A Compact Method to Deliver Extended Ephemeris Information that Complies with SUPL 1.0

E. Derbez, A. Izadpanah

Abstract:	The 3GPP/OMA Secure User Plane (SUPL) 1.0 standard provides a good framework for delivering real time GPS assistance data to A-GPS enabled terminals and many vendors are currently shipping fully compliant SUPL 1.0 devices. Work on SUPL 2.0 is already in progress. Implementing SUPL 2.0 support, while more challenging, will bring benefits, including support for multiple air interfaces, extended ephemeris and multiple GNSS constellations. This paper discusses the problems related to supporting extended ephemeris (7 days or more) across multiple GNSS constellations. The respective benefits of multi- GNSS constellation and extended ephemeris solutions have long been appreciated for mobile A-GPS systems. The problem of marrying both in SUPL 2.0 will be addressed, and a more bandwidth efficient solution using the current SUPL 1.0 standard augmented with onboard extended ephemeris generation (i.e. client-side propagation) is presented. A flexible framework allowing 7 days with graceful accuracy degradation is introduced and its characteristics are explored. Among these is the ability to deliver 7 day prediction for GPS / Glonass / Galileo in a common format and with around 6 KB of over-the-air payload -- all within the SUPL 1.0 framework. This compares favourably with the ~300KB payload that would be required by SUPL 2.0 for 1 week of combined GPS/ Glonass /Galileo extended ephemeris, a 25X to 50X improvement in delivery efficiency. Additionally, we discuss how this framework may be used to autonomously generate extended ephemeris. A conclusion from this analysis is that there are better ways in which service providers and their customers may receive 7 days of predicted ephemeris by extending the current standard with very small and low cost payloads, and all in a common format which will simplify Assisted- GNSS receiver software design. Notably, these payloads are also small enough to be economically broadcast over low bandwidth channels such as FM sub-carriers (eg RDS), and this will be the focus of a companion paper. We will include orbital error analysis using real data for this new onboard, client-based orbit propagation in the context of today's GPS and Glonass (similar analysis would hold for Galileo, QZSS, and Beidou). Actual receiver position fix data using this on board propagation will however only be shown for GPS.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	2054 - 2060
Cite this article:	Derbez, E., Izadpanah, A., "A Compact Method to Deliver Extended Ephemeris Information that Complies with SUPL 1.0," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2054-2060.
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