Research On Resource Management Of User-centric Cell-free Massive MIMO System

With the rapid development of mobile communication,in order to meet the needs of increasing number of users,higher data transmission rate and more stringent quality of service,Cell-free Massive MIMO has been proposed as a new solution.User-centric Cell-free Massive MIMO cancels the concept of traditional cellular and cellular edge,and deploys access points(AP)far more than the number of users in the region to jointly serve users,which can provide users with more consistent and efficient services while reducing inter user interference.However,due to the large number of APs,when multiple APs cooperate and a single access point serves multiple users,how to select the appropriate service access point and reasonably control the transmission power of each AP,so as to reduce the same frequency interference and improve the overall performance of the system is particularly important.Therefore,the research of access point selection algorithm and power control algorithm is of great significance.This paper studies the User-centric Cell-free Massive MIMO system model.In the User-centric Cell-free Massive MIMO system,there is no traditional cellular concept,and there are a large number of APs in the deployment range.When all APs work together,there will be interference and power waste,so AP selection algorithm is needed to select.Then,the AP selection algorithm based on pilot allocation is analyzed theoretically and simulated,and it is proved that the algorithm has good performance in User-centric Cell-free Massive MIMO system.An improved particle swarm optimization algorithm is proposed to solve the maximum and minimum fair power control optimization problem of User-centric Cellfree Massive MIMO system.The purpose is to maximize the minimum transmission rate of UE and improve the overall transmission rate,so as to improve the overall service quality of the system.Firstly,the max-min fair power control problem of Usercentric Cell-free Massive MIMO system is analyzed,and the optimization equation is established.Then the specific formulas of this problem in uplink and downlink are derived respectively.This paper points out the shortcomings of the basic minimum fair power control algorithm,then puts forward the improved PSO algorithm in this paper,introduces its theory。 Finally,the simulation results show that the algorithm is superior in solving the maximum and minimum fair power control optimization problem,and can improve the overall spectral efficiency of users in the system on the premise of providing more consistent services for UEs.