Codes Cross-Correlation Impact on S-curve Bias and Data-Pilot Code Pairs Optimization for CBOC Signals

The aim of this paper is to analyze the impact of spreading codes cross-correlation on code tracking performance, and to optimize the data-pilot code pairs of Galileo E1 Open Service (OS) Composite Binary Offset Carrier (CBOC) signals. The distortion of the discriminator function (i.e., S-curve), due to data and pilot spreading codes cross-correlation properties, is evaluated when only the data or pilot components of CBOC signals are tracked, considering the features of the modulation schemes. Analyses show that the S-curve bias also depends on the receiver configuration (e.g., the tracking algorithm and correlator spacing). In this paper, two methods are proposed to optimize the data-pilot code pairs of Galileo E1 OS. The optimization goal is to obtain minimum average S-curve biases when tracking only the pilot components of CBOC signals for the specific correlator spacing. The S-curve biases after optimization processes are analyzed and compared with the un-optimized results. It is shown that the optimized data-pilot code pairs could significantly mitigate the intra-channel (i.e., data and pilot) codes cross-correlation，and then improve the code tracking performance of CBOC signals

Performance of Deconvolution Methods in Estimating CBOC-Modulated Signals

Multipath propagation is one of the most difficult error sources to compensate in global navigation satellite systems due to its environment-specific nature. In order to gain a better understanding of its impact on the received signal, the establishment of a theoretical performance limit can be of great assistance. In this paper, we derive the Cramer Rao lower bounds (CRLBs), where in one case, the unknown parameter vector corresponds to any of the three multipath signal parameters of carrier phase, code delay, and amplitude, and in the second case, all possible combinations of joint parameter estimation are considered. Furthermore, we study how various channel parameters affect the computed CRLBs, and we use these bounds to compare the performance of three deconvolution methods: least squares, minimum mean square error, and projection onto convex space. In all our simulations, we employ CBOC modulation, which is the one selected for future Galileo E1 signals

Performance of Deconvolution Methods in Estimating CBOC-Modulated Signals

Multipath propagation is one of the most difficult error sources to compensate in global navigation satellite systems due to its environment-specific nature. In order to gain a better understanding of its impact on the received signal, the establishment of a theoretical performance limit can be of great assistance. In this paper, we derive the Cramer Rao lower bounds (CRLBs), where in one case, the unknown parameter vector corresponds to any of the three multipath signal parameters of carrier phase, code delay, and amplitude, and in the second case, all possible combinations of joint parameter estimation are considered. Furthermore, we study how various channel parameters affect the computed CRLBs, and we use these bounds to compare the performance of three deconvolution methods: least squares, minimum mean square error, and projection onto convex space. In all our simulations, we employ CBOC modulation, which is the one selected for future Galileo E1 signals

Advanced Signal Processing in Multi-mode Multi-frequency Receivers for Positioning Applications

The demands for positioning services are increasing steadily since the first Global Navigation Satellite Systems (GNSS), NAVSTAR Global Positioning System, also known as GPS was introduced in the early 80s. The increasing demands for positioning services have accelerated the advent of other satellite-based systems, such as the Russian GLONASS, the European Galileo and the Chinese Compass/Beidou-2 system. However, the GNSS fail to provide accurate positioning solution indoors, which is one of the demanding environments. Therefore developing indoor positioning techniques has become a very important topic, mainly in terms of continuity of services and seamless localization. This has led to many theoretical and experimental studies in this field using a wide range of techniques, from purely GNSS approach to methods employing networks of physical sensors or Wireless Local Area Networks (WLAN). These systems, together with satellite­ based ones, all have their advantages, but they also face different challenges. Most of these are related to the physical channel containing various error sources that affect the quality of the received signal and degrade the receiver's positioning performance. The users will benefit from having multiple systems with more satellites and different positioning methods available. In this way, the positioning performance against the errors and challenges will be superior to having only a single system. This can be realized by the multi-mode multi-frequency receiver, which is able to process jointly the new signals, modulations and frequencies introduced in modem positioning systems. The work presented in this thesis focuses on the signal processing part for research and development of such a receiver and outlines the potential capability of the future receivers for positioning applications. More specifically, this thesis studies the narrowband interference effects on the future GNSS signals in both single-frequency and multi­ frequency receivers, makes a performance analysis of dual-frequency ionosphere delay estimation methods under strong multipath errors and presents an optimized multi­ correlator based multipath mitigation technique for future GNSS signals. In addition, the performance of four multipath mitigation techniques under time-varying, measurement­ based channel models is compared. Finally, a new Non-Line-of-Sight identification based on non-GNSS signal is proposed for improving the path-loss modeling based indoor positioning in multi-mode multi-frequency receivers. This thesis consists of an introductory part with live chapters and a compendium of six original publications ([I] - [VI]), attached as appendices

