Using Real Constellations in Fully- and Over-Loaded Large MU-MIMO Systems With Simple Detection

The aim of this letter is to exhibit some advantages of using real constellations in large multiuser (MU) MIMO systems. It is shown that a widely linear zero-forcing (WLZF) receiver with M-ASK modulation enjoys a spatial-domain diversity gain, which linearly increases with the MIMO size even in fully- and over-loaded systems. Using the decision of WLZF as the initial state, the likelihood ascent search (LAS) achieves near-optimal BER performance in fully loaded large MIMO systems. Interestingly, for coded systems, WLZF shows a much closer BER to that of WLZF-LAS with a gap of only 0.9-2 dB in SNR.