Study On The Key Technologies Of Building Quadrature Chaos Amplitude Modulation Communication Scheme

The chaos security communication was an interdisciplinary study betweened non-linear dynamics and communication, which used chaos non-linear characteristic and sensitive of the starting value and system parameters. As a result, it caused the information which was modulated very difficult to intercept and break, enhancemented communications system security. The most difference between the chaos communication and traditional information encryption was that the chaos security communication carried on the chaos signal as a part of transmission informations, thus reduced system complexity and enhanced reliability. Along with chaos communication research, more and more chaos security communication systems were researched and developed, such as the chaos shift key(CSK), the chaos difference shift key(DCSK), the frequency modulation chaos difference shift key(FM-DCSK), the quadrature chaos shift key(QCSK) which was raised recently and so on.This dissertation mainly expatiates on the analysis and design of quadrature chaos amplitude modulation scheme from the four aspects demonstrated as follows:Ⅰ. Designed the frame of quadrature chaos amplitude modulation communication system. 1) Quadrature chaos signal generator was designed and quadrature chaos signal performance was analysed. 2) The latest structure of chaos modulation communication system—quadrature chaos shift key (QCSK) was analyzed. Meanwhile, lower transmission efficiency of useful information and higher demodulated bit error rate (BER) at receiver resulted from its structure were emphasized. 3) Originated from QCSK system frame, a kind of quadrature chaos amplitude modulation (QCAM) system based on chaos carrier was carried out. Analysed the fact that transmission efficiency of useful information on it doubles QCSK, and because of the use of correlation detection at receiver higher demodulated bit error rate (BER) than QCSK was achieved. 4) Influence to QCAM system from Gaussian white noise channel and Rayleigh fading channel was analyzed.Ⅱ. Restrained noise infection to QCAM transmitted signal and improved Local Projection Algorithm'sprinciple. 1) Analyzed Local Projection Algorithm principle. 2) Proposed one kind of Improvement Local Projection Algorithm by investigating how to choose the Q value in original Local Projection Algorithm. 3) Applied the original and enhanced Local Projection Algorithms to the noise restraint in QCAM system transmission. It's clear that the demodulated signal bit error rate became negligible compared with original ones. Furthermore, the improvement Local Projection Algorithm can improve QCAM system performance evidently.Ⅲ. Designed one kind of QCAM communication system synchronization scheme. 1) Analyzed the second kind of chaos system synchronized sufficient condition used in this paper. 2) Proposed one kind of chaos system synchronization scheme based on control and feedback mechanism.This scheme not only make coupled system enter into synchronization quickly but also keep the system stable and reliable. The simulation result indicates that the sensibility of coupled chaotic system initial value became weak. 3) Analysed the structure and principle of mold synchronization primitive model. 4) Designed one kind of synchronization scheme that can be consistent with the structure characteristics of QCAM system and primitive mold transform scheme.Discussed the enhanced algorithm from the aspects of error analysis and privacy protection.Ⅳ. Research into the blind channel Equalization Algorithm in QCAM system. 1) Introduce the principle as well as the math model. 2) Investigate the blind channel QCAM system based on Particle filter (PF) Algorithm with the ability to estimate signal's statistical characteristics after chaos quadrature chaos modulation in QCAM system. Simulation result indicates that this algorithm can demodulate useful information well. 3) Investigate blind channel of QCAM system based on unscented kalman filter (UKF) and 800 times of iterative calculation in a fading channel with four different channel coefficients indicate that the channel coefficient after blind equalization can trace the true value closely.