A multiple access scheme for chaos-based digital communication systems utilizing transmitted reference

Author name used in this publication: Francis C. M. LauAuthor name used in this publication: Chi K. Tse2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A chaotic secure communication scheme based on duffing oscillators and frequency estimation

This work presents a new technique to securely transmit and retrieve a message signal via chaotic systems. In our system, a two-valued message signal modulates the frequency of a Duffing oscillator sinusoidal term. An observer is used in the receiver side to retrieve the sinusoidal signal that contains the message and a novel frequency estimator is then used to reproduce an approximated estimation of the message signal. The performance of the system is analyzed by means of numerical simulations performed in Matlab.Postprint (author’s final draft

A secure communication system based on a modified chaotic chua oscillator

In this paper we propose a new scheme for secure communications us- ing a modified Chua oscillator. A modification of the oscillator is proposed in order to facilitate the decryption. The communication system requires two channels for transmitting the message. One of the channels transmits a chaotic signal generated by the oscillator and is used for synchronization. The second channel transmits the message encrypted by a nonlinear function. This function is built in terms of one of the chaotic signals, different from that sent on the first channel. In the receiver side, a synchronizer reconstructs the chaotic oscillator signals, one of which is used for the decryption of the message. The synchronization system is designed via Lyapunov theory and chaoticity proves via Poincar ´e maps and Lyapunov exponents will be pro- vided in order to demonstrate the feasibility of our system. Numerical simulations will be used to evaluate the performance of the system.Postprint (published version

Physics and Applications of Laser Diode Chaos

An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.Comment: Published in Nature Photonic

Analysis of a new modulation/ multiplexing technique using mutually orthogonal chaotic waveforms

A new digital modulation technique proposed [3] by Dr. Chance M. Glenn is presented and analyzed in this report. The report explains the MOC algorithm as a means of creating information-bearing baseband signals for modulation in digital communications. The process uses the natural diversity of chaotic oscillations. An orthogonal triplet of waveforms is extracted from the oscillations produced by a chaotic process. A simple digital communication system is built, which uses this triplet as basis waveforms to formulate a baseband waveform. There is a lot of research work done and still going on to use chaotic oscillations in the communication system. The previously proposed communication systems have a disadvantage of not retrieving the data back at the demodulator as the demodulator need to be synchronized with the modulator, which cannot be implemented in real time. We propose a new way of using chaotic oscillations. The work done and contribution toward the thesis includes finding sets of mutually orthogonal chaotic waveforms using the data collected from the various chaotic oscillations, finding an optimal set of chaotic waveforms that can be used in the communication system. We demonstrated the implementation of the communication system using Matlab and Simulink. We simulated and analyzed the communication system built based on the MOC waveforms. We compared the results yielded with other modulation schemes like QAM, QPSK. The goal is to show that the system outperforms other comparable modulation/multiplexing techniques. We\u27ll use concepts such as the spectral efficiency and bit error rate to show and compare the results

Unmasking Optical Chaotic Cryptosystems Based on Delayed Optoelectronic Feedback

29 páginas, 22 figuras, 3 tablas.The authors analyze the security of optical chaotic communication systems. The chaotic carrier is generated by a laser diode subject to delayed optoelectronic feedback. Transmitters with one and two fixed delay times are considered. A new type of neural networks, modular neural networks, is used to reconstruct the nonlinear dynamics of the transmitter from experimental time series in the single-delay case, and from numerical simulations in single and two-delay cases. The authors show that the complexity of the model does not increase when the delay time is increased, in spite of the very high dimension of the chaotic attractor. However, it is found that nonlinear dynamics reconstruction is more difficult when the feedback strength is increased. The extracted model is used as an unauthorized receiver to recover the message. Therefore, the authors conclude that optical chaotic cryptosystems based on optoelectronic feedback systems with several fixed time delays are vulnerable.This work was supported by CICYT (Spain) under Project TEC2009-14581-C02-02.Peer reviewe

Nonlinear Unknown‐Input Observer‐Based Systems for Secure Communication

Secure communication employing chaotic systems is considered in this chapter. Chaos‐based communication uses chaotic systems as its backbone for information transmission and extraction, and is a field of active research and development and rapid advances in the literature. The theory and methods of synchronizing chaotic systems employing unknown input observers (UIOs) are investigated. New and novel results are presented. The techniques developed can be applied to a wide class of chaotic systems. Applications to the estimation of a variety of information signals, such as speech signal, electrocardiogram, stock price data hidden in chaotic system dynamics, are presented

A Tutorial on Time-Evolving Dynamical Bayesian Inference

In view of the current availability and variety of measured data, there is an increasing demand for powerful signal processing tools that can cope successfully with the associated problems that often arise when data are being analysed. In practice many of the data-generating systems are not only time-variable, but also influenced by neighbouring systems and subject to random fluctuations (noise) from their environments. To encompass problems of this kind, we present a tutorial about the dynamical Bayesian inference of time-evolving coupled systems in the presence of noise. It includes the necessary theoretical description and the algorithms for its implementation. For general programming purposes, a pseudocode description is also given. Examples based on coupled phase and limit-cycle oscillators illustrate the salient features of phase dynamics inference. State domain inference is illustrated with an example of coupled chaotic oscillators. The applicability of the latter example to secure communications based on the modulation of coupling functions is outlined. MatLab codes for implementation of the method, as well as for the explicit examples, accompany the tutorial.Comment: Matlab codes can be found on http://py-biomedical.lancaster.ac.uk