Development of Integrated image broadcast and unicast systems for heterogeneous network environment

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Owing to the rapid advance of recent image coding technique and the performance of personal computers, the number of terminals with the ability of receiving and sending images are growing dramatically. On the contrary, broadband network is not available for every user and the network environment is very heterogeneous ranging from mere 9600 bps PDC type cellular phone to Giga bit network. The aim of this research was to tackle with various problems under such environment to efficiently transmit images.The outcomes of the research are as follows. We proposed an -innovative method for traffic balancing by the adaptive allocation of contents servers and adaptive replication of contents. We also studied the new rate control for image traffic. As for the layered image coding, we proposed very efficient hierarchical image coding techniques both for loss-less and lossy cases and fine-tuned the parameters for bit assignment for each class. Then we applied them to transparent media scaling and proposed a scheme for flexible and easy bandwidth assignment.From the viewpoint of development of network control method under heterogeneous network environment, we also focused WDM network as very high speed network and proposed an efficient yet simple path assignment algorithms. Then we showed the feasibility of real time traffic engineering with this algorithm. Although it is beyond the scope of our original research proposal, we also studied the routing constructing method of ad-hoc networks assuming the hierarchical transmission since they are. becoming realistic now as the very low speed part of die heterogeneous networks.The research term is now over, however we are still trying to integrate these specific research topics and still developing a prototype commercial system.