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On the Impact of Loss and Delay Variation on Internet Packet Audio Transmission
 

Summary: On the Impact of Loss and Delay Variation on Internet Packet
Audio Transmission
Lopamudra Roychoudhuri , Ehab Al-Shaer and Gregory B. Brewster
School of Computer Science, Telecommunications and Information Systems,
DePaul University, 243 S. Wabash Ave., Chicago, IL, U.S.A. 60604
Abstract
The quality of audio in IP telephony is significantly influenced by various factors, including type of encoder, delay, delay
variation, rate and distribution of packet loss, and type of error concealment. Hence, the performance of IP telephony
systems is highly dependent on understanding the contribution of these factors to audio quality, and their impact
on adaptive transport mechanisms such as error and buffer control. We conducted a large-scale audio transmission
experiment over the Internet in a 12-month period in order to evaluate the effects and the correlation of such parameters
on audio transmission over IP. We have noticed that the correlation of loss and delay is not linear, but stronger
correlation is observed as the delay approaches certain thresholds. We have made a number of new observations on
various delay thresholds that are significant for loss prediction for adaptive audio transmission over IP networks. We
also have made new observations to assess the audio quality of PCM -Law and G.728 codecs under different loss
and delay conditions. The paper provides a number of recommendations for implementing efficient adaptive FEC
mechanisms based on our measurement observations and analysis.
Key words: Monitoring, Internet Measurement, IP telephony, VoIP
1 Introduction
The human ear is much more sensitive to quality degra-

  

Source: Al-Shaer, Ehab - School of Computer Science, Telecommunications and Information Systems, DePaul University

 

Collections: Computer Technologies and Information Sciences