Dithered Sampling and Averaging for GNSS Signal Decoding Using Conventional Hardware

G. Falco

Abstract:	With the launches of two GALILEO test satellites named GIOVE-A and GIOVE-B and the Chinese Compass-M1 new Global Navigation Satellite Systems (GNSS) are moving ahead. As soon as these satellites started to broadcast, several researchers tried to observe and decode the signals, using the limited amount of unclassified information. In some cases the new signal modulations have been observed using high gain antennas, which provide a positive Signal to Noise Ratio (SNR), such that both the individual chips and the navigation bits can be observed without performing the despreading procedure. By means of this type of observations, it was possible to perform an accurate analysis of the signal structure and to identify unknown spreading codes. In this paper we propose a different approach to codes understanding that does not require sophisticated hardware or expensive equipments, but allows to derive the unknown code sequences from the signal received with a regular GNSS antenna. The methodology proposed is based on signal processing techniques, and in particular on a sampling frequency multiple of the received code rate and a following averaging stage. The method drastically improves the SNR in post processing and can be applied to any GNSS Direct Sequence Spread Spectrum (DSSS) signal structure without need of a priori removal of the mutual interference coming from other satellites. As an example of application results are presented for the GIOVE-A open service signals, that is representative of the new class of signals in which a data and a pilot channel are multiplexed.
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:	2926 - 2933
Cite this article:	Falco, G., "Dithered Sampling and Averaging for GNSS Signal Decoding Using Conventional Hardware," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2926-2933.
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