5G-NR Call Flow Procedures

Overview

This section is for 5G NR procedure flows such as registration, PDU session establishment, handover, paging, service request, and RRC setup. It can be expanded with UE, gNB, AMF, SMF, and UPF level signaling diagrams and step-by-step message breakdowns.

5G-NR Call Flow

• Access & Registration
• PDU Session Management
• Mobility Procedures
• RRC Procedures
• Security Procedures
• Voice Call Procedures
• Network Slice Procedures
• QoS / Policy Procedures
• Data Path Management
• Roaming Procedures
• Non-Terrestrial Network (NTN) Procedures
• Multi-Access Procedures

Access & Registration

Covers initial access, registration, authentication entry points, service request triggers, and the end-to-end UE to AMF registration sequence in 5G networks.

Key interfaces involved:

• N1
• N2
• NAS signaling

PDU Session Management

Includes PDU session establishment, modification, release, SSC handling, and user-plane tunnel setup between the UE, AMF, SMF, and UPF.

Key network functions:

• AMF
• SMF
• UPF

Mobility Procedures

Focuses on handover, tracking area updates, inter-gNB mobility, path switch, and session continuity during movement across the network.

RRC Procedures

Includes RRC setup, resume, reconfiguration, release, paging response, and other radio control exchanges between the UE and gNB.

Key interfaces involved:

• UE
• gNB

Security Procedures

Describes authentication, NAS security activation, AS security setup, key derivation, and security mode related call flows in 5G.

Voice Call Procedures

Covers VoNR and IMS-related signaling such as registration support, session establishment, emergency handling, and fallback-related voice flows.

Also includes fallback procedures.

Network Slice Procedures

Captures slice selection, allowed NSSAI handling, rejected S-NSSAI scenarios, and slice-aware session establishment procedures.

QoS / Policy Procedures

Groups call flows related to QoS flow setup, policy control interaction, PCC updates, GBR handling, and session rule enforcement.

Data Path Management

Focuses on user-plane path creation, updates, and release between the access network and UPF for active data sessions.

Roaming Procedures

Explains home-routed and local breakout roaming call flows, inter-PLMN registration, security handling, and session continuity in roaming cases.

Non-Terrestrial Network (NTN) Procedures

Provides a place for satellite and other non-terrestrial 5G procedures where large delay, orbital mobility, and NTN-specific access handling must be managed.

Multi-Access Procedures

Covers traffic steering and multi-access continuity mechanisms such as ATSSS across 5G and Wi-Fi or other access networks.

Recommended Reference Specifications

From 3rd Generation Partnership Project: