Exploiting Traffic Balancing and Multicast Efficiency in Distributed Video-on-Demand Architectures

Distributed Video-on-Demand (DVoD) systems are proposed as a solution to the limited streaming capacity and null scalability of centralized systems. In a previous work, we proposed a fully distributed large-scale VoD architecture, called Double P-Tree, which has shown itself to be a good approach to the design of flexible and scalable DVoD systems. In this paper, we present relevant design aspects related to video mapping and traffic balancing in order to improve Double P-Tree architecture performance. Our simulation results demonstrate that these techniques yield a more efficient system and considerably increase its streaming capacity. The results also show the crucial importance of topology connectivity in improving multicasting performance in DVoD systems. Finally, a comparison among several DVoD architectures was performed using simulation, and the results show that the Double P-Tree architecture incorporating mapping and load balancing policies outperforms similar DVoD architectures.This work was supported by the MCyT-Spain under contract TIC 2001-2592 and partially supported by the Generalitat de Catalunya- Grup de Recerca Consolidat 2001SGR-00218

Diseño e implementación de un Sistema Interactivo de Video bajo Demanda

El proyecto que presentamos muestra el diseño e implementación de un sistema interactivo de vídeo bajo demanda, que nos servirá como base en el desarrollo de modelos válidos que nos permitan representar sistemas multimedia, a efectos de definir un entorno donde mediante técnicas de simulación avanzadas, podamos analizar y diseñar este tipo de sistemas. Es usual, al afrontar el diseño de este tipo de sistemas, orientar los esfuerzos únicamente, en una de las múltiples áreas que implican su resolución; nuestro objetivo integra el estudio del sistema en su conjunto: el software de sistema, la red de interconexión, el servidor de almacenamiento, servidor de procesamiento y el diseño/desarrollo del cliente. A partir de un subconjunto de las especificaciones que debe cumplir el sistema, construiremos una primera plataforma de pruebas e iremos diseñando y sintonizando los modelos en paralelo. La construcción de prototipos, monitorización y simulación, serán las herramientas que nos permitirán afrontar con garantías el proyecto que pretendemos asumirÁrea: Procesamiento de Imágenes - Tratamiento de Señales - Computación Gráfica - VisualizaciónRed de Universidades con Carreras en Informática (RedUNCI

Individual-oriented Model Crowd Evacuations Distributed Simulation

AbstractEmergency plan preparation is an important problem in building design to evacuate people as fast as possible. Simulation exercises as fire drills are not a realistic situation to understand people behaviour. In the case of crowd evacuations the complexity and uncertainty of the systems increases. Computer simulation allows us to run crowd dynamics models and extract information from emergency situations. Several models solve the emergency evacuation problem. Individual oriented modelling allows to give behaviour rules to the individual and simulate interactions between them. Due to variation on the emergency situations results have to be statistically reliable. This reliability increases the computing demand. Distributed and parallel paradigms solve the performance problem. In the present work we present a crowd evacuations distributed simulator. We implemented two versions of the model. One using Netlogo and another using C with MPI. We chose a real environment to test the simulator: pavilion 2 of Fira de Barcelona building, able to hold thousands of persons. The distributed simulator was tested with 62,820 runs in a distributed environment with 15,000 individuals. In this work we show how the distributed simulator has a linear speedup and scales efficiently

Ampliació de xarxes de computadors, febrer 2008

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Effects of atmospheric nickel on LH blood levels

Introduction: The nickel (Ni) present in urban air pollutant interferes with the functioning of the endocrine system altering the production the release, the transport the metabolism and the mechanism of activity. The purpose of the study is to verify whether occupational exposure to low of nickel (Ni) present in urban air may affect the LH values in outdoor workers performing different tasks of a large Italian city. Materials and methods: 164 subjects of both sexes were included in the study. We assessed the dosage of urinary nickel LH blood. We used statistical methods for description for comparison between medium (T test, Mann- Whitney U test and ANOVA) and for correlation (Pearson test and Multiple Linear Regression). Results: Urinary nickel is associated with female sex for all the statistical test adopted. Discussion: It can be assumed that occupational exposure to low doses of nickel present in pollution affects urban LH levels in female outdoor workers exposed