Adaptive Tracking Techniques in Non-Stationary Environments

The continuously changing environments have been the main challenge for classical GNSS receiver implementations, as they can have a great impact on signal tracking performance and positioning. For this reason techniques capable of mitigating the impact of time-varying phenomena by adapting to changing conditions, thus improving performance are of great interest. This study reports the benefits of using adaptive techniques for standalone GNSS receivers in three different scenarios. The first scenario compares an adaptive Kalman filter against a classical DLL/PLL architecture in interference environments with user dynamics. The second scenario uses a multipath propagation channel to test alternative carrier tracking architectures which provide better results in terms of robustness. The third scenario uses the same multipath propagation channel to test the adaptive switching technique, 2-Step, in order to evaluate its capacity of guaranteeing and maintaining unambiguous tracking for BOC-type modulations. In order to assess the performance of these techniques a semi-analytical platform has been used. The results presented here show the benefits and trade-offs of different techniques taking into account different propagation channels and scenarios

Delay Trackers for Galileo CBOC Modulated Signals and Their Simulink-based Implementations

Galileo will be the future European Global Navigation Satellite Systems (GNSSs), which is going to provide high availability, increased accuracy and various location services. This new satellite system proposes the use of a new modulation, namely the Composite Binary Offset Carrier (CBOC) modulation, which motivates the research on GNSS receiver with this new modulation. Code tracking is one of the main functions in a GNSS receiver and its task is to give an accurate estimation of the code delay. The accuracy of this code delay estimation is strictly connected with the accuracy of user position computation. One typical code tracking structure is the code tracking loop. The code tracking algorithms or delay trackers used in code tracking loop are the main aspect, which affects the performance of code tracking loop. Various typical delay trackers are studied in this thesis. Simulation is one important issue in the design and analysis of any communication system or navigation system. One method for testing delay trackers and effects from different tracking algorithms can be realized in the simulation tool, such as a software receiver. The simulation tool makes it convenient to test various algorithms used in the receiver and to investigate the receiver performance before the algorithms are built in the real devices. On the other hand, the implementation of delay trackers in a software receiver can be also helpful for further developing the simulation tool. The goal of this thesis has been to develop and analyze the implementations of various code delay trackers for Galileo systems via Simulink tool. The analysis has also helped to further develop the model in order to include realistic receiver constraints for mass-market application. The performance of the delay trackers is measured in terms of Root Mean Square Error (RMSE), tracking error variance and Multipath Error Envelopes (MEEs). /Kir1

Contrôle d intégrité appliqué à la réception des signaux GNSS en environnement urbain

