Scientific Production

SEARCH

Search

Journal Paper

Two-Color Scheme for a Multi-Beam Satellite Return Link : Impact of Interference Coordination

Authors: Couble Yoann, Rosenberg Catherine, Chaput Emmanuel, Dupé Jean-Baptiste, Baudoin Cédric and Beylot André-Luc

IEEE Journal on Selected Areas in Communications, vol. 36, pp. 993-1003, May 2018.

The return link of broadband satellite systems has recently received more attention due to the spread of multi-beam antennas which enable spatial frequency reuse, and thus increase drastically the number of users that can potentially be served by one satellite. While interference isolation has so far been the way to go, with regular four-color frequency reuse scheme, there is a growing interest in densifying the frequency usage as is being done in cellular networks. In this paper, we address the return link radio resource allocation challenges, from spectral resource allocation to user scheduling, including modulation and coding scheme (MODCOD) selection. Our contributions highlight the potential gains of a two-color scheme and shed light on several levers to reap its benefits through interference management. We first consider the possibility to use a two-color scheme, while keeping the MODCOD selection and the scheduling local to each beam and we show that even though it yields a potential performance gain (+16%) with respect to the state of the art (SoA) (based on four colors), it is not viable due to a very high-block loss rate. Therefore, we propose a simple-yet fast and efficient-coordinated MODCOD selection process that alleviates the need of estimating interference and reduces drastically decoding failures. This coordination step offers significant gains (+58%) over the SoA, while leaving the per beam scheduler unchanged. Finally, we formulate a joint user scheduling and MODCOD selection problem across all beams and propose an offline heuristic to solve it efficiently. We obtain a 83% gain with respect to the SoA, but with higher computational complexity. Still, it confirms the great potential of coordinated scheduling.

Networking / Space communication systems

READ MORE

PhD Thesis

Fiabilisation des Transmissions Optiques Satellite-Sol / Reliability of Satellite-to-Ground Optical Communication

Author: Canuet Lucien

Defended on April 16, 2018.

DOWNLOAD DOCUMENT

Optical wavelengths are an alternative to radio-frequency links for future satellite-to-ground transmissions. They are envisioned in the framework of payload/telemetry data transfer (optical downlinks from LEO satellites) or communication (bi-directional optical links with GEO satellites). However, as it propagates through the atmosphere, the optical wave can be deeply affected by atmospheric turbulence which induces randomspatial and temporal variations of its amplitude and phase. Variations in amplitude translate into fluctuations of the collected power (scintillation). The phase distortions affect the spatial distribution of the power at the focal plane of the telescope causing deleterious losses when the incident flux needs to be coupled to an optoelectronic detector or to a single-mode optical fiber. Such losses result in dynamical attenuations of the received signal-called fading- and hence potentially to the loss of information. The most recent feasibility studies highlight the use of two types of fading mitigation techniques : adaptive optics systems and digital techniques (coding and interleaving). To limit the complexity and cost of such systems, the optimization of these mitigation techniques should be conducted jointly. The main objective of this thesis is therefore the investigation of the complementarity of physical (adaptive optics) and digital data reliability mechanisms (interleaving, correcting and erasure codes in a cross-layer approach).

READ MORE

Conference Paper

Restoration of Ultrasonic Images using Non-linear System Identification and Deconvolution

Authors: Hourani Mohamad, Basarab Adrian, Kouamé Denis, Girault Jean-Marc and Tourneret Jean-Yves

In Proc. IEEE International Symposium on Biomedical Imaging (ISBI), Washington DC, USA, April 4-7, 2018.

Signal and image processing / Earth observation

READ MORE

Patent

PROCÉDÉ D'ALLOCATION DE FRÉQUENCES DANS UN SYSTÈME DE RADIOCOMMUNICATION SATELLITAIRE MULTIFAISCEAUX, ET SYSTÈME ASSOCIÉ

Authors: Baudoin Cédric, Couble Yoann, Deleu Thibault, Dupé Jean-Baptiste and Chaput Emmanuel

n° 071015 FR RQDLV 26-02-18 BRU-AMA, February 2018.

