Research On Joint Spatial Division And Multiplexing In Massive MIMO Systems

Massive MIMO technology can greatly improve spectrum efficiency and system capacity. It has become one of the promising technologies for future mobile communication systems. The base station usually uses downlink precoding technique to eliminate the interference between different users, in order to improve the system performance. The premise of downlink precoding processing is that the base station can obtain downlink channel state information (CSI). Joint Spatial Division Multiplexing method (JSDM) can take advantage of the spatial channel correlation to significantly reduce the overhead for CSI acquisition. This thesis mainly address the downlink transmission scheme of the Massive MIMO system operating in frequency-division duplex (FDD) mode, focusing on JSDM applications and optimization.Firstly, the basis for Massive MIMO transmission technology are summarized, which include the basic model of MIMO systems and linear precoding algorithms for multiuser MIMO systems. Besides, typical MIMO channel models including physical channel models and statistical channel models are introduced.Then, the system model and the transmission scheme of JSDM is described, after which, we analyzed the performance of JSDM scheme through simulations and studied the parameter optimization problem in JSDM transmission scheme.Subsequently, we study the optimization methods for JSDM scheme applied in the complex scattering environment. We designed appropriate JSDM transmission scheme for complex scattering scenes, especially focusing on the problem of inter-group channel orthogonalization, for which, a solution based on genetic algorithm is proposed. Simulation results show that the proposed transmission scheme that can perform well in complex scattering environment.Finally, we extend the JSDM scheme to the 3D-SCM model, which is based on the 3GPP SCM model. A simplified JSDM method is proposed and demonstrated for 3D channel. Besides, we proposed a user grouping mechanism based on receive beamforming. Simulations show that the above schemes perform well.