L intégrité des signaux GNSS est définie comme la mesure de la confiance qui peut être placée dans l exactitude des informations fournies par le système de navigation. Bien que le concept d intégrité GNSS a été initialement développé dans le cadre de l aviation civile comme une des exigences standardisées par l Organisation de l Aviation Civile Internationale (OACI) pour l utilisation du GNSS dans les systèmes de Communication, Navigation, et Surveillance / Contrôle du Trafic Aérien (CNS/ATM), un large éventail d applications non aéronautiques ont également besoin de navigation par satellite fiable avec un niveau d intégrité garanti. Beaucoup de ces applications se situent en environnement urbain. Le contrôle d intégrité GNSS est un élément clé des applications de sécurité de la vie (SoL), telle que l aviation, et des applications exigeant une fiabilité critique comme le télépéage basé sur l utilisation du GNSS, pour lesquels des erreurs de positionnement peuvent avoir des conséquences juridiques ou économiques. Chacune de ces applications a ses propres exigences et contraintes, de sorte que la technique de contrôle d intégrité la plus appropriée varie d une application à l autre. Cette thèse traite des systèmes de télépéage utilisant GNSS en environnement urbain. Les systèmes de navigation par satellite sont l une des technologies que l UE recommande pour le Service Européen de Télépéage Electronique (EETS). Ils sont déjà en cours d adoption: des systèmes de télépéage pour le transport poids lourd utilisant GPS comme technologie principale sont opérationnels en Allemagne et en Slovaquie, et un système similaire est envisagé en France à partir de 2013. À l heure actuelle, le contrôle d intégrité GPS s appuie sur des systèmes d augmentation (GBAS, SBAS, ABAS) conçus pour répondre aux exigences de l OACI pour les opérations aviation civile. C est la raison pour laquelle cette thèse débute par une présentation du concept d intégrité en aviation civile afin de comprendre les performances et contraintes des systèmes hérités. La thèse se poursuit par une analyse approfondie des systèmes de télépéage et de navigation GNSS en milieu urbain qui permets de dériver les techniques de contrôle d intégrité GNSS les plus adaptées. Les algorithmes autonomes de type RAIM ont été choisis en raison de leur souplesse et leur capacité d adaptabilité aux environnements urbains. Par la suite, le modèle de mesure de pseudodistances est élaboré. Ce modèle traduit les imprécisions des modèles de correction des erreurs d horloge et d ephemeride, des retards ionosphériques et troposphériques, ainsi que le bruit thermique récepteur et les erreurs dues aux multitrajets. Les exigences d intégrité GNSS pour l application télépéage sont ensuite dérivées à partir de la relation entre les erreurs de positionnement et leur effets dans la facturation finale. Deux algorithmes RAIM sont alors proposés pour l application péage routier. Le premier est l algorithme basé sur les résidus de la solution des moindres carrés pondérés (RAIM WLSR), largement utilisé dans l aviation civile. Seulement, un des principaux défis de l utilisation des algorithmes RAIM classiques en milieux urbains est un taux élevé d indisponibilité causé par la mauvaise géométrie entre le récepteur et les satellites. C est pour cela que un nouvel algorithme RAIM est proposé. Cet algorithme, basé sur le RAIM WLSR, est conçu de sorte à maximiser l occurrence de fournir un positionnement intègre dans un contexte télépéage. Les performances des deux algorithmes RAIM proposés et des systèmes de télépéage associés sont analysés par simulation dans différents environnements ruraux et urbains. Dans tous les cas, la disponibilité du nouvel RAIM est supérieure à celle du RAIM WLSR.Global Navigation Satellite Systems (GNSS) integrity is defined as a measure of the trust that can be placed in the correctness of the information supplied by the navigation system. Although the concept of GNSS integrity has been originally developed in the civil aviation framework as part of the International Civil Aviation Organization (ICAO) requirements for using GNSS in the Communications, Navigation, and Surveillance / Air Traffic Management (CNS/ATM) system, a wide range of non-aviation applications need reliable GNSS navigation with integrity, many of them in urban environments. GNSS integrity monitoring is a key component in Safety of Life (SoL) applications such as aviation, and in the so-called liability critical applications like GNSS-based electronic toll collection, in which positioning errors may have negative legal or economic consequences. At present, GPS integrity monitoring relies on different augmentation systems (GBAS, SBAS, ABAS) that have been conceived to meet the ICAO requirements in civil aviation operations. For this reason, the use of integrity monitoring techniques and systems inherited from civil aviation in non-aviation applications needs to be analyzed, especially in urban environments, which are frequently more challenging than typical aviation environments. Each application has its own requirements and constraints, so the most suitable integrity monitoring technique varies from one application to another. This work focuses on Electronic Toll Collection (ETC) systems based on GNSS in urban environments. Satellite navigation is one of the technologies the directive 2004/52/EC recommends for the European Electronic Toll Service (EETS), and it is already being adopted: toll systems for freight transport that use GPS as primary technology are operational in Germany and Slovakia, and France envisages to establish a similar system from 2013. This dissertation begins presenting first the concept of integrity in civil aviation in order to understand the objectives and constraints of existing GNSS integrity monitoring systems. A thorough analysis of GNSS-based ETC systems and of GNSS navigation in urban environments is done afterwards with the aim of identifying the most suitable road toll schemes, GNSS receiver configurations and integrity monitoring mechanisms. Receiver autonomous integrity monitoring (RAIM) is chosen among other integrity monitoring systems due to its design flexibility and adaptability to urban environments. A nominal pseudorange measurement model suitable for integrity-driven applications in urban environments has been calculated dividing the total pseudorange error into five independent error sources which can be modelled independently: broadcasted satellite clock corrections and ephemeris errors, ionospheric delay, tropospheric delay, receiver thermal noise (plus interferences) and multipath. In this work the fault model that includes all non-nominal errors consists only of major service failures. Afterwards, the GNSS integrity requirements are derived from the relationship between positioning failures and toll charging errors. Two RAIM algorithms are studied. The first of them is the Weighted Least Squares Residual (WLSR) RAIM, widely used in civil aviation and usually set as the reference against which other RAIM techniques are compared. One of the main challenges of RAIM algorithms in urban environments is the high unavailability rate because of the bad user/satellite geometry. For this reason a new RAIM based on the WLSR is proposed, with the objective of providing a trade-off between the false alarm probability and the RAIM availability in order to maximize the probability that the RAIM declares valid a fault-free position. Finally, simulations have been carried out to study the performance of the different RAIM and ETC systems in rural and urban environments. In all cases, the availability obtained with the novel RAIM improve those of the standard WLSR RAIM.TOULOUSE-INP (315552154) / SudocSudocFranceF

