Chaotic Frequency Hopping Research Articles

Improved Spectrum Coexistence in 2.4 GHz ISM Band Using Optimized Chaotic Frequency Hopping for Wi-Fi and Bluetooth Signals.

Efficiently managing coexistence is crucial for achieving high-quality wireless communication in the Industrial, Scientific, and Medical (ISM) band where multiple wireless communication systems operate. Coexistence problems between Wi-Fi and Bluetooth Low Energy (BLE) signals are especially significant due to their shared frequency band, which often leads to interference and a reduced performance for both systems. Therefore, effective coexistence management strategies are essential for ensuring the optimal performance of Wi-Fi and Bluetooth signals in the ISM band. In this paper, the authors conducted a study to investigate coexistence management in the ISM band by evaluating four frequency hopping techniques: random, chaotic, adaptive, and an optimized chaotic technique proposed by the authors. The optimized chaotic technique aimed to minimize interference and ensure zero self-interference among hopping BLE nodes by optimizing the update coefficient. Simulations were conducted in an environment with existing Wi-Fi signal interference and interfering Bluetooth nodes. The authors compared several performance metrics, including the total interference rate, total successful connection rate, and trial execution time for channel selection processing time. The results indicated that the proposed optimized chaotic frequency hopping technique achieved a better balance between reducing interference with Wi-Fi signals, achieving a high success rate for connecting BLE nodes, and requiring minimal trial execution time. This makes it a suitable technique for managing interference in wireless communication systems. While the proposed technique had a higher interference than the adaptive technique for small numbers of BLE nodes, for larger numbers of nodes it had a much lower interference than the adaptive technique. The proposed optimized chaotic frequency hopping technique provides a promising solution for effectively managing coexistence in the ISM band, particularly between Wi-Fi and BLE signals. It has the potential to improve the performance and quality of wireless communication systems.

Design and Processing of a Novel Chaos-Based Stepped Frequency Synthesized Wideband Radar Signal.

The linear stepped frequency and linear frequency shift keying (FSK) signal has been widely used in radar systems. However, such linear modulation signals suffer from the range–Doppler coupling that degrades radar multi-target resolution. Moreover, the fixed frequency-hopping or frequency-coded sequence can be easily predicted by the interception receiver in the electronic countermeasures (ECM) environments, which limits radar anti-jamming performance. In addition, the single FSK modulation reduces the radar low probability of intercept (LPI) performance, for it cannot achieve a large time–bandwidth product. To solve such problems, we propose a novel chaos-based stepped frequency (CSF) synthesized wideband signal in this paper. The signal introduces chaotic frequency hopping between the coherent stepped frequency pulses, and adopts a chaotic frequency shift keying (CFSK) and phase shift keying (PSK) composited coded modulation in a subpulse, called CSF-CFSK/PSK. Correspondingly, the processing method for the signal has been proposed. According to our theoretical analyses and the simulations, the proposed signal and processing method achieve better multi-target resolution and LPI performance. Furthermore, flexible modulation is able to increase the robustness against identification of the interception receiver and improve the anti-jamming performance of the radar.

Anti‐jamming communication for body area network using chaotic frequency hopping

The healthcare industries research trends focus on patient reliable communication and security is a paramount requirement of healthcare applications. Jamming in wireless communication medium has become a major research issue due to the ease of blocking communication in wireless networks and throughput degradation. The most commonly used technique to overcome jamming is frequency hopping (FH). However, in traditional FH pre-sharing of key for channel selection and a high-throughput overhead is required. So to overcome this pre-sharing of key and to increase the security chaotic frequency hopping (CFH) has been proposed. The design of chaos-based hop selection is a new development that offers improved performance in transmission of information without pre-shared key and also increases the security. The authors analysed the performance of proposed CFH system under different reactive jamming durations. The percentage of error reduction by the reactive jamming for jamming duration 0.01 and 0.05 s for FH and CFH is 55.03 and 84.24%, respectively. The obtained result shows that CFH is more secure and difficult to jam by the reactive jammer.

Frequency Hopping Prediction Based on Multi-Kernel SVM

The chaotic frequency hopping sequences possesses short-term predictability. Via the phase space reconstruction approach, we can get chaos attractors, and the problem of series prediction can be transformed into the regression problem of the chaotic attractors. This paper uses SVR method to deal with the prediction of frequency hopping sequences. After analyzing the characteristics of existing kernel functions, we produce a new multi-kernel function, which is used for the prediction of frequency hopping sequences. Experiments show the fine performances of our methods.

A New Chaotic FH Sequences Generator based On Dynamic Quantization

In this paper a chaotic frequency hopping sequences generator based on dynamic quantification is proposed to address the problem of phase space reconstruction attack. This method is based on twice divisions of dynamic system interval and rotated gear dynamic quantification. Analyzed by computer simulation and statistical methods, the paper compared the performance of the proposed scheme with the existed multi-value quantization chaotic frequency hopping sequences generator. Simulation results show that the proposed method has better multi-address performance than other methods, hence is suitable for the FH-CDMA communication systems.

