Research On Anti-jamming Technology Of UAV Data Link Based On Cognitive Frequency Hopping

The war in the 21 st century is an informationized war.The UAV data link system serves as the "lifeline" for the ground control base station to transmit control instructions to the UAV and the UAV to transmit intelligence information to the ground control base station.Its anti-jamming ability is very important.Frequency hopping technology is widely used in data link anti-jamming technology because of its good anti-jamming and anti-interception capabilities.However,it selects frequency hopping frequency points in a fixed frequency concentration,and lacks the ability to actively avoid jamming.Cognitive frequency hopping technology combines the idea of cognitive radio with frequency hopping technology,which can recognize the surrounding spectrum environment and intelligently adjust the characteristics of its own communication parameters to achieve active avoidance of jamming.Therefore,consider applying cognitive frequency hopping technology to the UAV data link system in order to improve its anti-jamming performance.Therefore,it is of great significance to study the anti-jamming technology of UAV data link based on cognitive frequency hopping.The main contents of this research are as follows:Firstly,analyze the UAV data link jamming and anti-jamming technology.Explain the suppressive jamming commonly encountered in UAV data links,including broadband noise jamming,partial band noise jamming,tone jamming and linear frequency modulation jamming,and analyze its time domain and frequency domain characteristics.Using Link-16 as a model,research the anti-jamming technology used in the data link system,including channel coding,modulation,direct sequence spread spectrum technology and frequency hopping technology.In response to the current “blind hopping” problem of frequency hopping technology in data link systems,it is proposed to apply cognitive frequency hopping technology to data link systems to achieve active avoidance of jamming,adaptive selection of communication strategies,and improvement of spectrum resource utilization.So as to realize the improvement of the anti-jamming ability of the UAV data link.Secondly,study the jamming detection and recognition technology in the cognitive frequency hopping system.Aiming at the problem of detecting the presence of interference in the data link cognitive frequency hopping system,research the energy detection algorithm,and simulate its detection performance.The adaptive update of the cognitive frequency hopping frequency set is actually the screening of jamming frequency points.In order to obtain clean frequency points,the single-threshold and double-threshold Forward Consecutive Mean Excision（FCME）algorithms are studied,and the detection performance of the two algorithms on different jamming signal types is simulated and analyzed.In order to quickly and accurately identify the type of jamming signal,the jamming recognition algorithm based on fractal dimension is studied,and the fractal box dimension and LZ complexity of the jamming signal are extracted to form a two-dimensional feature vector.Based on its poor recognition performance under low jamming-to-noise ratio,a two-dimensional feature recognition algorithm based on Sevcik fractal dimension and energy concentration is proposed to evaluate the recognition rate of different jamming signals.Finally,evaluate the anti-jamming performance of the UAV data link system based on cognitive frequency hopping.Using Link-16 as a model,using Reed Solomon（RS）coding,Cyclic Code Shift Keying（CCSK）soft spread spectrum and Minimum Shift Keying（MSK）modulation,a UAV data link system model based on cognitive frequency hopping is established,and the workflow of the cognitive module is explained.Analyze the main functional modules of the frequency set adaptive update,frequency hopping pattern generation and frequency hopping synchronization in the cognitive frequency hopping system.Under the Nakagami-m channel model,when there is no jamming signal,simulate and analyze the bit error rate of the fading channel data link cognitive frequency hopping system with different degrees.When the jamming signal exists,the simulation analysis of the anti-jamming performance of the cognitive frequency hopping system in the presence of different jamming.And through the comparison with the conventional frequency hopping system,it illustrates the superiority of cognitive frequency hopping technology and its advantages in data link anti-jamming.