The Research And Implementation Of Physical Layer In UAV Communication System:Synchronization

Along with Unmanned Aerial Vehicle widely used in the military and civilian fields,the requirements of UAV communication system are becoming higher and higher.Nowadays,the amount of data that the UAV communication system needs to transmit is increasing,and at the same time,the requirements of real-time continue to improve.With the development of OFDM,more and more researchers have applied OFDM technology to UAV communication system and achieved good performance.However,due to the higher synchronization requirements of OFDM technology and the complexity of UAV channel,it is very important to study the synchronization technology based on UAV channel.This article will analyze the UAV channel and summrize the chacteristics of it.In this article,the classical OFDM synchronization technology is analyzed and simulated.According to the project requirements and UAV channel characteristics,this article choose an appropriate synchronization algorithm as the synchronization scheme for UAM communication system.In this article,three classical time-frequency joint synchronization algorithms are studied,including ML algorithm based on CP,Schmidl algorithm and Tufvesson algorithm.We focus on Schmidl algorithm and Tufvesson algorithm.The two algorithms are analyzed from the aspects of timing synchronization performance,frequency offset estimation range and variance.In addition,this article also analysed the computational complexity of the two algorithms.Then according to the characteristics of UAV channel and OFDM system index requirements,the Tufvesson algorithm is selected as the UAV OFDM system synchronization scheme after comprehensive consideration both performance and hardware resources,.Based on the chosen kind of design and UAV channel characteristics,this article builds a simulation model in MATLAB.The simulation results verify the effectiveness of the scheme.Furthermore,the FPGA implementation of UAV communication system receiver are introduced,including synchronization scheme selected above,OFDM demodulation module and OFDM symbol processing module.Because of the high data rate of the UAV communication system,this article elaborates the the control of data flow.Finally,the hardware test of the UAV communication is finished.The test results of the receiver sensitivity show that the reveiver has good sensitivity and is accordance with the expected design.