Description
The 5G Mobility Management (5GMM) protocol is a non-access stratum (NAS) protocol defined in 3GPP specifications, primarily in TS 24.501. It operates between the User Equipment (UE) and the Access and Mobility Management Function (AMF) in the 5G Core Network (5GC). 5GMM is responsible for managing the mobility and registration context of the UE, ensuring it can securely and efficiently access network services. It establishes and maintains the NAS signaling connection, which is essential for all control-plane communications between the UE and the core network, independent of the underlying radio access technology (e.g., NG-RAN, non-3GPP access).
5GMM operates based on specific states that define the UE's registration status with the network. The two primary states are 5GMM-REGISTERED and 5GMM-DEREGISTERED. In the REGISTERED state, the UE has successfully performed registration with the AMF, and a NAS signaling connection is established, allowing the UE to initiate service requests, receive paging, and maintain its mobility context. In the DEREGISTERED state, the UE is not registered, and the network does not maintain a context for it, though the UE may still perform initial registration procedures. 5GMM also manages substates like 5GMM-IDLE and 5GMM-CONNECTED, which reflect the connectivity status of the NAS signaling link.
Key procedures managed by 5GMM include initial registration, periodic registration update, mobility registration update (e.g., when the UE moves to a new tracking area), deregistration (initiated by the UE or network), and service request. The service request procedure is crucial as it transitions the UE from 5GMM-IDLE to 5GMM-CONNECTED mode to establish user-plane resources for data transfer. 5GMM also handles authentication and security by interacting with the Authentication Server Function (AUSF) and Security Anchor Function (SEAF) to ensure secure NAS signaling, including integrity protection and encryption of NAS messages.
5GMM is tightly integrated with other 5G core network functions. It works in conjunction with the Session Management Function (SMF) via the AMF to manage Protocol Data Unit (PDU) sessions. While 5GMM handles mobility and registration, session-specific parameters are managed by the 5G Session Management (5GSM) protocol. This separation allows for more flexible and scalable network architectures, supporting features like network slicing and edge computing. 5GMM also supports enhanced mobility scenarios, including handovers between 3GPP and non-3GPP access networks, and interworking with EPS (Evolved Packet System) for fallback scenarios.
Purpose & Motivation
5GMM was created as part of the 5G system architecture to address the limitations of the Evolved Packet System (EPS) Mobility Management (EMM) protocol used in 4G LTE. With the introduction of 5G, there was a need for a more flexible, scalable, and efficient mobility management protocol to support diverse use cases, including enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC). EMM, while effective for 4G, was not designed to handle the increased complexity, network slicing, and heterogeneous access integration required for 5G.
The primary problems 5GMM solves include simplifying signaling procedures to reduce latency, supporting seamless mobility across multiple access types (e.g., 3GPP NG-RAN, Wi-Fi, fixed networks), and enabling efficient network resource utilization. It introduces a service-based architecture (SBA) in the core network, where the AMF acts as a single entry point for NAS signaling, decoupling mobility management from session management. This separation allows for independent scaling and optimization of functions, which is critical for deploying network slices tailored to specific service requirements.
Historically, mobility management in previous generations (e.g., 4G EMM) was tightly coupled with session management, leading to less flexibility. 5GMM addresses this by defining clear state models and procedures that reduce signaling overhead and improve power efficiency for devices, especially IoT sensors. It also enhances security by incorporating new authentication frameworks and supporting concurrent multiple registrations for different network slices. The creation of 5GMM was motivated by the need to support a wider range of deployment scenarios, from dense urban areas to industrial IoT, while maintaining backward compatibility and interworking with 4G networks through procedures like handover and fallback.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (212 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the 5GMM function was newly introduced, establishing the core NAS protocol for 5G mobility management. This foundational release defined the 5GMM state machine with its deregistered and registered states and substates, specified procedures for registration over 3GPP (N1 mode) and non-3GPP access, and introduced new 5GMM cause codes. It also detailed the handling of key 5GMM parameters like the 5G-GUTI and ngKSI, and defined interworking procedures with EPS, including parameter coordination for single-registration mode operation.
