Improved MMSE Vector Precoding Based on the MBER Criterion

A novel vector precoding scheme is proposed for the downlink of a multiuser system equipped with multiple antennas transmitting to single-antenna aided mobile receivers. Our transmit preprocessing scheme first invokes a regularized channel inversion and then superimposes a perturbation vector to directly minimize the bit error ratio (BER) of the system as an improvement to the well-known minimum mean-square-error (MMSE) vector precoding scheme. Our simulation results demonstrate that the proposed vector precoding scheme achieves the same BER performance as the MMSE vector precoding at the same complexity, when only discrete vector perturbations are allowed. However, the performance of the proposed vector precoding scheme can be further improved based on the MBER criterion, when continuous-valued vector perturbations are carried out.