Research On Precoding Algorithm And Its Application For Massive MIMO System

With the rapid development of wireless mobile communication,people's requirements for rate,delay and throughput is also rising,but the traditional MIMO technology is unable to meet this requirement.At the time,the massive MIMO technology is proposed,which can improve the overall system spectrum utilization and system capacity etc.In the massive MIMO system,due to the base station with hundreds of antennas services a set of users,the interference between users will be greater.One way to solve this problem is the precoding technology.The thesis studies the precoding design problems of massive MIMO system.The thesis analyzes the shortcomings of traditional precoding algorithm and propose optimized precoding algorithm in three different scenarios such as the perfect channel state information(CSI),the imperfect CSI and non-ideal hardware.The contents of this thesis are as follows:In the case of perfect CSI,the thesis studies precoding problems for the single cell and multiple cell scenes.In a single cell scenario,the thesis presents an optimized block diagonalization pre-coding algorithm by combining the traditional zero forcing and block diagonalization pre-coding algorithm,which greatly reduces the interference between users and improves the overall performance of the system.In multi-cell scenarios,we analyze the reasons for the formation of inter-cell interference and leakage plus noise ratio of single receive antenna is used to get the criterion based precoding matrix,which can improve the performance of cell edge users.Simulation results show that the proposed algorithm can improve the system capacity and reduce the bit error rate.In the imperfect CSI,the thesis mainly studies and analyzes the impact of imperfect CSI in single cell scenarios.The thesis designs the pre-coding matrix by minimizing the mean square error and the maximum SNR criterion.In addition to the study of the precoding design of the Rayleigh channel model,the thesis simply introduces the rice channel model and Nakagami channel model and compares these three kinds of channel models.Simulation results show that this algorithm can solve the problem of imperfect CSI to a certain extent.Aiming at the problem of non-ideal hardware,the thesis studies the three problems of in-phase and quadrature(IQ)imbalance,high-power amplifier(HPA)nonlinear and phase noise.For these three problems,we first analyze the impact on the system.Secondly,the deficiency of the traditional precoding algorithm is given.Finally,the optimization of the precoding algorithm is proposed.The simulation results show that the optimization algorithm can restrain the influence of non-ideal hardware on the system.For the precoding algorithm for relay system,this thesis firstly introduces the concept of relay system.Secondly,we obtain the pre-coding matrix by using the least mean square error criterion and combining with the theory of the thesis.In the process of solving the problem,we reduce the number of the unknown variables and simplify the cost function.Finally,we depress the computational complexity.