I. Introduction
In modern wireless communication systems, the presence of channel state information (CSI) at the transmitter enables link adaptation, multi-user scheduling, beamforming, spatial multiplexing, space division multiple access, and coordinated multipoint transmission. Delays in the feedback control loop cause outdating of the CSI when transmitting to a moving vehicle. This problem becomes increasingly severe with larger delays, higher vehicle velocities, and shorter carrier wave-lengths. Prediction based on past received channel estimates by Kalman or Wiener prediction can to some extent alleviate the problem [1]. However, these methods become inadequate in multipath fading environments when the required prediction horizon in time corresponds to a movement of more than 0.3 carrier wavelengths in space. For high mobility users, this limitation prevents accurate CSI to be obtained in the current 3GPP Long Term Evolution (LTE) systems with carrier frequencies exceeding 1 GHz [2].