Research Of Time Reversal Anti Interference Technology In Massive MIMO Systems

In the context of the 5G Communication Network,the timeliness,security and reliability requirements of wireless communication are increasing.Massive MIMO technology is one of the crucial technologies of 5G,which improves communication capacity of MIMO systems,spectrum efficiency and energy efficiency,but it also raises a series of problems.Due to the increasing number of base station antennas,some uncorrelated noise and fast fading are faded gradually,and only slow fading and inter-user interference become the main factors affecting the quality of user communication.In additionon,pilot pollution causes more serious channel delay spread in the multipath channel environment,which causes inter-symbol-interference to become an important factor that restricts system performance.Time-reversal technique is considered to be the effective techniques to versus dense multipath and time-selective fading in the field of wireless communications due to the temporal and spatial focusing.Aiming at the problem of inter-user interference and inter-symbol interference in Massive MIMO systems,two interference suppression techniques based on time-reversal are proposed to reduce the interference and improve the channel capacity of massive MIMO systems.The major research contents of this thesis include the following two points:Firstly,aiming at the problem of the inter-user interference in massive MIMO systems,the time-reversal precoding anti-interference technique is proposed.The method performs channel detection,multipath channel modeling,interference channel analysis and matrix designing in MIMO system to realize IUI suppression transmission in multipath channel.The technology performs channel optimization based on TR technology,utilizes temporal and spatial focusing to achieve energy focusing.Meanwhile,zero forcing algorithm is used to reduce the inter-user interference and co-channel interference in massive MIMO systems.Finally,the results of MATLAB simulation verify that the proposed method can reduce the average bit error rate and significantly improve the signal and interference to noise ratio and achievable rate of MIMO systems.Secondly,aiming at the problem of inter-symbol interference in massive MIMO systems,the time-reversal OFDM multiple access technology in massive MIMO system is proposed.The method implements ISI suppression transmission of TR-OFDM symbols in multipath channels by multipath channel modeling,OFDM modulation,cyclic prefix selection and time-reversal multiple access designing.The feasibility of the scheme is analyzed by the theoretic analysis layer,the results of MATLAB verify that the OFDM multiple access technology based on time reversal can improve spectrum efficiency,reduce the average bit error rate,improve achievable rate and system capacity of massive MIMO systems.