Jitter regulation for multiple streams

摘要

For widely used interactive communication, it is essential that traffic is kept as smooth as possible; the smoothness of the traffic is typically captured by its delay jitter, that is, the difference between the maximal and minimal end-to-end delays. The task of minimizing the jitter is done by jitter regulators that use a limited-size buffer in order to shape the traffic. In many real-life situations regulators must handle multiple streams simultaneously and provide low jitter on each of them separately. Moreover, communication links have limited capacity, and these may pose further restrictions on the choices made by the regulator. This article investigates the problem of minimizing jitter in such an environment, using a fixed-size buffer. We showthat the offline version of the problem can be solved in polynomial time, by introducing an efficient offline algorithm that finds a release schedule with optimal jitter. When regulating M streams in the online setting, we take a competitive analysis point of view and note that, in the upcapacitated case, previous results in Mansour and Patt-Shamir [2001] can be extended to an online algorithm that uses a buffer of size 2·M·B and obtains the optimal jitter possible with a buffer of size B (and an offline algorithm). The question arises whether such a resource augmentation is essential. We answer this question in the affirmative, by proving a lower bound that is tight up to a factor of 2, thus showing that jitter regulation does not scale well as the number of streams increases unless the buffer is sized-up proportionally.