MU-MIMO is widely considered a key technology

for system capacity improvement in modern

wireless networks. In contrast to

SU-MIMO, where the spatial multiplexing gain

is confined to a single user, MU-MIMO allows

multiple users to be co-scheduled on the same

time-frequency resources to exploit this gain

among two or more UE units. This is particularly

beneficial as high-rank SU-MIMO transmission

is often limited by the number of

antennas and antenna design constraints at the

user end, whereas high-rank transmission using

MU-MIMO is more feasible due to the scattered

user distribution.

It is well known that the information theoretic

optimal MU-MIMO scheme is dirty paper

coding (DPC), which unfortunately is a nonlinear/

non-causal beamforming scheme and therefore

unrealistic in real-life applications. From a

practical deployment point of view, the most