Description
The European Geostationary Navigation Overlay Service (EGNOS) is a Satellite-Based Augmentation System (SBAS) developed by the European Space Agency, the European Commission, and Eurocontrol. While not a 3GPP-created technology, its support and integration are specified within 3GPP standards to enable location-based services in mobile networks. EGNOS enhances the performance of core Global Navigation Satellite Systems (GNSS) like GPS by providing correction data and integrity information.
Architecturally, EGNOS consists of a network of precisely surveyed ground reference stations (RIMS - Ranging and Integrity Monitoring Stations) spread across Europe. These stations continuously monitor the signals from GPS satellites. The collected data is sent to master control centers (MCCs) where errors (such as those caused by ionospheric delays, satellite clock drift, and ephemeris inaccuracies) are computed. These computed correction and integrity messages are then uploaded to geostationary satellites (GEO satellites) that broadcast them over the EGNOS service area.
A User Equipment (UE) with an EGNOS-enabled GNSS receiver receives both the standard GPS signals and the EGNOS augmentation signals from the GEO satellites. The receiver applies the correction data to the raw GPS measurements, significantly improving positional accuracy from about 10 meters (standalone GPS) to better than 1-2 meters horizontally. Crucially, EGNOS also provides integrity information, alerting the user within seconds if the GPS signal is unreliable or contains errors beyond safe limits for applications like aviation navigation. In the 3GPP context, this enhanced positioning data can be used by the UE or provided to the network via control plane or user plane location protocols (e.g., LPP, SUPL) to support advanced Location-Based Services (LBS).
Purpose & Motivation
EGNOS was created to address the limitations of standalone GPS for safety-of-life and other high-precision commercial applications in Europe. While GPS provides global coverage, its signals are susceptible to errors that degrade accuracy and, more importantly, lack a guaranteed integrity monitoring system. This made it unsuitable for critical phases of flight in aviation or for other applications where liability and safety are paramount.
The purpose of integrating EGNOS support into 3GPP standards (starting from Release 8) was to leverage this high-quality, certified positioning service for mobile applications. It enables network operators and service providers to offer more accurate and reliable location services. This solves problems such as providing enhanced 911 (E112) emergency caller location with better precision, enabling road tolling systems, precision agriculture, and supporting the evolving needs of intelligent transportation systems and IoT applications that depend on trustworthy positional data.
By specifying how UEs and networks can utilize EGNOS data, 3GPP allowed the mobile ecosystem to benefit from a publicly funded infrastructure that provides open, free, and certified augmentation signals, moving beyond the limitations of basic cell-ID or standalone GPS positioning available in earlier releases.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (34 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-8, normative work from Rel-15.
In Release 15, the update specifically concerned the provision of EGNOS assistance data via the OMA SUPL (Secure User Plane Location) protocol. This enhancement improved the delivery of European Geostationary Navigation Overlay Service correction information to user equipment. The change focused on refining the information elements within SUPL to support more accurate and reliable positioning services.
- Update of OMA SUPL information TS 38.305CR0011
In Release 16, the primary update for the EGNOS function within A-GNSS was the introduction of support for the B1C signal from the BDS (BeiDou) navigation system. This release also updated the associated B1I signal Interface Control Document (ICD) file to version 3.0. Furthermore, corrections and clarifications were made to user-plane positioning support by SUPL and to the technical specifications describing GNSS terms.
- Introduction of B1C signal in BDS system in A-GNSS TS 36.305CR0083
- Introduction of B1C signal in BDS system in A-GNSS TS 37.355CR0248
- Introducing support for GNSS Integer Ambiguity Level Indications TS 37.355CR0252
- Introduction of B1C signal in BDS system in A-GNSS TS 38.305CR0013
- Update B1I signal ICD file to v3.0 in BDS system in A-GNSS TS 36.305CR0088
- Correction on user-plane positioning support by SUPL TS 36.305CR0105
+ 6 more changes
In Release 17, the EGNOS-related function was enhanced with new capabilities for GNSS Positioning Integrity and high-accuracy location estimates. Specifically, the release introduced support for the B2a and B3I signals from the BDS system to improve integrity and added the delivery of NMEA GGA sentence information within high-accuracy GNSS location estimates. Furthermore, it included corrections and clarifications to the integrity bounds for GNSS orbits and clocks, the SSR BDS orbit ephemeris reference, and various field descriptions for tropospheric delay and other metrics.
