The method of FRactional Fourier Transform (FRFT) is introduced to Transform Domain Communication System (TDCS) for signal transforming in the paper after theoretical analysis. The method yields optimal Basis Function...The method of FRactional Fourier Transform (FRFT) is introduced to Transform Domain Communication System (TDCS) for signal transforming in the paper after theoretical analysis. The method yields optimal Basis Function (BF) by FRFT with optimal transform angle. The TDCS using the proposed method has wider usable spectrum, stronger robustness and better ability of anti non-stationary jamming than using usual methods, such as Fourier Transform (FT), Auto Regressive (AR), Wavelet Transform (WT), etc. The main simulation results are as follows. First, the Bit Error Rate (BER) Pb is close to theoretical bound of no jamming no matter in single tone or in linear chirp interference. Second, the interference-to-signal ratio J /E is at least 12dB more than that of Direct Spread Spectrum System (DSSS) under the same BER if the spectrum hopping-to-signal ratio is 1:20 in chirp plus hopping interfering. Third, the Eb /N 0(when estimation difference is 90% between trans- mitter and receiver) is about 3.5dB or about 0.5dB (when estimation difference is 10% between transmitter and receiver) more than that of theoretical result when no estimation difference un-der Pb=10-2.展开更多
Various types of interference signals limit the practical application of transform domain communication systems(TDCSs)in the severe electromagnetic field,an orthogonal basis learning method of transformation analysis(...Various types of interference signals limit the practical application of transform domain communication systems(TDCSs)in the severe electromagnetic field,an orthogonal basis learning method of transformation analysis(OBL-TA)is proposed to effectively address the problem of obtaining an optimal transform domain based on sparse representation.Then,the sparse availability is utilized to obtain the optimal transformation analysis by the iterative methods,which yields the sparse representation for transform domain(SRTD)in unrestricted form.In addition,the iterative version of SRTD(I-SRTD)in unrestricted form is obtained by decomposing the SRTD problem into three sub-problems and each sub-problem is iteratively solved by learning the best orthogonal basis.Furthermore,orthogonal basis learning via cost function minimization process is conducted by stochastic descent,which is assured to converge to a local minimum at least.Finally,the optimal transformation analysis is developed by the effectiveness of different transform domains according to the accuracy of the sparse representation and an optimal transformation analysis separately(OPTAS)is applied to the synthesized signal forms with conic alternatives,dualization,and smoothing.Simulation results demonstrate that the superiorities of the proposed methods achieve the optimal recovery and separation more rapidly and accurately than conventional methods.展开更多
针对在实际应用过程中,变换域通信系统的发射端和接收端电磁环境不相同而导致的收发两端出现基函数不一致的情况,对一种新的CASK算法进行了仿真。根据CASK算法和CSK算法以及双极性算法不同干扰、不同噪声和不同收发不一致比例的情况下...针对在实际应用过程中,变换域通信系统的发射端和接收端电磁环境不相同而导致的收发两端出现基函数不一致的情况,对一种新的CASK算法进行了仿真。根据CASK算法和CSK算法以及双极性算法不同干扰、不同噪声和不同收发不一致比例的情况下系统误码率和理论误码率的对比研究,可以发现,虽然在理想情况下,三者差距不大,然而当收发不一致的比例逐渐上升时,CASK算法的传输性能下降较慢,可以进行正常传输,且其传输性能较双极性调制和CSK调制分别提高2 d B和1 d B,具有良好的抗不一致性能,具有良好的应用前景。展开更多
A novel communication receiver which uses lapped transform(LT) incorporating modified median filter(MMF) algorithm was designed for narrow band interference(NBI) excision.Comparing to traditional Fourier Transform,LT ...A novel communication receiver which uses lapped transform(LT) incorporating modified median filter(MMF) algorithm was designed for narrow band interference(NBI) excision.Comparing to traditional Fourier Transform,LT has longer basis vectors,less spectral leakage,thus better frequency resolution.The LT domain MMF algorithm takes full advantages of the direct sequence spread spectrum signal,as well as the characteristics of LT,performs the transform domain filtering twice.The first filtering locates the position of interference and mitigates most of them.The second filtering is performed in a small neighborhood of the located interference.So LT domain MMF algorithm can completely mitigate the interference without distorting the desired signal.The simulation results demonstrate the improved BER(Bit Error Rate)performance and increased robustness of our receiver.展开更多
