Description
The Generic Public Subscription Identifier (GPSI) is a critical identifier in the 5G System (5GS) defined in 3GPP TS 23.501. It serves as a public-facing, globally unique address for a subscription, used by external Application Functions (AFs) and within the network to reference a user. There are two primary formats: an MSISDN (Mobile Subscriber Integrated Services Digital Network Number), which is a telephone number in E.164 format, and an External Identifier, which is a string formatted as 'username@realm'. The GPSI is stored in the Unified Data Management (UDM) as part of the subscription data and is associated with the SUPI (Subscription Permanent Identifier). Its key role is in service exposure via the Network Exposure Function (NEF) and in edge computing scenarios. When an external AF needs to interact with the network for a specific user (e.g., to influence traffic routing for low-latency applications), it uses the user's GPSI in its requests to the NEF. The NEF then translates this public GPSI into the internal SUPI for network operations, ensuring privacy. The GPSI is also used in UE policy configuration, SMS over NAS, and as a parameter in the Nnef_ services. Its handling involves strict privacy measures; for example, the GPSI is not used over the radio interface and is mapped to the SUPI within the secure core network domain.
Purpose & Motivation
GPSI was introduced in 5GS to fulfill the need for a stable, public, and user-friendly identifier that can be used by third-party application providers and within network service APIs, decoupling service addressing from internal network identifiers. Previous systems used MSISDN for this purpose, but this tied services to a specific numbering format (E.164) and was less flexible for non-telephony services or users without a phone number. The GPSI, with its support for both MSISDN and External Identifier (like an email address), solves this problem by providing a generic scheme. This is essential for 5G's service-based architecture and edge computing, where external applications need a consistent way to identify subscribers without being aware of their private SUPI or temporary 5G-GUTI. It addresses the limitations of using internal identifiers externally (a privacy and security risk) and the inflexibility of relying solely on MSISDN, enabling new business models and seamless integration with internet-based services and identity federations.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (20 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the GPSI was newly introduced as a replacement for the PUI (Private User Identifier) and was specifically added for use within the N5 interface. The release also included corrections to the regular expression pattern defining the GPSI format and enabled the sending of a GPSI in the form of an MSISDN during the procedure for initial spending limit retrieval.
In Release 17, the GPSI was enhanced to support new functions for UAV (Unmanned Aerial Vehicle) service integration, specifically for C2 (Command and Control) operation mode management. The updates included using the GPSI alongside a CAA-level UAV ID as a key identifier for UAS (Unmanned Aircraft System) procedures, such as USS (UAS Service Supplier) change authorization and Multi-USS policy management configuration. Furthermore, Release 17 introduced mechanisms for Event Exposure subscription revocation due to the removal of a GPSI and updated the BSF (Binding Support Function) NF (Network Function) profile to support both SUPI and GPSI.
In Release 18, the GPSI function was enhanced with new capabilities for mapping to Application Layer IDs and for supporting location services. Specifically, it introduced a procedure for GPSI to subscription network resolution using the NRF and added GPSI support to the 5GC-MT-LR procedure without requiring a UDM query. Furthermore, support for GPSI was extended to related UEs within the GMLC API.
- Add GPSI and Application Layer ID mapping information TS 29.519CR0490
- Updates to GPSI and Application Layer ID mapping information TS 29.519CR0513
- Including GPSI attribute support TS 29.535CR0037
- Add GPSI and Application Layer ID mapping information TS 29.591CR0173
- Delimiting the GPSI values to be fetched to UDM TS 29.503CR1242
- GPSI and SUPI Support for Related UEs in GMLC API TS 29.515CR0145
+ 2 more changes
In Release 19, the GPSI function was enhanced to support the association of multiple SUPIs to a single GPSI within the UDM. It also introduced the capability for an Application Function to generate AF-specific GPSIs and enabled new query procedures for GPSI/PEI-based identity associations. Furthermore, the scope of GPSI usage was clarified by addressing its omission from specific IEF event reporting parameters.
