  We address the problem of the bit error rate (BER) performance gap between
the sub-optimal and optimal linear precoder (LP) for a multiuser (MU) multiple
input and multiple output (MIMO) broadcast systems in this paper. Particularly,
mobile users suffer noise enhancement effect due to a sub-optimal LP that can
be suppressed by an optimal LP matrix. A sub-optimal LP matrix such as a linear
zero-forcing (LZF) precoder performs in high signal to noise ratio (SNR) regime
only, in contrast, an optimal precoder for instance a linear minimum
mean-square-error (LMMSE) precoder outperforms in both low and high SNR
scenarios. These kinds of precoder illustrates the BER gap distance at least
0.1 when it is used in itself in a MU MIMO systems. Thus, we propose and design
a unified linear precoding (ULP) matrix using a precoding selection technique
that combines the sub-optimal and optimal LP matrix for a multi-user MIMO
systems to ensure zero BER performance gap in this paper. The numerical results
show that our proposed ULP technique offers significant performance in both low
and high SNR scenarios.
