Performance characterisation of millimetre wave mobile radio systems in forests

The frequencies in the oxygen absorption band in the region of 60 GHz have been suggested for urban microcellular communications. This is due to the extra attenuation exhibited by the atmosphere in this frequency region, thus allowing for greater frequency re-use to be employed. Multipath in a microcellular forest environment due to reflections and scatter off foliage, with line-of-sight (LOS) prevailing, has not been examined. This study evaluates the severity of multipath in a mobile radio microcellular forest channel due to the presence of foliage. A number of measurements have been made at 62.4 GHz in the Forest of Dean, to evaluate the performance of millimetric cellular mobile radio communications for military applications. Measurements have been made by transmitting a continuous wave (CW) signal from a fixed base to a mobile receiver, and recording the signal envelope variation as a function of mobile position. The results of the propagation experiments are presented. Cumulative distribution functions for the received signal envelopes, as well as corresponding power spectra, are shown and described. A simple ray model is developed to assist in interpreting the experimental results obtained in this type of environment.