Scientific Production

SEARCH

Search

Conference Paper

Un algorithme de reconstruction dans le cas d’un échantillonnage non ponctuel, périodique ou non

Authors: Bonacci David and Lacaze Bernard

In Proc. Groupement de Recherche en Traitement du Signal et des Images (GRETSI), Juan-Les-Pins, France, September 5-8, 2017.

DOWNLOAD DOCUMENT

Les composants électroniques destinés à l’échantillonnage haute fréquence des signaux ont des temps de réponse susceptibles de dégrader les performances des algorithmes de reconstruction. Dans cet article, on considère un signal échantillonné par un composant modélisé par un filtre linéaire invariant activé à des instants potentiellement irréguliers et qui forment une suite vérifiant la condition de Landau (généralisation de la condition de Nyquist). On étudie les conséquences des imperfections des échantillonneurs dans la reconstruction du signal et dans l’estimation de l’enveloppe et de la phase.

Signal and image processing / Space communication systems

READ MORE

Sur l’égalisation fréquentielle des modulations à phase continue

Authors: Chayot Romain, Thomas Nathalie, Poulliat Charly, Boucheret Marie-Laure, Van Wambeke Nicolas and Lesthievent Guy

In Proc. Groupement de Recherche en Traitement du Signal et des Images (GRETSI), Juan-Les-Pins, France, September 5-8, 2017.

DOWNLOAD DOCUMENT

Dans cet article, nous proposons d’étudier différents algorithmes d’égalisation pour signaux à Modulation de Phase Continue (continuous phase modulation, CPM) dans le domaine fréquentiel à l’aide d’une représentation polyphase du signal. Par cette approche unifiée, nous montrons l’équivalence analytique de ces égaliseurs sous certaines hypothèses liées au canal de transmission, les liens, ainsi que leurs limitations dans certains cas.

Digital communications / Aeronautical communication systems and Space communication systems

READ MORE

Shape Effects on Sampling of Stationary Processes

Authors: Bonacci David and Lacaze Bernard

In Proc. Sampling Theory and Applications (SampTA), 12th International Conference, Tallinn, ESTONIA, July 3-7, 2017.

DOWNLOAD DOCUMENT

Acquisition devices play an important role in digital signal processing. The possibility of a perfect reconstruction is demonstrated in regular as well as irregular sampling when the number of samples in the observation interval is high enough in function of the bandwidth of the sampled signal (length of the support of the spectrum). In the case of high sampling rates, imperfections of acquisition devices can introduce non negligible errors (when the acquisition duration of a given sample becomes not negligible in comparison with the sampling period (or mean sampling period in the case of irregular sampling). In this paper, explicit method is proposed to take into account imperfections of the sampling device in order to improve the reconstruction of the signal. The proposed method is applicable for deterministic functions and random processes in the case of regular sampling, as well as irregular sampling.

Signal and image processing / Space communication systems

READ MORE

On Sparse Graph Coding for Coherent and Noncoherent Demodulation

Authors: Piat-Durozoi Charles-Ugo, Poulliat Charly, Thomas Nathalie, Boucheret Marie-Laure and Lesthievent Guy

In Proc. International Symposium on Information Theory (ISIT), Aachen, Germany, June 25-30, 2017.

DOWNLOAD DOCUMENT

In this paper, we consider a bit-interleaved coded modulation scheme (BICM) composed of an error correcting code serially concatenated with a M-ary non linear modulation with memory. We first compare demodulation strategies for both the coherent and the non coherent cases. Then, we perform an asymptotic analysis and try to show that the design of coding schemes performing well for both the coherent and the non coherent regimes should be done carefully when considering sparse graph based codes such as low-density parity-check (LDPC) codes. It will be shown that optimized coding schemes for the non coherent setting can perform fairly well when using coherent demodulation, while on the contrary, optimized coding schemes for the coherent setting may lead to ”non stable” coding schemes in the non coherent setting.

READ MORE

Talk

Livraison de contenu sur réseau hybride satellite-terrestre

Authors: Bouttier Élie, Dhaou Riadh, Arnal Fabrice, Baudoin Cédric, Dubois Emmanuel and Beylot André-Luc

Seminars of TéSA, Toulouse, April 19, 2016.

DOWNLOAD DOCUMENT

Networking / Other

READ MORE

Continuous Phase Modulation - A short Introduction

Authors: Piat-Durozoi Charles-Ugo and Chayot Romain

Seminars of TéSA, Toulouse, April 19, 2016.

DOWNLOAD DOCUMENT

Digital communications / Aeronautical communication systems and Space communication systems

READ MORE

Journal Paper

On Lower Bounds for Nonstandard Deterministic Estimation

Authors: Kbayer Nabil, Galy Jérôme, Chaumette Eric, Vincent François, Renaux Alexandre and Larzabal Pascal

IEEE Transactions on Signal Processing, vol. 65, n° 6, pp. 1538-1553, March, 2017.

