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Field tests have been performed in various environments in the Chicago area to evaluate cochannel isolation characteristics. As cell sizes shrink in order to increase capacity, cellular systems must address cochannel isolation degradation associated with hostile environments and its effect on reuse, for both omnidirectional and directional antennas. Measurement results are reported on directivity distortion due to scattering by close-in buildings, median signal level variations with omnidirectional antennas, and lognormal shadowing characteristics in 'minicells'. Simulations of C/I (carrier/interference ratio) performance were performed using measured data, and results indicate that median signal level variations can degrade C/I by up to three times that caused by directivity distortion. >

Field tests have been performed in a high density urban environment to evaluate two important aspects of shadowing variability in land mobile radio links. These factors are the magnitude of variability and the rate at which variations decorrelate with time and spatial movement. The former was found to be significantly influenced by the size of the field test area. 1/e decorrelation times of the order of 15 s and decorrelation distances on the order of 100 m appear common.