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Conference Paper

Incorporating User Feedback Into One-Class Support Vector Machines for Anomaly Detection

Authors: Lesouple Julien and Tourneret Jean-Yves

In Proc. 28th European Signal Processing Conference (EUSIPCO), Amsterdam, Netherlands, January 18-22, 2021.

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Machine learning and data-driven algorithms have gained a growth of interest during the past decades due to the computation capability of the computers which has increased and the quantity of data available in various domains. One possible application of machine learning is to perform unsupervised anomaly detection. Indeed, among all available data, the anomalies are supposed to be very sparse and the expert might not have the time to label all the data as nominal or not. Many solutions exist to this unsupervised problem, but are known to provide many false alarms, because some scarce nominal modes might not be included in the training dataset and thus will be detected as anomalies. To tackle this issue, we propose to present an existing iterative algorithm, which presents potential anomaly to the expert at each iteration, and compute a new boundary according to this feedback using One Class Support Vector Machine.

Signal and image processing / Space communication systems

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Wing 3D Reconstruction by Constraining the Bundle Adjustment with Mechanical Limitations

Authors: Demoulin Quentin, Lefebvre-Albaret François, Basarab Adrian, Kouamé Denis and Tourneret Jean-Yves

In Proc. 28th European Signal Processing Conference (EUSIPCO), Amsterdam, Netherlands, January 18-22, 2021.

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The estimation of wing deformation is part of the certification of an aircraft. Wing deformation can be obtained from 3D reconstructions based on conventional multiview photogrammetry. However, 3D reconstructions are generally degraded by the variable flight environments that degrade the quality of 2D images. This paper addresses this issue by taking benefit from a priori knowledge of the wing mechanical behaviour. Specifically, mechanical limits are considered to regularize the bundle adjustment within the photogrammetry reconstruction. The performance of the proposed approach is evaluated on a real case, using data acquired on an aircraft A350-900.

Signal and image processing / Aeronautical communication systems

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Constrained Bundle Adjustment Applied to Wing 3D Reconstruction with Mechanical Limitations

Authors: Demoulin Quentin, Lefebvre-Albaret François, Basarab Adrian, Kouamé Denis and Tourneret Jean-Yves

In Proc. IEEE International Conference on Image Processing (ICIP), Abu Dhabi, United Arab Emirates, October 25-28, 2020.

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Aircraft certification procedures require the estimation of wing deformation, which is a very challenging problem in photogrammetry applications. Indeed, in real flight conditions with varying environment, 3D reconstruction is strongly degraded. To cope with this issue, we propose to introduce prior knowledge about the wing mechanical limits in the photogrammetry reconstruction method. These mechanical limits are expressed as appropriate regularizations that are included into the classical bundle adjustment step. The proposed approach is evaluated using data acquired on a real aircraft yielding promising results.

Signal and image processing / Aeronautical communication systems

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QUIC: Opportunities and threats in SATCOM

Authors: Kuhn Nicolas, Michel François, Thomas Ludovic, Dubois Emmanuel and Lochin Emmanuel

In Proc. Advanced Satellite Multimedia Systems (ASMS), Graz, Austria, October 20-21, 2020.

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This article proposes a discussion on the strengths, weaknesses, opportunities and threats related to the deployment of QUIC end-to-end from a satellite-operator point-of-view. The deployment of QUIC is an opportunity for improving the quality of experience when exploiting satellite broadband accesses. Indeed, the fast establishment of secured connections reduces the short files transmission time. Moreover, removing transport layer performance enhancing proxies reduces the cost of network infrastructures and improves the integration of satellite systems. However, the congestion and flow controls at end points are not always suitable for satellite communications due to the intrinsic high bandwidth-delay product. Further acceptance of QUIC in satellite systems would be guaranteed if its performance in specific use-cases is increased. We propose a running code for an IETF document, and based on an emulated platform and on open-source software, this paper proposes values of performance metrics just as one piece of the puzzle. The final performance objective requires consensus among the different actors. The objective should be challenging enough for satellite operators to allow QUIC traffic but reasonable enough to keep QUIC deployable on the Internet.

Networking / Space communication systems

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Improving the estimation of the sea level anomaly slppe

Authors: Mailhes Corinne, Besson Olivier, Guillot Amandine and Le Gac Sophie

in Proc. IEEE Int. Geosci. Remote Sens. Symp. (IGARSS), Hawaï, USA, 26 September - 2 October 2020.

