Fully-autonomous Fine Time Aiding to a GPS Receiver in a Cellular Telephone

Robert Rowe, Murray R. Jarvis, Simon D. Hern, Peter J. Duffett-Smith and Anthony R. Pratt

Abstract:	This paper describes a fully-autonomous scheme for maintaining accurate GPS time in a cellular phone operating in an unsynchronized cellular network (GSM or WCDMA). In this context, autonomous means that the system is entirely cell-phone based, requiring no additional contact with a server. The system requires only information off air with no need for a database of cell tower positions. The accuracy of time maintenance is in the order of a few microseconds to tens of microseconds. However it depends strongly on how the system is used, as will be discussed in detail. The benefit of maintaining GPS time is the potential for reducing the GPS signal search space with consequent improvements in time to fix and power consumption. A description of the principles and error sources is given together with data obtained from a prototype implementation.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	1876 - 1883
Cite this article:	Rowe, Robert, Jarvis, Murray R., Hern, Simon D., Duffett-Smith, Peter J., Pratt, Anthony R., "Fully-autonomous Fine Time Aiding to a GPS Receiver in a Cellular Telephone," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 1876-1883.
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