The Research Of Pilot Contamination Resistance Technologies In High-capacity MIMO Systems

As the next generation of mobile communication technology,the 5^th generation needs to greatly improve the transmission rate and system capacity on the current basis,as well as reduce the communication delay to ensure transmission reliability.In the event that available spectrum resources become increasingly rare,high capacity MIMO systems can effectively overcome the scarcity of spectrum resources and improve the system capacity.High capacity MIMO is a technology which developed on the basis of massive MIMO.Different from massive MIMO,high capacity MIMO focuses on solving the various problems brought by the large-scale antennas and no longer simply discusses the impact of the number of antennas.In multi-cell TDD systems,the pilot reuse among cells can cause serious interference which is called pilot contamination.Pilot contamination can reduce the accuracy of channel estimation and make a series of effects on the downlink data transmission.It has become one of bottlenecks in the performance improvement of high capacity MIMO systems.As for this reason,this thesis mainly studies the pilot contamination in TDD mode.The main work is as follows:1.A pilot scheduling algorithm based on user location information is proposed for multi-cell high capacity MIMO systems.Firstly,this thesis establishes a suitable multipath channel and the signal angle of arrival model,and gives the expression of MMSE channel estimation and signal angle of arrival.Secondly,the thesis analyzes the influence on angle of arrival of the pilot signal on the users’MMSE channel estimation.Finally,a pilot scheduling algorithm based on user location information is proposed to ensure that the angle of arrival of desired user and interference user are not overlapped.And the effectiveness of the proposed pilot scheduling strategy in reducing the influence of pilot pollution is verified by simulation.2.A pilot scheduling algorithm based on Simulated Annealing is proposed for the pilot scheduling issue in high capacity MIMO systems.Firstly,this thesis builds the pilot scheduling model and analyzes the solution of the pilot scheduling problem from the perspective of combinatorial optimization.Then the Simulated Annealing algorithm is used to solve this combinatorial optimization problem.By setting a reasonable tabu region in the neighborhood among cells,the number of feasible solutions as well as the computational complexity is reduced,and the algorithm convergence is accelerated at the same time.The simulation results show that the Simulated Annealing based pilot scheduling algorithm has a good performance of convergence and anti-pilot contamination.