Research On Massive MIMO Transmitter Beamforming Technology In Multipath Environment

Massive MIMO technology can improve the spectrum efficiency by utilizing the spatial multiplexing when communicating with terminals in different locations at the same time and frequency.This paper mainly focuses on the transmitter in the multi-node Massive MIMO system,the research works are as follow:(1)The problem is that sparse array pattern has a higher sidelobe when it obtains a narrower mainlobe width.A joint genetic algorithm and a convex optimization algorithm are proposed to optimize the sparse array pattern.It uses the genetic algorithm to determine the position of the array.Then it obtains the excitation vector of the array with the convex optimization algorithm.The simulation show that it enables the array pattern to have the desired mainlobe width and lower sidelobes in the specified direction.(2)In Massive MIMO system the estimation algorithm about inversion of matrix is considered when high dimensional channel matrix leads to the complex calculation with the inverse of RZF precoding matrix.Based on truncated Taylor series expansion,an amend RZF precoding algorithm is proposed for improving the accuracy of estimation.Through formula deduction,the parameters of the algorithm is derived by building the error model of the estimation matrix and the original matrix.The simulation show that in low signal noise ratio,the performance of the algorithm on system of bit error rate approximates the performance of the RZF precoding under the Rayleigh channel.(3)Spectral efficiency is affected by many factors in the multi-node Massive MIMO system with antenna correlation and multipath.When the antenna is correlated,this paper compares different precoding with equal power allocation.Then a power allocation algorithm is proposed to maximize the total spectral efficiency of the system when the transmission power is limited and the each node have a certain signal-to-interference.The simulation shows that the algorithm has a significant improvement in spectral efficiency compared with the average power allocation.In the Massive MIMO system with multipath channel,this paper establishes the multi-node Massive MIMO system model of SCM channel.The simulation shows that under the equal power allocation,the spectrum efficiency increases and the trend of increasing becomes slower when the number of antennas increases at the transmitter.