Advanced GPS signal processing techniques for LBS services

Par le passé, il était indispensable, pour le bon fonctionnement du GPS (Global Positioning System), que le signal soit en vision directe entre le satellite et le récepteur, et les signaux faibles n'étaient pas exploitables. Mais l'extension du GPS aux services LBS (Location Based Services) et à d'autres applications de navigation a changé ce paradigme. Par conséquent, on prévoit une augmentation considérable de techniques de localisation de plus en plus performantes, surtout dans des environnements du type indoor ou urbain. Les exigences de la localisation dans ce type d'environnements posent un véritable défi pour la conception des récepteurs GPS. Le but de la thèse est d'optimiser les techniques existantes de traitement du signal GPS pour la localisation dans des milieux contraints, dans le cadre de l'AGPS (Assisted GPS). Ce système suppose que le récepteur GPS est connecté ou introduit dans un téléphone portable. Ce genre de couplage permet de transférer au récepteur GPS des données d'assistance via le réseau GSM (Global System for Mobile communications). Ces données fournissent au récepteur GPS la liste des satellites visibles, mais aussi des valeurs estimées de leur Doppler et leur retard de code, réduisant ainsi la fenêtre de recherche de ces paramètres. Les travaux de la thèse consistent à explorer différentes techniques d'acquisition du signal GPS pour réduire le temps d'acquisition nécessaire ou TTFF (Time To First Fix), sans affecter la sensibilité du récepteur GPS. Ceci est réalisé après une étude du canal GPS radio. L'étude débute par une revue du GPS et de la structure du signal utilisé dans ce système. Le processus d'acquisition est ensuite décrit en détails: l'acquisition classique est décrite en premier pour mettre en évidence par la suite l'effet du milieu de propagation sur cette étape du traitement du signal. A cet effet, les milieux contraignants (Indoors et Urbains) seront modélisés et analysés. Cette analyse permettra de mettre en évidence les problèmes subits par les ondes radio se propageant dans ce type d'environnements. On notera que le canal urbain a été analysé en utilisant un modèle déjà existant élaboré par Alexander Steingass et Andreas Lehner du DLR (Centre Aérospatial Allemand) [Steingass et al., 2005]. D'autre part, un modèle statistique du canal indoor a été développé par l'ESA (European Space Agency) dans le cadre du projet intitulé “Navigation signal measurement campaign for critical environments” et présenté dans [Pérez-Fontán et al, 2004]. Mais ce modèle considère un canal statistique invariable dans le temps. Pour cela nous avons développé un modèle Indoor qui envisage plutôt un canal variant avec le temps, en prenant en compte les variations temporelles de certains paramètres du canal, comme le retard et la phase de la fonction de transfert. Les valeurs initiales de ces paramètres utilisés dans notre modèle sont toutefois basées sur les distributions statistiques fournies par le modèle de l'ESA. L'étude des canaux de propagation porte surtout sur les multitrajets, les inter-corrélations, et le masquage du signal. Les multitrajets sont particulièrement gênants dans le cas de milieux urbains, les intercorrélations et le masquage sont par contre plus gênants dans les milieux indoors. Ces phénomènes peuvent impliquer des erreurs dans la position calculée par le récepteur. Pour y remédier, une des solutions est d'augmenter la durée d'observation du signal pour améliorer le rapport signal sur bruit. Mais ceci conduit à des temps d'acquisition beaucoup plus longs. Par conséquent, la qualité commerciale du récepteur est mise en cause vues les contraintes sur le TTFF nécessaires pour fournir une première solution. Ces contraintes en termes de temps ii de traitements sont aussi importantes que les contraintes en termes de précision pour les utilisateurs du GPS. Mais ces deux contraintes vont en général l'une à l'encontre de l'autre. Par conséquent, une solution idéale consistera à réduire le temps d'acquisition sans pour autant affecter la sensibilité du récepteur. Ainsi, dans la suite de l'exposé des méthodes avancées de traitement du signal dans la phase d'acquisition seront présentées. La plupart de ces méthodes vise à réduire le temps total d'acquisition plutôt qu'à améliorer la sensibilité du récepteur: ceci permet de tolérer) le traitement de signaux plus longs - afin d'améliorer la sensibilité - sans augmenter la durée globale de traitement. Ces méthodes seront tout d'abord caractérisées en évaluant