| At present,various countries are busy in 5G deployment.Due to its ability to effectively improve the spectrum efficiency and energy efficiency of the system,and its better robustness,massive MIMO technology has become one of the most potential technologies in 5G.However,most of the current researches on massive MIMO systems are carried out on the condition that channel state information has been obtained,which obviously cannot reflect the real communication environment.It is clear that channel estimation plays an important role in improving system performance.The channel estimation of massive MIMO systems in TDD mode is proposed.Based on the available literature,this paper summarizes the development of channel estimation technology in massive MIMO systems.The advantages and disadvantages of the existing channel estimation algorithms are analyzed.In this paper,pilot contamination in multi-cell channel estimation is analyzed.In order to reduce the computational complexity effectively,a novel channel estimation algorithm is proposed based on the given channel model.The paper introduces the channel estimation scheme from the aspects of system model,design of pilot structure,optimization of channel estimation and signal detection.In proposed method,the ZC sequence is used as the pilot signal,and the pilot structure is designed through the time-frequency conversion.Users in the same cell send the same ZC sequence,and the adjacent cell selects the cyclically shifted version of the ZC sequence.After the Fast Fourier Transform,the pilot sequences of the user in same cell are placed on the mutually orthogonal carriers.The pilot between adjacent cells also remains orthogonal to each other due to the correlation of ZC sequences.The receiver obtains the channel state information about the pilot by using the properties of cyclic convolution and Fourier transform,the DFT difference algorithm is used to detect the transmitted data.Finally,the advantages of the proposed scheme and the direction of improvement are analyzed,and the corresponding performance simulation is carried out. |
