WAAS Signal Deformation Monitor Performance: Beyond the ICAO Threat Model

R. Eric Phelts, Karl Shallberg, Todd Walter and Per Enge

Peer Reviewed

Abstract:	Over nearly 20 years, signal deformation monitoring implementations and research have advanced significantly. Both nominal and anomalous deformations have since been measured on numerous SVs, and sophisticated SBAS and GBAS monitoring algorithms have been exposed to them in real-time. Because of this, the accepted way of modeling signal deformation anomalies—i.e., the ICAO 2nd-Order Step model (with Dead Zones)—has itself come under greater scrutiny. Its continued ability to ensure that existing integrity monitors (previously designed using only that model) can protect against real-world signal deformation threats has yet to be re-assessed. In addition, little has been done to analyze monitor performance against threats outside the original threat model parameter limits. This paper proposes to assess the current WAAS signal quality monitor algorithm performance against several different kinds of deformation threats. First, it describes three alternative threat model—each extensions of the standard ICAO model, and each designed to more-accurately model past, real-world faults and nominal signal distortions. These alternate threat models include an extended range of standard 2 nd-order step parameters, an amplitude-modulated 2 nd-order model, and a single-reflection (multipath) model. The WAAS signal quality monitor is validated against each of these. It is shown that the existing WAAS monitor implementation is very capable of detecting many signal deformation threats not previously captured by the standard threat model, despite not having been specifically designed to mitigate them.
Published in:	Proceedings of the ION 2017 Pacific PNT Meeting May 1 - 4, 2017 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	713 - 724
Cite this article:	Phelts, R. Eric, Shallberg, Karl, Walter, Todd, Enge, Per, "WAAS Signal Deformation Monitor Performance: Beyond the ICAO Threat Model," Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, Hawaii, May 2017, pp. 713-724. https://doi.org/10.33012/2017.15103
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