Impact of 3D-BF against the Number of Picocell Sector in mmWave HetNets

Three-dimensional beamforming (3D-BF) is a promising technique to improve the received SINR or extend cell coverage in mobile systems. Heterogeneous networks (HetNets) with picocells operating at millimeter wave (mmWave) band are expected to achieve higher user throughput because of the enormous amount of signal bandwidth in 5G mobile systems and beyond. This paper discusses the impact of 3D-BF against the number of picocell sector in mmWave HetNets. The average and 5-percentile user throughput are clarified for five types of picocells as parameters of Tx beams used in 3D-BF, using system-level computer simulations. We confirmed that six-sector picocell using 3D-BF with 18 Tx beams can improve the average user throughput by approximate 1.4 times compared with three-sector picocell using 3D-BF with 36 Tx beams. We also clarified that the 3D-BF applied to picocells can increase the use rate of high-order modulation such as 1024-QAM in mmWave HetNets.