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2006 Vol. 28, No. 6
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2006, 28(6): 961-964.
Abstract:
The Ground Moving Target Indication(GMTI) is investigated based on along track high resolution airborne InSAR with two antennas. The two antenna interferometric processing is used to suppress ground clutter. The concept of moving target imaging is introduced for GMTI of high resolution InSAR with longer synthetic aperture time. The range migration correction and refocus processing for moving target signals are implemented to improve the signal-noise rate and signal-clutter rate for their detection and velocity measurement. The processing results of simulated InSAR data show the effectiveness of the new method.
The Ground Moving Target Indication(GMTI) is investigated based on along track high resolution airborne InSAR with two antennas. The two antenna interferometric processing is used to suppress ground clutter. The concept of moving target imaging is introduced for GMTI of high resolution InSAR with longer synthetic aperture time. The range migration correction and refocus processing for moving target signals are implemented to improve the signal-noise rate and signal-clutter rate for their detection and velocity measurement. The processing results of simulated InSAR data show the effectiveness of the new method.
2006, 28(6): 965-968.
Abstract:
CurviLinear Synthetic Aperture Radar (CLSAR), whose aperture is formed via single curvilinear trajectory, has the capability of three-dimensional (3-D) imaging. The 3-D images obtained by using non-parametric methods, however, have little practical use because the data collected by CLSAR is sparse in 3-D frequency space. Valuable 3-D target images are obtained by parametric methods. In this paper, a new algorithm is proposed for imaging 3-D target in CLSAR. With smartly utilizing the loose coupling between the range and cross-range parameters, the new algorithm reduces the problem of high dimensional optimization into several lower dimensional optimization, estimates them in sequence, and refines them via iteration. Simulation results show the new algorithm can efficiently form the targets 3-D image via CLSAR.
CurviLinear Synthetic Aperture Radar (CLSAR), whose aperture is formed via single curvilinear trajectory, has the capability of three-dimensional (3-D) imaging. The 3-D images obtained by using non-parametric methods, however, have little practical use because the data collected by CLSAR is sparse in 3-D frequency space. Valuable 3-D target images are obtained by parametric methods. In this paper, a new algorithm is proposed for imaging 3-D target in CLSAR. With smartly utilizing the loose coupling between the range and cross-range parameters, the new algorithm reduces the problem of high dimensional optimization into several lower dimensional optimization, estimates them in sequence, and refines them via iteration. Simulation results show the new algorithm can efficiently form the targets 3-D image via CLSAR.
2006, 28(6): 969-972.
Abstract:
The use of a monostatic radar configuration limits the ability of an Inverse Synthetic Aperture Radar (ISAR) system to image targets moving along the radar Line Of Sight (LOS). By employing bistatic geometries this limitation may be overcome. This paper analyzes the echo model of bistatic ISAR. The imaging theory, azimuth resolution, target size limitation and sampling rate of bistatic ISAR are studied in detail, and the analytical solutions are obtained. The computer simulation images are presented.
The use of a monostatic radar configuration limits the ability of an Inverse Synthetic Aperture Radar (ISAR) system to image targets moving along the radar Line Of Sight (LOS). By employing bistatic geometries this limitation may be overcome. This paper analyzes the echo model of bistatic ISAR. The imaging theory, azimuth resolution, target size limitation and sampling rate of bistatic ISAR are studied in detail, and the analytical solutions are obtained. The computer simulation images are presented.
2006, 28(6): 973-976.
Abstract:
UWB SAR works usually in low Signal-to-Clutter Ratio (SCR) conditions in order to detect targets hidden in forest or buried in ground. A Time-Frequency Representation Image Formation (TFRIF) is proposed in this paper, which can get a series of SAR images of different spatial frequency without loss of resolution. The SCR is improved through fusion of those images. The efficiency of TFRIF is proved with real data.
UWB SAR works usually in low Signal-to-Clutter Ratio (SCR) conditions in order to detect targets hidden in forest or buried in ground. A Time-Frequency Representation Image Formation (TFRIF) is proposed in this paper, which can get a series of SAR images of different spatial frequency without loss of resolution. The SCR is improved through fusion of those images. The efficiency of TFRIF is proved with real data.
2006, 28(6): 977-981.
Abstract:
The echo model of airborne bistatic SAR is analyzed in this paper. Based on the echo model and the chirp scaling algorithm of monostatic SAR imaging, the chirp scaling algorithm of bistatic SAR imaging is deduced, and its error is analyzed subsequently. Finally, it is proved to be correct by the simulation results.
The echo model of airborne bistatic SAR is analyzed in this paper. Based on the echo model and the chirp scaling algorithm of monostatic SAR imaging, the chirp scaling algorithm of bistatic SAR imaging is deduced, and its error is analyzed subsequently. Finally, it is proved to be correct by the simulation results.
2006, 28(6): 982-984.
Abstract:
The ISAR imaging of ship is significant relative to plane. The imaging condition of ship is more complicated than plane due to the complexity of the ships movement, and the conventional ISAR imaging algorithm to the plane can not be satisfactory to the ship. So, a new method based on adaptive Chirplet decomposition is proposed here, the instantaneous ISAR ship image is obtained.
The ISAR imaging of ship is significant relative to plane. The imaging condition of ship is more complicated than plane due to the complexity of the ships movement, and the conventional ISAR imaging algorithm to the plane can not be satisfactory to the ship. So, a new method based on adaptive Chirplet decomposition is proposed here, the instantaneous ISAR ship image is obtained.
2006, 28(6): 985-988.
Abstract:
Focused the issues on Moving Target Detection (MTD) in spotlight mode Synthetic Aperture Radar (SAR),the echo is divided into groups that are continuous and partly overlapping in time domain. Every group of data can be regarded as coming from a sub-aperture of time domain. The images of same ground scene are then generated in multiple sub-apertures. By Subtracting two consecutive sub-aperture SAR images, the stationary clutter or targets that appear in a sub-aperture SAR image can be suppressed or substantially eliminated, but moving target image is left. Superposing the result of subtracting every two consecutive sub-aperture SAR images, the tract of this moving target is obtained. Furthermore, its moving parameters can be estimated. This paper proved this method in theory and the simulation result testifies its validity.
