Chaotic Sequence Spread Spectrum Research Articles

Emerging 5G Multicarrier Chaotic Sequence Spread Spectrum Technology for Underwater Acoustic Communication

Generalized frequency division multiplexing (GFDM) is a newly introduced technique for the wireless fifth-generation (5G) standard based on multicarrier filter bank theory, which has the advantage of flexibility in setting the number of subcarriers and subblocks. The application of GFDM in underwater acoustic (UWA) communication can take full advantage of the limited spectral resources, which is a prime limitation in UWA communication and will promote the development of UWA network technology. However, the multicarrier communication technique utilized in radio 5G communication offers difficulty in channel estimation, and the influence of a channel cannot be ignored especially in the UWA communication field. Therefore, GFDM cannot be implemented directly in UWA communication; to solve this problem, a system combining chaotic sequence spread spectrum technology with GFDM is proposed, which is a novel technique with high spectrum efficiency. Simulation and experimental results verified the effectiveness of the proposed system.

Synchronous Online Diagnosis of Multiple Cable Intermittent Faults Based on Chaotic Spread Spectrum Sequence

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.

Anti-jamming performance analysis of optimal chaotic spread spectrum sequences

In order to improve the anti-jamming performance of Direct Sequence/Code Division Multiple Access (DS/CDMA) system based on chaotic sequences,an optimization algorithm for choosing chaotic sequences was proposed.The optimal improved Logistic-map chaotic sequences were applied to DS/CDMA system,and the anti-jamming performances were studied under different kinds of jamming such as single-frequency interference,partial-band interference,and impulsive interference.The results show that the optimal improved Logistic-map chaotic sequences have larger capacity,excellent anti-jamming ability,and lower Bit Error Rate (BER).Compared with the Gold sequence,with the same BER,SNR can be improved at least 2 dB,so they are more suitable for DS/CDMA system and anti-jamming technology.

Periodic performance of the chaotic spreadspectrum sequence on finite precision

It is well known that the periodic performance of spread spectrum sequence heavily affects the cor-relative and secure characteristics of communication systems. The chaotic binary sequence is paid more and moreattention since it is one kind of applicable spread spectrum sequences. However, there are unavoidable short cyclicproblems for chaotic binary sequences in finite precision. The chaotic binary sequence generating methods arestudied first. Then the short cyclic behavior of the chaotic sequences is analyzed in detail, which are generatedby quantification approaches with finite word-length. At the same time, a chaotic similar function is defined forpresenting the cyclic characteristics of the sequences. Based on these efforts, an improved method with scramblingcontrol for generating chaotic binary sequences is proposed. To quantitatively describe the improvement of periodicperformance of the sequences, an orthogonal estimator is also defined. Some simulating results are provided. Fromthe theoretical deduction and the experimental results, it is concluded that the proposed method can effectivelyincrease the period and raise the complexity of the chaotic sequences to some extent.

Balance analysis of four digital chaotic spread spectrum sequences

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.

A method for generating chaotic spread-spectrum sequences and their optimized selection algorithm

A method for generating chaotic spread-spectrum sequences based on the combined chaotic map is proposed. An optimized selection algorithm based on the property requirement of spread-spectrum sequences and the performance index of multiple access interference is also presented. Simulation is performed for the optimized chaotic sequence, and an optimized logistic sequence is applied to a direct sequence spread-spectrum CDMA system under different channel conditions. The results show that the chaotic spread-spectrum sequences generated by the proposed method have similar performance as the logistic spread-spectrum sequences and have better security.