Enhancing Positioning Accuracy Through RSS Based Ranging And Weighted Least Square Approximation

International audienceIn this paper, localization based on Received Signal Strength (RSS) is investigated assuming a path loss log normal shadowing model. RSS-based estimation schemes of ranges are investigated; three different schemes are studied: Mean, median and mode. Estimation of position is performed using weighted least square approximation. We show that the positioning accuracy depends on the used estimator of ranges from RSS observables. We suggest that typical median estimator must be replaced by maximum likelihood estimator (mode) to enhance the positioning accuracy. Monte Carlo simulations show that the estimation scheme based on the mode estimator performs better than those based on the median or the mean estimator; and that the use of Weighted Least square approximation enhances the accuracy comparing to typical unweighted least square approximation

Hybrid Data Fusion Techniques for Localization in UWB Networks

International audienceIn this paper, we exploit the concept of data fusion in UWB (Ultra Wide Band) localization systems by using different location-dependent observables. We combine ToA (Time of Arrival) and RSS (Received Signal Strength) in order to get accurate positioning algorithms.We assume that RSS observables are usually available and we study the effect of adding ToA observables on the positioning accuracy. The proposed architecture of Hybrid Data Fusion (HDF) is based on two stages: Ranging using RSS and ToA; and Estimation of position by the fusion of estimated ranges. In the first stage, we propose a new estimator of ranges from RSS observables assuming a path loss model. In the second stage, a new ML estimator is developed to merge different ranges with different variances. In order to evaluate these algorithms, simulations are carried out in a generic indoor environment and Cramer Rao Lower Bounds (CRLB) are investigated. Those algorithms show enhanced positioning results at reasonable noise levels

Le tolérancement inertiel, une autre façon d'intégrer l'aspect combinatoire dans les processus assemblés

International audienceNous proposons dans cette communication de remplacer la façon traditionnelle de tolérancer les caractéristiques mécaniques (Bipoint [min - Max]) par une nouvelle façon totalement originale : le tolérancement inertiel. Le principe consiste à tolérancer l'inertie des écarts par rapport à la cible. En tolérancement inertiel l'écart maximal par rapport à la cible n'est pas figé, il dépend du nombre de pièces que l'on réalise Cette nouvelle façon de tolérancer offre de très nombreux avantages sur le tolérancement classique, notamment dans les cas de mélanges de lots, de tolérancement de produits assemblés, de définition de la conformité... Couplé avec le nouvel indicateur de capabilité Cpi, ce tolérancement permet de réaliser le meilleur compromis entre la qualité des produits assemblés et le coût de production

A Maximum Likelihood TOA Based Estimator For Localization in Heterogeneous Networks

International audienceIn this paper, we exploit the concept of data fusion in hybrid localization systems by combining different TOA (Time of Arrival) observables coming from different RATs (Radio Access Technology) and characterized by different precisions in order to enhance the positioning accuracy. A new Maximum Likelihood estimator is developed to fuse different measured ranges with different variances. In order to evaluate this estimator, Monte Carlo simulations are carried out in a generic environment and Cramer Rao Lower Bounds (CRLB) are investigated. This algorithm shows enhanced positioning accuracy at reasonable noise levels comparing to the typical Weighted Least Square estimator. The CRLB reveals that the choice of the number, and the configuration of Anchor nodes, and the type of RAT may enhance positioning accuracy

Enhancing positioning accuracy through direct position estimators based on hybrid RSS data fusion

International audienceIn this paper, localization based on Received Signal Strength (RSS) is investigated assuming a path loss log normal shadowing model. On the one hand, indirect RSS-based estimation schemes are investigated; these schemes are based on two steps of estimation: estimation of ranges from RSS and then estimation of position using weighted least square approximation. We show that the performances of this type of schemes depend on the used estimator in the first step.We suggest that typical median estimator must be replaced by maximum likelihood estimator (mode) to enhance the positioning accuracy. On the other hand, a new direct RSS-based estimation scheme of position is proposed; Monte Carlo simulations show that the new estimator performs better than indirect estimators and can be reliable in future hybrid localization systems

