Chaotic Synchronization Communication Systems With Parametric Uncertainty And Time-delay

In secure communication, being synchronization between two chaotic systems is a new concept of secure communication. A chaos signal is a deterministic signal but has highly unpredictable and random nature. Its unique characteristics make it very attractive in the application area of secure communication. From 1990s, four generations of chaotic secure communication systems have been evolved. In the first three generations, the system uses the continuous signal to synchronize two chaotic systems. There are two problems in this way. The first one is that the whole system is in low security. The second one is the low efficiency of channel usage since the continuously transmitted synchronization signal uses a wider bandwidth comparable to that of the message signal. Then the researchers developed the fourth generation of chaotic secure communication system based on the theory of impulsive differential equations. The fourth generation uses the impulsive signals to synchronize the chaotic systems in the sender and receiver. Furthermore, the impulsive driving way is suitable for the digital communication system.In the fourth generation, security of the system still is the most important issue. There are two approaches to enhance the security of system. The first approach is to exploit hyperchaos-based secure communication systems, but such systems may introduce more difficulties to synchronization. The second approach is to combine conventional cryptographic schemes with a chaotic system, which uses low-dimensional chaos signal. Compare these two approaches, the second one is more economic while possesses a high security.Recently, there has been increasing interest in the synchronization of two chaotic systems and some significant results have been reported by researchers. In these results, a strong assumption that the two chaotic systems should be identical, i.e., without any parameter mismatch, is imposed. Clearly, it is impractical. In this thesis, pure impulsive synchronization is considered. We quantitatively establish a relationship between a pre-specified bound of the synchronization error and the length of impulsive intervals in the presence of both parametric uncertainties and mismatch between the two systems. Also, the quantization error problem is analyzed in this thesis. In the end, the thesis introduces the time delay problem when using impulsive synchronizing in the chaotic systems. This one is the advanced research topic in this area.The main works of the thesis are as follows:1. Introduce the basics of chaotic secure communication system and its evolution history. Propose a new chaotic secure communication system for simulation usage of our theory result.2. Describe the basic theories of impulsive differential equation. And discuss its application to impulsive synchronizing in the chaotic systems.3. Analysis the stability of the chaotic systems in the presence of both parametric uncertainties and system mismatch. Also give the stability result when quantization errors happened in the impulsive synchronization.4. Explore the delay problem in impulsive synchronization chaotic systems. And point out the research trend of the delay problem.