  An asymptotic technique is presented for finding the spectral efficiency of
multi-antenna links in wireless networks where transmitters have
Channel-State-Information (CSI) corresponding to their target receiver.
Transmitters are assumed to transmit independent data streams on a limited
number of channel modes which limits the rank of transmit covariance matrices.
This technique is applied to spatially distributed networks to derive an
approximation for the asymptotic spectral efficiency in the
interference-limited regime as a function of link-length, interferer density,
number of antennas per receiver and transmitter, number of transmit streams and
path-loss exponent. It is found that targeted-receiver CSI, which can be
acquired with low overhead in duplex systems with reciprocity, can increase
spectral efficiency several fold, particularly when link lengths are large,
node density is high or both. Additionally, the per-link spectral efficiency is
found to be a function of the ratio of node density to the number of receiver
antennas, and that it can often be improved if nodes transmit using fewer
streams. These results are validated for finite-sized systems by Monte-Carlo
simulation and are asymptotic in the regime where the number of users and
antennas per receiver approach infinity.