Color image steganography scheme using set partitioning in hierarchical trees coding, digital Fourier transform and adaptive phase modulation

In this research of color image hidden scheme, we aim to conceal a secret image into the cover image of the same size without noticeable degradation. In our approach, discrete wavelet transform (DWT) and set partitioning in hierarchical trees (SPIHT) codec are used to obtain a low bit rate and high reconstructed quality image compression. In the embedding process, an adaptive phase modulation (APM) mechanism and discrete Fourier transform (DFT) were adopted for secret data embedding. Simultaneously, nearest phase modulations (NPM) was used to improve the imperceptibility and decrease degradation of cover image. Both the chaotic mechanism (CM) and frequency hopping (FH) structure were hired to enhance the security of the scheme. Comparing with other data-hiding techniques, our proposed method has three advantages. (A) The extracted secret image has high quality reconstruction by using SPIHT coder. (B) The stego-image possesses excellent imperceptibility without noticeable degradation because secret data was concealed in the phase by using APM and NPM. (C) Have very large embedding capacity, it allows the size of secret image to be the same as the cover image.

Structure of frequency hopping sequences family based on block cipher

A novel family of frequency-hopping (FH) sequences based on iterated block cipher is proposed for frequencyhopping multiple-access (FHMA) communications. The design offers a class of nonlinear FH codes with high security, large linear span and a uniform spread over the entire frequency bandwidth. Moreover, FH sequences among the family are independent from each other and they perform as well as random patterns in terms of multiple access interference in anti-jamming applications. With the performance of packet error and throughput for FHMA network being derived in theory, many numerical results of the 3DES sequences are presented, comparing with those of shift register sequences and chaotic FH sequences. Efficiently implemented in field programmable gate arrays (FPGA), the generator prototype of the proposed sequence has been realized and incorporated into fast FH radio.

Analysis of FHMA Performance on Block Cipher Based Frequency-Hopping Sequences

Based on the triple Data Encryption Standard (DES) block cipher frequency-hopping (FH) sequences, a kind of packet protocol for frequency-hopping multiple-access (FHMA) network is suggested in this paper. In theory, the performances of both the packet error and the throughput are derived, which shows that the ratio of the packet length M to the frequency slots number q is most key parameter to determine the FHMA system performance under the condition of large user number. Computer simulation results of 3-DES FH sequences compared with those of the chaotic FH sequences are also included to support our developments.

Mode-locking Stability Adjustment of a Kerr-lens Mode-locked Ti:sapphire Laser, Analyzed by a Recently Developed Real-time Spectrum Analyzer

This is a report on the mode-locking stability of a Kerr-lens mode-locked Ti:sapphire, measured by a newly developed noise measurement method. Mode-locking stability is monitored via a power spectrum, which is obtained by irradiating optical pulses onto a fast photodiode, and by processing the detected signal using a recently developed real-time spectrum analyzer. The mode-locking stability of the Ti:sapphire laser strongly depends on pump power and becomes unstable as pump power decreases from an optimum power level. Amplitude fluctuation and Q-switched mode-locking are notably observed as the main causes for a break in a continuous-wave (CW) mode-locking operation. Moreover, chaotic frequency hopping is observed in a Q-switched mode-locking operation. A real-time spectrum analyzer provides a time-varying power spectrum, which enables easy adjustment for stable CW mode-locking operation of ultra-fast solid state lasers.

Design and realization of an FPGA-based generator for chaotic frequency hopping sequences

Chaos-based pseudonoise (PN) sequences for spread spectrum (SS) communications ranks amongst the most promising applications of chaos to communications. This paper deals with the design and realization of a chaotic frequency hopping (FH) sequence generator that is compatible with current FH/SS technologies. A simplistic generator architecture adopting nonlinear auto-regressive (AR) filter structures is proposed, which is based on the random sequence model and the metric entropy criterion for generation of random sequences. Conventional PN sequences are employed to perturb the generator such that the resulted sequences fulfil the FH requirements on period and family size. In addition, a chaos-based FH sequence generator prototype is realized in field programmable gate arrays (FPGAs) and various tests are performed. The generator produces long period FH sequences with uniform distribution over the available bandwidth, large linear complexity as well as suboptimal Hamming correlation properties. Bit error rate (BER) performance of the chaos-based asynchronous FH/CDMA system is evaluated by means of computer simulation. These results suggest that the cost-effective and well-performing generator has the potential to be incorporated into existing FH systems.

Chaotic frequency hopping sequences

This letter describes a novel family of frequency hopping sequences generated by chaotic systems. The sequences give a uniform spread over the entire frequency bandwidth. In addition to having good Hamming correlation properties, they possess ideal linear span. The sequences produce almost as good performance as random hopping patterns when used in frequency hopping code-division multiple-access (FH/CDMA) systems. Many numerical examples based on a digital chaos generator are presented.