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L'article présente le projet ERSAT GGC et les techniques de détection des effets locaux sur les GNSS développées pour l'introduction du GNSS dans le système ERTMS/ETCS

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.

This document is the deliverable D4.2-Technical Specification of the Survey Toolset where the outcome of the work performed in WP4.2 of the ERSAT GGC project is described. This document follows up the work performed in WP4.1 and reported in the deliverable D4.1, extending the ongoing general definition of the track area classification process. The goal of WP4.2 is the specification and development of the toolset for the survey and classification of track areas, giving the system overview and providing the different interacting blocks as the measurement hardware system, the processing software toolbox and the final classification data. Regarding this D4.2, the functional and technical specifications of the toolset are here provided with the description of the interfaces between the different detection techniques and decision logic blocks. Outcome of D4.3 will be the prototype implementation and installation. The document also includes the specification of the measurement system and hardware to be used in the survey process so that the necessary data for the classification techniques can be collected in the railway scenario. Finally, the specification of the output data - the track area classification results - is also analysed and provided. The specification of the survey measurement system and software toolset addressed in the current document will support the next project activities related to the development of the software tools for the classification of track areas in WP4.2 and the execution of measurement campaigns in WP4.3.

This document is the deliverable D4.3-Prototype Implementation of the Survey Toolset, which provides a high level description of the Toolset Prototype. This document is released in a pre-final version, where the toolset implementation has been done using demo data coming from RFI-ASTS private campaign in Italy. The dataset, related to the Pinerolo-Torino line, was used to test and debug the toolset, and the results provided in this document refer to that line and campaign. The Consortium thanks RFI, ASTS and TRI for the investment done to this aim and the availability of needed dataset in order to respect the scheduling of the project. The toolset will be definitively designed after the test campaigns on field, which will confirm the assumptions and in particular the decision logic approach. In fact, once the test campaigns foreseen in the ERSAT GGC will be performed - as planned in the WP4.3 task - the final implementation of the toolset prototype will be released based on those data. A conclusive issue of this deliverable will be then provided with the results of the test campaigns.

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.

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.

International audience; This paper presents the sizing and choice of the technological solutions used for the thermal management of the critical hot parts, the main structure and the equipment of the Hexafly-Int hypersonic glider. Air conditioning into the fairing is used during pre-flight operations so as to maintain the temperature of the vehicle with its equipment below 20°C. During the flight, the thermal integrity of the nose is based on a heat sink approach by using massive blocks of metallic materials coated by zirconium whereas the wing leading edges and the flaps are made in C/C-SiC material. Among different assessed solutions, the temperature of the main titanium structure is maintained below 700°C thanks to an extra high emissivity painting applied on its external face. Equipment is protected from radiative heat transfer of the main structure thanks to a light flexible microporous insulator named Aeroguard® which exhibits extra high insulation performance at low pressure into the stratosphere. This internal thermal protection system is kept in place on the internal faces of the main structure thanks to thin flexible wires which allow fast depressurization of the insulator and mechanical strength to vibrations during the ascent phase of the flight. All equipment is also protected from conductive heat transfer coming from the hot main structure by using low thermal conductivity fixations based on Vespel® material. A special thermal management is dedicated to telemetry electronic boxes so as to absorb their dissipated power into a heat sink based on phase changing material.

ITST 2018, 16th International Conference on Intelligent Transport Systems Telecommunications, Lisbonne, PORTUGAL, 15-/10/2018 - 17/10/2018; The introduction of the GNSS positioning technology into the evolution of ERTMS/ETCS is based on the concept of virtual balise to minimize the impact onto existing ERTMS solutions. The detection of virtual balises is foreseen by using GNSS in combination with odometry information. However, the presence of local GNSS threats (e.g, multipath, NLOS or interference) may lead to unbounded errors in the pseudorange measurement that cannot be corrected by local or wide-area augmentation systems, and will lead ultimately to an error in the virtual balise position that cannot be bounded with the required integrity. In order to a priori prevent the risk of this hazardous situation, virtual balises must be logically located in areas where there are not local threats that may lead a Virtual Balise Transmission System on board the train to dynamically estimate unbounded virtual balise position errors. This paper summarizes the initial work performed in the H2020 GSA Project ERSAT-GGC with respect to the different techniques that can be used to detect local GNSS threats and that can support a later classification of railway areas as suitable or not suitable for placing virtual balises.

