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ION GNSS + 2022, Denver, ETATS-UNIS, 21-/09/2022 - 23/09/2022; In safety-critical applications, the vulnerability of the Global Navigation Satellite System (GNSS) to radio frequency interferences (RFIs) is a major concern. The development of a fail-safe and robust localization system now necessarily requires detection and mitigation of such interferences, which has increased with the proliferation of wireless systems and easy access to personal privacy devices (PPD) also known as jammers. Moreover, the advent of software-defined radio (SDR) permitting the transmission of customized and more complex signals has further complicated this problem. This paper provides an in-depth comparison of interference mitigation techniques at multiple levels primarily focusing on the safety perspective at the position level. For this purpose, the classical adaptive notch filter (ANF) and the wavelet packet decomposition method are applied to mitigate the effects of interference. This comparative study aims to assess the performance of these mitigation techniques at multiple levels (frequency estimation, acquisition, tracking and position). However, the main goal for the final user is to study the impact on key performance indicators (KPIs) such as accuracy, availability, and safety. Furthermore, two cases are considered: 1): interference in the absence of any mitigation strategy and after applying interference mitigation technique at the pre-correlation level. The complete study is presented for two different types of time-varying continuous wave (CW) interferenc.e signals namely frequency hopping and the chirp signal.

ION ITM 2022 - International Technical Meeting of Institute of Navigation, Long Beach, CA, ETATS-UNIS, 25-/01/2022 - 27/01/2022; Localization function for an advanced intelligent transport system, such as an autonomous vehicle, must ensure various operational requirements such as safety, accuracy, availability and continuity of service, anytime, anywhere, at a reasonable cost. Global Navigation Satellite System (GNSS) have many advantages insofar as they present the most accessible technology to the user to determine its position with a certain accuracy without prior knowledge. However, in an environment where signal reception may not be optimal especially due to phenomena such as satellite blockage, multipath, intentional or unintentional interferences and spoofing, it becomes very challenging to meet all these requirements, especially those related to operational safety. The latter is measured by evaluating the integrity of the localization function. It can be evaluated through a Protection Level, which is calculated by the receiver to self-monitor its integrity, also called RAIM (Receiver Autonomous Integrity Monitoring). In the literature, integrity in presence of multipath and NLOS has been extensively investigated [1] as well interference detection and mitigation solutions [2]. However, the impact of interference presence and mitigation on integrity monitoring is not deeply addressed yet. In this study, we evaluate some key performance indicators (KPI's) for GNSS users. These indicators will be evaluated for three different cases; 1) when no interference is applied and clean GNSS signals are processed. 2) In the presence of interference but without any mitigation technique. 3) After applying a mitigation technique at the pre-correlation level to filter the interference signal. The mitigation technique relies on state-of-the-art Notch filters provided by a Septentrio receiver. The interference signals are generated in the laboratory to produce disturbances in the GNSS band. Thus, and thanks to the a priori knowledge of the true position, it is possible to establish the Stanford diagrams for these cases. A deep analysis of performance in the presence and absence of interferences and in the presence and absence of a mitigation technique allows the first conclusions to be drawn on the evolution of accuracy, availability and operational safety indicators. The preliminary results reveal the importance of considering, from the design phase of the localization function, the possibility of dealing with this phenomenon, in particular in the measurement weighting model to use for enhanced performance.

L'utilisation des GNSS (Global Navigation Satellite System) dans le milieu ferroviaire est d'ores et déjà une réalité sur le terrain. Mais les défis pour l'intégration des technologies de positionnement par satellites dans des systèmes complexes de contrôle-commande et de gestion du trafic ferroviaire restent nombreux.

The ERSAT-Galileo Game Changer research project, which concluded last November, has laid the foundations for GNSS satellite location technology to support train positioning on secondary railways, potentially reducing the cost of ERTMS deployment.This paper summarizes the main contributions of the project and the perspectives.

