A Study of Power-Line Communications for Realization of High-speed and High-reliable Home-Network

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The demand for a home network is increasing in recent years, so that power-line communication (PLC) and wireless communications attract attention as newly wiring-less methods. The research and development of high-speed PLC of around 10Mbps using the high-frequency band under 30MHz have become active in Japan. However, since a network topology of a power line is complicated and its transfer function is influenced by the household-electric-appliances which are connected to the power-line, it has been supposed that an estimation method of the transfer function of power-line channel was not easy generally.In 2001, it was shown that the power-line channel must be treated as a distributed constant circuit at the high-frequency band. The distributed constants of a VVF (Vinyl insulation, Vinyl sheath, Flat) cable, which is widely used for the residential power-line in Japan, were obtained. Moreover an estimation method of the transfer function of branched power-line channel was developed. The … More channel was segmented at each branching point, and the segmented piece of the cable was modeled as a four terminal network represented by a transmission matrix. Its elements were determined by the distributed constants when the cable length was given.One of PLC's difficulties is the wiring scheme, which sometimes affects the signal-attenuation property and sometimes introduces an unnecessary radiation due to the electrical unbalance. These problems may occur, when power-line channels are branched, the length of two signaling-wires is different due to switch circuits, and the conventional layout of ground-wire for outlets with ground connecter is used. In 2002, new wiring schemes were proposed. It was shown that the schemes were effective in improving the transmission characteristic of the power-line -channels. Moreover, the scheme allowed us to make the phantom transmission available when 3-wires VVF cables were used. The phantom transmission made the power-line channel-capacity double. The new phantom transmission circuit was developed, and its effectiveness was shown experimentally. Less