Study Of Hyperchaos Dynamical Properties With Application To Secure Communication

Chaos is a quasi-stochastic phenomenon appearing possibly in definite nonlinear dynamic systems. Chaotic motion is a complex nonlinear motion and the chaotic phenomenon has been observed in a lot of real systems. The dynamic properties of chaos signal such as ergodicity, aperiodic, uncorrelated, broadband, noise-like, deterministic and reproducible have been proved to be useful for secure communication. Hyperchaotic system has no less than two positive lyapunov exponents and more complicated dynamic behavior. So there are many advantages of hyperchaotic secure communication over normal chaotic communication such as higher security, bigger storage capacity and stronger robust and so on. Meanwhile digital noncoherent communication system is simply constructed, easily realized, needlessly synchronized and higher security than analogy communication system. Accordingly digital noncoherent hyperchaotic secure communication will be the study highlights in later days.Based on the hyperchaotic dynamic properties and its application to secure communication, the author has performed comprehensive research. First, the significance and purpose of this paper are illuminated and the basical theory of chaos and hyperchaos is surveyed.briefly. Next, dynamical properties of typical hyperchaotic systems are analyzed in detail. And then, the paper analyzes several chaotic digital secure communication schemes with good quality such as CSK, DCSK, CDSK, QCSK, and proceeds performance simulation and analysis.Then, this paper emphasize to study the performance of frequency modulated differential chaotic shift keying (FM-DCSK) system of hyperchaos such as Chua and Rossler system and then compares the performance of Rossler hyerchaotic system with Rossler chaotic system in FM-DCSK. The superiority of this hyperchaotic FM-DCSK communication system over lower dimensional chaotic FM-DCSK system is proved by theoretic analysis and Matlab simulation in the presence of AWGN channel, multi-path Rayleigh channel and multi-path Ricean channel respectively.At last, this paper high lights the performance of chaotic pulse position modulation (CPPM) secure communication system. To eliminate the disadvantage caused by error propagation, a novel communication strategy is introduced. This modified scheme gets the delay part out of the feedback loop from the modulator to avoid the possibility of system divergence and then removes the influence of information sequence on the dynamic properties of chaos. The proposed CPPM scheme is proved to increase the feasibility and security of this system without increasing the complexity by theoretic analysis, Matlab numerical simulation and Simulink.