Research On Modulation And Demodulation Technology Of Chaotic Secure Communication System

With the development of chaos theory and communication technology, it interests many scholars to apply the chaos theory to communication. Over the past decade, much research effort has been devoted to the study of chaotic communication and great progress has been made. From analog chaotic communication to digital chaotic communication, several schemes have been proposed and studied. The anti-jamming capability and the data transmission rate of a communication system have a close relation with the modulation and demodulation schemes. In this paper it is concentrated on modulation and demodulation technology of chaotic secure communication system. And the main works and contributions are as follows:1. By systematically studying lots of references about chaotic application technology, the development of chaotic communication and the current status of chaos research are summarized in this paper. Several modulation schemes are described in brief.2. The principles of digital chaotic modulation, such as CSK, DCSK, and FM-DCSK, are explained in detail. The characteristics of those schemes are analyzed and compared by computer simulation. Their bit error rates in white Gaussian noise environment are special studied.3. By analyzing and comparing, the FM-DCSK has the optimal performance. But its transmission rate is lower, just half of the CSK. In this paper, a new chaotic modulation scheme—Amplitude Frequency Quadrature Chaos Shift Keying is proposed. The simulation results show that the efficiency of chaotic communication system is improved significantly, and the transmission data rate is three times of the FM-DCSK.4. With the scheme that proposed above, the performance of anti-white Gaussian noise, anti-multi-path interference and anti-multi-access interference are studied by computer simulation.5. In order to improve the bit error rate of the chaotic communication system, some improvements are made in the receiving process. Because the chaotic signals have the characteristics of randomness and low-power spectrum, the noise interference should not be neglected. In the receiver, the Kalman filter is used to reduce the noise interference. Then the filtered signals are demodulated by chaotic demodulation. By theoretical analysis and computer simulation, the approach is demonstrated to be feasible and practicable.