https://orcid.org/0000-0002-7083-6001
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ABSTRACT
Low Earth Orbit (LEO) satellite navigation signal can be used as an opportunity signal in the case of a Global Navigation Satellite System (GNSS) outage, or as an enhancement by means of traditional GNSS positioning algorithms. No matter which service mode is used, signal acquisition is a prerequisite for providing enhanced LEO navigation services. Compared with the medium orbit satellite, the transit time of the LEO satellite is shorter. Thus, it is of great significance to expand the successful acquisition time range of the LEO signal. Previous studies on LEO signal acquisition are based on simulation data. However, signal acquisition research based on real data is crucial. In this work, the signal characteristics of LEO satellites: power space density in free space and the Doppler shift of LEO satellites are individually studied. The unified symbolic definitions of several integration algorithms based on the parallel search signal acquisition algorithm are given. To verify these algorithms for LEO signal acquisition, a Software Defined Receiver (SDR) is developed. The performance of these integration algorithms on expanding the successful acquisition time range is verified by the real data collected from the Luojia-1A satellite. The experimental results show that the integration strategy can expand the successful acquisition time range, and it will not expand indefinitely with the integration duration. The performance of the coherent integration and differential integration algorithms is better than the other two integration algorithms, so the two algorithms are recommended for LEO signal acquisition and a 20 ms integration duration is preferred. The detection threshold of 2.5 is not suitable for all integration algorithms and various integration durations, especially for the Maximum-to-Mean Ratio indicator.
Data availability statement
The data that support the findings of this study are available from the State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing (LIESMARS), www.lmars.whu.edu.cn. The University of Wuhan, but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are, however, available from the authors upon reasonable request and with permission of LIESMARS.
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Notes on contributors
Liang Chen
Liang Chen is a professor in the State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University. His research interests include indoor positioning, wireless positioning, sensor fusion, and location-based services.
Xiangchen Lu
Xiangchen Lu is currently studying for a PhD in Geodesy at Wuhan University. His research direction is LEO navigation augmentation and software defined receiver.
Nan Shen
Nan Shen received a PhD degree from Wuhan University in 2021. His research interests focus on precise GNSS data processing, software defined receiver.
Lei Wang
Lei Wang is currently an associate research fellow at Wuhan University. He obtained a PhD degree from Queensland University of Technology, Australia in 2015. His research interest includes GNSS precise positioning, LEO navigation augmentation, LEO precise orbit determination, indoor positioning systems.
Yuan Zhuang
Yuan Zhuang is a professor at Wuhan University. His current research interests include multi-sensors integration, real-time location system, personal navigation system, wireless positioning, Internet of Things (IoT), and machine learning for navigation applications.
Ye Su
Ye Su is a masters student at Wuhan University. Her current research interests include outdoor positioning and V-SLAM.
Deren Li
Deren Li received the Dr. Eng. degree in photogrammetry and remote sensing from Stuttgart University, Stuttgart, Germany, in 1985. He was elected as an Academician of the Chinese Academy of Sciences, Beijing, China, in 1991, and the Chinese Academy of Engineering, Beijing, and the Euro–Asia Academy of Sciences, Beijing, in 1995. He was the President of the International Society for Photogrammetry and Remote Sensing Commissions III and VI and the first President of the Asia GIS Association, from 2002 to 2006. His research interests include spatial information science and technology, such as remote sensing, GPS and geographic information system (GIS), and their integration.
Ruizhi Chen
Ruizhi Chen is currently the director of LIESMARS. He was elected an Academician of Finnish Academy of Science and Letters in 2021. His main research interests include smartphone ubiquitous positioning and satellite navigation and positioning.