[[alternative]]A Smart Guiding, Pre-Warning, and Monitoring Wireless Network System for the Blind(I)

計畫編號：NSC93-2745-E032-005-URD研究期間：200408~200507研究經費：822,000[[sponsorship]]行政院國家科學委員

Fly-By-Wireless for Next Generation Aircraft: Challenges and Potential solutions

”Fly-By-Wireless” paradigm based on wireless connectivity in aircraft has the potential to improve efficiency and flexibility, while reducing weight, fuel consumption and maintenance costs. In this paper, first, the opportunities and challenges for wireless technologies in safety-critical avionics context are discussed. Then, the assessment of such technologies versus avionics requirements is provided in order to select the most appropriate one for a wireless aircraft application. As a result, the design of a Wireless Avionics Network based on Ultra WideBand technology is investigated, considering the issues of determinism, reliability and security

An experimental analysis of the effects of noise on Wi-Fi video streaming

Wireless networks such as WiFi suffer communication performance issues in addition to those seen on wired networks due to the characteristics of the radio communication channel used by their Physical Layers (PHY). Understanding these issues is a complex but necessary task given the importance of wireless networks for the transfer of wide ranging packet steams including video as well as traditional data. Simulators are not accurate enough to allow all the intricacies of such communication to be accurately understood, especially when complex interactions between the protocols of different layers occurs. The paper suggests cross layer measurement as a solution to the problem of understanding and analysis of such complex communication issues and proposes a framework in which appropriate performance measurements can be made from a WiFi network supporting a video streaming application. The framework has been used to collect these measurements at the PHY, MAC, Transport and Application layers. Analysis of the collected measurements has allowed the effects of noise interference at the PHY to be related to the perceived performance at the Application Layer for a video streaming application. This has allowed the effect of the SNR on the download time of a video sequence to be studied

Análisis comparativo de prestaciones de tráfico de video multicast en redes heterogéneas

Durante los últimos años, se ha visto un aumento exponencial en el crecimiento en aplicaciones multimediales, y en particular en aplicaciones de video. Hoy en día, se puede recibir televisión digital con servicios de alta definición, existen sitios de Internet que ofrecen películas on-line; y los usuarios realizan carga y descarga de videos con sitios como YouTube. También la grabación y compartir vídeos con teléfonos móviles es generalizada. La videollamada a través de Internet es común y las grandes empresas y organizaciones utilizan aplicaciones de videoconferencia para la colaboración cara a cara en las distintas regiones geográficas; y aún dentro de la misma empresa el tráfico de video crece de tal forma, que se debe tener en cuenta al momento del diseño de la red. Los consumidores son cada vez más exigente en cuanto a la calidad y rendimiento de los productos basados en vídeo. Siguiendo una línea de investigación de tráfico multicast anterior, se pretende comprender la estructura de los datagramas de vídeo y los requisitos que imponen a la red, y obtener conclusiones sobre las mejores opciones de tráfico de video multicast en redes de laboratorio que ayudarán a mejorar el tráfico en la misma.Eje: Arquitectura , Redes y Sistemas OperativosRed de Universidades con Carreras en Informática (RedUNCI

Análisis comparativo de prestaciones de tráfico de video multicast en redes IPv6

Actualmente existe un continuo y creciente número de usuarios de tráfico multimedia en la red. Este hecho involucra que se ha incrementado exponencialmente los requisitos de ancho de banda. Los consumidores son cada vez más exigentes en cuanto a la calidad y rendimiento de los productos basados en el tráfico de vídeo, y, por lo tanto, hay un fuerte incentivo para la mejora continua en las tecnologías multimedia. Comprender la estructura de los datagramas de vídeo y los requisitos que imponen a la red, ayudarán a los administradores de red a mejorar el tráfico en la misma. Siguiendo una línea de investigación de tráfico multicast en el protocolo IPv4 anterior, se pretende continuar con la misma sobre el protocolo avanzado IPv6, comprender las diferencias de estructura de los datagramas de vídeo y los requisitos que imponen a la red, y obtener conclusiones sobre las mejores opciones de tráfico de video multicast sobre IPv6 en redes de laboratorio, midiendo variables de tráfico en la red como velocidad, cantidad de paquetes, retardos, jitter, etc. que ayudarán a mejorar el tráfico en la misma.Eje: Arquitectura, Redes y Sistemas Operativos.Red de Universidades con Carreras en Informática (RedUNCI

Experimental assessment of the effects of cross-traffic on Wi-Fi video streaming

Wi-Fi networks are the first and sometimes only choice for the video streaming in homes, airports, malls, public areas and museums. However, Wi-Fi networks are vulnerable to interference, noise and have bandwidth limitations. Due to the intrinsic vulnerability of the communication channel, and the large number of variables involved, simulation alone is not enough in the evaluation of the performance of wireless networks. Actually, there is a tendency to give experimental tests a central role in the assessment of Wi-Fi networks performance. The paper presents an experimental analysis of the effects of cross traffic on the performance of video streaming over Wi-Fi, based on cross-layer measurements. Experiments are carried out in a semi-anechoic chamber, to prevent the results from being influenced by external factors. The experimental results permit to analyze the influence of cross traffic characteristics on cross layer measures and objective video quality metrics evaluated through a standardized approach

Experimental Evaluation of Large Scale WiFi Multicast Rate Control

WiFi multicast to very large groups has gained attention as a solution for multimedia delivery in crowded areas. Yet, most recently proposed schemes do not provide performance guarantees and none have been tested at scale. To address the issue of providing high multicast throughput with performance guarantees, we present the design and experimental evaluation of the Multicast Dynamic Rate Adaptation (MuDRA) algorithm. MuDRA balances fast adaptation to channel conditions and stability, which is essential for multimedia applications. MuDRA relies on feedback from some nodes collected via a light-weight protocol and dynamically adjusts the rate adaptation response time. Our experimental evaluation of MuDRA on the ORBIT testbed with over 150 nodes shows that MuDRA outperforms other schemes and supports high throughput multicast flows to hundreds of receivers while meeting quality requirements. MuDRA can support multiple high quality video streams, where 90% of the nodes report excellent or very good video quality