Integrity monitoring applied to the reception of GNSS signals in urban environments

L’intégrité des signaux GNSS est définie comme la mesure de la confiance qui peut être placée dans l’exactitude des informations fournies par le système de navigation. Bien que le concept d’intégrité GNSS a été initialement développé dans le cadre de l’aviation civile comme une des exigences standardisées par l’Organisation de l’Aviation Civile Internationale (OACI) pour l’utilisation du GNSS dans les systèmes de Communication, Navigation, et Surveillance / Contrôle du Trafic Aérien (CNS/ATM), un large éventail d’applications non aéronautiques ont également besoin de navigation par satellite fiable avec un niveau d’intégrité garanti. Beaucoup de ces applications se situent en environnement urbain. Le contrôle d’intégrité GNSS est un élément clé des applications de sécurité de la vie (SoL), telle que l’aviation, et des applications exigeant une fiabilité critique comme le télépéage basé sur l’utilisation du GNSS, pour lesquels des erreurs de positionnement peuvent avoir des conséquences juridiques ou économiques. Chacune de ces applications a ses propres exigences et contraintes, de sorte que la technique de contrôle d’intégrité la plus appropriée varie d’une application à l’autre. Cette thèse traite des systèmes de télépéage utilisant GNSS en environnement urbain. Les systèmes de navigation par satellite sont l’une des technologies que l’UE recommande pour le Service Européen de Télépéage Electronique (EETS). Ils sont déjà en cours d’adoption: des systèmes de télépéage pour le transport poids lourd utilisant GPS comme technologie principale sont opérationnels en Allemagne et en Slovaquie, et un système similaire est envisagé en France à partir de 2013. À l’heure actuelle, le contrôle d’intégrité GPS s’appuie sur des systèmes d´augmentation (GBAS, SBAS, ABAS) conçus pour répondre aux exigences de l’OACI pour les opérations aviation civile. C´est la raison pour laquelle cette thèse débute par une présentation du concept d’intégrité en aviation civile afin de comprendre les performances et contraintes des systèmes hérités. La thèse se poursuit par une analyse approfondie des systèmes de télépéage et de navigation GNSS en milieu urbain qui permets de dériver les techniques de contrôle d’intégrité GNSS les plus adaptées. Les algorithmes autonomes de type RAIM ont été choisis en raison de leur souplesse et leur capacité d´adaptabilité aux environnements urbains. Par la suite, le modèle de mesure de pseudodistances est élaboré. Ce modèle traduit les imprécisions des modèles de correction des erreurs d’horloge et d’ephemeride, des retards ionosphériques et troposphériques, ainsi que le bruit thermique récepteur et les erreurs dues aux multitrajets. Les exigences d’intégrité GNSS pour l’application télépéage sont ensuite dérivées à partir de la relation entre les erreurs de positionnement et leur effets dans la facturation finale. Deux algorithmes RAIM sont alors proposés pour l’application péage routier. Le premier est l’algorithme basé sur les résidus de la solution des moindres carrés pondérés (RAIM WLSR), largement utilisé dans l’aviation civile. Seulement, un des principaux défis de l’utilisation des algorithmes RAIM classiques en milieux urbains est un taux élevé d’indisponibilité causé par la mauvaise géométrie entre le récepteur et les satellites. C’est pour cela que un nouvel algorithme RAIM est proposé. Cet algorithme, basé sur le RAIM WLSR, est conçu de sorte à maximiser l’occurrence de fournir un positionnement intègre dans un contexte télépéage. Les performances des deux algorithmes RAIM proposés et des systèmes de télépéage associés sont analysés par simulation dans différents environnements ruraux et urbains. Dans tous les cas, la disponibilité du nouvel RAIM est supérieure à celle du RAIM WLSR. ABSTRACT : Global Navigation Satellite Systems (GNSS) integrity is defined as a measure of the trust that can be placed in the correctness of the information supplied by the navigation system. Although the concept of GNSS integrity has been originally developed in the civil aviation framework as part of the International Civil Aviation Organization (ICAO) requirements for using GNSS in the Communications, Navigation, and Surveillance / Air Traffic Management (CNS/ATM) system, a wide range of non-aviation applications need reliable GNSS navigation with integrity, many of them in urban environments. GNSS integrity monitoring is a key component in Safety of Life (SoL) applications such as aviation, and in the so-called liability critical