Research On Pilot Allocation In Massive MIMO

In such an era of rapid development of wireless communication technology,various emerging services have appeared one after another,and the demand for communication mobile data traffic has shown an exponentially increasing attitude.Massive multiple-input multiple-output(Missive MIMO)technology,by deploying a large number of antennas on the base station side and increasing the antenna dimension,can serve multiple users on the same time-frequency resource,thereby greatly improving system spectral efficiency and channel capacity,and increasing system throughput..However,to realize the performance advantage of Missive MIMO technology,accurate channel state information(CSI)must be obtained.However,due to the limited pilot resources,the pilot contamination problem caused by the reuse of the same pilot among users in adjacent cells severely interferes with the base station to obtain accurate CSI.Therefore,How to suppress pilot contamination has become a crucial issue for Missive MIMO technology research.The pilot-based channel estimation method is the most commonly used way to obtain CSI today.By properly designing the pilot allocation scheme,the pilot contamination of the system can be significantly reduced.This paper starts with the study of pilot allocation schemes and designs a pilot allocation scheme that can effectively reduce pilot contamination while ensuring system performance.First,the system outlines the development process and key technologies of the Missive MIMO system,and studies the causes of the pilot contamination of the Massive MIMO system and its impact on the performance of the Massive MIMO system.Several existing methods of suppressing pilot contamination and their advantages and disadvantages are analyzed and compared,and the status of domestic and foreign research on various methods of suppressing pilot contamination is analyzed.Then,the theoretical basis of the formula that the pilot contamination affects the system is derived,and the user signal-to-interference ratio(SINR)in the community is different.The shortcomings of the traditional pilot allocation scheme are pointed out,and a pilot allocation scheme based on multi-level soft frequencies reuse is derived..This solution divides users into edge user groups and central user groups according to the interference received by users in the cell.Edge users in adjacent cells use mutually orthogonal pilot sequences,and the central user group reuses the same pilot sequence,which is effective.The communication quality of the edge users is improved,but the pilot overhead is increased.Finally,to address the problem of increasing pilot overhead,a pilot allocation scheme that combines distance factors and user priorities is proposed.In this solution,the interference experienced by users is represented by a distance factor,and each user in the cell has a weight representing its priority.A cost function is set according to the distance factor and priority weight of each user to determine the user's pilot frequency.degree of reuse.Theoretical and simulation results show that the pilot allocation scheme can effectively reduce pilot overhead while ensuring system performance.