Analysis of a software-based A-GPS acquisition performance using statistical processes

Abstract : The efforts of the semiconductor industry to produce small, low consumption and powerful chipsets bear fruit, and many portable devices are now equipped with them. Indeed, the miniaturized chipsets with increasing processing power make them suitable for supporting software-based applications. On the other hand, demand for indoor navigation and location based services applications, whose interoperability with GNSS technology is being more and more obvious, is expected to grow rapidly in the next few years. In this context, because of their maximum flexibility and minimum hardware modifications, software-based positioning techniques embedded in portable devices become very interesting. The remaining key point is the time needed to acquire these rare and weak indoor signals and give a position solution. The aim of this study is to present results on the time needed to acquire one satellite for such embedded GPS applications, and more specifically, for Assisted-GPS ones. In this paper, an RF front-end chipset combined with a processor embedded in a portable device is considered. Only the acquisition process using FFT correlations will be studied here. The classical structure for L1 code FFT acquisition is first described and acquisition performance, such as the mean acquisition time, is discussed. A statistical process is used to simulate acquisition procedures, according to probabilities of detection, acquisition structure and the implemented acquisition strategy. The estimated times are then deduced from these tests. A special study is carried out to measure the impact of the Doppler affecting the GPS signal. An analysis of the effect of the computational power is also conducted, as well as the influence of the signal-to-noise ratio on the acquisition procedure, mostly dedicated to indoor and deep indoor environments. Results point out the fact that to achieve the requirements of the application supporting the software-based acquisition process, a trade-off has to be found between performance relative to the acquisition of weak signals, and the rapidity of the processing, especially in deep indoor environments. The evaluation of the Doppler component due to user dynamics and the acquisition strategy are also key points that would speed up the process.
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Submitted on : Thursday, October 30, 2014 - 11:14:27 AM
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Damien Kubrak, Christophe Macabiau, Michel Monnerat. Analysis of a software-based A-GPS acquisition performance using statistical processes. ION NTM 2005, National Technical Meeting of The Institute of Navigation, Jan 2005, San Diego, United States. pp 1082 - 1092. ⟨hal-01021736⟩



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