Channel Estimation with Space-Time Windowing in MIMO PE-SDM Transmission

In a frequency-selective MIMO channel, the optimum beamforming is achieved by using eigenvectors, i.e., eigenbeam-space division multiplexing (E-SDM), in the frequency domain. However, the calculation load of eigenvalue decomposition increases in proportion to the number of FFT points. In addition, eigenvectors without consideration of frequency continuity increase the delay spread of the effective channel observed at the receiver. To solve these issues, a pseudo eigenvector technique has been proposed. It has also been reported that a pseudo E-SDM (PE-SDM) technique can provide almost the same or better performance compared with the E-SDM when the receiver employs a simple channel estimator with time windowing. In this paper, focusing on the calculating process of pseudo eigenvectors, we propose a spatial windowing scheme improving the accuracy of the effective channel estimates. The simulation results show that the accuracy in the PE-SDM can be improved by combining the proposed scheme with the conventional time windowing scheme.