Using the cyclostationary properties of chaotic signals for communications

Abstract

Cyclostationary signals have an expectation value which varies periodically in time. Chaotic signals that have large components at some discrete frequencies in their power spectra can be cyclostationary. The cyclostationarity persists even if the discrete frequency components are removed from the chaotic signal, leaving a signal with a purely broad band frequency spectrum. In this brief, a communications system is created by modulating information onto the periodic parts of a chaotic signal and then removing the periodic parts from the frequency spectrum. At the receiver, the periodic parts of the spectrum are restored by means of a nonlinear operation. This system is demonstrated both in simulations and real circuits, and the performance of this system is measured in simulations. Finally, some of the reasons why such a scheme might be useful are discussed.

Generalized Multi-carrier Chaotic Shift Keying

“…As shown in the Figure 2, when ‫ܭ‬ ൌ ͳ, the SER associated with each of the waveforms are approximately equivalent in low E s /N 0 regions; as the E s /N 0 is increased in the exploded view of Figure 3, the error rates for each of the waveforms diverge due to the increased self-interference of the received signal in the non-matched correlator. As expected, the constant amplitude CAZAC/DSSS waveforms provide the (6) lowest SER among the compared waveforms, yielding an approximate 0.4 dB performance gain over Gaussian chaotic. 2 While SER curves for specific spreading characteristics (chaos, percent Gaussian, or CAZAC) appear parallel with increasing E s /N 0 , it is seen that the CAZAC error performance overtakes that of a lower-ordered (smaller ‫)ܯ‬ chaos waveform in the limiting case of E s /N 0 ՜ λ.…”

“…Data is then recovered by match filtering all possible carrier selections at the receiver, choosing the one with the highest likelihood of being the transmitted symbol [1]. The security of these CSK systems is limited in that the chaotic attractor is itself a characteristic feature that can be used to convey information [6] and may need to be suppressed [7] in order to retain the desired security of from external detection. This paper presents a generalized CSK modulation derived from a digital chaotic communication system, where the transmitted signal is based on a data-selective mapping of an underlying time-synchronized digital chaotic circuit's output into a plurality of orthogonal spread spectrum carriers.…”

Design and analysis of a spread‐spectrum communication system with chaos‐based variation of both phase‐coded carrier and spreading factor

“…However with an unintended receiver, it is very difficult to detect the phase-coded carrier from the incoming signal because the chaotic sequence is converted into the NRZ form and covered by the BPSK carrier. With respect to the conventional SS systems with the fixed bit duration, since the cyclostationary properties [48] in the transmitted signal, the detection of this parameter is simply carried out by means of the spectrum analysis [49]. To overcome this drawback, in this paper, the spreading factor is designed to vary in the communication process and this variation leads to the variation of bit duration and bit energy.…”

Removing Cyclostationary Properties in a Chaos-Based Communication System

“…Note that the lower the control parameter, the higher the security of the transmission system will be. For the input bits (b ∈ 0, 1) b = [b [1], b [2], . .…”

“…It has been shown in [8] that the cyclostationary properties of some chaotic signals used in digital communication systems can be detected. The use of cyclostationary properties of chaotic signals for communication is observed in [2]. With this type of signal used in secure transmissions, the cyclostationary properties must be removed.…”