Research On Multiuser MIMO Technology Based On THP Precoding

With the rapid development of mobile communications and the diversification of communications services,the emerging services represented by multimedia and the like replace the traditional services that take voice messaging as the mainstay,which result in higher transmission rates and better quality of service to meet the growing demand for high-speed communications.However,the limited bandwidth resources are always the important factors which restrict the above requirements.Under this condition,how to effectively improve the spectral efficiency is a widespread concern.Multiple Input Multiple Output(MIMO)systems have drawn much attention because they can effectively improve the spectral efficiency without increasing the transmit power.The precoding technique is the key technique that can achieve or close theoretical capacity in MIMO system.It is also the research focus of academia and industry in recent years.This paper mainly focuses on the THP precoding,as a technology basis to start precoding technology research in the MIMO system.Aiming at the MIMO interference channel and multicell multiuser system,the design strategy of THP joint transceiver is proposed.And a two level precoding design algorithm with low complexity is proposed for the user aggregated scene in the large-scale antenna system.The main contents and results of this paper are as follows:First,the research status of MIMO precoding is analyzed in this paper.The linear precoding algorithm based on zero forcing(ZF)and the minimum mean square error(MMSE)is analyzed.Since nonlinear precodings have better performance than linear precoding,we further introduce and analyze the Dirty Paper Coding(DPC),THP and Vector Perturbation(VP)precoding.Secondly,the thesis studies the application of THP precoding in MIMO interference channel and proposes a joint transceiver design algorithm based on THP precoding with ideal channel state information at the base station.The method considers the design of the receiving matrix,the transmission matrix and the feedback matrix by minimizing the total MSE as the objective function under the power constraints of each transmitter.Due to the non-convexity of the problem,we transform the problem into a convex optimization problem by fixing two of the matrices and designing another matrix,and solve the closed-loop expression under the of Karush-KuhnTucker(KKT)condition.Finally,the algorithm of alternating iteration is used to solve the suboptimal solution.On this basis,we further consider the situation of channel error,and propose a robust THP precoding combined transceiver design algorithm under the assumption that channel error is Gauss distribution and the correlation between transmitter and receiver antenna is correlated.The simulation results show that the performance of the proposed THP transceiver algorithm is better than the linear precoding transceiver algorithm.Thirdly,the THP precoding technique is applied to multicell multiuser scene.Under the constraint of power of each base station,the feedback matrix,receiving matrix and precoding matrix are designed for each user in the cell by minimizing the total MSE of the system as the objective function.And the correctness of the theoretical analysis of the proposed algorithm is verified by simulation.Finally,aiming at the complexity of the precoding design in large scale antenna system,and considering the characteristics that users often have aggregate effect in geographic location,a low complexity two level precoding algorithm based on THP is proposed.The algorithm uses THP to eliminate the interference of the users in the cluster,and uses the linear precoding to eliminate the interference between the cluster.Simulation results show that although the algorithm has a certain degrees of loss in performance compared with full precoding,it reduces the computational complexity of the system.