  This paper introduces multiuser multiple-input multiple-output (MU-MIMO)
architectures based on non-linear precoding and stream combining techniques
using rate-splitting (RS), where the transmitter often has only partial
knowledge of the channel state information (CSI). In contrast to existing
works, we consider deployments where the receivers may be equipped with
multiple antennas. This allows us to employ linear combining techniques based
on the Min-Max, the maximum ratio and the minimum mean-square error criteria
along with Tomlinson-Harashima precoders (THP) for RS-based MU-MIMO systems to
enhance the sum-rate performance. Moreover, we incorporate the Multi-Branch
(MB) concept into the RS architecture to further improve the sum-rate
performance. Closed-form expressions for the signal-to-interference-plus-noise
ratio and the sum-rate at the receiver end are devised through statistical
analysis. Simulation results show that the proposed RS-THP schemes achieve
better performance than conventional linear and THP precoders.