WCRR 2019, 12th World Congress on Railway Research, Tokyo, JAPON, 28-/10/2019 - 01/11/2019; The use of GNSS positioning into the ERTMS/ETCS has been identified as the technology for supporting the detection of Virtual Balises (VB). However, the presence of local GNSS threats (e.g. multipath, non-line-of-sight (NLOS) or interference) that may not be detectable by a local or wide area augmentation network, can potentially lead to unbounded errors in the pseudorange measurement and ultimately to an error in the VB position that cannot be bounded with the required integrity. In order to prevent a priori the risk of this hazardous situation, VB must be located in areas there are no local threats that may lead a Virtual Balise Reader (VBR) on board the train to dynamically estimate unbounded virtual balise position errors. The ERSAT-GGC project has been funded to tackle with this challenge. This paper aims to present the techniques and methods developed to characterize track areas to know a priori which track portions are suitable for placing VBs. They will rely on basic equipment that every stakeholder shall be able to install and use, composed of a COTS GNSS receiver providing raw data and, when necessary, a spectrum analyzer. The paper describes and illustrates the selected techniques.

WCRR 2019, 12th World Congress on Railway Research, Railway Research to Enhance the Customer Experience, Tokyo, JAPON, 28-/10/2019 - 01/11/2019; Innovative technologies enable new approaches for train control, command and signaling systems. E.g. digitalization and automation lead to completely new concepts. The partner RAILENIUM, NSL, CEIT and DLR have founded the consortium Smart Rail Control (SmartRaCon) to develop new concepts, approachs and technologies for the train control, command and signaling systems of the future. In this contribution the developments in the areas of communication, localization and train integrity will be discussed. For the communication the next generation of mobile radio 5G is in the focus with the capability to support software defined networks and radio as well as virtualization potentials. For localization and train integrity supervision algorithms for the fusion of sensor data and digital maps are the key elements. E.g. Global Navigation Satellite Systems (GNSS) together with complementary sensors can be used to achieve a safe and reliable localization. This concept again can serve as a core of a end-of-train device for train integrity monitoring. Further elements like the traffic management or moving block as well as procedural aspects like simulation-based testing are subject of the SmartRaCon concepts and are related to the issues discussed here. The architectural concept to integrate all those elements is based on the idea to use components and software common-off-the-shelf (COTS) and to integrate them into a railway network in a modular way.

WCRR 2019, 12th World Congress on Railway Research, Tokyo, JAPON, 28-/10/2019 - 01/11/2019; New technologies such as GNSS-based positioning solutions will contribute to the modernization and efficiency enhancement of the railway system. Its capacity to provide a global absolute position without any infrastructure to be supported by the user at reasonable cost makes GNSS a game changer for rail. However, in order to reach the high-level performance requirements needed to apply these technologies to safety-critical applications, and in particular, for the use of virtual balises, some solutions need to ensure their accuracy, robustness and safety. Coming from aeronautics experience, the RAIM (Receiver Autonomous Integrity Monitoring) can help reducing inaccuracy by detecting and excluding faulty measurements and bounding residual errors. In this paper, we intend to demonstrate how the combination of weighting schemes and FDE (Fault Detection and Exclusion) can help the system to enhance GNSS performance in a railway environment where multipath, non-line of sight signals and interferences can occur. Some results based on real data are presented in order to quantify the benefit. Application of such techniques will help designing future on-board location units by evaluating their potential performance before deciding the level of hybridization that will be mandatory to ensure continuity of service and compensate the drawbacks of GNSS in harsh environments.

This is the deliverable D4.5 Process Execution Report of the ERSAT GGC project. This document reports the execution of the track area classification process developed during the work package WP4 Track Survey and Track Classification along with the main outcomes and results obtained during this process. The goal of WP4 is to set up a standard measurement and classification system that is able to provide a prediction of the expected presence of GNSS hazard causes and degraded performance to be expected at a given track area, in order to enable the evaluation if the specific environment is suitable or not to place virtual balises or on the contrary should be discarded beforehand. In this document, we detail the results of applying the classification standard process, by means of the developed software Toolset to the measurement data collected in the three measurements campaigns during ERSAT GGC project. This execution report addressed the main important aspects that need to be carried out for the correct application of the classification process and the results obtained with the data collected.

