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2007 Vol. 29, No. 3
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2007, 29(3): 509-512.
doi: 10.3724/SP.J.1146.2005.00844
Abstract:
Super resolution estimates of target ranges, azimuth angles and Doppler frequencies for HF-Surface Wave Radar (HF-SWR) are investigated in this paper. An algorithm based on the method of Direction Of Arrival (DOA) matrix to achieve simultaneous target parameters estimates is proposed. The estimates of target ranges, azimuth angles and Doppler frequencies can be obtained from the eigenvectors and the corresponding eigenvalues of the DOA matrix respectively. This method is computationally efficient with high resolution, and with automatic combine of the estimated target parameters. Simulation results validate the effectiveness of this method.
Super resolution estimates of target ranges, azimuth angles and Doppler frequencies for HF-Surface Wave Radar (HF-SWR) are investigated in this paper. An algorithm based on the method of Direction Of Arrival (DOA) matrix to achieve simultaneous target parameters estimates is proposed. The estimates of target ranges, azimuth angles and Doppler frequencies can be obtained from the eigenvectors and the corresponding eigenvalues of the DOA matrix respectively. This method is computationally efficient with high resolution, and with automatic combine of the estimated target parameters. Simulation results validate the effectiveness of this method.
2007, 29(3): 513-516.
doi: 10.3724/SP.J.1146.2005.00754
Abstract:
This paper proposes a new method based on statistical model of wavelet coefficients combined with modification to them according to significant coefficient rule. In the method, wavelet coefficients of logarithmic image are firstly modeled as mixture density of two Gaussian distributions with zero mean. In order to incorporate the spatial dependencies into the denoising procedure，Hidden Markov Tree (HMT) model is explored and Expectation Maximization (EM) algorithm is proposed to estimate model parameters. Bayes Minimum Mean Square Error (Bayes MMSE)method is used to estimate the wavelet coefficients free of noise. The wavelet coefficients are updated according to a rule whether the coefficient is a significant one or not. 2D inverse DWT and exponential transform are performed on the updated coefficients to get denoised SAR image. Experimental Results using real SAR images demonstrate that the method can not only reduce the speckle but also preserve edges and radiometric scatter points.
This paper proposes a new method based on statistical model of wavelet coefficients combined with modification to them according to significant coefficient rule. In the method, wavelet coefficients of logarithmic image are firstly modeled as mixture density of two Gaussian distributions with zero mean. In order to incorporate the spatial dependencies into the denoising procedure，Hidden Markov Tree (HMT) model is explored and Expectation Maximization (EM) algorithm is proposed to estimate model parameters. Bayes Minimum Mean Square Error (Bayes MMSE)method is used to estimate the wavelet coefficients free of noise. The wavelet coefficients are updated according to a rule whether the coefficient is a significant one or not. 2D inverse DWT and exponential transform are performed on the updated coefficients to get denoised SAR image. Experimental Results using real SAR images demonstrate that the method can not only reduce the speckle but also preserve edges and radiometric scatter points.
2007, 29(3): 517-520.
doi: 10.3724/SP.J.1146.2005.01584
Abstract:
The property that the ordered statistics CFAR(OS-CFAR) detector can obtain constant false alarm rate under homogeneous Log-normal distributed clutter background is proved in this paper, when the shape parameter of probability density function is known. Both the detection performance expressions with non-fluctuating target and the ADT (average decision threshold) expressions of the OS-CFAR detector are derived. Finally, the optimal order value and the signal-clutter-ratio losses compared with ideal CFAR of the OS-CFAR detector are discussed by numerical method when the number of reference cells is taken different values.
The property that the ordered statistics CFAR(OS-CFAR) detector can obtain constant false alarm rate under homogeneous Log-normal distributed clutter background is proved in this paper, when the shape parameter of probability density function is known. Both the detection performance expressions with non-fluctuating target and the ADT (average decision threshold) expressions of the OS-CFAR detector are derived. Finally, the optimal order value and the signal-clutter-ratio losses compared with ideal CFAR of the OS-CFAR detector are discussed by numerical method when the number of reference cells is taken different values.