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Satellite altimeters provide sea level measurements along satellite track. A mean profile based on the measurements averaged over a time period is then subtracted to estimate the sea level anomaly (SLA). In the spectral domain, SLA is characterized by a power spectral density of the form one over a power of the frequency where the power (the slope) is a parameter of great interest for ocean monitoring. However, this information lies in a narrow frequency band, located at very low frequencies, which calls for some specific spectral analysis methods. This paper studies a new parametric method based on an autoregressive model combined with a warping of the frequency scale (denoted as ARWARP). A statistical validation is proposed on simulated SLA signals, showing the performance of slope estimation using this ARWARP spectral estimator, compared to classical Fourier-based methods. Application to Sentinel-3 real data highlights the main advantage of the ARWARP model, making possible SLA slope estimation on a short signal segment, i.e., with a high spatial resolution.

Signal and image processing / Earth observation

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Journal Paper

New multiplexing method to add a new signal in the Galileo E1 band

Authors: Ortega Espluga Lorenzo, Poulliat Charly, Boucheret Marie-Laure, Aubault-Roudier Marion and Al Bitar Hanaa

IET Radar, Sonar & Navigation, E-First, Print pp.1751-8784, Online pp. 1751-8792, September, 2020.

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This work addresses the problem of integrating a new signal in the Galileo E1 band. Thus, the arising question is how the existing multiplexing methods can be efficiently used or modified to integrate a new binary signal in the Galileo E1 band with the existing Galileo E1 signals. To this end, in this study, the authors first select three efficient multiplexing methods from the state of the art (i.e. interplexing, POCET and CEMIC methods) to multiplex a new Galileo signal along with the Galileo E1 legacy signals in a constant envelope modulation. Moreover, they evaluate their performance and main advantages and drawbacks. Secondly, in order to improve both performance and flexibility/adaptability of the multiplexing method, a modified CEMIC method, called ACEMIC, is proposed. This method allows to design modulations which maximise the power efficiency with respect to a given peak-to-average-power-ratio constraint. Finally, they compare the previous multiplexing methods in terms of power signal distribution, constant envelope fluctuation and power efficiency.

Signal and image processing / Localization and navigation and Space communication systems

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Conference Paper

Processed 5G Signals Mathematical Models for Positioning considering a Non-Constant Propagation Channel

Authors: Tobie Anne-Marie, Garcia Pena Axel, Thevenon Paul and Aubault-Roudier Marion

In Proc. Vehicular Technology Conference (VTC-Fall), Honolulu, Hawaii, USA, September 22-25, 2019.

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The objective of this paper is to determine the ranging performance of the upcoming fifth generation (5G) signal. In order to do so, it is required to define 5G correlator outputs mathematical models. 5G systems will use OFDM (Orthogonal Frequency Division Multiplexing) signals; in the literature, mathematical models of OFDM signals are developed at the different receiver signal processing stages. These models assumed that the propagation channel is constant over an OFDM symbol; nevertheless, an in-depth study of QuaDRiGa, a 5G compliant propagation channel simulator, invalidates this hypothesis. Therefore, in this paper, mathematical models are developed that take into account the channel evolution. The focus is given on correlator outputs and results are applied to the computation of 5G based pseudo range accuracy.

Digital communications / Localization and navigation

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An Assessment Methodology of Smartphones Positioning Performance for Collaborative Scenarios in Urban Environment

Authors: Verheyde Thomas, Blais Antoine, Macabiau Christophe and Marmet François-Xavier

In Proc. ION GNSS+, St Louis, Missouri, USA, September 21-25, 2020.

