Modeling Interference Effects for Land-Mobile and Air-Mobile Communications

Analytic and computer models are presented that can provide an assessment of land-mobile and air-mobile communications performance in interference environments. The results obtained with these models, based on a communications region of operability criterion, include the effects of greater-than-free-space propagation path losses associated with low-elevation signal paths. The analytic models are used to examine the effects of higher order path loss on signal-to-interference contours for single and linearly distributed interference scenarios. The computer model can be used to investigate link performance for interference environments in which the link assets and each source of interference are arbitrarily located in three dimensions. A propagation submodel permits independent calculation of the loss over each link or interference signal path. Computer-generated plots are presented that illustrate the effect of antenna heights and frequency on the shape of the signal-to-interference (S/I) contours. Of particular interest is the effect on link region of operability when either the link transmitter or the sources of interference are at a higher altitude than the other.