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Frequency hopping does not increase anti-jamming resilience of wireless channels  [PDF]
Moritz Wiese,Panos Papadimitratos
Mathematics , 2015,
Abstract: The effectiveness of frequency hopping for anti-jamming protection of wireless channels is analyzed from an information-theoretic perspective. The sender can input its symbols into one of several frequency subbands at a time. Each subband channel is modeled as an additive noise channel. No common randomness between sender and receiver is assumed. It is shown that capacity is positive, and then equals the common randomness assisted (CR) capacity, if and only if the sender power strictly exceeds the jammer power. Thus compared to transmission over any fixed frequency subband, frequency hopping is not more resilient towards jamming, but it does increase the capacity. Upper and lower bounds on the CR capacity are provided.
非仿射系统的自适应观测器自抗扰控制  [PDF]
控制理论与应用 , 2014, DOI: 10.7641/CTA.2014.30551
Abstract: 研究了一类单输入单输出(SISO)非仿射非线性系统的控制问题,通过微分同胚变换以及自抗扰思想将该类形式转化成含有未知非线性且控制增益未知的仿射形式.引入扩展状态自适应观测器以及Nussbaum-type增益技术,利用积分反演和调节函数技术,设计了自抗扰控制器.从理论上证明了所设计的控制器能够保证闭环系统所有信号全局一致有界,并且证明了跟踪误差渐近收敛到零点的残集内.仿真例子验证了算法的有效性.
非仿射纯反馈非线性系统的自抗扰控制  [PDF]
程春华, 胡云安, 吴进华
自动化学报 , 2014, DOI: 10.3724/SP.J.1004.2014.01528
Abstract: ?针对一类具有外部扰动的不确定非仿射纯反馈非线性系统,结合反演和自抗扰技术,提出了一种新的控制设计方案,该方案中反演设计的每一步引入了自抗扰设计,同时采用微分器和扩展状态观测器分别估计虚拟控制的导数和系统的未知部分.与现有设计方法不同,它不是直接利用逼近定理来构建理想的控制器.该方案设计过程简单,并且通过输入状态稳定性分析证明了系统状态能渐近收敛到原点的任意小邻域内.仿真结果证实了该方法的有效性.
Frequency Hopping Spread Spectrum Security Improvement with Encrypted Spreading Codes in a Partial Band Noise Jamming Environment  [PDF]
Amirhossein Ebrahimzadeh, Abolfazl Falahati
Journal of Information Security (JIS) , 2013, DOI: 10.4236/jis.2013.41001

Frequency Hopping Spread Spectrum (FHSS) system is often deployed to protect wireless communication from jamming or to preclude undesired reception of the signal. Such themes can only be achieved if the jammer or undesired receiver does not have the knowledge of the spreading code. For this reason, unencrypted M-sequences are a deficient choice for the spreading code when a high level of security is required. The primary objective of this paper is to analyze vulnerability of linear feedback shift register (LFSRs) codes. Then, a new method based on encryption algorithm applied over spreading codes, named hidden frequency hopping is proposed to improve the security of FHSS. The proposed encryption security algorithm is highly reliable, and can be applied to all existing data communication systems based on spread spectrum techniques. Since the multi-user detection is an inherent characteristic for FHSS, the multi-user interference must be studied carefully. Hence, a new method called optimum pair “key-input” selection is proposed which reduces interference below the desired constant threshold.

Self-learning sliding-mode disturbance rejection control for non-affine systems

控制理论与应用 , 2016, DOI: 10.7641/CTA.2016.50636
Abstract: 针对一类单输入单输出(single-input single-output, SISO)非仿射非线性系统的控制问题, 提出了一种自学习 滑模抗扰控制方法. 该方法用非线性光滑函数设计扩张状态观测器, 实现SISO 非仿射非线性系统内部不确定性和 外部扰动的扩张状态估计, 并将扩张状态观测器(extended state observer, ESO)与自学习滑模控制技术融为一体, 实 现SISO非仿射非线性系统的自学习滑模抗扰控制. 该方法不依赖受控对象的数学模型, 可以快速跟踪任意给定的 参考信号. 数值仿真试验表明了该方法响应速度快、控制精度高, 具有很强的抗扰动能力, 因而是一种鲁棒稳定性很 强的控制方法, 在SISO非仿射非线性系统控制领域具有重要作用.
Disturbance rejection control (DRC) method with self-learning sliding mode (SLSM) is proposed for a class of single-input single-output (SISO) non-affine nonlinear systems (NANS). The proposed method realizes the extended state estimation of internal parameters perturbation and external disturbances of the NANS based on extended state observer (ESO) designed by nonlinear smooth function. Sliding mode disturbance rejection control (SMDRC) for SISO NANS with uncertainties and disturbance is realized by the technology based on the ESO combined with auto-learning sliding mode control (ALSMC). The method is not dependent on the mathematical model of the controlled plants, and can fast track any given reference signal. Numerical simulation results show that the proposed method not only has fast response, high control precision, but also has strong disturbance-rejection ability for the non-affine nonlinear systems with internal and external disturbance. So the proposed control method will play an important role in control field of the SISO NANS because of its strong robust stability.
Design of Constrained Signaling Frequency Hopping Sequence in Adaptive Frequency Hopping Radio

