Research On Precoding Method In Millimeter Wave MIMO System

With the development of society,people have higher requirements for the speed and stability of data transmission in communication systems.Millimeter wave is widely concerned because it can provide rich spectrum resources,but its physical characteristics determine that it needs to be combined with MIMO(multiple input and multiple output)technology to provide better service,but the corresponding precoding technology is also needed to improve the quality of transmission link.Considering the hardware constraints and channel sparsity of millimeter wave systems,hybrid precoding has become one of the main technologies of millimeter wave communication systems.This paper first introduces various commonly used nonlinear precoding and Linear Precoding techniques,and analyzes the effects of different precoding techniques on system performance.The principle of the hybrid precoding algorithm based on OMP is introduced in detail,and the simulation analysis is given on the basis of considering how to get better system performance.A mixed precoding algorithm based on iterated least mean square error is proposed for fully connected structures.The algorithm takes the spectral efficiency of the ideal pure digital precoding as a reference,and aims at minimizing the mean square difference between the transmitted and received signals,and iteratively updates the two level of the hybrid precoding structure by assuming an equivalent precoding matrix.Compared with the traditional precoding algorithm,the influence of the precoding matrix of the transmitter and the merging matrix of the receiver is taken into consideration.On the premise of minimizing the mean square error of the signal between the transmitted signal and the received signal,the two stage system is alternately updated and gradually tends to the optimal design,thus improving the spectrum efficiency of the system.Then,on the basis of performance optimization and considering the actual hardware cost,a hybrid precoding algorithm with low computational complexity is proposed.Simulation results show that the algorithm is superior to other precoding algorithms in terms of computational complexity.Finally,we try to improve the algorithm from the reconfiguration of the combiner,and simulate and verify the performance of the algorithm in different reconstruction directions.