| In the co-time co-frequency full duplex technology,the upstream and downstream signals are located in the same frequency band,which can double the utilization rate of spectrum resources theoretically.The application of full-duplex technology in the fifth generation millimeter wave mobile communication has become one of the research hotspots in academia with the increasing shortage of middle and low frequency spectrum resources.However,the communication quality is affected by the inevitable selfinterference in the full-duplex communication system.This thesis focuses on the co-time co-frequency full-duplex communication in the millimeter wave band.A self-interference suppression algorithm in frequency domain is designed for the high-noise environment,which reduces the influence of noise on the self-interference channel estimation and guarantees the self-interference suppression efficiency.The specific research content of this thesis can be summarized as follows:Firstly,the co-time co-frequency full-duplex model and its key techniques for selfinterference suppression are investigated.Different self-interference suppression algorithms are derived and analyzed,and the frequency domain self-interference suppression system model is built,including the transmitted signal model,the selfinterference channel model and the received signal model.In the transmitted signal model,the physical layer frame structure is designed according to the fifth-generation mobile communication technology protocol standards.Discrete Fourier Transform(DFT)channel estimation and smoothing techniques were used to improve the self-interference suppression ability under limited conditions.Secondly,a self-interference suppression algorithm based on DFT and exponential mean average is designed.Through the theoretical derivation of DFT channel estimation algorithm and exponential mean average algorithm,the principle of noise suppression is analyzed,the DFT channel estimation algorithm and exponential mean average algorithm are introduced into frequency domain self-interference suppression,the self-interference suppression algorithm combined with DFT exponential mean average is designed,and the theoretical feasibility of the algorithm is verified,and the simulation model is established.The algorithm is verified and analyzed by simulation.The simulation results show that when the interference-to-noise ratio is 10 d B to 30 d B,the suppression performance of the DFT combined with exponential mean average algorithm under the optimal smoothing coefficient is better than that of the frequency domain self-interference suppression algorithm under the LS channel estimation,and when the interference-tonoise ratio is 20 d B,the self-interference suppression capacity of the improved algorithm is 19.63 d B,and the performance is improved by 0.7d B.Finally,the Field Programmable Gate Array(FPGA)implementation and performance verification of the self-interference suppression system with DFT combined with exponential mean average are completed.The overall architecture of full duplex selfinterference suppression is designed,including the architecture design of transmitter and receiver,and the design and workflow of self-interference suppression module FPGA are introduced.The test platform of the self-interference suppression system is built,and the performance of the system is verified in the actual environment.The suppression performance is analyzed.The results show that when the received self-interference signal power is-67 d Bm,the self-interference suppression is 17.8d Bm,and the performance loss is 1.8d B compared with the simulation results.The DFT combined with exponential mean average self-interference suppression algorithm studied in this thesis has been successfully applied to the full-duplex communication system with the same frequency at the same time,which provides a theoretical basis and implementation reference for the further research of full-duplex communication system under high noise environment. |
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