Focused the issues on Moving Target Detection (MTD) in spotlight mode Synthetic Aperture Radar (SAR),the echo is divided into groups that are continuous and partly overlapping in time domain. Every group of data can be regarded as coming from a sub-aperture of time domain. The images of same ground scene are then generated in multiple sub-apertures. By Subtracting two consecutive sub-aperture SAR images, the stationary clutter or targets that appear in a sub-aperture SAR image can be suppressed or substantially eliminated, but moving target image is left. Superposing the result of subtracting every two consecutive sub-aperture SAR images, the tract of this moving target is obtained. Furthermore, its moving parameters can be estimated. This paper proved this method in theory and the simulation result testifies its validity.
2006, 28(6): 989-993.
Abstract:
This paper is about Monopulse Secondary Surveillance Redar (MSSR) reply decoding and confidence bits. A novel real-time arithmetic is presented in this paper which uses new rule of garble and overlap to process defruit and to extract reply code. The experimental results show that the new arithmetic can overcome the problem of multi-target reply-blend and get better reply decoding and confidence bits on the highly density reply occasion.
This paper is about Monopulse Secondary Surveillance Redar (MSSR) reply decoding and confidence bits. A novel real-time arithmetic is presented in this paper which uses new rule of garble and overlap to process defruit and to extract reply code. The experimental results show that the new arithmetic can overcome the problem of multi-target reply-blend and get better reply decoding and confidence bits on the highly density reply occasion.
2006, 28(6): 994-998.
Abstract:
Change detection is the process of identifying differences in the state of an object or phenomenon by observing it at different times. by removing the correlation among multitemporal images, change information can be detected effectively. Independence Component Analysis (ICA) is a blind source separate technique appeared in recent years. It can reduce second and high-order dependences in observed data, and the independent components are statistically as independent as possible. In this paper, a multitemporal remote sensing images change detection approach based on ICA is proposed in this paper. Firstly, independence component images change are obtained based on the ICA transformation without any prior knowledge about change areas. Then, different kinds of land variation are located according to these independent source images. The experimental results in synthesize and real multitemporal images show the effectiveness of the proposed approach.
Change detection is the process of identifying differences in the state of an object or phenomenon by observing it at different times. by removing the correlation among multitemporal images, change information can be detected effectively. Independence Component Analysis (ICA) is a blind source separate technique appeared in recent years. It can reduce second and high-order dependences in observed data, and the independent components are statistically as independent as possible. In this paper, a multitemporal remote sensing images change detection approach based on ICA is proposed in this paper. Firstly, independence component images change are obtained based on the ICA transformation without any prior knowledge about change areas. Then, different kinds of land variation are located according to these independent source images. The experimental results in synthesize and real multitemporal images show the effectiveness of the proposed approach.
2006, 28(6): 999-1003.
Abstract:
In this paper, a measure of signal variability is defined. Given any set of statistically independent source signals, it is proved here that a linear mixture of those signals has the following property: the signal variability of any signal mixture is greater than (or equal to) minimal that of its component source signals, and is less than (or equal to) maximal that of its component source signals. Based on the property, an algorithm for linear blind signal extraction is proposed. In the proposed algorithm, the source signal is extracted one by one by using generalized eigenvalue theory and deflation approach. The presented algorithm has less computations. Simulation results illustrate the efficiency and the good performance of the algorithm.
In this paper, a measure of signal variability is defined. Given any set of statistically independent source signals, it is proved here that a linear mixture of those signals has the following property: the signal variability of any signal mixture is greater than (or equal to) minimal that of its component source signals, and is less than (or equal to) maximal that of its component source signals. Based on the property, an algorithm for linear blind signal extraction is proposed. In the proposed algorithm, the source signal is extracted one by one by using generalized eigenvalue theory and deflation approach. The presented algorithm has less computations. Simulation results illustrate the efficiency and the good performance of the algorithm.
2006, 28(6): 1004-1008.
Abstract:
The bearing and range estimation of near-field sources is studied and a new method is presented. The presented algorithm uses the dual-polarization array and second statistics to estimate DOA -range parameter of near-field sources. The method has the merits of good estimate precision and no needing spectral peak searching. Its effectiveness is approved by the simulation results.
The bearing and range estimation of near-field sources is studied and a new method is presented. The presented algorithm uses the dual-polarization array and second statistics to estimate DOA -range parameter of near-field sources. The method has the merits of good estimate precision and no needing spectral peak searching. Its effectiveness is approved by the simulation results.
2006, 28(6): 1009-1012.
Abstract:
A blind equalization algorithm based on constant modulus and sparse underwater acoustic channel is presented according to the sparse characteristic of the high rate underwater acoustic communications. The algorithm combines the improved constant modulus algorithm with a variation of the decision feedback equalizer, namely the partial feedback equalizer, and uses the sparse characteristic of the underwater acoustic channel. It can not only achieve better equalization of the sparse underwater acoustic channel , but also calculate effectively and use easily hardware to carry out the algorithm . Simulation tests are dynamically conducted using the typical sparse underwater acoustic channel model. Simulation results show that the proposed algorithm has the advantages of robustness, calculation-efficient, lower steady state mean squared error, as compared to the self-adaptive LMS algorithm based sparse iteration.
A blind equalization algorithm based on constant modulus and sparse underwater acoustic channel is presented according to the sparse characteristic of the high rate underwater acoustic communications. The algorithm combines the improved constant modulus algorithm with a variation of the decision feedback equalizer, namely the partial feedback equalizer, and uses the sparse characteristic of the underwater acoustic channel. It can not only achieve better equalization of the sparse underwater acoustic channel , but also calculate effectively and use easily hardware to carry out the algorithm . Simulation tests are dynamically conducted using the typical sparse underwater acoustic channel model. Simulation results show that the proposed algorithm has the advantages of robustness, calculation-efficient, lower steady state mean squared error, as compared to the self-adaptive LMS algorithm based sparse iteration.
