Research On Two-stage Precoding Technology For Large-scale MIMO

In today's Internet of everything,both the amount of data in mobile communication and the number of device connections in mobile communication are increasing rapidly.In order to meet the requirements of the increasing transmission rate and the number of device connections,a breakthrough must be made in the existing physical transmission technology.Massive multi input multi output(MIMO)technology can improve the spectrum efficiency and energy efficiency,so it can effectively solve the above problems.Through assembling a large number of antenna arrays on one side of the base station,and through a large number of antennas,multi-user terminals can be served at the same time with the same time and spectrum,so as to obtain higher spatial gain,spectral efficiency and system robustness.This paper focuses on the downlink transmission of the main MIMO system in FDD(frequency division duplex)mode,focusing on the application of two-stage precoding in single cell and multiple cell scenarios.Aiming at the problem of signal beam overlapping in user receiving terminal grouping,a scheduling scheme of user receiving terminal with overlapping degree quantization is designed to ensure the minimum of signal beam overlapping in each service group,so as to reduce the degree of signal beam overlapping and improve the performance of two-stage precoding.In order to select the optimal grouping,the degree of beam overlap is constructed into undirected weighted graph,and the user group grouping problem is transformed into the minimum weight edge selection problem.In addition,in multiple cell scenarios,in order to solve the overlapping interference of signal beams between different cells and reduce the system overhead,according to the difference of the environment of the user receiving terminal in the center area and the edge area of the cell,based on the two-stage precoding and interference alignment technology,a joint transmission scheme of multiple cells is designed.Because of the difference of interference environment,channel link characteristic space rank and signal strength,each cell is divided into center part and edge part.For the user receiving terminal in the central area,because it is far away from the transmitting terminal base station in other cells,the signal interference from the user receiving terminal in other cells is small and can be ignored.JSDM(joint space division multiplexing)scheme is used to eliminate the signal interference between groups in the cell.JSDM is used to reduce the dimension of the equivalent channel link matrix,and then interference alignment technology is used to improve the transmission performance of the user receiving terminals at the cell edge.