Ambiguity Peak Resolution for Navigation Receiver

J-J. Floch, F. Soualle, J. Wendel

Abstract:	In the frame of Radio Navigation Satellites, new signal waveforms have been designed to fulfill new requirements, such as high accuracy, improved spectral separation with other signals sharing the same frequency bands. Despite the aforementioned performance improvements, these new modulations have also introduced new limitations like the ambiguity constraint of the multiple peaks in the auto-correlation function. There is a risk that a tracking loop locks to a side-peak, which results in a systematic error in the pseudorange measurements if this is not detected and mitigated. Such a false lock to a side-peak leads to errors in the position, velocity and time (PVT) solution and needs to be avoided. In order to minimize the probability of false lock as described above, the authors of the present contribution developed an innovative approach in the time domain for the resolution of the aforementioned bias. The principle is similar to the Bump-jump algorithm approach; it uses extra-correlators for the detection of false peak acquisition, additionally to the correlators currently used for code tracking and demodulation. For an optimized performance, the detection would require the same number of correlators as they are peaks in the correlation function. To apply this new technique, the principle would be initially to evaluate the ratio between the different correlators located on each of the correlation’s peak. The correlation would be characterized at the output of the receiver front-end considering the real distortions due to the payload (e.g. transmitted bandwidth) and receiver front-end. During tracking, the receiver would compare the ratio of the different correlators with the theoretical and expected ones. If the differences of the ratios are higher or lower than a pre-defined threshold, false peak synchronization will be detected and will be corrected to be inline with the theoretical results, knowing that the correlator “0” needs to track the central peak. The advantage of this method is that the distortions of the transmitted signal will not impact the performance as the method uses a referenced correlation function considering the payload and receiver distortions. Due to the high number of available information, the probability of a missed detection is very low even in a multipath environment. Additionally, and as part of the paper’s conclusion, the necessary modifications on the classical structure of a CDMA software navigation receiver are studied to support our bias detection method.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	868 - 875
Cite this article:	Floch, J-J., Soualle, F., Wendel, J., "Ambiguity Peak Resolution for Navigation Receiver," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 868-875.
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