一种改进的DCSK保密图像传输方案

差分混沌键控(DCSK)采用非相干解调技术,不必在接收端生成混沌同步信号,结构简单,并具有很好的抗噪性能,但保密性不足,较易破解.针对DCSK保密性差的问题,提出了一种改进的DCSK方案,在保证其性能的同时大大提高保密性.且对此系统进行了深入的理论分析,对误码率、扩频系数和信噪比之间的关系进行了深入研究,并将其运用到图像保密传输中,通过仿真验证该方案的可行性.仿真结果表明,改进的DCSK系统在误码性能和保密性上都较原系统有极大提高,因此对实际应用具有重大意义.     

一种新型FM-DCSK保密通信系统

为解决DCSK系统中混沌信号比特能量的不恒定会引起估计干扰从而造成误码率下降,同时该系统的传输速率较低,保密性较差这一问题.提出FM调制与改进型的DCSK系统相结合的方法,通过使用FM调制使混沌信号能量保持恒定从而提高了系统误码性能,同时结合使用两条信道的改进型DCSK的方案进一步提高系统传输效率以及系统安全性能.最后通过理论分析与仿真实验结果比较证明了改进后的系统相关性能得到极大提高.     

一种新的混沌数字保密通信实现方案

针对差分混沌键控（DCSK）的保密性低,数据传输速率不高等缺点,这里设计并研究了一种新的混沌键控调制方式—调频相关延迟键控（FM-CDSK）通信方案,该方案同时兼具CDSK和FM-DCSK的优点。通过仿真分析验证了该系统在数据传输速率和保密性等方面较DCSK和CDSK都有所提高,传输速率更是比原有键控方式提高了2倍,并且利用该混沌调制方式很好的实现了图像信号的保密传输,验证了该系统在数字保密通信中的可实现性。     

一种改进型DCSK保密通信系统性能分析

差分混沌键控(DCSK)的输出信号具有固有的抗噪声以及宽频特性,由于其采用非相干解调技术,不必在收发两端建立同步,相比传统通信系统有很多优势。但其传输速率较低、保密性差。针对上述问题,提出一种改进型DCSK保密通信系统。该系统将信息分散于两个正交信道中传输,不仅保证了传输速率而且提高了安全性。理论分析和仿真结果证明,改进型DCSK保密通信系统较原系统性能有极大的提高。     

新型的CD-DCSK混沌键控保密通信系统

针对现有混沌键控通信系统存在的数据传输速率低性、安全性差等问题,提出一种新型的混沌键控通信系统——CD-DCSK(相关延迟—差分混沌键控),并对该系统的通信性能进行了深入地仿真分析.验证了改进的CD-DCSK同时兼具CDSK(相关延迟键控)保密性高和DCSK误码率低的优点,并且系统的数据传输速率更是提高到了原有键控方式的2倍.同时利用该新型的键控系统很好地实现了图像数据信号的保密传输,证明本系统在数字保密通信中的可实现性和高安全性.     

基于MIMO技术的DCSK通信方案的性能分析

基于MIMO技术的DCSK通信方案,主要就是指在对于MIMO通信技术优势应用的情况下,设计的通过DCSK通信控制实现的一种MIMO-DCSK混沌通信方案。其中,MIMO通信技术在通信实现过程中,能够在不增加通信信号带宽以及发射功率的条件下,通过在通信系统的信号发射端以及接收端,进行多个发送天线和接收天线的设置使用,来实现对于通信过程中信道衰落与噪声的控制。本文主要结合DCSK混沌通信系统的通信原理,在进行基于MIMO技术的DCSK通信方案设计实现与仿真分析情况下,实现对于基于MIMO技术的DCSK通信方案的性能分析与论述。     

瑞利衰落信道下DCSK系统性能分析

差分混沌键控(DCSK)是一种非相干调制技术,其输出信号具有固有的宽频特性。在各种混沌键控数字调制方案中,DCSK调制有着最优的抗噪声性能。文中在文献[4]的基础上,进一步分析了DCSK在瑞利衰落信道下的系统性能,推导出误码率公式,并通过计算机仿真实验验证了该理论分析的正确性。     

DCSK混沌数字调制方法及性能分析

文章在传统映射的基础上提出了改进的基于整数的Logistic映射,用于产生混沌序列,并介绍了以CSK为基础发展起来的DCSK混沌数字调制与解调的基本原理。运用matlab仿真软件分析了DCSK系统在高斯白噪声信道下的误码性能。实验得出,非相干DCSK具有较好的误码性能。     

一种新型正交相关延迟混沌开关键控系统

在相关延迟键控(CDSK)和混沌开关键控(COOK)这两种传统方案的基础上提出了一种新型的混沌键控方案——正交相关延迟混沌开关键控(OCD-COOK)。该方案结合了CDSK系统和COOK系统各自的特点，同时引入了一对简单的Walsh码序列，克服了CDSK系统误码性能差的缺点，具有比特误码率低、传输速率高、安全性好等优势。理论分析及仿真结果均表明，该系统的比特误码率低于CDSK和差分混沌键控(DCSK)，传输速率是DCSK的2倍，具有很好的实际应用价值。     

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。     

Performance Analysis and Optimization of Multi-User Differential Chaos-Shift Keying Communication Systems

