Innovative techniques for Collective Detection of multiple GNSS signals in challenging environments

Abstract

Collective Detection (CD) is an interesting technique for acquiring highly attenuated satellites signals in harsh environment. The idea of this approach is to process all signals in view collectively to take advantage of the spatial correlation between GNSS signals as vector acquisition. In this way, the acquisition of weak signals will be facilitated by the presence of stronger ones. Increasing the coherent integration time for acquisition of weak GNSS signals in challenging environments is limited by several sources which can increase the Doppler shift. In this study, we propose a new methodology for acquisition processing within the Collective Detection approach. The standard CD performs a coarse estimation of the user position in the position domain using a collective metric combining individual satellites correlations computed separately using the standard Fast Fourier Transform (FFT) for parallel code search acquisition. In the proposed algorithm, we compute the Collective Detection metrics in function of both the code phase and the Doppler frequency for all visible satellites by applying an efficient technique to estimate the Doppler frequency. The new approach consists of applying the Spectral Peak Location (SPL) delta-correction technique within the CD algorithm using the Bi-dimensional Parallel Search (BPS) acquisition method. The proposed acquisition method allows improving the accuracy of the Doppler estimation through FFT, and therefore enhancing the correlation energy. The application of this proposition is tested and validated with real GPS signals to illustrate the increased sensitivity and the reduced complexity.