Research On Downlink Data Link Communication Technology Of UAV Based On FRFT

The UAV downlink data link is a communication link for data interaction with the ground command center.Orthogonal Frequency Division Multiplexing(OFDM)technology is widely used in downlink data link transmission due to its high spectrum utilization and fast transmission rate.With the continuous development of wireless communication technology,the communication demands of good signal concealment,strong anti-interception and anti-multipath capabilities are increasing.Among them,Fractional Fourier transform(FRFT)can adapt to fast time-varying channel more flexibly because its fractional order is variable.Based on an in-depth study of OFDM transmission methods,FRFT technology is combined with OFDM technology to carry out the research on the communication technology of UAV downlink data link based on FRFT.It provides key technology and method for improving the data transmission rate and anti-interference ability of communication system which has important theoretical significance and practical application value.Based on an in-depth analysis of the Fractional Fourier Transform Technology(FRFT)and the OFDM transmission method of the downlink data link of the UAV,FRFT technology is combined with OFDM technology in the thesis to develop cyclic prefix addition based on the FRFT-OFDM communication model.Then an optimal fractional order selection method which can effectively reduce the system bit error rate is proposed,and it is verified that it can effectively reduce the system's bit error rate through simulation.In order to further improve the anti-interference ability of the downlink data link of the UAV,the thesis introduces the G function mechanism in differential frequency hopping communication,and proposes a FRFT-DFH-OFDM transmission method to achieve efficient and reliable transmission.In the research,the signal generation and reception of this method are modeled,and the focus is on the generation of one-dimensional data in the generation mechanism,the selection of two-dimensional information data subcarriers controlled by the G function,thetime-frequency analysis of FRFT signals in the reception mechanism and the decision of the frequency point is designed.The correctness is verified by simulation analysis.In order to further verify the applicability of the FRFT-DFH-OFDM transmission method,the thesis performs simulation tests and analysis on the peak-average power and bit error rate of the method based on the CDL scheme of UAV downlink data link.The simulation results show that the method has better performance than traditional OFDM transmission methods.