Realization of next generation multimedia PHS system

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In order to realize the next generation multi-media PHS enabling network access at more than 20Mb/s, the following research results have been obtained by this research work.1. The radio propagation measurement including power delay profile measurement have been done in both indoor and outdoor environments. At the same tune, bit error rate performance has also been measured to reveal the reason of the errors in outdoor environment. The results in outdoor environment have shown the delay spread of about 100ns. In indoor environment, an ultra delay resolution measurement with 0.5ns resolution has shown the possibility of the direct use of the measured delay profile data for computer simulation of transmission quality. This will be considered to ease the establishment of propagation model in indoor environments.2. Computer simulation based on the parallel virtual machine has revealed the possibility of the system parameter for OFDM system in indoor radio environment. And also, the computer … More simulation based on the measured delay profile in indoor radio environment has shown the possibility of the direct use of measured data due to the ultra delay resolution.3. The real hardware system based on the MMAC-HiSWAN has been developed to estimate the proposed symbol timing synchronization circuit. Field test in outdoor environments have confirmed the good bit error rate performance and made possible to evaluate the performance by delay profile characteristics.4. In order to enable the mobile multi-media PHS, the symbol synchronization problem in OFDM system has been researched based on the orthogonal channel interference detecting method. The computer simulation results have shown the effective improvement in FFT timing synchronization. This principle has been followed to develop an adaptive decision circuit based on a neural network which can effectively compensate the linear distortion caused by the DC offset due to multipath propagation.5. For adopting the instantaneous variation of transmission quality, an adaptive transmission rate system based on DAPSK-COFDM system has been proposed. The computer simulation results have shown that the performance of the proposed system is very effective when combined with code-combining diversity reception system based on hard decision Viterbi decoders.6. And finally, combining with space diversity branches, the proposed adaptive transmission rate DAPSK-COFDM system including Viterbi code combiner has been proposed. Its performance will be discussed after constructing the computer simulation system. Less