Sum-rate Maximization in Sub-28 GHz Millimeter-Wave MIMO Interfering Networks

TL;DR

This paper introduces fast-converging algorithms for sum-rate maximization in sub-28 GHz millimeter-wave MIMO networks, effectively managing interference despite limited directivity and short channel coherence times.

Contribution

It proposes the max-DLT algorithm with a derived lower bound, non-homogeneous waterfilling solutions, and demonstrates their fast convergence and effectiveness in interference-limited millimeter-wave networks.

Findings

The max-DLT algorithm converges rapidly to a stationary point.

The proposed methods outperform traditional approaches in dense networks.

Interference management yields significant performance gains in low-bandwidth millimeter-wave systems.

Abstract

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.