Research And Verification Of Key Technology Of UAV Variable Rate HD Image Transmission Waveform

High definition(HD)video and image transmission is one of the main services in communication between Unmanned Aerial Vehicle(UAV)and ground station,which is widely used in military and civilian fields.UAV needs to maintain real-time,stable transmission during fast movement while switching the transmission rate according to the channel environment.In this paper,the research and verification of key technologies such as timing synchronization,single-carrier frequency domain equalization and error correction coding in UAV variable-rate HD image transmission waveforms are carried out.The main work of this thesis is as follows:Firstly,the function and performance requirements of the UAV's variable-speed HD image transmission waveform are demonstrated in detail,and the function division and working mode of the waveform are carried out.We analyze the free space propagation loss when the UAV communicates with the ground station,and the signal-to-noise ratio of the received signal at the required distance.Then we expound the influence of frequency offset on synchronous correlation peak and demodulation signal-to-noise ratio,and give the actual SNR curve of demodulated signal when the SNR at receiver keep fixed.Finally we analyze the influence of frame synchronization offset on the receiving performance of SC-FDE system which provides theoretical basis for waveform design.Secondly,a waveform scheme with high transmission rate,anti-Doppler shift,and high reliability is designed.We present the structure of the transmitter and receiver,and propose waveform schemes of transmission rate at 2Mbps,4Mbps,and 8Mbps.Then we expound the detailed design of each signal processing unit,and study the key techniques in baseband signal processing systematically,including frame synchronization and symbol synchronization,single carrier frequency domain equalization and LDPC coding and decoding.Finally we complete link performance simulation,including carrier synchronization,frame synchronization,SNR estimation and bit error rate performance,when the decoding iteration is 50 times,the bit error rate performance is only 0.2dB worse than the theoretical reference.Thirdly,the key techniques for image transmission waveforms are implemented and validated on software defined radio platforms.We introduce the overall structure of the hardware platform of the waveform;.Then we design the interface and implementation of the key module,including frame synchronization and symbol synchronization module,frequency domain equalization module and LDPC coding code module.Finally we test the spectrum,frame synchronization and block error rate performance of the transmitted signal in laboratory environment,when the block error rate reaches 10-5,the SNR required for waveform transmission is 1.5?3dB worse than software simulation.The paper proposes a variable-rate high-definition waveform transmission scheme based on SC-FDE technique,and completes the design and implementation of key techniques,which has certain engineering value.