A subspace-based code tracking loop design for GPS multi-antenna receiver in multipath environment
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ORIGINAL ARTICLE
A subspace‑based code tracking loop design for GPS multi‑antenna receiver in multipath environment Xi Hong1 · Wenjie Wang1 · Ning Chang1 · Qinye Yin1 Received: 14 December 2019 / Accepted: 3 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Global Navigation Satellites Systems have been greatly developed in recent years, but receivers usually suffer the undesired measurement bias errors caused by multipath incidence in an urban area. We propose an effective subspace-based estimator cooperating with the conventional delay-locked loop (DLL) for Global Positioning System L1 C/A Signal. With the help of the multi-antenna, the incident rays could be distinguished in space. A forward and backward space spatial smooth technique is then taken to solve the coherent problem in signal subspace estimation. By using the structure of the receiving array, a subspace rotation invariance can be built, and the angles of arrival and relative delays of incident rays could be estimated jointly. After combining the estimates from DLL and subspace-based estimators, we can enhance the strength of the lineof-sight ray and achieve a modified delay tracking output without multipath bias effectively. Simulation results prove that compared with the existing methods, such as the narrow early-minus-late and the multipath estimating delay lock loop, the proposed method has the best multipath mitigation in the delay estimation. Keywords Multi-antenna receiver · Multipath mitigation DLL · Subspace-based estimator · FBSS · Joint delay · AOA estimation
Introduction Within recent decades, the development of the Global Navigation Satellite Systems (GNSSs) has made much progress. The USA first developed its Global Positioning System (GPS) from the 1970s, and the new Block-III satellites were launched last year with additional L1C and L5 broadcasting. China, Russia, and E.U. also developed Beidou, GLONASS, and Galileo systems, respectively. For the purposes of positioning improvement, Japan and India also have their own space-based local area GNSS enhancement systems (Fernandez-Prades et al. 2011). Although these systems are essential to location navigation applications, they usually suffer performance degradations from the ionosphere, troposphere, jammer, multipath, and other bad effects. Since more GNSSbased applications have been used in cities, multipath mitigation is now an important research point. Multipath rays are mainly caused by reflections surrounding the receiver
* Xi Hong [email protected] 1
Xi’an Jiaotong University, Xi’an, People’s Republic of China
and generate a bias error in pseudorange measurement. This error is environment-depended, so it is hard for the receiver to reduce the effects by using aid information from reference stations and local area enhancement systems. It means that the multipath effects shall be suppressed by the receiver in real-time applications. There is much research on multipath mitigation. Van Dierendonck et al. (1992) mitigates the multipath
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