1,720,970 research outputs found
Galileo/GPS Mass Market Receivers: Tracking Algorithms Analysis and Performance
No full textThe scope of the work is the development and demonstration of the main GNSS algorithms currently used in GNSS mass-market receivers, with a particular interest toward Galileo signals. An exhaustive survey on existing commercial receivers signal processing techniques has been carried out and the most promising state-of-the-art algorithms for GPS signals have been analyzed and extended to E1B and E1C Galileo signals. The selected techniques have then been implemented in a software receiver, able to process raw GPS and Galileo samples. First the accuracy of the techniques is analyzed, both in terms of code delay and Doppler frequency estimates accuracy, proving the functionality of the multicorrelator processing unit. Second, some tests on robustness sensitivity have been carried out with a simulated LMS channel, proving the benefits of open loop strategies. Finally some tests on power consumption, representing one of the key drivers for the mobile consumer devices design, are carried out. The analysis of the results provides an early assessment on the suitability of these techniques, improving the attractiveness of Galileo to the massmarket community
Code and Frequency Estimation in Galileo Mass Market Receivers
No full textMass market receivers feature particular signal processing techniques, to comply with mobile and consumer devices resources and requirements. Delay and frequency estimation algorithms have then been redefined or adapted, in particular to cope with the new Galileo OS signals. The scope of the work is the analysis, development and performance examination of some of the main GNSS acquisition and tracking algorithms currently used in mass market receivers. The feasibility of such techniques is proved by means of semi-analytical and Monte Carlo simulations, outlining the estimators sensitivity and accuracy, and by tests on real Galileo IOV signal
An Insight on Mass Market Receivers Algorithms and their Performance with Galileo OS
No full textThe scope of the work is the development and demonstration of the main GNSS algorithms currently used in mass-market GNSS receivers, by focusing on a GPS and Galileo consumer receiver. Indeed, the global market for commercial GNSS chipsets continue to rapidly grow. In the next future. when more constellations are available, the constellations selection may be driven by particular signal characteristics that can result helpful features. Thanks to the release of the Galileo ICD in 2010, Galileo capable chips have been developed well in advance and at present there are several consumer devices ready to process Galileo signals with just a firmware update, for example the STM Teseo 2.
An exhaustive survey on existing mass-market signal processing techniques has been carried out; the most promising state-of-the-art algorithms for GPS signals have been analyzed, implemented in a software receiver and extended to E1BC Galileo signals. The performance of these techniques in terms of code delay and Doppler frequency estimates has been verified with simulated GNSS data.
At the same time, three main mass-market design drivers have been identified, studied with the software receiver and tested with the Teseo 2. First the TTFF for different C/N0, for hot, warm and cold start, and for different constellation combinations has been computed. Then some tests on the sensitivity in harsh environments have been carried out, exploiting a simulated LMS channel and different user dynamics. Finally, power consumption strategies, in particular duty cycle tracking, were considered.
The testing activity has been conducted in the ESTEC Navigation Lab and, on-field, using a mobile test-bed vehicle. The analysis of the results spots the performance differences between the same algorithms applied to different constellation signals and provides an early assessment on the suitability of their characteristics, hereby improving the attractiveness of Galileo to the mass-market community
A mass-market Galileo receiver: Its algorithms and performance
Full text linkThe two main GNSS receiver market segments, professional high-precision receivers and mass market/consumer receivers, have very different structure, objectives, features, architecture, and cost. The code-delay estimation is performed in the software receiver by a parallel correlation unit, giving as output a multi-correlation with certain chip spacing. This approach presents some advantages, mostly the fact that the number of correlation values that can be provided is thousands of times greater, compared to a standard receiver channel. Use of multiple correlators increases multipath-rejection capabilities, essential features in mass-market receivers, especially for positioning in urban scenarios. The TTFF was estimated with about 50 tests, in hot, warm, and cold start, first using both GPS and Galileo satellites, and then using only one constellation. In the second case only the 2D fix is considered, since, according to the scenario described, at maximum three satellites are in view
Performance analysis of duty-cycle power saving techniques in GNSS mass-market receivers
No full textThe scope of this work is the analysis and assessment of power saving duty cycle techniques for GNSS receivers. One of the key design drivers of mass-market commercial GNSS devices is indeed power consumption. Different techniques are analyzed and a particular method, based on the alternation of active and sleep states, is implemented in a software receiver based on open-loop processing. The main issues related to the parameters re-initialization after the sleep state are described and a solution is proposed. Then, accuracy and performance are evaluated, for different signal power and in three different scenarios, simulating a static, a pedestrian and an automotive user. Results prove the good accuracy of the technique proposed in all conditions, confirming its validity also for applications different from the consumer market
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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