High precision positioning technology

In order to improve the positioning accuracy in complex electromagnetic environment, some novel algorithms have been developed such as multipath mitigation algorithm, RAIM algorithm, spoofing detection algorithm, GNSS/INS deep fusion etc.

Multipath mitigation algorithm:

This algorithm can detect and mitigate the multipath signal no matter if the LOS signal is exist. All the characteristics of multipath signal can be calculated to improve the positioning performance.

The comparison of positioning performance is given as follows:

The left panel is the position result after multipath mitigation, while the right panel is the result before multipath mitigation. It can be seen that the positioning performance has been improved after using the proposed algorithm.

GNSS/INS integrated navigation

GNSS/INS integrated technology can help receiver to improve the tracking sensitivity in weak signal environment. A novel VDLL algorithm is proposed to implement in the software receiver to increase the robust performance of positioning.

Spoofing detection

In order to detect repeater spoofing signal with single antenna for ordinary civilian users, a novel algorithm is proposed to solve this problem. A 3D model of environment is constructed to analyze the signal propagation model and depict the result of proposed algorithm.

The following figure shows that the proposed algorithm detects a spoofing signal and a multipath signal of a GEO satellite and provides its detail feature like carrier phase, code delay, correlation shape and SNR. In this figure, the blue line represents the repeater spoofing signal and the green line represents the multipath signal. The third subfigure depicts that power of spoofing signal is a little stronger than direct line of sight signal and power of multipath is very weak.

Spoofing signal detection

The positioning results show that the positioning error of standard hardware receiver which uses single point positioning with multi-constellations is about sixty meters. When software receiver, used for the experiments, only uses single point positioning with beidou, positioning error may expand over one hundred meters. However, the positioning error of software receiver is reduced within ten meters in the same environment while using proposed anti-spoof algorithm and this result meets the standard of single point positioning method. In addition, the position of spoofer calculated by proposed algorithms is approximate equal to the true position. A 3D model of environment is constructed to analyze the signal propagation model and depict the result of proposed algorithm.

Positioning result by using spoofing detection algorithm