Research On Digital Communication Systems Based On Coherent CSK Technology

With the booming development of the telecommunications and Internet technology transfer and exchange of information and more and more quickly, easily, but in an open network, how to ensure the security of information transmission is an important issue. In recent years some scholars want to use a random set of the carrier signal to send data, making the carrier signal in the encryption process is still similar to the action, it is not easy to transfer data from a third party was attacked (including theft or decrypt data and so on). Chaotic digital communication system is an extension of traditional communication systems, the biggest difference is the use of the chaotic carrier signal as a transmission signal, there is the initial value sensitive, difficult to predict trajectories and other characteristics will be applied to information transfer can be well kept confidential effect, coupled with the use of cryptography in the concept of public-key to prevent an eavesdropper's attack and invasion, did improve the security of communication systems.In this thesis, the chaotic digital communication schemes based on the concept of chaotic synchronization is proposed. The schemes contain some components:modulation and demodulation multiple access and channel fading effect. There are two strategies; a least square algorithm and conventional chaotic demodulator are used to achieve chaotic communication systems. The characteristic of chaotic and the technological of chaotic communication CSKare first introduced. Furthermore,two communication schemes the coherent CSKand coherent CSKof digital chaotic communication system are proposed in the thesis. A special point view of strategy of demodulator is used the concept of generalized chaoticsynchronization in different chaotic circuits, Lorenz system to drive Chua's circuit. Finally, some digital images are transited to test the system performances.On the other hand, the adaptive algorithm-LMS is designed to the channel equalizer to compensate the corrupted signals which are transmitted through fading channel.In this thesis, we not only achieved the numerical simulation but also transmit digital images in different communication schemes to verify proposed results. Finally, we expect to develop an adaptive and robust the chaotic communication systems in the future.