Downlink Performance Optimization For Massive MIMO Systems With Imperfect CSI

With the vigorous development of communication and data services,various new wireless services have greatly optimized people’s quality of life.In order to meet the needs of intensive users,the wireless communication system under development has increased the energy consumption of the mobile system,but the wider network coverage and lower power consumption wireless communication system also bring more challenges to the wireless communication system.In 2021,my country has initially built the world’s largest mobile network(5th Generation mobile communication systems,5G),marking the official start of China’s 5G commercial era.The massive multiple-input and multiple-output(MIMO),known as one of the key technologies of 5G,can effectively improve the massive MIMO system by equipping dozens or even hundreds of antennas at the base station.The overall spectrum efficiency and the total energy efficiency of the system.This article will conduct an in-depth discussion on the optimization of spectrum efficiency and energy efficiency in the downlink of a massive MIMO system in the case of imperfect channel state information(CSI)in multiple cells.In summary,in view of the expanding user needs and business requirements and the challenges of green energy,the optimization of spectrum efficiency and energy efficiency in massive MIMO systems has reached the point where it is urgent and has very practical research significance.The main work done in this paper is as follows:1.Establish a system model of a massive MIMO system under imperfect CSI for multicell scenarios to study and analyze the data transmission process of the downlink,based on the classic channel estimation minimum mean square error algorithm(The Minimum Mean Square Error,MMSE)A channel estimation algorithm MC-MMSE(multicell MMSE)suitable for a multi-cell environment.The MC-MMSE channel estimation algorithm can obtain a diagonal matrix from the observation value and the channel estimation matrix to make the correlation calculation between signals more accurate,thereby Improve the system performance of massive MIMO,derive and analyze MC-MMSE to get the estimated value and estimation error.Then three precoding technologies of MRT,ZF and MMSE are used to derive the formula of the downlink to establish the maximum total spectrum efficiency of the system.According to the two different power allocation methods,the spectrum efficiency is optimized and compared,and the MC-MMSE is obtained by simulation analysis.Channel estimation technology has a larger spectrum efficiency optimization space than MMSE channel estimation technology,and the use of MC-MMSE channel estimation technology under the three precoding technologies can obtain better spectrum efficiency.Finally,it is concluded that the water injection power allocation algorithm is used.And with MRT precoding technology,it can give play to the better performance of the system.2.The system model of the downlink of the massive MIMO system is established by using the random geometry method,and a method to realize the downlink of the multi-cell massive MIMO system that can maximize the energy efficiency is designed,and reality is introduced into the system model.In the communication system,parameters such as the pilot reuse factor,the fixed ratio of downlink transmission,the degree of hardware damage,etc.,are derived through mathematical formulas,including the number of base station antennas,the number of users,the base station density in the cell,the pilot reuse coefficient,and the power control factor,etc.Parametric expression of the signal-to-interference and noise ratio of the downlink to obtain the spectral efficiency.Then,the energy efficiency is set as the regional nature,and the power consumption model of the energy consumption in various situations such as the transmission power,hardware loss,and signal processing in the region is considered,thereby obtaining the energy efficiency equation.Finally,the EE optimization is carried out by the alternating iterative optimization algorithm and the numerical values of the various parameters when maximizing EE are obtained.After simulation verification,the downlink implementation method proposed in this paper has good convergence and feasibility,energy efficiency optimization can be realized,the number of base station antennas and the number of users obtained by simulation are in line with the antenna settings of large-scale MIMO systems,and compared with the energy efficiency of other multi-cell downlinks,it also has obvious advantages in energy efficiency,and the numerical value is increased by about 12.2%,and the method proposed in this paper has stronger robustness when the environment changes,and it is also representative in actual situations.