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UBC Theses and Dissertations

Channel characterization and forward error correction coding for data communications on intrabuilding electric power lines Chan, Morgan Hing Lap


The use of intrabuilding electric power lines for data communications and local area networking is of growing interest. In this thesis, an original work to study the very important signal propagation and noise characteristics of the complex and hostile power line networks has been completed. Various impairments such as high and varying signal attenuation levels, periodic signal fading and impulse noise were identified. Estimates of the amplitude, pulse width and interarrival distributions of impulse noise were obtained. Communication signal attenuation of power line networks was explored. The effects of electrical loading on these communication channel factors were examined. Implications of the results for intrabuilding communications are addressed. To combat power line impulse noise, channel fading, attenuation and other impairments, forward error correction (FEC) coding and bit interleaving is proposed and shown to be very effective, and is an essential component for reliable communication over power lines. The performance of interleaved hard and soft decision decoding of repetition codes with or without erasure has been analysed, using a simple first order power line noise model. Various random and burst error correcting block codes have been evaluated, using actual recorded bit error patterns encountered on power line data channels. Based on studies of the channel and error correction coding, an actual low cost FEC coded communication system for use on intrabuilding power lines was successfully designed, implemented and tested. Real time performance results of coded and uncoded data transmissions on typical power lines were experimentally determined. Convolutional codes as well as repetition coding and bit interleaving are used to overcome burst errors and other impairments encountered on power line channels. The emphasis is on high speed transmission at bit transmission rates up to 57.6 kbits/s. Typical practical coding gains from 10 to 20 dB were achieved at bit error rate of 10⁻⁴ on various noisy links. It is successfully demonstrated that with appropriate and inexpensive FEC coding, reliable high speed data transmission over power lines is feasible, even at very small interleaving delay.

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