Research On Reducing Pilot Pollution In Large-scale MIMO System

The continuous development of wireless communication system,especially the wide application of intelligent terminal,makes the communication system to improve the data transmission rate.By increasing the number of antennas at the transmitter and receiver of the system,MIMO technology can effectively improve the data transmission rate and anti-interference capability of the communication system.However,the system gain brought by the number of antennas in the traditional MIMO system is far from enough to meet people's demand for system performance.The emergence of large-scale MIMO has provided a new approach to solve this problem.In this paper,the pilot pollution in large-scale MIMO has always existed and cannot be completely eliminated,the main direction is the research of channel estimation method and pilot allocation.This paper firstly introduces the large-scale MIMO system and the causes of pilot pollution,the principle and development history of large-scale MIMO system,and expounds the current research status of reducing pilot pollution at home and abroad.Secondly,this thesis studied the traditional channel estimation method,least square channel estimation method and the minimum mean square channel estimation,theoretical derivation estimation algorithm and the simulation analysis of the performance of the traditional channel estimation method,combining with the characteristics of the traditional channel estimation method,studied an improved channel estimation method,compared with the traditional channel estimation method,the system performance are improved to a certain extent.Finally,this paper expounds the traditional methods of pilot allocation,think in terms of different pilot allocation strategy,combined with the reason of pilot pollution.Meanwhile,studied the reasonable pilot allocation strategy from the time domain and the user area,so as to reduce the pilot pollution.On the basis of the traditional method of pilot allocation,the improving measures are put forward combining with the characteristics of the traditional allocation strategy,not only deduced the performance of improved scheme but also simulated it and concluded that the improved scheme can effectively improve the sum rate of the downlink transmission system.