基于矢量跟踪的城市环境下非视距信号的检测和修正

In urban environments, GNSS positioning performance is unsatisfactory due to severe multipath and non-line-of-sight (NLOS) effects caused by nearby high-rise buildings. Many attempts have been made to reduce or mitigate these effects, e.g. receiver-based signal processing design, sophisticated antenna design and measurement quality check. These methods have some drawbacks, however, such as complicated signal processing or hardware requirement. Besides, these methods have no significant improvement against NLOS-caused errors. A promising technique to detect NLOS reception is vector tracking (VT), which is more robust against signal interference and attenuation due to its combination of signal tracking and navigation solving. Previous research mainly focuses on the detection and exclusion of NLOS reception. In urban areas, however, satellite availability is also a critical issue due to severe signal blockages. The exclusion of NLOS signals would further de-crease satellite availability. In this paper, NLOS error is corrected and exploited for positioning after it is detected by VT. VT estimates the code delay according to both the incoming measurements and the system propagation. Therefore, the NLOS reception would not be locked onto in VT, and the correction of NLOS signal can be extracted from the code discriminator output or correlation value. To verify the performance of the proposed method, an NLOS reception is simulated
using a direct signal cancellation algorithm where a replica of one of the direct signals is subtracted from the received signals and a code-delayed version of the same replica signal is then added to the original signals. Results show that with NLOS reception detection and correction, NLOS reception can be accurately
detected and positioning performances can be improved significantly without any external aiding.