NF instances. (not present in EPC world) NRF offers to other NFs the following services: 
=>OAuth2 Authorization Core network functions 73 Core network functions Network Exposure Function (NEF) 
=>Provides security for services or AF accessing 5G Core nodes 
=>Seen as a proxy, or API aggregation point, or translator into the Core Network 

Policy Control Function (PCF) 

=>Expected to have similarities with the existing policy framework (4G PCRF) 
=>Updates to include the addition of 5G standardized mobility based policies (part of the PCRF functionality from EPC) 

Session Management Function (SMF) :
=>DHCP functions 
=>Termination of NAS signaling related to session management 
=>Sending QoS/policy N2 information to the Access Network (AN) via AMF
=>Session Management information obtained from UDM 
=>DL data notification 
=>Selection and control of UP function 
=>Control part of policy enforcement and QoS. 
=>UE IP address allocation & management 
=>Policy and Offline/Online charging interface termination 
=>Policy enforcement control part 
=>Lawful intercept (CP and interface to LI System) Core network functions.

Unified Data Management (UDM) :

=>Similar functionality as the HSS in Release 14 EPC User Data Convergence (UDC) concept: separates user information storage and management from the front end 
=>User Data Repository (UDR): storing and managing subscriber information processing and network policies 
=>The front-end section: Authentication Server Function (AUSF) for authentication processing and Policy Control Function (PCF). Core network functions 

User Plane Function (UPF) :
=>Allows for numerous configurations which essential for latency reduction
=>Anchor point for Intra-/Inter-RAT mobility 
=>Packet routing and forwarding 
=>QoS handling for User Plane 
=>Packet inspection and PCC rule enforcement 
=>Lawful intercept (UP Collection) 
 Roaming interface (UP)
=>May integrate the FW and Network Address Translation (NAT) functions 
=>Traffic counting and reporting (UPF includes SGW and PGW functionalities) 

Application Functions (AF) 
=>Services considered to be trusted by the operator
=>Can access Network Functions directly or via the NEF 
=>AF can use the PCF interface PCF for requesting a given QoS applied to an IP data flow (e.g., VoIP). 
=>Un-trusted or third-party AFs would access the Network Functions through the NEF (same as AF in EPC) Network Slice Selection Functions (NSSF) 
=>Selecting of the Network Slice instances to a UE.
=>Determining the AMF set to be used to serve the UE.
=>The Application Function (AF) can be a mutually authenticated third party. – Could be a specific 3rd party with a direct http2 interface or a inter-working gateway exposing alternative API’s to external applications. 
=>Enables applications to directly control Policy (reserve network resource, enforce SLAs), create network Slices, learn device capabilities and adapt service accordingly, invoke other VNF’s within the network… 
=>Can also subscribe to events and have direct understanding of how the network behaves in relation to the service delivered.

 Data Network (DN):

=> Services offered: Operator services, Internet access, 3rd party 

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