Correction Algorithm for SBAS C/A Code Interference

L. Lestarquit, M. Malicorne, M. Bousquet, V. Calmettes

Abstract:	Previous studies have showed the risk of false acquisition and C/N0 degradation in presence of C/A code cross-correlation interference [1]. But, tracking error can also appear. The interference mechanism is the same as if the interfering signal was multipath (code interference on itself). If the relative Doppler is equal to zero, the cross-correlation peak will not move relative to the main auto-correlation peak, the interference will give a lasting bias and both interfering codes will appear "quasi-stationary" relative to one another. However, unlike multipath, all the interfering signals can be tracked on independent channels. In its raw measurements, the receiver provides the relative code and phase offset, the relative Doppler, the relative power and the navigation message of the interfering signals. Knowing, the code cross-correlation function for any pair of signal, it's possible to predict the code measurement error, and therefore to correct it using an appropriate correction algorithm on the raw measurements. The tracking error due to C/A code cross-correlation with low Doppler has been little studied because for common GPS applications, the Doppler due to the satellite motion is high (ranging from -4.5kHz to 4.5kHz for standing user). There is a low probability to have a Doppler collision leading to a high tracking error. Indeed if the relative Doppler between the desired signal and interfering signals is higher than the receiver code loop noise bandwidth (less than 1 Hz typically), then the tracking error is filtered. But there are applications that have low relative Doppler: the first application concerns geostationary satellites and fixed receivers, and the second one concerns pseudolite use with a receiver on board a geostationary satellite.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	1345 - 1354
Cite this article:	Lestarquit, L., Malicorne, M., Bousquet, M., Calmettes, V., "Correction Algorithm for SBAS C/A Code Interference," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 1345-1354.
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