BER versus SRxNR with MIMO LP over measured indoor channels. Figure 8 shows the uncoded BER with respect to the SRxNR. A MIMO system with four transmit antennas and four receive antennas (Nt = Nr = 4) is considered. The performance evaluation is carried out considering LP for ZF as well as MMSE, while all schemes are evaluated with and without Tx-noise. Finally, schemes specifically designed to deal with Tx-noise (labeled as "modified") are also evaluated. In all cases, QPSK signals over measured indoor channels are used, whereas the estimated STxNR is about 25 dB.