Collocated Microstrip Antennas for MIMO Systems with a Low Mutual Coupling Using Mode Confinement

WOSInternational audienceIn this paper, collocated antennas for MIMO systems are presented. The structure is composed of a dual-polarized microstrip square patch combined to a dual-polarized microstrip square ring. Consequently, four different radiation patterns are available simultaneously. With a length of about one guided wavelength, the proposed structure is well suited to reduce the MIMO terminal size. The structure operates in the 5.25 GHz band and exhibits a mutual coupling between the four input ports less than -23.5 dB in simulation and -20 dB in measurement. MIMO channel capacity measurements have been performed and demonstrate that the proposed antenna system can replace a classical system based on space diversity

Common synaptic input, synergies and size principle: Control of spinal motor neurons for movement generation

Understanding how movement is controlled by the CNS remains a major challenge, with ongoing debate about basic features underlying this control. In current established views, the concepts of motor neuron recruitment order, common synaptic input to motor neurons and muscle synergies are usually addressed separately and therefore seen as independent features of motor control. In this review, we analyse the body of literature in a broader perspective and we identify a unified approach to explain apparently divergent observations at different scales of motor control. Specifically, we propose a new conceptual framework of the neural control of movement, which merges the concept of common input to motor neurons and modular control, together with the constraints imposed by recruitment order. This framework is based on the following assumptions: (1) motor neurons are grouped into functional groups (clusters) based on the common inputs they receive; (2) clusters may significantly differ from the classical definition of motor neuron pools, such that they may span across muscles and/or involve only a portion of a muscle; (3) clusters represent functional modules used by the CNS to reduce the dimensionality of the control; and (4) selective volitional control of single motor neurons within a cluster receiving common inputs cannot be achieved. Here, we discuss this framework and its underlying theoretical and experimental evidence

Antennes co-localisées reconfigurables en fréquence pour systèmes MIMO

National audienceCe papier présente trois antennes co-localisées dont les accès présentent un découplage de l'ordre de 30dB en simulation. La diversité entre chaque antenne est assurée par une combinaison de diversité de polarisation et de rayonnement. Le dispositif a été dimensionné pour fonctionner autour de 5.25GHz avec une largeur de bande d'environ 9.8%. Toutefois, afin de répondre aux besoins actuels concernant la multiplication de fonctions au sein d'un même dispositif, une agilité en fréquence a été introduite via l'utilisation de courts-circuits étendant ainsi la bande à 33%, de 5GHz à 7GHz. La faisabilité pratique d'une telle antenne et la fiabilité des choix des différents paramètres de simulation ont été démontrés précédemment dans le cas d'une antenne cube du même type excitée par un seul monopôle

Pattern Reconfigurable Cubic Antenna

International audienceA new single-feed reconfigurable antenna for pattern diversity is presented in this paper. The proposed structure is based on a metallic cubic cavity which radiates through rectangular slots. The pattern reconfiguration is achieved with PIN diode switches by short-circuiting slots in their center. The designed antenna can switch between three different radiation patterns which radiate in a 4π steradian range and can receive any incident field polarizations. A prototype of the antenna, including PIN diodes and operating in the 5 GHz band, has been built to demonstrate the feasibility of the concept. Measurements have been conducted and three-dimensional radiation patterns are provided. Diversity performances are evaluated by calculating the envelope correlation coefficient

Investigation on Cavity/Slot Antennas for Diversity and MIMO systems: the example of a three-port antenna

International audienceThe use, as diversity antennas, of electromagnetic cavities with radiated slots etched on their faces is discussed. From this kind of geometries, many antenna configurations can be designed in order to provide uncorrelated signals. As an example, a three-port antenna which combines polarization and radiation pattern diversities is presented. The structure operates in the 5 GHz band and exhibits a coupling between input ports less than -30 dB in measurement. Envelope correlations between radiation patterns of each port are less than 0.035 which makes this structure well-suited for antenna diversity systems