Research On Anti-jamming And Anti-interception Communication Technology Based On Differential Frequency Hopping

Differential Frequency Hopping(DFH)transmits data information through the correlation of adjacent frequencies.DFH enables data to be transmitted at high speed,and the speed of hopping is improved,which means that the resident time of each jump is shortened,which greatly improves the anti-tracking ability of systems.In this thesis,first we study the frequency transfer function(FTF)that has important influence on the anti-interception property of DFH systems,and we propose its improved method.Then a hybrid spread spectrum system of DFH and Direct Sequence Spread Spectrum(DSSS)systems or M-ary spread spectrum systems are proposed,and we simulate and analyze the bit error rate(BER)performance of the hybrid system.Finally,the anti-jamming and anti-interception of the DFH systems and the hybrid systems are studied.The main work and achievements of this thesis are as follows:1.In order to solve the problem that two-dimensional continuity of traditional FTF is poor which results in poor anti-interception and safety of DFH systems,in this thesis,a FTF design based on the scrambler algorithm is proposed,which theoretically proves that the frequency sequence generated by the algorithm satisfies the requirement of two-dimensional continuity test.The simulation results show that the two-dimensional continuity of the frequency sequence generated by the improved algorithm is good,at the same time the antiinterception and security of the DFH systems are improved,and the BER performance of the receiver is not reduced.The improved method is simple,effective and easy to implement.2.Considering the direct sequence spread spectrum(DSSS)and M-ary spread spectrum have good anti-interference and anti-jamming performance.In this thesis,the combined hybrid systems of DFH and DSSS systems or M-ary spread spectrum systems are proposed.The simulation results show that the combined hybrid systems of DSSS systems or M-ary spread spectrum system significantly improves the BER performance of system.For the problem of high complexity of the hybrid system,this thesis proposes a method to reduce the complexity of systems using the special structure of convolutional code.The simulation results show that the reduction of complexity basically does not affect the system's BER performance.Using spectrum analysis,we can see that the anti-interception performance of the combined hybrid systems of DFH and DSSS systems is better than that of the DFH systems.The simulation verified the correctness of the analysis.3.The anti-interference performance of combined hybrid systems of DFH and DSSS systems or M-ary spread spectrum systems are analyzed.We simulate and compare the anti-jamming performance of the combined hybrid system of DFH and DSSS systems or M-ary spread spectrum systems.In this thesis,Analyzing the anti-intercept performance of DSSS systems and M-ary spread-spectrum systems using the blind detection methods is proposed.The simulation results show that the anti-intercept performance of the M-ary spread spectrum systems is better than that of the DSSS systems.Therefore,the combined hybrid systems of DFH and M-ary spread spectrum systems has better anti-interception performance than DFH and DSSS systems.