Year: 1989
Type: dissertation
Abstract: Asynchronous Transfer Mode (A TM) is fast emerging as the preferred information transfer technique for future Broadband Integrated Services Digital Networks (BISON), offering the advantages of both the simplicity of time division circuit switched techniques and the flexibility of packet switched techniques.A TM networks with their inherent rate flexibility offer new opportunities for the efficient transmission of real time Variable Bit Rate (VBR) services over such networks.Since most services are VBR in nature when efficiently coded, this could in turn lead to a more efficient utilisation of network resources through statistical multiplexing.Video communication is typical of such a service and could benefit significantly if supported with VBR video over A TM networks.The primary objective of the research described in this thesis is to address the various issues associated with the transmission of VBR video over an ATM network called the Orwell Ring.There are two major issues concerned in this work.One relates to the relative merits of VBR video, and the other, to the efficient transmission and control of VBR video traffic over the ring.VBR video signal statistics were collected from a COST211 video-conferencing codec which was modified to operate as a VBR video source.The picture material investigated were mainly head and shoulders scenes corresponding to videophone and video-conferencing type pictures.The statistics collected enabled an assessment of the relative merits of the type of VBR video sources concerned.The results indicated a bandwidth saving of about 2-3 over constant bit rate video, as well as other advantages such as improved picture quality and simpler codec design.The effects of statistical multiplexing the outputs of uncorrelated VBR video sources were also investigated.The signal statistics collected also provided information on the characteristics of the VBR video signals, and enabled a simple VBR video source model to be developed.The model exhibited most of the characteristics of the video sources upon which it was modelled, but in view of the constraints in computing resources, some of the simplifications made suggested that the scope of the model was somewhat limited.It is nevertheless considered to be adequate for this study.Simulation studies of the transmission of VBR video over the Orwell Ring have shown that with correct dimensioning of the ring, proper exercise of the traffic control mechanisms provided by the protocol, and a reasonable amount of buffering, a good Quality of Service (QOS) can be obtained for all services in a multi-service environment.Cell loss rate and call i
Author: Hin-Soon Chin
Institution: Loughborough University
Language: English
Subfield: Computer Networks and Communications
Field: Computer Science
Domain: Physical Sciences
Open Access status: green
Funder: Loughborough University
OpenAlex ID: W1614186219