Bit-error rate (BER) performance of a generalized multi-user differential chaos-shift-keying (DCSK) digital communication system is analyzed and optimized in this paper using baseband models. The generalized version of DSCK involves use of multiple nonrepeating chaotic spreading segments and energy adjustments and allows considerable system optimization. Theoretical BER analysis of correlation decoders based on a mathematical two-stage exact conditional approach is given as the foundation of subsequent performance studies. The consequent fully theoretical BER result gives an odd-symmetric spreading map condition for the BER to be unaffected by the mix of transmitted bits. The basis of the theoretical result is used to improve on the traditional simple Gaussian approximation (SGA) approach to the calculation of BER; this is inaccurate because it does not recognise the chaotic dynamics of DCSK. To overcome this drawback, a dynamically improved Gaussian approximation (DIGA) is developed. The DIGA approach is compared with the SGA approach, with simulation results demonstrating its accuracy and efficiency, certainly for more than five to ten users. Not only does the DIGA approach provide a more accurate BER than the SGA approach, its simple form also makes optimization of the DCSK system practically possible. The BER lower bound for the multi-user DCSK system is deduced from the DIGA approach. It is shown how the parameters and structure of the multi-user DCSK communication system can be optimized to achieve this lower bound. The work gives an exact theoretical basis of DCSK and covers several aspects which have not been treated in earlier research or have been inexactly treated.     

通用差分混沌键控通信系统及其性能分析

在各种混沌通信方案中,差分混沌键控混沌采用了易于实现的非相干解调,因而成为了混沌超宽带通信研究的热点。文章基于传统差分混沌键控通信提出一种通用差分混沌键控通信系统,该系统包含了多种差分混沌键控通信系统。文中理论分析了该系统中每比特采样点数、每符号比特数和信号占空比三个参数对于系统性能的影响,通过仿真证明了理论分析的正确性,最后分析了仿真和理论分析差异产生的原因。     

Non-coherent UWB Radio for Low-rate WPAN Applications: A Chaotic Approach

The requirements of low cost, low power and longer operation range for low-rate wireless personal area network (LR-WPAN) applications has driven the utilization of non linear communication approach. In this paper, a combined ultra-wideband (UWB) and chaotic communication technologies is proposed to meet these challenging demands. Among the candidates, the differential chaos shift keying (DCSK) modulation appears to be a very promising solution. The DCSK is a family of transmit reference (TR) system where a correlator based receiver is used to demodulate the received signal. However, this is not very well understood in the literature and therefore we will exemplify this issue in terms of noise performance. Furthermore, the feasibility study of the proposed DCSK is presented through the scalability and link budget analysis in two different operation modes. The system performance in both additive white Gaussian noise (AWGN) channel and standardized IEEE 802.15.4a UWB multipath channels are provided in order to further demonstrate the capability of the proposed system.     

A subspace theory for differential chaos-shift keying

In this brief, we introduce a subspace theory for differential chaos-shift keying (DCSK) systems. We show that DCSK systems operate by transmission of chaotic signals residing in a low-dimensional subspace. The subspace formalism of DCSK schemes leads to the derivation of useful subspace detectors that can be applied to decode the DCSK signal for various types of channels. Closed form expressions for the bit error rate is derived for an M-ary FM-version of DCSK, under the assumption of orthogonal subspace generating vectors. Numerical simulations demonstrate that the proposed subspace detector in general outperforms the conventional correlation detector for DCSK.     

BER performance enhancement for secure wireless communication systems based on DCSK-MIMO techniques under Rayleigh fading channel

There has been a growing interest in the use of chaotic techniques for enabling secure communication in recent years. This need has been motivated by the emergence of a number of wireless services which require the channel to provide very low bit error rates (BER) along with information security. As more and more information is transacted over wireless media, there has been increasing criminal activity directed against such systems. This paper investigates the feasibility of using chaotic communications over Multiple-Input-Multiple-Output (MIMO) channels. We have studied the performance of differential chaos shift keying (DCSK) with 2×2 Alamouti scheme and 2×1 Alamouti scheme for different chaotic maps over additive white Gaussian noise (AWGN) and channels disturbed by Rayleigh fading. Both the inherently wideband DCSK modulation and the space-time block code (STBC) are techniques that can mitigate the effect of multipath fading. The use of these schemes allows us to enhance security without degrading the BER performance for Rayleigh fading channels. We have employed an exact method to analyze the performances of DCSK communication system over fading channel. Our simulations indicate that the combination of the STC and tent map provides the best BER performance in addition to security when compared to the choice of other maps. Hence, this study shows that the use of these schemes can allow the user to enhance security without degrading the BER performance while communicating over these channels.     

DCSK通信系统中的一种LS-SVM降噪方法

本文提出了基于最小二乘支撑矢量机(LS-SVM)学习算法的一种DCSK混沌通信系统降噪方法。在发信端混沌信号的动力学特性是已知的情况下,设定接收信号为训练样本集,利用LS-SVM的非线性处理能力对接收信号进行估计,从而优化接收的混沌信号,达到降噪的目的。仿真结果表明,优化后的系统误码率(BER)性能得到改善。     

Chaotic communications with correlator receivers: theory and performance limits

This paper provides a review of the principles of chaotic digital communications using correlator receivers. Modulation schemes using one and two chaotic basis functions, as well as coherent and noncoherent correlation receivers, are discussed. The performance of differential chaos shift keying (DCSK) in multipath channels is characterized. Results are presented for DCSK with multiuser capability and multiple bits per symbol.     

一种新的跳时多址DCSK系统设计与分析

常见差分混沌键控(DCSK)系统的多址方案存在两个问题,首先所有用户共享同一时隙,只能利用混沌信号的低互相关性来降低多址干扰。其次发送的参考信号和数据信号并不相同或相反,破坏了DCSK系统的良好抗多径性。该文提出了DCSK系统一种新颖的跳时多址方式。该方式给每个用户分配不同的伪随机跳时码,根据跳时码参考信号和数据信号进行相同量的跳时。从理论上给出了多址系统在加性高斯白噪声信道中的误码率解析式。分析和仿真表明该跳时多址方式可以很好地解决上述两个问题,而且具有更低的误码率。