Performance Analysis of GNSS Global and Regional Integrity Concepts

H. Blomenhofer, W. Ehret, E. Blomenhofer

Abstract:	GPS and Galileo are expected to serve as navigation sources for a variety of applications. The most stringent performance requirements are derived from safety critical applications including aviation APV-II respectively CAT-I precision operations. The Galileo baseline architecture specifies a global integrity concept. This means e.g. that besides the accuracy, availability and continuity the specified integrity performance must be achieved on a global level. However Civil Aviation Authorities outside Europe, might wish due to sovereignty reasons as well as due to performance reasons to determine the System Integrity of Galileo independently. One concept would be to adapt the different Augmentation approaches for GPS (SBAS, GBAS, GRAS) for the Galileo case. However, the Galileo baseline already foresees to include a multi-regional integrity concept where regions can install own integrity determination architecture while Galileo will provide the interfaces from regions to the Galileo satellites for disseminating of the regionally determined integrity. The basic approach of the Galileo integrity concept hereby is the task split of the Galileo integrity monitoring between the System (providing the GNSS Integrity Channel) and the User (providing Receiver Autonomous Integrity Monitoring techniques). The system performance has to be achieved in terms of the specified accuracy, availability and continuity figures. In addition the integrity monitoring has to detect Hazardously Misleading Information (HMI) of the navigation system and to alert the users within the specified Time To Alert (TTA). The Galileo System shall provide timely warning if the errors caused by satellite, clock, signal and / or navigation message are larger than predicted via a combination of a Signal In Space Accuracy (SISA) and Integrity Flag (IF). The SISA is a quantitative estimation of the orbit and clock prediction of the Galileo Control Centre which is updated with every clock update - in a fault free case. If an error occurs in the satellites, clocks, signal, navigation message or in the processing itself, then it has to be detected by the Integrity Processing Facility (IPF) in real-time and a warning flag IF has to be sent to the user within the necessary Time-to-Alert. As the check in the IPF has to be performed nearly instantaneous (fraction of the Time to Alert), there has to be a sufficient number of Sensor Stations to get a statistically significant test, which allows even to identify and to exclude Sensor Stations with local disturbances in the observations. The main design driver of the Galileo architecture is the IF performance. This paper compares the Galileo global integrity concepts with a regional approach using different concepts and IF algorithms but also different ground architectures.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	991 - 1001
Cite this article:	Blomenhofer, H., Ehret, W., Blomenhofer, E., "Performance Analysis of GNSS Global and Regional Integrity Concepts," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 991-1001.
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