A Subspace-based Spatial and Temporal Multipath Mitigation for GPS Signal in Dynamic Enviroment

Within recent years, global navigation satellite systems (GNSS) have been wildly used in many positioning and navigation applications. However, the GNSS multipath rays are often reflected by the buildings, and they have been a major positioning error source in urban area. Many classic multipath mitigations only use the signal characteristics in time, but not take the spatial property into consideration. Besides, the tracking results may get swinging in dynamic environment when incident rays do not share the same Doppler frequency offset (DFO). In this paper, we propose a subspace-based loop design to mitigate the multipath effects and prevent this swinging problem in tracking. The direction-of-arrival (DOA) and relative delay of each ray are estimated jointly by a subspace-based estimator. The line-of-sight ray parameters is chosen by its first arrival property, then the complex amplitudes effects of multipath rays can be least-square (LS) estimated and canceled at the discriminator. Therefore, the multipath effects in code phase estimation are greatly mitigated. Compared with the existing methods, the multipath error envelops (MEE) and the root mean squared error (RMSE) simulations show that the proposed method achieves the best multipath mitigation performance and the most accurate delay estimation.