Geometrical modeling of non-stationary double-Rayleigh fading channels for MIMO vehicle-to-vehicle communications

In this paper, we present a channel model that characterizes the non-stationarities of small-scale multipleinput multiple-output (MIMO) vehicle-to-vehicle (V2V) double-Rayleigh fading channels that arise from the temporal variations of the propagation delays. The analysis of the correlation properties of the proposed channel model is the main objetive of our paper. To achieve this goal, we derive an analytical expression for the space-time-frequency cross-correlation function (STF-CCF) following a geometrical plane-wave propagation (PWP) framework. An important feature of this expression is that it does not depend on a particular arrangement of the interfering objects (IOs) in the propagation scenario. Furthermore, a closedform expression of the STF-CCF is derived for the particular case of the geometrical two-rings model. The analytical and simulation results show that the elements of the MIMO channel matrix are non-wide-sense stationary (non-WSS) random processes both in the time and the frequency domains, as well as pairwise jointly non-WSS both in the time and the frequency domains.