Subjective assessment of ATM video impairment using multiservice models

The authors discuss the investigation of the following factors for video transmission in ATM networks: the temporal pattern of cell loss; the effect of this loss on the human viewer (subjective quality); the influence of scene contest; and the efficiency of the network for a given level of picture quality. They constructed a network model of multiplexed links and intermediate switching nodes. One video channel served as the observation channel while the model simulated other channels in a multiplexer. This approach obviated the need for the provision of a large number of truly independent video sources which is difficult to realise in practice. For simplicity it was assumed that, in overload conditions, the proportion of lost cells is the same for all channels. Although in reality more sophisticated cell discard rules may apply (policing functions) their introduction would only add another variable to the effects of network impairments