Title: Mitigation of Nominal Signal Deformations on Dual-Frequency WAAS Position Errors
Author(s): Gabriel Wong, Yu-Hsuan Chen, R. Eric Phelts, Todd Walter, Per Enge
Published in: Proceedings of the 27th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2014)
September 8 - 12, 2014
Tampa Convention Center
Tampa, Florida
Pages: 3129 - 3147
Cite this article: Wong, Gabriel, Chen, Yu-Hsuan, Phelts, R. Eric, Walter, Todd, Enge, Per, "Mitigation of Nominal Signal Deformations on Dual-Frequency WAAS Position Errors," Proceedings of the 27th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 3129-3147.
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Abstract: Global Navigation Satellite Systems (GNSS) are used in a wide variety of applications, some critical, many essential. They are steadily being improved with the addition of new constellations, new frequencies, and new signals. Future multi-frequency GNSS will eliminate one of the largest error sources (ionospheric delays) and promises even better performance. Unfortunately, the new frequencies and signals will have small but unavoidable biases relative to one another. These nominal satellite signal deformations – deviations of broadcast satellite signals from ideal – result in tracking errors, range biases, and position errors in GPS receivers. The impact of these biases increases as other error sources are eliminated. Left unquantified and unmitigated, future performance may be limited by these biases. Thus it is imperative to measure, characterize, and mitigate them. An effective “measure-and-verify” measurement technique for signal deformation biases was previously demonstrated by the author and collaborators for L1-frequency signals [15]. This two-stage process produced highly-consistent measurements, thus rendering signal deformation biases observable and measurable. This measurement method is applied to obtain signal deformation bias measurements for 3 of the recent Block IIF dual-frequency L1/L5 satellites. These dual-frequency measurements are subsequently used to validate past projections of dual-frequency L1/L5 biases from single-frequency L1-only biases. In turn, this allows accurate estimations of expected and worst case 2 position errors for dual-frequency L1/L5 positioning in the presence of unmitigated signal deformation biases. Finally, using the “measure-and-verify” technique, a proposed strategy is demonstrated to be highly effective: narrowing the space of allowed user-receiver correlator spacings. Use of this strategy mitigates the signal deformation biases and resultant position errors, allowing dual-frequency users to reap the performance benefits of ionospheric error removal without significant limitations caused by signal deformation biases.