Research On The Limited Feedback Mechanism Of Massive MIMO Systems

The Massive Multiple-Input Multiple-Output system serves multiple users simultaneously by configuring an antenna array consisting of a large number of antennas at the transmitter side.Large antenna arrays can bring significant array gain through coherent beamforming and low complexity preprocessing algorithm,which can significantly improve spectrum efficiency and user rate while reducing transmission power consumption.In order to achieve optimal performance of Massive MIMO system,the base station requires the channel state information.However,the increasing number of antennas and users also greatly increases the feedback overhead which limits the overall performance of the system.Therefore,how to reduce the feedback overhead and improve the transmission performance of transmitter has research value.First,in Massive MIMO-OFDM system,based on principal component analysis in the process of feedback channel,in the actual calculation channel vector covariance matrix,the computational complexity becomes unacceptable because of the increasing number of antennas and the subcarrier.We propose a feedback channel scheme based on two-directions principal component analysis to solve this problem.The simulation results show that the feedback scheme presented in this paper has lower complexity than the traditional Principal Component Analysis(PCA)channel feedback and better compression performance.At the same time,a bit allocation algorithm which can effectively reduce the feedback overhead is also proposed for the proposed feedback scheme.Secondly,for the precoder feedback scheme based on Channel State Information(CSI)sharing,the precoder vector quantization error will cause leakage interference and reduce the sum rate.We proposed a differential precoding feedback scheme based on CSI sharing.The proposed scheme utilizes the time correlation of the channel,which can effectively reduce the feedback overhead,and reduces the leakage interference caused by modifying precoding vector.The simulation results show that the proposed scheme can greatly reduce the feedback overhead and improve the sum rate.