A Comparative Study of LEO-PNT Systems and Concepts

Bernd Eissfeller, Thomas Pany, Dominik Dötterböck, and Roger Förstner

Abstract:	Currently, about ten dedicated LEO-PNT activities are under way on a worldwide basis. The SOOP (signals-of-opportunity) research within existing mega-constellations and plans for LEO-PNT research satellites are left out of consideration here. Thus, we observe a kind of hype and euphoria for LEO-PNT. However, shortcomings, contradictions and risks in several system designs are observed. In particular, many system designers underrate user segment aspects. In the paper we try to analyze the advantages and disadvantages of the proposed concepts, and to consider the most reasonable and realistic approach for LEO-PNT in a trade-off. We perform systematic assessments of the technical & non-technical characteristics of the LEO-PNT concepts: Orbit and constellation, carrier frequency, bandwidth and signal power issues, atmospheric (rain) and foliage attenuation and C/N0 as function of carrier-frequency (UHF to Ku-Band). Additionally, satellite platform issues (dedicated satellite versus hosted payload), payload technology and SWAP-budgets, LEO satellite classes are considered. We expect that a LEO payload will also show code- and phase bias delays in the individual satellite signals (not different from MEO). If this is the case and calibration does not solve the bias issue with required precision, PPP – corrections have to be determined for each LEO-PNT satellite. This has an impact on the complexity of the GSEC (ground segment) of LEO-PNT, because a large number of reference stations and up-load stations will be required based on the visibility constraint of the LEO orbit. The requirement on bias-free pseudorange and carrier-phase LEO-PNT measurements gets very stringent in the case that integer ambiguities have to be resolved for high accuracy and safety critical user segments.
Published in:	Proceedings of the ION 2024 Pacific PNT Meeting April 15 - 18, 2024 Hilton Waikiki Beach Honolulu, Hawaii
Pages:	758 - 782
Cite this article:	Eissfeller, Bernd, Pany, Thomas, Dötterböck, Dominik, Förstner, Roger, "A Comparative Study of LEO-PNT Systems and Concepts," Proceedings of the ION 2024 Pacific PNT Meeting, Honolulu, Hawaii, April 2024, pp. 758-782. https://doi.org/10.33012/2024.19646
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