A relatively recent idea of extending the benefits of
MIMO systems to multi-user scenarios seems promising in the
context of achieving high data rates envisioned for future cellular
standards after 3G (3rd Generation). Although substantial
research has been done on the theoretical front, recent focus
is on making Multi-User Multiple-Input Multiple-Output (MUMIMO)
practically realizable. This article presents an overview
of the different MU-MIMO schemes included / being studied
in 3GPP standardization; from LTE (Long Term Evolution) to
LTE-Advanced. MU-MIMO system concepts and implementation
aspects have been studied here. Various low-complexity receiver
architectures are investigated and their performance assessed
through link-level simulations. Appealing performance offered
by low-complexity interference aware (IA) receivers is notably
emphasized. Furthermore, system level simulations for LTE
Release 8 are provided. Interestingly, it is shown that MU-MIMO
only offers marginal performance gains with respect to singleuser
MIMO. This arises from the limited MU-MIMO features
included in Release 8 and calls for improved schemes for the
upcoming releases.
