Research On Interference Cancellation Methods In Massive MIMO Systems

With the popularization of intelligent terminal devices and the rapid growth of new data-intensive mobile business,the 5th generation(5G)mobile communication system faces great challenges of increasing system capacity and user rate.As one of the most promising and key candidate technologies in 5G mobile communication system,massive multiple-input multiple-output(MIMO)technology can effectively improve the spectral efficiency,energy efficiency and reliability of data transmission in wireless communication systems.For massive MIMO system,the main research work and contribution of this paper are summarized as follows:First of all,this paper mainly studies the theory and technology of massive MIMO,investigates and summarizes the interference elimination methods and pilot pollution elimination methods in multi-cell and multi-user massive MIMO systems.In order to study the problem of interference cancellation in complex interference scenarios and the problem of pilot pollution elimination in multi-cell,multi-user massive MIMO systems,the research provides the theoretical foundation.Secondly,aiming at the problem of cross-interference cancellation in multi-cell and multi-user massive MIMO system,this paper presents a method based on joint user scheduling and transceiver design.By analyzing the characteristics of cross-link interference,the user scheduling constraint factor is designed to prevent from scheduling the downlink edge users which suffer from severe cross-link interference so to reduce the user-to-user interference.For the serious interference from base station(BS)to BS,the matrix singular value decomposition(SVD)is applied to decompose the large-scale BS to BS channel into several interfering sub-channels and an allocation method is designed to process the interfering sub-channels by the uplink BS and the downlink BS,respectively.It can be seen from the system simulation results that the reachable rate of the user in the uplink cell is greatly improved.Thirdly,aiming at the problem of eliminating pilot pollution in multi-cell and multi-user massive MIMO system,this paper proposes a heuristic pilot allocation method based on the azimuth of the analog beam combined with hybrid beamforming.Based on this,considering the fairness of users,a pilot allocation method based on user grouping is put forward to ensure the performance of edge users.From the simulation results,we can see that the heuristic pilot allocation method and user-based pilot allocation method proposed in this paper can effectively reduce the pilot pollution and improve the spectral efficiency and system capacity of massive MIMO system.