Differential Chaos Shift Keying System Research Articles

System Design and Performance Analysis of Orthogonal Multi-Level Differential Chaos Shift Keying Modulation Scheme

A novel non-coherent multi-level differential chaos shift keying (DCSK) modulation scheme is proposed in this paper. This new scheme is based on both the transmitted-reference technique and $M$ -ary orthogonal modulation, where each data-bearing signal is chosen from a set of orthogonal chaotic wavelets constructed by a reference signal. Thanks to this signaling design, the new scheme can achieve a higher attainable data rate, lower energy loss in reference transmission, increased bandwidth efficiency, better data security and better bit error rate (BER) performance as compared to the conventional DCSK. Unlike other DCSK-based systems that separate the reference and data-bearing signals using the TDMA scheme, this new system employs I/Q channels to send these two signals in a parallel and simultaneous manner, making the system easily extendable to multi-carriers. This transmission mechanism not only can further increase data rate but also can remove all radio frequency delay lines from detectors. Analytical BER expressions of the proposed system are derived for both additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Relevant simulation results are given and compared to non-coherent binary/ $M$ -ary DCSK systems. In addition, the impacts of various system parameters on noise performance are discussed. Both theoretical analysis and simulation results confirm the promising benefits of the new design.

Iterative Receiver for <inline-formula> <tex-math notation="LaTeX">$M$</tex-math></inline-formula>-ary DCSK Systems

Although the performance of a differential chaos shift keying (DCSK) system can be improved by designing appropriate channel codes, it is still a great challenge to do so for various channel models through transmitter and receiver designs, particularly with short frame length transmissions. Alternatively, to bypass the difficult task of designing a good channel code, an iterative receiver (IR) DCSK system is proposed in this paper. A soft demapper suitable for non-coherent $M$ -ary DCSK system is presented, which can work either with or without fading amplitude information. Bit error rate (BER) performance shows its advantages over the non-IR DCSK system in different channel models. The achievable rate curves also indicate that gains relative to non-iterative DCSK system can be achieved with the iterative receiver.

Design and Performance Analysis of a New Multiresolution <inline-formula> <tex-math notation="LaTeX">$M$</tex-math></inline-formula>-Ary Differential Chaos Shift Keying Communication System

A new multiresolution $M$ -ary differential chaos shift keying (DCSK) modulation scheme is proposed in this paper. It is a promising technique for providing a different quality of service for transmitted bits within a symbol according to their different bit error rate (BER) requirements based on the principle of nonuniformly spaced constellations. The new system not only is simple but also provides better antimultipath fading performance against various spreading factors, inheriting the advantages of the conventional DCSK system. Furthermore, the proposed scheme and its multicarrier version further increase spectral efficiency and use lower energy consumption at the same bandwidth as compared with the conventional DCSK and its multicarrier system. Explicit BER expressions of the new system are derived and analyzed over additive white Gaussian noise and multipath Rayleigh fading channels. All simulation results verify the prominent advantages of the new scheme and the accuracy of the new analytical approach.

BER performance enhancement for secure wireless communication systems based on DCSK-MIMO techniques under Rayleigh fading channel

There has been a growing interest in the use of chaotic techniques for enabling secure communication in recent years. This need has been motivated by the emergence of a number of wireless services which require the channel to provide very low bit error rates (BER) along with information security. As more and more information is transacted over wireless media, there has been increasing criminal activity directed against such systems. This paper investigates the feasibility of using chaotic communications over Multiple-Input-Multiple-Output (MIMO) channels. We have studied the performance of differential chaos shift keying (DCSK) with 2×2 Alamouti scheme and 2×1 Alamouti scheme for different chaotic maps over additive white Gaussian noise (AWGN) and channels disturbed by Rayleigh fading. Both the inherently wideband DCSK modulation and the space-time block code (STBC) are techniques that can mitigate the effect of multipath fading. The use of these schemes allows us to enhance security without degrading the BER performance for Rayleigh fading channels. We have employed an exact method to analyze the performances of DCSK communication system over fading channel. Our simulations indicate that the combination of the STC and tent map provides the best BER performance in addition to security when compared to the choice of other maps. Hence, this study shows that the use of these schemes can allow the user to enhance security without degrading the BER performance while communicating over these channels.

