Chaotic Modulation Research Articles

Multiuser BER Analysis Of CS-QCSK Modulation Scheme in a Cellular System

In recent years, chaotic communication is a hot research topic and it suits better for the emerging wireless networks because of its excellent features. Different chaos based modulation schemes have evolved, of which the CS-DCSK modulation technique provides better BER performance and bandwidth efficiency, due to its code domain approach. The QCSK modulation technique provides double benefit: higher data rate with similar BER performance and same bandwidth occupation as DCSK. By combining the advantage of code shifted differential chaos shift keying (CS-DCSK) and Quadrature chaos shift keying (QCSK) scheme, a novel modulation scheme called code shifted Quadrature chaos shift keying (CS-QCSK) is proposed and its suitability in a multiuser scenario is tested in this paper. The analytical expressions for the bit-error rate for Multi-user CS-QCSK scheme (MU-CS-QCSK) under Rayleigh multipath fading channel is derived. The simulation result shows that, in multiuser scenario the proposed method outperforms classical chaotic modulation schemes in terms of bit error rate (BER).

Suppressing harmonics in four‐quadrant AC‐DC converters with chaotic SPWM control

ABSTRACTIn this paper, a new chaotic sinusoidal pulse width modulation (chaotic SPWM) control is proposed and implemented in a four‐quadrant AC‐DC converter for harmonics suppression, where a chaotic carrier plays a key role. Further, the relationship of the harmonic distribution and carrier frequency is derived by analyzing the harmonic components of the AC‐DC converter, which is useful for revealing the operation principle of the chaotic SPWM control for harmonic suppression. Finally, the simulation and experimental results illustrate the effectiveness of the proposed chaotic SPWM control on harmonics reduction. Copyright © 2012 John Wiley & Sons, Ltd.

Dispersion compensation in an open-loop all-optical chaotic communication system

The optical chaotic communication system using open-loop fiber transmission is studied under strong injection conditions. The optical chaotic communication system with open-loop configuration is studied using fiber transmission under strong injection conditions. The performances of fiber links composed of two types of fiber segments in different dispersion compensation maps are compared by testing the quality of the recovered message with different bit rates and encrypted by chaotic modulation (CM) or chaotic shift keying (CSK). The result indicates that the performance of the pre-compensation map is always worst. Two types of symmetrical maps are identical whatever the encryption method and bit-rate of message are. For the transmitting and the recovering of message of lower bit rate (1 Gb/s), the post-compensation map is the best scheme. However, for the message of higher bit rate (2.5 Gb/s), the parameters in communication system need to be modified properly in order to adapt to the high-speed application. Meanwhile, two types of symmetrical maps are the best scheme. In addition, the CM method is superior to the CSK method for high-speed applications. It is in accordance with the result in a back-to-back configuration system.

Examination of the nonlinear dynamics of a chaotic acousto-optic Bragg modulator with feedback under signal encryption and decryption

An acousto-optic Bragg cell with first-order feedback, which exhibits chaotic behavior past the threshold for bistability, was recently examined for possible chaotic encryption and recovery of simple messages (such as low-amplitude periodic signals) applied via the bias input of the sound cell driver. We carry out a thorough examination of the nonlinear dynamics of the Bragg cell under intensity feedback for (i) dc variations of the feedback gain () and the phase shift parameter (0) and (ii) ac variations of 0,total under signal encryption, investigating both from two different perspectives: (i) examining chaos in view of the so-called Lyapunov exponent derived recently by Ghosh and Verma and (ii) examining chaos in terms of the familiar bifurcation maps of intensity plotted against the feedback gain and the effective bias. It is shown that overall, the nonlinear dynamical results using the two approaches broadly agree, both for dc (fixed-parameter) analyses and, more importantly, when applied to the case of ac signal encryption cases. This affirms the effectiveness of the nonlinear dynamical theory in predicting and tracking the actual physical behavior of this system for message signal transmission and recovery under complex chaotic encryption.

