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
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
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
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
针对Chirp基调制信号在分数阶傅里叶变换域特征明显,信号周期易被检测等问题,提出一种能够实现多域隐蔽的低检测概率(low probability of detection,LPD)波形构造方法。该方法采用分数阶傅里叶变换跳频(fractional Fourier transform-fr...针对Chirp基调制信号在分数阶傅里叶变换域特征明显,信号周期易被检测等问题,提出一种能够实现多域隐蔽的低检测概率(low probability of detection,LPD)波形构造方法。该方法采用分数阶傅里叶变换跳频(fractional Fourier transform-frequency hopping,FrFT-FH)架构,在不改变Chirp信号扩频增益的前提下,通过时宽分割和重组(time width division and reorganization,TDR),降低信号在分数阶傅里叶变换域和周期域的能量聚敛特性。仿真结果表明,相较于现有LPD波形只能实现单一特征域隐蔽的问题,所提波形在不影响系统通信性能的前提下,面对频域检测、分数阶傅里叶变换域检测、周期域检测多种检测手段,在10 dB信噪比条件下的信号检测概率均低于0.2,满足系统在不同特征域下的LPD需求。展开更多
Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochann...Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochannel interference （CCI） can seriously harm the system＇s performance. On the basis of the analysis of the CCI pattern of frequency hopped multiple access signal, a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems is proposed. In the proposed scheme, the CCI is canceled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both the theoretical analysis and computer simulation results show that compared to the conventional detector and Mabuchi＇s detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise （AWGN） channels and Rayleigh fading channels.展开更多
Diversity combining technologies are analyzed for fast frequency-hopping spread spectrum systems during partial-band noise jamming to develop a novel combining receiver called an Adaptive Threshold Clipper Combining R...Diversity combining technologies are analyzed for fast frequency-hopping spread spectrum systems during partial-band noise jamming to develop a novel combining receiver called an Adaptive Threshold Clipper Combining Receiver (ATCCR). The optimal clipping level for an ATCCR is analyzed, computed, and compared with several other diversity combining technologies. Since the ATCCR can estimate the power of the jamming and the number of jammed frequency cells to adaptively adjust the clipper's threshold, the system performance using the adaptive threshold clipper combining technique can be greatly improved.展开更多
An signal noise ratio（ SNR） adaptive sorting algorithm using the time-frequency（ TF）sparsity of frequency-hopping（ FH） signal is proposed in this paper. Firstly,the Gabor transformation is used as TF transformat...An signal noise ratio（ SNR） adaptive sorting algorithm using the time-frequency（ TF）sparsity of frequency-hopping（ FH） signal is proposed in this paper. Firstly,the Gabor transformation is used as TF transformation in the system and a sorting model is established under undetermined condition; then the SNR adaptive pivot threshold setting method is used to find the TF single source. The mixed matrix is estimated according to the TF matrix of single source. Lastly,signal sorting is realized through improved subspace projection combined with relative power deviation of source. Theoretical analysis and simulation results showthat this algorithm has good effectiveness and performance.展开更多
基金Supported by the National Nature Science Foundation of China(61072048)
文摘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.
基金the National Natural Science Foundation of China (No.90604035 and 60572142)the Program for New Century Excellent Talents in University (NCET) (No.NECT-05-0795).
文摘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.
基金supported by the Important National Science and Technology Specific Project of China(2018ZX03001020-0052016ZX03001022-006)+2 种基金the National Natural Science Foundation of China(61771308)the Shanghai Science and Technology Committee(16DZ1100402)the Special Project of Military and Civilian Integration of Shanghai Economic and Information Committee with the name"Ultra High Sensitivity UAV Communication System Based on Radar Related Technology"
文摘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.
基金National Natural F oundation of China(No.60 0 72 0 2 8) and High Technology Research and Developm entProgramm e of China(No.2 0 0 1AA12 3 0 14 )
文摘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.
文摘针对Chirp基调制信号在分数阶傅里叶变换域特征明显,信号周期易被检测等问题,提出一种能够实现多域隐蔽的低检测概率(low probability of detection,LPD)波形构造方法。该方法采用分数阶傅里叶变换跳频(fractional Fourier transform-frequency hopping,FrFT-FH)架构,在不改变Chirp信号扩频增益的前提下,通过时宽分割和重组(time width division and reorganization,TDR),降低信号在分数阶傅里叶变换域和周期域的能量聚敛特性。仿真结果表明,相较于现有LPD波形只能实现单一特征域隐蔽的问题,所提波形在不影响系统通信性能的前提下,面对频域检测、分数阶傅里叶变换域检测、周期域检测多种检测手段,在10 dB信噪比条件下的信号检测概率均低于0.2,满足系统在不同特征域下的LPD需求。
基金the National Natural Science Foundation of China (60372055)National Doctoral Foundation of China (20030698027).
文摘Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochannel interference （CCI） can seriously harm the system＇s performance. On the basis of the analysis of the CCI pattern of frequency hopped multiple access signal, a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems is proposed. In the proposed scheme, the CCI is canceled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both the theoretical analysis and computer simulation results show that compared to the conventional detector and Mabuchi＇s detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise （AWGN） channels and Rayleigh fading channels.
文摘Diversity combining technologies are analyzed for fast frequency-hopping spread spectrum systems during partial-band noise jamming to develop a novel combining receiver called an Adaptive Threshold Clipper Combining Receiver (ATCCR). The optimal clipping level for an ATCCR is analyzed, computed, and compared with several other diversity combining technologies. Since the ATCCR can estimate the power of the jamming and the number of jammed frequency cells to adaptively adjust the clipper's threshold, the system performance using the adaptive threshold clipper combining technique can be greatly improved.
基金Supported by the National Natural Science Foundation of China(64601500)
文摘An signal noise ratio（ SNR） adaptive sorting algorithm using the time-frequency（ TF）sparsity of frequency-hopping（ FH） signal is proposed in this paper. Firstly,the Gabor transformation is used as TF transformation in the system and a sorting model is established under undetermined condition; then the SNR adaptive pivot threshold setting method is used to find the TF single source. The mixed matrix is estimated according to the TF matrix of single source. Lastly,signal sorting is realized through improved subspace projection combined with relative power deviation of source. Theoretical analysis and simulation results showthat this algorithm has good effectiveness and performance.