2006, 28(6): 1013-1015.
Abstract:
During the transmission of digital image, the signal may be blurred by the Point Spread Function (PSF) of the 2-dimensional channel. On the restoration of the image, the influence of PSF should be eliminated without the knowledge of PSF in most real applications. It is called blind image restoration when the property of PSF is unknown. A new algorithm for blind image restoration via 2-dimensional blind equalization is proposed in this article. It is essentially a 2-dimensional expansion of EVA algorithm applied in the field of communication. Experimental results show that the algorithm works with rapid convergence speed and high improvement of SNR and has the prospect of wide applications.
During the transmission of digital image, the signal may be blurred by the Point Spread Function (PSF) of the 2-dimensional channel. On the restoration of the image, the influence of PSF should be eliminated without the knowledge of PSF in most real applications. It is called blind image restoration when the property of PSF is unknown. A new algorithm for blind image restoration via 2-dimensional blind equalization is proposed in this article. It is essentially a 2-dimensional expansion of EVA algorithm applied in the field of communication. Experimental results show that the algorithm works with rapid convergence speed and high improvement of SNR and has the prospect of wide applications.
2006, 28(6): 1016-1020.
Abstract:
This paper presents an MP-based harmonic and individual lines sinusoidal modeling used in parametric audio coding. The input audio signal can be represented by harmonic plus individual lines and the model parameters (amplitudes, frequencies and phases) are extracted by MP (Matching Pursuit) algorithm which can lower computational complexity. The fundamental frequency is obtained by subharmonic summation. Harmonic frequency points are decided by MP exactly and are curve-fitted by quadric polynomial. The corresponding harmonic amplitudes are simulated by LPC spectrum envelope. In the decoder, audio signal is reconstructed with IFFT and OLA. The experimental results show that this sinusoidal modeling can represent the stationary parts of the audio signal very well.
This paper presents an MP-based harmonic and individual lines sinusoidal modeling used in parametric audio coding. The input audio signal can be represented by harmonic plus individual lines and the model parameters (amplitudes, frequencies and phases) are extracted by MP (Matching Pursuit) algorithm which can lower computational complexity. The fundamental frequency is obtained by subharmonic summation. Harmonic frequency points are decided by MP exactly and are curve-fitted by quadric polynomial. The corresponding harmonic amplitudes are simulated by LPC spectrum envelope. In the decoder, audio signal is reconstructed with IFFT and OLA. The experimental results show that this sinusoidal modeling can represent the stationary parts of the audio signal very well.
2006, 28(6): 1021-1025.
Abstract:
On the basis of cyclostationary feature of speech in short segment, an improved Voice Activity Detection (VAD) algorithm based on higher-order cyclic cumulant is proposed in this paper, which can be applied in complex noise background. In this algorithm, modeling speech signal under MA(Moving Average)model is adopted and estimating cyclic frequency by AMDF(Average Magnitude Difference Function) is chosen to decrease computing complexity as well. Extensive testing on VoIP platform reveals that the algorithm owns good adaptive classification capability in steady noise, such as Gauss (whited and colored) noise, while with a little loss in speech quality, even when it is applied in asymmetric noise conditions.
On the basis of cyclostationary feature of speech in short segment, an improved Voice Activity Detection (VAD) algorithm based on higher-order cyclic cumulant is proposed in this paper, which can be applied in complex noise background. In this algorithm, modeling speech signal under MA(Moving Average)model is adopted and estimating cyclic frequency by AMDF(Average Magnitude Difference Function) is chosen to decrease computing complexity as well. Extensive testing on VoIP platform reveals that the algorithm owns good adaptive classification capability in steady noise, such as Gauss (whited and colored) noise, while with a little loss in speech quality, even when it is applied in asymmetric noise conditions.
2006, 28(6): 1026-1030.
Abstract:
The typical target recognition and location is a key technique of the application system for Unmanned Aerial Vehicle (UAV), but there exists a certain difficulty in entirely automatic target recognition and location. A new method to recognize and locate multiple targets is presented in this paper. Through introducing the deformable template technique and the man-in-the-loop thought, this paper designs the multiple target recognition and location algorithm for the fused downward-looking image from UAV. The emphases of the method are laid on the construction of different deformable templates, the definition of corresponding energy functions, and the optimal search strategy. Results show that the technique of multiple target recognition and location using deformable templates is more effective and can accurately recognize and locate multiple typical targets.
The typical target recognition and location is a key technique of the application system for Unmanned Aerial Vehicle (UAV), but there exists a certain difficulty in entirely automatic target recognition and location. A new method to recognize and locate multiple targets is presented in this paper. Through introducing the deformable template technique and the man-in-the-loop thought, this paper designs the multiple target recognition and location algorithm for the fused downward-looking image from UAV. The emphases of the method are laid on the construction of different deformable templates, the definition of corresponding energy functions, and the optimal search strategy. Results show that the technique of multiple target recognition and location using deformable templates is more effective and can accurately recognize and locate multiple typical targets.
2006, 28(6): 1031-1035.
Abstract:
A new group of texture features based on Generalized Local Walsh Transform (GLWT) are presented in this paper. Firstly, Local Walsh Transform (LWT) is defined and generalized in spatial domain to extract local texture information. Then, the twelve 2nd order moments of GLWT coefficients are estimated in a macro-window and selected as texture features. The performance of these features in discriminating textures has been evaluated. The textural features from Haralick(1973), Wang Li(1990), Yu Hui has been used for comparison. The experimental results reveal that the texture features presented have the best discriminating performance.
