GPS Position Aiding in a Cellular Telephone without the Network

M.R. Jarvis, R.W. Rowe, P.J. Duffett-Smith, A.R. Pratt

Abstract:	Standardised methods of providing assistance to a GPS receiver make use of a network-based server with access to GPS information which can be sent on request to a mobile terminal. Such information includes satellite position information (almanac and ephemeris), but may also include time, frequency and position information to centre and bound the satellite signal acquisition windows. GPS receivers need such assistance when operating in challenging environments, such as inside a building, in order to provide the user with a fast-enough position and without draining the battery too much. The challenge faced by terminals of GSM and W-CDMA systems is that the network transmitters are unsynchronised and hence cannot support methods employed, for example, in CDMA and CDMA-2000 systems. Furthermore, network operators often consider that their network details are commercially sensitive, so that it may not be possible to obtain, for example, a database of base-station coordinates. At a recent ION meeting, we described a method for obtaining and maintaining accurate GPS time in a cellular telephone (GSM/W-CDMA), for the purpose of aiding a GPS receiver, which was autonomous in the sense that it needed no support from a network server and did not require knowledge in the terminal of base-station positions. In this paper, we extend the method to include the provision of position aiding, and hence position fallback, to a GPS receiver. The distinctive feature is that assistance (time, frequency and position) is provided to the GPS receiver without requiring participation by the network operator in any sense, neither needing a network server, nor a database of base station positions, nor the collaboration nor consent of the network operator and in particular incurs no data communications costs with the network. We support this using real data collected from a prototype system.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1821 - 1828
Cite this article:	Jarvis, M.R., Rowe, R.W., Duffett-Smith, P.J., Pratt, A.R., "GPS Position Aiding in a Cellular Telephone without the Network," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1821-1828.
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