SIMULATION AND MODELLING OF VARIABLE BIT RATE MPEG VIDEO TRANSMISSION OVER ATM NETWORKS

Abstract

This paper proposes an efficient transmission mechanism based on frame spreading, for variable bit rate (VBR) MPEG compressed video, through an asynchronous transfer mode (ATM) multiplexer, such as a cable head-end. We implement a priority scheme in a software MPEG encoder which produces proportionate traffic in both (i.e. high and low) priority partitions for all three types of video frames used in MPEG, i.e. intraframe (I), predicted (P) and bidirectionally interpolated (B). Furthermore, we simulate an ATM multiplexing scheme with a pushout buffer mechanism providing priority scheduling at the multiplexer for the two video partitions. We load the multiplexer with VBR MPEG traffic and collect performance statistics such as the cell loss ratios for various frame spreading scenarios. In order to study the transmission mechanisms via simulation, we develop two statistical models, using the transform-expand-sample technique (TES) for VBR MPEG video with two levels of priority. The first model is matched with the empirical histogram and autocorrelation function of each frame type (I, P and B). The second model is created with the assumption of a gamma distribution for the number of bits in each frame type. We conduct experiments using both models and compare the results.