Frequency-Frequency Interactions in Chaos Communications

Chaos: An Interdisciplinary Journal of Nonlinear Science, 2005

A new spread spectrum communication system utilizing chaotic frequency modulation of sinusoidal signals is discussed. A single phase lock loop ͑PLL͒ system in the receiver is used both to synchronize the local chaotic oscillator and to recover the information signal. We study the dynamics of the synchronization process, stability of the PLL system, and evaluate the bit-error-rate performance of this chaos-based communication system.

Signal Processing, 2015

Many communication systems based on the synchronism of chaotic systems have been proposed as an alternative spread spectrum modulation that improves the level of privacy in data transmission. However, depending on the map and on the encoding function, the transmitted signal may cease to be chaotic. Therefore, the sensitive dependence on initial conditions, which is one of the most interesting properties for employing chaos in telecommunications, may disappear. In this paper, we numerically analyze the chaotic nature of signals modulated using a system that employs the Ikeda map. Additionally, we propose changes in the communication system in order to guarantee that the modulated signals are in fact chaotic.

Physics Letters A, 1996

The results of the experimental observation of synchronized chaos in circuits generating chaotic oscillations with different characteristic frequencies are presented. This synchronized chaotic behavior is studied in a system composed of an autonomous chaotic driving circuit and a response circuit. Onset of synchronization is detected by the auxiliary system method.

Acta Astronautica, 2003

Methods of communications using chaotic signals use an ability of a chaos generator (encoder) and matched response system (decoder) to behave identically despite the instability of chaotic oscillations. Chaotic oscillations cover a wide spectral domain and can efficiently mask an information signal scrambled by the chaotic encoder. At the same time the wide spectrum poses intrinsic difficulties in the chaotic decoding if the chaotic signal is transmitted over real communication channels with limited bandwidth. We address this problem both numerically and experimentally. Two alternative ways to improve communication with chaos over band-limited channels are investigated. The first method employs a matching filter in the decoder which compensates channel distortions of the transmitted signal. This modification does not change the individual dynamics of chaotic systems in the synchronous state however the information signal injected into the driving system, breaks the symmetry between encoder and decoder and therefore exact recovery is impossible. We show that this approach has limited ability for synchronization of chaotic encoder. The second approach does not use adaptive compensation but relies on the design of chaotic oscillators which produce narrow-band chaotic waveforms.

Understanding Complex Systems, 2011

showing better security performance than that of the conventional method.

In recent years, synchronization of chaotic systems and its potential application to secure digital communications have received ever increasing attention.

Physics Letters A, 2004

We discuss an approach of chaotic signal communication that is based on the synchronization of two identical nonlinear systems. Along with the procedure of decoding a pair of unknown chaotic signals, a parameter of the transmitting system is estimated through adaptive evolution. The signals are actually two dynamical variables of a nonlinear system. As one of the parameters of the transmitting chaotic system is unknown, security is assured against external interceptions. A periodic signal is also transmitted and it is recovered directly without any parameter estimation.

International Journal of Bifurcation and Chaos, 2005

In this article, the secure transmission of data is being realized on the basis of the synchronization of two chaotic systems. The transmitted signal is only the sign of a projection of the state. This has the advantage of making the transmission not very sensitive to the noises of transmission and the attenuation of the transmitted signal without using a VCO (Voltage Control Oscillatory) into the transmitter and the receiver. It should be noted that for the considered type of chaotic system, the traditional conditions of observability and linearization by injection of outputs are not checked. Here, we can only carry out an estimator.

Journal of Engineering Science and Technology Review, 2009

The experimental study of a secure chaotic synchronized communication system is presented. The synchronization between two digital chaotic oscillators, serving as a transmitter-receiver scheme, is studied. The oscillators exhibit rich chaotic behavior and are unidirectionally coupled, forming a master-slave topology. Both the input information signal and the transmitted chaotic signal are digital ones.