Optimization of downtilts adjustment combining joint transmission and 3D beamforming in 3D MIMO

This paper mainly proposes a downtilts adjustment scheme combining joint transmission (JT) and 3-dimension (3D) beamforming in 3D multiple-input multiple-output (MIMO) communication systems, under the new typical scenario in the 3rd generation partnership project (3GPP) which is defined as urban macro cell with one high-rise per sector (3D UMa-H). In our proposed scheme, the specific downtilts adjustment for cellcenter users and cell-edge users are realized through dynamic vertical beamforming. Moreover, the cell-center users are served by 3D beamforming, while the cell-edge users are served by JT and 3D beamforming, which facilitate to maximize both cell-center users' and cell-edge users' throughput. To achieve accurate performance evaluation, 3D spatial channel model (3D SCM) and 2-dimension (2D) planar antenna array structure are also considered in our system-level simulation. Simulation results show that our proposed scheme can achieve about 35% gain on cell average spectral efficiency and 42% gain on cell edge user spectral efficiency compared to traditional 2D MIMO without JT.