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A Synchronization Acquisition Algorithm Based on the Frequency Hopping Pulses Combining
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作者 She Honghan Cheng Yufan +4 位作者 Zhang Wenzihan Zhang Yaohui Zhao Yuheng Shen Haoran Mou Ying 《China Communications》 SCIE CSCD 2024年第4期74-87,共14页
As modern electromagnetic environments are more and more complex,the anti-interference performance of the synchronization acquisition is becoming vital in wireless communications.With the rapid development of the digi... As modern electromagnetic environments are more and more complex,the anti-interference performance of the synchronization acquisition is becoming vital in wireless communications.With the rapid development of the digital signal processing technologies,some synchronization acquisition algorithms for hybrid direct-sequence(DS)/frequency hopping(FH)spread spectrum communications have been proposed.However,these algorithms do not focus on the analysis and the design of the synchronization acquisition under typical interferences.In this paper,a synchronization acquisition algorithm based on the frequency hopping pulses combining(FHPC)is proposed.Specifically,the proposed algorithm is composed of two modules:an adaptive interference suppression(IS)module and an adaptive combining decision module.The adaptive IS module mitigates the effect of the interfered samples in the time-domain or the frequencydomain,and the adaptive combining decision module can utilize each frequency hopping pulse to construct an anti-interference decision metric and generate an adaptive acquisition decision threshold to complete the acquisition.Theory and simulation demonstrate that the proposed algorithm significantly enhances the antiinterference and anti-noise performances of the synchronization acquisition for hybrid DS/FH communications. 展开更多
关键词 adaptive anti-interference frequency hopping synchronization acquisition
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Gigahertz frequency hopping in an optical phase-locked loop for Raman lasers
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作者 毛德凯 税鸿冕 +3 位作者 殷国玲 彭鹏 王春唯 周小计 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第2期60-65,共6页
Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers.We demonstrate an innovative gigahertz frequency hopping appro... Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers.We demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop(OPLL),which finds practical application in an atomic gravimeter,where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman lasers.The method merges the advantages of rapid and extensive frequency hopping with the OPLL’s inherent low phase noise,and exhibits a versatile range of applications in compact laser systems,promising advancements in portable instruments. 展开更多
关键词 Raman lasers optical phase-locked loop frequency hopping
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Satellite Navigation Method Based on High-Speed Frequency Hopping Signal 被引量:1
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作者 En Yuan Peng Liu +4 位作者 Weiwei Chen Rui Wang Bing Xu Wenyu Zhang Yanqin Tang 《China Communications》 SCIE CSCD 2023年第7期321-337,共17页
Global navigation satellite system has been widely used,but it is vulnerable to jamming.In military satellite communications,frequency hopping(FH)signal is usually used for anti-jamming communications.If the FH signal... Global navigation satellite system has been widely used,but it is vulnerable to jamming.In military satellite communications,frequency hopping(FH)signal is usually used for anti-jamming communications.If the FH signal can be used in satellite navigation,the anti-jamming ability of satellite navigation can be improved.Although a recently proposed timefrequency matrix ranging method(TFMR)can use FH signals to realize pseudorange measurement,it cannot transmit navigation messages using the ranging signal which is crucial for satellite navigation.In this article,we propose dual-tone binary frequency shift keyingbased TFMR(DBFSK-TFMR).DBFSK-TFMR designs an extended time-frequency matrix(ETFM)and its generation algorithm,which can use the frequency differences in different dual-tone signals in ETFM to modulate data and eliminate the negative impact of data modulation on pseudorange measurement.Using ETFM,DBFSK-TFMR not only realizes the navigation message transmission but also ensures the precision and unambiguous measurement range of pseudorange measurement.DBFSK-TFMR can be used as an integrated solution for anti-jamming communication and navigation based on FH signals.Simulation results show that DBFSK-TFMR has almost the same ranging performance as TFMR. 展开更多
关键词 satellite navigation frequency hopping RANGING navigation message transmission
