Study On Massive MIMO-Based Millimeter Wave Of Wireless Communication System

At present,mankind has an urgent pursuit of connectivity and transmission rates in communication technology.Obviously 4G can not meet these requirements,therefore 5G key technologies have become a hot spot for research.Meanwhile,Massive-MIMO technology combined with millimeter-wave frequency band has become one of the key technologies of 5G.The short wavelength of the millimeter wave makes the size of the antenna smaller,which is good for the use of a large-scale antenna array.However,the use of large-scale MIMO can effectively increase the array gain and reduce the serious problem of the millimeter wave fading in the space.It can be seen that the two are mu-tually reinforcing and provide a powerful impetus for the upcoming 5G technology.Therefore,the combination of the two effectively improves the system capacity and spectrum resource utilization,and the application of the millimeter wave effectively solves the problem of the antenna size and the antenna spatial correlation.However,millimeter wave technology is still in its infancy in many aspects,especially in terms of channel model,channel estimation,antenna array distribution structure and hybrid precoding.Block diagonalization(BD)-based hybrid precoding in multi-user systems is ana-lyzed and a hybrid precoding based on the iteration algorithm of analog domain is pro-posed in this paper.For BD-based hybrid precoding,the spectrum efficiency with the changes of signal-noise ratio,number of data streams and number of users are simulated separately,the simulation comparison between the millimeter-wave channel and Ray-leigh channel is performed,and the uniform linear and uniform planar arrays are simu-lated and analyzed.The simulation results show that the BD-based hybrid precoding saves the hardware equipment and power loss while the spectral efficiency of the sys-tem approaches or exceeds the full digital precoding.For hybrid precoding based on the analog domain iterative algorithm,the three precoding schemes of MRT,ZF and BD are respectively used in the digital domain.The simulation results show that the MRT per-formance of the three digital precoding schemes is better under small SNR and the BD algorithm is better under medium-high SNR.When using only the iterative algorithm in the analog domain,the performance is similar to the optimal case.Millimeter-Wave Massive MIMO systems employing centralized and distributed antenna structures are researched in this article.The centralized and distributed lower diversity gain formulas are derived,showing the potential for linear increase in the di-versity compared to a centralized diversity gain or multiplexing gain.Then the spectral efficiency of millimeter-wave massive MIMO distributed and centralized systems is simulated and compared.In the single-user system,a hybrid precoding method based on the orthogonal matching filtering algorithm(OPM)is adopted,and a multiuser uses a hybrid precoding method based on BD.Simulation results show that distributed systems in single-user systems are not superior to centralized in all cases,and it is closely related to the number of data streams and the number of blocks.Distributed multi-user system is better than the centralized structure and the rate increases as the number of distribu-tions increases.