Research And Simulation Of Key Technologies Of 5G Oriented Physical Layer For Massive MIMO

With the development of communication technology and people's demand for better quality of service,the fifth generation(5G)has become a global research hotspot.5g has been officially commercialized in 2020.Among them,large-scale multiple input multiple output(massive MIMO)technology is considered to be an important means to improve the spectral efficiency.Under this background,this paper studies the key technologies of the physical layer of 5G oriented massive MIMO.Firstly,this paper introduces the technical principle of massive MIMO channel modeling and the massive MIMO system based on this modeling technology.At present,there are two kinds of beamforming methods:continuous beamforming and discrete beamforming.The continuous beamforming massive MIMO system can turn the beam angle to the user's direction to obtain the highest channel gain,but there are two users too close to each other,resulting in mutual interference.The massive MIMO system with discrete beamforming selects the closest beam for users in a series of nearly orthogonal beams,and one beam can only serve one user,and the remaining users can only select the next nearest beam or wait for the next transmission.The simulation results show that the rate of continuous beamforming is higher than that of discrete beamforming.Then,in order to further improve the data rate,the sparse code multiple access(SCMA)technology is introduced into the massive MIMO system.According to whether different coding layers of SCMA are in the same beam,they can be divided into intra beam coding and inter beam coding.Considering two beamforming methods,there are four different types of massive MIMO-SCMA systems.Among them,the continuous beamforming system with intra beam coding and the discrete beamforming system with inter beam coding are mainly used in the industry.The simulation results show that the system speed of the system with intra beam coding is high.In addition,the rate of continuous beamforming system is higher than that of discrete beamforming system.Finally,in order to solve the problem of user to user interference in the continuous beamforming system with intra beam coding and the problem that users of the same beam in the discrete beamforming system with intra beam coding cannot be served at the same time,a hybrid SCMA coding scheme is proposed,that is,when the user to user interference is small,the user carries out independent SCMA coding,and when the user to user interference is large,the users carry out joint SCMA coding.The scheme can provide users with high rate and reliable data transmission services.It can be considered as a system combining the advantages of two systems,i.e.intra beam coding and inter beam coding.The simulation results also show that the user rate of the proposed system is second only to the intra beam coding system,and the correct transmission rate is the highest.