DDCSK-Walsh Coding: A Reliable Chaotic Modulation-Based Transmission Technique

To overcome the performance loss of noncoherent detectors of differential chaos-shift keying (DCSK), some improved versions of DCSK have been proposed. However, little has been done to improve the multiuser DCSK system based on Walsh codes (WCs), i.e., referred to as DCSK-WC, although it is considered more feasible in practice among the existing multiuser DCSK systems. This brief introduces a novel differentially DCSK (DDCSK) technique into such a multiuser system so as to build the desirable DDCSK-WC, obtaining significant performance gain, as compared with the conventional DCSK-WC, while retaining its hardware complexity unchanged. Moreover, the proposed system can greatly enhance the robustness against intersymbol interference in a wireless multipath fading channel. Therefore, the new system is deemed to provide a good alternative transmission scheme for wireless communication based on chaotic modulation, in such as indoor applications of the transmitted-reference ultrawideband. The theoretical analysis and simulated noise performances of the proposed system demonstrate their high consistence.

A Image Transmission System Based on Logistic Map

A method for chaotic synchronization system based on nonlinear control was studied. The general approach to chaotic system is following Logistic map. First, the parameter which meets chaotic status was analyzed and found via bifurcation diagram and Lyapunov exponent spectrum. The system can be synchronized quickly after just only a single iteration. Then, the method of implementing the synchronization system within a chaotic parameter modulation based communication system was researched. The deduction and simulation results also showed the probability for implementation the system in fast secure chaotic communications that require instant synchronization schemes. Finally, the chaotic system was applied in image transmission and the simulation results were also given.

Optimization of Matched Chaotic Frequency Modulation Excitation Sequences for Multichannel Simultaneously Triggered Ultrasonic Ranging System

The matched spectrum and correlation characteristics are both important to realize the multichannel ultrasonic sensors working together. The spectrum matching can make full use of the bandwidth of the ultrasonic ranging system, and the good correlation characteristic can eliminate crosstalk among multichannel ultrasonic sensors triggering simultaneously. Linear frequency modulation (LFM) excitation sequences have been used as transmission signals for ultrasonic sensors. Due to the narrow bandwidth of the ultrasonic ranging system, the number of available LFM excitation sequences is limited. The chaotic frequency modulation (CFM) excitation sequences, which can generate more available excitation signals, are proposed in this paper. The nondominated sorting genetic algorithm-II is adopted to optimize both the spectrum and correlation characteristic of the CFM excitation sequences. After optimization, the CFM excitation sequences are spectrally matched to the ultrasonic ranging system as well as have best correlation characteristic. Real experiments have been implemented using an ultrasonic ranging system consisting of eight-channel SensComp 600 series electrostatic sensors excited with 2 ms CFM sequences. Experimental results show that spectra of the optimized CFM excitation sequences can match to the system and can work together without crosstalk.

A Chaos MIMO Transmission Scheme for Channel Coding and Physical-Layer Security

SUMMARY In recent wireless communication systems, security is ensured mainly in the upper-layer techniques such as a password or a cryptography processing. However, security needs not be restricted to the upperlayer and the addition of physical-layer security also would yield a much more robust system. Therefore, in this paper, we exploit chaos communication and propose a chaos multiple-input multiple-output (MIMO) transmission scheme which achieves physical-layer security and additional channelcoding gain. A chaotic modulation symbol is multiplied to the data to be transmitted at each MIMO antenna to exploit the MIMO antenna diversity, and at the receiver, the joint MIMO detection and chaos decoding is done by maximum likelihood decoding (MLD). The conventional chaos modulation suffers from bit error rate (BER) performance degradation, while the coding gain is obtained in the proposed scheme by the chaos modulation in MIMO. We evaluate the performances of the proposed scheme by an

