Experimental Evaluation of Fine-Time Aiding in Unsynchronized Networks

Nicolas Couronneau, Peter J. Duffett-Smith

Abstract:	We demonstrate that the long-term stabilities of the signals from an unsynchronized cellular network can be exploited to provide fine-time aiding to a mobile GPS receiver. The time to first fix (TTFF) of a GPS receiver can be shortened by providing accurate GPS time to the receiver, thus improving the user experience. We present the results of experiments made to measure the stability of an unsynchronized cellular network. These show a large heterogeneity in the overall stabilities of the time signals from the individual cellular base stations and the importance of the mechanisms used to control disciplined oscillators. We introduce an ensemble filter with the goal of improving the long-term stability of the local oscillator in a mass-market GPS device, without the need for specific equipment in the cellular network. The filter is evaluated for two types of oscillator models and we show that a simple random-walk model can provide time aiding with an accuracy better than 50 µs over 4 days in a GSM unsynchronized network.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	711 - 716
Cite this article:	Couronneau, Nicolas, Duffett-Smith, Peter J., "Experimental Evaluation of Fine-Time Aiding in Unsynchronized Networks," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 711-716.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In