Abstract
In global navigation satellite system (GNSS)-based positioning and applications, multipath is by far the most obstinate impact. To overcome paradoxical issues faced by current processing approaches for multipath, this paper employs an intrinsic method to identify and mitigate multipath based on empirical mode decomposition (EMD) and Hilbert–Huang transform (HHT). Frequency spectrum and power spectrum are comprehensively employed to identify and extract multipath from complex data series composed by combined GNSS observations. To systematically inspect the multipath from both code range and carrier phase, typical kinds of combinations of the GNSS observations including the code minus phase (CMP), differential correction (DC), and double differential (DD) carrier phase are selected for the suggested intrinsic approach to recognize and mitigate multipath under typical positioning modes. Compared with other current processing algorithms, the proposed methodology can deal with multipath under normal positioning modes without recourse to the conditions that satellite orbits are accurately repeated and surrounding environments of observing sites remain intact. The method can adaptively extract and eliminate multipath from solely the GNSS observations using intrinsic decomposition mechanism. From theoretical discussions and validating tests, it is found that both code and carrier phase multipath can be identified and distinguished from ionospheric delay and other impacts using the EMD based techniques. The resultant positioning accuracy is therefore improved to an obvious extent after the removal of the multipath. Overall, the proposed method can form an extensive and sound technical frame to enhance localization accuracy under typical GNSS positioning modes and harsh multipath environments.
Highlights
The global navigation satellite system (GNSS) based technology is rapidly penetrating into various fields, and more and more high performances are preferred
It is a side effect relating with scenarios, which may result in time delay for code range, power loss of signal, carrier phase distortion, and phase rate changes relative to line-of-sight signal
Huang in 1998 aiming at decomposition of any signal into a series of intrinsic mode function (IMF), which is known as empirical mode decomposition (EMD)
Summary
The global navigation satellite system (GNSS) based technology is rapidly penetrating into various fields, and more and more high performances are preferred To meet these high-accuracy needs, many efforts have been made to cope with different impact factors including satellite orbit dithering, satellite and receiver clock biases, ionospheric and tropospheric delay, multipath reflections, jamming, and other interferences. These can be classified as influences derived from devices and environments. Multipath is regarded as a propagation anomaly of line-of-sight signal caused by reflection or diffraction from objects surrounding antenna [1] It is a side effect relating with scenarios, which may result in time delay for code range, power loss of signal, carrier phase distortion, and phase rate changes relative to line-of-sight signal. Since multipath cannot be eliminated using differential processing or numerical modeling, its impact is obstinate and remains a vital mission for researchers to seek for remedy against positioning loss caused by it in the worse cases [2]
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