- Introduction of B2a and B3I signal in BDS system and GNSS Positioning Integrity TS 36.305CR0107
- NMEA GGA sentence info in high accuracy GNSS location estimates [HA-GNSS-NMEA] TS 37.355CR0349
- Correction on the GNSS Orbit and Clock Integrity Bounds in TS 37.355 TS 37.355CR0377
- GNSS SSR BDS orbit emphemeris reference clarification to align with RTCM TS 37.355CR0461
- Field description correction for HA-GNSS metrics TS 37.355CR0474
- Correcting field description and definition of GNSS-SSR-URA TS 37.355CR0400
+ 2 more changes
In Release 18, the enhancements for the EGNOS function focused on refining A-GNSS positioning assistance data, including corrections to the support for GNSS almanac and UTC model parameters. The release also introduced and corrected assistance information for identifying Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) GNSS signal conditions to improve positioning accuracy. Additionally, editorial corrections were made to the specification's navigation data structure and descriptions for parameters like the Klobuchar model.
- GNSS LOS/NLOS assistance information [GNSS LOS/NLOS] TS 37.355CR0446
- Miscellaneous RIL corrections for GNSS LOS/NLOS [GNSS LOS/NLOS] TS 37.355CR0495
- Correction on GNSS-AlmanacSupport and GNSS-UTC-ModelSupport in A-GNSS positioning TS 37.355CR0518
- Correction on NavIC almanac set IE, and field descriptions under KlobucharModelParamater and GNSS-SystemTime. TS 37.355CR0534
- Editorial corrections to the navigation pane for 9.3.4 and 9.3.5 TS 38.455
In Release 19, the primary new development for the EGNOS function was the expansion of supported satellite systems for Assisted-GNSS (A-GNSS). Specifically, the release introduced support for the NavIC L1 SPS signal and the BDS B2b signal across key specifications, including the LTE and NR Stage 2 specifications as well as the LPP protocol. This continued the 3GPP trend of extending A-GNSS to include additional global navigation satellite systems beyond GPS.
- Introduction of NavIC L1 SPS A-GNSS in LTE Stage 2 specification TS 36.305CR0120
- Introduction of BDS B2b in A-GNSS TS 36.305CR0121
- Introduction of NavIC L1 SPS A-GNSS in LPP TS 37.355CR0532
- Introduction of B2b signal in BDS system in A-GNSS TS 37.355CR0545
- UE request for equalIntegerAmbiguityLevel assistance data [GNSS-EqualIntegerAmbiguity] TS 37.355CR0557
- Introduction of NavIC L1 SPS A-GNSS in NR Stage 2 specification TS 38.305CR0179
+ 2 more changes
Explore further
Broader topics and technologies where EGNOS plays a role.
Defining Specifications
3GPP specifications that define or reference EGNOS, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 22.071 vj00 | 3GPP TS 22.071: Location Services (LCS) Stage 1 | Rel-19 |
| TS 25.305 vj00 | UTRAN UE Positioning Stage 2 | Rel-19 |
| TS 25.306 vj00 | UE Radio Access Capabilities Specification | Rel-19 |
| TS 25.331 vj00 | UTRAN RRC Protocol Specification | Rel-19 |
| TS 25.423 vj00 | UTRAN RNSAP Specification | Rel-19 |
| TS 25.433 vj00 | Node B Application Part (NBAP) Protocol | Rel-19 |
| TS 25.453 vj00 | PCAP Protocol Specification | Rel-19 |
| TS 36.305 vj00 | UE Positioning in E-UTRAN Stage 2 | Rel-19 |
| TS 36.355 vj00 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TS 38.455 vj10 | NR Positioning Protocol A (NRPPa) | Rel-19 |
| TS 44.031 vj00 | Radio Resource LCS Protocol (RRLP) | Rel-19 |