IEEE RTSI 2018, 4th International Forum on Research and Technologies for Society and Industry, Palerme, ITALIE, 10-/09/2018 - 13/09/2018; Global Navigation Satellite Systems (GNSS) have continually involved in our daily life in the past decades. Among all these GNSS-based applications, there is an increasing number of GNSS-based urban transport applications, especially the critical liability ones, such as the Electronic Toll Collection (ETC) and the Intelligent Transport System (ITS). For these GNSS-based applications, not only positioning accuracy but also its reliability is required. Latter has attracted more and more attention from urban GNSS users. Yet urban environments present great challenges for common commercial GNSS receivers since the existence of local effects such as multipath and the Non-Line-of-Sight (NLOS) receptions. The main objective of this paper is to investigate the integrity performance one can expect from a lowcost common GNSS receiver. Under this framework, this paper proposes an innovation-based integrity monitoring scheme by using an Extended Kalman Filter (EKF) with the help of carrierpower-to-noise ratio (C/N0) weighting. The derivations of the Horizontal Protection Level (HPL) for the EKF innovation-based integrity monitoring is also presented in detail. The accuracy and integrity performances are evaluated with real GPS data collected in urban environments. Compared to the classic residual-based snapshot Receiver Autonomous Integrity Monitoring (RAIM), the innovation-based EKF integrity monitoring scheme presents more advantages in terms of accuracy and integrity. With the real dataset collected in urban canyon of Nantes center, the results show that the average size of horizontal position error has been reduced by 1.15 meter with the proposed approach compared to the classic weighted RAIM, the median size of HPL has been reduced by 7.5 meters and the algorithm availability is 100% instead of 98.57%.

Fourth International Conference on Railway Technology: Research, Development and Maintenance, Sitges, ESPAGNE, 03-/09/2018 - 07/09/2018; Présentation de l'architecture développée pour le projet ERSAT GGC utilisant l'image pour la caractérisation de la réception des signaux GNSS le long d'une voie.

TRA 2018, 7th Transport Research Arena, Vienne, AUTRICHE, 16-/04/2018 - 19/04/2018; Cet article présente un résumé de l'état de l'art réalisé pour le projet EU STARS sur l'utilisation d'EGNOS dans le domine ferroviaire. GNSS is expected to help the railway system to be modernized. However, such localization applications requires a high level of accuracy and safety that deserve to use the best potential of satellite-based technologies. The augmentation systems, as the satellite-based augmentation system EGNOS (European Geostationary Navigation Overlay Service), helps to increase the nominal performance. One of the tasks of the EU STARS project deals with the study of the usability of EGNOS in railway environments. EGNOS has indeed been developed driven by the requirements of civil aviation safety procedures in conditions for signal reception that differ from the railway ones. In this paper, after introducing the needs and the basic principles of these systems, we describe the limitations caused by the specificities of railways and some solutions perspectives proposed by the project.