DOWNLOAD DOCUMENT

We consider deterministic parameter estimation and the situation where the probability density function (p.d.f.) parameterized by unknown deterministic parameters results from the marginalization of a joint p.d.f. depending on random variables as well. Unfortunately, in the general case, this marginalization is mathematically intractable, which prevents from using the known standard deterministic lower bounds (LBs) on the mean squared error (MSE). Actually the general case can be tackled by embedding the initial observation space in a hybrid one where any standard LB can be transformed into a modified one fitted to nonstandard deterministic estimation, at the expense of tightness however. Furthermore, these modified LBs (MLBs) appears to include the submatrix of hybrid LBs which is an LB for the deterministic parameters.Moreover, since in the nonstandard estimation, maximum likelihood estimators (MLEs) can be no longer derived, suboptimal nonstandard MLEs (NSMLEs) are proposed as being a substitute. We show that any standard LB on the MSE of MLEs has a nonstandard version lower bounding the MSE of NSMLEs. We provide an analysis of the relative performance of the NSMLEs, as well as a comparison with the MLBs for a large class of estimation problems. Last, the general approach introduced is exemplified, among other things, with a new look at the well-known Gaussian complex observation models.

Signal and image processing / Aeronautical communication systems, Earth observation, Localization and navigation and Space communication systems

READ MORE

Conference Paper

Multisymbol with Memory Noncoherent Detection of CPFSK

Authors: Piat-Durozoi Charles-Ugo, Poulliat Charly, Boucheret Marie-Laure, Thomas Nathalie, Bouisson Emmanuel and Lesthievent Guy

In Proc. IEEE Int. Conf. Acoust., Speech and Signal Proces. (ICASSP), La Nouvelle-Orléans, Louisiane-USA, March 5-9, 2017.

DOWNLOAD DOCUMENT

Multisymbol receiver is an effective method to demodulate noncoherent sequences. However it is necessary to correlate an important number of symbols in a noncoherent scheme to reach the performances carried out by optimal coherent Maximum a Posteriori (MAP) detectors such as BCJR. In this paper, we propose an advanced multisymbol receiver by adding some memory to the decision process. The advanced receiver, called here Multisymbol With Memory (MWM) takes into account the cumulative phase information unlike multisymbol algorithm and thus it can be seen as a truncated BCJR. An exact mathematical derivation is performed for this truncated BCJR. Then an implementation of the MWM detector applied to a continuous phase frequency shift keying modulation is presented. Finally an asymptotic analysis is carried out based on the achievable Symmetric Mutual Information rate. The proposed system exhibits good performances compared to classical multisymbol receivers at the expense of increased complexity and can approach the performances of a coherent receiver.

Digital communications / Space communication systems

READ MORE

Joint Channel and Carrier Frequency Estimation for M-ARY CPM over Frequency-Selective Channel using PAM Decomposition

Authors: Chayot Romain, Boucheret Marie-Laure, Poulliat Charly, Thomas Nathalie, Van Wambeke Nicolas and Lesthievent Guy

In Proc. IEEE Int. Conf. Acoust., Speech and Signal Proces. (ICASSP), La Nouvelle-Orléans, Louisiane-USA, March 5-9, 2017.

DOWNLOAD DOCUMENT

In this paper, we present a new data-aided carrier-recovery method for Continuous Phase Modulation (CPM) signals over frequency-selective channels. We first present a linear model of the received signal based on Mengali representation over selective channels and show how to use it to perform joint channel and carrier-frequency estimation. We also derive a low-complexity version of the estimator. Simulation results show that this method performs better than the optimal method suited to the Additive White Gaussian Noise (AWGN) channels.

Digital communications / Aeronautical communication systems and Space communication systems

READ MORE

Estimation Accuracy of Non-Standard Maximum Likelihood Estimators

Authors: Kbayer Nabil, Galy Jérôme, Chaumette Eric, Vincent François, Renaux Alexandre and Larzabal Pascal

In Proc. IEEE Int. Conf. Acoust., Speech and Signal Proces. (ICASSP), La Nouvelle-Orléans, Louisiane-USA, March 5-9, 2017.

DOWNLOAD DOCUMENT

In many deterministic estimation problems, the probability density function (p.d.f.) parameterized by unknown deterministic parameters results from the marginalization of a joint p.d.f. depending on additional random variables. Unfortunately, this marginalization is often mathematically intractable, which prevents from using standard maximum likelihood estimators (MLEs) or any standard lower bound on their mean squared error (MSE). To circumvent this problem, the use of joint MLEs of deterministic and random parameters are proposed as being a substitute. It is shown that, regarding the deterministic parameters : 1) the joint MLEs provide generally suboptimal estimates in any asymptotic regions of operation yielding unbiased efficient estimates, 2) any representative of the two general classes of lower bounds, respectively the Small-Error bounds and the Large-Error bounds, has a ”non-standard” version lower bounding the MSE of the deterministic parameters estimate.

Signal and image processing / Aeronautical communication systems, Earth observation, Localization and navigation and Space communication systems

READ MORE

TeSA in New Orleans

Charles-Ugo Piat-Durozoi (left) and Romain Chayot (right) presented papers at ICASSP 2017 last March, supported by Corinne Mailhes (center).

PhD positions available at TeSA

PhD subjects available on the CNES site.
On line application before the 31rst of March.

READ MORE

Welcome to our 3 new PhD students: Adrien, Lorenzo and Selma (from left to right).