Bayesian algorithms for mobile terminal positioning in outdoor wireless environments

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Hardware for Mobile Positioning : Considerations on Design and Development of Cost-Efficient Solutions

The estimation of a moving agent's position in an unknown environment is a problem formulated in its current form already in the 1980s. Emphasis on localization and mapping problems has grown rapidly in the last two decades driven by the increased computational capability of especially handheld systems and a large number of target applications in various fields, ranging from self-driving cars and geomatics to robotics and virtual/augmented reality. Besides the algorithms for positioning, hardware plays a major role as a backbone for enabling accurate, robust and flexible position estimation solutions. This thesis gives an overview of sensors utilized in mobile positioning with a focus on passive visual-inertial sensors as an alternative to more expensive active-ranging solutions. The main research interest of the thesis is the feasibility of developing and implementing a cost-efficient hardware solution for positioning. Visual, inertial and satellite positioning sensors' advantages, performance parameters, sources of error and physical requirements are considered. Sensor integration and both sensor and system-level calibration in a multisensor setup are discussed. Levels of developer involvement and options for hardware development approaches are presented, mainly ready-made modular solutions, building on top of intermediate products and development from scratch. Hardware development processes are demonstrated by implementing a synchronized visual-inertial positioning system including two pairs of stereo cameras, an inertial measurement unit and a Real-Time Kinematic capable satellite positioning solution. The system acts as a cost-efficient example for options and decisions required on the selection of sensors and computational subsystems supporting the sensor hardware, integration and continuous temporal synchronization of sensors as well as requirements and manufacturing options for system enclosures. Even though the direct costs of the solution seem inexpensive compared to competitive solutions, accounting for the development time and associated risk makes hardware development from scratch less attractive option compared to other approaches. For a proof-of-concept or a case in which a very limited number of end products are produced, implementation from the ground up is most likely time-consuming and thus ends up being an expensive endeavor compared to other approaches. Also, the benefits of control over the details of hardware and integration may not be fully utilized

Analyse des Performances de l’Acquisition des Nouveaux Signaux GNSS

Since the development of the GPS, the global navigation satellite systems (GNSS) have been widely diversified: maintenance, modernization and deployment of new systems such as the European Galileo. In addition, the number of GNSS signals applications, based on the use of GNSS signals, is increasing. To meet these new challenges and requirements, GNSS receivers are constantly evolving. A new trend is the development of software receiver which processes the GNSS signal in a software way unlike hardware receiver, equipping our vehicles, smartphones, for example. This thesis is part of a common project between a laboratory and a company, consisting of the development of a software receiver tracking GPS L1 C/A and Galileo E1 OS. The more specific aim of the thesis is to study the acquisition, first signal processing which provides a rough estimation of the incoming signal parameters. This work focuses particularly the low power signals, an acquisition threshold is set at 27 dB-Hz considered as a representative of urban or degraded environments. It is important to note that the success of the acquisition of such signals should be at least 9 times out of 10, without any aid or knowledge of almanac or ephemeris. Initially, a solid theoretical study of the acquisition performance and sources of degradation is conducted. One of them is the bit transitions due to the presence of the navigation message and the secondary code on pilot component of the new signals. It is thus highlighted the need to use a Transition-Insensitive acquisition method. Secondly, an innovative method, the Double-Block Zero-Padding Transition- Insensitive (DBZPTI) is developed to permit efficiently the acquisition of Galileo E1 OS signal. It takes part in the development of the global acquisition strategy, which should provide an estimate of the Doppler frequency and code delay, fine and reliable, for a satisfactory signal tracking.Depuis le développement du GPS, les systèmes de navigation par satellites (GNSS) se sont largement diversifiés : maintenance, modernisation et déploiement de nouveaux systèmes, comme l’européen Galileo. De plus, le nombre d’applications basées sur l’utilisation de signaux GNSS ne cesse d’augmenter. Pour répondre à ces nouveaux challenges et besoins, les récepteurs GNSS ne cessent d’évoluer. Un nouvel axe est le développement du récepteur logiciel qui présente la particularité d’un traitement logiciel des signaux contrairement au récepteur matériel, équipant nos véhicules, smartphones par exemple. Cette thèse de doctorat s’inscrit dans le projet commun d’un laboratoire et d’une PME consistant au développement d’un récepteur logiciel poursuivant les signaux GPS L1 C/A et Galileo E1 OS. L’objectif plus spécifique de la thèse est d’étudier l’acquisition, première étape du traitement du signal GNSS qui doit fournir une estimation grossière des paramètres du signal entrant. Ce travail vise particulièrement les signaux à faible puissance, un seuil d’acquisition est fixé à 27 dB-Hz pouvant s’apparenter à l’acquisition en milieu urbain ou dégradé. Il est important de noter qu’une des contraintes est de réussir l’acquisition de tels signaux au moins 9 fois sur 10, sans aucune aide extérieure ou connaissance des almanachs ou éphémérides. Dans un premier temps, une solide étude théorique portant sur les performances de l’acquisition et les sources de dégradations est menée. Parmi elles, peuvent être citées, les transitions de bits dues à la présence du message de navigation et du code secondaire sur la voie pilote des nouveaux signaux. Est ainsi mis en lumière la nécessité d’avoir recours à une méthode d’acquisition insensible aux inversions de signe du message de navigation. Dans un deuxième temps, une méthode innovante, le Double-Block Zero-Padding Transition-Insensitive (DBZPTI), est donc développée pour permettre l’acquisition du signal Galileo E1 OS de façon efficiente. Elle prend part au développement de la stratégie globale d’acquisition dont l’objectif est d’avoir en sortie une estimation de la fréquence Doppler et du retard de code du signal entrant, assez fine et fiable pour une satisfaisante poursuite du signa

