Interoperation and Integration of Satellite Based Augmentation Systems

Richard Fuller, Donghai Dai, Todd Walter, Christopher Comp, Per Enge, J. David Powell

Abstract:	In recent years there has been widespread growth in the independent development of Satellite Based Augmenta-tion Systems (SBASs). The Federal Aviation Admini-stration’s Wide Area Augmentation System (WAAS) will be the first of multiple systems to become operational in the near future. Of current interest is interoperability of these physically separate, independent SBASs. In par-ticular, designers are investigating the type, amount, and methodology of information shared between systems. There are interface issues related to a user passing from one SBAS to another. Among these is the degradation of the ephemeris and clock integrity bounds for users oper-ating outside of the SBAS network of reference stations. While some degradation in performance and integrity limits can be expected, it is shown that the ability to verify the quantity of error can deteriorate very rapidly. Both geometric and dynamic ephemeris estimates will suffer this increase in uncertainty due to dramatic decreases in GPS satellite observability. The effect of adding periph-ery stations to reduce this degradation is demonstrated through use of the National Satellite Test Bed (NSTB) network. Distributed systems have the ability to provide comple-mentary and cooperative data while retaining specific lev-els of independence. This extends as well to worldwide interoperability of continuous navigation services and in the standardization of international aviation navigation aids. A risk/benefit analysis of SBAS interoperability is presented. The analysis presents strategies of information integration that optimizes overall user integrity for the typical SBAS architecture by monitoring data sent from systems external to the SBAS. The performance of this integrity monitoring is characterized. The conceptual distributed design is supported by results from the NSTB network.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	121 - 130
Cite this article:	Fuller, Richard, Dai, Donghai, Walter, Todd, Comp, Christopher, Enge, Per, Powell, J. David, "Interoperation and Integration of Satellite Based Augmentation Systems," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 121-130.
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