A secure communication scheme based on chaotic Duffing oscillators and frequency estimation for the transmission of binary-coded messages

This work presents a new technique to securely transmit and retrieve a message signal via chaotic systems. The main contribution of this paper is two-fold: the way that the message signal is encrypted in the frequency of a sinusoidal term and a novel frequency estimator for retrieving the message. In our system, a two-valued message signal modulates the frequency of the Duffing oscillator sinusoidal term. Then, two chaotic signals generated by the oscillator are encrypted with a Delta modulator and sent through a noisy channel. A Lyapunov-based observer is used in the receiver side to retrieve the sinusoidal term that contains the message and a novel frequency estimator is then used to retrieve the confidential message signal. The system was implemented in Matlab/Simulink in order to analyze its performance.     

基于WIA-PA传感器网络的能量有效时间同步算法

WIA-PA协议是一种新型工业级无线传感器网络国际标准。当WIA-PA网络内节点数目增多时,传统的参考广播同步算法RBS以及改进型ERBS算法网络开销非常大。针对这一严峻的问题,提出了一种能量有效的局部最优时间同步算法。该算法对相邻的接收节点在多个参考广播消息的条件下求取平均相位偏差,然后对此平均相位偏差进行最大后验估计,最后根据此估计值调整本地时钟。仿真结果表明,本文所提时间同步算法在同步精度方面比RBS约提高168%,比ERBS约提高24%;同时,同步过程中的网络能耗也大大减少。     

基于EPL的分布式时钟同步方法

工业以太网协议Ethernet POWERLINK(EPL)分布式站点的时钟同步方法并不能在实时运行过程中保持很高的同步精度,无法满足特定环境下的控制要求。研究了工业以太网协议EPL的两种时钟同步机制,通过数理计算分析了时钟同步误差产生的原因,针对误差较大的缺点,提出了减小误差的方法。通过迭代计算消除了主从站同步报文往返的路径延迟,并设计基于现场可编程门阵列(FPGA)的集线器(Hub)用于EPL菊花链网络拓扑结构,有效地克服了时钟同步报文往返传输延时不一致的缺点,测试结果表明新方法明显优于协议自身的时钟同步方法,对于实现基于EPL的高精度分布式时钟同步网络具有重要意义。     

A new color image cryptosystem via hyperchaos synchronization

This paper proposes a novel color image cryptosystem based on synchronization of two different six-dimensional hyperchaotic systems. In the transmitter end, we apply the drive system to generate the diffusion matrices and scrambling ones, which are used to change the image pixel value and position, respectively. Thus the ciphered image is obtained. In the receiver, synchronization of two nonidentical hyperchaotic systems can be achieved by designing the appropriate controllers. The response system is employed to yield the corresponding diffusion matrices and scrambling ones using the same generation method in the encryption algorithm. Then the cipher-image can be decrypted by the decryption algorithm, which is similar to that of the encryption process but in the reversed order. The experimental results show that the presented image cryptosystem has high security and can resist noise and crop attacks.     

An improved artificial bee colony algorithm for directing orbits of chaotic systems

Artificial bee colony algorithm (ABC) is a relatively new optimization technique which has been shown to be competitive to other population-based algorithms. However, there is still an insufficiency in ABC regarding its solution search equation, which is good at exploration but poor at exploitation. To address this concerning issue, we propose an improved ABC (IABC) by using a modified search strategy to generate a new food source in order that the exploration and exploitation can be well balanced and satisfactory optimization performances can be achieved. In addition, to enhance the global convergence, when producing the initial population, both opposition-based learning method and chaotic maps are employed. In this paper, the proposed algorithm is applied to control and synchronization of discrete chaotic systems which can be formulated as both multimodal numerical optimization problems with high dimension. Numerical simulation and comparisons with some typical existing algorithms demonstrate the effectiveness and robustness of the proposed approach.     

Type-I intermittency with noise versus eyelet intermittency

In this Letter we compare the characteristics of two types of the intermittent behavior (type-I intermittency in the presence of noise and eyelet intermittency taking place in the vicinity of the chaotic phase synchronization boundary) supposed hitherto to be different phenomena. We show that these effects are the same type of dynamics observed under different conditions. The correctness of our conclusion is confirmed by the consideration of different sample systems, such as quadratic map, Van der Pol oscillator and Rössler system. Consideration of the problem concerning the upper boundary of the intermittent behavior also confirms the validity of the statement on the equivalence of type-I intermittency in the presence of noise and eyelet intermittency observed in the onset of phase synchronization.     

Nonlinear electronic circuit, Part II: synchronization in a chaotic MODEM scheme

In this work we present a thorough investigation of the effect of noise (internal or external) on the synchronization of a drive-response configuration system (unidirectional coupling between two identical systems). Moreover, since in every practical implementation of a communication system, the transmitter and receiver circuits (although identical) operate under slightly different conditions it is essential to consider the case of the mismatch between the parameters of the transmitter and the receiver. In our work we consider the non-autonomous 2nd order nonlinear oscillator system presented in [G. Mycolaitis, A. Tamasevicious, A. Cenys, A. Namajunas, K. Navionis, A. N. Anagnostopoulos, Globally synchronizable non-autonomous chaotic oscillator, in: Proc. of 7th International Workshop on Nonlinear Dynamics of Electronic Systems, Denmark, July 1999, pp. 277-280] which is particularly suitable for digital communications.Furthermore, we modified the previous chaotic communication system in order to exhibit enhanced security features. The enhancement in the security of the system is achieved by introducing a set of parameters used in the encoding and decoding of the message signal. We also introduce a time delay parameter in the dynamical system which on the one hand improves the chaotic behavior of the system and on the other hand, adds further security in the encoding-decoding scheme.     

Chaotic synchronization by the intermittent feedback method

This paper studies the synchronization of chaotic systems by the intermittent feedback method which is efficient. A sufficient synchronization criterion for a general intermittent linear state error feedback control is obtained by using a Lyapunov function and differential inequalities. Numerical simulations for the chaotic Chua oscillator are presented to illustrate the theoretical results.