Au cours des dernières décennies, de plus en plus d'applications de transport urbain basées sur les systèmes de positionnement par satellites (GNSS) ont vu le jour. Des applications exigent une fiabilité critique comme le télépéage basé sur l'utilisation du GNSS, pour lesquelles des erreurs de positionnement peuvent entraîner de graves conséquences. Pourtant, les environnements urbains présentent de grands défis pour le positionnement GNSS en raison de l'existence des trajets multiples et de signaux NLOS (None-Line-of-Sight). Cet article présente un système complet de surveillance de l'intégrité pour les applications de transport urbain. Tout d'abord, les erreurs de mesure sont mieux caractérisées en utilisant des modèles de pondération tirant parti d'un modèle de multi-trajet urbain (UMM). Deuxièmement, différentes méthodes de détection et d'exclusion de défauts (FDE) sont appliquées afin de détecter et d'exclure des mesures erronées. Enfin, les niveaux de protection horizontale (HPL) sont calculés et la probabilité d'événements redoutés (MI) est analysée., In the past decades, more and more Global Navigation Satellite Systems (GNSS)-based urban transport applications emerged. Among these applications, the liability critical ones, such as Electronic Toll Collection (ETC) and Pay as you Drive insurance, have high requirements for positioning accuracy as well as integrity since large errors can lead to serious consequences. Yet urban environments present great challenges for GNSS positioning due to the existence of multipath effects and None-Line-of-Sight (NLOS) receptions. This article presents a complete integrity monitoring scheme for urban transport applications. This scheme is realized in several levels. Firstly, measurement errors are better characterized by using weighting models with the help of an Urban Multipath Modeling (UMM). Secondly, several Fault Detection and Exclusion (FDE) methods are applied in order to detect and exclude erroneous measurements. Finally, Horizontal Protection Levels (HPLs) are computed and the probability of Misleading Information (MI) is analyzed.

RAIL Live 2018, Bilbao, ESPAGNE, 18-/04/2018 - 19/04/2018; Présentation de l'état de l'art des applications GNSS pour le ferroviaire, des enjeux et des verrous. Industry update: the state of GNSS-based solutions and projects for rail. Understanding the implications of GNSS for the rail industry: optimising operations and reducing costs. Remaining issues and next short term steps: developing tools and methodology to enhance and prove both the reliability and safety of GNSS-based positioning solutions

International Congress on High-speed Rail: technologies and long term impacts, Madrid, ESPAGNE, 04-/10/2017 - 06/10/2017; High Speed Railway services have shown that Railways are a competitive and, at the same time, an environmentally friendly transport system. The next level of improvement will be a higher degree of automation, with partial or complete automatic train operation up to fully automatic unattended driverless operation to reduce energy consumption and noise, as well as improving punctuality and comfort. Based on extensive experience in separated railway systems such as Metros, VAL (Véhicule automatique léger) and subways, today's discussion focuses on the fully automatic train operation on regular railway lines. This introduces some questions that are more complex than in today's systems: the performance, length and weight of the trains spreads in a wider range; there are other and more complex operations; components such as level crossings in different equipment variants are added; requirements are higher and the technological equipment point is more heterogeneous. Many evolutionary or innovative approaches for railway automation rely on precise and reliable localization. Especially for higher levels of automation it is essential. Starting from existing technologies such as the European Train Control System (ETCS), moving on to advanced driver assistance systems for local automatic operation up to full automatic train operation (ATO), all of these solutions depend on knowledge of the position of the train on the network. Improved concepts for railway operation e.g. using moving block, on-board integrity supervision or virtual train sets will result in even higher requirements for accuracy and reliability of the localization. The contribution shows an approach based on Global Navigation Satellite Systems (GNSS) as a priority source of information used in combination with sensor data fusion. Elements such as trackside augmentation as well as the use of digital maps will be discussed. Different approaches are considered, e.g. those currently under development by projects in the innovation program in the joint undertaking Shift2Rail.

