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Session B2: Trends in GNSS Augmentation Systems

EGNOS V3 DFMC Demonstrator (EDD) — A Representative Live Simulation Capability for the Future EGNOS Services
Renaud Fabre, Thomas Fuhrmann, and Keerthi Narayana, Airbus Defence and Space

EGNOS is the European SBAS in charge of providing GNSS users with navigation corrections and an integrity service, broadcasted from geostationary (GEO) satellites.
Airbus Defense and Space, together with its key partners, is currently developing the second generation of EGNOS (EGNOS V3) for the European Space Agency (ESA) and for the European Union Agency for the Space Programme (EUSPA) [RD.1]. This new generation of European SBAS will operate on a multi-frequency (L1/L5, E1/E5) and multi-constellation basis (GPS, Galileo). Thus, EGNOS V3 will improve both GPS and Galileo performances, in order to provide satellite-positioning services to the most safety-critical applications such as aircraft navigation.
Thanks to the recent achievements of EGNOS V3 development funded by the European Union, Airbus has developed a representative EGNOS DFMC Demonstrator (EDD) using EGNOS V3 assets. Built on the powerful EGNOS V3 testbed framework, the EDD embeds the actual EGNOS V3 algorithms prototype to process signals collected in real-time from public GNSS receiver stations spread over Europe and generate the SBAS augmentation messages in compliance with the ICAO SARPs Annex 10 [RD-2] and receiver MOPS standard [RD-3].
This paper is structured in four parts: 1) EDD concept and architecture, 2) Receiver stations selection and performance analysis, 3) End-to-end SBAS performance results, 4) Conclusions and way forward

1) EDD concept and architecture
EDD is built re-using existing EGNOS V3 assets:
- SPV-P: System Performance Validation Platform
- PCF CAM: EGNOS V3 prediction chain CPF algorithmic models for
o Single-frequency enhanced mode (SF ENH) a specific EGNOS V3 configuration using both GAL and GPS to compute ionospheric delays correction.
o Dual-frequency multi-constellation mode (DFMC)
- PEACE: Performance Analysis tool suite
The real-time data collection is established using publicly available data streams from GNSS receiver stations forming part of the IGS and EUREF networks.
The logical workflow of EDD starts with GNSS data (Galileo and GPS observables) collection by SPV-P from IGS NTRIP casters in near real-time. The SPV-P is in charge of scheduling and feeding data to the EGNOS V3 prediction chain which generates the EGNOS V3 SBAS messages. The EGNOS V3 SBAS messages are recorded in EMS format and the end-to-end performance is then analyzed and displayed through PEACE, the EGNOS V3 performance analysis tool suite.

2) Receiver stations selection and performance analysis
To select the public GNSS receiver stations from which the GNSS data is collected, several requirements had to be met. The first was to maximize the representativeness of the future service, therefore the selected station network should mimic as much as possible the EGNOS V3 stations network with regards to number and locations of stations. Secondly, the stations had to be able to provide both GPS and Galileo observations through a live caster, to deliver high-rate data (1 Hz) with no or very few data gaps. And finally, the overall performance of the selected stations shall be good according to several key performance indicators (KPI) discussed below.
After a first candidate selection step, a full performance analysis of the candidate stations was conducted based on statistics provided by EPN website allowing to deliver a weighted score to each of the candidate stations based on the following KPIs: Clock type, percentage of observed versus expected observations, number of missing EPOCHs, number of Cycle Slips, and multipath level. Secondly, candidate stations data has been analyzed with TEQC software to both confirm the EPN statistics and detect any data gaps greater than 2s. Finally, candidate stations data have been analyzed using the Bernese GNSS software to provide detailed insight on receiver clock performances through elaboration of Allan deviation plots for each station as well to estimate the accurate station coordinates required as an input for the EDD data processing.
Through all these steps, the amount of candidate stations has reduced from 153 stations to 35 stations on the final selection, close to the amount of EGNOS RIMS (Ranging and Integrity Monitoring Stations) currently operational (38).

3) Performance results
Several simulations have been run producing in parallel two different SBAS messages compliant with MOPS standards [RD-3], one representative of the future EGNOS V3.1 system capabilities (L1 SBAS, Single Frequency Enhanced Mode), one representative of future EGNOS V3.2 system capabilities (L5 SBAS, Dual Frequency Multi Constellation). For each of the produced SBAS messages a performance analysis supported by the PEACE tool allowed to measure existing and future SBAS services (NPA, APV-I, CAT-I/LPV-200 (Vertical Alert Limit VAL=35m), CAT I (VAL=10m)) in the EGNOS service area (dashed black line in Figure 3).
A very promising level of service performance has been obtained with this first live demonstration of DFMC capabilities over Europe. The sample of results shown in Figure 3 reflects the LPV-200 service availability over a 24-hour period in the EGNOS service area, but using public GNSS stations as the EGNOS V3 RIMS stations are not yet fully deployed, so the performances displayed are not representative in that terms.

4) Conclusion and way forward
Thanks to this flexible and agile EDD platform and to this successful first live demonstration of DFMC future service capabilities above Europe, we open the door to future experimentations to support EU users’ community in DFMC adoption, but as well to support new services experimentation and system evolutions over other geographical area experiments. A first DFMC message dissemination through signal in space above EGNOS service area is foreseen Q3 2024 thanks to EDD.
Acknowledgments
Part of this work has been carried out with the funding of the European Union. Any reproduction total or partial of this work shall acknowledge that it has been carried out with the funding of the European Union.
Disclaimer
The views expressed herein can in no way be taken to reflect the official opinion of the European Union, the EU Agency for the Space Programme or the authors' organizations. Any reproduction total or partial of this work shall include this disclaimer.
[RD-1]: European GNSS Agency, “Airbus awarded EGNOS V3 contract”, February 2018.
https://www.gsa.europa.eu/newsroom/news/airbus-awarded-egnos-V3-contract
[RD-2]: ICAO Annex 10 Vol1, “Standards and Recommended Practices and guidance material for the global navigation satellite system (GNSS)”
https://store.icao.int/en/annex-10-aeronautical-telecommunications-volume-i-radio-navigational-aids
[RD-3]: ED-259 - Minimum Operational Performance Standard for Dual-Frequency Multi-Constellation Satellite-Based Augmentation System Airborne Equipment
https://eshop.eurocae.net/eurocae-documents-and-reports/ed-259a/



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