Networking / Space communication systems

READ MORE

Talk

Patch-Based Regularization in Multiband Imaging Inverse Problems

Author: Bioucas Dias José Manuel

Seminar of TeSA, Toulouse, February 16, 2018.

Qualité des Observations pour les systèmes Sensor Webs

Author: Auger Antoine

Seminar of TeSA, Toulouse, February 16, 2018.

DOWNLOAD DOCUMENT

Les systèmes dits Sensor Webs sont des middlewares informatiques assurant la communication entre les capteurs et les applications. En tant que véritables médiateurs, la popularité de ces systèmes n’a cessé de grandir depuis l’apparition des tout premiers capteurs. Plus récemment, l’émergence de nouveaux paradigmes tels que l’Internet des Objets (IoT) a complètement révolutionné les systèmes basés sur les capteurs en général. Parmi eux, les Sensor Webs ne dérogent pas à cette règle et doivent maintenant répondre à de nouveaux défis, notamment en termes d’intégration, de Qualité des Observations (QoO) et d’adaptation système. Dans le cadre de ma thèse, j'ai proposé une nouvelle génération de Sensor Webs capables d’adapter la QoO distribuée de manière autonomique et spécifique à chaque application (QASWS). Premièrement, j'introduirai un framework générique destiné aux chercheurs et développeurs souhaitant concevoir leur propre solution QASWS. Dans un deuxième temps, je montrerai comment j'ai utilisé ce framework afin de développer une plateforme d’intégration pour l’évaluation de la QoO à la demande (iQAS). Après avoir évalué ses performances, je présenterai trois cas d’utilisation pour la plateforme iQAS. Finalement, je conclurai ma présentation en imaginant l’apport de certains paradigmes transverses vis-à-vis de la QoO dans un futur proche.

Networking / Other

READ MORE

Communication IoT low-cost par satellite

Author: Cluzel Sylvain

Seminar of TeSA, Toulouse, February 16, 2018.

DOWNLOAD DOCUMENT

Les réseaux de capteurs type LPWAN (grande autonomie, grande couverture, faible débit) sont en plein essor. Ces réseaux, qui ont pour but de connecter des milliers de capteurs sans fils de la manière la plus efficace possible, seraient un maillon indispensable à l’internet des objets tel qu’il est imaginé dans les années à venir. Dans le but d’augmenter la couverture de ces services, un lien satellite est envisagé. Cette thèse étudie les contraintes liées à l’utilisation d’un lien satellite unidirectionnel dans un système terrestre étendu, sans modifications du matériel, supposé bas-coût. Après une rapide présentation du milieu de l’IoT et des solutions LPWAN terrestres, nous présenterons la solution et le système choisis, compatible LTE NB-IoT. L’utilisation d’un lien satellite limite le système en termes de bilan de liaison et d’interférences. On cherchera alors à quantifier ces interférences et à obtenir les performances d’un tel réseau.

READ MORE

Conference Paper

New Solutions on the Design of a Galileo Acquisition-Aiding Signal to Improve the TTFF and the Sensitivity

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

In Proc. Institute of Navigation International Technical Meeting & Trade Show (ION ITM), Reston, USA, January 29-February 1, 2018.

DOWNLOAD DOCUMENT

The design of a new GNSS signal is always a trade-off between improving performance and increasing complexity, or even between improving different performance criteria. Position accuracy, receiver sensitivity (acquisition, tracking or data demodulation thresholds) or the Time-To-First-Fix (TTFF) are examples of those GNSS receivers performance criteria. Within the framework of Galileo 2nd Generation (G2G), adding a new signal component dedicated to aid the acquisition process on E1 can help to improve performance of GNSS receivers with respect to these criteria as it was shown in [1]. In order to create this new component, various aspects such as the spreading modulation, the data navigation content, the channel coding or the Pseudo-Random Noise (PRN) codes must be studied. To this end, this paper firstly proposes the study of new spreading modulations, and secondly, we investigate on PRN codes that can be well suited to the proposed Acquisition-Aiding signal.

