Codebook Design Of Massive MIMO For5G

Massive MIMO has become one of the candidate technologies for 5G mobile communication system by increasing the space gain of transmission antenna though configuring traditional MIMO antenna in the base station coverage area.In the environment of multi-user multi-scene communication,a large number of transmission antennas and the simultaneous service of multiple users can cause serious interference,and precoding techniques and multi-user selection techniques can effectively reduce these disturbances.At present,the precoding and multi-user selection technology based on the traditional MIMO system can not be directly applied to the large-scale MIMO system.Based on the analysis of channel model and precoding technology of large-scale MIMO system,this paper studies the problem of reducing frequency conductivity pollution and the design of codebook which conforms to the large-scale MIMO system.Firstly,this paper analyzes the precoding technology of MIMO from three aspects:codebook design,codebook search and multiuser selection.At the same time,the multi-user MMO downlink precoding system model is built.3D MIMO simulation models are compared and analyzed for different transmission scenarios,and WINNER 2 simulation model is introduced.Then,a channel estimation scheme based on improved DFT algorithm is proposed to solve the pilot pollution problem in MMO system.This method obtains the time domain impact response of the channel by the channel in the transform domain and uses interference signal outside the useful signal part to carry out Hanning window processing and zero padding,screening out the effective channel impulse response.LS estimation algorithm,traditional DFT estimation algorithm and improved DFT estimation algorithm are introduced.The simulation analysis compares the channel estimation accuracy of the three algorithms and reduces the lead frequency pollution.Finally,this paper analyzes the code books and transmission channel characteristics of the existing MMO technology,improves the type selection,and structure design of the codebook,and puts forward a construction scheme for the design of the improved code books by using the DFT codebook and R11 code combination.The simulation results show that the improved code design scheme is more suitable to the real large-scale 3D MIMO channel.At the same time,the optimization analysis of the design code is made from the complexity of search and inverse computation of matrix.