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PhD Thesis

Méthodes d'accès aléatoire pour les communications par satellite

Author: Zamoum Selma

Defended on November 28, 2019.

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The effective coverage of satellites and the technology behind have motivated many actors to develop efficient communications for Internet access, television and telephony. For a long time, reservation resources of Demand Assignment Multiple Access (DAMA) techniques have been largely deployed in the return link of satellite communications, occupying most of the frequency bandwidth. However, these resources cannot follow the technological growth with big users communities in applications like the Internet of Things and Machine to Machine communications. Especially because the Round Trip Time is significant in addition to a potential underuse of the resources. Thus, access protocols based on ALOHA took over a big part of the Random Access (RA) research area and have considerably evolved lately. CRDSA have particularly put its fingerprint in this domain, which inspired many different techniques. In this context, a complementary method, called MARSALA comes to unlock CRDSA when packets can no longer be retrieved. This actually involves a correlation complexity related to packet localization which is necessary for replicas combinations that results in a potentially higher signal power. Accordingly, the main goal of this PhD research is to seek for effective and less complex alternatives. More precisely, the core challenge focuses on the way to manage multi-user transmissions and solve interference at reception, with the smallest complexity. In addition, the loop phenomenon which occur when multiple users transmit their packets at the same positions is tackled as it creates an error floor at the packet loss ratio performance. Synchronous and asynchronous solutions are proposed in this thesis, mainly based on providing the transmitter and the receiver with a shared prior information that could help reduce the complexity, mitigate the loop phenomenon and enhance the system performance. An in-depth description and analysis of the proposed techniques are presented in this dissertation.

Digital communications / Space communication systems

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PhD Defense Slides

Random Access Techniques for Satellite Communications

Author: Zamoum Selma

Defended on November 28, 2019.

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Digital communications / Space communication systems

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Talk

Statistical Analysis of Android GNSS Raw Data Measurements in an Urban Environment for Smartphone Collaborative Positioning Methods

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

In Proc. International Navigation Conference (INC), Edinburgh, UK, Nov. 18-21, 2019.

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In May 2016, Google decided to release an Android API enabling developers and researchers to access GNSS raw data measurements from embedded GNSS chipsets. This initiative potentially allows billions of smartphone users to achieve individual precise positioning [1]. Recently, smartphones’ GNSS capabilities were optimized with the release of multi-constellation and multi-frequency GNSS chipsets such as the Broadcom 47755 in Xiaomi Mi8 [2]. However, in constrained environments, signals degradation prevents mobile users to obtain sub-metric precision especially due to the linearly polarized smartphones’ GNSS antenna. To overcome this, a smartphone collaborative positioning method will be developed and implemented, within a network of users, in order to exchange qualitative GNSS information. These exchanged data are derived from signals degradation status, quality, availability and integrity obtained via other users and abundant data from today’s urban environment. In the interest of developing this method, measurements error models must be established for different GNSS chipsets/smartphones, in an urban environment. The aim of this paper is then to draw statistical measurements models in order to characterize Android GNSS raw data measurements. Therefore, we analyzed GNSS raw data measurements obtained during a data collection campaign in Toulouse, France. Two vehicles, equipped with geodetic grade receivers, antenna and IMUs for reference purposes, were used in this campaign to collect data from seven recent smartphones (Xiaomi Mi9, Google Pixel 3, Huawei Mate 20X, 2 Honor View 20 and two Xiaomi Mi8). The structure of this article will be as follows: first, the context of smartphone collaborative positioning is presented. Thereafter, the protocol of the data collection campaign will be described in detail and different collaborative scenarios will be introduced. Finally, the statistical analysis will be made for the different scenarios and a generalized method will be extracted in order to characterize any smartphone embedded GNSS chipset’s measurements.

Digital communications / Localization and navigation

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Répartition équitable des flux dans les Named Data Networking

Authors: Thibaud Adrien, Chaput Emmanuel, Fasson Julien, Arnal Fabrice and Sallantin Renaud

Seminar of TeSA, Toulouse, November 6, 2019.

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Le nouveau paradigme Information Centric Network (ICN), et en particulier l'architecture Named Data Networking (NDN), redéfinissent une couche réseau accès sur le contenu. En effet, les tendances d'utilisation d'Internet ont bien évoluées depuis l'invention d'IP (Youtube, Netflix, ...). Ce nouveau type de réseau promet une utilisation plus intelligente du réseau pour garantir une meilleure Qualité d’Expérience à ses utilisateurs. Mais qu'en est-il vraiment ? Après une description des principales caractéristiques de NDN, nous vous proposons de vous présenter une solution pour répartir équitablement les flux des différents utilisateurs dans ce type de réseau.

Networking / Space communication systems

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

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

Seminar of TeSA, Toulouse, November 6, 2019.

