Description
Universal Geographical Area Description (GAD) is a fundamental concept within 3GPP specifications that provides a standardized method for describing geographical areas. It is not a single protocol but a set of definitions and encodings used across various network interfaces and applications. GAD defines how geographical information—such as points, ellipsoid points, polygons, and ellipsoid arcs—is structured and communicated. This structured description allows network entities and user equipment to unambiguously interpret location-related data.
The architecture of GAD is embedded within the broader location services (LCS) framework of 3GPP. It is utilized in signaling messages between core network nodes, such as the Gateway Mobile Location Centre (GMLC) and the Mobile Switching Centre (MSC), as well as in protocols like the Mobile Application Part (MAP) and Diameter. The GAD format includes parameters for shape, coordinates, and uncertainty, enabling precise or approximate area definitions depending on the service requirement. For instance, it can describe a cell coverage area, a predefined geofence, or a target region for location-based alerts.
Key components of GAD include the shape type (e.g., ellipsoid point, polygon), the geographical coordinates (typically using the World Geodetic System 1984, WGS84), and associated uncertainty or confidence levels. These components are encoded according to ASN.1 rules specified in 3GPP technical specifications. The role of GAD is critical for enabling services like emergency caller location, location-based charging, fleet management, and enhanced 911 (E911). By providing a universal format, it ensures interoperability between different network elements and across different generations of mobile networks, from GSM to 5G.
Purpose & Motivation
GAD was created to solve the problem of inconsistent and proprietary geographical descriptions in early mobile networks. Before standardization, vendors and operators used ad-hoc methods to define areas, leading to interoperability issues and hindering the rollout of location-based services. The need for a universal format became pressing with regulatory requirements for emergency services (e.g., E112 in Europe) and the commercial potential of location-aware applications.
The historical context lies in the evolution of GSM into 3G, where location services became a mandated feature. GAD, introduced in Release 4, provided a common language that allowed network equipment from different manufacturers to exchange geographical information seamlessly. It addressed limitations such as the inability to precisely define complex geographical zones or to convey uncertainty in location estimates. By standardizing the description, GAD enabled the development of a wide range of services that rely on accurate and interpretable area definitions, from navigation aids to geofencing for IoT devices.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (52 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-4, normative work from Rel-15.
In Release 15, the primary new introduction for the GAD function was the specification of high-accuracy GAD shapes, including a high-accuracy ellipsoid point with an uncertainty ellipse and a high-accuracy ellipsoid point with altitude and an uncertainty ellipsoid. These new shape descriptions provide enhanced precision for location data by defining more granular latitude, longitude, and altitude encoding. This enhancement supports the requirements for high-accuracy positioning services within the 5GS framework.
In Release 16, the GAD (Universal Geographical Area Description) function was enhanced by adding corresponding OpenAPI descriptions in clause 5.1. Furthermore, the release introduced GMLC authorization procedures within the RequestPosInfo service operation.
In Release 17, the key enhancement for the Universal Geographical Area Description (GAD) function was the introduction of a new high-accuracy GAD shape with scalable uncertainty, specifically defined for use with local coordinates. This builds upon the existing framework of shapes like the ellipsoid point with uncertainty ellipse by providing enhanced precision. Additionally, the release included corrections and clarifications to the description fields within the relevant OpenAPI service descriptions, such as those for the Namf_Location and Namf_EventExposure service APIs.
- Schedule location time for GMLC TS 29.515CR0072
- GMLC using AMF event exposure service TS 29.518CR0530
- Namf_MBSCommnuication service description TS 29.518CR0608
- GAD shape for location estimate in Local Coordinates TS 23.032CR0018
- Data Types Descriptions TS 29.515CR0047
- Data Type Description for Namf_MT Service API TS 29.518CR0518
+ 11 more changes
In Release 18, the GAD function was enhanced by introducing the NWDAF as a new service consumer for the GMLC and by adding the previously missing interface between the LMF and GMLC. The release also introduced capabilities for local LMF and GMLC selection and expanded support for GPSI and SUPI identifiers for related UEs within the GMLC API. Furthermore, procedural and descriptive corrections were made, including updates to the EventNotify service and refinements to parameters like `scheduledLocTime`.
- Add NWDAF as GMLC service consumer TS 29.515CR0100
- Addition of missing interface between LMF and GMLC TS 29.515CR0127
- Local LMF and GMLC selection TS 29.518CR0845
- Location header description TS 29.515CR0097
- Correction on the description of scheduledLocTime TS 29.515CR0128
- GPSI and SUPI Support for Related UEs in GMLC API TS 29.515CR0145
+ 12 more changes
In Release 19, updates to the GAD function focused on refining the technical descriptions within the specification to improve clarity and alignment. This included correcting and completing the descriptions of re-used data types, such as those for ellipsoid points and polygons, and addressing missing or incorrect descriptions in service APIs. The changes also involved clarifying the descriptions of conditional attributes and aligning event descriptions with other 3GPP working groups.
- Adding a new AMF service description TS 29.518CR1194
- Update the description of correlation Id TS 29.518CR1256
- Add description for ENUM data type TS 29.515CR0204
- Correct the description of some conditional attributes TS 29.515CR0207
- Missing descriptions in Namf_Location API TS 29.518CR1100
- Correct the Description of AIoT Service TS 29.518CR1226
+ 5 more changes
Explore further
Broader topics and technologies where GAD plays a role.
Defining Specifications
3GPP specifications that define or reference GAD, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.032 vj00 | Universal Geographical Area Description | Rel-19 |
| TS 24.080 vj20 | Mobile radio interface layer 3 supplementary services | Rel-19 |
| TS 29.515 vj50 | Ngmlc Service Based Interface Protocol | Rel-19 |
| TS 29.518 vj50 | AMF Service Based Interface Protocol | Rel-19 |
| TS 43.318 vj00 | Generic Access Network (GAN) Stage 2 | Rel-19 |