Analysis performance of MC-CDMA communication system based on improved Chebyshev sequence

The research on the balance of chaotic sequence has important significance to spread-spectrum communication. The relationship between the balance and the parameter of four typical chaotic maps (Chebyshev, improved Logistic, Logistic and Tent) was discussed. The new numeric ranges of initial value and fractal parameter were decided, which provided reference for the generation of chaotic spread-spectrum sequence. Through the graphs of the four chaotic sequences' balance and the error-bit rate performance of these systems with the four chaotic sequences' map parameters, the new numeric ranges were validated. Both simulation results and the analysis show that the balance of Chebyshev is the best.

In this paper, we conduct research on effective and robust time-delay estimation methodology for spread spectrum communications. The development of underwater acoustic spread spectrum communication technology derived from the demand for underwater remote, reliable communication. Due to the underwater acoustic channel belt width, background noise and high rate of Doppler frequency shift, severe multipath effect, absorption problems such as uneven, makes the communication quality serious decline. We firstly analyze the fast time-delay estimators to serve as the prior knowledge, and later, we analyze the channel estimation techniques. Finally, we test the error and efficiency. Results show that the system has better ability to resist noise and multiple access interference, and improve the chaotic spread spectrum sequence to better the performance of the system of traditional chaotic spread spectrum sequence. The experimental result proves the effectiveness of proposed methodology. In the future, we plan to conduct more literature reviews to modify the current technique.

This paper proposes a method based on chaotic spread spectrum sequence for synchronous online diagnosis of intermittent faults for complex and cable. networks, such as the aircraft power system. The novelties of the proposed method include: 1) since chaotic spread spectrum signals are sensitive to initial values, the number of chaotic sequences are not limited and the proposed method is not limited by the number of cables under monitoring; 2) with the self-correlation characteristic and cross-correlation characteristic of chaotic sequence, the proposed method can be extended to online diagnosis of multiple cable intermittent faults; and 3) the signal source impedance amplification method is proposed for intermittent arc faults of multiple cables, which improves the reflection coefficient and increases the accuracy of online detection and location of intermittent arc faults. A series of simulations and experiments on multiple cables with different intermittent fault modes are conducted to verify the effectiveness of the proposed approaches.

At present, the spread spectrum (SS) sequences used in watermark include i.i.d. random sequences and the sequences used in SS communications. They appear earlier than digital watermark. Almost no researchers pay attention to whether they are really fit for watermark. In this paper, we compare the SS watermark channel and the traditional SS communication channel. We find out that their correlation property is different. Considering cropping and translation attacks, we define watermark auto- and cross-correlation and propose Loose Autocorrelation and Tight Cross-Correlation (LAC&TCC) properties for SS watermark. The LAC&TCC properties are that, whether or not synchronized, the autocorrelation is equal or close to 1 and the cross-correlation is equal or close to 0. Accordingly, the peak correlation is divided into the peak autocorrelation Ra(l) and the peak cross-correlation Rc(l). We establish the lower bound of Rc(l) and the higher bound of Ra(l), respectively. The two bounds indicate that, no matter how small the cover is reserved, the extractor can always find a threshold to distinguish auto- and cross-correlation in theory.

Communication using power line as a medium of signal transmission offers a convenient and inexpensive solution for multimedia signal transmission and control applications. This paper aims to present a de-noising scheme which is a combination between chaotic spread spectrum sequence system and the wavelet transform in power line communications (PLC). The proposed communication scheme is based on two key ideas. The first concept consists of the use of the spread-spectrum based on chaotic sequence in order to minimize interference caused by the power line and to secure the transmission information. The second idea consists of the use of discrete wavelet transform to reduce the noise from a chaotic sequence. Signal-to-noise (SNR) and root mean squared error (RMSE) are made. Analyses of bit error rate (BER) illustrate the superior communication performance of the proposed PLC de-noising scheme based on chaotic spread spectrum and wavelet.

