24 GHz cmwave radio propagation through vegetation: Suburban tree clutter attenuation

This paper presents a measurement-based analysis of cm-wave radio propagation through vegetation at 24 GHz. A set of dedicated directional measurements were performed with horn antennas located close to street level inside a densely-vegetated area illuminated from above. The full azimuth was examined for the elevation range from +10 to +30 degrees at each of the measurement positions in order to explore the directional characteristics of the channel. The detailed analysis of the spatial multipath components scattered from the trees suggests, in average, the presence of 5 strong tree-scattered components per location with an azimuthal deviation of approximately 20 degrees between the strongest and the direct transmitter-receiver components. A diversity gain of approximately 7 dB is estimated, plus 2 dB extra in the case of considering multi-beam combining techniques. Tree clutter attenuation was found to be in the range 2.6-3.8 dB/m for the first meters inside the vegetated area. This attenuation can be predicted by the current ITU-R models, although some modifications are suggested. Single-tree attenuation was estimated to be approximately 20 dB. The different models and observations presented along the paper are useful for simulation and radio network planning of future wireless systems operating at 24 GHz in presence of vegetation.