Modeling of Highly Non-Stationary Low Altitude Aircraft-to-Aircraft Channels

Due to the high velocity and low altitude of combat sorties the aircraft-to-aircraft communication channel becomes highly non-stationary. Nowadays, however, there are still many channel models based on the wide-sense stationary uncorrelated scattering assumption. This assumption breaks down for most military aircraft-to-aircraft channels. In order to include the nonstationarity into the channel model, we use a time-variant, delay-dependent description of the Doppler frequency. The model is based on a geometric-stochastic channel model. By using the aircraft geometry, the non-stationarities are naturally included into the model. Due to the fact that we employ a delay-dependent description of the Doppler frequency, the model becomes wideband. The surfaces of constant delays are ellipsoids with the aircraft in its foci. Thus, a channel description in a prolate spheroidal coordinate system is used to simplify the mathematical notation. We show the delay-dependent Doppler probability density function and its corresponding characteristic function for practical low altitude scenarios.