多対多通信を用いたコンピュータネットワークの性能評価に関する研究

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We have been focusing on DS-CDMA(Direct Sequence-Code Division Multiple Access) systems with perfect/imperfect power control, and overlaid structures with interference suppression.1. Wireless systems with perfect/imperfect power control and sectoringBased on the IS-95 protocol, a hierarchical cellular model of the reverse link is proposed, in which we assume that the received signal follows log-normal statistics, and the multi-beam antennas are employed to divide the cells. The system capacity plane and the outage probability are examined and quantified when the system is with the perfect/imperfect power control and the perfect/imperfect sectorization. According to our numerical results, we can increase the system capacity 2.3 times more than the one of the nonhierarchical cellular system. A method for the performance evaluation of the hierarchical system is also proposed for the forward link with the power control. The propagation characteristic is assumed as the log-normal statistics. The system capacity and the outage probability of macrocell, and microcell areinvestigated. The system capacity can be increased 3.1 times compared with that of the nonhierarchical system.2. Overlaid cellular systems with interference suppressionWe investigate the feasibility of the spectrum overlaid systems of TDMA/W-CDMA and N-CDMA/W-CDMA, in which the interference suppression technologies are adopted. When the systems are assumed with the perfect power control, the system capacity trade-offs and the spectrum efficiency are studied when the systems are with both slight and serious shadow fadings. We introduce the notch filtering depth p and signal level clipping depth q. According to the numerical results p and q can be flexibly selected to ensure higher spectrum efficiency.