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A Subspace-based Spatial and Temporal Multipath Mitigation for Multi-antenna GPS Receiver

In this paper, a novel subspace-based spatial and temporal mitigation method is proposed for GPS signal tracking by a multi-antenna receiver in multipath environment. Since the tracking result from the delay-lock-loop has been polluted by the multipath incidence, we only use it to follow the code phase shift but design a subspace-based estimator to distinguish different incident rays by their spatial and temporal signatures. The carrier phase is firstly extended into the signatures because of the signal BPSK modulation. A subspace rotation invariance in space and DOAM-like correlation matrices are both established by the property of the receiving array, and a forward and backward space smooth is also taken here to solve the coherent problem by multipath. The angle-of-arrivals and signatures are estimated from the eigenvalues and eigenvectors from the cross-correlation matrix, the signatures also provide the relative delay and carrier phase estimates with respect to the tracking loop. The line-of-sight ray's estimates are picked up by its first arrival character, and a modified delay tracking output without multipath bias is finally achieved by combining tracking loop and the subspace estimator results together. 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.