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A Fine Synchronization Method for Coherent Fast Frequency Hopping
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作者 Xuanhe Yang Weike Zhang +3 位作者 Shixun Luo Chang Li Xiaqing Miao Aihua Wang 《China Communications》 SCIE CSCD 2023年第10期163-184,共22页
Coherent fast frequency hopping(CFFH)is attracting growing attention owing to its good antijamming performance and the coherent combining ability.However,compared with the conventional non-coherent fast frequency hopp... Coherent fast frequency hopping(CFFH)is attracting growing attention owing to its good antijamming performance and the coherent combining ability.However,compared with the conventional non-coherent fast frequency hopping,CFFH requires a more precise system synchronization.In this paper,we propose a new fine synchronization algorithm for CFFH.This algorithm consists two stages,namely,open-loop stage and closed-loop stage.In the openloop stage,a grid-based search parameter estimation method is proposed.In the closed-loop stage,we construct a fully coherent phase-locked loop(PLL)and a delay-locked loop(DLL)with decoding feedback structure to perform further fine estimation of the system clock skew and time delay,respectively.Moreover,we analyze the effect of the search parameter settings on the estimation error and derive the root mean squared error(RMSE)of estimates in the steady state of the closed-loop stage.Finally,through simulation,the RMSE performance are compared with the corresponding Cramer-Rao low bound(CRLB)and conventional code loop estimation to show the effectiveness of proposed algorithm. 展开更多
关键词 fast frequency hopping(Ffh) spread spectrum communication fine synchronization
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CONSTRUCTION OF FREQUENCY HOPPING SEQUENCES WITH NO HIT ZONE 被引量:9
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作者 Ye Wenxia Fan Pingzhi 《Journal of Electronics(China)》 2007年第3期305-308,共4页
In this paper,a property of Frequency Hopping (FH) sequence set with No Hit Zone (NHZ) is analyzed. Based on matrix transform and mapping methods,respectively,two classes of NHZ FH sequences are presented. These NHZ F... In this paper,a property of Frequency Hopping (FH) sequence set with No Hit Zone (NHZ) is analyzed. Based on matrix transform and mapping methods,respectively,two classes of NHZ FH sequences are presented. These NHZ FH sequences have good Hamming auto-correlation and Hamming cross-correlation properties. FH Code-Division Multiple Access (FH-CDMA) communication systems employing such NHZ FH sequences will eliminate multiple-access interference if the maximum time delay is shorter than the length of the NHZ. 展开更多
关键词 frequency hopping (fh sequences Hamming correlation No Hit Zone (NHZ)
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Key technologies of frequency-hopping frequency synthesizer for Bluetooth RF front-end
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作者 徐勇 王志功 +3 位作者 李智群 章丽 闵锐 徐光辉 《Journal of Southeast University(English Edition)》 EI CAS 2005年第3期260-262,共3页
A scheme of a frequency-hopping frequency-synthesizer applied to a Bluetooth ratio frequency (RF) front-end is presented,and design of a voltage controlled oscillator (VCO) and dual-modulus prescaler are focused o... A scheme of a frequency-hopping frequency-synthesizer applied to a Bluetooth ratio frequency (RF) front-end is presented,and design of a voltage controlled oscillator (VCO) and dual-modulus prescaler are focused on.It is fabricated in a 0.18 μm mixed-signal CMOS (complementary metal-oxide-semiconductor transistor) process.The power dissipation of VCO is low and a stable performance is gained.The measured phase noise of VCO at 2.4 GHz is less than -114.32 dBc/Hz.The structure of the DMP is optimized and a novel D-latch integrated with "OR" logic gate is used.The measured results show that the chip can work well under a 1.8 V power supply.The power dissipation of the core part in a dual modulus prescaler is only 5.76 mW.An RMS jitter of 2 ps is measured on the output signal at 118.3 MHz.It is less than 0.02% of the clock period. 展开更多
关键词 BLUETOOTH frequency hopping frequency synthesizer voltage controlled oscillator (VCO) dualmodulus prescaler programmable divider
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Performance of Luby transform coded frequency hopping systems in partial-band jamming
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作者 卜祥元 邱源 +2 位作者 杨行 周荣花 马园园 《Journal of Beijing Institute of Technology》 EI CAS 2013年第3期367-373,共7页