Les applications des systèmes de positionnement par satellites (ou GNSS - Global Navigation Satellite System) ont progressivement envahi les systèmes de transport et les applications mobiles. Les applications déployées sont peu exigeantes en termes de performance : elles tolèrent une certaine imprécision et ne requièrent pas nécessairement une grande confiance dans l'information délivrée. Avec l'arrivée des véhicules autonomes ou les évolutions des systèmes de signalisation ferroviaire, de nouveaux besoins sont exprimés : une plus grande précision assortie d'un indicateur de confiance dans l'information fournie, en particulier pour des applications qui mettent en jeu la sécurité des biens et des personnes. Un récepteur GNSS utilise la mesure simultanée de 4 (au moins) temps de propagation des signaux issus de 4 satellites différents pour estimer sa position. Dans les environnements traversés par les systèmes de transports, la réception de ces signaux est fréquemment sujette à des conditions de réception difficiles liées à la présence d'obstacles proches de l'antenne de réception (blocage, réflexion, diffraction) qui engendrent indisponibilité, retards de propagation et donc, erreurs sur le calcul de la position. Pour comprendre les causes et les conséquences des erreurs introduites par le canal de propagation radio sur les performances de localisation, les travaux présentés dans ce mémoire de HDR rassemblent les travaux menés selon 3 axes principaux. Dans ces travaux, nous avons ainsi analysé les effets du canal de propagation radio sur le signal reçu par l'antenne du récepteur GNSS, caractérisé et quantifié la qualité du signal reçu en sortie du récepteur, proposé des méthodes originales permettant de modéliser et pallier les erreurs de localisation et enfin nous avons contribué au développement d'une méthodologie d'analyse de la sûreté de fonctionnement du système de localisation dans le domaine ferroviaire. L'erreur que nous cherchons à réduire en particulier est l'erreur engendrée par les phénomènes de propagation locaux et en particulier par l'utilisation des signaux reçus après réflexions et en l'absence de signal direct, encore appelés NLOS (Non-Line-Of-Sight). Parmi les résultats, nous avons mis en oeuvre des techniques de traitement d'images pour une détection déterministe associée à des techniques d'exclusion et de pondération des signaux reçus. Avec des techniques de traitement du signal, nous avons proposé des méthodes d'estimation dynamique des retards de propagation qui ont montré leur efficacité dans la réduction des imprécisions sur les calculs de la position en milieux urbains. Enfin, nous abordons le concept d'intégrité de la position. Les processus de surveillance de l'intégrité sont aujourd'hui issus de l'aéronautique et s'adaptent mal aux conditions de réception en milieu urbain. Notre connaissance des conditions de propagation des signaux nous a conduits à étudier et à proposer de nouveaux processus pour borner les erreurs de position introduites par l'environnement urbain. Enfin, nous présentons les axes de recherche mis en oeuvre afin de contribuer à l'introduction des solutions GNSS pour des applications de signalisation ferroviaire : nos travaux portent sur l'adaptation des méthodologies classiques ferroviaires au système GNSS et à ses sources de dégradation.

The objective of STARS task 5.1 is to review the existing navigation augmentation systems and services in terms of performances achieved and application environments, and to analyse the experimentations and projects already performed in railway applications related to the use of these systems and services.This report aims to draw the state of the art of existing monitoring system (as used in aeronautics) and past experiences of railways when using such concepts. The focus only concerns GNSS-based positioning systems and do not pretend to present the global systems developed to insure the complete safety level of railway signalling.

Institute of navigation - International Technical Meetings - ION ITM 2017, Monterey, Etats-Unis, 30-/01/2017 - 02/02/2017; Integrity is one of the most important parameters characterizing the Global Navigation Satellite Systems (GNSS) performance for safety-related applications. It is defined as a measure of trust to be placed in the correctness of the information supplied by the total system. This concept is more and more important, especially for applications in urban environment with standalone GNSS system, where GNSS performance is strongly degraded by the signal propagation conditions. Non line of Sight (NLOS) signals, caused by the surrounding obstacles, are of particular interest, as the error they induced remains a large cause of inaccuracy. In order to get rid of these constraints and to guarantee a better performance of positioning accuracy as well as integrity, several approaches can be used, such as positioning weighting models, 3D city models, Fault Detection and Exclusion (FDE) techniques etc. Since the concepts of integrity and accuracy are strongly related to each other, a better accuracy can help to improve the integrity performance. Thus, to reduce and to bound position errors are our two main objectives. In the work presented here, we will introduce 2 classes of methods which contribute to the NLOS signal mitigation as well as integrity performance. The first class concerns the use of different weighting models in order to reduce the influence of the NLOS on the overall measurements. The second class consists of Fault Detection and Exclusion (FDE) algorithms which allow users to identify and remove the outliers.