Research On New Precoding Technology In MIMO Downlink Communication

More and more high data transmission demand of users has promoted the development of mobile communication technology.In addition,with the rapid development of Internet technology,smart terminals have been popularized and applied in daily life.Therefore,improving the performance of downlink system and simplifying the complexity of receiver are important directions for the development of mobile communication.By preprocessing at the transmitter,precoding can effectively reduce the complexity of the receiver,thus becoming one of the research hotspots in this field.In this thesis,a new type of precoding technology in multiple-input multiple-output(MIMO)downlink communication system is studied.In order to optimize the system performance,a more robust precoding system was proposed considering the effect of actual delay on the precoding performance,and a hardware testbench was built for experimental verification.On the other hand,the multiuser precoding scheme is studied,the precoding scheme based on space-time line code is analyzed,and a new scheme with better performance is presented.The specific research contents of this thesis are as follows:Firstly,this thesis introduces the research background of MIMO technology,precoding technology,and the research status of space-time line code technology.Secondly,this thesis introduces Tomlinson-Harashima precoding(THP)and vector perturbation(VP)precoding techniques in detail,and compares the THP technology based on different matrix decompositions and the VP precoding technology of different perturbation vector search algorithms through simulation.In addition,the influence of equalizer on nonlinear precoding technology is analyzed,and the deterioration of nonlinear precoding performance by equalizer is proved by computer simulation.Third,in this thesis,aiming at the problem of nonlinear precoding is sensitive to transmission delay,a VP system based on time delay compensation is presented,by optimizing the structure of the transmitter makes the system performance,but also reduces the complexity.A hardware test system is built to verify the performance of the proposed scheme.Fourthly,this thesis studies the multiuser precoding scheme,studies the multi-user precoding scheme based on space-time line code,and uses the new diversity technology of space-time line code to obtain the performance gain.In order to improve the system performance,a new multi-user precoding scheme based on space-time line code is proposed.An enhancement scheme based on the feedforward information is also proposed to further improve the system performance.Finally,this thesis summarizes the main research contents and contributions.