Research On Key Characteristics Of FD-MIMO Technology In Next Generation Wireless Communication System

As the next generation of mobile communication standard,5G is an important research field in the area of wireless communication.Large-scale antenna technology is considered one of the core technologies of 5G communication system with the advantage of effectively improving the spectrum and energy efficiency of the system with limited spectrum resources. While the Full Dimension Multi-Input-Multi-Output (FD-MIMO) technology can make full use of the advatages of large-scale antenna. FD-MIMO technology extends the one-dimensional transmit antenna array in traditional MIMO systems to two-dimensional. The 2D antenna array can double the space utilization of base station and make full use of the spatial degree of freedom (DOF)in the vertical direction to achieve 3D beamforming, making the system coverage increase significantly at the same time. Currently, FD-MIMO has been listed as an important work item in 5G standard process of the Third Generation Partnership Project (3GPP).3GPP has basically completed the FD-MIMO wireless physical layer standard formulation, and the main purpose of this paper is to verify the RF performance of FD-MIMO system according the 3 GPP standard. The main research contents are as follows:1. The new features of FD-MIMO system are studied. Firstly, the transmission mode and precoding technique in traditional MIMO systems are analyzed. Then, the2D antenna configuration and channel correlation matrix of FD-MIMO are studied, the 3D channel model is completed, and the reporting process of CSI in MIMO system is analyzed. At last, a FD-MIMO downlink simulation platform based on the traditional LTE downlink system is established.2. Researched the application scenario of Non-precoded CSI-RS mode and beamformed CSI-RS mode respectively. For Non-precoded CSI-RS mode,3GPP has defined a new 2D precoding codebook corresponding the two-dimensional antenna array in FD-MIMO. In this paper, the structure of the new codebook is analyzed and the new codebook is implemented of the simulation platform. Second, as the number of CSI-RS ports is extended from 8 to 12 and 16, a new mapping scheme is designed for the extended CSI-RS in this paper. Then, the simulation platform of Non-precoded CSI-RS mode is established, and designed a test case to test the accuracy of CSI reporting. The simulation results verify that UE can reporte CSI accuratly under the new codebook and extended CSI-RS ports.3. For beamformed CSI-RS mode, the base station transmits a plurality of CSI-RS resources during one CSI-RS process and applys different beamforming scheme respectively. The number of CSI-RS resource groups larger than one or equal to one corresponds to two different scenarios. For the scenario of K larger than 1, the process of CSI-RS beamforming and the calculation method of CSI-RS resource indicator are designed in this paper. And verified the accuracy of CSI reporting according a test case. For the scenario of K equals 1, a single codebook feedback mode is supported. So new codebook for this mode is added to the simulation platform. Finally, a test case for CSI reporting is designed, and the simulation results show that UE can report CSI accurately with single codebook mode of beamformed CSI-RS.