GLONASS Orbits in GPS/Galileo-style Ephemeredes for Assisted GNSS

Lauri Wirola and Jari Syrjarinne

Abstract:	The 3GPP (Third Generation Partnership Project) Release 7 of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) cellular standards include major modifications as to how AGNSS (Assisted GNSS) assistance data is transferred from the cellular network to the cellular terminal. One of the major changes in the coming 3GPP GSM/UMTS Release 7 is the introduction of multi-mode navigation model. This navigation model supports all the native formats, including Galileo ephemeris. Multi-mode navigation model also enables an interesting opportunity to provide navigation model assistance in nonnative formats. For instance, the multi-mode model allows, if desired, representing GLONASS orbits and clocks using GPS/Galileo Keplerian ephemeris and GPS clock model. Such a solution simplifies the network and terminal implementation as well as partly harmonizes performance between different GNSSs. The current work examines, if GLONASS orbits and clocks can be represented with the bit counts and scale factors available in GPS/Galileo ephemeris. The analysis is based on the final precise orbits for GPS and GLONASS as well as clocks for GPS from International GNSS service over 19 weeks. The final GLONASS clocks were obtained from the Russian Mission Control Centre, MCC. Included in the analysis are GPS weeks 1437-1455. Keplerian parameters and clock models were fitted to these data in 4-h blocks. The results show that GLONASS orbits and clocks can be expressed in 4-h blocks using GPS/Galileo-style ephemeris without difficulties. The study also reveals interesting differences in the characteristics of GPS and GLONASS orbits.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	1032 - 1039
Cite this article:	Wirola, Lauri, Syrjarinne, Jari, "GLONASS Orbits in GPS/Galileo-style Ephemeredes for Assisted GNSS," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 1032-1039.
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