In order to transmit the speech information safely in the channel,a new speech encryp-tion algorithm in linear canonical transform(LCT)domain based on dynamic modulation of chaot-ic system is proposed.The algorithm fi...In order to transmit the speech information safely in the channel,a new speech encryp-tion algorithm in linear canonical transform(LCT)domain based on dynamic modulation of chaot-ic system is proposed.The algorithm first uses a chaotic system to obtain the number of sampling points of the grouped encrypted signal.Then three chaotic systems are used to modulate the corres-ponding parameters of the LCT,and each group of transform parameters corresponds to a group of encrypted signals.Thus,each group of signals is transformed by LCT with different parameters.Fi-nally,chaotic encryption is performed on the LCT domain spectrum of each group of signals,to realize the overall encryption of the speech signal.The experimental results show that the proposed algorithm is extremely sensitive to the keys and has a larger key space.Compared with the original signal,the waveform and LCT domain spectrum of obtained encrypted signal are distributed more uniformly and have less correlation,which can realize the safe transmission of speech signals.展开更多
针对变换域通信系统传统固定门限判决不能体现频谱的使用程度的问题,提出一种多级门限判决的基函数生成算法。分析了变换域通信系统(transform domain communication system,TDCS)电磁环境频谱的特性和窄带高斯信号的特征,建立了一种二...针对变换域通信系统传统固定门限判决不能体现频谱的使用程度的问题,提出一种多级门限判决的基函数生成算法。分析了变换域通信系统(transform domain communication system,TDCS)电磁环境频谱的特性和窄带高斯信号的特征,建立了一种二元假设检验,在传统二元判决的基础上引入多元判决,能对电磁环境频谱进行多级量化,体现出不同频段的不同使用程度。仿真结果表明,采用多级门限判决的TDCS基函数误码率性能优于传统固定门限判决的TDCS基函数,抗干扰性能更好。展开更多
针对传统变换域通信系统的基函数门限设计单一固定,且未考虑系统吞吐量的缺点,提出了一种新型的双门限基函数优化设计方法。该方法通过高、低门限的合理设定,确立基函数幅度谱与干扰幅度谱的动态关系式。定义变量PCR(probability of bit...针对传统变换域通信系统的基函数门限设计单一固定,且未考虑系统吞吐量的缺点,提出了一种新型的双门限基函数优化设计方法。该方法通过高、低门限的合理设定,确立基函数幅度谱与干扰幅度谱的动态关系式。定义变量PCR(probability of bit error to output capacity ratio)为系统误码率与吞吐量的比值,来综合度量通信系统性能。通过理论分析推导出PCR关于门限的表达式,进而建立优化模型,并采用遍历法进行最终优化搜索。经仿真测试,与传统的二进制门限设计相比,本文所设计双门限优化算法在误码率与系统吞吐量性能上都有较大提升,并能够实现变换域通信系统误码率与吞吐量的最佳权衡。展开更多
基金Supported by Fund of National Key Lab.of Communication.
文摘The method of FRactional Fourier Transform (FRFT) is introduced to Transform Domain Communication System (TDCS) for signal transforming in the paper after theoretical analysis. The method yields optimal Basis Function (BF) by FRFT with optimal transform angle. The TDCS using the proposed method has wider usable spectrum, stronger robustness and better ability of anti non-stationary jamming than using usual methods, such as Fourier Transform (FT), Auto Regressive (AR), Wavelet Transform (WT), etc. The main simulation results are as follows. First, the Bit Error Rate (BER) Pb is close to theoretical bound of no jamming no matter in single tone or in linear chirp interference. Second, the interference-to-signal ratio J /E is at least 12dB more than that of Direct Spread Spectrum System (DSSS) under the same BER if the spectrum hopping-to-signal ratio is 1:20 in chirp plus hopping interfering. Third, the Eb /N 0(when estimation difference is 90% between trans- mitter and receiver) is about 3.5dB or about 0.5dB (when estimation difference is 10% between transmitter and receiver) more than that of theoretical result when no estimation difference un-der Pb=10-2.
基金supported by the University Cooperation Project Foundation of the Key Laboratory for Aerospace Information Technology(KX162600022).
