Modelling of Non-WSSUS Channels with Time-Variant Doppler and Delay Characteristics

This paper deals with the modelling of non-wide-sense stationary uncorrelated scattering (non-WSSUS) channels in which the angles of arrival (AOAs), Doppler frequencies, and propagation delays vary with time. Starting from a geometrical model in which the mobile station (MS) travels along a predefined path with time-variant velocity, it is shown how the parameters of the non-WSSUS model can be computed analytically assuming that the scatterers are fixed. One of the key results of our analysis is that the time-variant Doppler frequencies and the time-variant propagation delays of WSSUS and non-WSSUS channels are connected by a fundamental relationship. Furthermore, the time-variant channel transfer function of the non-WSSUS channel model is derived. In addition, general expressions are presented for the correlation functions in the time and frequency domains. Moreover, it is shown that the proposed non-WSSUS channel model is consistent w.r.t. the mean Doppler shift, Doppler spread, mean propagation delay, and delay spread. The proposed concept is of fundamental importance for the design of physically sound wideband channel models under non-stationary propagation conditions.