Optimized Jamming Against Convolutional Code And Its Anti-Jamming Scheme

Convolutional code is still widely used in various communication systems and military communications of various countries due to its short length,simple encoding and decoding structure,and good error-correction performance.Under the background of cognitive electronic warfare,this thesis proposes an optimized pulse jamming scheme for convolutional codes.Then we designs corresponding effective anti-jamming schemes for the optimized jamming scheme.Finally,this thesis verifies the performance of the above jamming and anti-jamming schemes on the USRP platform.The main work and contributions of this thesis are as follows:This thesis proposes an optimized jamming scheme for convolutional codes is proposed.First,this thesis studies the bit error rate of the binary signal and the multi-ary signal in the AWGN channel with correlated jamming,then derives and simulates the waveform with good jamming performance to the above signals by using the convex optimization method to analyze the bit error rate formula.Next,the thesis derives the probability distribution of different event lengths and error correction capabilities of convolutional codes in the decoding path according to the Viterbi decoding algorithm formula,and designs the jamming pulse length based on the probability distribution.Then,two design methods for the duty cycle of the jamming pulse are proposed.One is to use the bit error rate formula under the jamming to solve the jamming pulse duty cycle to maximize the bit error rate before decoding.The other method is to simulate the link of the whole communication system,aiming at maximizing the bit error rate of the receiver,and finding out the best jamming pulse duty cycle by exhausting different duty cycle.After obtaining the parameters of the jamming waveform,pulse length and duty cycle,the performance of the convolutional code optimization jamming scheme is simulated and verified,and compared with the traditional digital modulation jamming and noise jamming.The simulation results show that the bit error rate caused by convolutional code optimization jamming increases obviously when the mean jamming to signal ratio is the same.Based on the modulation method of convolution code optimization jamming and error correction capability pertinence,this thesis designed several simple and effective anti-jamming scheme,such as reducing the modulation order,adding different interleaving methods,and reducing the coding rate.Then we compared the anti-jamming effects of different interleaving methods,the storage space consumed,and the system delay.At last,the bit error rate curve after anti-jamming scheme is simulated.Finally,this thesis uses the USRP-2952 R from NI and the E8267 D vector signal source from Agilent to build the communication system of convolutional code optimization jamming and anti-jamming scheme.Then we measured the performance of the jamming and anti-jamming scheme.At last,the actual measured value is compared with the simulation value to verify the effectiveness of the proposed jamming and antijamming scheme.