Explore further
Broader topics and technologies where GPSI plays a role.
Defining Specifications
3GPP specifications that define or reference GPSI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.255 vj50 | UAS Application Layer Support | Rel-19 |
| TS 23.286 vj00 | V2X Application Enabler Architecture | Rel-19 |
| TS 23.434 vk00 | Service Enabler Architecture for Verticals | Rel-20 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.540 vj20 | 5G Service Based SMS Stage 2 | Rel-19 |
| TS 23.558 vk00 | Architecture for Edge Applications | Rel-20 |
| TR 23.758 vh00 | Study on Edge Application Architecture | Rel-17 |
| TS 24.257 vj40 | UAS Application Enabler (UAE) Layer | Rel-19 |
| TS 24.583 vj00 | Application Layer Support for Personal IoT Network | Rel-19 |
| TS 26.510 vj10 | Media Delivery APIs for 5GMS and RTC Systems | Rel-19 |
| TS 26.512 vj10 | 5G Media Streaming Protocols & APIs | Rel-19 |
| TS 28.204 vi11 | Charging management | Rel-18 |
| TR 28.840 vi10 | Technical Report | Rel-18 |
| TS 29.503 vj50 | UDM Service Based Interface Stage 3 | Rel-19 |
| TS 29.504 vj50 | Nudr Service Based Interface Stage 3 Protocol | Rel-19 |
| TS 29.505 vj50 | UDR Service for Subscription Data Usage | Rel-19 |
| TS 29.507 vj40 | 5G Access & Mobility Policy Control Service | Rel-19 |
| TS 29.508 vj40 | 5G Session Management Event Exposure Service | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 29.515 vj50 | Ngmlc Service Based Interface Protocol | Rel-19 |
| TS 29.517 vj40 | 5G AF Event Exposure Service Stage 3 | Rel-19 |
| TS 29.518 vj50 | AMF Service Based Interface Protocol | Rel-19 |
| TS 29.519 vj40 | UDR Usage for Policy & Exposure Data | Rel-19 |
| TS 29.521 vj40 | 5G Binding Support Management Service Stage 3 | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 29.523 vj20 | 5G Policy Control Event Exposure Service | Rel-19 |
| TS 29.525 vj40 | 5G UE Policy Control Service Stage 3 | Rel-19 |
| TS 29.530 vj00 | AF AI/ML Services Stage 3 Protocol | Rel-19 |
| TS 29.535 vj40 | 5G AKMA Anchor Services Stage 3 Protocol | Rel-19 |
| TS 29.558 vj40 | Enabling Edge Applications | Rel-19 |
| TS 29.561 vj30 | 5G Interworking with External Data Networks | Rel-19 |
| TS 29.562 vj40 | HSS Services for IMS & GBA Interworking | Rel-19 |
| TS 29.571 vj50 | Common Data Types for 5G Service Based Interfaces | Rel-19 |
| TS 29.591 vj40 | 5G NEF Southbound Services Stage 3 | Rel-19 |
| TS 29.594 vj20 | 5G Spending Limit Control Service Stage 3 | Rel-19 |
| TR 29.829 vh10 | SMS Service-Based Interfaces for 5G Core | Rel-17 |
| TS 29.890 vg00 | CT3 5G System Technical Report | Rel-16 |
| TS 32.255 vk10 | Telecom Management; Charging for 5G Data Connectivity | Rel-20 |
| TS 32.256 vj40 | 5G Connection & Mobility Charging Spec | Rel-19 |
| TS 32.291 vj40 | Charging Management: Service-Based Interface Protocol | Rel-19 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TR 33.739 vi10 | Study on security enhancement of support for | Rel-18 |
| TS 33.749 vj00 | Study on security aspects of edge computing enhancement | Rel-19 |
| TS 33.835 vg10 | Study on authentication and key management for apps | Rel-16 |
| TR 33.867 vh10 | User Consent for 3GPP Services | Rel-17 |
| TS 38.473 vj10 | 5G F1 Application Protocol (F1AP) | Rel-19 |
