Effects of Cross Correlation on High Performance C/A Code Tracking

Zhen Zhu and Frank van Graas

Abstract:	Due to the GPS C/A code structure, cross correlation errors can be observed between different satellites. For many applications, the resulting errors are negligible compared to other error sources such as multipath. However, for high-accuracy and high-integrity systems that primarily rely on the C/A code ranging performance, cross correlation errors must be considered. For example, the performance of a Signal Quality Monitoring (SQM) function for reference receivers is affected by cross correlation. If the cross correlation errors are not well understood, they could cause false alerts or limit the ability to detect and characterize multipath errors. This paper provides a detailed analysis of cross correlation errors. The analysis has been verified with both computer simulations and receiver bench tests. Cross correlation errors reach maximum values for Doppler frequency differences that are well outside the tracking loop bandwidth. In most applications, these errors are mitigated through extended carrier phase smoothing of the pseudorange measurements. For SQM, decisions must be made at the meter-level on short data segments, on the order of a few seconds, which necessitates a complete characterization of cross correlation errors. The results provided in this paper also apply to high-frequency multipath error characterization and high performance indoor GPS positioning.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	1053 - 1061
Cite this article:	Zhu, Zhen, van Graas, Frank, "Effects of Cross Correlation on High Performance C/A Code Tracking," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 1053-1061.
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