One wire PLC system for inter-floor connectivity

The conventional narrowband power-line communication (NB-PLC) is a two-wire system, that has injected its signal between wires using a capacitive coupler. When communicating between floors at a large-sized building, the signal has to travel over long-distances across a switchboard which supplies electricity to distribution boards. Moreover, the signal is attenuated not only at the switchboard but also at the distribution boards. Therefore signal amplifiers had to be installed at the boards. In this paper, a single wire PLC solution is proposed to shorten the communication distance and reduce the attenuation by taking a shortcut of the signal traveling path. It is described experimentally that the earth could be used as its signal returning path to the signal source. Therefore a single wire is enough to inject and receive the signal. An inductive coupling method suitable to this system is also proposed. The signal attenuation of the proposed system was 30 dB better than that of the conventional two-wire system for our university building. The achieved performances of PLC modems also showed that the proposed system was useful.