Control of real-time multimedia applications in best-effort networks

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Title: Control of real-time multimedia applications in best-effort networks
Author: Ye, Dan
Abstract: The increasing demand for real -time multimedia applications and the lack of quality of service (QoS ) support in public best -effort or Internet Protocol (IP ) networks has prompted many researchers to propose improvements on the QoS of such networks . This research aims to improve the QoS of real -time multimedia applications in public best -effort networks , without modifying the core network infrastructure or the existing codecs of the original media applications . A source buffering control is studied based on a fluid model developed for a single flow transported over a best -effort network while allowing for flow reversal . It is shown that this control is effective for QoS improvement only when there is sufficient flow reversal or packet reordering in the network . An alternate control strategy based on predictive multi -path switching is studied where only two paths are considered as alternate options . Initially , an emulation study is performed , exploring the impact of path loss rate and traffic delay signal frequency content on the proposed control . The study reveals that this control strategy provides the best QoS improvement when the average comprehensive loss rates of the two paths involved are between 5 % and 15 % , and when the delay signal frequency content is around 0 .5 Hz . Linear and nonlinear predictors are developed using actual network data for use in predictive multi -path switching control . The control results show that predictive path switching is better than no path switching , yet no one predictor developed is best for all cases studied . A voting based control strategy is proposed to overcome this problem . The results show that the voting based control strategy results in better performance for all cases studied . An actual voice quality test is performed , proving that predictive path switching is better than no path switching . Despite the improvements obtained , predictive path switching control has some scalability problems and other shortcomings that require further investigation . If there are more paths available to choose from , the increasing overhead in probing traffic might become unacceptable . Further , if most of the VoIP flows on the Internet use this control strategy , then the conclusions of this research might be different , requiring modifications to the proposed approach . Further studies on these problems are needed .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1157
Date: 2009-05-15


Control of real-time multimedia applications in best-effort networks. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1157 .

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