期刊名称：International Journal of Computer Networks (IJCN)
电子版ISSN：1985-4129
出版年度：2011
卷号：3
期号：3
页码：167-177
出版社：Computer Science Journals
摘要：The evident increase in media traffic over Internet is expected to worsen its congestion state. TCP-friendly rate control protocol TFRC is one of the most promising congestion control techniques developed so far. TFRC has been thoroughly tested in terms of being TCP-friendly, responsive, and fair. Yet, its impact on the visual quality and the peak signal-to- noise ratio PSNR of the media traffic traversing Internet is still questionable. In this paper we aimed to point out the enhancements required for TFRC that enables producing the maximum PSNR value for Internet media traffic. Firstly, we suspected the default value of n that represents the number of loss intervals used in calculating the loss event rate in the TFRC equation. This value is recommended to be set to 8 according to the latest RFC of TFRC. We investigated the effect of modifying the TFRC mechanism on the resulting PSNR of the transmitted video over Internet using TFRC via switching n across the values from 2 to 16. We investigated the effect of such variation over a simulated network environment to study its effect on the resulting PSNR for a number of arbitrary video sequences. Our simulations results showed that running TFRC with n=11 led to reaching the maximum PSNR values among all the examined values of n including its default value. Secondly, we tested the impact on the PSNR of another modification in the TFRC mechanism via switching both values of n and Nfb which is frequency of feedback messages sent by TFRC receiver to its sender every round-trip time RTT. The default value of Nfb is 1; hence we scanned every possible combination of n and Nfb ranging from 2 to 16, and from 1 to 4, respectively and recorded the produced PSNR. It was obvious that several other combinations of n and Nfb produced higher PSNR values other than their default values in the request for comment RFC of TFRC. We hereby suggest using an enhanced TFRC that we abbreviated as ETFRC which has the values of n and Nfb value set to 4 and 11 respectively as a replacement for the traditional TFRC to enable reaching higher PSNR for media traffic over Internet.
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