Efficient modeling of VBR MPEG-1 coded video sources

The performance evaluation of broadband networks requires statistical analysis and modeling of the actual network traffic. Since multimedia services, and especially variable bit rate (VBR) MPEG-coded video streams are expected to be a major traffic component carried by these networks, modeling of such services and accurate estimation of network resources are crucial for proper network design and congestion-control mechanisms that can guarantee the negotiated quality of service at a minimum cost. The layer modeling of MPEG-1 coded video streams and statistical analysis of their traffic characteristics at each layer is proposed, along with traffic models capable of estimating the network resources over asynchronous transfer mode (ATM) links. First, based on the properties of the entire MPEG-1 sequence (frame layer signal), a model (Model A) is presented by correlating three stochastic processes in discrete time (autoregressive models), each of which corresponds to the three types of frames of the MPEG encoder (I, P, and B frames). To simplify the traffic Model A and to reduce the required number of parameters, we study the MPEG stream at a higher layer by considering a signal, which expresses the average properties of I, P, and B frames over a group of picture (GOP) period. However, models on this layer cannot accurately estimate the network resources, especially in multiplexing schemes. For this reason, an intermediate layer is introduced, which exploits and efficiently combines information of both the aforementioned layers, producing a model (Model B), which requires much smaller number of parameters than Model A and simultaneously provides satisfactory results as far as the network resources are concerned. Evaluation of the validity of the proposed models is performed through experimental studies and computer simulations, using several long duration VBR MPEG-1 coded sequences, different from that used in modeling. The results indicate that both Models A and B are good estimators of video traffic behavior over ATM links at a wide range of utilization.