Herramienta de optimización paramétrica distribuida con HFSS

Hoy en día, las señales de naturaleza electromagnética son la esencia de las actuales tecnologías de la información y de las comunicaciones. En particular, el auge de las redes de comunicación inalámbrica, ha elevado la demanda de diseño de estructuras electromagnéticas de gran complejidad. El análisis de estas estructuras es costoso en tiempo y en recursos computacionales, por lo que, realizar simulaciones paramétricas, que requieren realizar múltiples modificaciones sobre los parámetros de la estructura, eleva el conjunto de análisis y aumenta inevitablemente el tiempo de ejecución. El objeto del presente Proyecto Fin de Carrera es diseñar una metodología de simulación paramétrica distribuida que permita gestionar de forma eficiente los recursos computacionales que se disponen, minimizando así, dicho tiempo de ejecución. A esta metodología se le puede incluir, si es el caso, un optimizador que ayude al diseñador a encontrar la solución óptima. En este proyecto se propone un optimizador que hace uso de la simulación paramétrica para encontrar los valores de los parámetros que proporcionan la solución óptima. Se ha utilizado HFSS como simulador de problemas electromagnéticos, tanto para el modelado de las estructuras, como también para su análisis y obtención de resultados. El conjunto de análisis a realizar en el proceso de optimización es distribuido en el cluster del Grupo de Radiofrecuencia del departamento de Teoría de la Señal y Comunicaciones, gracias al sistema gestor de colas Sun Grid Engine (SGE). La herramienta ha sido validada con la optimización de un filtro de guiaonda con postes dieléctricos, en particular, de cuatro cavidades y cinco irises. Como puede intuirse, esta estructura cuenta con un elevado número de parámetros, lo que justifica una optimización con un uso eficiente de los recursos debido a la elevada necesidad de cómputo necesaria. ________________________________________________________________________________________________________________________Nowadays, electromagnetic natural signals are the essence of modern information technology and communications. Particularly, the growth of wireless communication networks has risen the demand of highly complex electromagnetism structures design. The analysis of these structures is costly in time and computational resources. Therefore, carrying out parametric simulations, which require making several modifications over the structure parameters, expands the analysis set and increases inevitably the execution time. The object of the following dissertation is to design a methodology of distributed parametric simulation that allows to efficiently manage the available computational resources, minimizing this way the execution time. To this methodology can be included, if needed, an optimizer which helps the designer to find the optimal solution. In this project it is proposed an optimizer using the parametric simulation to find the values of the parameters which give the optimal solution. HFSS has been used as the electromagnetic problem simulator, both for structure modelling and for analysis and obtaining of results. The set of analysis to make in the optimization process is distributed in the cluster from the Radio Frequency Group of the Signal Processing and Communication Theory Department, thanks to the Sun Grid Engine (SGE) queuing system. The tool has been validated with the optimization of a waveguide filter with dielectrics, particularly using four cavities and five iris. As can be seen, this structure includes a high number of parameters, which justifies an optimization that efficiently manages resources, due to the high computation capacity needed.Ingeniería de Telecomunicació

Analysis of the impact of FEC techniques on a multicast video streaming service over LTE

The proceeding at: European Conference on Networks and Communications (EuCNC 2015), took place in June 29/July 2, 2015, in Paris, France.In a multicast video streaming service the same multimedia content is sent to a mass audience using only one multicast stream. In multicast video streaming over a cellular network, due to the nature of the multicast communication, from a source to multiple recipients, and due to the characteristics of the radio channel, different for each receiver, transmission errors are addressed at the application level by using Forward Error Correction (FEC) techniques. However, in order to protect the communication over the radio channel, FEC techniques are also applied at the physical layer. Another important technique to improve the communication of the radio channel is the use of a single-frequency network. This paper analyzes the performance of a video streaming service over a cellular network taking into account the combined impact of different factors that affect the transmission, both the physical deployment of the service and the two levels of FEC.This work was supported in part by the Spanish Ministry of Economy and Competitiveness, National Plan for Scientific Research, Development and Technological Innovation (IN-NPACTO subprogram), LTExtreme project (IPT-2012-0525-430000).Publicad