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L'objectif général de la présentation est de déterminer les performances des futurs signaux 5G en terme de positionnement. Pour ce faire, l'étude se focalise sur la définition d'un modèle mathématique de sorties de corrélateurs 5G. D'après les standards 3GPP, la 5G utilisera des signaux OFDM (Orthogonal Frequency Division Multiplexing). Dans la littérature, des modèles mathématiques aux différentes étapes du traitement (modulation, démodulation, corrélation, boucle de poursuite,...) pour signaux OFDM sont déjà disponible. Ces modèles sont développés en supposant un canal de propagation constant pendant la durée d'un symbole OFDM. En vue d'adapter ces résultats, ces modèles, à la 5G, il a été nécessaire de sélectionner un canal de propagation répondant aux critères des standards 3GPP pour la 5G. Le choix s'est porté sur le simulateur QuaDRiGa ; une étude approfondie des modèles générés par ce simulateur a montré que le canal de propagation ne pouvait être considéré comme constant sur la durée d'un symbole OFDM. Ainsi, les modèles développés dans la littérature ne sont pas utilisables tels quels. Dans cette présentation, de nouveaux modèles mathématiques, prenant en compte cette évolution de canal, sont développés et appliqués pour le calcul de pseudo- distance 5G.

Digital communications / Localization and navigation

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Conference Paper

Data Decoding Analysis of Next Generation GNSS Signals

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

In Proc. ION Global Navigation Satellite Systems (GNSS), Miami, Florida, USA, September 16-20, 2019.

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Error correcting schemes are fundamental in the new generation of data navigation signals. Thanks to those, the system has the capability to correct possible data navigation errors, which potentially induces delays in first fix of the receiver. In the GNSS receivers, those error correcting schemes use the Log Likelihood Ratio (LLR) as the input of the decoding algorithm. Until now, the LLR was always computed under the Gaussian assumption and considering perfect Complete State Information (CSI), which does not hold in most of the real scenarios. Then, in this paper we proposed several methods to compute the LLR, considering a set of realitic scenarios and considering that perfect CSI is not available at the receiver. We test the proposed LLRs for several new generation GNSS signals.

Signal and image processing and Digital communications / Localization and navigation

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Binary Root Protograph LDPC Codes for CSK Modulation to Increase the Data Rate and Reduce the TTD

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

In Proc. ION Global Navigation Satellite Systems (GNSS), Miami, Florida, USA, September 16-20, 2019.

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New generation of GNSS systems seeks to provide new features in order to create or to improve their currents services. Between those possible features; the increase of the data rate is necessary in order to to provide services such as authentication, precise positioning or reduce the Time-To-First-Fix (TTFF). On the other hand, the data availability in harsh environment suggest the need of error correcting technologies. Then, based on previous works over the Code-Shift Keying (CSK) modulation and in Root Protograph LDPC code to reduce the TTFF, in this paper, it is presented the optimization of Root Protograph LDPC codes for the CSK modulation in a Bit-Interleaved Coded Modulation context and the optimization of Root Protograph LDPC codes for the CSK modulation in Bit-Interleaved Coded Modulation Iterative Decoding context. Both optimization where base on the Protograph EXIT chat algorithm, providing promising results.

Signal and image processing and Digital communications / Localization and navigation

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Optimal Channel Coding Structures for Fast Acquisition Signals in Harsh Environment Conditions

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

In Proc. ION Global Navigation Satellite Systems (GNSS), Miami, Florida, USA, September 16-20, 2019.

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In this article, we provide the method to construct two error correcting structures for GNSS systems, which are capable to provide Maximum Distance Separable (MDS), full diversity and rate-compatible properties. Thanks to those properties, the GNSS receiver is capable to reduce the Time-To-First-Fix (TTFF) and to enhance the robustness of the data demodulation under low Carrier to Noise ratio environments, urban environments and pulsed jamming environments. The proposed error correcting structures are then simulated and compared with the GPS L1C subframe 2 error correcting scheme under the precedent transmission environments. Simulations show an outstanding improvement of the error correction capabilities (which reduce the TTFF in harsh environments) mainly caused by the rate-compatible and the full diversity properties. Moreover, thanks to the MDS property a high reduction of the TTFF under good environments is appreciated.

Signal and image processing and Digital communications / Localization and navigation

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Talk

Robust Statistics for GNSS Positioning

Author: Medina Daniel

Seminar of TeSA, Toulouse, July 10, 2019.

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Signal and image processing / Localization and navigation

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Robust Global Navigation Satellite Systems

Author: Closas Pau

Seminar of TeSA, Toulouse, July 10, 2019.

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Signal and image processing / Localization and navigation

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Activity Report

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Pau Closas, Northeastern Univ Boston, in TeSA

TeSA welcomes him with a research fellowship for July!

INP INNOV' 2019

Plenty of laurels for TeSA: congratulations to all!