les avantages et les inconvénients de chacune d'elles. Une évaluation de performances de ces algorithmes, utilisant des signaux générés avec un Spirent STR4500 sera conduite dans une étape finale de cette étude. ABSTRACT : In the past, in order for GPS (Global Positioning System) to work accurately, the presence of an unobstructed LOS (Line-Of- ight) signal was necessary. Weak signals were not suitable for use because they may have large associated noise and other errors. The expansion of GPS to LBS (Location- ased Services) and other navigation applications all over the world, such as the E-911 and the E-112 mandates in the United States and Europe respectively, changed the paradigm. Consequently a dramatic increase in the need for more and more performant positioning techniques is expected, especially in urban and indoor environments. These rising localization requirements pose a particularly difficult challenge for GPS receivers design. The thesis objective is to evaluate and enhance existing GPS signal acquisition techniques for positioning goals in harsh environments, in the context of AGPS (Assisted GPS). The AGPS system assumes that the GPS receiver is connected to or introduced in a mobile phone. This allows for the transfer of AD (Assistance Data) to the GPS receiver via the GSM (Global System for Mobile communications) cellular network. Amongst others, the AD provides the GPS receiver with the list of visible satellites and estimates of their Dopplers and code delays, thus reducing the search window of these parameters. This work consists in exploring different GPS signal acquisition to reduce the acquisition time or TTFF (Time To First Fix), without affecting the receiver sensitivity. This is done after a prior study of the GPS radio channel. The study starts out with a revue of the GPS system and the GPS transmitted and received signal structure. The acquisition process is then described in details: the classical acquisition is first described in order to proceed afterwards with the impact of the propagation environment on this stage of the signal processing. For this purpose, harsh environments (urban and indoor) are modelled and analysed. This analysis enables to study the problems which encounter the radio frequency signal propagation through such environments. Note that the urban channel is studied using an existing statistical model developed by Alexander Steingass and Andreas Lehner at the DLR (German Aerospace Center) [Steingass et al., 2005]. On the other hand, an indoor channel model was developed by the ESA (European Space Agency) in the frame of a project entitled “Navigation signal measurement campaign for critical environments” and presented in [Pérez-Fontán et al, 2004]. But this model considers a time invariant statistical channel. Consequently, we developed an Indoor model which rather considers a time variant channel, by taking into account temporal variations of some channel parameters, like the transfer function delay and phase. The initial values are however based on the statistical distributions provided by the ESA model. The channels are analysed is terms of multipaths, cross-correlations and signal masking. The multipaths replicas are particularly disturbing in urban environments while the cross-correlations and masking effects are more disturbing in indoor environments. These phenomena may induce errors in the final solution calculated by the receiver. In order to avoid this error, one solution consists in increasing the signal observation duration in order to enhance the signal to noise ratio. But this generally implies longer acquisition time, thus affecting the receiver iv performance, commercially speaking. Indeed, the time requirements are as important as sensitivity requirements for GPS users. However, these two requirements are not generally compatible with each other. Consequently, an ideal solution consists in reducing the acquisition time without greatly affecting the receiver sensitivity. Accordingly, such advanced methods for acquisition signal processing are described next. Most of these methods aim at reducing the total acquisition time, rather than enhancing the receiver sensitivity. This means however that longer signal blocks can be processed (thus enhancing sensitivity) without affecting the global processing duration. At first, each of these methods is evaluated through the description of its advantages and drawbacks. A performance evaluation of these algorithms, using signals generated with a Spirent STR4500, ensues as a final step of this stud

