基于广义观测器实现混沌系统的同步及信息传输

将保密通信问题看成是信息信号同步问题,从全新的角度提出了一种基于广义观测器的保密通信系统.首先在不改变混沌发送系统的混沌特性的前提下,将信息信号注入到混沌发送系统中,并将其看作系统的状态量;然后在接收端设计广义观测器;最后根据发送端传来的隐藏有信息信号的混沌输出信号同步出混沌系统的状态和信息信号.此方法不需要单独设计加密解密算法,而是将收发端混沌系统的同步与信息传输用同步方法一次实现.对系统的仿真证明了该方法的有效性.     

一种超混沌混合保密通信方案

本文将超混沌系统单变量单向耦合同步方法与两信道保密通信方案相结合，给出了一种双信道超混沌混合保密通信方案。发送端利用超混沌振荡器的一个或多个状态产生混沌密钥和遮掩信号，对信息信号先加密再遮掩，获得加密信号后使用一个信道传输；利用另一信道传输实现超混沌系统同步的单变量同步信号。接收端基于单变量单向耦合同步方法获得解密同步信号，实现信息信号高信噪比恢复。仿真结果表明了方案的有效性。     

基于多广义函数混沌同步的数字信号传输方案

讨论的是混沌保密通信问题。在多广义混沌同步和间歇偶合思想基础上提出了一种数字信号传输方案。在信号传输过程中，每个信号周期被分为两部分Tl，T2，分别用于实现同步和信号解调。通过随机选择广义函数和T1，T2的大小，大大提高了信息传输的安全性能。分析了T1，T2与安全性能和信息解调精度的关系。数值仿真表明效果良好。     

二进制混沌键控信号的最佳解调

本文通过对二进制混沌键控（２ＣＳＫ）系统同步误差信号的分析，提出２ＣＳＫ的最佳解调方案，同时给出了以Ｌｏｒｅｎｚ电路为例的计算机模拟结果。     

基于MATLAB/Simulink混沌信号的2FSK调制解调仿真

构建基于MATLAB/Simulink的2FSK调制解调仿真系统;分析混沌信号的特征机理,针对混沌正弦波信号调制与解调,使其运行的仿真波形与随机正弦波一致,验证此仿真系统针对混沌信号的正确性。     

一个混沌保密通信方案的改进

对文献[1]中的一个方案作了改进。用混沌映射信号作保密通信系统的调制载波,对待加密传输的信息信号进行调制,不需要用其它混沌同步方法,利用模运算在接收端直接完成混沌载波的恢复,从而恢复信息信号;为了更好地隐匿信息信号特征,借鉴混沌掩盖对信息信号幅度进行限制,使密文完全随机化。仿真结果表明:该加密系统加密效果好,且能抵御密码分析。     

一种应用粒子滤波器实现混沌通信的方法

该文研究应用粒子滤波器实现混沌通信的问题。组合信号建模技术,提出了一种基于粒子滤波器的实现方法。在发送端,采用加性混沌掩盖或乘性混沌掩盖将信息符号调制在混沌信号上;在接收端,应用粒子滤波器估计信息符号,进而实现混沌通信。仿真结果表明,当信息符号为二进制编码和M进制编码时,基于两种混沌掩盖的通信方案,粒子滤波器均能较好地从噪声混沌信号中恢复信息的编码值;与无先导卡尔曼滤波器相比,前者具有较低的误码率。此外,对比两种混沌通信方案,基于粒子滤波器的加性混沌掩盖通信系统在较高的Eb/N0下的通信性能接近BPSK,具有较低的误码率。     

一种新的混沌键控方案——分段移位混沌键控

为了进一步提高混沌通信系统的数据传输率,提出了一种新的混沌键控方案——分段移位混沌键控SSCSK,它是一种多进制调制方案。将SSCSK中的参考信号等分成M个信号段,根据传送的M进制数字码元,将M个信号段循环左移n（0≤n〈M）段,即形成信息携带信号。通过对其误码性能进行仿真分析可知,在相同的误比特率条件下,在信噪比要求上,二进制SSCSK比DCSK方案大约小3dB,四进制SSCSK的误比特率与DCSK方案接近,在混沌信号长度相同的条件下,四进制SSCSK的信息传输速率比DCSK提高了1倍。     

基于间歇耦合和广义混沌同步的数字信号传输方案

该文讨论了一种基于间歇耦合思想和广义混沌同步的保密通信方案。在这种数字信号传输过程中,每个信号周期被分为两部分T1,T2,分别用于实现同步和信号提取,分析了T1,T2与安全性能和信息解调精度的关系。数值仿真表明效果良好。     

基于混沌同步信号自适应传输的数字音频加密

利用混沌同步进行加密是当前信息安全的一个热门研究领域,它不但具有良好的实时性,而且可以有效地避免混沌密钥序列的周期性,其主要难题是如何传输混沌同步信号。提出一种数字音频的混沌加密方案,通过把音频信号的冗余信息自适应地替换成混沌同步信息,从而有效地解决了混沌同步信号的传输问题,并在解密时获得容许误差范围内的混沌同步,进而恢复出密钥序列进行解密,最后将丢失的冗余音频恢复得到最终解密音频。最后以二维超混沌映射为例,通过数值仿真说明该方案的有效性。     