The deliverable D4.1 Procedure Specification Document of the ERSAT-GGC project is related to the work performed in Task 4.1. The aim of WP4 is to set up a standard measured system that is able to provide a forecast method for the GNSS service performance to be expected at a given track point, in order to enable evaluation whether the specific scenario is favourable to place virtual balises or on the contrary should be discarded beforehand. The results of this assessment can be included in a database map where geo-referenced GNSS quality data is stored. Users may access the information via specified interfaces using standardized communication channels. In order to set up the system, at first a standardized process has to be defined and specified that will determine what has to be measured under which conditions and what has to be simulated for GNSS characterizing along the line. This is the scope of Task 4.1. In order to set the context of the work, a description of the need and importance of a standard process to classify the track areas for virtual balise placement is given in the introduction. Later, a first version of the high level requirements to the classification process is provided. Based on these requirements a preliminary study of the different techniques, measurements and parameters that are relevant to define a safe track area classification standard process has been performed. The document then focus on a detail description on the GNSS detection techniques that are relevant for the standard process and the track area classification criteria. Further works related to the detection and classification criteria are required, and they will be included in the next deliverable D4.2, which specifies the dedicated requirements for the toolset.The standard process will undergo reviews until the execution and test: all these improvements and the related links to the toolset development will be covered by the next deliverables of WP4.

International audience; This paper proposes one possible concept for a dual frequency dual constellation GBAS architecture. It is based on a single frequency L5/E5a mode as primary processing scheme for best standard performance, a switch to an ionosphere free combination in case of ionospheric disturbances and supporting also classical GBAS approach service types (GAST) C and D for single frequency GPS-based CAT I and CAT II/III modes. The concept is supported by a proposal of how to transmit the required corrections in the existing capacity limited VDB broadcast and is backwards compatible to legacy GBAS. A discussion about the benefits and remaining issues of the proposed architecture concludes the paper.

International audience; The Ground Based Augmentation System (GBAS) is being studied as a potential means to provide Category II/III precision approach operations. The current technology, the Instrumental Landing System (ILS) is expensive to maintain and suffers from multipath effects which inhibit capacity in all - weather conditions. The GBAS Approach Service Types (GASTs) have been define d to apply to the various levels of vertically guided approach for which up to GAST C relating to Category I precision approach have been standardized. GAST D is under development to support Category II/III precision approaches using the L1 C/A signal of t he GPS constellation. A GAST F concept is being developed within the SESAR framework on the basis of a multi - constellation (GPS and GALILEO) multi - frequency environment (L1/L5 and E1/E5a). In order to assess which processing models are to be selected for t he GAST F solution, the error models for the new signals must be developed taking into account the impact of the antenna and receiver. This paper presents the analysis of the noise and multipath characterisation using real measurements taken at an experimental ground station

International audience; Crowdsourcing platforms for disaster management have drawn a lot of attention in recent years due to their efficiency in disaster relief tasks, especially for disaster data collection and analysis. Although the on-site rescue staff can largely benefit from these crowdsourcing data, due to the rapidly evolving situation at the disaster site, they usually encounter various difficulties and have requests, which need to be resolved in a short time. In this paper, aiming at efficiently harnessing crowdsourcing power to provide those on-site rescue staff with real-time remote assistance, we design and develop a crowdsourcing disaster support platform by considering three unique features, viz., selecting and notifying relevant off-site users for individual request according to their expertise; providing collaborative working functionalities to off-site users; improving answer credibility via "crowd voting." To evaluate the platform, we conducted a series of experiments with three-round user trials and also a System Usability Scale survey after each trial. The results show that the platform can effectively support on-site rescue staff by leveraging crowdsourcing power and achieve good usability