A model to evaluate MBSFN and AL-FEC techniques in a multicast video streaming service

This procceding of: 10th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob). Took place 2014, October 08-10, in Lanarca (Chipre). The event Web site of http://conferences.computer.org/wimob2014/ .In a multicast video streaming service over a cellular network, the same content is sent to a mass audience using a common channel. However, users belonging to the same multicast channel perceive different characteristics of the radio channel. Moreover, in wireless environments, the radio interface introduces an important level of interference and noise, resulting in a high rate of transmission errors. Therefore, a protection of the information is needed at each receiver using Forward Error Correction (FEC) schemes, which allow the recovery of the lost packets sending redundancy together with the payload. FEC solutions can be used in combination with other techniques to overcome the existing limitations of the mobile network, in particular, the use of a single-frequency network to prevent the effect of destructive signal interference. This paper analyzes the performance of a video streaming service comparing different FEC schemes, Raptor and RaptorQ codes, where some system parameters can be tuned in a single-frecuency network.This work was supported in part by the Spanish Ministry of Economy and Competitiveness, National Plan for Scientific Research, Development and Technological Innovation (INNPACTO subprogram), LTExtreme project (IPT-2012-0525-430000).Publicad

Contribución al diseño de servicios multimedia en arquitecturas de red móvil basadas en funciones de red virtualizadas

La demanda de servicios multimedia en las redes móviles ha experimentado un gran crecimiento en los últimos años. Sin embargo, la retransmisión en directo de eventos sigue planteando diversos desafíos cuando estos servicios se soportan sobre las arquitecturas de red móvil tradicionales. Los organismos de estandarización han definido protocolos y mecanismos de streaming que dan soporte a los servicios multimedia en las redes móviles, pero el estado del arte muestra la necesidad de proponer soluciones orientadas a reducir el retardo de las retransmisiones en directo y garantizar la continuidad de la reproducción multimedia. En la tesis doctoral se abordan dos enfoques para diseñar los mecanismos de streaming. El primero, consiste en desplegar las soluciones de mejora en los dispositivos finales de la red, es decir, en los servidores y los dispositivos móviles. El segundo, consiste en adaptar la transmisión del streaming multimedia mediante la actuación de elementos intermedios de la red, como por ejemplo, servidores proxy. Los mecanismos de streaming propuestos usando estos enfoques se han evaluado mediante modelos analíticos y de simulación. El marco de las nuevas arquitecturas de red móvil, basadas en tecnologías de virtualización, proporciona una flexibilidad que facilita la adopción de los mecanismos propuestos. Las principales ventajas de estas nuevas arquitecturas se obtienen gracias a la combinación de soluciones basadas en la virtualización de las funciones de red y las redes definidas por software, aumentando la programabilidad de las redes y flexibilizando el despliegue de nuevos servicios. En la tesis doctoral se analiza la integración de los servicios de difusión de contenidos multimedia y las mejoras definidas en la tesis para los mecanismos de streaming en las nuevas arquitecturas de red móvil basadas en funciones de red virtualizadas. Las propuestas de integración realizadas, junto con los resultados obtenidos de la evaluación mediante modelos analíticos y de simulación de los mecanismos de streaming propuestos, muestran cómo es posible reducir la latencia del servicio garantizando la continuidad de la reproducción multimedia en las nuevas arquitecturas de red móvil. ----------ABSTRACT---------- The demand for multimedia services in mobile networks has been rapidly increasing over the past years, which has led to a significative Internet traffic growth. Broadcasting live events over current mobile network architectures can reduce bandwidth consumption but poses other challenges in terms of quality of service. Standardization bodies have defined protocols and streaming mechanisms giving support to multimedia broadcast services in mobile networks. However, the state of the art shows the need to propose solutions aimed at providing a seamless multimedia playback with a reduced service latency. This doctoral thesis addresses this problem by proposing new streaming mechanisms that can improve these key aspects of the service. Two different approaches are considered when designing the streaming mechanisms proposed in this thesis. The first one is based on implementing the new solutions in end devices such as servers and mobile devices. The second one is based on network assisted streaming using intermediate network nodes, such as proxy servers, to support the multimedia streaming adaptation. The streaming mechanisms proposed following these approaches have been evaluated by using analytical and simulation models. The upcoming mobile network architectures, based on virtualization technologies, provide the flexibility needed for adopting the proposed streaming mechanisms. The main advantages of these architectures rely on the combination of network function virtualization and softwaredefined networking, which increases the programmability of networks and facilitates the deployment of new services. In this doctoral thesis, we analyse how both multimedia broadcast services and the new streaming solutions previously proposed can be integrated with the new mobile network architectures based on virtual network functions. Our proposals for this integration, together with the results obtained from the evaluation of the streaming mechanisms using analytical and simulation models, show how it is possible to reduce service latency while providing a seamless playback in the context of the upcoming mobile network architectures