Luby transform (LT) codes are proposed to suppress the effect of partial band noise jam- ming in frequency hopping (FH) communication systems. A decoding scheme for joint erasures of severely jammed symbols and er... Luby transform (LT) codes are proposed to suppress the effect of partial band noise jam- ming in frequency hopping (FH) communication systems. A decoding scheme for joint erasures of severely jammed symbols and error correction is proposed. If an uncorrectable error is detected, the receiver erases the jammed symbols and uses incremental redundancy to increase the error-correcting capability. The performance of LT codes, under power-oppressive partial band noise jamming ( PB- N J) with the additive white Gaussian noise (AWGN), is evaluated via simulation. Even if the jam- mer spreads its high power over half of the hopping bandwidth, LT codes are shown to achieve a tar- get bit error probability of 10 -5, demonstrating their effectiveness as high-performance codes to im- prove the ability of FH systems to combat varying partial band noise jamming. 展开更多
关键词 Luby transform (LT) codes frequency hopping (fh erasure-correcting partial bandnoise jamming (PBNJ) anti-jam
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Anti-follower jamming wide gap multi-pattern frequency hopping communication method 被引量:2
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作者 Yao-bei Wang Hou-de Quan +1 位作者 Hui-xian Sun Pei-zhang Cui 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2020年第2期453-459,共7页
This paper deals with the follower jamming(FJ)resistance for the frequency hopping(FH)communication system over additive white Gaussian noise(AWGN)channel.Conventional FH systems are susceptible to be jammed by FJ,and... This paper deals with the follower jamming(FJ)resistance for the frequency hopping(FH)communication system over additive white Gaussian noise(AWGN)channel.Conventional FH systems are susceptible to be jammed by FJ,and multi-pattern frequency hopping(MPFH)has good resistance to FJ.To further improve the FJ rejection capability of MPFH,we propose a wide gap multi-pattern frequency hopping(WGMPFH)scheme.WGMPFH uses channels to represent messages,and the data channel and complementary channel are hopping on orthogonal frequency slots according to wide gap FH patterns.The transmitted signal lures FJ to aim at the data channel and the complementary channel is away from FJ by adopting wide gap frequency patterns.FJ does not affect the complementary channel but increases the signal energy in the data channel,thus the effect of FJ is reduced.Its bit error rate(BER)is derived under FJ and the effects of three FJ parameters(tracking success probability,jamming duration ratio and jamming bandwidth ratio)on the BER performance of WGMPFH are investigated versus the co nventional FH/BFSK and MPFH system.Numerical and simulation results show that when under the worst-case FJ,the proposed WGMPFH outperforms the MPFH by about 1-3 dB and outperforms the conventional FH/BFSK by more than 4 dB.The proposed WGMPFH shows superior jamming rejection performance under FJ especially in severe signal-to-jamming ratio(SJR). 展开更多
关键词 frequency hopping communication Multi-pattern frequency hopping FOLLOWER jamming AWGN channel
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The Identification of Frequency Hopping Signal Using Compressive Sensing 被引量:3
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作者 Jia YUAN Pengwu TIAN Hongyi YU 《Communications and Network》 2009年第1期52-56,共5页
Compressive sensing (CS) creates a new framework of signal reconstruction or approximation from a smaller set of incoherent projection compared with the traditional Nyquist-rate sampling theory. Recently, it has been ... Compressive sensing (CS) creates a new framework of signal reconstruction or approximation from a smaller set of incoherent projection compared with the traditional Nyquist-rate sampling theory. Recently, it has been shown that CS can solve some signal processing problems given incoherent measurements without ever reconstructing the signals. Moreover, the number of measurements necessary for most compressive signal processing application such as detection, estimation and classification is lower than that necessary for signal reconstruction. Based on CS, this paper presents a novel identification algorithm of frequency hopping (FH) signals. Given the hop interval, the FH signals can be identified and the hopping frequencies can be estimated with a tiny number of measurements. Simulation results demonstrate that the method is effective and efficient. 展开更多
关键词 COMPRESSIVE SENSING frequency hopping SIGNAL identification
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The Linear Span of a Class of Optimal Frequency Hopping Sequences 被引量:1
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作者 高军涛 胡予濮 李雪莲 《China Communications》 SCIE CSCD 2011年第2期147-151,共5页
