High Efficiency Differential Chaos Shift Keying Research Articles

A New Receiver Design for Protograph-Coded Reference Reused DCSK Systems

In this letter, we investigate the performance of protograph-coded reference reused differential chaos shift keying (DCSK) systems to improve the transmission reliability. The traditional protograph-coded DCSK receiver does not take full advantage of the reused chaotic reference signals and hence cannot obtain desirable error performance. To solve this problem, we design a new receiver architecture called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">weighted reference estimation and iterative decoding (WRE-ID)</i> , which can universally improve the performance of protograph-coded reference reused DCSK systems over both multipath Rayleigh fading and additive white Gaussian noise channels. In particular, we put forward the WRE algorithm to estimate reference signal in order to calculate log-likelihood ratio (LLR) more precisely. Furthermore, extrinsic information output from the decoder is utilized to iteratively recalculate the weight of the WRE algorithm. As a further illustration, we derive the LLR expressions of the proposed WRE-ID-aided receiver of a typical protograph-coded reference reused DCSK (i.e., high-efficiency DCSK) system. Analytical and simulated results show that the proposed WRE-ID-aided receiver can always overtake the traditional receivers in reference reused DCSK systems. Hence, the protograph-based reference reused DCSK systems with the proposed receiver are very promising for high-rate high-reliability wireless applications.

Performance analysis of MISO-MU-OHE-DCSK system over Rayleigh fading channels

In this paper, a novel non-coherent communication system, multi-user orthogonal high efficiency differential chaos shift keying (MU-OHE-DCSK) system is presented. In the proposed system, by using an orthogonal chaotic generator (OCG) to generate two orthogonal chaotic signals, therefore the intra-signal interference components in MU-OHE-DCSK are eliminated. As in high efficiency differential chaos shift keying (HE-DCSK), the reference signal is transmitted in the first time slot. The 2N data bits are spread by chaotic sequence and then separated through Walsh codes in the second time slot of the frame. As a result, the superiority of this proposed system is that it can enhance the spectral efficiency when compared with DCSK and HE-DCSK. Furthermore, using multiple antennas at the transmitter end, this system can inhibit the channel fading problem and then obtain more diversity gain. The BER formula of multiple-input single-output MU-OHE-DCSK (MISO-MU-OHE-DCSK) is derived under the assumption of the proposed system over Rayleigh fading channels, respectively. Theoretical analysis is consistent with simulation results and shows that the new system outperforms other DCSK-based systems.

Chaos-Based Underwater Communication With Arbitrary Transducers and Bandwidth

In this work, an enhanced differential chaos shift keying (DCSK), based on a first order hybrid chaotic system, is being proposed for a high reliability underwater acoustic communication system. It can be integrated into systems that use standard existing transducers. We show that a coherent operation between the received signal and the time reversal of the basis function in a first order hybrid chaotic system maximizes the signal to noise ratio at the receiver. Concurrently, DCSK configuration is used to resist the distortion caused by the complex underwater acoustic channel. Our simulation results show that the proposed method has lower bit error rate (BER). In addition, it shows higher communication reliability over underwater acoustic channel as compared to the conventional DCSK using logistic map and its variant forms such as Correlation Delay Shift Keying (CDSK), Phase-Separate DCSK (PS-DCSK), High Efficiency DCSK (HE-DCSK), and Reference Modulated DCSK (RM-DCSK).

Bit-Error-Rate Evaluation of High-Efficiency Differential-Chaos-Shift-Keying System Over Wireless Channels

A high-efficiency differential-chaos-shift-keying (HE-DCSK) system has been proposed previously for the improvement of both bit-rate and bit-error-rate (BER) performance in comparison with the conventional DCSK system. This improvement made HE-DCSK be a promising solution for chaos-based communications. However, the performance of this system was just investigated under an additive white Gaussian noise (AWGN) channel. This is main motivation for our work to evaluate the performance of HE-DCSK over a typical wireless channel which is simultaneously affected by white noise, fading, multipath, and delay spread. The operation of the transmitter and receiver over the wireless channel is modeled and described. The BER performance is evaluated by theoretical analysis using Gaussian approximation and discrete integration. The numerical results obtained by Monte Carlo simulations are presented to verify the analyzed performance. Obtained results point out that the HE-DCSK system not only performs better than other DCSK-based ones under wireless channels but also can exploit the multipath characteristic to improve the performance.

Very high efficiency differential chaos shift keying system

In this study, a new non-coherent communication system, i.e. very high efficiency differential chaos shift keying system, is proposed. This system is a generalised form of the high efficiency differential chaos shift keying (HE-DCSK) system, with an arbitrary number (N) of transmitted bits per frame. The major advantage of this new proposition is its ability to significantly improve the spectral efficiency compared with DCSK and HE-DCSK. The theoretical bit error rate of this system is found using the Gaussian approximation method under different communication channels: additive white Gaussian noise and two-ray Rayleigh fading channels. Simulations in both environments show a perfect match with the analytical expressions for large spreading factors. Simulation results for the two-ray Rayleigh fading channel show clearly the diversity gain compared with the single-ray Rayleigh channel.

Reference flipped-differential chaos ‎shift keying scheme for chaos- based ‎communications

In this paper, a new differential coherent chaos-based communication system is proposed and named Reference Flipped-DCSK (RF-DCSK). By utilizing the low correlation value between a chaotic segment and its flipped version, each transmitted signal will be the sum of the information bearing signal and the mirrored version of the reference signal. This enhances the bandwidth efficiency of DCSK by doubling bits rate. Additionally, noise performance is improved at typical values of the spreading factor. According to Gaussian approximation method, theoretical expression for Bit-Error-Rate (BER) is derived. The proposed scheme is simulated and compared with Differential Chaos Shift Keying (DCSK), Correlation Delay Shift Key (CDSK) and High Efficiency -Differential Chaos Shift Keying (HE-DCSK) schemes in Additive White Gaussian Noise (AWGN) environment. Effect of spreading factor is studied. Results show that the proposed scheme clearly outperforms other systems.

Simple intra-signal-interference removing detector for HE-DCSK

In this paper, a novel simple detector is designed to remove the intra-signal interference in high efficiency differential chaos shift keying (HE-DCSK) modulation scheme. With the help of data bit estimated before correlation detection, this new detector could remove the modulated chaotic segment that would form intra-signal interference component in the correlator output from every received information-bearing signal in HE-DCSK, leading to greatly and effectively improved system bit error rate (BER) performance. The effectiveness of this proposed detector is studied analytically based on the numerical integration method and evaluated by computer simulation in additive-white-Gaussian- noise (AWGN) channel. Simulation results reveal that the proposed detector can dramatically improve the overall BER performance of HE-DCSK even at relatively low signal noise ratio (SNR) levels.

High-Efficiency Differential-Chaos-Shift-Keying Scheme for Chaos-Based Noncoherent Communication

In this brief, a new noncoherent chaos-based communication scheme, named high-efficiency differential chaos shift keying (DCSK) (HE-DCSK), is proposed. By recycling each reference sample in DCSK, 2 bits of data can be carried in one data-modulated sample sequence, which offers our scheme double bandwidth efficiency and nonrepeated transmitted signal less prone to interception in comparison to DCSK. The bit-error performance of the proposed scheme is studied analytically based on Gaussian approximation for discrete-time implementations. Simulations in additive-white-Gaussian-noise channel are performed and compared with DCSK and correlation delay shift keying (CDSK) schemes. Results show that the bit-error rate performance of HE-DCSK can always outperform CDSK and be even better than DCSK with typical spreading factors and at reasonable E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> levels.