Digital communications / Localization and navigation and Space communication systems

READ MORE

Journal Paper

Performances Analysis of GNSS NLOS Bias Correction in Urban Environment Using a 3D City Model and GNSS Simulator

Authors: Kbayer Nabil and Sahmoudi Mohamed

IEEE Transactions on Aerospace and Electronic Systems, PP(99):1-1, 2016.

DOWNLOAD DOCUMENT

The well-known conventional Least Squares (LS) and Extended Kalman Filter (EKF) are one of the most widely used algorithms in science and particularly in localization with GNSS measurements. However, these estimators are not optimal when the GNSS measurements become contaminated by non-Gaussian errors including multipath (MP) and non-line-of-sight (NLOS) biases. On the other hand, this kind of ranging measurements errors occurs generally in urban areas where GNSS-based potitionning applications require more accuracy and reliability. In this paper, we use additional information of the environment consisting of bias prediction from a 3D model and a GNSS simulator to exploit constructively NLOS measurements. We use this 3D GNSS simulator to predict lower and upper bounds of these biases. Then, we integrate this information in the position estimation problem by considering these biases as additive error and exploiting the bounds to end-up with a constrained state estimation problem that we resolve with existing Constrained Least Squares (CLS) and Constrained EKF (CEFK) algorithms. Experimental results using real GPS signals in Down-Town Toulouse show that the proposed estimator is capable of improving the positioning acuracy compared to conventional algorithms. Theoretical conditions have been established to determine the acceptable bias prediction error allowing better positioning performance than conventional estimators. Tests are conducted then to validate these conditions and investigate the influence of the bias prediction error on the localization performance by proposing new acuracy metrics.

Signal and image processing / Localization and navigation

READ MORE

A Hierarchical Bayesian Model Accounting for Endmember Variability and Abrupt Spectral Changes to Unmix Multitemporal Hyperspectral Images

Authors: Thouvenin Pierre-Antoine, Dobigeon Nicolas and Tourneret Jean-Yves

IEEE Transactions on Computational Imaging, vol. 4, issue 1, pp. 32-45, January 2018.

DOWNLOAD DOCUMENT

Hyperspectral unmixing is a blind source separation problem which consists in estimating the reference spectral signatures contained in a hyperspectral image, as well as their relative contribution to each pixel according to a given mixture model. In practice, the process is further complexified by the inherent spectral variability of the observed scene and the possible presence of outliers. More specifically, multi-temporal hyperspectral images, i.e., sequences of hyperspectral images acquired over the same area at different time instants, are likely to simultaneously exhibit moderate endmember variability and abrupt spectral changes either due to outliers or to significant time intervals between consecutive acquisitions. Unless properly accounted for, these two perturbations can significantly affect the unmixing process. In this context, we propose a new unmixing model for multitemporal hyperspectral images accounting for smoothtemporalvariations,construedasspectralvariability,and abrupt spectral changes interpreted as outliers. The proposed hierarchical Bayesian model is inferred using a Markov chain Monte-Carlo (MCMC) method allowing the posterior of interest to be sampled and Bayesian estimators to be approximated. A comparison with unmixing techniques from the literature on synthetic and real data allows the interest of the proposed approach to be appreciated.

Signal and image processing / Earth observation

READ MORE

Activity Report

READ MORE

TeSA in Miami

Philippe Paimblanc, TeSA Researcher, Julien Lesouple and Lorenzo Ortega, TeSA PhD students, presented papers at ION GNSS+ 2018.

TeSA in Berlin

Bastien Tauran and Selma Zamoum, TeSA PhD students, presented papers at ASMS/SPSC 2018.

Yoann Couble becomes a Doctor

Congratulations!