  Traditional approaches in the analysis of downlink systems decouple the
precoding and the channel estimation problems. However, in cellular systems
with mobile users, these two problems are in fact tightly coupled. In this
paper, this coupling is explicitly studied by accounting for channel training
overhead and estimation error while determining the overall system throughput.
The paper studies the problem of utilizing imperfect channel estimates for
efficient linear precoding and user selection. It presents precoding methods
that take into account the degree of channel estimation error.
Information-theoretic lower and upper bounds are derived to evaluate the
performance of these precoding methods. In typical scenarios, these bounds are
close.
