Estimation of cardiac and respiratory rhythms based on an AMFM demodulation and an adaptive eigenvector decomposition

International audienceIn a goal of sleep researches, we need to estimate cardiac and respiratory rhythms on 20-second epochs of a signal giving the variations in radial arterial pressure. This signal is amplitude and frequency modulated by cardiac and respiratory contributions. The technique we developped combines an amplitude and frequency (AMFM) demodulation using Teager energy operator and an adaptive eigenvector decomposition. The interest of the method lies in its independence from artefacts obtained for reasonable calculation and memory costs. Results indicate a close correspondence between estimations and reference values both for cardiac and respiratory estimations (mean error of 4% for both and standard deviation of 7% for cardiac and 14% for respiration rhythm)

A Block-Parallel Architecture for Initial and Fine Synchronization in OFDM Systems

International audienceA novel low complexity parallel algorithm and its associated architecture are proposed for initial synchronization in orthogonal frequency division multiplexing (OFDM) systems. The method is hierarchical and uses auto-correlation for the first step and cross-correlation for the second step. The main advantage of the proposed approach is that it reduces the computational complexity by a factor of five (80%), while achieving similar mean square error (MSE) as cross-correlation based methods. The method uses block-level parallelism for auto-correlation step, which speeds up the computation significantly. After fixed-point analysis, a parallel architecture is proposed to accelerate both coarse and fine synchronization steps. This parallel architecture is scalable and provides speed-up proportional to number of parallel blocks

Extraction des rythmes cardiaque et respiratoire par démodulation AMFM

Nous décrivons dans cet article une application d'un bracelet multicapteur, développé par l'ENSSAT, et qui intègre un capteur fournissant les variations de pression de l'artère radiale. Ce signal, sur lequel sont lisibles les battements cardiaques, est modulé en amplitude et en fréquence par la respiration. On opère sur celui-ci une démodulation AMFM en utilisant l'opérateur de Teager afin d'en extraire les rythmes cardiaque et respiratoire. Cependant, l'utilisation de l'opérateur de Teager est conditionnée à la satisfaction de conditions théoriques, qui ne sont pas remplies par le signal de pression artérielle. C'est pourquoi nous avons, dans un premier temps, étudié le comportement de la méthode d'extraction des paramètres afin de nous assurer de sa pertinence au delà du cadre défini par la théorie. Les premiers résultats montrent une erreur relative d'estimation de l'ordre de 1% sur les rythmes cardiaque et respiratoire

Speech enhancement using harmonic regeneration

International audienceThis paper addresses the problem of single microphone speech enhancement in noisy environments. Common short-time noise reduction techniques introduce harmonic distortion in enhanced speech because of the non reliability of estimators for small signal-to-noise ratios. We propose a new method called Harmonic Regeneration Noise Reduction technique which solves this problem. A fully harmonic signal is calculated based on the distorted signal using a non-linearity to regenerate harmonics in an efficient way. This artificial signal is then used to compute a suppression gain able to preserve the speech harmonics. This method is theoretically analyzed, then objective and formal subjective results are given and show a significant improvement compared to classical noise reduction techniques

Experimental Demonstration of Real Time Receiver for FDMA PON

International audienceFDMA PON provides high aggregate capacity (20-40Gbps) without requiring the user modules to operate at such high data rate. In this paper, we present for the first time a real time implementation of a FDM receiver in FPGA 1Gbitps in transceiver modules for an ONU and OLT

A CENTRALIZED ACOUSTIC ECHO CANCELLER BASED ON PERCEPTUAL PROPERTIES

International audienceThe use of a centralized acoustic echo canceller in the mobile switching center of a GSM network allows the operator to enhance the audio quality before transmission to all subscribers. However, the main problem is the impact of the speech coder/decoder nonlinearities along the echo path. In this paper, we propose a combined acoustic echo canceller/post-filter based on perceptual properties to reduce the coding noise. Theoretical and experimental comparisons against classical solutions are given to evaluate the performance of the proposed approach in a centralized context of echo cancellation

Intérêt de la prise en compte de propriétés auditives en annulation d'écho et débruitage

La communication avec un système "mains-libres" peut être considérablement altérée par le phénomène de l'écho acoustique et par le bruit ambiant. Aussi des traitements d'annulation d'écho et de débruitage s'avèrent indispensables pour assurer une communication de bonne qualité. Nous présentons une méthode de réduction de ces différentes perturbations à base de filtrage optimal, pouvant remplacer avantageusement les techniques classiques. L'introduction de propriétés auditives - s'appuyant sur un modèle de masquage hybride - dans le principe de filtrage permet de limiter les distorsions générées par celui-ci. Les résultats des simulations démontrent la pertinence de cette démarche, tout particulièrement pour le cas où la perturbation est un signal de parole

Evaluation de la précision des algorithmes de projection affine en virgule fixe

Le but de ce papier est de déterminer de manière analytique la puissance du bruit généré par une implémentation virgule fixe des Algorithmes de Projection Affine (APA). Ces algorithmes ont été développés dans les années 80 mais aucune étude de ce type n'a encore été menée. Dans cet article, nous définissons une expression analytique de la puissance du bruit puis celle-ci est appliquée à l'algorithme NLMS-OCF, un type d'Algorithme de Projection Affine. La validité du modèle est ensuite vérifiée par des simulations

IQ Imbalance Compensation Based on Maximum SNR Estimation in Coherent QPSK Systems

International audienceWe present a simple alternative method for the compensation of quadrature imbalance in optical quadrature phase-shift-keying (QPSK) coherent systems. The method is based on the determination and the compensation of the phase mismatch by the introduction of a relevant signal-to-noise ratio metric. The principle is validated numerically and the algorithm is validated experimentally through bit-error-rate (BER) and error vector magnitude (EVM) measurements. A 20 Gb/s optical QPSK experiment reveals a good agreement of theproposed method with the Gram-Schmidt orthogonalization procedure (GSOP). Moreover, the robustness of both methods was verified with up to 30° phase misalignment by comparing the signal after phase imbalance compensation to that without compensation. A 10% reduction of EVM is achieved with our method for a high phase misalignment of 30°

Noise Probability Density Function in Fixed-Point Systems based on smooth operators

International audienceTo satisfy cost constraints, application implementation in embed- ded systems requires fixed point arithmetic. Thus, the application defined in floating point arithmetic must be converted into a fixed- point specification. This conversion requires accuracy evaluation to ensure algorithm integrity. Indeed, fixed-point arithmetic generates quantization noises due to the elimination of some bits during a cast operation. These noises propagate through the system and degrade computing accuracy. In this paper, a method based on Generalized Gaussian PDF is presented to model and generate the output noise of the system. The accuracy of the proposed model is evaluated through different experiments