Methods for the integration of combined PET/MR into radiotherapy planning

Despite recent advances in radiotherapy (RT) there are still tumor types for which a high fraction of recurrences is observed following treatment. Limiting factors in current treatment concepts seem to be inaccuracies in image-based tumor delineation and missing consideration of the biological heterogeneity of individual tumors. In this respect, the abundant anatomical and functional information provided by magnetic resonance imaging (MRI) and positron emission tomography (PET) may lead to major advances in RT treatment. Recently available combined PET/MR scanners allow for the acquisition of simultaneous, intrinsically registered PET/MR data, facilitating their combined analysis for the integration into RT. In this thesis, dedicated methods and algorithms for the analysis and integration of the multimodal PET/MR datasets into RT are developed. In the first part, a method for multimodal deformable registration is developed, to enable the spatial transformation of PET/MR data to the computed tomography used for treatment planning. The second part is concerned with the development of an automatic tumor segmentation algorithm, considering PET and MR information simultaneously. In the last part, a correlation analysis of various functional datasets is motivated and performed in order to support the definition of a biologically adapted dose prescription.Trotz jüngster Fortschritte in der Strahlentherapie (ST) gibt es noch immer Tumorarten mit einem hohen Prozentsatz an Rezidiven nach der Behandlung. Limitierende Faktoren in aktuellen Behandlungskonzepten scheinen vor allem Ungenauigkeiten in der bildbasierten Tumorabgrenzung sowie die fehlende Berücksichtigung der biologischen Heterogenität der einzelnen Tumoren zu sein. In dieser Hinsicht erscheint die Einbeziehung der vielfältigen anatomischen und funktionellen Bildgebungsmöglichkeiten der Magnetresonanztomographie (MRT), sowie der Positronenemissionstomographie (PET), in die ST vielversprechend. Seit kurzem verfügbare PET/MR-Scanner erlauben die Akquisition simultaner, intrinsisch registrierter PET/MR-Datensätze, wodurch deren kombinierte Analyse und Integration in die Therapieplanung erleichtert wird. Diese Arbeit befasst sich mit der Entwicklung von dedizierten Methoden und Algorithmen für die Analyse und Integration der multimodalen PET/MR-Datensätze in die ST. Im ersten Teilprojekt wurde eine Methode zur multimodalen deformierbaren Registrierung entwickelt, um die räumliche Transformation der PET/MR-Daten auf die zur Therapieplanung notwendige Computertomographie-Aufnahme zu ermöglichen. Im zweiten Teil wurde ein Algorithmus zur automatischen Tumorsegmentierung unter simultaner Berücksichtigung von PET- und MR-Information entwickelt. Abschließend wurde im dritten Teil eine Korrelationsanalyse der funktionellen PET- und MR-Datensätze motiviert und ausgeführt, um die Definition einer biologisch adaptierten Dosisverschreibung zu unterstützen

Bridge Design to Eurocodes – Worked examples

This document is a Technical Report with worked examples for a bridge structure designed following the Eurocodes. It summarizes important points of the Eurocodes for the design of concrete, steel and composite road bridges, including foundations and seismic design, utilizing a common bridge project as a basis. The geometry and materials of the example bridge as well as the main assumptions and the detailed structural calculations are presented in the first chapter of the report. Each of the subsequent chapters presents the main principles and rules of a specific Eurocode and their application on the example bridge, namely: • The key concepts of basis of design, i.e. design situations, limit states, the single source principle and the combinations of actions (EN 19990); • Permanent, wind, thermal, traffic and fatigue actions on the bridge deck and piers and their combinations (EN 1991); • Bridge deck modeling and structural analysis; • The design of the bridge deck and the piers for the ULS and the SLS, including the second-order effects (EN 1992-2); • The classification of the composite cross-sections, the ULS, SLS and fatigue verifications and the detailed design for creep and shrinkage (EN 1994-2); • The settlement and resistance calculations for the pier, three design approaches for the abutment and the verification of the foundation for the seismic design situation (EN 1997); • The conceptual design for earthquake resistance considering the alternative solutions of slender or squat piers; the latter case involves seismic isolation and design for ductile behavior (EN 1998-1, EN 1998-2). The bridge worked example analyzed in this report was prepared and presented at the workshop “Bridge Design to the Eurocodes” that was held on 4-6 October 2010 in Vienna, Austria. The workshop was organized by JRC with the support of DG ENTR and in collaboration with CEN/TC250/Horizontal Group Bridges, the Austrian Federal Ministry for Transport, Innovation and Technology and the Austrian Standards Institute. The document is part of the Report Series “Support to the implementation, harmonization and further development of the Eurocodes”, prepared by JRC in collaboration with DG ENTR and CEN/TC250 “Structural Eurocodes”.JRC.G.5-European laboratory for structural assessmen

