THE EFFECT OF MULTIPLE TIME SCALES AND SUBEXPONENTIALITY IN MPEG VIDEO STREAMS ON QUEUING BEHAVIOR

Guided by the empirical observation that realtime MPEG video streams e xhibit both multiple time scale and subexponential characteristics, we construct a video model that captures both of these characteristics a nd is amenable to queueing analysis, We investigate two fundamental ap proaches for extracting the model parameters: using sample path and se cond-order statistics-based methods. The model exhibits the following two canonical queueing behaviors. When strict stability conditions are satisfied, i.e., the conditional mean of each scene is smaller than t he capacity of the server, precise modeling of the interscene dynamics (long-term dependency) is not essential for the accurate prediction o f small to moderately large queue sizes, In this case, the queue lengt h distribution is determined using quasistationary (perturbation theor y) analysis. When weak stability conditions are satisfied, i.e., the c onditional mean of at least one scene type is greater than the capacit y of the server, the dominant effect for building a large queue size i s the subexponential (long-tailed) scene length distribution, In this case, precise modeling of intrascene statistics is of secondary import ance for predicting the large queueing behavior, A fluid model, whose arrival process is obtained from the video data by replacing scene sta tistics with their means, is shown to asymptotically, converge to the exact queue distribution. Using the transition scenario of moving from one stability region to the other by a change in the value of the ser ver capacity, we synthesize recent queueing theoretic advances and ad hoc results in video modeling, and unify a broad range of seemingly co ntradictory experimental observations found in the literature, As a wo rd of caution for the widespread usage of second-order statistics mode ling methods, we construct two processes with the same second-order st atistics that produce distinctly different queueing behaviors.