Study On Multi-user Scheduling Algorithm In Massive MIMO Uplink System

With the rapid popularization of mobile devices(e.g.smart phones),people's demand for mobile communication systems is also increasing quickly.Massive MIMO system can significantly improve the capacity of wireless communication system by equipping a large number of antennas at the base station(BS).By using multi-user scheduling technology in Massive MIMO systems,it can give full play to system performance and serve a large number of users.However,due to a series of new problems brought by the significant increasing of antenna number and user number,it still faces many difficulties and challenges to put the multi-user scheduling in Massive MIMO system into effect.In this paper,the key technologies and main problems in Massive MIMO multi-user uplink network will be studied in depth.Firstly,we will introduce the background and significance in Massive MIMO multi-user scheduling system and discuss the key technologies,including system model,uplink receiver,3D MIMO channel,channel estimation and so on.Then,three traditional scheduling algorithms will be talked:Round Robin(RR)scheduling,Proportional Fair(PF)scheduling and Maximum Carrier to Interference(Max C/I)scheduling.In addition,we will present the advantages of grouping based scheduling algorithm in Massive MIMO multi-user system.Next,aiming at reducing the high computational complexity of multi-user scheduling in Massive MIMO uplink network,a new grouping based scheduling algorithm with low complexity will be proposed.The main idea of the algorithm is to divide all the RBs into several segments,and then each user is grouped into a most suitable segment,so as to reduce the complexity of scheduling.Furthermore,the users will be scheduled on the basis of proportional fairness principle and the channel correlation between scheduled users.The simulation results show that,compared with RR algorithm and PF algorithm,the proposed algorithm achieve a good throughput performance with low computational complexity.And then,aiming at the problem of how many users should be scheduled in Massive MIMO system,we consider three factors that affect system performance:antenna number of BS,channel correlation between scheduled users and the error of channel estimation,and we simulate the relationship between the three factors and the best scheduled user number.The simulation results show that the three factors have significant impact on system throughput performance,taking these factors into full consideration and choosing an optimal number of scheduled users can achieve a good throughput performance in Massive MIMO system.If there are too many or too few scheduled users,the system can't present a best performance.We also give some suggestions on the optimal number of scheduled users in different scenes.