  Cell densification is a key driver to increase area spectral efficiencies in
multi-antenna cellular systems. As increasing the densities of base stations
(BSs) and users that share the same spectrum, however, both
inter-user-interference (IUI) and inter-cell interference (ICI) problems give
rise to a significant loss in spectral efficiencies in such systems. To resolve
this problem under the constraint of local channel state information per BS, in
this paper, we present a novel noncooperative multi-user multiple-input
multiple-output (MIMO) precoding technique, called
signal-to-interference-pulse-leakage-pulse-noise-ratio (SILNR) maximization
precoding. The key innovation of our distributed precoding method is to
maximize the product of SILNRs of users per cell using local channel state
information at the transmitter (CSIT). We show that our precoding technique
only using local CSIT can asymptotically achieve the multi-cell cooperative
bound attained by cooperative precoding using global CSIT in some cases. We
also present a precoding algorithm that is robust to CSIT errors in multi-cell
scenarios. By multi-cell system-level simulations, we demonstrate that our
distributed precoding technique outperforms all existing noncooperative
precoding methods considerably and can also achieve the multi-cell bound very
tightly even with not-so-many antennas at BSs.