Zhang Xiao,Wu Qi-hui,Shi Zhao-wu,
张 晓

电子与信息学报 , 2007,
Abstract: Signaling transmission is the key technology for adaptive frequency hopping radio. In order to improve its safety and reliability, this paper provides a constrained signaling frequency hopping sequence by analyzing the performances and the limitations of the unconstrained signaling frequency-hopping sequence and the wide gap signaling frequency hopping sequence in fractional band jamming. Theory analysis and the simulation results show that the performance of the proposed sequence is better than those of the former two sequences.
Anti jamming method for frequency hopping communication based on BSS and wavelet denoising

- , 2015,
Abstract: 传统盲源分离技术中白化处理的降噪能力有限,导致其在低信噪比条件下效果不理想,制约了盲源分离技术在通信抗干扰领域的实际运用。针对这一问题,在基于盲源分离的跳频通信抗非相关干扰方法的框架基础上引入小波降噪,提出了对混有干扰的多路接收跳频信号先小波降噪预处理再盲源分离的方法。仿真结果表明,提出方法与已有的类似工作相比,能够在低信噪比条件下进一步改善跳频通信对抗强非相关干扰的误码性能。
The denoising ability of whitening procedure is limited, so the performance of traditional blind source separation(BSS) is severely affected by the noise level, holding back the application of BSS in communication anti jamming domain. In view of this, a wavelet denoising technique is introduced as a pre processing unit into the basic model of BSS based frequency hopping (FH) anti jamming against uncorrelated jamming. Firstly, wavelet denoising is used to enhance the signal to noise ratio(SNR)of the received signals, which are the mixture of jamming and the FH signal. Then, BSS is utilized to extract the desired FH signal. Simulation results indicate that the method is valid for multiple kinds of hostile uncorrelated jammings and exhibits superior performance when the SNR is lower
Performance Analysis of Differential Frequency Hopping System under Partial Band Noise Jamming

Chen Zhi,Li Shao-qian,Dong Bin-hong,

电子与信息学报 , 2007,
Abstract: This paper presents a new HF hopping system, which is called Differential Frequency Hopping (DFH) system. The frequencies transition function and the method of signal detection are the key technologies in this system. Detection and receiving symbol by symbol, detection by sequence and linear-combining receiving are two kinds of methods of signal detection and receiving. The performance of rejecting Partial Band Noise Jamming (PBNJ) by using these two methods is analyzed respectively in theory, and the corresponding simulation results are given, all these prove that the performance of DFH system with signal detection by sequence and linear-combining receiver is much better than conventional frequency hopping system under PBNJ.
Analysis of the Self-Interference Cancellation Capacity in Communication under Jamming Links

- , 2016, DOI: 10.3969/j.issn.1001-0548.2016.02.006
Abstract: 针对基于射频干扰对消的扰中通系统,本文研究了采用多抽头射频干扰重建技术可获得的自干扰抑制度,给出了抽头数为2的自干扰消除器的解析结构,并分析了干扰消除效果与信号带宽和抽头数的关系。数值分析与计算机仿真结果表明:干扰消除能力随信号带宽增大而减弱,随抽头数增加而提升,对于100 MHz带宽信号,6抽头射频对消器在S频段可提供约70 dB的自干扰消除能力。
浅析三异涤长丝仿毛织物的技术关键  [PDF]
纺织学报 , 1999,
Abstract: 本文简析了三异涤长丝仿毛织物开发过程,发现仿毛织物的研制与开发是一项系统工程,其中三异涤长丝、织造形式以及合理的碱减量技术是仿毛织物成功的技术关键。
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