A spread-spectrum system with dual processing gains designed for cyclic noise in power line communications

Many electric appliances using power lines for their power supply often tend to emit larger noise to the lines when the absolute instantaneous voltage of the power-supplying AC is higher. Thus, total noise on the lines has positive relation to the AC voltage. In this paper we first model the noise to be cyclic stationary Gaussian with the instantaneous power (variance) proportional to the n-th power of the absolute instantaneous voltage of the AC. Considering this statistical feature of the noise, we also propose a power-line communication system and show its performance. The proposed system employs two processing gains: the smaller one for the period with lower AC voltage and the larger for the rest period.