Interferometric GNSS-R processing : modeling and analysis of advanced processing concepts for altimetry

This PhD dissertation is focused on the use of the opportunity signals from the Global Navigation Satellite Systems (GNSS), that scatter-off the Earth's surface for perform ocean mesoscale altimetry (the so called GNSS-R technique). Specially, this work analyses the capabilities of the interferometric approach (iGNSS-R) originally proposed for PARIS IoD (which will be implemented on GEROS-ISS), comparing its performance with the one obtained by the conventional approach (cGNSS-R). The main content of this PhD dissertation includes: A comprehensive analysis of the GNSS-R cross-correlation waveform properties, analyzing the impact that the observation geometry and system parameters have on the GNSS-R observables, where parameters such as the receiver bandwidth, observation geometry, sea state, and thermal and speckle noises are analyzed. A detailed derivation of the statistics for both the voltage and power cross-correlations (for both conventional and interferometric processing cases) validated all of them with both simulated and real data from ground-based airborne, and spaceborne experiments. Study of the performance model of the altimetry precision based on the Cramer-Rao Bound statistical estimator theory. This study has been carried out for a wide variety of parameters concerning the overall observation system, including instrument, on-board and on-ground processing aspects, for both the conventional and interferometric GNSS-R techniques. Analysis of experimental data from the Typhoon Investigation using GNSS-R Interferometric Signals (TIGRIS) experiment. This analysis has been used to determine and establish the boundaries and capabilities of GNSS-R towards remote sensing of typhoons. In this part, aspects such as the mitigation of the direct cross-talk contamination, GNSS multipath contamination, and preliminary results (including a novel observable) are presented.Este PhD se centra en el uso de la señales GNSS (Global Navigation Satellite Systems) como señales de oportunidad, para realizar altimetría. Es lo que se conoce como GNSS-R (Global Navigation Satellite Systems-Reflectometry). Especialmente este trabajo analiza las principales propiedades del método interferométrico (iGNSS-R) inicialmente propuesto para PARIS-IoD, y que será implementado en GEROS-ISS. comparándolo con el método convencional (cGNSS-R). A continuación se enumeran los principales puntos abordados en esta tesis doctoral: Se ha realizado un exhaustivo y detallado análisis de las propiedades de las waveforms, evaluando la influencia de la geometría (altitud, ángulo de incidencia, estado del mar, etc), y de los principales parámetros a nivel de instrumento sobre las waveforms. Así mismo se ha analizado el impacto del ancho de banda del receptor, y del ruido térmico y speckle. Por otra parte, se han derivado las estadísticas (matrices de covarianzas) tanto para las waveforms complejas, como para las waveforms de potencia, considerando el método convencional, y el interferométrico. Las diferentes estadísticas o matrices de covarianzas han sido validadas usando datos reales procedentes de diferentes experimentos y datos simulados, para diferentes escenarios (.espacio, aerotransportado, ground-base). Dichas matrices de covarianza, posteriormente han sido usadas para calcular la precisión altimétrica, basada en el uso de estimadores estadísticos, como es el Cramer-Rad Bound. Dicho estudio ha sido realizado considerando un amplio número de parámetros, tanto para el método convencional como para el interferométrico, comparando el performance de ambas técnicas, y realizando una primera estimación de la precisión altimétrica que se obtendría para una misión espacial como PARIS-IoD. Por último se han analizado datos de la campaña experimental TIGRIS (Typhoon Investigation using GNSS-R Interferometric Signal). con dicho analisis se han estudio la capacidad de la técnica GNSS-R para monitorizar y detectar huracanes. Este análisis incluye aspectos como la mitigación de la contaminación procendente de la señal directa, y del multipath ocasionado por las diferentes señales GNSS. Al mismo tiempo durante este análisis un nuevo observable se ha propuesto