3D MIMO系统下水平和垂直维联合预编码的研究

第五代(5G)移动通信网络将会在很大程度上提高无线通信的速率。由于多入多出系统(MIMO)能够满足5G网络中对信息速率越来越高的要求，现在正受到广泛的关注。然而，传统意义的二维(2D)MIMO技术仅仅能控制水平维的波束。为了满足5G的需求，需要引入能同时考虑水平维和垂直维波束的三维(3D)MIMO技术。本文基于3D MIMO信道模型，在分析3D MIMO信道相关性的基础上，针对发射相关和接收相关矩阵在水平维和垂直维的分解，提出了一种利用3D MIMO信道相关性的有限反馈预编码方案。并在此基础上，结合2D MIMO信道下的DFT码本和Grassmannian码本，提出了两种新的3D MIMO信道下的码本。实验结果表明，提出的3D MIMO预编码方案整体性能优于传统2D MIMO和现有的3D MIMO预编码方案。在3D MIMO系统中，由于可以动态调节天线的下倾角，故充分发掘了空间三维自由度。3D MIMO预编码技术减小小区间干扰，增加了系统容量，有效地提高了整个通信系统的性能。 

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.