The Analysis Of Power Allocation Of Base Station Cooperations In Massive MIMO

Video,data and other services in modern society have been greatly needed,in order to meet the features of development diversity and high efficiency of data transmission,5G communication has developed rapidly.Massive MIMO with large antenna array at the base station side can greatly improve the capacity of the system and has become a highlight in the 5G communication.With the development of mobile communication technology,it should not only pay attention to the performance of the system,but also consider the allocation of resources and energy consumption.In the design of wireless communication system,energy efficiency and spectrum efficiency must be taken into consideration.There is no doubt that green communication will be one of the important aspects of wireless communication in the future,from this point of view,it is very important to study the optimization of transmit power during the process of communication.The topic of this thesis comes from the National Natural Science Foundation of China(61372126)undertaken by my tutor.On the basis of introducing related theoretical knowledge of Massive MIMO,the thesis establishes Massive MIMO system with multiple antennas multiple users.When the base station cooperation is CoMP,channel state information(CSI)and data are shared among base stations.When the base station cooperation is CoBF,only CSI is shared among base stations.Firstly,the method of transmit power optimization is introduced,it is based on convex optimization.The expression of SINR and achievable rate are derived,then formulating power minimization problem according to target functions and constraints,it can be proved that the problem belongs to linear programming and can be solved by convex optimization.Simulation results show that the proposed method can greatly reduce the transmit power.Then the second method is introduced,the power minimization problem is solved by asymptotic analysis in large system.The structure of the optimal linear precoding is derived when the number of antennas at the base stations is large.It can be proved that transmit power is depended on long-term channel attenuation,relative interference intensity,quality of channel estimation and target achievable rate.The influence of these variables on the performance of the system is obtained and validity and reliability of the method are proved by simulations.The two methods of transmit power optimization introduced above in this thesis are both related with linear programming,constraits of linear programming are both involved in achievable rate,however,not any value of achievable rate is the solution.Reason is the trade-off between achievable rate and propagation environment,such as path loss,limit power for pilot sequences and so on,these all can have an impact on achievable rate.In this thesis,algorithm is designed to ensure that each user can have a certain amount of achievable rate and power can be distributed reasonably at the same time.