Regularized channel diagonalization for multiuser MIMO downlink using a modified MMSE criterion

We propose a regularized channel diagonalization method for a joint transmit-receive linear optimization in the downlink of a multiuser multiple-input multiple-output (MIMO) communication system. This method is based on the use of a modified minimum mean-square error (MMSE) criterion, which employs a weighted information symbol vector for the target and signal scaling. The weights for the target are the equivalent channel gain resulting from a zero-forcing (ZF)-based MIMO channel diagonalization. A joint iterative algorithm for minimizing the mean-square error (MSE) under a total transmit power constraint is derived, and its convergence is proved. The signal-to-interference-plus-noise ratio (SINR) is analyzed and the sum rates evaluated in a computer simulation. The results demonstrate that the proposed method outperforms the existing ZF- and MMSE-based methods.