A new group of texture features based on Generalized Local Walsh Transform (GLWT) are presented in this paper. Firstly, Local Walsh Transform (LWT) is defined and generalized in spatial domain to extract local texture information. Then, the twelve 2nd order moments of GLWT coefficients are estimated in a macro-window and selected as texture features. The performance of these features in discriminating textures has been evaluated. The textural features from Haralick(1973), Wang Li(1990), Yu Hui has been used for comparison. The experimental results reveal that the texture features presented have the best discriminating performance.
2006, 28(6): 1036-1039.
Abstract:
The approach for speaker recognition based on neural networks is able to emulate the function of human brain in some degree, so it is a main implementation technology in the speaker recognition. But it is difficult to determine the number of hidden layer neurons, slowly convergent and easy to fall into local minimum point. The model of wavelet neural networks is studied. The structure of the network and learning algorithm are given. The recognition correctness reaches to 99.5% for 5 speakers using Mel frequency cepstral coefficient as feature parameters. The experimental at results show that the learning rate and recognition correctness are improved much compared to the BP networks. It has a good application prospect and worth to research further more.
The approach for speaker recognition based on neural networks is able to emulate the function of human brain in some degree, so it is a main implementation technology in the speaker recognition. But it is difficult to determine the number of hidden layer neurons, slowly convergent and easy to fall into local minimum point. The model of wavelet neural networks is studied. The structure of the network and learning algorithm are given. The recognition correctness reaches to 99.5% for 5 speakers using Mel frequency cepstral coefficient as feature parameters. The experimental at results show that the learning rate and recognition correctness are improved much compared to the BP networks. It has a good application prospect and worth to research further more.
2006, 28(6): 1040-1044.
Abstract:
The effects of several types of oppressive broadband interference (BPSK interference, FM interference) on pseudo noise coded fuze system are analyzed. It is found that the correlation output is deteriorated when the interference power is larger than the anti-interference limit of the fuze system. So it is very necessary to excise the above interference before correlation. A new simple technique of excising interference through envelope filtering is put forward. The received signal is quadrature demodulated to inphase and quadphase signal. The instantaneous envelope and phase are got with the inphase and quadphase signal. The envelope of interference is obtained by envelope notch filtering in the frequency domain. The interference is reconstructed using the notched envelope sequence and the phase sequence. Then the reconstructed interference is subtracted from the received signal. It is found by simulation that the technique proposed in this paper can effectively excise the broadband interference, especially for strong interference. And the correlation output is improved obviously. The technique is easy to be understood. It has low computational complexity and therefore is easy to realize.
The effects of several types of oppressive broadband interference (BPSK interference, FM interference) on pseudo noise coded fuze system are analyzed. It is found that the correlation output is deteriorated when the interference power is larger than the anti-interference limit of the fuze system. So it is very necessary to excise the above interference before correlation. A new simple technique of excising interference through envelope filtering is put forward. The received signal is quadrature demodulated to inphase and quadphase signal. The instantaneous envelope and phase are got with the inphase and quadphase signal. The envelope of interference is obtained by envelope notch filtering in the frequency domain. The interference is reconstructed using the notched envelope sequence and the phase sequence. Then the reconstructed interference is subtracted from the received signal. It is found by simulation that the technique proposed in this paper can effectively excise the broadband interference, especially for strong interference. And the correlation output is improved obviously. The technique is easy to be understood. It has low computational complexity and therefore is easy to realize.
2006, 28(6): 1045-1048.
Abstract:
A time-frequency analysis method for reconnaissance signal recognition of PN and LFM is studied. Wigner time-frequency distribution function for PRBC-LFM reconnaissance signal is deduced. By WVD analysis，features related to carrier frequency, FM slope and PN parameters such as sub-pulse width, code-length and pulse cycle are extracted. Then a method for the parameter evaluation is presented. Finally, analysis results are simulated under Gaussian noise conditions. Simulation show the method is superior to spectral correlation method on PRBC-LFM signal recognition and not limited to relations between bandwidth of FM and spectral width of PN.
A time-frequency analysis method for reconnaissance signal recognition of PN and LFM is studied. Wigner time-frequency distribution function for PRBC-LFM reconnaissance signal is deduced. By WVD analysis，features related to carrier frequency, FM slope and PN parameters such as sub-pulse width, code-length and pulse cycle are extracted. Then a method for the parameter evaluation is presented. Finally, analysis results are simulated under Gaussian noise conditions. Simulation show the method is superior to spectral correlation method on PRBC-LFM signal recognition and not limited to relations between bandwidth of FM and spectral width of PN.
2006, 28(6): 1049-1053.
Abstract:
A new robust joint source channel coding method for MPEG-4 video over noisy channel is proposed. In the method, the base layer bit streams are reordered according to their relative importance and then interlaced packetized. Multiple sub-layers of texture information are generated based on their rate distortion function, the number of which is adjusted dynamically by the encoder according to the feedback information to minimize the overall distortion. Simulation results show that the method has the performance obviously higher than that of un-protected MPEG-4, and can be more stable than MPEG-4 equal error protection method under the same conditions of bandwidth and packet loss rate. Since the method makes joint optimization to the the number of transmission sublayers and the protection level according to the feedback parameter, it can be more adaptive to the channel situation and can obtain higher performance compared with MDFEC method proposed by Puri, which design the object functions and perfoms optimization according to the fixed channel situation.
A new robust joint source channel coding method for MPEG-4 video over noisy channel is proposed. In the method, the base layer bit streams are reordered according to their relative importance and then interlaced packetized. Multiple sub-layers of texture information are generated based on their rate distortion function, the number of which is adjusted dynamically by the encoder according to the feedback information to minimize the overall distortion. Simulation results show that the method has the performance obviously higher than that of un-protected MPEG-4, and can be more stable than MPEG-4 equal error protection method under the same conditions of bandwidth and packet loss rate. Since the method makes joint optimization to the the number of transmission sublayers and the protection level according to the feedback parameter, it can be more adaptive to the channel situation and can obtain higher performance compared with MDFEC method proposed by Puri, which design the object functions and perfoms optimization according to the fixed channel situation.
