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Conference Paper
Advanced Co-Design of Message Structure and Channel Coding Scheme to Reduce the Time to CED and to Improve the Resilience for a Galileo 2nd Generation New Signal
In Proc. ESA Workshop on Satellite Navigation Technologies and European Workshop on GNSS Signals and Signal Processing (NAVITEC), Noordwijk, The Netherlands, December 5-7, 2018.
Reducing the Time To First Fix (TTFF) and improving the resilience of future Galileo signals are two important characteristics, especially when considering urban environments. To reach these goals, we studied two new advanced techniques based on the co-design of the message structure and the channel coding scheme. The first technique proposes a reduction of time needed to retrieve the data by reinforcing the parity check matrix structure constraints. The second technique provides an enhancement of the retrieved data error rate in parallel to a reduction of the time needed to retrieve the data thanks to a new co-design requirement based on a family of codes inspired from the rate-compatible root LDPC codes. The results obtained are promising, since the time to retrieve the data (and thus the TTFF) is significantly reduced, while keeping a good level of demodulation performance.
Digital communications / Localization and navigation and Space communication systems
PhD Thesis
On the interaction between transport protocols and link-layer reliability schemes for satellite mobile services
Defended on December 12, 2018.
Networking / Space communication systems
PhD Defense Slides
ON THE INTERACTION BETWEEN TRANSPORT PROTOCOLS AND LINK-LAYER RELIABILITY SCHEMES FOR SATELLITE MOBILE SERVICES
Defended on December 6, 2018.
Networking / Space communication systems
Conference Paper
Physical Layer Abstraction for Performance Evaluation of LEO Satellite Systems for IoT using Time-Frequency Aloha Scheme
In Proc. 6th IEEE Global Conference on Signal and Information Processing (GlobalSIP), Anaheim, California, USA, November 26–29, 2018.
One of the main issues in using a Low Earth Orbit (LEO) satellite constellation to extend a Low-Powered Wide Area Network is the frequency synchronization. Using a link based on random access solves this concern, but also prevents delivery guarantees, and implies less predictable performance. This paper concerns the estimation of Bit Error Rate (BER) and Packet Error Rate (PER) using physical layer abstractions under a time and frequency random scheme, namely Time and Frequency Aloha. We first derive a BER calculation for noncoded QPSK transmission with one collision. Then, we use the 3GPP LTE NB-IoT coding scheme. We analyze the interference that could be induced by repetition coding scheme and propose an efficient summation to improve the decoder performance. Finally, to estimate a PER for any collided scenario, we propose a physical layer abstraction, which relies on an equivalent Signal-to-Noise Ratio (SNR) calculation based on Mutual Information.
Digital communications / Space communication systems
PhD Thesis
Nouvelle forme d’onde et récepteur avancé pour la télémesure des futurs lanceurs
Defended on November 27, 2018.
Les modulations à phase continue (CPMs) sont des methodes de modulations robuste à la non-cohérence du canal de propagation. Dans un context spatial, les CPM sont utilisées dans la chaîne de transmission de télémesure de la fusée. Depuis les années 70, la modulation la plus usitée dans les systèmes de télémesures est la modulation CPFSK continuous phase frequency shift keying filtrée. Historiquement, ce type de modulation est concaténée avec un code Reed-Solomon (RS) afin d’améliorer le processus de décodage. Côté récepteur, les séquences CPM non-cohérentes sont démodulées par un détecteur Viterbi à sortie dure et un décodeur RS. Néanmoins, le gain du code RS n’est pas aussi satisfaisant que des techniques de codage moderne capables d’atteindre la limite de Shannon. Actualiser la chaîne de communication avec des codes atteignant la limite de Shannon tels que les codes en graphe creux, implique de remanier l’architecture du récepteur usuel pour un détecteur à sortie souple. Ainsi, on propose dans cette étude d’ élaborer un détecteur treillis à sortie souple pour démoduler les séquences CPM non-ohérentes. Dans un deuxième temps, on concevra des schémas de pré-codages améliorant le comportement asymptotique du récepteur non-cohérent et dans une dernière étape on élabora des codes de parité à faible densité (LDPC) approchant la limite de Shannon.
Digital communications / Space communication systems
PhD Defense Slides
Nouvelle forme d’onde et récepteur avancé pour la télémesure des futurs lanceurs
Defended on November 27, 2018.
Digital communications / Space communication systems
Conference Paper
Joint Design of GNSS Signal and Message Structure for Galileo 2nd Generation
In Proc. 5th International Technical Symposium on Navigation and Timing (ITSNT), Toulouse, France, November 13-16, 2018.
Digital communications / Localization and navigation and Space communication systems
Doubly-Selective Channel Estimation for Continuous Phase Modulation
In Proc. 37th premier international conference for military communications (MILCOM), Los Angeles, USA, October 29-31, 2018.
In this paper, we present two Data-Aided channel estimators for Continuous Phase Modulation (CPM) in the case of transmissions over doubly-selective channels. They both capitalize on the Basis Expansion Model (BEM), widely used for OFDM systems and for Single Carrier transmission with linear modulation. However, in the case of CPM signals, we need to work on a over-sampled received signal (fractionally-spaced representation) as the equalization techniques are also working on the over-sampled received signal. The first one is a classical Least Squares (LS) estimation of the BEM parameters whereas the second channel estimator introduces first a parametric dependence on the paths delays. Indeed, in the case where those delays are known (by estimation or by geometrical consideration as for the aeronautical channel by satellite), the second LS estimation on the BEM parameters is improved and less computationally demanding. Simulations results are provided and show good performance of our parametric LS estimation.
Digital communications / Aeronautical communication systems and Space communication systems
Precoding for Non-coherent detection of continuous phase modulations
In Proc. 37th premier international conference for military communications (MILCOM), Los Angeles, USA, October 29-31, 2018.
Non-coherent trellis based receiver (TBR) is an effective method to demodulate noncoherent continuous-phase modulated sequences. However it requires to increase the observation length to reach the performance of classical coherent TBRs. Furthermore it appears that both receivers offers different behaviours when considered in a bit-interleaved coded modulation (BICM) system using iterative decoding. Indeed, trellis based outer coding schemes performing well in coherent regime generate error floors in non-coherent regime. In this paper, we show that precoding of the continuous phase modulation (CPM) encoder can deal with the latter issue. The optimization of this non-coherent precoding relies on different objectives than the existing precoding methods introduced in the coherent case. The optimization relies on some asymptotic arguments enabling an efficient BICM scheme using iterative decoding. Using the proposed precoding approach enables to remove error floors in the non-coherent regime while enabling transparent use in the coherent case.
Digital communications / Space communication systems
Cardiac Motion Estimation with Dictionary Learning and Robust Sparse Coding in Ultrasound Imaging
In Proc. EEE International Ultrasonics Symposium, Kobe, Japan, October 22-25, 2018.
Signal and image processing / Other
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