Bernadette Costa

Discrete Event Modeling and Simulation of Wireless Sensor Network Performance

The wireless distributed microsensor networks have profited from recent technological advances and it seems essential to precisely understand these systems. Modeling and simulation appear to be an essential aspect of predicting the Wireless Sensor Network (WSN) specific behavior under different conditions. We want to provide a new method of modeling, simulation and visualization of WSN using a discrete-event approach. Described by Zeigler in the 1970s, the Discrete Event System Specification is ideal for describing the asynchronous nature of the events occuring in WSN. We have provided a basic model for the analysis of WSN performance, including routing management, energy consumption and relative CPU activity. Our approach uses a detailed definition of node-oriented components and aims to introduce methods of visualizing the network at a different level of abstraction.

Wildfire impact on deterministic deployment of a Wireless Sensor Network by a discrete event simulation

Detecting and providing evolution informations of the wildfire can be a challenge for Wireless Sensor Networks. The network performance is directly related to the placement of the sensors within the field of interest. In this paper, we address the problem of wireless sensor deployment, for the purpose of following wildfire phenomenon. Based on a discrete event simulation using DEVS formalism, we show that the complexity of the fire position estimation is dependant of network deployement. We test four strategies of deployement and we show the limit of deterministic deployment in simple wildfire scenario.

DEVS-WSN : A discrete event approach for Wireless Sensor Network simulation

Zeigler in the 70 s introduced Discrete Event system Specification (DEVS) formalism. This formalism is able to describe the asynchronous nature of the events occuring in Wireless Sensor Network (WSN). In this paper we introduce a DEVS application oriented components for WSN : DEVS- WSN. Based on pyDEVS, it wants to provide a simulation tool based on a discrete event approach. Our model uses a detained definition of all node components and is independent of operating system. DEVS-WSN provides a framework to build quickly and easily a complex Wireless Sensor Network and to analyze several parameters at various levels of abstraction : hardware components, node, network.

Diffraction of ultrasonic waves from elastic Galois gratings

A significant attenuation of the specular echo in a wide frequency domain occurs in scattering of waves by Galois gratings.Diffraction of ultrasonicwaves by immersed one‐dimensional elasticgratings constructed from the finite Galois fields GF(p m ) is investigated. We develop a theoretical model taking into account the elasticity of the structure, its finite thickness, the boundary conditions at the fluid–solid and solid–fluid interfaces, and the periodicity of the gratings. In addition to the typical attenuation of the specular echo predicted by discrete Fourier transform, such a model predicts minima in the spectrum of the reflection coefficient corresponding to the excitation of surface waves (generalized Rayleigh and Scholte–Stoneley waves) by mode conversion and to the excitation of Lamb‐type modes. The attenuation as well as the minima are experimentally observed and these results are in good agreement with theoretically predicted ones. Galois gratings could constitute an advance in the search for new anechoic devices.

Scattering by immersed two‐dimensional elastic galois gratings

Diffraction of ultrasonic waves by immersed elastic bigratings constructed from the Galois fields GF(23) along one direction and GF(32) along the orthogonal one is studied. Such bigratings permit a significant attenuation of the specular echo in a wide frequency domain. This attenuation is experimentally observed and agrees with the theoretical one predicted by a model which takes into account the elasticity of the structure, the boundary conditions at the fluid–solid interface, and the periodicities of the gratings. Furthermore, numerous sharp minima in the spectrum of the reflection coefficient are experimentally observed and theoretically predicted; they correspond to the excitation of surface waves (generalized Rayleigh and Scholte–Stoneley waves) and they contribute significantly to the attenuation of the specular echo.