Utilization of Full-Resolution Ground Code and Carrier-Phase Measurements in DFMC GBAS (GAST E)

Susumu Saito, Mutaz Tuffaha, Morten Topland, Linda Lavik, Tim Murphy, Gary McGraw, Joel Wichgers

Abstract:	Standards of the Dual-Frequency and Multi-Constellation (DFMC) Ground-based Augmentation System (GBAS) using the GNSS signals at L1 and L5 frequencies which is called GAST E are under development at International Civil Aviation Organization (ICAO). For GAST E, code and carrier-phase measurements made by the GBAS ground reference receivers are being designed to be uplinked. However, due to limited bandwidth of VHF data broadcast (VDB), effective data compression and reconstruction protocols are necessary. At the same time, simplicity and robustness are important. It is also necessary to be able to support future extended services based on GAST E, such as carrier-phase-based applications. We developed a set of protocols for GAST E to send code pseudo-range and carrier-phase measurements of the ground reference receivers to aircraft in the MT-23. It can accommodate 16 satellites in one MT-23 which is sufficient to support Category-II/III operations. The procedure to compress and reconstruct ground measurements are straight forward, deterministic, and each MT-23 is independent of other MT-23s at different epochs. This gives strong robustness against missed VDB messages. We showed that the reconstructed measurements including the code pseudo-ranges and carrier-phases can be used for code-based and carrier-based positioning just as the original measurements. The proposed MT-23 and related protocols are promising candidates for GAST E.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	250 - 262
Cite this article:	Saito, Susumu, Tuffaha, Mutaz, Topland, Morten, Lavik, Linda, Murphy, Tim, McGraw, Gary, Wichgers, Joel, "Utilization of Full-Resolution Ground Code and Carrier-Phase Measurements in DFMC GBAS (GAST E)," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 250-262. https://doi.org/10.33012/2025.20301
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In