In this tutorial we shall see 3GPP 5G network architecture.
5G architecture are of 2 types:
1. 5G architecture: This we shall see in this chapter
2. 5G Service based Architecture: This we shall see in the next chapter.
5G Architecture:
Below is how the network functions are separated by functionality:
The above image shows you 5G architecture. Here this architecture is similar to 4G architecture.
MME is replaced my AMF and S-GW is replaced by UPF.
We shall see the functionality of all the elements in brief.
RAN: Radio Access Network:
In 5G RAN is split into 2 types.
1. CU: Central Unit
2. DU: Distributed Unit
Multiple distributed units are connected to one central unit. This is called as CRAN. Cloud RAN architecture.
The splitting is done based on the layers. The splitting helps in virtualization of the network and reduce cost.
Below is how different splitting options are available:
Brief overview of network functionality
AMF: Access and Mobility Management Function
• Access Authorization including check of roaming rights;
• Termination point for RAN CP interfaces (N2)
• Registration Area management;
• Mobility Management (Reachability, Idle/Active Mode mobility state handling)
• Session Management Function (SMF) selection
• Similar to MME function in EPC.
SMF: Session Management Function
• Termination of NAS signaling related to session management
• Selection and control of UP function
• UE IP address allocation & management
• Policy and Offline/Online charging interface termination
• Lawful intercept (CP and interface to LI System)
• DL data notification
• Selection and control of UP function
• Control part of policy enforcement and QoS.
PCF: Policy Control Function
• 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)
UDM: Unified Data Management
Similar to HSS is LTE
User Data Convergence (UDC) concept: separates user information storage and management from the front end
UserDataRepository(UDR):storingandmanaging
subscriber information processing and network policies
NEF: Network Exposure Function
• Provide security for services for accessing 5G Core nodes
AUSF: Authentication Server Function
• Storage for Keys (part of HSS from EPC)
• Obtains authentication vectors from UDM
and achieves UE authentication.
UPF: User Plane Function
• 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)
AF: Application Functions
• 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).