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Reports (Research Report) Year : 2000

Queueing Analysis of Simple FEC Schemes for IP Telephony


In interactive voice applications, FEC schemes are necessary for the recovery from lost packets. These schemes need to be simple with a light coding and decoding overhead so as not to impact the interactivity. The objective of this paper is to study a well known simple FEC scheme that has been proposed and implemented, in which for every packet $n$, some redundant information is added to some subsequent packet $n + \phi$. If packet $n$ is lost, it will be reconstructed in case packet $n+\phi$ is well received. The quality of the reconstructed copy of packet $n$ will depend on the amount of information of packet $n$ carried by packet $n+\phi$. We propose a detailed queueing analysis based on a ballot theorem, and obtain simple expressions for the audio quality as a function of the amount of redundancy and its relative position with respect to the original information. For a utility function that is linear in the amount of information, the analysis shows that this FEC scheme does not scale well and any amount of added redundancy might cause a degradation in the overall quality. We then introduce and analyze other utility functions in order to obtain a quality function that is better adapted to the characteristics of this kind of applications.


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Dates and versions

inria-00072647 , version 1 (24-05-2006)


  • HAL Id : inria-00072647 , version 1


Eitan Altman, Chadi Barakat, Victor Manuel Ramos Ramos. Queueing Analysis of Simple FEC Schemes for IP Telephony. [Research Report] RR-3998, INRIA. 2000, pp.34. ⟨inria-00072647⟩
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