Research On Chaotic Secure Communication Applied To Software Radio

Chaos is produced by the system's internal random property, a non-random movement while it looks like random. The one of its basic characteristics is that the system is highly sensitive to original condition. So chaos has its native value in secure communication. The study of digital chaotic communication has become a hotspot problem in info-sci field. The purpose of this thesis is to seek valid digital chaotic communication model according to software radio character. The model is realized by synchronous or asynchronous method and the results are analyzed.This thesis carries through the following aspects of study:1) In allusion to the basic structure of software radio system, the principle of the software radio is introduced and the feasibility of the encryption link is illuminated. In addition, the thesis confirm the digital chaos' significance as a communication encrypting method in software radio system. Then an audio-simulation of direct sampling orthogonal DSB is put forward.2) Some kinds of prevalent chaotic modulation technology are introduced. In allusion to prospective FM-DCSK model, an asynchronous demodulation scheme is presented. The scheme solves the synchronous problem in demodulation by matching of the code elementposition, which plays down the system requirement. The method can demodulate original information even if some noise is added to the system. Compared with the demodulation results of ideal synchronization, the simulation results prove the efficiency and practicality of this method.3) With the synchronizing model carried out by driven-parameter method, a new scheme of digital chaotic communication is proposed., which improves the traditional chaotic encrypting method. Public key and private key are separated. Attacker can merely get the public key and only authoritative receiver can obtain the private key to decode the information. According to the scheme, the coding and decoding circuit of digital chaotic communication system based on ARM microprocessor is designed and the results are satisfactory.4) Finally this paper presents the 32-bit ARM-core microprocessor , which is applied in hardware implementation. To avoid chaotic degree of accuracy problem, high accuracy processor should be choose besides enhancing the system's structure. ARM-core microprocessor has high accuracy and efficiency, which can be used to improve the random character of digital chaos. Surplus operational resources in the processor can be spent on the other parts of the software radio system.