Décodage des codes LDPC définis sur des groupes abéliens

Une large classe de codes LDPC est définie et qui comprend les codes LDPC définis sur les corps finis, les anneaux et les groupes mais aussi des codes non-linéaires. Cela est rendu possible en étendant la notion de parité du code. Un algorithme rapide de type propagation de croyance est développé pour ce type de parité. Des exemples montrent des utilisations possibles de tels codes

Spontaneous hot-electron light emission from electron-fed optical antennas

Nanoscale electronics and photonics are among the most promising research areas providing functional nano-components for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically-driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale

Probabilistic sensor data processing for robot localization on load-sensing floors

International audienceLoad-sensing floors are capable of tracking objects without suffering from occlusions nor posing the same privacy issues as cameras. They have been mostly used to analyze human gait as a way of continuous diagnosis but could also be placed alongside robots to help monitoring in specialized institutions, such as elderly care facilities. However, large-scale deployments necessitate cheap sensors which do not necessarily offer the same precision. With more noisy sensors, lighter robots might be difficult to track and precisely localize. In this article, we investigate various models in order to estimate the position of a robot. We experiment with several robots of different weights and compare the models' estimates against ground truth measurements provided by a motion capture system. We show that with standard-sized tiles of 60 cm, we can track even the lighter robots with less than 4 cm of error

Communication numérique sécurisée par synchronisation du chaos

é- Ce travail concerne les communications numériques sécurisées basées sur un principe de modulation par des signaux chaotiques. Le système de communication présenté ici repose sur un nouveau concept, l'emploi d'une rétroaction dans la chaîne de transmission. Il permet notamment d'élargir la classe de signaux chaotiques potentiels pour ce type d'applications sans alterer la vitesse de synchronisation du système

Laser-induced thermoelectric effects in electrically biased nanoscale constrictions

Electrically biased metal nanostructures are at the core of innovative multifunctional integrated devices that control the flow of electrons and photons at the nanoscale. They are based on plasmonic structures that create strongly confined fields, typically associated with large temperature gradients. These thermal effects may generate artifact responses detrimental to the desired operation. We show here how a biasing polarity and a local optical excitation asymmetry of a generic geometry – a nanoscale constriction – interplay thermally to modify the diffusive electron transport in out-of-equilibrium conditions. Our experimental results are accompanied with computational electromagnetism and multiphysics simulations

Novel insights into the diet of the Pyrenean desman (Galemys pyrenaicus) using next-generation sequencing molecular analyses

[Departement_IRSTEA]EauxInternational audienceThe Pyrenean desman, a threatened, semiaquatic mammal, is considered a specialist predator feeding on aquatic benthic invertebrates. This categorization comes from visual identification of prey in scat or gut contents, often based on a limited number of samples and locations. We combined diet analyses using next-generation sequencing methods with an extensive survey to explore the summer diet of Pyrenean desmans across the French Pyrenees. This study thus provides an unprecedented level of detail on the trophic ecology of Pyrenean desmans. Our results revealed a diverse diet containing a high proportion of rare prey and substantial consumption of terrestrial prey, which suggests a more generalist diet than previously understood. Three diet groups were identified, with significant differences in prey composition. These differences were not related to geographic location, but rather to local environmental variables. The spatial variation in diet was likely induced by local abiotic parameters that affect prey availability or use of foraging habitats

Turbo Decision Aided Receivers for Clipping Noise Mitigation in Coded OFDM

<p>Abstract</p> <p>Orthogonal frequency division multiplexing (OFDM) is the modulation technique used in most of the high-rate communication standards. However, OFDM signals exhibit high peak average to power ratio (PAPR) that makes them particularly sensitive to nonlinear distortions caused by high-power amplifiers. Hence, the amplifier needs to operate at large output backoff, thereby decreasing the average efficiency of the transmitter. One way to reduce PAPR consists in clipping the amplitude of the OFDM signal introducing an additional noise that degrades the overall system performance. In that case, the receiver needs to set up an algorithm that compensates this clipping noise. In this paper, we propose three new iterative receivers with growing complexity and performance that operate at severe clipping: the first and simplest receiver uses a Viterbi algorithm as channel decoder whereas the other two implement a <it>soft-input soft-output</it> (SISO) decoder. Each soft receiver is analyzed through EXIT charts for different mappings. Finally, the performances of the receivers are simulated on both short time-varying channel and AWGN channel.</p

Turbo Decision Aided Receivers for Clipping Noise Mitigation in Coded OFDM

Orthogonal frequency division multiplexing (OFDM) is the modulation technique used in most of the high-rate communication standards. However, OFDM signals exhibit high peak average to power ratio (PAPR) that makes them particularly sensitive to nonlinear distortions caused by high-power amplifiers. Hence, the amplifier needs to operate at large output backoff, thereby decreasing the average efficiency of the transmitter. One way to reduce PAPR consists in clipping the amplitude of the OFDM signal introducing an additional noise that degrades the overall system performance. In that case, the receiver needs to set up an algorithm that compensates this clipping noise. In this paper, we propose three new iterative receivers with growing complexity and performance that operate at severe clipping: the first and simplest receiver uses a Viterbi algorithm as channel decoder whereas the other two implement a soft-input soft-output (SISO) decoder. Each soft receiver is analyzed through EXIT charts for different mappings. Finally, the performances of the receivers are simulated on both short time-varying channel and AWGN channel