Improving Medium Frequency R-Mode Ranging with GMSK Modulation

Lars Grundhöfer, Filippo Giacomo Rizzi, Stefan Gewies, Michael Hoppe, Giovanni Del Galdo

Abstract: The R-Mode terrestrial navigation system evaluates the phase of two carriers next to a modulated signal, from which a range can be derived to allow positioning using different stations. To improve the accuracy of ranging, we propose in this paper to replace the currently used Minimum Shift Keying (MSK) modulation with Gaussian Minimum Shift Keying (GMSK). By applying a Gaussian pulse shape for the bit transition to that of the MSK a higher spectral efficiency is achieved. If the data rate is kept constant, this reduces the energy of the modulated signal within the bandwidth of the phase estimator. This increases the accuracy of the added carrier estimate and achieves our goal of improved distance-estimation accuracy. In this paper, we compare the estimates for an R-Mode signal with MSK and two different GMSK modulations. The increased accuracy is verified using software and hardware in-the-loop simulations.
Published in: Proceedings of the 34th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2021)
September 20 - 24, 2021
Union Station Hotel
St. Louis, Missouri
Pages: 3227 - 3233
Cite this article: Grundhöfer, Lars, Rizzi, Filippo Giacomo, Gewies, Stefan, Hoppe, Michael, Del Galdo, Giovanni, "Improving Medium Frequency R-Mode Ranging with GMSK Modulation," Proceedings of the 34th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2021), St. Louis, Missouri, September 2021, pp. 3227-3233.
https://doi.org/10.33012/2021.18092
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