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Simultaneous BOC subcarrier ambiguity fixing using the LAMBDA method

: Wendel, J.; Schubert, F.M.; Gulie, I.; Rügamer, A.

Institute of Navigation -ION-, Manassas/Va.; Institute of Navigation -ION-, Satellite Division, Washington/DC:
28th international technical meeting of the Satellite Division of The Institute of Navigation, ION GNSS+ 2015. Proceedings : Sept. 14 - 18, 2015, Tampa Convention Center, Tampa, Florida
Manassas/Va.: ION, 2015
Institute of Navigation, Satellite Division (ION GNSS International Technical Meeting) <28, 2015, Tampa/Fla.>
Fraunhofer IIS ()

The autocorrelation function of binary offset carrier (BOC) modulated signals contains multiple peaks, and therefore multiple stable tracking points when a conventional early-minus-late tracking loop is used. A false lock to such a side-peak leads to an offset in the corresponding pseudorange measurement, which in turn corrupts the PVT solution. A variety of techniques have been proposed for the tracking of BOC modulated signals. This paper analyses the background of the most important BOC tracking techniques which are able to provide independent pseudoranges both from subcarrier tracking and from code tracking. This analysis shows that further BOC tracking architectures can be proposed, which are outlined briefly. However, all of these techniques aim at fixing the subcarrier ambiguity -i.e. to detect and correct false locks - for each channel independently. Mathematically, the problem of fixing subcarrier ambiguities is identical to the problem of fixing carrier phase ambiguities. Therefore, it is possible to use the well-established techniques for carrier phase ambiguity resolution also for subcarrier ambiguity fixing, e.g. the LAMBDA method. An outline of this idea is given, and experimental results are provided, obtained from the tracking BOC(1,1) modulated signals generated by a space segment simulator. The experimental results clearly indicate the superiority of the LAMBDA-based simultaneous subcarrier ambiguity fixing w.r.t. the standard techniques, which solve the subcarrier ambiguities for each tracking channel independently.