Range Biases on the WAAS Geostationary Satellites

R. Eric Phelts, Todd Walter, Per Enge, Dennis M. Akos, Karl Shallberg, and Tom Morrissey

Abstract:	Due to limited receiver bandwidth and tracking configuration differences, measurements made on a narrowband geostationary satellite signal may differ significantly from those made on GPS signals and result in relatively large range bias errors for users. Modeling and analysis of this net effect is complicated by several parameters including a wide range of allowed GEO signal correlator spacings (relative to GPS for both the reference and user receivers). Further, the differential group delays of the reference receivers, user receivers, and GEO signal itself play a significant role in the magnitude of this effect. The result is that a narrowband GEO signal appears distorted relative to wideband GPS signals. This paper describes the history and identification of the GEO bias problem in WAAS and its current remedy. The paper models several filters and identifies the differential group delay as the key cause of this distortion. It then analyzes the effects of differential group delay on correlation functions and provides supporting analysis using actual filter models and live signal data processed in real GPS receivers. Finally, this paper provides estimates on ranging performance for future (wideband) GEOs and offers recommendations on receiver configurations designed to minimize this bias error.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	110 - 120
Cite this article:	Phelts, R. Eric, Walter, Todd, Enge, Per, Akos, Dennis M., Shallberg, Karl, Morrissey, Tom, "Range Biases on the WAAS Geostationary Satellites," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 110-120.
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