ATM is a key technology in the construction of the broadband ISDN. The introduction of the ATM concept significantly influences the coding of video services, i.e. from CBR to VBR video coding. The major advantages of VBR coding are consistent picture quality, bandwidth saving, and delay reduction. However, one of the major drawbacks is cell loss due to network congestion and consequent aggravated picture degradation. Recently, many compensative methods have been proposed to make the cell loss imperceptible. Two layer coding is supposed to be one of the very promising methods transmitting VBR video traffic over ATM networks.
Since the channel capacity for each information source is allocated dynamically in ATM networks, source models are especially important for estimating required channel capacity.
In this thesis, a model for two-layered video traffic is proposed and the characteristics of this model and the effects of two-layer coding schemes in ATM networks is studied. First, from the experimental data of the 2-layer coded video traffics, it is observed that traffic patterns of base layer and enhanced layer are highly correlated to each other, when constant image quality is kept. With this observation, coded two layered video traffic can be modeled as 2-dimensional Markov chain. This model well fit the real experimental data.
This model was used for the analysis of the performance of statistical multiplexer with priorities in ATM networks. As a buffer control model, selective input buffer control discipline scheme was used.
As a result of this analysis, we can understand the effect of multiplexing the input sources which are crosscorrelated. And network and image coder can estimate the performance of network, as the change of base layer ratio in the total generated data rates. Also, if the performance measure is adquately defined, the optimal ratio of base layer in total generated data rate can be found.
