Blockwise-Lattice-Reduction aided precoders for multiuser MIMO with clusters of correlated users

This paper presents a new class of Blockwise-Lattice-Reduction (BLR) aided Tomlinson-Harashima precoders (BLR-THPs) for multiuser multiple-input-multiple-output (MU-MIMO) downlink communications with clusters of correlated channels. The proposed BLR-THPs take the clustering information into account by first decoupling the overall downlink channel into multiple subchannels (one for each cluster) before applying the lattice-reduction technique to each subchannel. In comparison to the conventional LR-THPs, the proposed BLR-THPs require much lower complexity as the computationally intensive LR procedure in the LR-THPs is now effectively approximated by multiple LR procedures with much lower dimensionality. We present a number of new precoders that belong to this class and then compared them with the existing THPs with or without LR through extensive computer simulations.