Approximate channel block diagonalization for open-loop Multiuser MIMO communications

This paper proposes an approximate block diagonalization (BD) method that does not require feedback of channel state information (CSI) by using the second-order statistics of channels for multiuser MIMO mobile communications. On the assumption that an incidence angle (angle-of-arrival) distribution in the uplink channel is the same as an angle-of-departure distribution in the downlink channel, the proposed scheme estimates the autocorrelation matrix of the downlink channel from the average and variance of incidence angles in the uplink. Since the proposed scheme uses the estimate of the autocorrelation matrix of the downlink channel, it performs eigenvalue decomposition of the estimated autocorrelation matrix whereas the conventional BD precoding performs singular value decomposition of the channel matrix. To verify the effectiveness of the proposed scheme, computer simulations are conducted. It is shown that the proposed scheme, which does not need CSI feedback, is little inferior in the channel capacity to the conventional BD precoding that requires CSI feedback.