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Digital Television (digital + television)

Distribution by Scientific Domains
Engineering75%

Selected Abstracts

Proxy caching algorithms and implementation for time-shifted TV services

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 2 2008
Tim Wauters
The increasing popularity of multimedia streaming applications introduces new challenges in content distribution networks (CDNs). Streaming services such as Video on Demand (VoD) or digital television over the Internet (IPTV) are very bandwidth-intensive and cannot tolerate the high start-up delays and poor loss properties of today's Internet. To solve these problems, caching (the initial segment of) popular streams at proxies could be envisaged. This paper presents a novel caching algorithm and architecture for time-shifted television (tsTV) and its implementation, using the IETF's Real-Time Streaming Protocol (RTSP). The algorithm uses sliding caching windows with sizes depending on content popularity and/or distance metrics. The caches can work in stand-alone mode as well as in co-operative mode. This paper shows that the network load can already be reduced considerably using small diskless caches, especially when using co-operative caching. A prototype implementation is detailed and evaluated through performance measurements. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Fusion of digital television, broadband Internet and mobile communications,Part I: Enabling technologies

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2007
F. L. C. Ong
Abstract The introduction of digital video broadcasting (DVB) satellite systems has become an important tool for future mobile communication and is currently a focus in several research areas such as the integration of DVB satellite systems with different wireless technologies. This tutorial consists of two parts, Enabling technologies and Future service scenarios, which aims to provide an introduction to the current state-of-the-art of DVB standards over satellite and its fusion with mobile and Internet technologies. This paper, Enabling technologies, focuses on providing an overview of the different technologies and issues that facilitates better understanding of the current and future operational scenarios, whereas the second paper, Future service scenarios will emphasize future research directions in this research area. In the first part, the paper will initially be focused on the introduction of different DVB satellite systems, i.e. DVB- via satellite (DVB-S), DVB return channel by satellite (DVB-RCS) and second-generation DVB system for broadband satellite services (DVB-S2). This is then followed by a description of the different Internet Protocol (IP) technologies used to support macro- and micro-mobility and the migration strategies from IP version 4 (IPv4) to IP version 6 (IPv6). Finally, the different security mechanisms for the DVB system and end-to-end satellite network are addressed. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Internal DTV antenna for folder-type mobile phone

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2006
Kin-Lu Wong
Abstract By using the upper and lower ground planes of a folder-type mobile phone, a novel internal shorted dipole antenna for digital television (DTV) signal reception in the 470,806-MHz band is presented. The shorted dipole antenna further comprises an internal matching circuit, which includes a chip capacitor and two narrow metal strips, for achieving improved impedance matching over the DTV band of 470,806 MHz. The proposed DTV antenna was constructed and studied. The measured return loss for the operating frequencies over the DTV band is better than 2.5:1 VSWR. In addition, good radiation characteristics are also obtained. Design considerations of the proposed internal DTV antenna are described. A parametric study of the internal matching circuit on the impedance matching of the antenna is also presented. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1015,1019, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21587 [source]

Imaging geophysical data,taking the viewer into account

ARCHAEOLOGICAL PROSPECTION, Issue 1 2004
T. J. Dennis
Abstract A common way of presenting geophysical data from two-dimensional sources is as a grey-scale image. Some theoretical background to discrete image representation is described, and the deleterious effects of inappropriate (too sparse) sampling and display of such images discussed in an archaeological context. In high-quality images, such as magazine illustrations or digital television, the sampling densities can be sufficiently high to avoid the appearance of artefacts. Geophysical images in contrast are often sampled at very low densities; if the effective area of each sample is significantly less than the sample spacing, then the classic effect called ,aliasing' in communication engineering, caused by the violation of Nyquist's criterion, will be seen. Knowledge of the sensor's footprint can be used to select an appropriate sample density, and so minimize this source of distortion. To maximize the visibility of what may be low-contrast structures immersed in a high level of background noise, it is helpful also to consider the bandpass nature of the spatial frequency response of the human visual system. The non-linear phenomenon of visual masking is shown to influence the choice on presentation methods. Copyright © 2004 John Wiley & Sons, Ltd. [source]