Channel Properties and Communication Strategies
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.