2006, 28(6): 1054-1058.
Abstract:
SNRE (Signal-to-Noise Ration Estimator) can be used in a lot of areas in mobile communication, such as the decoder of LDPC code which need it to compute the a priori information of received bits. In this paper, a low complexity blind SNRE, FBSNRE (Fading channel Blind SNRE), based on the online estimator in AWGN channel, is presented. Simulation results prove that FBSNRE cam achieve excellent performance when it is applied in the decoder of LDPC code.
SNRE (Signal-to-Noise Ration Estimator) can be used in a lot of areas in mobile communication, such as the decoder of LDPC code which need it to compute the a priori information of received bits. In this paper, a low complexity blind SNRE, FBSNRE (Fading channel Blind SNRE), based on the online estimator in AWGN channel, is presented. Simulation results prove that FBSNRE cam achieve excellent performance when it is applied in the decoder of LDPC code.
2006, 28(6): 1059-1063.
Abstract:
The high latency introduced by the recursive computation in the MAP-based decoding of turbo codes limits the application of turbo codes in the high data rate transmission。In this paper, a parallel decoding scheme for reducing the decoding delay greatly is presented. In this parallel decoding scheme, interleaver (de-interleaver) must be collision-free when the extrinsic information memory is reading(or writing) between the two decoders. An idea of designing an arbitrary S-random interleaver using the collision-free mapping law is presented. Simulation results show that the BER performance of parallel decoding scheme is inferior slightly to that of the conventional scheme.
The high latency introduced by the recursive computation in the MAP-based decoding of turbo codes limits the application of turbo codes in the high data rate transmission。In this paper, a parallel decoding scheme for reducing the decoding delay greatly is presented. In this parallel decoding scheme, interleaver (de-interleaver) must be collision-free when the extrinsic information memory is reading(or writing) between the two decoders. An idea of designing an arbitrary S-random interleaver using the collision-free mapping law is presented. Simulation results show that the BER performance of parallel decoding scheme is inferior slightly to that of the conventional scheme.
2006, 28(6): 1064-1067.
Abstract:
By employing MMSE (Minimal Mean Squared Error) criteria, the multi-user transceivers in this paper are optimized by adjusting their signatures and demodulations according to interferences around, which can reduce at most the co-interferences from users and minimize the lower bound of MMSE. During the design process, the striking improvements in both convergence and low-complexity are achieved by using matrix-blocking computation theory. And in practice, the designed signature assemble perform rather well than that by capacity-maximizing signature design method (Rose etc.2002) under the additive white Gaussian noise channel. Finally, some simulation results are also provided as proof.
By employing MMSE (Minimal Mean Squared Error) criteria, the multi-user transceivers in this paper are optimized by adjusting their signatures and demodulations according to interferences around, which can reduce at most the co-interferences from users and minimize the lower bound of MMSE. During the design process, the striking improvements in both convergence and low-complexity are achieved by using matrix-blocking computation theory. And in practice, the designed signature assemble perform rather well than that by capacity-maximizing signature design method (Rose etc.2002) under the additive white Gaussian noise channel. Finally, some simulation results are also provided as proof.
2006, 28(6): 1068-1072.
Abstract:
In a heavy noise,the method based on Wigner Ville (WV) and Hough transformations has the poor performance of detecting the weak signal. To improve it, this paper analyzes the influence of the Fitz Hugh Nagumo(FHN) models parameters on its filtering characteristics, and presents a method of detecting weak sinusoid and LFM signals based on FHN model of stochastic resonance. Firstly ,the received signal is filtered by FHN model ,and transformed by WV and Hough in turns, thus whether a signal is present in noise is determined according to whether there is a line in time-frequency picture. Finally, the validity of this method is well verified by the experiments.
In a heavy noise,the method based on Wigner Ville (WV) and Hough transformations has the poor performance of detecting the weak signal. To improve it, this paper analyzes the influence of the Fitz Hugh Nagumo(FHN) models parameters on its filtering characteristics, and presents a method of detecting weak sinusoid and LFM signals based on FHN model of stochastic resonance. Firstly ,the received signal is filtered by FHN model ,and transformed by WV and Hough in turns, thus whether a signal is present in noise is determined according to whether there is a line in time-frequency picture. Finally, the validity of this method is well verified by the experiments.
2006, 28(6): 1073-1076.
Abstract:
Ultra-WideBand (UWB) signal faced badly multi-path fading in indoor environment, RAKE receiver usually is adopted to gather multi-path energy and improve performance. A new diversity scheme is proposed in this paper, which implemented pretreatment in transmitter and RAKE combine in receiver respectively, and then a based on channel matrix eigen-value SVD algorithm is presented to estimated optimal parameter of delay time and combine weight. Both theoretic analysis and simulation show, the algorithm always gains maximized output SNR than conventional RAKE receiver.
Ultra-WideBand (UWB) signal faced badly multi-path fading in indoor environment, RAKE receiver usually is adopted to gather multi-path energy and improve performance. A new diversity scheme is proposed in this paper, which implemented pretreatment in transmitter and RAKE combine in receiver respectively, and then a based on channel matrix eigen-value SVD algorithm is presented to estimated optimal parameter of delay time and combine weight. Both theoretic analysis and simulation show, the algorithm always gains maximized output SNR than conventional RAKE receiver.
2006, 28(6): 1077-1081.
Abstract:
It is a great challenge in UWB communication systems to receive the subnanosecond pulses properly. Most literatures analyzed the performance of UWB systems based on match filter receiver. But the system performance will degrade greatly when there is big timing error. And the match filter receiver can hardly provide several correlation templates with different timings. In this paper, a novel method to receive the subnanosecond pulses is proposed. This method is tolerant against timing error, and can provide correlation templates with different timings. In addition, the performance degradation of this receiver is acceptable.