文摘Various types of interference signals limit the practical application of transform domain communication systems(TDCSs)in the severe electromagnetic field,an orthogonal basis learning method of transformation analysis(OBL-TA)is proposed to effectively address the problem of obtaining an optimal transform domain based on sparse representation.Then,the sparse availability is utilized to obtain the optimal transformation analysis by the iterative methods,which yields the sparse representation for transform domain(SRTD)in unrestricted form.In addition,the iterative version of SRTD(I-SRTD)in unrestricted form is obtained by decomposing the SRTD problem into three sub-problems and each sub-problem is iteratively solved by learning the best orthogonal basis.Furthermore,orthogonal basis learning via cost function minimization process is conducted by stochastic descent,which is assured to converge to a local minimum at least.Finally,the optimal transformation analysis is developed by the effectiveness of different transform domains according to the accuracy of the sparse representation and an optimal transformation analysis separately(OPTAS)is applied to the synthesized signal forms with conic alternatives,dualization,and smoothing.Simulation results demonstrate that the superiorities of the proposed methods achieve the optimal recovery and separation more rapidly and accurately than conventional methods.
文摘针对在实际应用过程中,变换域通信系统的发射端和接收端电磁环境不相同而导致的收发两端出现基函数不一致的情况,对一种新的CASK算法进行了仿真。根据CASK算法和CSK算法以及双极性算法不同干扰、不同噪声和不同收发不一致比例的情况下系统误码率和理论误码率的对比研究,可以发现,虽然在理想情况下,三者差距不大,然而当收发不一致的比例逐渐上升时,CASK算法的传输性能下降较慢,可以进行正常传输,且其传输性能较双极性调制和CSK调制分别提高2 d B和1 d B,具有良好的抗不一致性能,具有良好的应用前景。
文摘A novel communication receiver which uses lapped transform(LT) incorporating modified median filter(MMF) algorithm was designed for narrow band interference(NBI) excision.Comparing to traditional Fourier Transform,LT has longer basis vectors,less spectral leakage,thus better frequency resolution.The LT domain MMF algorithm takes full advantages of the direct sequence spread spectrum signal,as well as the characteristics of LT,performs the transform domain filtering twice.The first filtering locates the position of interference and mitigates most of them.The second filtering is performed in a small neighborhood of the located interference.So LT domain MMF algorithm can completely mitigate the interference without distorting the desired signal.The simulation results demonstrate the improved BER(Bit Error Rate)performance and increased robustness of our receiver.
基金supported by the National Natural Science Found-ation of China(No.61901248)the Scientific and Tech-nological Innovation Programs of Higher Education Institu-tions in Shanxi(No.2019L0029).
文摘In order to transmit the speech information safely in the channel,a new speech encryp-tion algorithm in linear canonical transform(LCT)domain based on dynamic modulation of chaot-ic system is proposed.The algorithm first uses a chaotic system to obtain the number of sampling points of the grouped encrypted signal.Then three chaotic systems are used to modulate the corres-ponding parameters of the LCT,and each group of transform parameters corresponds to a group of encrypted signals.Thus,each group of signals is transformed by LCT with different parameters.Fi-nally,chaotic encryption is performed on the LCT domain spectrum of each group of signals,to realize the overall encryption of the speech signal.The experimental results show that the proposed algorithm is extremely sensitive to the keys and has a larger key space.Compared with the original signal,the waveform and LCT domain spectrum of obtained encrypted signal are distributed more uniformly and have less correlation,which can realize the safe transmission of speech signals.
文摘针对变换域通信系统传统固定门限判决不能体现频谱的使用程度的问题,提出一种多级门限判决的基函数生成算法。分析了变换域通信系统(transform domain communication system,TDCS)电磁环境频谱的特性和窄带高斯信号的特征,建立了一种二元假设检验,在传统二元判决的基础上引入多元判决,能对电磁环境频谱进行多级量化,体现出不同频段的不同使用程度。仿真结果表明,采用多级门限判决的TDCS基函数误码率性能优于传统固定门限判决的TDCS基函数,抗干扰性能更好。
文摘针对传统变换域通信系统的基函数门限设计单一固定,且未考虑系统吞吐量的缺点,提出了一种新型的双门限基函数优化设计方法。该方法通过高、低门限的合理设定,确立基函数幅度谱与干扰幅度谱的动态关系式。定义变量PCR(probability of bit error to output capacity ratio)为系统误码率与吞吐量的比值,来综合度量通信系统性能。通过理论分析推导出PCR关于门限的表达式,进而建立优化模型,并采用遍历法进行最终优化搜索。经仿真测试,与传统的二进制门限设计相比,本文所设计双门限优化算法在误码率与系统吞吐量性能上都有较大提升,并能够实现变换域通信系统误码率与吞吐量的最佳权衡。
