Design And Implementation Of Chaotic Multi-tone Covert Communication Transmitter

Due to the development and progress of high-speed computing technology,the schemes for the hidden transmission of information in the existing communication system are facing a huge risk of being intercepted and deciphered.Therefore,this article starts from changing the method of current communication modulation and demodulation,and introduces a new covert communication modulation technology based on multi-value mapping,which is called chaotic multi-tone modulation technology.It expresses the same baseband information with different multi-tone frequency groups,and combines frequency-hopping communication and multi-tone communication technology to accomplish signal modulation.The obtained chaotic multi-tone signal has the characteristics of information concealment ability and anti-demodulation of non-cooperative parties,so as to realize the purpose of concealment communication.This paper mainly studies the method of realizing the new modulation mode on the hardware,conducts a detailed study on the design of the transmitter system,and gives the implementation process of FPGA-based transmitter hardware.Finally,the test experiments to verify the correctness of the transmitter system design are given.The transmitter system presented in this paper is mainly composed of seven modules,which are data encryption module,channel coding module,chaotic multitone modulation module,synchronization module,D/A conversion module,and radio frequency modulation module.The data encryption module mainly encrypts the baseband symbols.The chaotic scrambling algorithm is used to scramble the position of the original baseband code and output it.The channel coding module mainly uses(7,4)Hamming encoding to correct binary data.The chaotic multi-tone modulation module mainly uses the chaotic sequence to determine the chaotic multi-tone frequency group,and uses the mathematical algorithm to complete the mapping between the scrambled and encoded data and the chaotic multi-tone frequency group.The synchronization module mainly generates the positive and negative chirp signals internally determined by the transceiver as the synchronization header before sending the chaotic multi-tone modulation signal.In this way,the time offset can be obtained by using two correlators at the receiving end,so that the system can be synchronized.The D/A conversion module uses the AD9767 chip to convert the digital signal output from the FPGA into an analog voltage signal to connect to the RF module at the back.The RF modulation module mainly modulates the baseband-modulated intermediate frequency signal to the high frequency so as to transmit the signal after the antenna receives it.The algorithm platform built by the transmitter system is mainly written by Verilog HDL language and implemented on Altera's FPGA development board.Modelsim simulation software and board-level verification are used to test the system and give verification results.After testing,the transmitter can transmit the chaotic multi-tone signals correctly and has good concealment performance,which has achieved the goal of this design.