It is a great challenge in UWB communication systems to receive the subnanosecond pulses properly. Most literatures analyzed the performance of UWB systems based on match filter receiver. But the system performance will degrade greatly when there is big timing error. And the match filter receiver can hardly provide several correlation templates with different timings. In this paper, a novel method to receive the subnanosecond pulses is proposed. This method is tolerant against timing error, and can provide correlation templates with different timings. In addition, the performance degradation of this receiver is acceptable.
2006, 28(6): 1082-1085.
Abstract:
A T/2 fractionally-spaced sparse complete feedback equalizer scheme is proposed to avoid the performance deterioration caused by symbol timing error in the receiver, which is a generalized version of the previously proposed Complete Feedback Equalizer (CFE). The performance of the scheme is analyzed based on minimum mean square error (MMSE) criterion, and the MMSE performance is proved to be the same as that of the Decision Feedback Equalizer (DFE). The scheme also effectively exploits the sparseness of the multi-path channels with large delay spread and reduces the complexity of the equalizer with small performance degradation. Theoretical analysis and computer simulations over field measured wireless channel show that the scheme performs better than symbol-spaced CFE and T/2 fractionally-spaced DFE.
A T/2 fractionally-spaced sparse complete feedback equalizer scheme is proposed to avoid the performance deterioration caused by symbol timing error in the receiver, which is a generalized version of the previously proposed Complete Feedback Equalizer (CFE). The performance of the scheme is analyzed based on minimum mean square error (MMSE) criterion, and the MMSE performance is proved to be the same as that of the Decision Feedback Equalizer (DFE). The scheme also effectively exploits the sparseness of the multi-path channels with large delay spread and reduces the complexity of the equalizer with small performance degradation. Theoretical analysis and computer simulations over field measured wireless channel show that the scheme performs better than symbol-spaced CFE and T/2 fractionally-spaced DFE.
2006, 28(6): 1086-1090.
Abstract:
Dynamic network topology, long transport delay and interferences from outer space make the intersatellite communications unstable. In this paper, a link stability model of satellite networks is presented. Based on this model, an intersatellite link design strategy is introduced for a LEO/MEO satellite network. The simulation results show that the link stability model is applicable to different performance requirements of satellite networks.
Dynamic network topology, long transport delay and interferences from outer space make the intersatellite communications unstable. In this paper, a link stability model of satellite networks is presented. Based on this model, an intersatellite link design strategy is introduced for a LEO/MEO satellite network. The simulation results show that the link stability model is applicable to different performance requirements of satellite networks.
2006, 28(6): 1091-1094.
Abstract:
Background and advantages of GPS based remote sensing are introduced, characteristics of forward scattered GPS signal such as polarization, variation, code delay due to the wave travel distance difference between direct and scattered signal, and the cross-correlation power expansion due to sea surface roughness are discussed in detail. Working principle of the self-developed delay mapping receiver is also presented. The first test flight experiment is done at Tianjin near sea with the delay mapping receiver mounted on an airplane. Analysis shows that results have good agreement to the theory discussed above.
Background and advantages of GPS based remote sensing are introduced, characteristics of forward scattered GPS signal such as polarization, variation, code delay due to the wave travel distance difference between direct and scattered signal, and the cross-correlation power expansion due to sea surface roughness are discussed in detail. Working principle of the self-developed delay mapping receiver is also presented. The first test flight experiment is done at Tianjin near sea with the delay mapping receiver mounted on an airplane. Analysis shows that results have good agreement to the theory discussed above.
2006, 28(6): 1095-1100.
Abstract:
Transmitter diversity has been studied extensively as a technique for combating channel fading in mobile wireless communications, especially when receiver diversity is expensive or impractical. In this paper, three subspace-tracking channel estimation algorithms for OFDM systems with transmitter diversity are proposed, and their performances are compared. Because the fading channel has slow-varying delays and fast-varying amplitudes, the noise effect in the channel estimation can be partially eliminated by tracking delay subspace and amplitudes of the channel. In three approaches, the last one has the lowest computation complexity and the best performance, the first one has a little high complexity and the worst performance, and the second one has the highest complexity for its DFT and IDFT operations. Simulation results show that one to two decibels benefits can be obtained by subspace and amplitudes tracking.
Transmitter diversity has been studied extensively as a technique for combating channel fading in mobile wireless communications, especially when receiver diversity is expensive or impractical. In this paper, three subspace-tracking channel estimation algorithms for OFDM systems with transmitter diversity are proposed, and their performances are compared. Because the fading channel has slow-varying delays and fast-varying amplitudes, the noise effect in the channel estimation can be partially eliminated by tracking delay subspace and amplitudes of the channel. In three approaches, the last one has the lowest computation complexity and the best performance, the first one has a little high complexity and the worst performance, and the second one has the highest complexity for its DFT and IDFT operations. Simulation results show that one to two decibels benefits can be obtained by subspace and amplitudes tracking.
2006, 28(6): 1101-1105.
Abstract:
The blind space-time channel estimation and multiuser detection algorithm for asynchronous DS-CDMA system in frequency selective Rayleigh fading channel are presented. By investigating the code space of the multipath signals and the data vector space, the noise-subspace-based approach is used to perform blind channel parameter estimation in the asynchronous DS-CDMA system. The method exploits not only the characteristics of multipath propagation but also the characteristics of timing-offsets which may occur in the receiver, to facilitate the application of a blind linear filter-optimization technique to robust interference suppression. A modified ULV updating algorithm is applied to performing noise subspace tracking. The algorithm does not require rank estimation of the correlation matrix, and estimate directly the noise subspace without tracking the signal subspace. Furthermore, Linearly Constrained Minimum Variance (LCMV) blind space-time multiuser detection and its adaptive implementation based on Householder-transform constrained least-mean-square (HCLMS) algorithm is considered. Simulation results show the effectiveness of the proposed algorithms.
