An Innovative and Efficient Frequency Estimation Method for GNSS Signals Acquisition

P. Esteves

Abstract:	In the acquisition of GNSS signals, the trade-off between complexity and sensitivity is critical. Within the search for signals, a coarse search grid in either code or frequency dimension may lead to missing some weak signals, but it may allow the application of computationally attractive acquisition methods. The recurrent tool for accelerated acquisition in GNSS software receivers is Fast Fourier Transform (FFT), which allows search parallelization in either dimension. While its application in the code delay search does not generally affect the acquisition detection performance, the same is not necessarily true in the frequency domain, due to the impossibility to freely define the frequency resolution. In this paper, we introduce a new method for GNSS signal acquisition employing a low-complexity approach adopted from signal processing literature which allows improving the accuracy of frequency estimation through FFT. This is achieved by calculating an offset (delta) based on the magnitude of the FFT bins obtained in the spectral analysis of the signal. The delta value represents an estimate of the difference between the true signal frequency and the closes FFT frequency bin, therefore improving the FFT-only estimation accuracy, without the need for heavy computations. The methodology to apply the delta-correction technique in the acquisition of GNSS signals is developed and proposed and results from both simulation and real data are used to illustrate the capacities of the newly developed method. The results show that the new method is capable of keeping the desired low complexity while being robust to a wide range of Doppler shifts within the FFT bin.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1996 - 2006
Cite this article:	Esteves, P., "An Innovative and Efficient Frequency Estimation Method for GNSS Signals Acquisition," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 1996-2006.
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