2007, 29(3): 521-523.
doi: 10.3724/SP.J.1146.2005.00997
Abstract:
The estimation of rotation angle is the precondition for ISAR imaging. In this passage, a new method based on the analysis of the echo signals is proposed. The signals in different range bin are approximated as the multi-component third-order polynomial signals, and the proportion of third-order phase coefficient to first-order phase coefficient is constant just equal to the square of the rotation rate. Then the parameters of the third-order polynomial signal are estimated by the maximum likelihood method. The results of real data show the validity of the method proposed.
The estimation of rotation angle is the precondition for ISAR imaging. In this passage, a new method based on the analysis of the echo signals is proposed. The signals in different range bin are approximated as the multi-component third-order polynomial signals, and the proportion of third-order phase coefficient to first-order phase coefficient is constant just equal to the square of the rotation rate. Then the parameters of the third-order polynomial signal are estimated by the maximum likelihood method. The results of real data show the validity of the method proposed.
River Detection in SAR Images Based on Edge Extraction in Wavelet Domain and Ridge Tracing Technique
2007, 29(3): 524-527.
doi: 10.3724/SP.J.1146.2005.00992
Abstract:
This paper deals with automatic river detection in SAR images. A new method is proposed using the boundary extraction in wavelet domain and merging the water region by ridge tracing. In the method, edge detection is approached by direct spatial correlation of wavelet transform at several adjacent scales. It is much easier than the algorithm of WTMM proposed by Mallat and proved to be more efficient. And the ridge tracking based on gray scale image , which is applied in fingerprint tracing, is introduced here to complete the river bank linking and river connecting. This improvement avoids the disadvantages of the Snake model widely used in linking the coastline. The river detection result from the method is good at connection and location. And the method is much more efficient and adaptive to the complicated bank.
This paper deals with automatic river detection in SAR images. A new method is proposed using the boundary extraction in wavelet domain and merging the water region by ridge tracing. In the method, edge detection is approached by direct spatial correlation of wavelet transform at several adjacent scales. It is much easier than the algorithm of WTMM proposed by Mallat and proved to be more efficient. And the ridge tracking based on gray scale image , which is applied in fingerprint tracing, is introduced here to complete the river bank linking and river connecting. This improvement avoids the disadvantages of the Snake model widely used in linking the coastline. The river detection result from the method is good at connection and location. And the method is much more efficient and adaptive to the complicated bank.
2007, 29(3): 528-531.
doi: 10.3724/SP.J.1146.2005.00688
Abstract:
A passive radar imaging algorithm is presented in the paper. Receiving the reflected signals from multiple television stations located at various aspect angles, the algorithm can image moving object by synthesizing multiple sub-apertures of the television stations which are induced by the small angular rotations of the object into a wide-angle equivalent aperture. In addition to the low complexity in computation, the algorithm only uses the carrier waves of television stations while requires a small rotation angle of object in the area where dense television stations are available. Finally, the theoretical validity is illustrated by simulation results.
A passive radar imaging algorithm is presented in the paper. Receiving the reflected signals from multiple television stations located at various aspect angles, the algorithm can image moving object by synthesizing multiple sub-apertures of the television stations which are induced by the small angular rotations of the object into a wide-angle equivalent aperture. In addition to the low complexity in computation, the algorithm only uses the carrier waves of television stations while requires a small rotation angle of object in the area where dense television stations are available. Finally, the theoretical validity is illustrated by simulation results.
2007, 29(3): 532-535.
doi: 10.3724/SP.J.1146.2005.01036
Abstract:
A new IMM algorithm for tracking maneuvering target is proposed, which uses a CS(Current Statistical) model with a fading factor and a CV(Constant Velocity) model for interaction. The CS model itself has a high precision when tracking common maneuvering target, its ability of tracking a sudden maneuvering target has been improved by introducing a fading factor of Strong Tracking Filter (STF), and the high precision to track non maneuvering targets can be ensured by interacting with the CV model. Simulation results show that, when there is only common maneuver the performance of the algorithm is the same with the IMM-CS/CV, when there is a sudden maneuver, the performance of this algorithm is much better than the IMM-CS/CV.
