Study On Pilot Scheduling Algorithm Of Massive MIMO System Based On Space Partition

Massive multiple-input multiple-output(MIMO)technology can fully exploit spatial freedom for spatial multiplexing transmission,improve spectrum efficiency,and achieve energy-efficiency orders of magnitude improvement,so it has become one of the key technologies in the fifth generation of mobile communications.However,in the massive MIMO system,due to the limited orthogonal pilots in the coherent time,the pilots are inevitably reused in neighboring cells,leading to the generation of pilot contamination,which seriously affects the system performance.This paper mainly studies the problem of pilot contamination in massive MIMO systems.Based on the division of user cell space by smart antennas,it uses various technologies,such as fractional pilot multiplexing allocation and cell user pilot time slot grouping.A fractional pilot allocation scheme based on space division and a pilot allocation scheme with time-shift joint space division are introduced.1.This article introduces the status of pilot contamination research in massive MIMO systems,builds a cellular system model,and analyzes the transmission process of uplink and downlink data transmission links.Through comprehensive literature surveys by scholars in this field,formulas are used to derive and analyze the causes and effects of pilot contamination in the system.The analysis results show that the number of antennas in the base station is constantly increasing,and the pilot contamination will not be reduced accordingly.On this basis,a system model for dividing the cell by a smart antenna is constructed,and the transmission process of the uplink and downlink data transmission links is analyzed,and the advantages and disadvantages of using the space division technology are summarized.2.Based on the smart antenna technology to divide user cells in physical space,so that users in each zone are only polluted by pilots in one direction,a fractional pilot allocation scheme is proposed.By dividing the orthogonal pilot sequence into groups,and then assigning a subset of orthogonal pilots to the sector-shaped cells of the neighboring cells that generate interference in a specific method,the pilot contamination of users in the target cell is reduced.Simulation results show that the proposed pilot allocation scheme can reduce the pilot contamination more effectively and improve the fairness and performance of the system than the space allocation pilot allocation.3.The pilot allocation scheme for time-shift joint space division is proposed by combining from the transmission time domain and the physical space domain.Reducing the number of pilot sequence multiplexing in time and spatially reducing the source of pollution,thereby reducing pilot multiplexing interference and obtaining more accurate channel estimation.It is known from the simulation experimental results that the proposed joint scheme can effectively reduce the interference caused by multi-cell pilot multiplexing,obtain accurate channel estimation,and improve system performance.