| Research Abstract |
The aim of this study is to globally investigate both spatial and temporal signal processing in a physical layer and protocol in a network layer in viewpoints of adaptive signal processing, information theory, and network theory as key technologies for higher speed and more reliable multimedia wireless communications. The spatial and temporal signal processing covers information compression, error control, and filtering suitable for multimedia information sources and mobile radio channels. The protocol should cover access control considering transparency with wired networks and inherent properties of mobile radio channels. First, in a physical layer, we have studies signal processing in space and time domains based on universal information compression adaptable to any information media source and adaptive array antenna, adaptive digital filter, and codec (encoder and decoder) robust against multipath fading and interference. For instance, (1) mathematical modeling of multimedia informa
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tion source, and proposal and investigation of novel universal information compression schemes based on modification of arithmetic coding and LZW coding in which the mathematical modeling and a method to identify each model are used. (2) Derivation of optimum receivers in space and time domains using adaptive array antenna and adaptive controlling algorithms. (3) Proposal and optimization of space and time channel coding using adaptive array antenna. (4) Proposal of a method of measuring traffic variance of multimedia CDMA wireless communication systems and a method of adaptive controlling the processing gain and transmission power for individual media. (5) Proposal of a novel scheme of generating a group of spreading codes and a scheme of canceling interference in space and time domains for the purpose of improving frequency efficiency in CDMA systems. Second, in a network layer, we have investigated various problems in outage probability of packets and processing delay due to inherent properties of wireless mobile channels such as multipath fading, problems in access control and routing maintaining transparency with wired networks. For instance, (1) Proposal of novel schemes of adaptive controlling transmission power, packet length, processing gain for multimedia wireless CDMA network. (2) Classification and performance analysis of various hybrid schemes such as CSMA/CD, ALOHANET, DS/CDNA, multi-carrier FH/CDMA system and so far. Less
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