Research on Joint Precoding of Horizontal and Vertical Dimension in 3D MIMO System

The fifth generation (5G) mobile communication networks will greatly increase the data-rate of wireless communication. Multiple-input multiple-output (MIMO) system has drawn more and more attentions as it meets the increasing demands in 5G mobile networks. However, traditional two-dimensional (2D) MIMO technologies can only control the beamformers in the azimuth dimension. To meet the demand of 5G, three-dimension (3D) MIMO technology is proposed, which takes into account the azimuth and elevation directions. Based on 3D MIMO channel model, the correlation of 3D MIMO channel is analyzed. For the correlation matrixes of transmitter and receiver can be separated in the azimuth and elevation dimensions, a precoding scheme of limited feedback using the correlation matrixs is proposed in this paper. Based on the improved scheme, we propose two new 3D MIMO codebooks combining with the DFT and Grassmannian codebooks in 2D MIMO channel. Simulation results show that the proposed 3D MIMO precoding scheme outperforms the traditional 2D and the exiting 3D MIMO precoding schemes. Owing to the dynamic downtilt adjustment, 3D MIMO system fully explores the 3D space degrees of freedom. Our 3D MIMO precoding scheme can reduce the inter-cell interference, increase the system capacity and effectively improve the overall system performance.