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Power-Line Communications
Channel Properties and Communication Strategies
Lars Selander, 1999


This thesis is about power-line communication over the low-voltage grid, which has interested several researchers and utilities during the last decade, trying to achieve higher bit-rates and more reliable communication over the power lines. The main advantage with power-line communication is the use of an existing infrastructure. Wires exist to every household connected to the power-line network.

This thesis starts with a general introduction to power-line communication. Then an existing application, communicating on a low-voltage grid, is investigated in order to obtain some knowledge of how the power line acts as a communication channel. We also expose this system with a load, consisting of a set of industrial machines, to study the change in communication channel quality. After these large-scale measurements we measure some channel characteristics in the same grid. Measurements of the noise level and the attenuation, up to 16 MHz, are reported.

The power-line communication channel can, in general, be modeled as having a time-varying frequency-dependent signal-to-noise ratio over the communication bandwidth. The effect of non-white Gaussian noise on different receiver structures is studied, one ideal and one sub-optimal, and the importance of diversity (in frequency) is illustrated when the set of transmitter waveforms is fixed. We investigate robust, low-complexity, modulation methods which are able to handle unknown phase and attenuation, which simplifies the implementation of the receiver.

Finally we describe a communication strategy that eventually could be used for informa-tion transfer over the power-line communication channel. In doing this we combine cod-ing, frequency diversity and the use of sub-channels (similar to Orthogonal Frequency Division Multiplex). This is a flexible structure which can be upgraded and adapted to future needs.

The entire paper in PDF.