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5G Deregistration Procedure Explained

call-flow 5G NR | 5GC | NAS | Mobility

Introduction

The Deregistration procedure in 5G networks allows the User Equipment (UE) or the network to release the UE’s registration context in the 5G Core (5GC).

Once deregistration is completed:

the UE is no longer reachable for paging
mobility management context is removed
data sessions are released
security context may be deleted

The procedure is defined by the 3rd Generation Partnership Project in:

3GPP TS 23.502 - 5G System Procedures
3GPP TS 24.501 - NAS Protocol

5G Deregistration procedure call flow diagram showing UE, gNB, and AMF signaling

Types of Deregistration

There are two major types of deregistration in 5G networks.

Type	Trigger
UE Initiated Deregistration	UE powers off or leaves network
Network Initiated Deregistration	Network releases UE context

Network Elements Involved

UE (User Equipment)

The UE may trigger deregistration when:

the device powers off
the SIM is removed
the user disables network connectivity

gNB (5G Base Station)

The gNB forwards NAS signaling between the UE and the core network.

AMF (Access and Mobility Management Function)

The AMF manages UE registration state and removes UE context during deregistration.

Interfaces Used

Interface	Description
NR-Uu	Radio interface between UE and gNB
N1	NAS signaling between UE and AMF
N2	Control plane between gNB and AMF

UE Initiated Deregistration Call Flow

When the UE decides to leave the network, it sends a Deregistration Request.

UE                gNB                AMF
 |                 |                  |
 |---Deregistration Request--------->|
 |                 |----N2---------->|
 |                 |                  |
 |<--Deregistration Accept-----------|
 |                                   |
 |-----UE Context Release------------|

Step-by-Step Explanation

Step 1: Deregistration Request

The UE sends a Deregistration Request NAS message.

Typical triggers include:

UE power off
SIM deactivation
manual network disconnect

Important parameters to check

Engineers should verify:

deregistration type
UE identity (5G-GUTI)
switch-off indicator

Step 2: Network Processing

The AMF processes the request and performs several actions:

release UE context
release mobility information
terminate active sessions

The network may also release associated PDU sessions.

Important parameters to check

Check:

UE context release cause
PDU session release events
AMF context removal

Step 3: Deregistration Accept

The AMF sends a Deregistration Accept message.

After this step:

the UE is no longer registered
paging is disabled
NAS context is removed

Network Initiated Deregistration

Sometimes the network forces deregistration.

Typical scenarios include:

subscription cancellation
network maintenance
policy enforcement
roaming restrictions

Network Initiated Deregistration Call Flow

AMF                gNB                UE
 |                  |                 |
 |--Deregistration Request---------->|
 |                  |----N2---------->|
 |                  |                 |
 |<--Deregistration Accept-----------|
 |                                   |
 |------UE Context Release---------->|

Key NAS Messages

Message	Purpose
Deregistration Request	Trigger deregistration
Deregistration Accept	Confirm deregistration
UE Context Release	Release UE context

Deregistration Causes

Common deregistration reasons include:

UE power off
subscription expiration
mobility restrictions
security issues
operator policy

Deregistration vs Registration

Feature	Registration	Deregistration
Purpose	Connect UE to network	Remove UE from network
Trigger	UE attach or update	UE or network request
Result	UE reachable	UE unreachable

Troubleshooting Deregistration Issues

Unexpected Deregistration

Possible causes:

AMF overload
subscription policy enforcement
roaming restrictions

UE Cannot Deregister

Possible causes:

NAS signaling failure
RRC connection problems
network configuration issues

Data Sessions Not Released

Possible causes:

SMF session cleanup failure
UPF context retention
session timeout misconfiguration

Relevant 3GPP Specifications

The deregistration procedure is defined in:

3GPP TS 23.502 - 5G System Procedures
3GPP TS 24.501 - NAS Protocol
3GPP TS 38.300 - NR Architecture

Published by the 3rd Generation Partnership Project.

Summary

The 5G Deregistration procedure removes the UE’s registration context from the 5G Core network. It can be triggered either by the UE or the network and ensures that resources are released and subscriber context is properly cleared.

This procedure is important for:

network resource management
subscriber policy enforcement
maintaining accurate UE location tracking