Blockage of the line-of-sight (LOS) component is one of the main problems of GNSS receivers when operating in harsh working conditions. This is the case, for instance, of urban canyons, where GNSS receivers in moving vehicles are subject to sudden fading events with more than 20 dB of signal attenuation. In these circumstances it is not possible for traditional receivers to keep track of the received signals, thus failing to provide reliable position fixes. The problem is aggravated when hardware implementation constraints need to be satisfied. For instance, as in target applications that involve embedding GNSS capabilities into ARM processors of mobile devices. Therefore, highsensitivity GNSS receivers with reduced complexity and power consumption are mandatory. The contribution of this paper is the proposal and analysis with synthetic signal of a Kalman filterbased architecture for robust and high-sensitivity tracking. The use of extended correlations mitigates the measurement noise and allows the tracking operation under these harsh conditions. The results obtained validate the strategy proposed to operate at a / 0 (carrier-to-noise ratio) as low as 15 dBHz.
This paper proposes an analytical model for estimating the standard deviation of the measurement ( ) error in a coherent early-late delay lock loop DLL when the input code is corrupted by a disturbing signal with ( ) arbitrary spectrum features. The approach is to analyze by Fourier techniques the interactions between the disturbance and the DLL processes to determine how the measurement is affected. The main utility of this model is for the analysis of interference effects on receivers for navigation systems, such as GPS, GLONASS, the Wide ( ) ( ) Area Augmentation System WAAS , and the European GNSS Navigation Overlay Service EGNOS .Following the theoretical derivation, the model is validated by comparison with experimental results obtained by adding radio frequency interference at different spectrum frequencies on a real navigation receiver. A theoretical analysis is also presented to cross-check the correspondence between the proposed model and the well-known models for the case of white-noise disturbances.
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