Spread spectrum communication technology is one of the most critical core technologies in anti‐jamming satellite communication systems. However, it has certain technical limitations in anti‐jamming applications. For instance, frequency‐hopping spread spectrum technology exhibits weak resistance against spot jamming, while direct‐sequence spread spectrum technology is less effective in mitigating wideband interference. With the continuous development of satellite countermeasure technologies, these technical limitations will significantly constrain the performance of satellite communication systems and compromise the reliable transmission of space‐based information. Aiming at the technical limitations of spread spectrum anti‐jamming satellite communication, this paper proposes a solution based on blind source separation technology to enhance the anti‐jamming capability of spread spectrum communication. This paper establishes a blind source separation‐based anti‐jamming communication prototype system, verifying the feasibility of applying blind source separation to communication anti‐jamming. It conducts an in‐depth analysis of the characteristics and existing issues in spread spectrum anti‐jamming satellite communication systems, identifies the problems and challenges of applying blind source separation to such systems, and proposes potential solutions.

The paper contains an analysis of the basic criteria for the selection of spreading sequences for the multi-carrier CDMA (MC-CDMA) systems with spectrum spreading in the frequency domain. It is shown that the time-domain crosscorrelation function between the spreading sequences is not a proper interference measure for the asynchronous MC-CDMA users. Therefore the spectral correlation function is introduced and, together with the peak-to-average power ratio (PAPR) and the dynamic range of the corresponding multi-carrier waveforms, is used for the evaluation of MC-CDMA sequences. Some well-known classes of sequences, such as Walsh and Gold sequences, as well as orthogonal Gold and Zadoff-Chu (1972) sequences, are evaluated with respect to the aforementioned basic criteria. It is also shown that the multi-carrier spread spectrum waveforms based on the (multilevel) Huffman sequences have the lower PAPR than a single sine wave.

As the widely investigation of chaotic sequence in the application of communication, binary and quaternary phaseshift keying modes have been extensively adopted in spread spectrum communication. Based on Chebyshev chaotic mapping, binary-phase and quadric-phase chaotic spreading sequences are generated, and the relationship among the performance of balance and fractal parameter, initial value and the period of sequence are analyzed. The non-balanced points which should be avoided in the chaotic sequence when applying in CDMA system are proposed. Aiming at the problem which the conventional degree of balance functions only investigates the balance of the 2- valued sequence, the maximum balanced difference method is proposed. The definition of maximum balanced difference is proposed. We analyze the balance performance of quadric-phase Chebyshev sequence. Experimental results show that the maximum balanced difference function can replace the traditional binary-phase degree of balance function to research the balance of digital 2-valued and multi-valued sequence, which has better universality.

In this letter, the weighted fractional Fourier transform (WFRFT) is performed on the chaotic sequence to enhance the security of the chaotic direct sequence spread spectrum (CD3S) communication, and a WFRFT-CD3S system that spreads the information bits through the WFRFT-chaotic sequence is proposed. In the proposed system, the transmitter scrambles the phase space trajectory of the chaotic sequence through WFRFT and make the distribution of the transmitted signal be Gaussian-like. The receiver synchronizes the WFRFT-chaotic sequence through bidirectional correlation search and demodulates the information through the synchronized local WFRFT-chaotic sequence. Simulations are implemented to evaluate the security performance, synchronization performance, and demodulation performance of the proposed system.

This paper presents the performance analysis of compound chaotic sequence (CCS)-based noise reduction differential chaos shift keying (NR-DCSK) system under multipath Rayleigh fading channel conditions. The special characteristics of chaotic sequences are their deterministic randomness behaviour that adds security and multipath immunity to the data when used as a carrier in communication systems. In this paper, the chaotic sequences are generated by combining the outputs of chaotic maps, such as logistic map, Chebyshev map, Bernoulli shift map, tent map, etc., leading to new complex sequences known as CCSs. This sequence possesses more randomness, overcomes severe interference levels encountered during transmission and provides higher multipath immunity compared with those of pseudo-noise (PN) codes. Since NR-DCSK is a spread spectrum technique, its performance in wireless multipath fading channels has important considerations. The CCS is used as a carrier in NR-DCSK systems, which leads to improved bit error rate (BER) performance. Comparisons of simulation results to theoretical BER expressions of additive white Gaussian noise (AWGN) and Rayleigh fading channels have been carried out to test the efficiency of the proposed CCS-based NR-DCSK system.

