Figure 2

Displays the BER curves versus the SNR, i.e., $1∕{\sigma }_n^2$ , of the considered ZF beamform-ing scheme, i.e., the multi-user (MU) scenario, with N _t = 2 ( continuous red line with the marker x), N _t = 3 ( continuous green line with the marker o ) and N _t = 4 ( continuous magenta line with the marker Δ ) assuming perfect frequency synchronization and for a 16 QAM modulation scheme. We can observe that the diversity order of the proposed distributed schemes increases with the number of transmit antennas, matching the derivations proposed in Section 3.2. The BER curves of a single-user (SU) system with transmit-MRC beamforming and N _t = 2 (continuous blue line) and N _t = 4 (dashed black line) are also displayed.