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Conference Paper

Modélisation des signaux altimétriques en présence de pics

Authors: Halimi Abderrahim, Mailhes Corinne, Tourneret Jean-Yves and Thibaut Pierre

In Proc. Groupement de Recherche en Traitement du Signal et des Images (GRETSI), September 5-8, 2011.

Coastal altimetric waveforms may be corrupted by peaks. A simple parametric model was recently introduced to model peaky altimetric waveforms. This model assumes that the received altimetric waveform is the sum of a Brown echo and a Gaussian peak. This model has provided interesting results for symmetric peaks affecting altimetric signals. However, it is not appropriate for altimetric signals corrupted by asymmetric peaks. This paper introduces a Brown with asymmetric Gaussian peak model for altimetric waveforms. The parameters of this model are estimated by a maximum likelihood estimator. The performance of the proposed model and the resulting estimation strategy are evaluated via simulations conducted on synthetic and real data.

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Signal and image processing / Earth observation

Segmentation des signaux ECG et caractérisation des ondes P et T à l'aide d'un échantillonneur de Gibbs par bloc

Authors: Lin Chao, Kail Georg, Mailhes Corinne, Tourneret Jean-Yves and Hlawatsch Franz

In Proc. Groupement de Recherche en Traitement du Signal et des Images (GRETSI), September 5-8, 2011.

The delineation of P and T waves is important for the medical interpretation of ECG signals. We propose a Bayesian algorithm for simultaneous detection, delineation, and estimation of P and T waves. A block Gibbs sampler exploits the strong local dependencies in ECG signals by imposing block constraints on the P and T wave locations. The proposed algorithm is evaluated on the annotated QT database and compared with two classical algorithms.

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Signal and image processing / Other

Sonar and Radar SAR Processing for Parking Lot Detection

Authors: Mure-Dubois James, Vincent François and Bonacci David

In Proc. International Radar Symposium (IRS), Leipzig, Germany, September 7-9, 2011

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In this paper, SAR processing algorithms for automotive applications are presented and illustrated on data from non-trivial test scenes. The chosen application is parking lot detection. Laboratory results obtained with a teaching sonar experiment emphasize the resolution improvement introduced with range-Doppler SAR processing. A similar improvement is then confirmed through full scale measurements performed with an automotive radar prototype operating at 77GHz in very close range conditions, typical of parking lot detection. The collected data allows a performance comparison between different SAR processing algorithms for realistic targets.

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Signal and image processing / Other

Une technique de correction d’erreur basée sur le CRC pour des systèmes codés en treillis contenant des bits de bourrage

Authors: Prévost Raoul, Coulon Martial, Bonacci David, Le Maitre Julia, Millerioux Jean-Pierre and Tourneret Jean-Yves

In Proc. Groupement de Recherche en Traitement du Signal et des Images (GRETSI), Bordeaux, France, September 5-8, 2011.

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This paper introduces a new error correction strategy using cyclic redundancy checks (CRC) for a trellis coded system in the presence of bit stuffing. The proposed receiver is designed to simultaneously demodulate, decode and correct the received message in the presence of bit stuffing. It is based on a Viterbi algorithm exploiting the conditional transitions of an appropriate extended trellis. The receiver is evaluated with automatic identification system (AIS) messages constructed with a 16 bit CRC and a Gaussian Minimum Shift Keying (GMSK) modulation. The stuffed bits are inserted after any sequence of five consecutive bits 1 as requested by the AIS recommendation. Simulation results illustrate the algorithm performance in terms of packet error rate. A gain of more than 2,5 dB is obtained when compared to the conventional GMSK receiver.

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Digital communications / Localization and navigation and Space communication systems

T-wave Alternans Detection Using a Bayesian Approach and a Gibbs Sampler

Authors: Lin Chao, Mailhes Corinne and Tourneret Jean-Yves

in Proc. IEEE Int. Conf. on Eng. Medicine Biol. Soc. (EMBC), Boston, MA, pp. 5868-5871, August, 2011.

The problem of detecting T-wave alternans (TWA) in ECG signals has received considerable attention in the biomedical community. This paper introduces a Bayesian model for the T waves contained in ECG signals. A block Gibbs sampler was recently studied to estimate the parameters of this Bayesian model (including wave locations, amplitudes and shapes). This paper shows that the samples generated by this Gibbs sampler can be used efficiently for TWA detection via different statistical tests constructed from odd and even T-wave amplitude samples. The proposed algorithm is evaluated on real ECG signals subjected to synthetic TWA and compared with two classical algorithms.

