混沌序列码实现方法及应用

以logitic混沌序列代替伪随机序列，引入软件无线电思想，实现了软件无线电混沌扩频通信系统。对随机产生的混沌序列进行优选，得到了性能优异的混沌序列，在不同信道条件下进行了系统仿真。结果表明，系统各个模块均能正常工作，优选混沌序列性能优于传统序列，是扩频序列的新选择。     

混沌扩频通信系统在多径Rayleigh衰落信道中的性能分析

本文研究了混沌直接扩频信号在多径Rayleigh衰落信道中传输时的抗多径干扰和多址干扰的特性。对于所给出的混沌扩频通信系统,当加入多径干扰和信道噪声时,给出了理论误码率与实际误码率的比较,数值结果表明在多径衰落信道中,混沌扩频通信系统抗多径干扰的性能很好;同时对混沌直接扩频信号的奇、偶互相关函数进行了计算,结果表明混沌扩频通信系统具有良好的抗多址干扰能力。     

基于混沌的扩频通信

针对混沌信号具有的随机性、宽带性、似噪声以及对初始条件的极端敏感性的特点，本文用混沌序列取代扩频通信系统中的伪随机码，在提出并实现一种混沌网络同步化法的基础上，实现了语音、文字和图像的码分多址的扩频通信。用Ｌｏｒｅｎｚ混沌系统对同步和通信的仿真结果表明了本文所述方法的有效性和可靠性。进一步指出了这种通信方式具有简便性和自然的保密性的优点。     

新的混沌扩频序列抗多址性能的Simulink仿真

针对混沌扩频通信中提升混沌码性能的问题,通过重构Bernoulli映射相空间,得到一种改进的Bernoulli混沌映射,计算证明该映射具有弱结构特性,并在Simulink平台搭建了多用户混沌直接扩频通信系统的仿真模型,并与原Bernoulli混沌序列的抗多址性能做了比较。Simulink动态仿真结果表明,改进后的混沌扩频序列具有较好的抗多址干扰能力。     

基于混沌的扩频通信系统及性能分析

指出了混沌扩频通信的特点及分类,分析了混沌扩频通信系统中的编码与解码问题.介绍了Logistic-Map数字混沌扩频通信系统的组成及原理,并对该系统误码率进行了计算机仿真分析与实际计算,比较两种方法的误码率值可知,对该系统性能分析的方法及解析表达是正确可行的.     

CNN混沌扩频通信系统的性能研究

本文把细胞神经网络（CNN）理论应用于混沌扩频通信系统（CSSS），研究了细胞神经网络实现脉冲式混沌同步的可行性，指出能否同步与同步脉冲的能量有关，而且用CNN产生了性能优良的二值和多值随机码，并对系统的抗多址和多径干扰的性能进行了研究。通信系统的仿真实验表明，CNN能够很好地应用于扩频通信系统。     

基于时空混沌的CPSK多用户扩频通信

传统的混沌扩频（CDSS）是利用混沌序列量化、编码后产生的0、1序列作为扩频码,来实现频谱展宽。另外,由于混沌序列本身的宽频特性,一些传统的混沌数字调制技术也可被用于扩频通信系统的设计。在单向耦合映像格子（OCML）时空混沌模型同步的基础上,直接利用混沌相位键控（CPSK）调制技术构建了一个多用户扩频通信系统。该模型为每个用户分配一个OCML时空混沌模型,为了更好地利用时空混沌系统的时间与空间混沌特性,其采用＂跳格序列＂作为扩频调制序列对用户信息进行调制。通过与传统混沌直接序列扩频（CDSS）系统的仿真比较发现,所设计的CPSK调制多用户扩频通信系统拥有比后者更好的误码性能及安全性能。     

时空混沌流扩频

针对计算机网络中的保密通信，充分利用时空混沌序列复杂度高、伪随机性好的特点，将时空混沌直接扩频通信与流密码技术相结合，提出时空混沌流扩频通信方案。以单向耦合映象格子时空混沌系统模型为基础，采用驱动-响应同步方法达到时空混沌同步，使用长周期的时空混沌二值序列作为会话密钥对明文信息进行扩频(加／解密)。这种通信方式具有很高的安全性。     

改进分段Skew Tent 映射及其在扩频通信中应用

混沌序列用作扩频系统扩频码,具有码元丰富、保密性好等优点。针对传统Skew Tent 映射所产生随机序列的混沌特性较弱,特别是其随机性、相关性等指标较差等不足,将Skew Tent 映射进行分段对偶扩展获得一种改进分段Skew Tent 映射构造方法,并将其所产生的随机序列用于构造扩频通信系统的扩频码。通过扩频通信系统仿真测试验证了改进分段Skew Tent 映射相比Skew Tent 映射具有更加良好的混沌特性,以及所产生随机序列作为扩频系统地址码在降低系统的误码率方面有了较大的改善。改进分段Skew Tent 映射作为加密算法用于图像通信系统中,有效提高了图像信息的传输质量和安全性。混沌映射进行分段对偶扩展是一种行之有效的改进方法,混沌特性更好的迭代映射更利于扩频通信在军民领域的广泛应用。     

多用户混沌序列扩频通信系统设计与性能分析

该文介绍了多用户混沌扩频通信系统原理,分析了Chebyshev,Logistic,Tent 3种混沌扩频序列的平衡性、相关性,建立了多用户混沌扩频通信系统动态可视化仿真模型,利用模型研究了这3种不同混沌扩频序列扩频码的初始值、信噪比、用户数以及截取的序列长度对系统误码率的影响。仿真结果表明,Chebyshev映射的扩频性能最好,Logistic映射次之,Tent映射最差,且这3种混沌扩频码的扩频性能均优于传统的扩频码。     

