This paper studies a data-driven approach to detect faults in flight control systems of civil aircraft. A particular class of failures, referred to as Oscillatory Failure Cases (OFC), impacting the actuator servo loop has motivated the authors to consider a data-driven approach based on distance and correlation measures (see reference [Goupil et al.(2016). A data-driven approach to detect faults in the Airbus flight control system. IFAC-PapersOnLine, 49(17), 52-57] of this paper) leading to promising results compared to the state-of-the-art methods based on analytical redundancy. The present paper extends the formulation and the results of the considered OFC detection approach investigating Support Vector Machine (SVM) techniques to define a more accurate detector based on distance and correlation measures.

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.

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.

This paper studies a maritime vessel detection method based on the fusion of data obtained from two different sensors, namely a synthetic aperture radar (SAR) and an automatic identification system (AIS) embedded in a satellite. In this work we propose a detector that uses the vessel position provided by the AIS system to improve the radar detection performance. The problem is handled by a generalized likelihood ratio test leading to a detector whose test statistics has a simple closed form expression. The distribution of the test statistics under the hypotheses is also determined, allowing theoretical and simulated receiver operational characteristics (ROCs) to be compared. Our results indicate that the proposed method improves detection performance and motivates the joint use of raw radar data with AIS demodulated information for ship detection.

Deriving a meaningful functional brain parcellation is a very challenging issue in task-related fMRI analysis. The joint parcellation detection estimation model addresses this issue by inferring the parcels from fMRI data. However, it requires a priori fixing the number of parcels through an initial mask for parcellation. Hence, this difficult task generally depends on the subject. The proposed automatic parcellation approach in this paper overcomes this limitation at the subject-level relying on a Dirichlet process mixture model combined with a hidden Markov random field to estimate the parcels and their number online. The proposed method adopts a variational expectation maximization strategy for inference. Compared to the model selection procedure in the joint parcellation detection estimation framework, our method appears more efficient in terms of computational time and does not require finely tuned initialization. Synthetic data experiments show that our method is able to estimate the right model order and an accurate parcellation. Real data results demonstrate the ability of our method to aggregate parcels with similar hemodynamic behaviour in the right motor and bilateral occipital cortices while its discriminating power is increased compared to its ancestors. Moreover, the obtained HRF estimates are close to the canonical HRF in both cortices.

This paper addresses the problem of estimating the roll-off factor of a received communication signal. We study two new statistical estimation methods that determine the roll-off factor by minimizing the difference between the theoretical and empirical power or power spectral density of the received signal. Another interesting contribution is the derivation of the roll-off Cramér–Rao bound which provides a reference in terms of estimation variance. Simulation results conducted on synthetic data allow the performance of the proposed methods to be evaluated. They are compared to a recent technique based on the amplitude fluctuations of the power spectral density associated with the received communication signal. The estimation methods are shown to be robust to channel impairments (including white Gaussian noise and synchronization errors). The proposed strategies are finally tested on real signals with known ground truth showing their possible application to digital communication problems.

L'augmentation continue de la demande en bande passante pousse les opérateurs à déployer toujours plus d'antennes, et les force à une réutilisation plus agressive des ressources spectrales. Allouer ces ressources aux utilisateurs devient alors une opération délicate, où les interférences jouent un rôle central. Sur le lien montant, le problème est d'autant plus difficile que le niveau d'interférence est fortement lié aux utilisateurs à qui les ressources sont allouées. Cet article traite de l'affectation des ressources (spectrales et temporelles) pour les satellites multi-faisceaux. Cette thématique a été largement étudiée dans le contexte des réseaux cellulaires terrestres, le contexte satellitaire s'en distingue notamment par sa méthode d'accès, ce qui implique des modifications dans le modèle et dans sa méthode de résolution. Une modélisation spécifique du problème est alors présentée, sous la forme d'un problème d'optimisation linéaire en nombres entiers, cherchant à maximiser l'efficacité spectrale du système. Puis l'impact de simplifications exploitant la structure du problème est étudié, permettant de calculer une borne supérieure pour des scénarios réalistes.

High throughput satellites have proven to be an excellent solution to provide Internet services to white spots or to complement other existing infrastructures. With the use of multi-beam antennas, the same frequency may be reused dozens of times across a single satellite coverage area, increasing the system capacity and profitability. Legacy frequency reuse patterns such as uncoordinated 4-color scheme ensure interference isolation at the expense of important capacity reduction, using only one fourth of the operator's share in the scarce Ka band. Thus, to increase the per-beam available bandwidth, it is necessary to look for more aggressive and efficient Frequency Reuse schemes, generating higher Co-Channel Interference which has to be analyzed and handled. In this paper, we focus on the DVB-RCS2 return link of a multi-beam satellite and investigate the possibility of reaching the upper bound of a coordinated 2-color system capacity through the use of Interference-aware User Scheduling techniques. We first formalize the problem as an Integer Linear Program and study the impact of greedy simplifications on the optimality and processing times of our optimization models.

Considered as the free accessible and suitable solution for positioning in urban areas, Global Navigation Satellite Systems (GNSS) have been widely used these recent years in a wide spectrum of applications. However, signal blockage, non-line-of-sight (NLOS) multipath interferences and signal degradation affect the system performance and represent the major hurdles of GNSS in it course of adoption as a main localization technology in urban environments. Many approaches have been employed to constructively use these degraded signals in order to reduce positioning errors. Following this vision, we propose in this paper a joint estimation method of the position and the bias for measurement correction. This formulation leads to an ill-conditioned estimation problem. In this work, we apply a regularized robust estimation framework to this problem of NLOS mitigation for GNSS positioning in harsh areas. We derive the optimal regularization matrix by minimizing the total Mean Square Errors (MSE) of the considered model. The performance of the proposed method is assessed using real GNSS data collected in a dense urban area in Toulouse City, showing improvements in comparison to some existing methods.

Le procédé de positionnement comprend l'estimation d'un ensemble de biais multitrajets sur la base d'un modèle théorique des écarts entre les pseudo-distances mesurées et les pseudo-distances estimées. Le modèle comprend un terme de géométrie dépendant de la position du récepteur GNSS et des émetteurs GNSS et un terme additif représentant l'ensemble desdits biais. Les inconnues du modèle comprennent la position courante du récepteur GNSS et lesdits biais. L'estimation des biais repose sur une minimisation des résidus entre les écarts et le modèle théorique, en fonction des inconnues, sous la contrainte que l'ensemble des biais doit être parcimonieux. Les pseudo-distances mesurées sont corrigées sur base des biais estimés et une position courante du récepteur GNSS est prédite sur la base des pseudo-distances mesurées ainsi corrigées. L'invention permet de réduire l'impact des multi-trajets sur la solution de positionnement et donc d'en améliorer l'exactitude.