DCSK와 CDSK 방식을 사용하는 카오스 통신 시스템의 항재밍 특성

디지털 통신 기술은 보다 높은 데이터 효율과 정보의 효율적인 부호화에 초점을 맞추고 있다. 또한, 보안성을 높이고 외부 요인의 간섭을 최소화하는 것이 중요하다. DCSK(Differential Chaos Shift Keying)나 CDSK(Correlation Delay Shift Keying)와 같은 비선형 시스템에서는 정보를 효율적으로 부호화하여 보안성을 높이고 외부 요인의 간섭을 최소화시키는 방법으로 카오스 통신 시스템을 많이 사용하고 있다. 본 논문에서는 DCSK 방식과 CDSK 방식에 카오스 맵을 적용하여 카오스 통신 시스템의 BER 성능과 정보의 항재밍 특성을 평가한다. 시뮬레이션을 통해 Gauss iterated map이 다른 3개의 카오스 맵보다 좋은 성능을 얻을 수 있다는 것을 알 수 있다. 또한, DCSK 방식과 CDSK 방식은 카오스 맵을 적용함으로써 더 좋은 항재밍 특성을 얻을 수 있다. Digital communication technology have been focused on the higher data efficiency and the effective coding of information. Also, it is very important to improve security and minimize the interference of the external sources, Chaos communications system is studied to improve security and minimize the interference by effective encoding of information in the nonlinear systems such as DCSK(Differential Chaos Shift Keying) and CDSK(Correlation Delay Shift Keying). In this paper, we evaluate anti-jamming performance of chaos communications system using the DCSK and CDSK system. The simulation results show that the Gauss iterated map has better BER performance than the other maps(tent map, logistic map, Henon map). Also, DCSK and CDSK system can get the better anti-jamming performance by applying different chaotic maps.

Design of a High-Data-Rate Differential Chaos-Shift Keying System

In a differential chaos-shift keying (DCSK) system, the reference and information chaotic bearing signals are transmitted in two consecutive time slots and require the presence of delay components in the modulator and demodulator circuits. This system design requires a difficult-to-implement radio-frequency delay line that limits the data rate. The code-shifted DCSK (CS-DCSK) system proposes a solution for these problems by spreading the two chaotic slots by Walsh codes instead of using a time delay and sending them during the same time interval. In this brief, we extend the study of the CS-DCSK system, and we design two versions of a high-data-rate CS-DCSK system, which increase the data rate and can also perform in a multiuser case. The idea to achieve a high data rate is to get the information bits to share the same reference chaotic slot, where their separation is assured and maintained by different chaotic signals. In addition, this new design is not limited to a restricted number of Walsh codes such as CS-DCSK and provides from the properties of the chaotic signal in terms of security and good correlation properties. Finally, the performances of the systems are analyzed.

A Noise Eliminating Method of DCSK System Based on Multi-Layered Noise Control Materials

This paper proposes a new chaotic communication scheme which is developed from Differential Chaos Shift Keying (DCSK), named reversed-phase overlay DCSK. Different from DCSK, at the receiver of the improved scheme the first and the second half-symbol signals within a code period are reversed-phase overlapped before the correlation operation. Both the theoretical analysis and the simulation results show that the proposed scheme can effectively suppress the noise and improve the BER performance of DCSK if the channel noise in the first half of a code period and the second is positively correlated. The proposed scheme can be applied to the communication systems suffering with colored noise, such as Low-voltage Power Line Communication(L-PLC) system

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 Generalized BER Prediction Method for Differential Chaos Shift Keying System Through Different Communication Channels

In this paper, we present a generalized accurate methodology to predict the bit error rate performance for non-coherent chaos-based communication systems. The Gaussian approximation approach, which is widely used to compute the performance of such systems, leads to inaccurate results, especially with respect to low spreading factors. Our new approach based on the chaos bit energy distribution gives accurate results even for low spreading factors. The system is studied and simulated under an additive white Gaussian noise, Rice and Rayleigh channels. Finally, we compare our approach to the Gaussian approximation approach. Computer simulations shows a high accuracy for our method, especially for small spreading factors.

