Validation of the RTCA Message Format for WAAS

Yeou-Jyh Tsai, Per Enge, Yi-Chung Chao, Todd Walter, Changdon Kee, Jennifer Evans, Andrew Barrows, David Powell, and Bradford Parkinson

Abstract:	The Wide Area Augmentation System (WAAS) will augment GPS by broadcasting: - additional ranging signals from geostationary satellites. - integrity data for each satellite - multiple-component differential corrections for each satellite The ranging function will improve the availability and reliability of the position fix; the integrity data will improve the safety of the fix; and the differential GPS corrections will provide non-precision and Category I precision approach capability. The WAAS data format was designed by Working Group 2 of RTCA Special Committee 159, and is gaining wide acceptance as the standard for WAAS transmissions. This remarkable format allows for the broadcast of differential corrections and integrity data on the GPS-like ranging signal. As such, it must pack this data into 250 bits/second, because higher data rates would require higher signal powers which might interfere with GPS. This paper is the first to report on a nearly full implementation of the RTCA data format. It is baaed on the experimental WAAS flight system maintained by Stanford University for the FAA. The paper describes the separation of the error components, message scheduling and packing, and flight results.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	661 - 670
Cite this article:	Tsai, Yeou-Jyh, Enge, Per, Chao, Yi-Chung, Walter, Todd, Kee, Changdon, Evans, Jennifer, Barrows, Andrew, Powell, David, Parkinson, Bradford, "Validation of the RTCA Message Format for WAAS," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 661-670.
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