For the anti-jamming purpose,frequency hopping sequences are required to have a large linear span. In this paper,we firstly give the linear span of a class of optimal frequency hopping sequences. The results show that... For the anti-jamming purpose,frequency hopping sequences are required to have a large linear span. In this paper,we firstly give the linear span of a class of optimal frequency hopping sequences. The results show that the linear span is very small compared with their periods. To improve the linear span,we transform these optimal frequency hopping sequences into new optimal frequency hopping sequences with large linear span by using a general type of permutation polynomials over a finite field. Furthermore,we give the exact values of the linear span of the transformed optimal frequency hopping sequences. 展开更多
关键词 frequency hopping sequences linear span permutation polynomials optimal sets
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Novel Frequency Hopping Sequences Generator Based on AES Algorithm 被引量:2
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作者 李振荣 庄奕琪 +1 位作者 张博 张超 《Transactions of Tianjin University》 EI CAS 2010年第1期22-27,共6页
A novel frequency hopping(FH) sequences generator based on advanced encryption standard(AES) iterated block cipher is proposed for FH communication systems.The analysis shows that the FH sequences based on AES algorit... A novel frequency hopping(FH) sequences generator based on advanced encryption standard(AES) iterated block cipher is proposed for FH communication systems.The analysis shows that the FH sequences based on AES algorithm have good performance in uniformity, correlation, complexity and security.A high-speed, low-power and low-cost ASIC of FH sequences generator is implemented by optimizing the structure of S-Box and MixColumns of AES algorithm, proposing a hierarchical power management strategy, and applying ... 展开更多
关键词 frequency hopping sequences advanced encryption standard LOW-POWER LOW-COST application specific integrated circuit
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Anti-Jamming Performance of Fountain Coded Differential Frequency Hopping Systems in AWGN 被引量:2
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作者 ZHU Wenjie YI Benshun GAN Liangcai XIE Qiuying 《China Communications》 SCIE CSCD 2014年第A02期53-60,共8页
Based on the anti-jamming performance of differential frequency hopping (DFH) systems in Additive White Gaussian Noise (AWGN) channel, Fountain code is introduced to the DFH systems as the outer error correcting c... Based on the anti-jamming performance of differential frequency hopping (DFH) systems in Additive White Gaussian Noise (AWGN) channel, Fountain code is introduced to the DFH systems as the outer error correcting code in this paper to investigate the improvements against partial-band jamming over AWGN channel. The performance of Fountain coded DFH is theoretically analyzed and numerically simulated. The total frequency of hopping in the simulation is 16, and results show that, on one hand, when exact jamming state information (JSI) is available, and the number of jamming frequency is n= 16, the bit error rate (BER) of 10~3 is achieved with the signal to interference ratio (SIR) approximately 7.5 dB over AWGN channel, and the performance improves about 1-1.5dB compared with the no-coded system. When the number of jamming frequency is n=2, the performance increases 15-17dB. On the other hand, when JSI is unavailable, a joint JSI estimation and decoding algorithm is proposed. The BER of 10 3 is achieved with jamming-frequency n 16, SIR=8dB and signal noise ratio (SNR) 10dB over AWGN channel. It's proved that this algorithm provides robust anti-jamming pertbrmance even without JSI. The anti-jamming performance of Fountain coded DFH systems is obviously superior to no-coded DFH systems. 展开更多
关键词 differential frequency hopping partial- band jamming Fountain codes jamming state estimation
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New Iterated Decoding Algorithm Based on Differential Frequency Hopping System 被引量:1
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作者 梁富林 罗伟雄 《Journal of Beijing Institute of Technology》 EI CAS 2005年第1期27-31,共5页
A new iterated decoding algorithm is proposed for differential frequency hopping (DFH) encoder concatenated with multi-frequency shift-key (MFSK) modulator. According to the character of the frequency hopping (FH) pat... A new iterated decoding algorithm is proposed for differential frequency hopping (DFH) encoder concatenated with multi-frequency shift-key (MFSK) modulator. According to the character of the frequency hopping (FH) pattern trellis produced by DFH function, maximum a posteriori (MAP) probability theory is applied to realize the iterate decoding of it. Further, the initial conditions for the new iterate algorithm based on MAP algorithm are modified for better performance. Finally, the simulation result compared with that from traditional algorithms shows good anti-interference performance. 展开更多
