Hybrid Precoding Research Of Millimeter Wave Massive MIMO System

With the development of wireless communication technology,it has gradually entered into all aspects of people's daily life,and greatly affected people.At present,the requirements for spectrum efficiency,system capacity,and bit error rate of wireless communication are still increasing.The combination of millimeter wave communication and Massive MIMO is considered to be a promising technology for future 5G communication.Millimeter-wave Massive MIMO can significantly increase system throughput due to the large spectral band(30-300 GHz)and the gain provided by massive MIMO.This paper focuses on the millimeter-wave Massive MIMO system,which is aimed at the problem of excessive energy consumption in traditional all-digital precoding.A hybrid precoding method will be used to solve this problem,decomposing the all digital precoder into a high dimensional analog precoder and a low dimensional digital precoder.This structure requires only a small number of RF chains to achieve near-optimal performance.First,the transmission model of millimeter wave Massive MIMO system is analyzed,and the millimeter wave channel model is also analyzed.In the case of known channel matrix,three different linear precoding schemes are adopted for the signal.In order to transmit the signal of the base station to the user end more efficiently and completely,three different methods are designed.The work content is as follows(1)Under the multi-user millimeter-wave massive MIMO system,a ZF hybrid precoding method is proposed,which decomposes the overall capacity optimization problem into separate antenna arrays.In the case of known channel state information,Firstly,using the idea of continuous interference cancellation algorithm,the phase is controlled by the analog precoder,then the zero-forcing(ZF)precoding is applied on the digital precoder,and each antenna array is optimized one by one,and finally the parallelized iteration is realized.Process to maximize system capacity.(2)Under the single-user millimeter-wave massive MIMO system,a hybrid precoding algorithm based on geometric mean decomposition is proposed for the bit error rate caused by bit allocation in singular value decomposition in different channels and SNR.In the case of considering both the precoder and the synthesizer,the digital encoder is first designed with singular value decomposition at the base station side,and the analog precoder is designed using the base tracking principle.A heuristic algorithm is then used at the receiving end to design the digital synthesizer and the analog synthesizer.The hybrid precoding scheme has a lower bit error rate than the conventional singular value based hybrid precoding,and the spectral efficiency is closer to the ideal value.(3)Under the multi-user massive MIMO system,in order to meet the requirements of hardware limitation and realize the potential of large-scale multi-user MIMO system,it is proposed to use pure phase control to couple the analog precoder to the transmission antenna.The cost of the phase shifter.Low-dimensional multi-stream processing is then performed on the digital precoder to reduce interference between users.The proposed method can approach the performance of all-digital ZF precoding and greatly reduce the use of the RF chain.