A simple method of transmitting stream adaptation for fixed-matrix-size precoding on MU-MIMO transmission

During the operation of multiuser multiple-input-multiple output (MU-MIMO) algorithms, some antennas of BS or UEs may neither transmit nor receive signals due to the long distance or unexpected damages. Therefore, the BS cannot obtain the channel state information (CSI) from/to these antennas. Without these CSI, the performance of algorithm is degraded. We call this effect as `broken antenna effect (BAE)´. To cope with this issue, this paper proposes a process to regularize the channel matrix by replacing the missing CSI with zero(s) and setting nonzero values to diagonal elements. Then, it is confirmed through computer simulation that the proposed method can adjust the number of transmitting parallel streams according to the number of `broken´ antennas, and provide MU-MIMO transmission with maximum diversity order without any change of the precoding process.