GPS Multipath Detection in the Frequency Domain

TL;DR

This paper introduces FFT-based detectors for GPS multipath detection, improving the ability to identify and exclude multipath-affected signals in precise positioning, applicable to various GNSS systems.

Contribution

It presents novel FFT-based binary hypothesis tests for multipath detection in GPS, validated with simulated and real data, enhancing multipath mitigation techniques.

Findings

Detectors effectively identify multipath signals in GPS data.

Detection methods work with both scalar and vector tracking loops.

Techniques can be extended to other GNSS systems.

Abstract

Multipath is among the major sources of errors in precise positioning using GPS and continues to be extensively studied. Two Fast Fourier Transform (FFT)-based detectors are presented in this paper as GPS multipath detection techniques. The detectors are formulated as binary hypothesis tests under the assumption that the multipath exists for a sufficient time frame that allows its detection based on the quadrature arm of the coherent Early-minus-Late discriminator (Q EmL) for a scalar tracking loop (STL) or on the quadrature (Q EmL) and/or in-phase arm (I EmL) for a vector tracking loop (VTL), using an observation window of N samples. Performance analysis of the suggested detectors is done on multipath signal data acquired from the multipath environment simulator developed by the German Aerospace Centre (DLR) as well as on multipath data from real GPS signals. Application of the detection tests to correlator outputs of scalar and vector tracking loops shows that they may be used to exclude multipath contaminated satellites from the navigation solution. These detection techniques can be extended to other Global Navigation Satellite Systems (GNSS) such as GLONASS, Galileo and Beidou.