Performance of CSMA with priority acknowledgements on intrabuilding power line local area networks

The use and performance of carrier-sense multiaccess (CSMA) with priority acknowledgements (PA) for medium access control on intrabuilding power-line communication networks are described. Such networks, while universal in building coverage at no incremental installation cost and readily accessed, suffer from highly variable unpredictable signal-to-noise ratio. The architecture of the CSMA implementation is discussed, along with its advantages relative to token-passing or polling-access control schemes. Choice of the best packet length, in terms of throughput maximization, approximates 1000 bits. Delay-throughout performance is measured, and the effects of performance of the power-line channel behavior are ascertained. Extensive tests were conducted using channel bit rates from 1200 to 9600 b/s, with FSK (frequency-shift keyed) and spread-spectrum PSK (phase-shift keyed) modems transmitting at 3 V rms at frequencies ranging from 40 to 120 kHz. Included are results for potentially difficult cases involving transmissions across power phases