Showing papers by "Mohamed Sahmoudi published in 2011"

A New Frequency Offset Correction Approach for Enhancing Sensitivity of GNSS Receivers

Abstract: Increasing the coherent integration for acquisition of weak GNSS signals in urban and indoor environments is limited by several challenges. Besides of the possible sign reversal of the navigation data bit every 20ms, Doppler shift increases with the integration time. Inaccurate estimate of this offset may severely reduce the correlation power and prevent the receiver from detecting the presence of low-power signals. Standard acquisition approaches are not efficient for performing long coherent integrations. Furthermore, they achieve their limitations in high dynamics, where the signal frequency cannot be considered constant over the entire period of observation. In this paper, Frequency Offset Correction (FOC) loops are explored to compensate for the Doppler shift during the correlation process, thus enhancing stand-alone receivers’ sensitivity. The estimated frequency offset during the previous coherent integrations is used in a feedback scheme for self-aiding to extend the coherent integration time. We propose a new FOC loop architecture for compensating the frequency of each sample of the input signal. State of the art frequency compensation methods correct for the frequency drift on the post-correlation output for fine acquisition. At this stage, the correlation loss is already large enough to prevent the gain from accumulating longer signal.