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Article de conférence

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), pp. 5689-5694, 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 conférence

Intrinsic Slepian-Bangs Type Formula for Parameters on LGs with Unknown Measurement Noise Variance

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

In Proc. 2023 57th Asilomar Conference on Signals, Systems, and Computers, pp. 887-891, Pacific Grove, CA, USA, 29 Oct.-1 Nov. 2023.

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Intrinsic lower bounds on the intrinsic mean square error are of major importance to characterize the best achievable estimation performance of any unbiased estimator on smooth manifold as Lie group (LG). When the parameter is described by a LG model and the observation noise is with unknown variance, it is also necessary to determine a bound both on the LG parameter and this variance. In this communication, we propose an intrinsic generic Fisher information matrix taking into account this problem. To achieve that, we derive an intrinsic Slepian-Bangs formula on the LG product of the unknown parameter of interest and the LG of positive scalar values in which the variance intrinsically lies. The proposed bound is validated on a Gaussian observation model for unknown parameter lying to SE (3) and variance noise on R+.

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

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

Article de conférence

Joint Registration and Fusion of 3D Mgnetic Resonance and 2D Ultrasound Images for Endometriosis Surgery

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

In Proc. 31st EUropean SIgnal Processing COnference (EUSIPCO 2023), Helsinki, Finland, September 4-8, 2023.

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This paper investigates a general framework for the registration of 3D magnetic resonance (MR) and 2D ultrasound (US) images. This framework is divided into a rigid slice-tovolume 3D-2D MR/US registration and a 2D-2D US/MRI fusion algorithm to generate an image having a better resolution than the MR image and a better contrast than the US image. The accuracy of the joint registration and fusion method is analyzed by means of quantitative and qualitative tests conducted on experimental phantom and realistic synthetic data generated from an in vivo MRI volume, with a specific attention to endometriosis treatment.

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Traitement du signal et des images / Autre

An EM Approach for GNSS Parameters of Interest Estimation Under Constant Modulus Interference

Auteurs : Lesouple Julien et Ortega Espluga Lorenzo

In Proc. 31st EUropean SIgnal Processing COnference (EUSIPCO 2023), Helsinki, Finland, September 4-8, 2023.

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Interferences are an important threat for applications relying on Global Navigation Satellite Systems (GNSS). Interferences degrade GNSS performance, and can lead to denial of service. The most notable intentional interference family is characterized by its constant envelope, e.g. chirp and tone interferences. Due to its simple structure, the space to search the interference contribution yields to complex circles, allowing the introduction of some latent variables related to those circles. In order to mitigate the interference effect, we compute the maximum likelihood estimator of the parameters of interest (time delay and Doppler shift) in presence of those latent variables. Thus, we resort to the Expectation Maximization algorithm which has already been proved to be efficient in such cases. Experiments conducted on synthetic signals highlight the efficiency of the proposed algorithm.

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

Article de journal

GNSS Channel Coding Structures for Fast Acquisition Signals in Harsh Environment Conditions.

Auteurs : Ortega Espluga Lorenzo et Poulliat Charly

Navigation-Journal of Navigation, doi: 10.33012/navi.585, September, 2023.

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In this article, we investigate on a new method to jointly design the navigation message with an error correcting scheme. This joint design exploits the "carousel" nature of the broadcasted navigation message and allows both: i) to reduce the Time To First Fix (TTFF) and ii) to enhance the error correcting performances under favorable and challenging channel conditions. We show that the joint design requires error correcting schemes characterized by Maximum Distance Separable (MDS) and the full diversity properties. Those error correcting codes are referred to as Root LowDensity Parity Check (Root-LDPC) codes and they can efficiently operate on block varying channels, enabling the efficient and rapid recovery of information over possibly non ergodic channels. Finally, in order to ensure the data demodulation performance over harsh condition, we propose Root-LDPC codes endowed with the nested property, which allows to inherently adapt the channel coding rate depending on the number of received blocks. The proposed error correcting joint design is then simulated and compared with the well-known GPS L1C subframe 2 structure under several transmission scenarios. Simulations showthatwe can have some enhancement of the error correction performance and a reduction of the TTFF for some scenarios.

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

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