  The fundamental challenge of the millimeter-wave (mmWave) frequency band is
the sensitivity of the radio channel to blockages, which gives rise to unstable
connectivity and impacts the reliability of a system. To this end, multi-point
connectivity is a promising approach for ensuring the desired rate and
reliability requirements. A robust beamformer design is proposed to improve the
communication reliability by exploiting the spatial macro-diversity and a
pessimistic estimate of rates over potential link blockage combinations.
Specifically, we provide a blockage-aware algorithm for the weighted sum-rate
maximization (WSRM) problem with parallel beamformer processing across
distributed remote radio units (RRUs). Combinations of non-convex and coupled
constraints are handled via successive convex approximation (SCA) framework,
which admits a closed-form solution for each SCA step, by solving a system of
Karush-Kuhn-Tucker (KKT) optimality conditions. Unlike the conventional
coordinated multi-point (CoMP) schemes, the proposed blockage-aware beamformer
design has, per-iteration, computational complexity in the order of RRU
antennas instead of system-wide joint transmit antennas. This leads to a
practical and computationally efficient implementation that is scalable to any
arbitrary multi-point configuration. In the presence of random blockages, the
proposed schemes are shown to significantly outperform baseline scenarios and
result in reliable mmWave communication.
