Research On Multiuser Hybrid Precoding In Massive MIMO System

Massive MIMO technology is the core technology of 5G communication.It has the advantages of high throughput and high throughput,which is highly concerned by the academia and industry.Precoding technology can send signals and suppress interference between data streams.It is widely used in the Massive MIMO system.All digital precoding is unable to be used in Massive MIMO system due to high complexity and expensive hardware cost.Therefore,analog and digital hybrid precoding technology has become a new research hotspot.In this paper,we study basic structure of the Massive MIMO system,the channel model and the hybrid precoding technology.The main work and results are as follows:1.We study the BD precoding and SLNR criterion of MU-MIMO system.Since the precoding vector of BD algorithm is derived from the zero space of the interference channel matrix,there is a constraint on the number of antennas,that is,the number of transmit antennas is greater than the number of all the receiving antennas.The fairness of precoding based on SLNR criterion in multiuser systems is not good,and the equal power allocation strategy is used to limit the performance improvement.To solve this problem,an energyefficient iterative SLNR(EI-SLNR)scheme is proposed in this paper.The weighted equivalent channel is used to improve the fairness of the user,and the dynamic power allocation strategy is used to further improve the performance of the system.Simulation results show that compared with BD precoding and SLNR criterion,the proposed algorithm improves the system rate and BER performance without increasing computational complexity,and the fairness of multi-user is also improved.2.In single-user hybrid precoding design of Massive MIMO system,we introduce the hybrid precoding based on SVD decomposition and orthogonal matching pursuit.The hybrid precoding based on SVD decomposition has poor performance,and the complexity of hybrid precoding based on orthogonal matching pursuit is relatively high.To avoid shortcomings of the above algorithms,a hybrid precoding algorithm based on optimal decomposition is proposed in this chapter and the complexity of the proposed algorithm is relatively low.Simulation results show that the BER performance and spectral efficiency of the system are improved.3.In multi-user hybrid precoding design of Massive MIMO system,we study the hybrid BD precoding algorithm,where the RF precoder is designed by analog phase shifter,and multiuser interference in the baseband can be eliminated using BD algorithm.But the hybrid BD algorithm has the antenna number constraint,and the common RF domain designing makes the system performance not ideal.Therefore,a new hybrid optimization algorithm based on SLNR is proposed in this paper to increase the array gain and improve the user's system capacity by RF beamforming optimization.Then the SLNR criterion is used to suppress multi-user interference in the baseband.Compared with the conventional hybrid BD algorithm,the proposed hybrid optimization algorithm based on SLNR in this chapter has no constraints on the number of antennas.The simulation results show that the proposed algorithm outperforms the conventional hybrid BD algorithm in BER performance and spectrum efficiency.