International audience

International audience; This paper presents an overview on the performance of hybrid data fusion and tracking algorithms evaluated in the WHERE consortium. The focus is on small scale indoor scenarios with ultra wideband (UWB) complementing cellular communication systems, mid scale indoor scenarios with Wi-Fi aiding cellular communication systems, and large scale outdoor scenarios with global navigation satellite systems (GNSSs) aided by cellular communication systems. For the small scale indoor scenario with UWB, the accuracy can vary in time as a connectivity-dependent random process distributed over 3 orders of magnitude, from 100m in the worst situation down to 0.1m in the most favourable one. In the mid scale scenario, time difference of arrival (TDOA) measurements from a cellular network can give wide-area coverage with limited accuracy, whereas the received signal strength measurements of Wi-Fi hotspots give more accurate results if coverage is available. Finally, for large scale outdoor scenarios, cellular TDOA measurements can support GNSS especially in critical scenarios, where only a few satellites are visible. This is even the case when the overall accuracy of stand-alone cellular positioning is lower than that for GNSS positioning under optimum conditions.

This paper considers a downlink multiple-input multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) system with pilot aided channel estimation (PACE) and iterative channel estimation (ICE) in the receiver. Exploiting orthogonal space-time block coding (STBC), we investigate ICE schemes as a simple extension of PACE using estimated data chips as additional pilots. Due to the superpo-sition of different users? spread data signals, zero-valued chips can occur after spreading, which can cause noise enhancement when using data estimates as reference signals in ICE. Hence, we propose MIMO channel estimation methods to overcome the above problem. Simulations with a realistic outdoor MIMO channel model, over a wide range of data rates and speeds, show that ICE can outperform PACE at the cost of increased complexity.

This paper investigates a downlink multiple-input multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) system with pilot aided channel estimation (PACE) and iterative channel estimation (ICE) in the receiver. Due to the superposition of different users' spread data signals, zero-valued chips can occur after spreading, which can cause noise enhancement when using data estimates as reference signals in ICE. Hence, we propose a MIMO channel estimation method to overcome the above problem and avoid noise enhancement in ICE. Simulations results for PACE and ICE were computed for a realistic outdoor MIMO channel model. The results show that frame error rates of ICE are smaller than the ones of PACE.

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WCRR 2022, World Congress on Railway Research, Birmingham, ROYAUME-UNI, 06-/06/2022 - 10/06/2022; Novel signalling systems are expected to use Digital Maps to implement Automatic Train Operation (ATO) functions or to augment technologies such as European Global Navigation Satellite Systems (EGNSS), inertial sensors or optical sensors for localization purposes. However, the construction of a Digital Map requires with current technologies expensive railway surveying campaigns. Additionally, the cost for their maintenance and update is a major challenge that prevents its adoption. With regard to the evolution of Control-Command and Signalling (CCS) systems, a new verification infrastructure is also needed to characterize new on-board solutions in terms of train position, speed and acceleration errors, as well as to assess their expected performance. Our research, on one side, aims to develop a methodology and related toolset for executing railway surveying, building and maintaining Digital Maps based on the post-processing of data recorded by trains in commercial service, equipped with Commercial Off The Shelf (COTS) sensors like GNSS receivers, cameras, Inertial Measurement Units (IMUs), and LIDARs. On the other side, a similar approach and development can be used to provide « high precision and high accuracy ground truth reference data » as true values for carrying out error and performance analysis. This Ground Truth methodology does not require installation of trackside equipment or modifications to existing trackside signalling systems and a-priori knowledge of track databases. This paper summarizes the main user needs of (1) the use of Digital Maps for signalling subsystems purposes, (2) the availability of innovative Ground Truth sources for performance assessments. These user needs are essential for the future design of such methodologies and toolsets.