Study of the local multipoint distribution service radio channel

Millimeter wave communication systems in the 21.5 to 29.5 GHz band are being developed in the United States and Canada for use in a local multipoint distribution service (LMDS). This paper summarizes radiowave propagation impairments for the LMDS and reports measurement data for small cells. Results include area coverage estimates over a range of basic transmission losses for 0.5-, 1.0- and 2.0-km suburban cells with foliated trees. Multipath, signal attenuation, depolarization, and cell to cell coverage also are discussed. Data indicates a high probability of non-line-of-sight paths due to trees which can cause signal attenuation and signal variability when wind is present. Signal variability was studied using k factors and compared to the Rician cumulative distribution function. Depolarization caused by vegetation and other signal scatterers was found to be an order of magnitude greater than rain-induced depolarization. A simple tapped delay line model is presented to describe multipath for three channel states.