  Low-complexity precoding {algorithms} are proposed in this work to reduce the
computational complexity and improve the performance of regularized block
diagonalization (RBD) {based} precoding {schemes} for large multi-user {MIMO}
(MU-MIMO) systems. The proposed algorithms are based on a channel inversion
technique, QR decompositions{,} and lattice reductions to decouple the MU-MIMO
channel into equivalent SU-MIMO channels. Simulation results show that the
proposed precoding algorithms can achieve almost the same sum-rate performance
as RBD precoding, substantial bit error rate (BER) performance gains{,} and a
simplified receiver structure, while requiring a lower complexity.
