Study on Multimedia communication systems under heterogeneous network environment

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To avoid congestion in heterongeneous network environment during multimedia communication, it is necessary to discard packets of low priority. From this point of view, the treatment of intermedia priority is treated in this study. Further, the objective evaluation of such a priority structure is also discussed. Our primary result of this study are as follows.For the image media, we developed a novel coding scheme where both the hierarchical strucutre and reversibility are sustained. The coding effiecney of the proposed coding scheme is studied and it is clarified that the proposed shemce has a large advantage. Also, for lossy coding, we found a new conding scheme which has better coding efficiency. In finding them, we utilized the strucutre of sub-band coding.For network control sheme, we developed a new congestion deteciton algorithm where such congestion are detected in very short term, which is mixed with a novel flow control scheme. Computer simulation of this algorithm is also performed and the performance is verified. Further, we imbed this idea into the ABR service class of ATM.As typical application, we also developed a system where Q factor of MPEG streams are dynamically contorlled using this algorithm. This system was also implemented on the real B-ISDN systems.