Models and approximations for the fast calculation of packet delay variation

通过互联网传输的信息，比如从Web服务器到用户，需要一些时间才能到达用户。任何在互联网上看过视频的人都注意到，在图片真正出现在屏幕上之前需要一段时间。它也证明了这个延迟并不总是相同的，而是围绕某个平均值变化。这被称为传输的“抖动”，它可能是服务质量差的原因，例如对于双向视频会议，它可能使图像和声音冻结甚至完全消失。因此，运营商在设计网络时需要考虑到这种抖动，并尽可能地控制它。这反过来意味着，每当提出新配置时，他们的设计工具必须能够实际计算此抖动的值。在给定的规划中，这种计算必须进行大量的次数，因此需要既快速又准确的技术。本项目的目标是找到满足这两个要求的计算方法。然后，它们将被纳入网络设计工具，这将为运营商提供一种有效的手段，以更好的服务质量和更低的成本规划网络。这也将使我们能够扩展我们对各种网络设计的研究，以考虑抖动，从而提高其准确性和有效性。从长远来看，这项研究将提高加拿大公司在世界电信市场的地位，并加强加拿大作为该领域的领导者的作用。

The information transmitted over the Internet, say from a web server to a user, needs some time to reach the user. Anybody who has watched video on the Internet has noticed that it takes a little while before the picture actually appears on the screen. It also turns out that this delay is not always the same but varies around some average value. This is called the ``jitter'' of the transmission and it can be the cause of poor service, say for instance for a two-way video conference, where it could make the image and sound freeze or even disappear completely. Operators therefore need to design their networks to take this jitter into account and try to control it as much as possible. This in turn means that their design tools must be able to actually compute the value of this jitter whenever a new configuration is proposed. This calculation has to be done a large number of times in a given planning so that one needs techniques that are both fast and accurate. The objective of this project is to find calculation methods that meet these two requirements. They will then be included into network design tools which will give operators an efficient mean to plan networks with better quality of service and lower cost. This will also allow us to extend our research on the design of various kinds of networks to take jitter into account thereby increasing their accuracy and effectiveness. In the longer term, this research will improve the position of canadian companies in the world telecommunication market and re-inforce the role of Canada as a leader in the field.