Research Of Multi-user MIMO Technology In LTE/LTE-Advanced System

With the development of mobile communication, LTE/LTE-Advanced system attracts more and more attention. As a kind of technology which can effectively improve the reliability of data transmission and the transmission rate, MIMO is applied in different communication systems widely. Combining with LTE/LTE-Advanced system, this paper studies the Multi-user MIMO technology.First,this paper gives a research on MIMO channel capacity.According to the simulation results,it can be found that the Channel State Information(CSI) can help to improve channel capacity effectively.When the CSI is known,the channel capacity is greater than that when CSI is unknown,this happenes on condition that the SNR is low.If the SNR is much higher,the access to CSI can not help to improve channel capacity.Then this paper gives a research on precoding algorithm of LTE system. Different precoding algorithms are studied,such as the forced zero precoding, MMSE precoding, Block Diagonalization precoding, Dirty Paper Coding (DPC) and THP precoding.The simulation of the BER property shows that linear MMSE algorithm is superior to ZF algorithm. And in nonlinear precoding methods, the MMSE-THP precoding algorithm is superior to ZF-THP algorithm. DPC precoding algorithm can gain maximum capacity, but its realization is much more complex.According to the advantages and disadvantages of different precoding algorithms, this paper proposes a new idea to combine the linear and nonlinear precoding algorithm in practical application. Based on the above research, this paper studies the CoMP-MU-MIMO joint precoding scheme, which mainly analyses the cooperative transmission in different cell controlled by only one eNodeB; Through the simulation results, it can be found that the joint precoding scheme can improve communication quality effectively, especially to those users that are at the edge of the cell; The scheme can reduce inter-user interference obviously,which improves the reliability of the total communication system at the same time.This paper gives a reaearch on MIMO technology of LTE/LTE-Advanced system, which mainly studies MU-MIMO technology. The research results provide a theoretical reference for the design of communication system.