Rabih Chrabieh and Serdar Sezginer, Nestwave, France

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In this paper, estimation of time of arrival (TOA) in multipath and Non-Line -of-Sight environments is tackled with a particular focus on GNSS positioning signals GPS L1 C/A and Galileo E1. Two novel approaches are introduced for multipath mitigation in GNSS. First, maximization, for the earliest path, of the signal to multipath and noise ratio (SINR) for a given PDP model, using a filter design matched to the earliest path or to TOA (TOA-MF [8]), and applied pre-correlators. The proposed pre-correlation filters are able to benefit from the large number of dimensions in the samples space in order to project onto sub-spaces relatively orthogonal to late arriving multipath. Second, matching the filter to the full PRN sequence of each satellite, which enables deep suppression of early sidelobes, and hence the unearthing of an earliest path from underneath heavy multipath. Indeed, at the PRN sequence level, the TOA-MF is able to cancel the small but undesirable auto-correlation’s sidelobes that can be found at non-zero time shifts for sequences such as Gold sequences. Simulation and field results confirm the significant gain of performance achieved by TOA-MF when the channel suffers from dense multipath interference or NLOS conditions. The techniques described in this article are code phase based multipath mitigation using a unique antenna, and are suitable for static or moving vehicles.