Satellite-Based Augmentation System Signal-In-Space Integrity Performance Analysis, Experience, and Perspectives

Donghai Dai, Todd Walter, Per Enge, and J. David Powell

Abstract:	The Federal Aviation Administration (FAA) is pioneering a transformation of the national airspace system from its present ground based navigation and landing system to a satellite-based system using the Global Positioning System (GPS). To meet the critical safety-of-life aviation positioning requirements, a Satellite-Based Augmentation System (SBAS) known as the Wide Area Augmentation System (WAAS) will be implemented to support navigation for all phases of flight from oceanic through Category I precision approaches. The WAAS will provide its users with integrity information, vector differential corrections and corresponding confidence intervals through ranging capable geostationary satellites. Providing wide area availability of precision approach is the most challenging design feature of WAAS. Integrity and safety are the paramount issues in evaluating the SBAS overall service quality. First, a WAAS integrity risk analysis leads to a system level characterization of the SBAS integrity architecture. Analysis illustrates that the most critical challenges of the WAAS total system integrity function include: the ground control stations' ability to guarantee SIS integrity, and the integrity of the airborne navigation system. This study will focus on the statistical characterization of the WAAS signal-in-space (SIS) integrity function, which is fundametally rooted in two aspects: integrity of accuracy and the ability to satisfy the strict time-to-alarm requirements. The theoretical framework of statistical hypothesis testing is generalized to the analysis of the system integrity of accuracy, specifically the vector correction confidence intervals, known as user differential range error (UDRE) and grid ionosphere vertical error (GIVE) algorithms. Meanwhile, interoperability between worldwide independent SBASs is desirable to achieve seamless global aviation systems. The integrity issue inevitable becomes one of the most critical factors for interoperation and is investigated in depth based on the previous analysis. Different interoperation scenarios will be investigated and tested using NSTB live data. Recommended interoperation scenarios will be identified for future cooperative efforts to achieve seamless worldwide navigation services. Quantitative characterization of the system SIS integrity function is achieved and verified through analyses, simulation and National Satellite Test Bed (NSTB) live data.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	159 - 179
Cite this article:	Dai, Donghai, Walter, Todd, Enge, Per, Powell, J. David, "Satellite-Based Augmentation System Signal-In-Space Integrity Performance Analysis, Experience, and Perspectives," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 159-179.
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