  Precoding with block diagonalization is an attractive scheme for approaching
sum capacity in multiuser multiple input multiple output (MIMO) broadcast
channels. This method requires either global channel state information at every
receiver or an additional training phase, which demands additional system
planning. In this paper we propose a lattice based multi-user precoder that
uses block diagonalization combined with pre-equalization and perturbation for
the multiuser MIMO broadcast channel. An achievable sum rate of the proposed
scheme is derived and used to show that the proposed technique approaches the
achievable sum rate of block diagonalization with water-filling but does not
require the additional information at the receiver. Monte Carlo simulations
with equal power allocation show that the proposed method provides better bit
error rate and diversity performance than block diagonalization with a
zero-forcing receiver. Additionally, the proposed method shows similar
performance to the maximum likelihood receiver but with much lower receiver
complexity.
