Improving High Sensitivity GNSS Receiver Performance in Multipath Environments for Vehicular Applications
Date
2013-09-24
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Abstract
Generally, standalone GNSS receiver architectures cannot provide a position accuracy suitable for use in vehicular applications in urban canyon scenarios. Specifically, GNSS signals are affected by the surrounding objects, such as high buildings, trees, etc., which will introduce multipath errors. Multipath arises from the reception of reflected or diffracted signals in addition to the line-of-sight (LOS) signal, and is one of the most detrimental error sources in GNSS positioning applications. By using a block processing high sensitivity receiver scheme with more correlators and/or longer coherent integration time, this thesis aims to obtain better positioning performance in the urban canyon areas.
It was reported that signal correlation peaks (e.g., LOS correlation peaks, multipath correlation peaks) may be separated in the Doppler domain by a long coherent integration time. Generally, the dominant peak is utilized in high sensitivity receivers, however, this approach is not always optimal in multipath environments since it is not assured that the dominant peak is the LOS peak. In this regard, a LOS peak identification scheme is proposed in this work, which yields better positioning performance compared to the dominant peak scheme.
Multipath distributions in the urban canyon area are characterized in this work. In particular, the Doppler frequency and code phase delay under different conditions are assessed as a function of vehicle speed and signal power. Results of this characterization is use to configure the receiver to better remove the multipath signals. More specifically, the multipath distribution will eventually affect the search strategy (i.e., search space size, coherent integration time) utilized in the high sensitivity receiver. Multipath directional-dependence phenomenon (i.e., the variation resulting from the direction of travel of the user) is observed during this process; and the multipath maximum Doppler offset and minimum Doppler offset are derived and verified by the real data, and finally used to detect errors in the receiver’s navigation solution.
It is shown that most of the multipath peaks are removed in the receiver after using the proposed algorithm; consequently, pseudorange and Doppler accuracies are improved substantially. Also, different search space sizes and coherent integration times are compared in this work and an empirically-optimal search strategy is developed. Three data sets collected in the urban canyon areas are used to assess the proposed high sensitivity receiver strategy, it is shown that the position accuracies are better than 20 m.
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Citation
XIE, PENG. (2013). Improving High Sensitivity GNSS Receiver Performance in Multipath Environments for Vehicular Applications (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26488