Research On Precoding Of Wireless Massive MIMO System

With the rapid development of mobile communication technologies,wireless data traffic is showing exponential growth.Spectral efficiency and energy efficiency become two important metrics for the development of future wireless communication networks.As a candidate technology in future 5G networks,Massive MIMO can provide high energy efficiency and spectral efficiency.Thus,it has attracted widespread interest from both academia and industry.Therefore,we study the following three aspects of massive MIMO:Firstly,key technologies of massive MIMO are introduced as a basis for subsequent study,which involve precoding,channel estimate and the joint application of 3D MIMO and massive MIMO.Then the linear precoding algorithms in single cell systems are introduced.We also derive the asymptotic performances of ZF(Zero Forcing)precoding algorithm and DPC(Dirty Paper Coding)in massive MIMO systems.Secondly,we concentrate on the downlink multicell multiuser 3D massive MIMO communication system employing ZF precoder with tilt angle at the base station.And we propose novel closed-form expressions of the achievable data rate and outage probability.Then we investigate the effect of base station antenna tilt angle on system performance.As the simulation results show,the tilt angle of the base station should be designed especially for the cell edge users.It is because the inappropriate tilt angle design can decay the performance of the system which can be worse than the system without tilt angle at the base station.Thirdly,we focus on the decentralized cooperative precoding schemes in massive MIMO systems and the optimization objective is energy efficiency.We study the convergence performance,the effects of maximum power constraints,circuit power consumption and the number of serving users on the system energy efficiency.Meanwhile,we compare the proposed algorithm with decentralized precoding algorithms.