Randomly-Directional Beamforming in Millimeter-Wave Multiuser MISO Downlink

Abstract

In this paper, the performance of opportunistic random beamforming (RBF) and the multiuser (MU) gain in millimeter-wave (mm-wave) MU multiple-input single-output (MISO) downlink systems are analyzed based on the uniform random single-path (UR-SP) channel model suitable for highly directional mm-wave radio propagation channels. It is shown that under the UR-SP channel model, RBF achieves linear sum rate scaling with respect to (w.r.t.) the number of transmit antennas and, furthermore, yields optimal sum rate performance when the number of transmit antennas is large, if the number of users increases linearly w.r.t. the number of transmit antennas. Several beam training and user selection methods are investigated to yield insights into the most effective beamforming and scheduling choice for mm-wave MU-MISO in various operating conditions. Simulation results validate our analysis based on asymptotic techniques for finite cases.