Performance Evaluation of the Ionospheric Threat Mitigation Strategies in Dual-Frequency Multi-Constellation GBAS

Maria Caamano, Daniel Gerbeth, Hiroatsu Sato, Mihaela-Simona Circiu, Michael Felux

Abstract:	Abstract—In this paper, we evaluate the performance of the dual-frequency airborne ionospheric gradient monitor proposed for dual-frequency multi-constellation (DFMC) Ground Based Augmentation Systems (GBAS) at different distances from the airport. We use two types of thresholds for this assessment: (i) a constant threshold derived from operational requirements, and (ii) a dynamic threshold that increases with the distance from the airport. Increasing the threshold allows more ionospheric error within the position solution, but also enables the use of the primary single-frequency modes without the need to switch to the ionosphere-free (Ifree) solution for a longer period, which generally degrades the performance because it combines the noise and multipath of two frequencies. Furthermore, we compare the performance of the two potential architectures for DFMC GBAS: (i) the so-called GAST F architecture, which is based on single-frequency 100 seconds smoothing, and (ii) the GAST X architecture, which is based on divergence-free (Dfree) smoothing with variable and potentially longer smoothing time constants. Results with both simulated and real data show that the use of a variable threshold significantly reduces the probability of excluding satellites and switching to the Ifree mode for both GAST F and X, thereby increasing the availability of GBAS. Index Terms—Dual-frequency multi-constellation GBAS, ionospheric monitoring, availability, integrity, anomalous ionospheric gradients
Published in:	2023 IEEE/ION Position, Location and Navigation Symposium (PLANS) April 24 - 27, 2023 Hyatt Regency Hotel Monterey, CA
Pages:	196 - 207
Cite this article:	Caamano, Maria, Gerbeth, Daniel, Sato, Hiroatsu, Circiu, Mihaela-Simona, Felux, Michael, "Performance Evaluation of the Ionospheric Threat Mitigation Strategies in Dual-Frequency Multi-Constellation GBAS," 2023 IEEE/ION Position, Location and Navigation Symposium (PLANS), Monterey, CA, April 2023, pp. 196-207. https://doi.org/10.1109/PLANS53410.2023.10140062
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