Improvement of Bit Rate Using M-ary Chaotic Pulse Position Modulation

Recent studies have pointed out that Chaotic Pulse Position Modulation (CPPM) is a very promising method for improving privacy and security in chaos-based digital communication. Especially, CPPM provides better performance than other chaotic modulation methods in noise- and distortion-affected environments. In this paper we present our development of a robust method named M-ary CPPM which is based on the combination of the conventional CPPM and multi-symbol modulation in order to improve the transmission bit rate. The M-ary CPPM signal has a pulse train format in which each pulse is a symbol and the chaotically-varied inter-pulse time interval conveys the binary information of k bits (M = 2k). The analysis and development of modulation and demodulation schemes are presented in detail. Theoretical evaluation of Bit-Error-Rate (BER) performance in the presence of additive white Gaussian noise (AWGN) and the use of AWGN filtering is also provided. The chaotic behavior of the M-ary CPPM is investigated with the variation of modulation parameters. In order to verify the performance of the proposed schemes, numerical simulations were carried out in Simulink and comparison between simulation and theoretical results is reported.

Image Encryption Algorithm Based on Chaotic Modulation of Arnold Dual Scrambling and DNA Computing

Image Encryption Algorithm Based on Chaotic Modulation of Arnold Dual Scrambling and DNA Computing

Improvement of Electromagnetic Compatibility of Motor Drives Using Hybrid Chaotic Pulse Width Modulation

This paper proposes and implements a new hybrid chaotic (HC) pulse width modulation (PWM) scheme for the reduction of electromagnetic interference (EMI) in alternating current (AC) motor drives. This scheme utilizes logistic mapping to simultaneously chaoize both the carrier frequency and the pulse position. Compared with available chaotic PWM schemes such as the chaotic-pulse-position-modulated (CPPM) PWM and the chaotic-amplitude-frequency-modulated (CAFM) PWM, the proposed scheme is a synergy of CPPM-PWM and CAFM-PWM. Thus, it possesses a hybrid characteristic, namely the peaky EMI is suppressed while the occurrence of low-order noises is reduced. Both simulation and experimental results are provided to support the validity.

A chaotic system in synchronization and secure communications

In this paper we deal with the synchronization and parameter estimations of an uncertain Rikitake system and its application in secure communications employing chaotic parameter modulation. The strategy consists of proposing a receiver system which tends to follow asymptotically the unknown Rikitake system, refereed as transmitter system. The gains of the receiver system are adjusted continually according to a convenient high order sliding-mode adaptative controller (HOSMAC), until the measurable output errors converge to zero. By using HOSMAC, synchronization between transmitter and receiver is achieved and message signals are recovered. The convergence analysis is carried out by using Barbalat’s Lemma.

Adaptive-based methods for information transmission by means of chaotic signal source modulation

Three methods for information transmission based on chaotic signal source modulation based on: application of adaptive observers, adaptive identification with the Implicit Adjustable Model, and frequency modulation with the adaptive demodulator are described. Application of the proposed methods for information transmission by means of chaotic Chua generator modulation is presented.

A Novel Digital Image Covert Communication Scheme Based on Generalized FCM in DCT Domain

A novel covert communication method of digital image is presented, based on generalized fuzzy c-means clustering (GFCM), human visual system (HVS) and discrete cosine transform (DCT). Therefore, the original image blocks are classified into two classes according to specified characteristic parameters. So one block is suited for embedding security information, but the other block is not. Hence the appropriate blocks can be selected in an image to embed the security information by selectively modifying the middle-frequency part of the original image in conjunction with HVS and DCT. Furthermore the maximal information strength is fixed based to the frequency masking. Also to improve performances of the proposed algorithm, the security information is modulated into the chaotic modulation array. The simulation results show that we can remarkably extract the hiding security information and can achieve good robustness with common signal distortion or geometric distortion and the quality of the embedded image is guaranteed.

A new digital communication scheme based on chaotic modulation

Based on parameter identification, a parameter observer is designed for a class of chaotic systems. The digital signals modulated in the parameter will be recovered by the observer. By choosing different frequency signals as “0” and “1,” a practical digital secure communication scheme is proposed by this parameter modulation method. Numerical simulations show the effectiveness of this communication scheme.

