  MIMO systems in the lower part of the millimeter-wave spectrum band (i.e.,
below 28 GHz) do not exhibit enough directivity and selectively, as their
counterparts in higher bands of the spectrum (i.e., above 60 GHz), and thus
still suffer from the detrimental effect of interference, on the system
sum-rate. As such systems exhibit large numbers of antennas and short coherence
times for the channel, traditional methods of distributed coordination are
ill-suited, and the resulting communication overhead would offset the gains of
coordination. In this work, we propose algorithms for tackling the sum-rate
maximization problem, that are designed to address the above limitations. We
derive a lower bound on the sum-rate, a so-called DLT bound (i.e., a difference
of log and trace), shed light on its tightness, and highlight its decoupled
nature at both the transmitters and receivers. Moreover, we derive the solution
to each of the subproblems, that we dub non-homogeneous waterfilling (a
variation on the MIMO waterfilling solution), and underline an inherent
desirable feature: its ability to turn-off streams exhibiting low-SINR, and
contribute to greatly speeding up the convergence of the proposed algorithm. We
then show the convergence of the resulting algorithm, max-DLT, to a stationary
point of the DLT bound. Finally, we rely on extensive simulations of various
network configurations, to establish the fast-converging nature of our proposed
schemes, and thus their suitability for addressing the short coherence
interval, as well as the increased system dimensions, arising when managing
interference in lower bands of the millimeter wave spectrum. Moreover, our
results also suggest that interference management still brings about
significant performance gains, especially in dense deployments.