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Signal and image processing / Other

A Network Calculus Model for SpaceWire Networks

Authors: Ferrandiz Thomas, Frances Fabrice and Fraboul Christian

In Proc. IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2011), Toyama, Japan, August 28-31, 2011.

Space Wire is a wormhole network standard scheduled to be used as the sole on-board network for future satellites by the ESA. As the network will be shared by real-time and non real-time traffic, network designers require a tool to check that temporal constraints are verified for all the urgent messages. Previously, we proposed a model for a best-effort worm-hole network based on Network Calculus theory. This model is based on new network element that we call the Wormhole Section. Here, we show how to combine Wormhole Section elements to compute the end-to-end service curve offered to a flow and illustrate its use on a industrial case study.

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Networking / Other

A New Model for Peaky Altimetric Waveforms

Authors: Halimi Abderrahim, Mailhes Corinne, Tourneret Jean-Yves and Thibaut Pierre

in Proc. IEEE Int. Geosci. Remote Sens. Symp. (IGARSS), Vancouver, Canada, July 25-29, 2011.

Coastal altimetric waveforms may be corrupted by peaks. A simple parametric model was recently introduced to model peaky altimetric waveforms. This model assumes that the received altimetric waveform is the sum of a Brown echo and a Gaussian peak. This model has provided interesting results for symmetric peaks affecting altimetric signals. However, it is not appropriate for altimetric signals corrupted by asymmetric peaks. This paper studies a Brown with asymmetric Gaussian peak model for parameter estimation of altimetric waveforms. The parameter estimation problem is solved by a maximum likelihood estimator relying on an optimization algorithm. The performance of the proposed model and the resulting estimation strategy is evaluated via simulations conducted on synthetic and real data.

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Signal and image processing / Earth observation

Journal Paper

Spectral and Power-Efficient Data Multiplexing Format Based on Code-Shift-Keying

Authors: Dudal Clément, Boucheret Marie-Laure, Lops Marco, Thomas Nathalie and Dervin Mathieu

IEEE Communications letters, vol. 15, n° 7, pp. 695-697, July, 2011.

This paper proposes a spectral- and power- efficient code division multiplexing (CDM) scheme based on code shift keying (CSK) for the down-link of a communication system subject to additive Gaussian noise (e.g., the forward link of a satellite communication system). In a CSK system, each active user is assigned a set of sequences taken from Gold codes and their cyclic shifts. Spectral efficiency can be achieved by multiplexing several CSK modulators. We first define the corresponding Maximum-Likelihood (ML) decoder, showing that it can be efficiently implemented through a Sphere Decoding (SD) algorithm. An approximate performance analysis of the proposed scheme is given, and validated through numerical simulations, showing that larger spectral efficiencies also lead to increased power efficiencies.

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Digital communications / Space communication systems

Patent

Procédé et dispositif de détection d'une cible masquée par des réflecteurs de forte énergie

Authors: Vincent François and Goy Jean-Philippe

n° EP 2544020 A1, n° EP 2544020 B1, n° US20130176162, July 2011.

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Signal and image processing / Localization and navigation

Journal Paper

Using Network Calculus to Compute End to End Delays in Space Wire Networks

Authors: Ferrandiz Thomas, Frances Fabrice and Fraboul Christian

ACM SIGBED Review, vol. 8, n° 3, pp. 44-47, 2011.

The SpaceWire network standard is promoted by the ESA and is scheduled to be used as the sole on-board network for future satellites. This network uses a wormhole routing mechanism that can lead to packet blocking in routers and consequently to variable end-to-end delays. As the network will be shared by real-time and non real- time traffic, network designers require a tool to check that temporal constraints are verified for all the critical messages. Network Calculus can be used for evaluating worst- case end-to-end delays. However, we first have to model SpaceWire components through the definition of service curves. In this paper, we propose a new Network Calculus element that we call the Wormhole Section. This element allows us to better model a wormhole network than the usual multiplexer and demultiplexer elements used in the context of usual Store-and-Forward networks.

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Networking / Other

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