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Article de conférence

Scalable Syndrome-based Neural Decoders for Bit-Interleaved Coded Modulations

Auteurs : De Boni Rovella Gastón, Benammar Meryem, Benaddi Tarik et Meric Hugo

In Proc. IEEE International Conference on Machine Learning for Communication and Networking (ICMLCN 2024), Stockholm, Sweden, May 5-8, 2024.

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In this work, we introduce a framework that enables the use of Syndrome-Based Neural Decoders (SBND) for highorder Bit-Interleaved Coded Modulations (BICM). To this end, we extend the previous results on SBND, for which the validity is limited to Binary Phase-Shift Keying (BPSK), by means of a theoretical channel modeling of the bit Log-Likelihood Ratio (bit-LLR) induced outputs.We implement the proposed SBND system for two polar codes (64, 32) and (128, 64), using a Recurrent Neural Network (RNN) and a Transformer-based architecture. Both implementations are compared in Bit Error Rate (BER) performance and computational complexity.

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Communications numériques / Systèmes spatiaux de communication et Autre

Séminaire

Calcul Quantique : Graal de l’optimisation ou Mirage de la puissance ?

Auteur : Gondran Alexandre

Seminar of TeSA, Toulouse, February 9, 2024.

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Réseaux / Autre

Article de journal

On the GNSS Synchronization Performance Degradation under Interference Scenarios: Bias and Misspecified CRB

Auteurs : Ortega Espluga Lorenzo, Lubeigt Corentin, Vilà-Valls Jordi et Chaumette Eric

Navigation-Journal of Navigation, doi: 10.33012/navi.606, December 2023.

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Global navigation satellite systems (GNSS) are a key player in a plethora of applications, ranging from navigation and timing, to Earth observation or space weather characterization. For navigation purposes, interference scenarios are among the most challenging operation conditions, which clearly impact the maximum likelihood estimates (MLE) of the signal synchronization parameters. While several interference mitigation techniques exist, a theoretical analysis on the GNSS MLE performance degradation under interference, being fundamental for system/receiver design, is a missing tool. The main goal of this contribution is to provide such analysis, by deriving closed-form expressions of the misspecified Cramér-Rao (MCRB) bound and estimation bias, for a generic GNSS signal corrupted by an interference. The proposed bias and MCRB expressions are validated for a linear frequency modulation chirp signal interference.

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Traitement du signal et des images / Localisation et navigation et Systèmes spatiaux de communication

Article de conférence

Time-Delay and Doppler Estimation with a Carrier Modulated by a Band-Limited Signal

Auteurs : Bernabeu Frias Joan Miguel, Ortega Espluga Lorenzo, Blais Antoine, Gregoire Yoan et Chaumette Eric

In Proc. IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), Los Sueños, Costa Rica, December 10-13, 2023.

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Since time-delay and phase estimation is a fundamental task in a plethora of engineering fields, several CRB and MLE expressions have been derived for the past decades. In all these previous works, a common hypothesis is that the wave transmission process introduces an unknown phase which prevents from estimating both delay and transmission phase components. By revisiting this problem, including the derivation of the MLE and the associated CRB, we show that this well-admitted assertion is not true strictly: both informations can be estimated, but generally with a sub-optimal achievable MSE in the asymptotic region. Moreover, since practical problems exist where the transmission phase can be estimated apart, adding this additionnal measure to the observation model provides a setting allowing to explore the contribution of each signal component (carrier frequency, baseband signal and transmission phase measure) to the achievable MSE of time-delay and phase estimation in the asymptotic region.

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Traitement du signal et des images / Systèmes de communication aéronautiques et Systèmes spatiaux de communication

Fusion of Ultrsound and Magnetic Resonance Images for Endometriosis Diagnosis : a Non-Parametric Approach

Auteurs : El Bennioui Youssra, Bruguier Alexandre, Vidal Fabien, Basarab Adrian et Tourneret Jean-Yves

In Proc. IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), Los Sueños, Costa Rica, December 10-13, 2023.