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The release of Android Global Navigation Satellite Systems (GNSS) raw measurements in late 2016 unlocked the access of smartphones' embedded positioning chipset capabilities for developers and the scientific community. This groundbreaking announcement was followed by technical innovations, made by smartphone brands and chipset manufacturers, in order to obtain the world's most precise smartphone on the market. In recent years, several studies investigated the development of advanced positioning techniques (e.g. Precise Point Positioning (PPP), Real-Time Kinematic (RTK)) using Android raw data measurements. However, most studies drawn their conclusions based on one smartphone brand and model in optimal open-sky conditions despite the fact that most smartphone-based positioning activities are achieved in urban and sub-urban areas. In order to overcome urban smartphone-based positioning issues, we ambition to develop a collaborative user’s network taking advantage of the tremendous numbers of connected Android devices in today's busy city centers. A throughout study has been conducted in the city center of Toulouse in France for characterizing smartphone positioning performance in both nominal and urban conditions. Various limiting factors were exposed during our data collection campaign. Nevertheless, the investigation conducted on Android GNSS raw measurement uncovered smartphone positioning potential for navigation applications in constraint environment. A methodology assessment has been implemented in order to identify, characterize and compare smartphones’ positioning performances. A classification of key parameters has been determined focusing on the implementation of collaborative algorithms, revealing the attributes and components for smartphone-based collaborative methods. Thereafter, a comprehensive state of the art review on existing cooperative positioning techniques, has been achieved. An evaluation of the feasibility and the applicability of those methods into the smartphone domain has been made. We present a method based on simple assumptions, without third-party equipment and data, only relying on smartphones’ own data combination. Our cooperative network can be described as a low-cost embedded structure aiming at providing positioning assistance to its users.

Digital communications / Localization and navigation

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On the Time-Delay Estimation Accuracy Limit of GNSS Meta-Signals

Authors: Ortega Espluga Lorenzo, Vilà-Valls Jordi, Chaumette Eric and Vincent François

In Proc. Intelligent Transportation Systems Conference (IEEE/ITSC), Rhodes, Greece, September 20-23, 2020.

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In standard two-step Global Navigation Satellite Systems (GNSS) receiver architectures the precision on the position, velocity and time estimates is driven by the precision on the intermediate parameters, i.e., delays and Dopplers. The estimation of the time-delay is in turn driven by the baseband signal resolution, that is, by the type of broadcasted signals. Among the different GNSS signals available the socalled AltBOC modulated signal, appearing in the Galileo E5 band and the new GNSS meta-signal concept, is the one which may provide the better time-delay precision. In order to meet the constraints of safety-critical applications such as Intelligent Transportation Systems or automated aircraft landing, it is fundamental to known the ultimate code-based precision achievable by standalone GNSS receivers. The main goal of this contribution is to assess the time-delay precision of AltBOC type signals. The analysis is performed by resorting to a new compact closed-form Cramér-Rao bound expression for time-delay estimation which only depends on the signal samples. In addition, the corresponding time-delay maximum likelihood estimate is also provided to assess the minimum signal-to-noise ratio that allows to be in optimal receiver operation.

Signal and image processing / Localization and navigation and Space communication systems

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On the Time-Delay Estimation Accuracy Limit of GNSS Meta-Signals

Authors: Ortega Espluga Lorenzo, Vilà-Valls Jordi, Chaumette Eric and Vincent François

In Proc. Intelligent Transportation Systems Conference (IEEE/ITSC), Rhodes, Greece, September 20-23, 2020.

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In standard two-step Global Navigation Satellite Systems (GNSS) receiver architectures the precision on the position, velocity and time estimates is driven by the precision on the intermediate parameters, i.e., delays and Dopplers. The estimation of the time-delay is in turn driven by the baseband signal resolution, that is, by the type of broadcasted signals. Among the different GNSS signals available the socalled AltBOC modulated signal, appearing in the Galileo E5 band and the new GNSS meta-signal concept, is the one which may provide the better time-delay precision. In order to meet the constraints of safety-critical applications such as Intelligent Transportation Systems or automated aircraft landing, it is fundamental to known the ultimate code-based precision achievable by standalone GNSS receivers. The main goal of this contribution is to assess the time-delay precision of AltBOC type signals. The analysis is performed by resorting to a new compact closed-form Cramér-Rao bound expression for time-delay estimation which only depends on the signal samples. In addition, the corresponding time-delay maximum likelihood estimate is also provided to assess the minimum signal-to-noise ratio that allows to be in optimal receiver operation.

Signal and image processing / Localization and navigation and Space communication systems

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Activity Report

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WiSATS 2020

Conference talk of Amal Boubaker, TeSA PhD, at WiSATS 2020

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ETTC 2020

Conference talk of Quentin Demoulin, TeSA PhD, at ETTC 2020

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ICL-GNSS 2020

Conference talks of Thomas Verheyde, TeSA PhD and Lorenzo Ortega, TeSA postdoc, at ICL-GNSS 2020

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