Evaluation of coded speech quality degraded by cell loss in ATM networks
Hiromi Nagabuchi, Nobuhiko Kitawaki · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 1992
Abstract The asynchronous transfer mode (ATM) is considered interesting as the signal transfer mode in multimedia communication which can realize flexible and efficient channel usage. In ATM, the quality of speech is degraded by cellular handling of the signal which has a property different from the quality degradation in the conventional STM. Due to the small number of studies reported so far, the characteristics of the quality degradation have not been well understood. This paper presents the design data for the speech quality in ATM network and considers the cell loss as the inherent factor degrading the quality in ATM. The complex effect of the cell loss and the coding distortion on the overall subjective quality and the articulation of the speech is measured and discussed. For several methods of speech coding and cell structures, the degradation of quality is examined when the cell loss rate increases. It is shown that the 32‐kbit/s embedded ADPCM with the cell structure, where the lower two bits are selected with priority to suffer the loss, has a high immunity to the cell loss. Through the quality evaluation of the coded speech containing a cell loss, two factors are shown to be important: the speaker and the speech power at the site of cell loss. As a result of this study, new knowledge is obtained concerning the speech quality degradation characteristics in ATM network, and the data and knowledge useful in the speech quality design of ATM network are obtained.