Synthetic Aperture Radar (SAR) Meets Deep Learning

This reprint focuses on the application of the combination of synthetic aperture radars and depth learning technology. It aims to further promote the development of SAR image intelligent interpretation technology. A synthetic aperture radar (SAR) is an important active microwave imaging sensor, whose all-day and all-weather working capacity give it an important place in the remote sensing community. Since the United States launched the first SAR satellite, SAR has received much attention in the remote sensing community, e.g., in geological exploration, topographic mapping, disaster forecast, and traffic monitoring. It is valuable and meaningful, therefore, to study SAR-based remote sensing applications. In recent years, deep learning represented by convolution neural networks has promoted significant progress in the computer vision community, e.g., in face recognition, the driverless field and Internet of things (IoT). Deep learning can enable computational models with multiple processing layers to learn data representations with multiple-level abstractions. This can greatly improve the performance of various applications. This reprint provides a platform for researchers to handle the above significant challenges and present their innovative and cutting-edge research results when applying deep learning to SAR in various manuscript types, e.g., articles, letters, reviews and technical reports

Master\u27s Tools and the Master\u27s House: A Historical Analysis Exploring the Myth of Educating for Democracy in the United States

Over the past forty-years, neoliberal education reform policies in the U.S. have spurred significant resistance, often galvanized by claims that such policies undermine public education as a vital institution of U.S. democracy. Within this narrative, many activists call to “save our schools” and return them to a time when public schools served the common good. With these narratives in mind, I explore the foundational and persistent power structures that characterize the U.S. as a means to reveal the fundamental purpose of its public education system. The questions that guide my research include: (1) With an understanding that capitalism, white supremacy, settler colonialism and heteropatriarchy are inherently inequitable, incredibly violent and undemocratic; how can we expect meaningful and lasting social protections or even emancipation within a nation-state constituted by these structures? (2) Consequently, can we then expect public education - an institution constructed and controlled by these structural forces - to be transformed into an equitable and democratic institution? (3) Is it even possible to attain state protections for the common good within the current global domain of finance capital? In this extensive historical analysis, I examine these questions using a critical theory lens, historical revisionism and discourse analysis to interrogate primary source materials, scholarly work, news stories, policies and industry publications. This research shows that public education is an extension of a duplicitous and despotic cultural political economy and thus has never been, nor ever could be, an institution that serves democratic or emancipatory purposes. I contend that it is imprudent to strive to transform public education to serve democratic purposes. My research makes evident how current education policies are a continuation of the original design of public education, yet modernized to bolster the imperious and ubiquitous interests of global financialization

Traveling Salesman Problem

This book is a collection of current research in the application of evolutionary algorithms and other optimal algorithms to solving the TSP problem. It brings together researchers with applications in Artificial Immune Systems, Genetic Algorithms, Neural Networks and Differential Evolution Algorithm. Hybrid systems, like Fuzzy Maps, Chaotic Maps and Parallelized TSP are also presented. Most importantly, this book presents both theoretical as well as practical applications of TSP, which will be a vital tool for researchers and graduate entry students in the field of applied Mathematics, Computing Science and Engineering

GSI Scientific Report 2009 [GSI Report 2010-1]

Displacement design response spectrum is an essential component for the currently-developing displacement-based seismic design and assessment procedures. This paper proposes a new and simple method for constructing displacement design response spectra on soft soil sites. The method takes into account modifications of the seismic waves by the soil layers, giving due considerations to factors such as the level of bedrock shaking, material non-linearity, seismic impedance contrast at the interface between soil and bedrock, and plasticity of the soil layers. The model is particularly suited to applications in regions with a paucity of recorded strong ground motion data, from which empirical models cannot be reliably developed

30 años (1977-2007): Centro de Investigaciones Ópticas (CIOp)

La edición de este libro fue financiada en parte por la Comisión de Investigaciones Científicas de la Provincia de Buenos Aires