- 5GMM parameter handling for TAU rejected with EMM cause #9 TS 24.301CR3047
- 5GMM context handling TS 24.301CR3063
- Introduction of 5GMM cause #15 TS 24.501CR0158
- Correct 5GMM reference used in the handling of the emergency numbers procedures TS 24.301CR3088
- Update of handling of 5GMM parameters in EPS TS 24.301CR3115
- 5GMM parameters handling for 5GC interworking TS 24.301CR3131
+ 26 more changes
In Release 16, key 5GMM enhancements included defining new 5GMM cause values for CAG and SNPNs, adding a UE capability for SRVCC handover to UTRAN, and introducing an LCS indication within the 5GMM capability. The release also specified detailed handling for new and existing cause values, such as #72 for SNPN access via a PLMN and #11 for abnormal cases, while refining procedures for coordination between 5GMM and EMM/GMM, particularly in single-registration mode.
- 5GMM capability for SRVCC from NG-RAN to UTRAN TS 24.501CR1187
- Abnormal case handling for receipt of 5GMM cause value #11 from a PLMN TS 24.501CR1229
- 5GMM cause value for CAG TS 24.501CR1057
- 5GMM capability update for eNS TS 24.501CR1316
- Addition of LCS indication in 5GMM capability and 5GS NW capability TS 24.501CR1335
- Ethernet header compression for CP CIoT – 5GMM aspects TS 24.501CR2165
+ 66 more changes
In Release 17, key enhancements to the 5GMM function included new procedures and cause codes for satellite access, support for the Network Slice-Specific Authentication and Authorization (NSAG) capability, and refined handling for specific reject causes like #78 and #79. The release also introduced mechanisms for storing 5GMM information during SNPN operation and clarified the use of the Equivalent PLMN list. Furthermore, it defined the reset of the registration attempt counter upon receiving certain EMM reject causes and added a service request procedure for handling non-integrity protected reject messages.
- New 5GMM cause for satellite access TS 24.501CR3101
- MCC list for 5GMM message TS 24.501CR3100
- 5GMM procedures for satellite access for reject cause on UE location - alternative handling TS 24.501CR3217
- Support NSAG in 5GMM capability TS 24.501CR4295
- Storage of 5GMM information for UEs in SNPN access operation mode TS 24.501CR3262
- The handling of 5GMM#79 TS 24.501CR3947
+ 53 more changes
In Release 18, key 5GMM enhancements included improved support for Standalone Non-Public Networks (SNPNs) by defining the handling of equivalent SNPNs and associated parameters in connected mode with RRC inactive indication. The release also introduced a dedicated 5GMM state for managing unavailability periods and added a new cause code (#15) to explicitly reject access via Satellite NG-RAN. Furthermore, it refined inter-system mobility through enhanced coordination procedures between 5GMM and EMM states in single registration mode.
- Equivalent SNPNs usage in 5GMM-CONNECTED mode with RRC inactive indication TS 24.501CR4839
- Equivalent SNPNs: NSSAIs, network-assigned UE radio capability ID, maximum number of established PDU sessions and 5GMM parameters in annex C stored per selected entry TS 24.501CR5027
- 5GMM procedure updates for LADN per DNN & S-NSSAI TS 24.501CR5012
- Indication of support for reconnection to the network due to RAN timing synchronization status change via the 5GMM capability IE TS 24.501CR5056
- 5GMM state for unavailability period TS 24.501CR5458
- Indicating Uplink data status IE considering multicast MBS session reception in 5GMM-CONNECTED mode with RRC inactive indication TS 24.501CR5321
+ 35 more changes
In Release 19, the 5GMM function introduced new capabilities for 5G ProSe multi-hop relays and IM relays, and defined specific handling for new 5GMM cause #83 (procedure cannot be completed due to unavailable feeder link). The release also included corrections and enhancements for handling 5GMM parameters during the eCall inactivity procedure and for timer management during transitions from RRC inactive to idle mode.
- Update 5GMM capability for 5G ProSe multi-hop relays TS 24.501CR6692
- Update 5GMM capability for IM relay TS 24.501CR6937
- Handling 5GMM parameters due to eCall inactivity procedure TS 24.301CR4272
- Correction to the handling of the 5GMM parameters in eCALL-INACTIVE state. TS 24.301CR4514
- 5GMM handling upon cause #83 TS 24.301CR4578
- FTAI list handling for extended 5GMM cause with cause #15 TS 24.501CR6728
+ 2 more changes
Explore further
Broader topics and technologies where 5GMM plays a role.
Defining Specifications
3GPP specifications that define or reference 5GMM, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 24.301 vj60 | NAS protocol for Evolved Packet System | Rel-19 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.890 vg00 | 5G NAS Protocol for 5GS Stage 3 | Rel-16 |
| TS 29.214 vj20 | Policy and Charging Control over Rx | Rel-19 |
| TS 38.508 vj11 | 5G NR UE Radio Transmission & Reception | Rel-19 |
