| This paper mainly studies the pre-coding technology and multi-user scheduling algorithm in the downlink data communication of MU-MIMO communication system.First,it introduces the research status and significance of MU-MIMO technology.Based on the known literature and the actual implementation scheme,it expounds the basic principle and research direction of MIMO technology.Secondly,this paper takes simple single-user MIMO system as an example,divides it into two types of scenarios at the base station side through the channel transmission model,namely the convinced CSI model and the unconvinced CSI channel model,and calculates the ideal system capacity of the corresponding scenario theoretically.Then the spatial multiplexing and spatial diversity of MIMO technology and their functions are discussed.the system capacity of multi-terminal downlink is obtained by calculating the simulated MU-MIMO channel transmission model.several precoding algorithms and multi-terminal scheduling algorithms commonly used in MU-MIMO communication system are briefly explained.Based on ZF-CI algorithm and BD algorithm,this paper analyzes the complexity of several common algorithms aiming at the scheme of downlink precoding algorithm,such as traditional BD algorithm,BD algorithm based on QR decomposition and GZI algorithm.In the case that the system capacity and rate are not changed or changed in a small amount,this paper proposes an improved BD algorithm for the purpose of reducing operational complexity,and shows its advantages in some application scenarios.In addition,based on the implementation of the traditional SLNR algorithm,this paper makes a certain degree of improvement,which is considered as an improved SLNR algorithm.When the terminal of demand communication needs to transmit data to be sure,the improved SLNR algorithm relaxes the target when solving,improves the SINR of the worst data stream and improves the data certainty of the terminal.On the premise of not changing the capacity and rate of the base station system,the performance of BLER with poor channel condition was greatly improved,that is,the communication quality of the worst terminal was optimized under the condition that the total transmitting power and capacity of the base station remained unchanged.For the downlink multi-terminal scheduling technology of MU-MIMOcommunication system,an improved scheduling algorithm based on sub-channel clustering is used to implement the scheme.Based on inter-terminal correlation,all terminals in the area covered by the base station are clustered and classified.In this paper,the complexity of multi-terminal scheduling algorithm is reduced by matrix reconstruction to reduce the correlation calculation among sub-channels containing terminals in the cluster.Through simulation,the algorithm complexity is reduced effectively with a little sacrifice of channel capacity and transmission rate. |