Generalized correlation-delay-shift-keying scheme for noncoherent chaos-based communication systems

In this paper, we propose a generalized correlation-delay-shift-keying (GCDSK) scheme for noncoherent chaos-based communications. In the proposed scheme, several delayed versions of a chaotic signal are first produced. Some of them will be modulated by the binary data to be transmitted. The delayed signals will then be added to the original chaotic signal and transmitted. At the receiver, a simple correlator-type detector is employed to decode the binary symbols. The approximate bit error rate (BER) of the GCDSK scheme is derived analytically based on Gaussian approximation. Simulations are performed and compared with the noncoherent correlation-delay-shift-keying (CDSK) and differential chaos-shift-keying (DCSK) modulation schemes. The effects of the spreading factor, length of delay, and the number of delay units on the BER are fully studied. It is found that GCDSK can achieve better BER performance than DCSK under reasonable bit-energy-to-noise-power-spectral-density ratios.     

Synchronized chaotic mode hopping in DBR lasers with delayedopto-electric feedback

We propose and demonstrate a scheme for generating synchronized chaotic mode hopping in two wavelength-tunable lasers. Chaotic mode hopping resulting in large hops in wavelength is induced by delayed feedback of an electrical signal proportional to the intensity of the laser output which passes through an optical filter. Mode hopping among up to 11 modes was experimentally observed and optical signals in each wavelength band show a different on-off modulation time series. Analysis of the time series indicates high dimensionality. By using a unidirectional coupling method that injects part of the output of one laser into another, we can synchronize the chaotic mode hopping of two separate lasers and obtain synchronized chaotic on-off modulation patterns in multiple corresponding wavelength bands. The robustness of the synchronization with respect to the parameter mismatch and the effects of the coupling strength are investigated. The chaotic mode hopping dynamics and synchronization are well described with a numerical model that includes the characteristics of the laser tuning and the filter transmission. A multiplexed data transmission scheme using chaotic carriers is proposed and experiments demonstrate that multiple messages can be simultaneously recovered when chaos synchronization is achieved     

基于非线性控制器设计的离散混沌系统同步方法

在混沌通信系统工程化过程中,要求实时信号接收处理,实现收发两端系统的快速同步。为解决该问题,提出了以非线性控制器设计为基础的快速同步方案。针对离散混沌系统,采用Lyapunov函数同步法判定准则和反馈同步原理,合理设计了响应系统中的非线性控制器。仿真结果表明,同步误差可快速地稳定于零点,验证了该快速同步方法的正确性和有效性。     

简单分段线性混沌系统与SETMOS混沌系统的自适应广义同步

研究了基于SETMOS构成的、参数未知的类双涡卷混沌系统与结构不同的简单分段线性混沌系统的广义自适应同步方法。通过分析混沌系统的特点和广义同步的定义,基于李雅普诺夫稳定性理论,提出了一种新颖的、结构简单的自适应控制器和参数更新律,来实现不同结构、驱动系统参数未知的混沌系统的广义同步。这种方法还可以应用于不同结构或相同结构的其他同步问题,如自适应广义反同步等,应用范围较广。仿真结果进一步证实了该方法的有效性和可行性。     

在线混沌聊天保密通信研究

利用离散混沌映射进行信息的加解密,设计并实现了一个网络在线文字聊天保密通信系统,它不仅提供了一个实时通信平台,而且也保证了通信的保密性。系统采用倾斜帐篷映射,通过密钥同步方案,信息被实时加密后经TCP协议传输;而且由于混沌映射具有类随机特性及初值敏感性,传输的信息很难被破译,保密性较强。     

A Near-Optical Noncoherent Chaos-Based Communication Scheme

In this paper we introduce a method for improving the performance of noncoherent chaos-based communication systems. This method involves transforming chaotic signals into predefined patterns according to the relative magnitudes of the signal samples. First, for large spreading factors, the transformation leads to a large correlation between two different chaotic signals having the same distribution. This property can be used to recover the information in a noncoherent system. If the chaotic map and the transformation function are known, we can generate another chaotic signal to construct the reference signal for use in the correlator. In this scheme, both the synchronization circuit and the referencetransmission are not required. This scheme is referred to as the near-optimal noncoherent (NON) scheme. Second, for small spreading factors where high autocorrelation of the transmitted signals cannot be achieved, we propose a near-optimal noncoherent scheme with transmitted reference (NON-TR). For comparison, the corresponding performance bound using coherent detection is also given. This reference scheme is called the nearoptimal coherent (NOC) scheme. It can be shown that the NON scheme can achieve a similar performance as the chaos shift keying (CSK) system.     

Chaotic network synchronization with application to communications

Chaotic signals are widely exploited for the spread spectrum communication technique. Synchronization of a chaotic communication system between a single point and multiple points is recognized as an essential issue. In this paper, a chaotic network synchronization scheme is proposed to tackle the problem of multi‐access synchronization. The proposed synchronization scheme enables the realization of a fast synchronization of multiple chaotic systems. In this paper, the proposed system is validated by application to direct‐sequence (DS) spread spectrum communication (SSC) with code division multiple access (CDMA). Promising results were obtained on the applications of speech, characters and image communications. The obtained results indicate that the proposed SSC is effective and reliable even under the situations of a noisy channel, and multi‐path interference. Copyright © 2001 John Wiley & Sons, Ltd.