Research And Implementation Of High Speed OFDM Communication Link

With the rapid development of mobile communication technology,UAV communication has been widely used in various fields.In order to realize high-speed communication between UAVs,in the uav airspace communication scenario,the main scheme of physical layer of high-speed OFDM communication link is designed based on OFDM technology to ensure high-speed and reliable data transmission in this scenario.Firstly,the system requirements of high-speed OFDM communication links are introduced,including application scenarios,channel models and design requirements.The principle of high-speed OFDM communication link and the design process of system parameters are described in detail.Finally,the frame structure design of the system is given.Second,the time-frequency synchronization algorithm of high-speed OFDM communication link is studied.Because of the large dynamic frequency offset and multipath effect in the application scenarios of the system,the synchronization of the system will be seriously interfered.Therefore,the anti-frequency offset performance of Zadoff-Chu(ZC)sequence is studied,and the perfect autocorrelation of zadoff-Chu(ZC)sequence is verified to be suitable for the channel model of the system.Therefore,a PNweighted ZC sequence is designed based on ZC sequence,and its time-frequency synchronization algorithm is given.The simulation results show that in AWGN channel,when SNR is-5dB,the capture probability reaches 99%,and when SNR is-2dB,the accuracy of frequency offset estimation is NRMSE?10-2.When SNR is-3 dB,the capture probability reaches 99%,and when SNR is greater than 0dB,the NRMSE accuracy of frequency offset estimation remains in the range of 1%-2%.It shows that the timing synchronization algorithm can keep reliable timing performance under low SNR,and the accuracy of frequency offset estimation can meet the requirements of system design.Thirdly,the channel estimation technique of high-speed OFDM communication link is studied.Firstly,according to the channel model of the system,a time-frequency twodimensional pilot pattern suitable for the system is designed.Then,based on the pilot pattern,an LS channel estimation algorithm based on multi-domain noise reduction is proposed.The noise can be filtered through the cascade of frequency-domain interpolation and time-frequency interpolation with time-domain denoising and transform-domain denoising.Compared with the traditional LS channel estimation,it can provide about 0.5dB performance optimization.The simulation results show that the proposed algorithm can meet the requirements of the system under the channel model.Fourthly,based on Xilinx XCV7690T chip FPGA hardware platform,the transceiver implementation structure of high-speed OFDM communication link is designed.The realization methods of key modules in transmitter and receiver are introduced respectively,and the simulation description of Modelsim is given to verify the correctness of the design.Finally,the overall resource consumption of single link is given,indicating that the resource consumption meets the requirements of the system.Finally,the test system of high-speed OFDM communication link is built,and the synchronous measurement and single link self-loopback measurement are completed,which verifies that the FPGA realization results meet the requirements of system throughput and completes the high-speed OFDM communication link that meets the performance requirements.