DVB-T2 network optimization with swimulated annealing

Postprint (author’s final draft

Metaheuristic proposal to minimize self-interference in single frequency networks

Postprint (published version

Escritorios remotos en máquinas virtuales aplicados en grandes corporaciones

Postprint (published version

MCU basada en SIP para videoconferencias seguras

Los sistemas actuales de videoconferencia IP presentan diferentes problemáticas que entorpecen la comunicación a través de ellos. La mayoría están basados en implementaciones propietarias y conllevan costes elevados de adquisición de los equipos. Además, la calidad de los recursos multimedia transferidos por estos sistemas acostumbra a ser bastante baja, cosa que afecta a la experiencia del usuario y a la percepción de presencia. Finalmente, la mayoría de las soluciones comerciales no incluyen la opción de asegurar las videoconferencias. En este artículo se presenta una solución implementada basada en un servidor de videoconferencias en software de código abierto. Una capa de señalización basada en el protocolo SIP y un plano multimedia, basado en un replicador de paquetes RTP. Esta solución constituye una plataforma que permite disminuir los costes del sistema usando ordenadores personales con clientes SIP en software, permitiendo reducir drásticamente el coste de los equipos. Finalmente, se propone un mecanismo de protección de los flujos multimedia usando Secure Real-time Transport Protocol (SRTP) y Multimedia Internet Keying (MIKEY) para el intercambio de claves.Postprint (published version

Wavelet analysis of long-range dependent traffic

Network traffic exhibits fractal characteristics such as self-similarity and long-range dependence. Several estimators of fractal parameters have been developed, but few consider the possibility of tracking the time evolution of those parameters. Some fractal-aware network algorithms such as effective bandwidth estimation, admission control or traffic prediction could improve their performance if an accurate description of the time evolution of traffic fractality were developed. The aim of the present dissertation is to study the temporal evolution of fractal traffic parameters via a wavelet-based analysis. In particular, three different wavelet transforms are presented: Discrete Wavelet Transform (DWT), Wavelet Packet Transform (WPT) and Stationary Wavelet Transform (SWT). The dynamic estimation of the fractal parameters of a locally monofractal process is strongly dependent on the choice of the variance change points algorithm to be applied to the wavelet coefficients series. Namely, we discuss the following two procedures: Iterated Cumulative Sum of Squares (ICSS) and Schwarz Information Criterion (SIC)

Fibre orientation and stiffness prediction in short fibre-reinforced thermoplastics

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN011567 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Towards an Improved Characterization of Fractal Network Traffic ∗

Network traffic exhibits fractal characteristics such as self-similarity and long-range dependence. Several estimators of the fractal parameters have been developed, but few consider the possibility of tracking the time evolution of those parameters. Some fractal-aware network-related algorithms such as effective bandwidth estimation, control admission or traffic prediction could improve their performance if an accurate description of the time evolution of traffic fractality were developed. The Discrete Wavelet Transform (DWT) is a powerful tool capable of performing a multiresolution analysis of a time series. The Abry-Veitch estimator (based on a graphic tool called LogScale Diagram) is an accurate and efficient DWT-based estimator of the fractal parameters, but it lacks adaptability to possible changes in the aforementioned parameters. In order to detect the changes, we combine the DWT and its non-orthogonal version, the Stationary Wavelet Transform (SWT) with the Schwarz Information Criterion (SIC), a variance change points detection algorithm founded on information theory concepts. Both DWT-SIC and SWT-SIC algorithms, together with a first implementation of a “real-time ” estimator, were described in previous works. This paper describes the last refinements added to our algorithms: 1) an automatic clustering procedur