一种新的混沌扩频序列产生方法

本文提出了一种新的混沌扩频序列产生方法。该方法基于神经网络的强大学习能力和副近非线性函数能力,应用具有全局最优的ＢＰ改进算法通过训练学习建立起具有混沌性态的优化神经网络模型,利用网络权值调整的灵活性来产生混沌扩频序列。计算机仿真结果表明,该模型产生的混沌扩频序列调整更容易,比基于单一混沌映射能产生更多符合扩频通信要求的扩频序列。     

Performance of Chaos-Based Digital Communication Systems in the Presence of a Pulsed-Noise Jammer

Chaos-based communication systems are known to offer advantages that are shared by spread-spectrum communications. One important aspect of the performance of any spread-spectrum communication system is the ability to resist jamming. In this paper, an analysis of the antijamming performance of a coherent chaos shift keying system under the influence of a common pulsed-noise jammer is presented. Two types of pulsed-noise jammers, slowly switching and fast switching jammers, are considered in our studies. The performance is evaluated in terms of the bit error rate (BER) under different levels of noise power, jamming power, spreading factor, and duty factor. The maximum (worst-case) BERs are also obtained analytically for the case where the jammer is slowly switching. Computer simulations are performed to verify the analytical results. Finally, the BERs are compared with those of a conventional direct-sequence spread-spectrum communication system.     

Analysis and CMOS implementation of a chaos-based communication system

We describe the design and CMOS implementation of a baseband spread-spectrum communication system using chaotic signals for spreading digital data. The communication system uses a new chaotic modulation scheme called modified differential chaos shift keying (M-DCSK). The M-DCSK scheme and its characteristics are analyzed for single user and multi user applications. The chaotic signals were generated using a simple and robust circuit. The dynamics of this chaos generating circuit are also studied. The spectral properties of the system are investigated and compared with theoretical expectations.     

Essence and Advantages of FM-DCSK Versus Conventional Spread-Spectrum Communication Methods

Frequency-modulated differential chaos shift keying (FM-DCSK) is essentially a technique that combines modulation with a spread-spectrum property for communications. It is also an effective technique similar to recent multiantenna methodologies that can make use of multipath effects, thereby achieving an excellent anti-multipath fading capability. Through analysis and simulation, this paper reports some essential characteristics and advantages in the system performance of the newly proposed M-ary FM-DCSK technology. The basic design of the M-ary FM-DCSK-based chaotic spread-spectrum communication system and a comparison with its conventional equivalent are presented. It is shown that the former is not only robust in multipath fading environments and simple in implementation, but also flexible in adjusting system parameters and trading-off several effects among bandwidth efficiency, energy efficiency, data rate, and error performance. It is demonstrated that the FM-DCSK technique is promising for the next generation of wireless communication systems as an excellent modulation and spread-spectrum scheme candidate.     

基于混沌和CNN交错反馈产生扩频序列的性能分析

提出了一种基于细胞神经网络和混沌交错反馈产生扩频序列的设计方法,用计算机仿真对该混沌扩频序列的平衡特性、游程特性、位移特性、相关特性和线性复杂度等伪随机特性进行了系统的分析,并分析了该序列的奇/偶相关特性.结果表明,该混沌扩频序列具有理想的伪随机特性,可以作为扩频通信中的扩频码,同时系统的交错加强了通信的保密性.     

一种基于软件无线电技术的扩频通信系统

文章介绍了一种基于软件无线电技术的数字扩颊通信系统,包括扩频ASIC芯片的设计,发射机、接收机的设计等。着重描述了采用ESDA技术设计扩频ASIC信片的过程,给出了ASIC芯片的数学模型、仿真结果及系统性能分析。仿真及测试结果表明,该扩频通信系统具有较强的抗干扰能力。     

Exploiting the robust nature of spread-spectrum technology for future wireless applications

The attractiveness of spread-spectrum technology for future terrestrial mobile communication systems is shown. It is based on the robust nature of the spread-spectrum concept and its flexibility in the service design. The robustness of a spread-spectrum system is carried out and the corresponding benefits are listed and applied to future needs for communication systems.     

一种宽频段扩频通信系统设计

以某数据链课题为背景,设计了一种基于STEL－2000A可编程扩频处理器的宽频段扩频基带和数字中频处理器方案。主要集中论述扩频模块的实现,硬件部分着重基带电路的接口设计,软件部分着重STEL－2000A初始化和通信接口编程。测试结果表明,该方案工作频段宽,设备简单,具有一定的实用性和可移植性。     

Coexistence of chaos-based and conventional digital communication systems of equal bit rate

Chaos-based communication systems represent a new category of spread-spectrum communication systems, whose working principle differs significantly from conventional direct-sequence and frequency-hopping spread-spectrum systems. However, like all other kinds of spread-spectrum systems, chaos-based systems are required to provide reasonable bit error performance in the presence of a narrow-band signal which can be generated from an intruder or a coexisting conventional communication system. In particular, the frequency band of this foreign narrow-band signal can fall within the bandwidth of the chaos-based system in question. Such a scenario may occur in normal practice when chaos-based systems are introduced while the conventional systems are still in operation. It is therefore important to examine the coexistence of chaos-based and conventional systems. The objective of this paper is to evaluate the performance of the chaos-based system when its bandwidth overlaps with that of a coexisting conventional system. In particular, the chaos-based systems under study are the coherent chaos shift keying (CSK) system and the noncoherent differential CSK (DCSK) system, whereas the conventional system used in the study employs the standard binary phase shift keying scheme. Also, both the chaos-based and conventional systems are assumed to have identical data rates. Analytical expressions for the bit-error rates are derived, permitting evaluation of performance for different noise levels, power ratios and spreading factors. Finally, results from computer simulations verify the analytical findings.