Performance Analysis and Optimization of Multi-User Differential Chaos-Shift Keying Communication Systems

Bit-error rate (BER) performance of a generalized multi-user differential chaos-shift-keying (DCSK) digital communication system is analyzed and optimized in this paper using baseband models. The generalized version of DSCK involves use of multiple nonrepeating chaotic spreading segments and energy adjustments and allows considerable system optimization. Theoretical BER analysis of correlation decoders based on a mathematical two-stage exact conditional approach is given as the foundation of subsequent performance studies. The consequent fully theoretical BER result gives an odd-symmetric spreading map condition for the BER to be unaffected by the mix of transmitted bits. The basis of the theoretical result is used to improve on the traditional simple Gaussian approximation (SGA) approach to the calculation of BER; this is inaccurate because it does not recognise the chaotic dynamics of DCSK. To overcome this drawback, a dynamically improved Gaussian approximation (DIGA) is developed. The DIGA approach is compared with the SGA approach, with simulation results demonstrating its accuracy and efficiency, certainly for more than five to ten users. Not only does the DIGA approach provide a more accurate BER than the SGA approach, its simple form also makes optimization of the DCSK system practically possible. The BER lower bound for the multi-user DCSK system is deduced from the DIGA approach. It is shown how the parameters and structure of the multi-user DCSK communication system can be optimized to achieve this lower bound. The work gives an exact theoretical basis of DCSK and covers several aspects which have not been treated in earlier research or have been inexactly treated.

A subspace theory for differential chaos-shift keying

In this brief, we introduce a subspace theory for differential chaos-shift keying (DCSK) systems. We show that DCSK systems operate by transmission of chaotic signals residing in a low-dimensional subspace. The subspace formalism of DCSK schemes leads to the derivation of useful subspace detectors that can be applied to decode the DCSK signal for various types of channels. Closed form expressions for the bit error rate is derived for an M-ary FM-version of DCSK, under the assumption of orthogonal subspace generating vectors. Numerical simulations demonstrate that the proposed subspace detector in general outperforms the conventional correlation detector for DCSK

Performance of Differential Chaos-Shift-Keying Digital Communication Systems Over a Multipath Fading Channel With Delay Spread

The performance of the noncoherent differential chaos-shift-keying (DCSK) communication system over a multipath fading channel with delay spread is evaluated. Analytical expressions of the bit error rates are derived under the assumption of an independent Rayleigh fading two-ray channel model. Analytical and simulated results are presented and compared. The multipath performance of the DCSK system is also compared with that of the coherent CSK system as well as conventional generic waveform communication schemes.

Permutation-based DCSK and multiple-access DCSK systems

This paper presents a method for enhancing the differential chaos-shift-keying (DCSK) and multiple access DCSK systems. By introducing a permutation transformation which destroys the similarity between the reference and data samples in a DCSK system, the bit rate can be made undetectable from the frequency spectrum, thereby enhancing the data security. Using different transformations for different users, the interference between users in a multiple-access system can be minimized, and each symbol is ensured to be sent within one bit duration for all users. Furthermore, the implementation requires only slight modification to the original DCSK system.

Anti-jamming performance of chaotic digital communication systems

Among the various modulation schemes proposed for chaos-based digital communications, chaos-shift keying (CSK) and differential chaos-shift keying (DCSK) have been most thoroughly analyzed and considered for practical implementation. One important aspect of performance of any communication system is the ability to resist jamming. This area of study, however, is not available in the literature. In this paper, an analysis of antijamming performance of the coherent CSK and noncoherent DCSK systems is presented. The study includes performance analysis for the two types of systems in terms of the bit error probability under different levels of noise power, jamming power, jamming frequency and spreading factor. Computer simulations are used to verify the analytical results.

Application of noise reduction to chaotic communications: a case study

Over the past few years, several methods have been proposed for decontaminating noisy chaotic signals by exploiting the short-term predictability of chaotic signals. This work evaluates the effectiveness, for a differential chaos shift keying (DCSK) telecommunications system, of a noise reduction approach using a deterministic optimization technique. Noise reduction is governed by a cost function which consists of two terms: the first gives the distance between the noisy and enhanced orbits, while the second one checks the dynamics of the cleaned signal. These two terms are weighted by a scalar /spl Gamma/. The effect of this factor on the noise reduction performance is also studied. Evaluation of the noise performance of a telecommunication system by computer simulation requires a very long simulation time. We propose a computationally-efficient criterion for quantifying the performance improvement of a DCSK system. We show that the noise reduction technique improves the overall noise performance only if the energy per bit-to-noise spectral density (E/sub b//N/sub 0/) exceeds a certain threshold. The effect of code length on this threshold level is also evaluated. Finally, the effect of parameter mismatch, which is present in every practical system, is analyzed.