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Sufficient Bandwidth (sufficient + bandwidth)

Distribution by Scientific Domains

Engineering	60%

Selected Abstracts

Wireless provision of true VoD services and fast access to Internet

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2002
E. Pallis
Abstract The evolution of digital compression techniques has made possible the provision of full-motion video services through networking infrastructures of sufficient bandwidth. This paper presents a wireless broadband network, which is capable of providing true interactive VoD services (with full VCR functions) and fast access to Internet to a number of simultaneous clients. The network is based on frequency hopping spread spectrum (FHSS) technology operating in the 2.4 GHz frequency band. The paper describes the system architecture and configuration adopted in a real environment trial and elaborates on the provided picture quality in a multi-client environment. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Transcoding media for bandwidth constrained mobile devices

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 2 2005
Kevin Curran
Bandwidth is an important consideration when dealing with streaming media. More bandwidth is required for complex data such as video as opposed to a simple audio file. When delivering streaming media, sufficient bandwidth is required to achieve an acceptable level of performance. If the information streamed exceeds the bandwidth capacity of the client the result will be ,choppy' and incomplete with possible loss of transmission. Transcoding typically refers to the adaptation of streaming content. Typical transcoding scenarios exploit content-negotiation to negotiate between different formats in order to obtain the most optimal combination of requested quality and available resources. It is possible to transcode media to a lesser quality or size upon encountering adverse bandwidth conditions. This can be accomplished without the need to encode multiple versions of the same file at differing quality levels. This study investigates the capability of transcoding for coping with restrictions in client devices. In addition, the properties of transcoded media files are examined and evaluated to determine their applicability for streaming in relation to a range of broad device types capable of receiving streaming media.,Copyright © 2005 John Wiley & Sons, Ltd. [source]

Small microstrip patch antennas with short-pin using a dual-band operation

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008
Cheol Yoon
Abstract This article presents the design and fabrication of a short-pin dual-band E-shaped microstrip patch antenna for application in a 2.630,2.655 GHz band satellite-DMB with a 5.725,5.825 GHz band wireless LAN. The prototype consist of a short-pin and E-shaped patch. To obtain sufficient bandwidth in VSWR < 2, an air layer is inserted between the ground plane and the substrate. A small short-pin patch that has a dual-band characteristic is used. Important design parameters are the slot's existence, length, the air-gap's height, the feed point's position, and the short-pin's existence and point position. From these optimized parameters, an E-shaped antenna is fabricated and measured. The measured results of the fabricated antenna are obtained individually at 200 and 700 MHz bandwidths in VSWR < 2 referenced to the center frequency, and the individual gain at 8.79 and 10.26 dBi. The experimental 3 dB beam width is shown to be broad across the pass band in the E-plane, and in the H-plane is individually 73°, 65°, 74°, and 42°, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 367,371, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23099 [source]

UMTS diplexer design using dual-mode ring resonators

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007
Min-Hua Ho
Abstract In this letter, we propose a novel design of a UMTS diplexer using dual-mode rectangular ring-resonators. The diplexer is composed of two rectangular rings, which termed as the Tx- and Rx-ring, with each ring its input and output ports separated from each other by a quarter-wavelength to create the degenerate-mode resonance. The ratio of the long- and short-side dimension of rectangular ring can be used to fine tune the passband's bandwidth and the ratio is properly chosen to achieve sufficient bandwidth required by the UMTS diplexer applications. An enhanced parallel-coupled structure is introduced in the circuit to replace the conventional end-gap coupling for reducing the insertion losses in the passband. The effect of the coupling-line length is also simulated and the resulting data are used to precisely tune the positions of the zeros. In the zero assignment, one of the zeros possessed by each ring filter is managed to be implanted in the passband of its counterpart filter for increasing the isolation between the Rx- and Tx-port. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 63,65, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22030 [source]

Slice-selective FID acquisition, localized by outer volume suppression (FIDLOVS) for 1H-MRSI of the human brain at 7,T with minimal signal loss

NMR IN BIOMEDICINE, Issue 7 2009
Anke Henning
Abstract In comparison to 1.5 and 3,T, MR spectroscopic imaging at 7,T benefits from signal-to-noise ratio (SNR) gain and increased spectral resolution and should enable mapping of a large number of metabolites at high spatial resolutions. However, to take full advantage of the ultra-high field strength, severe technical challenges, e.g. related to very short T2 relaxation times and strict limitations on the maximum achievable B1 field strength, have to be resolved. The latter results in a considerable decrease in bandwidth for conventional amplitude modulated radio frequency pulses (RF-pulses) and thus to an undesirably large chemical-shift displacement artefact. Frequency-modulated RF-pulses can overcome this problem; but to achieve a sufficient bandwidth, long pulse durations are required that lead to undesirably long echo-times in the presence of short T2 relaxation times. In this work, a new magnetic resonance spectroscopic imaging (MRSI) localization scheme (free induction decay acquisition localized by outer volume suppression, FIDLOVS) is introduced that enables MRSI data acquisition with minimal SNR loss due to T2 relaxation and thus for the first time mapping of an extended neurochemical profile in the human brain at 7,T. To overcome the contradictory problems of short T2 relaxation times and long pulse durations, the free induction decay (FID) is directly acquired after slice-selective excitation. Localization in the second and third dimension and skull lipid suppression are based on a T1 - and B1 -insensitive outer volume suppression (OVS) sequence. Broadband frequency-modulated excitation and saturation pulses enable a minimization of the chemical-shift displacement artefact in the presence of strict limits on the maximum B1 field strength. The variable power RF pulses with optimized relaxation delays (VAPOR) water suppression scheme, which is interleaved with OVS pulses, eliminates modulation side bands and strong baseline distortions. Third order shimming is based on the accelerated projection-based automatic shimming routine (FASTERMAP) algorithm. The striking SNR and spectral resolution enable unambiguous quantification and mapping of 12 metabolites including glutamate (Glu), glutamine (Gln), N -acetyl-aspartatyl-glutamate (NAAG), , -aminobutyric acid (GABA) and glutathione (GSH). The high SNR is also the basis for highly spatially resolved metabolite mapping. Copyright © 2009 John Wiley & Sons, Ltd. [source]