The blind space-time channel estimation and multiuser detection algorithm for asynchronous DS-CDMA system in frequency selective Rayleigh fading channel are presented. By investigating the code space of the multipath signals and the data vector space, the noise-subspace-based approach is used to perform blind channel parameter estimation in the asynchronous DS-CDMA system. The method exploits not only the characteristics of multipath propagation but also the characteristics of timing-offsets which may occur in the receiver, to facilitate the application of a blind linear filter-optimization technique to robust interference suppression. A modified ULV updating algorithm is applied to performing noise subspace tracking. The algorithm does not require rank estimation of the correlation matrix, and estimate directly the noise subspace without tracking the signal subspace. Furthermore, Linearly Constrained Minimum Variance (LCMV) blind space-time multiuser detection and its adaptive implementation based on Householder-transform constrained least-mean-square (HCLMS) algorithm is considered. Simulation results show the effectiveness of the proposed algorithms.
2006, 28(6): 1106-1110.
Abstract:
A new chaotic spread spectrum communication system FFH-FMDCSK is presented, which is based on FMDCSK and fast frequency hopping techniques. FFH-FMDCSK is able to improve the performance of FMDCSK on anti-jam, multiple access, and resistance to multipath fading as well as low interference to other systems. This paper compares the BER performance of FFH-FMDCSK with that of FMDCSK in multi-path channel, and delivers the theoretical analysis and Monte-Carlo simulation results.
A new chaotic spread spectrum communication system FFH-FMDCSK is presented, which is based on FMDCSK and fast frequency hopping techniques. FFH-FMDCSK is able to improve the performance of FMDCSK on anti-jam, multiple access, and resistance to multipath fading as well as low interference to other systems. This paper compares the BER performance of FFH-FMDCSK with that of FMDCSK in multi-path channel, and delivers the theoretical analysis and Monte-Carlo simulation results.
2006, 28(6): 1111-1114.
Abstract:
In this paper, a new PAM (QAM) constellation is recursively designed by lower order modulation constellation arrangement, and the constellation is still Gray map. The every higher order modulation bit soft output can be calculated by bit soft output of lower order modulation. The soft output of any higher order modulation can be calculated by calculating the soft output of binary modulation. It can decrease complexity. The simulation shows its correctness.
In this paper, a new PAM (QAM) constellation is recursively designed by lower order modulation constellation arrangement, and the constellation is still Gray map. The every higher order modulation bit soft output can be calculated by bit soft output of lower order modulation. The soft output of any higher order modulation can be calculated by calculating the soft output of binary modulation. It can decrease complexity. The simulation shows its correctness.
2006, 28(6): 1115-1119.
Abstract:
A new video rate control scheme which uses linear source model as content complexity measure of video frames is proposed in this paper to implement bit allocation between frames and rate control over Micro Btocte(MB) level in one frame. Comparing with TM5, simulation results show that the proposed method can improve PSNR obviously and achieve more accurate rate control as well as more smooth objective and subjective visual quality even when scenes change. This algorithm is also applicable in MPEG4 and low rate video coding.
A new video rate control scheme which uses linear source model as content complexity measure of video frames is proposed in this paper to implement bit allocation between frames and rate control over Micro Btocte(MB) level in one frame. Comparing with TM5, simulation results show that the proposed method can improve PSNR obviously and achieve more accurate rate control as well as more smooth objective and subjective visual quality even when scenes change. This algorithm is also applicable in MPEG4 and low rate video coding.
2006, 28(6): 1120-1123.
Abstract:
In this paper a new MultiFractal Model (MFM) of Variable Bit Rate (VBR) video traffic is proposed. It makes sure that the approaching performance of the new model (PM-MFM) has better performance than MFM and PM-MFM. Meanwhile, a new frame level VBR traffic model base on PM-MFM is proposed, which is called Composite MWM(CMWM).CMWM considers the correlation structure of I, P, B frame size of VBR video traffic. Simulation result shows that CMCM can depict statistical feature and network performance more accurately than traditional SRD model and LRD model, Simulation result also shows multifractal feature is important in traffic modeling.
In this paper a new MultiFractal Model (MFM) of Variable Bit Rate (VBR) video traffic is proposed. It makes sure that the approaching performance of the new model (PM-MFM) has better performance than MFM and PM-MFM. Meanwhile, a new frame level VBR traffic model base on PM-MFM is proposed, which is called Composite MWM(CMWM).CMWM considers the correlation structure of I, P, B frame size of VBR video traffic. Simulation result shows that CMCM can depict statistical feature and network performance more accurately than traditional SRD model and LRD model, Simulation result also shows multifractal feature is important in traffic modeling.
2006, 28(6): 1124-1128.
Abstract:
There have been two a priori models up till now concerning network traffic: self-similar and multifractal models. The self-similar model is simple enough to characterize network traffic with the single exponent H, however it can not thoroughly describe the contents. The multifractal model, which is more accurate, is not practical because it uses multifractal spectra as functions to represent signals. Therefore, on the basis of the framework of IDC theory, this paper proposes a stable multifractal model of network traffic. It is tested on several traces by using the method of wavelet transforms that the model fits traffic precisely in terms of both scale behaviors and marginal distributions. As a specific case of multifractal processes, this model, by estimations of four parameters, can specify the representation of the multifractal exponent.
There have been two a priori models up till now concerning network traffic: self-similar and multifractal models. The self-similar model is simple enough to characterize network traffic with the single exponent H, however it can not thoroughly describe the contents. The multifractal model, which is more accurate, is not practical because it uses multifractal spectra as functions to represent signals. Therefore, on the basis of the framework of IDC theory, this paper proposes a stable multifractal model of network traffic. It is tested on several traces by using the method of wavelet transforms that the model fits traffic precisely in terms of both scale behaviors and marginal distributions. As a specific case of multifractal processes, this model, by estimations of four parameters, can specify the representation of the multifractal exponent.
