Growth of elderly population induces the increasing demands for high-quality healthcare services, wireless body area networks (WBANs) has emerged as a promising solution for monitoring of patients vital life signs parameters. Reliability and extending the lifetime are considered amongst the important and challenging issues in WBANs. The standard IEEE 802.15.4 is considered as the most used MAC protocol for medical sensor body area networks, owing to its low-power, low data rate and low-cost features. In this paper, we propose an enhancement optimized MAC protocol based on IEEE 802.15.4 dubbed EOMAC. The proposed protocol aims to enhance the reliability and to prolong the lifetime of the network, by reducing energy consumption.
Ce travail de these est consacre a la mise en place et a la validation d’un banc metrologique permettant d’etudier le comportement des stimulateurs cardiaques exposes a des perturbations electromagnetiques de basses frequences. Nous avons commence par une presentation detaillee de la problematique generale des interactions entre les champs electromagnetiques et les stimulateurs cardiaques. La methode que nous avons developpee comporte deux phases principales correspondant aux essais en perturbations conduites et aux essais en perturbations rayonnees dans l’air et in vitro. Les frequences etudiees sont 50/60 Hz et 10/25 KHz. Les essais experimentaux ont ete effectues sur plusieurs stimulateurs mono chambres et double chambres. Les resultats montrent un effet de fenetrage des circuits de detection des stimulateurs pour les quatre frequences etudiees. La modelisation du banc de mesure necessite d’etudier les effets des courants induits generes par l’application d’un champ magnetique. Des calculs analytiques et des simulations numeriques ont ete effectues. Nous avons modelise les interactions du champ magnetique avec une representation simplifiee du stimulateur cardiaque implante dans le milieu. La comparaison des resultats dans l’air et in vitro nous a permis d’etablir un modele electrique equivalent. Les resultats obtenus experimentalement et theoriquement ont permis de valider le banc de mesure. La methode appliquee est valable pour des autres implants medicaux tel que les defibrillateurs cardiaques, implants auditifs…etc.
In this paper, an indoor VLC system based on new LED array arrangement using 16 LEDs distributed in a 3-D space around the ceiling is presented. The proposed designs performance are investigated and compared with other different designs [8], [9] using the same number of LED arrays. Enhance received power, data rate and SNR across the room without increasing number of LEDs arrays is our purpose. To evaluate the system performance, the received power and SNR were calculated. While to analyze the impact of inter symbol interference the root mean square delay spread was calculated too. The results show that a significant improvement was observed in all the parameters for evaluating the performances of the proposed system, in particular (received power, SNR, RMS and data rate). The received power under our proposed models was increased from 2.1666 to 2.5804 dBm for model l, and 0.0592 to 0.7787 dBm for model 2. The SNR is increased from 73.987 to 74.5765 dB for model 1, and 69.8918 to 70.8576 dB for model 2 and the data rate is enhanced as well from 116.90 to 139.4031Mb/s for model 1, and from 125 to 167.7283 Mb/s for model 2.
Over the past decade, the evolution of embedded system has taken place drastically as it has been for their integration in various industries. This increases Electro-Magnetic Interferences (EMI) problems and generates new design constraints on Electro-Magnetic Compatibility (EMC). Thus, the nature of the electromagnetic environment and the prospective for undesired coupling must be taken into consideration by embedded systems engineers to avoid the equipment failure or malfunction. Accordingly, the radiated emission models are of great interest to designers of electronic equipment. This paper exploits the Plane Wave Spectrum (PWS) technique to predict and compute the magnetic field at various distances till 100mm above a Device Under Test (DUT). Good similarities are obtained between the magnetic field components calculated by PWS and the simulated ones by HFSS at different elevation from the electric dipole.
The classic learning environments are based on the "one size fits all" approach, that is to propose the same contents to all learners without considering their preferences and abilities. This work aims to develop a learning environment that provides personalized contents to learners. For this, a new association rule based recommendation approach (A_RS) is proposed and integrated into this environment. A_RS recommends learning materials taking into account learners' preferences, prior knowledge and memory capacity.
