Abstract:

The fading process in high speed vehicular traffic telematic applications at 5 GHz is expected to fulfill the wide-sense stationarity uncorrelated scattering (WSSUS) assumptions for very short time-intervals only. In order to test this assumption we apply the concept of a local time-and frequency-variant scattering function, which we estimate from measurements of vehicle-to-vehicle wave propagation channels by means of a multi-window spectrogram. The obtained temporal sequence of local scattering functions (LSF) is used to calculate a collinearity measure. We define the stationarity time as the support of the region where the collinearity exceeds a certain threshold. The stationarity time is the maximum time duration over which the WSSUS assumption is valid. Measurements from a highway with vehicles driving in opposite directions show stationarity times as small as 23 ms whereas vehicles driving in the same direction show stationarity times of 1479 ms.