【作者】 田金超；

【导师】 张兴周；

【作者基本信息】 哈尔滨工程大学 ， 信号与信息处理， 2008， 博士

【摘要】 混沌保密通信是非线性动力学与通信技术的交叉学科,利用混沌的非线性以及对初值和系统参数的敏感性等特性,使得被调制的信息很难被截获和破译,从而提高通信系统的保密性。与传统的信息加密不同的是,目前开发的混沌保密通信系统不需要单独的传输密匙(公匙),而是将混沌信号作为传输信息的一部分进行传输,从一定程度上降低了加密系统的复杂性,可靠性大大提高,然而引进的混沌信号又减小了信息被破译的可能性。随着混沌研究的深入,越来越多的混沌保密通信系统被研发出来,比如混沌键控(CSK),混沌差分调制(DCSK),频域混沌差分调制(FM-DCSK),以及最近被提出来的正交混沌差分键控(QCSK)等等。本论文以正交混沌调幅通信机制的构建与分析为主题,从以下4个方面进行了研究和探讨:一、构建了正交混沌调幅通信机制。1)设计了正交混沌信号发生器,分析了正交混沌信号的特性;2)分忻目前最新的混沌调制通信系统结构——正交混沌键控系统(QCSK,quadrature chaos shift key),指出由于其结构的原因导致有用信息的传输效率较低,且接收端的解调误码率较高;3)以QCSK系统结构为蓝本,构建出一种基于混沌载波的正交调幅机制(QCAM,quadrature chaos amplitude modulation),通过分析其传输有用信息的效率是QCSK的2倍,由于在接收端的解调方式使用的载波同步相关检测,使得解调误码率较QCSK有所提高;4)分析高斯白噪声信道以及Rayleigh衰落信道对QCAM系统的影响。二、改进了局部投影算法,并对QCAM传输信号中的噪声进行抑制。1)分析局部投影算法的原理;2)针对原始局部投影算法中Q值的选取问题提出了一种改进的局部投影算法;3)将改进前后的局部投影算法应用到QCAM系统传输信号的噪声抑制中,抑制后的接收信号解调后的系统误码率性能有所改善,且改进后的局部投影算法改善QCAM系统误码率的效果比原算法明显。三、设计了QCAM通信系统的同步方案。1)分析本论文所利用的第2类混沌系统同步的充分条件;2)提出一种基于控制反馈的混沌系统网同步方案,该方案不仅使得耦合系统能够在很短的时间内达到同步,而且稳定可靠,仿真结果表明耦合混沌系统初始值的敏感性变弱;3)分析取模同步的原始模型的结构原理;4)根据QCAM系统结构的特点,结合原始取模变换方案改进出一种适用于QCAM系统的同步方案,并从误差分析和保密性两个方面对改进后的方案进行分析。四、研究了QCAM系统的信道盲均衡算法。1)介绍盲均衡算法的原理及其数学模型;2)研究基于粒子滤波(PF,Particle filter)算法的QCAM信道盲均衡,能较好的估计QCAM系统中经过混沌正交调制后信号的统计特性,仿真结果表明,该算法能够很好的解调有用信息;3)研究基于UKF算法(UKF,Unscented Kalman Filter)的QCAM信道盲均衡,通过对4个不同信道系数的衰弱信道进行800次的迭代后表明,盲均衡后的信道系数能够非常紧密的跟踪真实值。更多还原

【Abstract】 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.更多还原