关键词 differential frequency hopping (Dfh) maximum a posteriori (MAP) non-coherent detection
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Performance Improvement of Wireless Communications Using Frequency Hopping Spread Spectrum 被引量:1
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作者 Naser Hossein Motlagh 《International Journal of Communications, Network and System Sciences》 2010年第10期805-810,共6页
To improve the performance of short-range wireless communications, channel quality must be improved by avoiding interference and multi-path fading. Frequency hopping spread spectrum(FHSS) is a transmission technique w... To improve the performance of short-range wireless communications, channel quality must be improved by avoiding interference and multi-path fading. Frequency hopping spread spectrum(FHSS) is a transmission technique where the carrier hops from frequency to frequency. For frequency hopping a mechanism must be designed so that the data can be transmitted in a clear channel and avoid congested channels. Adaptive frequency hopping is a system which is used to improve immunity toward frequency interference by avoiding using congested frequency channels in hopping sequence. In this paper mathematical modelling is used to simulate and analyze the performance improvement by using FHSS with popular modulation schemes, and also the hopping channel situations are investigated. 展开更多
关键词 frequency hopping SPREAD SPECTRUM ADAPTIVE frequency hopping Performance Evaluation
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Multi-user performance analysis of differential frequency hopping system over Rayleigh-fading channel 被引量:2
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作者 陈智 《High Technology Letters》 EI CAS 2008年第2期147-153,共7页
A novel non-coherent detection scheme for differential frequency hopping(DFH)system is proposedin asynchronous multi-user environments over Rayleigh-fading channels.The synchronous and asyn-chronous multi-user perform... A novel non-coherent detection scheme for differential frequency hopping(DFH)system is proposedin asynchronous multi-user environments over Rayleigh-fading channels.The synchronous and asyn-chronous multi-user performances of DFH with the conventional detection scheme and this novel detectionscheme are analyzed,respectively.The performance results are validated with simulation.The results ofanalyses and simulations prove two conclusions.Firstly,the performance of asynchronous multi-user DFHsystem overcomes that of synchronous multi-user DFH system over Rayleigh-fading channel.Secondly,the novel detection scheme can achieve better performance than the conventional non-coherent detectionscheme in asynchronous multi-user environments. 展开更多
关键词 differential frequency hopping(Dfh) multi-user performance multi-access interfer-ence(MAI) Rayleigh-fading
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Frequency Hopping Spread Spectrum Security Improvement with Encrypted Spreading Codes in a Partial Band Noise Jamming Environment 被引量:1
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作者 Amirhossein Ebrahimzadeh Abolfazl Falahati 《Journal of Information Security》 2013年第1期1-6,共6页
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 unde... 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. 展开更多
关键词 frequency hopping SPREAD SPECTRUM KEY Distribution Centre KEY Encryption KEY Linear Feedback Shift REGISTER frequency hopping Code Division Multiple Access Direct Sequence SPREAD SPECTRUM
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High Secure Sequence Design in Frequency Hopping Communications 被引量:1
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作者 Rui Chen Zan Li +2 位作者 Jia Shi Lei Guan Jiankang Zhang 《China Communications》 SCIE CSCD 2019年第4期139-150,共12页
Frequency-hopping(FH) technique is widely used in high-secure communications by exploiting its capabilities of mitigating interference and confidentiality. However, electronic attacks in wireless systems become more a... Frequency-hopping(FH) technique is widely used in high-secure communications by exploiting its capabilities of mitigating interference and confidentiality. However, electronic attacks in wireless systems become more and more rigorous, which poses huge challenges to the use of the number theory based and chaos theory assisted sequences. The structure of the FH sequence directly affects the performance of FH communication systems. In this paper, the novel FH sequence generation scheme is proposed with the aid of the so-called Government Standard(GOST) algorithm, which achieves a promising balance between efficiency and security. Moreover, the security performance of the proposed algorithm is analyzed, which reveals that it is more resistant to impossible differential attacks than the widely-used Data Encryption Standard(DES) algorithm. The numerical results show that the FH sequences generated by the GOST algorithm significantly outperform the ones generated by the DES algorithm and chaotic theory in terms of the randomness and complexity. 展开更多
