Search

The proposed UWB antenna covers mobile communications (GSM, EDG, UMTS(3G), LTE(4G)) and wireless networks (WIFI, WiMAX), within a theoretical bandwidth defined from 780MHz to 4.22GHz. The UWB antenna is designed and realized on a FR-4 substrate with an electrical permittivity of 4.4. It presents a 98.75% average analytical efficiency and an omnidirectional radiation within the previous bandwidth. The impedance excitation port is fixed at 50 Ohm according with the SMA impedance used in the practical part. The measured results are in good agreement with those obtained using CST and ADS softwares. The measured bandwidth, defined from 980MHz to 4.2GHz, presents an efficiency of 94.14%. Furthermore, the practical radiation diagram and the excitation port impedance stay the same as that the simulation one., Comment: 10 Pages, 13 Figures

The Substrate Integrated Waveguide (SIW) technology is a very promising technique with which we can take the advantages of both waveguides and planar transmission lines. Therefore, in [2.1-3] GHz band various microwave components and devices have been designed successfully using Ansoft HFSS software. We then proceeded to the realization of the coupler and then made measurements of the frequency response in the range [2.1-3] GHz using a network analyzer. Thus, results of this modeling are presented, discussed and allow to integrate these devices in planar circuits., arXiv admin note: substantial text overlap with arXiv:1404.2888 by other authors

International audience; The main challenge in the field of Wireless Sensor Networks (WSNs) is the energy conservation as long as possible. Clustering paradigm has proven its ability to prolong the network lifetime. The present paper proposes two algorithms using an approach that combines fuzzy c-means and ant colony optimization to form the clusters and manage the transmission of data in the network. First, fuzzy c-means is used to construct a predefined number of clusters. Second, we apply Ant Colony Optimization (ACO) algorithm to form a local shortest chain in each cluster. A leader node is randomly chosen at the beginning since all cluster nodes have the same amount of energy. In the next transmission, a remaining energy parameter is employed to select leader node. In the first algorithm, leader nodes transmit data in single hop to the distant base station (BS) while in the second the ACO algorithm is applied again to form a global chain between leader nodes and the BS. Simulation results show that the second proposed algorithm consumes less energy and effectively prolongs the network lifetime compared respectively with the first proposed and the LEACH algorithms.

International audience

Data aggregation in wireless sensor networks (WSNs) provides a great reduction of energy consumption. The limited resources of sensor nodes make the choice of an encryption algorithm very important for providing security for data aggregation. Asymmetric cryptography involves large ciphertexts and heavy computations but solves, on the other hand, the problem of key distribution of symmetric one. The latter provides smaller ciphertexts and speed computations. Also, the recent researches have shown that achieving the end-to-end confidentiality and the end-to-end integrity at the same is a challenging task. In this paper, we propose (SA-SPKC), a novel security protocol which addresses both security services for WSNs, and where only the base station can verify the individual data and identify the malicious node. Our scheme is based on stateful public key encryption (StPKE). The latter combines the best features of both kinds of encryption along with state in order to reduce the computation overhead. Our analysis shows the security and the efficiency of our scheme for WSNs.

International audience

International audience; Over the last decade, great efforts are invested in reducing emissions of greenhouse gases at a world scale. We should therefore elaborate new global solutions to this type of pollution, in which fleets of vehicles are heavily contributing. In this paper, we propose a novel green architecture for global fleet management that considers the most important actors. The proposed architecture allows to collect useful information from several fleets of vehicles and their environment, and provides real-time services to companies that own one of these fleets. One important service is the calculation of economic itinerary. We propose a new "green" calculation method that is based on an efficient and high precision fuel consumption estimation. Our method uses: (i) topological information such as the elevation variations, source and destination of the trip, (ii) weather conditions, (iii) vehicle's characteristics, and (iv) driver's behavior. We implemented a lightweight traffic management server that provides a real-time service allowing to find the most economic itinerary for vehicles belonging to the fleet. The utilization of such architecture and mechanisms associated with itinerary planning results in a highly green fleet management system.

Les systèmes de communications mobiles d'aujourd'hui exigent une qualité plus élevée de communication, des débits plus élevés, une opération de fréquence plus élevée, et plus de canaux par largeur de bande d'unité. Dans le domaine de télécommunication, les synthétiseurs de fréquences trouvent leurs applications dans de nombreux dispositifs, émetteur, récepteur. Le but essentiel de notre travail, consiste à analyser et à simmuler le bruit de phase d’un synthétiseur de fréquences pour les commmunications mobiles sur UMTS (Universal Mobile Telecommunication System) opérant dans la bande (1920-1980) MHz pour l’émission et la bande (2110-2170) MHz pour la réception. Sciences of Electronics,Technologie of Information and Telecommunication (2012).

Temperature dependence of the GaN-Dual-Gate MESFET (GaNDGMESFET)DC-characteristics is investigated using two dimensional numerical simulations. Differential equations derived from a Hydrodynamic electron transport model describe the physical proprieties of the device. Simulation results over a wide range of temperature from 300 K to 900 K performed on an industrial software Atlas from SILVACO are presented for a GaN-DGMESFET with a gate length of 0.5 μm. The results show a significant degradation of the DC characteristics. Variation of the electron temperature with the drain-source voltage (Vds) is studied and a large temperature is observed for Vds > 1 V. At low drain-source voltage (Vds < 1 V) the electron temperature is closed to the lattice temperature

Temperature dependence of the GaN-Dual-Gate MESFET (GaNDGMESFET) DC-characteristics is investigated using two dimensional numerical simulations. Differential equations derived from a Hydrodynamic electron transport model describe the physical proprieties of the device. Simulation results over a wide range of temperature from 300 K to 900 K performed on an industrial software Atlas from SILVACO are presented for a GaN-DGMESFET with a gate length of 0.5 µm. The results show a significant degradation of the DC characteristics. Variation of the electron temperature with the drain-source voltage (Vds) is studied and a large temperature is observed for Vds > 1 V. At low drain-source voltage (Vds < 1 V) the electron temperature is closed to the lattice temperature. IJCSI International Journal of Computer Science Issues, Vol. 9, Issue 1, No 3, January 2012.

Recently, band-pass photonic crystal filters have attracted great attention due to their important applications in the fields of optical interconnection network and ultrahigh speed information processing. In this paper we propose the design of a new type of photonic crystal band-pass resonant filters realized in onemissing- row waveguide by decreasing proper defects along the waveguide with broadband acceptable bandwidth. Two types of photonic crystal band-pass filters are utilized and optimized using the Two-dimensional finite-difference time-domain (FDTD) technique. The first one is based on the Fabry-Pérot cavities and in the second one a cavity is introduced in the middle by omitting two neighboring air holes in waveguide. Numerical results show that a band [1.47 μm-1.57 μm] around 1.55μm is transmitted with a maximum transmission of about 68% and as a result wide band-pass filters are designed.

International audience; Wireless sensor networks (WSN) grows in size and gain new applications in our lives ranging from military applications to civilian ones. However security in WSN was not carefully carried out, since only some symmetric encryption based protocols are proposed in literature, under the assumption that the nature of sensor nodes does not support public key encryption due to the limitation in battery and CPU power. However the new development of sensors technologies may allow more computational power and gives us the possibility to use public key encryption in WSN if the used algorithm is energy efficient such as ECC. Therefore in this paper we propose a lightweight implementation of Public Key Infrastructure (PKI). Our proposed protocol called ¹PKI uses public key encryption only for some speci¯c tasks as session key setup between the base station and sensors giving the network an acceptable threshold of confidentiality and authentication