5G-NR Call Flow Procedures
Call flow procedures for 5G NR and 5G core signaling, mobility, registration, and session management.
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.
Browse Procedure Groups
Jump directly to the part of the 5G call-flow library you need for tracing, learning, or troubleshooting.
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.
| Call Flow | Description |
|---|---|
| 5G Initial Registration | UE registers with the 5G Core |
| Periodic Registration Update | UE refreshes registration timer |
| Mobility Registration Update | Registration triggered by mobility |
| Emergency Registration | Registration for emergency services |
| Deregistration Procedure | UE or network deregisters session |
| Network Initiated Deregistration | Core network removes UE |
| Identity Request Procedure | UE identity verification |
Key interfaces involved:
PDU Session Management
Includes PDU session establishment, modification, release, SSC handling, and user-plane tunnel setup between the UE, AMF, SMF, and UPF.
| Call Flow | Description |
|---|---|
| PDU Session Establishment | UE creates data session |
| PDU Session Modification | Change QoS or resources |
| PDU Session Release | End of session |
| Network Requested PDU Session | Network initiates session |
| PDU Session Authentication | Session-level authentication |
| Secondary PDU Session Setup | Additional session creation |
Key network functions:
Mobility Procedures
Focuses on handover, tracking area updates, inter-gNB mobility, path switch, and session continuity during movement across the network.
| Call Flow | Description |
|---|---|
| Idle Mode Mobility | Cell reselection |
| Connected Mode Handover | UE moves between cells |
| Inter-gNB Handover | Handover between base stations |
| Inter-AMF Mobility | UE moves between AMF regions |
| Xn Handover | gNB to gNB handover |
| N2 Handover | Core assisted handover |
| Inter-RAT Handover | 5G to LTE mobility |
RRC Procedures
Includes RRC setup, resume, reconfiguration, release, paging response, and other radio control exchanges between the UE and gNB.
| Call Flow | Description |
|---|---|
| RRC Connection Setup | UE establishes radio connection |
| RRC Reconfiguration | Radio parameters updated |
| RRC Reestablishment | Recover connection after radio failure |
| RRC Release | Connection released |
| RRC Resume | Resume from idle |
| RRC Suspend | Enter suspended state |
| Paging Procedure | Network pages UE |
| Measurement Reporting | UE sends radio measurements |
Key interfaces involved:
Security Procedures
Describes authentication, NAS security activation, AS security setup, key derivation, and security mode related call flows in 5G.
| Call Flow | Description |
|---|---|
| Authentication Procedure | UE authentication |
| Security Mode Command | Activate encryption |
| Relay Key Procedure | Relay-specific NAS key and authentication exchange |
| Key Derivation Procedure | Generate security keys |
| Security Context Update | Update encryption keys |
| Integrity Protection | Control plane protection |
Voice Call Procedures
Covers VoNR and IMS-related signaling such as registration support, session establishment, emergency handling, and fallback-related voice flows.
| Call Flow | Description |
|---|---|
| VoNR Call Flow and Procedures | Complete VoNR architecture and procedure overview |
| VoNR Registration | IMS registration over NR |
| VoNR Mobile Originated Call | UE initiates call |
| VoNR Mobile Terminated Call | UE receives call |
| VoNR Call Termination | End voice session |
| VoNR Call Hold / Resume | Voice session modification |
| VoNR Emergency Call | Emergency voice service |
Also includes fallback procedures.
| Call Flow | Description |
|---|---|
| EPS Fallback | 5G to LTE voice fallback |
| VoLTE Call Flow and Procedures | Voice over LTE / IMS call setup and session flow |
| SRVCC Procedure | Single Radio Voice Call Continuity to legacy CS voice |
Network Slice Procedures
Captures slice selection, allowed NSSAI handling, rejected S-NSSAI scenarios, and slice-aware session establishment procedures.
| Call Flow | Description |
|---|---|
| Network Slice Selection | UE selects slice |
| Slice Authentication | Authorization for slice |
| Slice Mobility Procedure | Mobility across slices |
QoS / Policy Procedures
Groups call flows related to QoS flow setup, policy control interaction, PCC updates, GBR handling, and session rule enforcement.
| Call Flow | Description |
|---|---|
| QoS Flow Establishment | QoS parameters setup |
| QoS Flow Modification | Update QoS |
| QoS Flow Release | Remove QoS flow |
| PCC Policy Enforcement | Policy control |
Data Path Management
Focuses on user-plane path creation, updates, and release between the access network and UPF for active data sessions.
| Call Flow | Description |
|---|---|
| User Plane Establishment | Setup UPF routing |
| User Plane Modification | Update path |
| User Plane Release | Remove routing |
| UL CL Procedure | Uplink classifier path change |
Roaming Procedures
Explains home-routed and local breakout roaming call flows, inter-PLMN registration, security handling, and session continuity in roaming cases.
| Call Flow | Description |
|---|---|
| 5G Roaming Registration | UE registers in visited network |
| Home Routed Roaming | Traffic via home network |
| Local Breakout Roaming | Traffic via visited network |
| Roaming Authentication | Cross-network authentication |
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.
| Call Flow | Description |
|---|---|
| NTN Registration | Satellite network registration |
| NTN Handover | Satellite mobility |
| NTN Timing Advance | Large propagation delay handling |
Multi-Access Procedures
Covers traffic steering and multi-access continuity mechanisms such as ATSSS across 5G and Wi-Fi or other access networks.
| Call Flow | Description |
|---|---|
| ATSSS Traffic Steering | Traffic switching between WiFi/5G |
| Access Traffic Switching | Multi-access handover |
| Access Traffic Splitting | Multi-path data transmission |
Recommended Reference Specifications
From 3rd Generation Partnership Project:
| Spec | Description |
|---|---|
| TS 23.501 | 5G System Architecture |
| TS 23.502 | 5G Procedures |
| TS 24.501 | NAS Signaling |
| TS 38.300 | NR Overall Description |
| TS 38.331 | RRC Protocol |