Unicast and multicast streaming services over LTE

The poster at: European Conference on Networks and Comunications. EUCNC 2014, took place in Bologna (Italy), in 23-26, June, 2014. The Event Web site in http://www.eucnc.eu/2014/www.eucnc.eu/index.htmlThis work was supported in part by the Spanish Ministry of Economy and Competitiveness, National Plan for Scientific Research, Development and Technological Innovation, LTExtreme project (IPT-2012-0525-430000)Publicad

Supporting handover between LTE video broadcasting and unicast streaming

The heterogeneity of the network poses new challenges on the paradigm of multimedia content distribution. Nowadays, different access technologies coexist in user terminals, so it is possible to improve the performance or avoid coverage problems by switching from one to another. This process is known as handover. In this work we have focused on vertical handover, which is the process of switching between different access technologies without losing connectivity. If a handover happens during a video streaming session, the session will need to adapt to the different channel conditions. This paper discusses the proposal of a new mechanism at the application level to support a handover between a unicast video streaming session and a video session based on LTE broadcasting

DASH Adaptation Algorithm Based on Adaptive Forgetting Factor Estimation

The wide adoption of multimedia service-capable mobile devices, the availability of better networks with higher bandwidths, and the availability of platforms offering digital content has led to an increasing popularity of multimedia streaming services. However, multimedia streaming services can be subject to different factors that affect the quality perceived by the users, such as service interruptions or quality oscillations due to changing network conditions, particularly in mobile networks. Dynamic Adaptive Streaming over HTTP (DASH), leverages the use of content-distribution networks and the capabilities of the multimedia devices to allow multimedia players to dynamically adapt the quality of the media streaming to the available bandwidth and the device characteristics. While many elements of DASH are standardized, the algorithms providing the dynamic adaptation of the streaming are not. The adaptation is often based on the estimation of the throughput or a buffer control mechanism. In this paper, we present a new throughput estimation adaptation algorithm based on a statistical method named Adaptive Forgetting Factor (AFF). Using this method, the adaptation logic is able to react appropriately to the different conditions of different types of networks. A set of experiments with different traffic profiles show that the proposed algorithm improves video quality performance in both wired and wireless environments

A virtualized platform for analyzing LTE broadcast services

Nowadays, users are demanding access to video content anytime and anywhere. LTE broadcast services and video streaming services can reduce the resources used by telecommunication companies to give access to video content and open up new business opportunities. In this context, testbeds and simulation tools can help in the analysis of the different parameters that need to be considered in the deployment of video services based on LTE. In this paper, we describe the design and implementation of an open-source virtualized platform that supports both LTE broadcast services and video streaming services. The testbed is being used both over real LTE networks and LTE network emulations to analyze the performance of video streaming services and to validate new proposals