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A fusion method was recently proposed for ultrasound and magnetic resonance images for endometriosis diagnosis. This method combined the advantages of each modality, i.e., the good contrast and signal to noise ratio of the MR image and the good spatial resolution of the US image. The method was based on an inverse problem, performing a superresolution of the MR image and a denoising of the US image. A polynomial function was introduced to model the relationships between the gray levels of the MR and US images. This paper studies the potential interest of replacing this polynomial function by a non-parametric transformation built using the theory of reproducing kernel Hilbert spaces. Simulations conducted on a phantom and synthetic data allow the performance of the resulting fusion method to be appreciated.

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Traitement du signal et des images / Autre

Improved Syndrome-based Neural Decoder for Linear Block Codes

Auteurs : De Boni Rovella Gastón et Benammar Meryem

In Proc. IEEE Global Communications Conference (GLOBECOM 2023), Kuala Lumpur, Malaysia, December 4-8, 2023.

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In this work, we investigate the problem of neuralbased error correction decoding, and more specifically, the new so-called syndrome-based decoding technique introduced to tackle scalability in the training phase for larger code sizes. We improve on previous works in terms of allowing full decoding of the message rather than codewords, allowing thus the application to nonsystematic codes, and proving that the single-message training property is still viable. The suggested system is implemented and tested on polar codes of sizes (64,32) and (128,64), and a BCH of size (63,51), leading to a significant improvement in both Bit Error Rate (BER) and Frame Error Rate (FER), with gains between 0.3dB and 1dB for the implemented codes in the high Signal-to-Noise Ratio (SNR) regime.

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Communications numériques / Systèmes spatiaux de communication

Séminaire

Introduction aux Blockchains et à leurs Applications

Auteur : Lacan Jérôme

Seminar of TeSA, Toulouse, November 30, 2023.

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Réseaux / Autre

Introduction à la Cryptographie Post-Quantique

Auteur : Deneuville Jean-Christophe

Seminar of TeSA, Toulouse, November 30, 2023.

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Réseaux / Autre

Article de journal

Barankin, McAulay–Seidman and Cramér–Rao bounds on matrix Lie groups

Auteurs : Labsir Samy, Renaux Alexandre, Vilà-Valls Jordi et Chaumette Eric

Automatica, vol. 156, pp. 111-199, October 2023.

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In this article, we first derive a general intrinsic Barankin bound (IBB) for unknown parameters lying on Lie groups (LGs), and its intrinsic McAulay-Seidman bound (IMSB) approximation. Second, the IMSB expression is used to revisit the intrinsic Cramér-Rao bound (ICRB) on LGs. Indeed, an analytic expression of the ICRB, which is a special IMSB case, is obtained from the latter. Finally, closed-form expressions for both IMSB and ICRB are obtained for Euclidean and LG observation models depending on parameters lying in SO(3) and SE(3). The validity of the these IMSB and ICRB expressions, with respect to the intrinsic mean square error, is shown via numerical simulations to support the discussion.

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Traitement du signal et des images / Systèmes spatiaux de communication

Approximate Maximum Likelihood Time-Delay Estimation for Two Closely Spaced Sources

Auteurs : Lubeigt Corentin, Vincent François, Ortega Espluga Lorenzo, Vilà-Valls Jordi et Chaumette Eric

Signal processing, vol. 210, 109056, September, 2023.

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The study of ground reflections of Global Navigation Satellite System (GNSS) signals, as in GNSS Reflectometry (GNSS-R) can lead to the receiver height estimation. The latter is estimated by comparing the time of arrival difference between the direct and reflected signals, also called path separation. In ground-based scenarios, this path separation can be very small, inducing important interference between paths, which makes it difficult to correctly obtain altimetry products. The path separation estimation can be obtained by a brute force dual source maximum likelihood estimator (2S-MLE), but this solution has a large computational cost. On the other hand, the path separation is so small that a number of approximations can be done. In this study, a third order Taylor approximation of the dual source likelihood criterion is proposed to reduce its complexity. The proposed algorithm performance is compared to the non approximated 2S-MLE for the estimation of the path separation, and to a standard single source processing for the estimation of the direct signal time-delay. These results, along with the corresponding lower bounds, prove that the proposed approach may be of interest for two applications: ground-based GNSS-R altimetry (or radar with low elevation targets) and GNSS multipath mitigation.

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Traitement du signal et des images / Localisation et navigation et Systèmes spatiaux de communication

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