Performance of a new decoding method used in open-loop all-optical chaotic communication system

A new decoding method with decoder is used in open-loop all-optical chaotic communication system under strong injection condition. The performance of the new decoding method is numerically investigated by comparing it with the common decoding method without decoder. For new decoding method, two cases are analyzed, including whether or not the output of the decoder is adjusted by its input to receiver. The results indicate the decoding quality can be improved by adjusting for the new decoding method. Meanwhile, the injection strength of decoder can be restricted in a certain range. The adjusted new decoding method with decoder can achieve better decoding quality than decoding method without decoder when the bit rate of message is under 5 Gb/s. However, a stronger injection for receiver is needed. Moreover, the new decoding method can broaden the range of injection strength acceptable for good decoding quality. Different message encryption techniques are tested, and the result is similar to that of the common decoding method, indicative of the fact that the message encoded by using Chaotic Modulation (CM) can be best recovered by the new decoding method owning to the essence of this encryption technique.

Video-Object Oriented Biometrics Hiding for User Authentication under Error-Prone Transmissions

An automatic video-object oriented steganographic system is proposed for biometrics authentication over error-prone networks. Initially, the host video object is automatically extracted through analysis of videoconference sequences. Next, the biometric pattern corresponding to the segmented video object is encrypted by a chaotic cipher module. Afterwards, the encrypted biometric signal is inserted to the most significant wavelet coefficients of the video object, using its qualified significant wavelet trees (QSWTs). QSWTs provide both invisibility and significant resistance against lossy transmission and compression, conditions that are typical in error prone networks. Finally, the inverse discrete wavelet transform (IDWT) is applied to provide the stego-object. Experimental results under various losses and JPEG compression ratios indicate the security, robustness, and efficiency of the proposed biometrics hiding system.

A Combined just Noticeable Distortion Model-Guided Color Image Watermarking Scheme

A new color image watermarking scheme is presented. The visual characteristics of HVS, multi-resolution of discrete wavelet transform, and color image content information are adopted to classify the wavelet coefficients and find a new JND model. The embedded watermark is processed by Arnold transform and chaotic modulation, which can improve the security of scheme. The combined JND model-guided watermarking scheme provides the maximum strength transparent watermark to compromise the robustness and invisibility. Both better invisibility and robustness work than other algorithms based on HVS are shown in the experimental results.

Design of Analogue Chaotic PWM for EMI Suppression

An analogue chaotic carrier is designed to be embedded in a chaotic pulse width modulation (PWM) boost converter, and to be used for reducing electromagnetic interference (EMI) in dc-dc converters. The analogue chaotic PWM has its advantages over the digital one in its low costs and easy-to-design, making it suitable for high-frequency operation and situations when design flexibility and low cost are required. Finally, simulations and experiments are conducted to illustrate the effectiveness of the proposed analogue chaotic PWM in reducing EMI.

A 3-GHz Serial ATA Spread-Spectrum Clock Generator Employing a Chaotic PAM Modulation

In this paper, we propose a prototype of a spread-spectrum clock generator which is the first known specifically meant generator for 3-GHz Serial Advanced Technology Attachment II (SATA-II) applications. A further innovative aspect of our prototype is that it takes advantage of a chaotic pulse-amplitude modulation as driving signal, instead of a triangular signal as in all spread-spectrum generators proposed so far in the literature for SATA-II. In this way, we are able to obtain the optimal theoretical electromagnetic-interference reduction by avoiding the periodicity of the modulated clock and completely flattening the peaks in the power spectral density. We also show that, despite the fact that such an unconventional aperiodic modulating signal is used, the clock can be recovered by exploiting a standard clock and data recovery circuit at the receiver side of the SATA-II bus. The circuit prototype has been implemented in 0.13-μm CMOS technology and achieves a peak reduction greater than 14 dB measured at RBW = 100 kHz, which is better than any other prototypes presented in the literature. The estimated random jitter is 5.4 ps <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> , while the chip active area is 0.27 0.78 × mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the power consumption is as low as 14.7 mW.