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UBC Theses and Dissertations

Design and performance analysis of intrabuilding power line carrier sense multiple access data networks Onunga, John Ogutu


The search for cost-effective, and flexible means of connecting computers in a localized community has received considerable attention, during the last few decades. Intrabuilding power lines (IPL) provide a readily available and easily accessed network for data communications within buildings. In this thesis, a new generation of low-cost computer networks using carrier sense multiple access with priority acknowledgement (CSMA/PA) on intrabuilding power lines has been designed, analysed, implemented and tested. The communication characteristics of IPL channels are summarized, and found to suffer from highly variable, ever-changing and unpredictable signal-to-noise ratio and bit error rates. CSMA is an efficient and reasonably simple means for decentralized control of access to a shared communication channel. The advantages of CSMA/PA relative to those of polling and token passing access protocols are discussed. The design and implementation of an operational five-node IPL network using CSMA/PA is described. Choice of the best data link packet length is determined from throughput measurements to approximate 1000 bits. The performance of a finite 'user CSMA/PA is analysed based on power line channel characteristics which include high and variable channel error rates, large detection delays and significant effects of acknowledgement traffic. The analysis is generally applicable to noisy channels where messages and acknowledgements share a communication bandwidth. Delay-throughput performance measurements are obtained from an actual noisy five-node intrabuilding power line network operating at transmission rates ranging from 1.2 - 9.6 kbit/s and shows excellent agreement with analytical results. IPL network performance deteriorates rapidly with increasing channel errors and changes with electrical loading over time. An adaptive automatic- repeat request (ARQ) switching scheme has been proposed and shown to be very effective in improving IPL network performance whenever the channels are in a poor quality state, while preserving the maximum achievable performance when the channels are in a good quality state. The use of such an ARQ switching scheme with FEC and proper routing algorithms provide the most effective foundation of realizing efficient and reliable intrabuilding power line computer networks.

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