applications like GNSS-based electronic toll collection, in which positioning errors may have negative legal or economic consequences. At present, GPS integrity monitoring relies on different augmentation systems (GBAS, SBAS, ABAS) that have been conceived to meet the ICAO requirements in civil aviation operations. For this reason, the use of integrity monitoring techniques and systems inherited from civil aviation in non-aviation applications needs to be analyzed, especially in urban environments, which are frequently more challenging than typical aviation environments. Each application has its own requirements and constraints, so the most suitable integrity monitoring technique varies from one application to another. This work focuses on Electronic Toll Collection (ETC) systems based on GNSS in urban environments. Satellite navigation is one of the technologies the directive 2004/52/EC recommends for the European Electronic Toll Service (EETS), and it is already being adopted: toll systems for freight transport that use GPS as primary technology are operational in Germany and Slovakia, and France envisages to establish a similar system from 2013. This dissertation begins presenting first the concept of integrity in civil aviation in order to understand the objectives and constraints of existing GNSS integrity monitoring systems. A thorough analysis of GNSS-based ETC systems and of GNSS navigation in urban environments is done afterwards with the aim of identifying the most suitable road toll schemes, GNSS receiver configurations and integrity monitoring mechanisms. Receiver autonomous integrity monitoring (RAIM) is chosen among other integrity monitoring systems due to its design flexibility and adaptability to urban environments. A nominal pseudorange measurement model suitable for integrity-driven applications in urban environments has been calculated dividing the total pseudorange error into five independent error sources which can be modelled independently: broadcasted satellite clock corrections and ephemeris errors, ionospheric delay, tropospheric delay, receiver thermal noise (plus interferences) and multipath. In this work the fault model that includes all non-nominal errors consists only of major service failures. Afterwards, the GNSS integrity requirements are derived from the relationship between positioning failures and toll charging errors. Two RAIM algorithms are studied. The first of them is the Weighted Least Squares Residual (WLSR) RAIM, widely used in civil aviation and usually set as the reference against which other RAIM techniques are compared. One of the main challenges of RAIM algorithms in urban environments is the high unavailability rate because of the bad user/satellite geometry. For this reason a new RAIM based on the WLSR is proposed, with the objective of providing a trade-off between the false alarm probability and the RAIM availability in order to maximize the probability that the RAIM declares valid a fault-free position. Finally, simulations have been carried out to study the performance of the different RAIM and ETC systems in rural and urban environments. In all cases, the availability obtained with the novel RAIM improve those of the standard WLSR RAIM

Signal Quality Monitoring of GNSS Signals Using a Chip Shape Deformation Metric

The Global Navigation Satellite System continues to become deeply em-bedded within modern civilization, and is depended on for confident, accurate navigation information. High precision position and timing accuracy is typically achieved using differential processing, however these systems provide limited compensation for distortions caused by multi-path or faulty satellite hardware. Signal Quality Monitoring (SQM) aims to provide confidence in a receivers Position, Navigation, and Timing solution and to offer timely warnings in the event that signal conditions degrade to unsafe levels. The methods presented in this document focus on implementing effective SQM using low-cost Commercial Off-the-Shelf equipment, a Software Defined Radio, and a typical software receiver architecture that tracks the Galileo E1C signals and the Global Positioning System L1 Coarse-Acquisition signals. Techniques are centered on acquiring and discriminating signal chip shapes with a goal of identifying both 1) clean and 2) deformed signals. The demonstrated identification method is relevant to the growing significance of SQM for SoL applications while providing benefit for confidently monitoring received GNSS signal integrity without requiring specialized receiver hardware