Personal computer communications on intrabuilding power line LAN´s using CSMA with priority acknowledgements

Intrabuilding power lines provide a readily available and easily accessed network for personal computer (PC) communications within buildings. The use and performance of carrier-sense multiple access with priority acknowledgements (CSMA/PA) on such networks is described. The communication characteristics of intrabuilding power-line channels are summarized and found to suffer from highly variable and unpredictable signal-to-noise ratios and bit-error rates. The advantages of CSMA/PA relative to polling and token-passing access protocols are discussed. The architecture of a CSMA/PA implementation is described. The choice of the best data-link packet length is determined from throughput measurements to be approximately 1000 bits. Delay-throughput performance is measured at 1.2, 2.4, 4.8, and 9.6 kb/s using a phase-shift-keyed (PSK) spread-spectrum modem. Results are included for the potentially difficult problem of transmission across power phases. A discussion of results obtained and their implications for PC intrabuilding communications is also included