关键词 frequency-hopping SEQUENCE CRYPTOGRAPHIC algorithm SECURITY RANDOMNESS COMPLEXITY
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Frequency hopping in IEEE 802.15.4 to mitigate IEEE 802.11 interference and fading
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作者 JAVED Umer HE Di +1 位作者 LIU Peilin YANG Yueming 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2018年第3期445-455,共11页
In this paper, we investigate the issues of initialization and deployment of wireless sensor networks(WSNs) under IEEE 802.11 b/g interference and fading channels using frequency hopping(FH). We propose an FH algo... In this paper, we investigate the issues of initialization and deployment of wireless sensor networks(WSNs) under IEEE 802.11 b/g interference and fading channels using frequency hopping(FH). We propose an FH algorithm for WSNs, which is implemented and tested with a pair of nodes employing IPv6 over low power wireless personal area networks(6 LoWPAN) standard.The merits and demerits of the proposed FH scheme in WSNs are studied under strong IEEE 802.11 b/g interference and frequency selective fading channels. We compare the performance results of the proposed FH scheme with those obtained by single-channel radio in WSNs, and show that FH maintains very reliable data rates in the presence of adverse conditions where the single-channel radio fails. We determine a minimum center frequency offset of channels between IEEE 802.15.4 and IEEE 802.11 b/g-based networks, which guarantees the error free network operation of IEEE802.15.4 using a single channel. We design a second FH procedure comprising only four free channels(15, 20, 25, and 26) of IEEE 802.15.4 standard, and show that in the presence of nearby IEEE 802.11 b/g interference, the IEEE 802.15.4 data rate using this method is always 98% and more. 展开更多
关键词 IEEE 802.15.4 wireless sensor networks(WSNs) frequency hopping(fh interference avoidance COEXISTENCE
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PERFORMANCE ANALYSIS OF FREQUENCY HOPPING PACKET RADIO NETWORK WITH ACKNOLEDGEMENT TRAFFIC
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作者 Tang Wei Zhang Naitong (Communication Research Center, Harbin Institute of Technology, Harbin 150001) 《Journal of Electronics(China)》 2000年第1期15-24,共10页
Performance analysis of an asynchronous frequency hopping packet radio network and numerical results are given. The network has mixed traffic, one type of packet needs an Acknowledgement(Ack), the other type does not ... Performance analysis of an asynchronous frequency hopping packet radio network and numerical results are given. The network has mixed traffic, one type of packet needs an Acknowledgement(Ack), the other type does not need, the background of such a network is tactical missile systems. A reasonable network model is given, based on which the effect of various parameters under multiaccess interference is investigated. The performance curves of throughput and average packet delay is given in this paper. 展开更多
关键词 frequency hopping PACKET RADIO network ACKNOWLEDGEMENT
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A Novel Complexity Metric of Frequency Hopping Sequences
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作者 蔡觉平 宋文涛 罗汉文 《Journal of Shanghai Jiaotong university(Science)》 EI 2004年第1期63-67,共5页
This paper made use of approximate entropy (ApEn) to evaluate the complexities of frequency-hopping (FH) sequences. By defining the maximal randomness of sequences with arbitrary lengths, ApEn can classify different c... This paper made use of approximate entropy (ApEn) to evaluate the complexities of frequency-hopping (FH) sequences. By defining the maximal randomness of sequences with arbitrary lengths, ApEn can classify different complex systems including stochastic processes, deterministic random process and random processes. It modified the conventional ApEn, which is used for continuous data sequence, for the discrete FH sequences. Two important theorems were given and the related main parameters were discussed. The algorithm was tested with several families of FH sequences. The simulation results show that ApEn is able to discern the changing complexities of FH sequences with a relatively small amount of samples of sequences. 展开更多
关键词 frequency hopping (fh) ENTROPY RANDOMNESS CRYPTOGRAPHY
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