To address the inability to quantitatively analyze the performance of the direct sequence spread spectrum (DSSS) communication system in the presence of short-period pseudo-noise (PN) sequences, this study derives the interference components resulting from correlation processing of single-frequency interference. Given the short period of the spread spectrum sequence used in underwater acoustic systems, a theoretical expression is proposed for analyzing the anti-single-frequency interference performance of DSSS communication systems in underwater acoustics. This expression combines the interference power output by the system to enable quantitative analysis. Simulations are conducted to validate the accuracy of the theoretical expression. The results reveal that the interference sequence generated by correlation processing assumes either a direct current (DC) or sinusoidal distribution. The bit error rate (BER) of the system is influenced by signal-to-interference ratio (SIR), interference frequency offset, phase deviation, and the structure of the spreading code itself. The BER exhibits regular variation with changes in the interference phase. In all working conditions where the interference frequency offset is an integer multiple of the bit bandwidth, single-frequency interference with a frequency offset equivalent to the bit bandwidth has the greatest impact on the system. The concise theoretical expression presented in this study has significant practical value as it allows for quick prediction of variation in the anti-single-frequency interference performance of underwater acoustic DSSS communication systems using short-period PN sequences.

The properties of chaotic maps based on Logistic map, Tent map, Improved Logistic map and Chebyshev map are analyzed in this paper .Then we discuss the performance of correlation, balance and run-length of the chaotic binary sequences . Simulation results show that the characteristics of chaotic sequences are similar to the traditional pseudo-random sequences, and chaotic sequence is suitable for direct sequence spread spectrum systems as spreading sequence.

Spread spectrum technology has been widely employed for positioning and communicating with autonomous underwater vehicles (AUVs), but conventional spread spectrum sequences lack confidentiality and reliability in UWA channel. Considering the limitations of conventional sequences and the characteristics of underwater acoustic (UWA) channel, a composite chaotic orthogonal sequence (CCOS) based on the UWA channel is proposed. The confidentiality of the CCOS is superior to that of the m‐sequence, while the autocorrelation performance of the CCOS is superior to that of the orthogonal sequence. Moreover, the CCOS can compensate for the imbalance of logistic chaotic sequence when assigned certain initial values. Acquisition is a crucial component of accessing the spread spectrum signal; therefore, the acquisition performance indicates the applicability of the CCOS. The source–target model is established to simulate communication with an underwater moving target. To simulate the acquisition process, a parallel algorithm based on fast Fourier transform is adopted, and the entire simulation process is completed based on the BELLHOP ray acoustic model. Through data processing, the Doppler shift error is less than half of the frequency‐search element. Furthermore, the acquisition probabilities of the CCOS with different numbers of bits are over 90%, which demonstrates the reliability of the CCOS.

The bandwidth ratio increasing of spread spectrum (SS) communication limits the performance of wideband adaptive interference cancellation (WAIC) for strong wideband interference signal. To improve the interference cancellation radio (ICR), wideband interference signal is divided into subbands to reduce the computational bandwidth of the WAIC algorithm. In this paper, a method that fits the wideband interference signal by multi-tone signals is proposed to explicitly analyze the effect of the signal bandwidth on the cancellation system and quantitatively calculate the analytical solution of the ICR. Basing on the method proposed, the performance can be evaluated by the amplitude and phase difference between the received signals from the main antenna and the auxiliary antenna. Simulations and experiments are conducted to verify the theoretical analysis, and the results are consistent. Therefore, the analytical method proposed in this paper provides the design guidelines between the ICR requirement and subband bandwidth, which can reduce the complexity in the implementation of the WAIC system.

Chaotic sequences have good correlation properties and they can be used as address sequences in Spread Spectrum Communication. Chaotic functions are highly sensitive to initial condition and exhibit non-linear behavior. In Chaotic spread spectrum communication systems, different user may be assigned different sequences generated with different initial conditions. Set of binary sequences with good pair wise cross- correlation property finds applications in Direct Sequence- Code Division Multiple Access (DS-CDMA) systems. Security in Direct Sequence-Code Division Multiple Access systems is relatively limited. To enhance security in Direct Sequence- Code Division Multiple Access systems, chaotic sequences are generated. In this paper we analyze the generation of chaotic binary sequences and study of auto correlation and cross correlation properties.