2006, 28(6): 1129-1134.
Abstract:
Random Early Detection (RED) is a kind of buffer management algorithms which is widely used in the current Internet. To improve the adaptability and fairness of RED is one of the main tasks of the active queue management. In this paper, the buffer occupancy of individual flow is replaced by a new introduced variable Sharing Index to indicate the network resource share among different flows, so as to overcome the limitation of buffer occupancy. The definition of Sharing Index in wireless networks is also extended to make it consider both fairness and system performance (channel condition). Through defining rules of both Sharing Index and queue length, a fuzzy logic based buffer management algorithm named FF-RED is proposed. When calculating packet dropping probability in FF-RED algorithm, the probability will further increase or decrease based on the sharing of network resource (by means of Sharing Index), so it can use the difference between flows to make congestion relief more quickly, and it has better adaptability and fairness. Simulation results show that the system performance is improved through using the proposed algorithm.
Random Early Detection (RED) is a kind of buffer management algorithms which is widely used in the current Internet. To improve the adaptability and fairness of RED is one of the main tasks of the active queue management. In this paper, the buffer occupancy of individual flow is replaced by a new introduced variable Sharing Index to indicate the network resource share among different flows, so as to overcome the limitation of buffer occupancy. The definition of Sharing Index in wireless networks is also extended to make it consider both fairness and system performance (channel condition). Through defining rules of both Sharing Index and queue length, a fuzzy logic based buffer management algorithm named FF-RED is proposed. When calculating packet dropping probability in FF-RED algorithm, the probability will further increase or decrease based on the sharing of network resource (by means of Sharing Index), so it can use the difference between flows to make congestion relief more quickly, and it has better adaptability and fairness. Simulation results show that the system performance is improved through using the proposed algorithm.
2006, 28(6): 1135-1140.
Abstract:
Active Networks (AN) are a novel approach to network architecture in which the switches of the network perform customized computations on the messages flowing through them. AN seems to be particularly useful in the context of QoS support. In this paper, an active routing protocol is proposed which is called Mulli-constraints Active Routing(MAR) by introducing QoS routing into AN. Some simulation and analysis prove this protocol is more concise, more controllable, and more flexible than other QoS routing mechanisms at present.
Active Networks (AN) are a novel approach to network architecture in which the switches of the network perform customized computations on the messages flowing through them. AN seems to be particularly useful in the context of QoS support. In this paper, an active routing protocol is proposed which is called Mulli-constraints Active Routing(MAR) by introducing QoS routing into AN. Some simulation and analysis prove this protocol is more concise, more controllable, and more flexible than other QoS routing mechanisms at present.
2006, 28(6): 1141-1144.
Abstract:
In Eurocrypt 2004, Canetti, Halevi and Katz proposed a method for constructing Chosen Ciphertext secure ( ie., CCA secure) public key encryption from any Selective-ID secure ID-Based Encryption (IBE). However, this method needs one time signature and thus adds noticeable overhead to the underling scheme. In this paper, a new CCA secure public key cryptosystem is constructed from the Adaptive-ID secure IBE scheme proposed by Waters. Here, the identity is the hash of the first two parts of the ciphertext, and the bilinear map is used to test the ciphertext validity. The proposal is much more efficient than those obtained from the general CHK method. The security of the new scheme is proved under the standard Decisional Bilinear Diffie-Hellman (DBDH) assumption.
In Eurocrypt 2004, Canetti, Halevi and Katz proposed a method for constructing Chosen Ciphertext secure ( ie., CCA secure) public key encryption from any Selective-ID secure ID-Based Encryption (IBE). However, this method needs one time signature and thus adds noticeable overhead to the underling scheme. In this paper, a new CCA secure public key cryptosystem is constructed from the Adaptive-ID secure IBE scheme proposed by Waters. Here, the identity is the hash of the first two parts of the ciphertext, and the bilinear map is used to test the ciphertext validity. The proposal is much more efficient than those obtained from the general CHK method. The security of the new scheme is proved under the standard Decisional Bilinear Diffie-Hellman (DBDH) assumption.
2006, 28(6): 1145-1149.
Abstract:
A new kind of group-oriented signature is presented with a new signature model in this paper. The signature has the following properties: it is based on ID cryptography concept; does not have the function of key escrow, that is, no one, other than the member himself, knows the secret key, even the PKG does not know; the member in the designated group can verify the signature independently. The secret sharing is not used in the signature, so the cooperation among the members is not needed. Comparing to other group-oriented signature, the new one uses less system resources, and improves the system efficiency.
A new kind of group-oriented signature is presented with a new signature model in this paper. The signature has the following properties: it is based on ID cryptography concept; does not have the function of key escrow, that is, no one, other than the member himself, knows the secret key, even the PKG does not know; the member in the designated group can verify the signature independently. The secret sharing is not used in the signature, so the cooperation among the members is not needed. Comparing to other group-oriented signature, the new one uses less system resources, and improves the system efficiency.
2006, 28(6): 1150-1152.
Abstract:
The fractal parameter is very import in studying the chaos signal. Wavelet transform is a useful multi-scale tool for analyzing the fractal. In this paper, the self-similarity property of chaos signal and the properties of the coefficient of wavelet transform in different scales are discussed, and the signal of Boost circuit in chaotic state is studied by wavelet transform. From deduction, the algorithm of calculating the fractal parameter of the chaotic attractor of the circuit is got. Finally, the calculation and simulation are done.
The fractal parameter is very import in studying the chaos signal. Wavelet transform is a useful multi-scale tool for analyzing the fractal. In this paper, the self-similarity property of chaos signal and the properties of the coefficient of wavelet transform in different scales are discussed, and the signal of Boost circuit in chaotic state is studied by wavelet transform. From deduction, the algorithm of calculating the fractal parameter of the chaotic attractor of the circuit is got. Finally, the calculation and simulation are done.