A new IMM algorithm for tracking maneuvering target is proposed, which uses a CS(Current Statistical) model with a fading factor and a CV(Constant Velocity) model for interaction. The CS model itself has a high precision when tracking common maneuvering target, its ability of tracking a sudden maneuvering target has been improved by introducing a fading factor of Strong Tracking Filter (STF), and the high precision to track non maneuvering targets can be ensured by interacting with the CV model. Simulation results show that, when there is only common maneuver the performance of the algorithm is the same with the IMM-CS/CV, when there is a sudden maneuver, the performance of this algorithm is much better than the IMM-CS/CV.
2007, 29(3): 536-539.
doi: 10.3724/SP.J.1146.2005.00673
Abstract:
SAR/DPCA(Displaced Phase Center Antenna) technique is a simple and practical method of multi-channel SAR/GMTI(Graund Moving Target Indication), but in practice it is limited by some kinds of errors, in which antenna phase center velocity error and channel mismatch are the most important errors. In this paper, the error analysis model is founded and the loss of moving target detection performance is analyzed under the circumstance of antenna phase center velocity error or channel mismatch. The error analysis results are shown on the figures and the range of detectable velocity, blind velocity and minimum detectable velocity are confirmed on the basis of actual parameters of dual-channel SAR/DPCA system.
SAR/DPCA(Displaced Phase Center Antenna) technique is a simple and practical method of multi-channel SAR/GMTI(Graund Moving Target Indication), but in practice it is limited by some kinds of errors, in which antenna phase center velocity error and channel mismatch are the most important errors. In this paper, the error analysis model is founded and the loss of moving target detection performance is analyzed under the circumstance of antenna phase center velocity error or channel mismatch. The error analysis results are shown on the figures and the range of detectable velocity, blind velocity and minimum detectable velocity are confirmed on the basis of actual parameters of dual-channel SAR/DPCA system.
2007, 29(3): 540-543.
doi: 10.3724/SP.J.1146.2005.00985
Abstract:
This paper proposes a novel mixed genetic algorithmActive Mutating Anneal-Genetic Algorithm(AMAGA) based on sorting and describes an elevation beam widening method of spaceborne SAR antenna, which only changes the phases at part of array elements and so called Partly Phase-only Weighting Method (PPWM). Moreover, the resulting phases need not be quantized and can be directly applied to engineering project. In comparison with the fully phase-only weighting method for beam widening, the partly phase-only method for beam widening is more realizable and more flexible. Simulated examples show that the mainlobe notch of widened beam can be controlled finely with lower sidelobe.
This paper proposes a novel mixed genetic algorithmActive Mutating Anneal-Genetic Algorithm(AMAGA) based on sorting and describes an elevation beam widening method of spaceborne SAR antenna, which only changes the phases at part of array elements and so called Partly Phase-only Weighting Method (PPWM). Moreover, the resulting phases need not be quantized and can be directly applied to engineering project. In comparison with the fully phase-only weighting method for beam widening, the partly phase-only method for beam widening is more realizable and more flexible. Simulated examples show that the mainlobe notch of widened beam can be controlled finely with lower sidelobe.
2007, 29(3): 544-548.
doi: 10.3724/SP.J.1146.2005.00816
Abstract:
In this paper, the variation of Doppler frequency of the group flying targets is analyzed. For low resolution radars, the echoes of targets can be modeled as Linear Frequency Modulated (LFM) signals. A method for detecting the number of targets is proposed. A fast estimation of character of the whole in the time-frequency domain can be obtained through the Radon-WVD (Radon-Wigner Ville Distribution). The cross-terms of WVD have no influence on the result of the estimation. The method performs well under either higher SNR or lower SNR. The experimental results demonstrate the validity of the method.
In this paper, the variation of Doppler frequency of the group flying targets is analyzed. For low resolution radars, the echoes of targets can be modeled as Linear Frequency Modulated (LFM) signals. A method for detecting the number of targets is proposed. A fast estimation of character of the whole in the time-frequency domain can be obtained through the Radon-WVD (Radon-Wigner Ville Distribution). The cross-terms of WVD have no influence on the result of the estimation. The method performs well under either higher SNR or lower SNR. The experimental results demonstrate the validity of the method.
2007, 29(3): 549-552.
doi: 10.3724/SP.J.1146.2005.01023
Abstract:
Utilizing Dynamic Bayesian Networks (DBNs) to deal with multi-temporal remote sensing data, the multi-temporal data of different time can be input simultaneously, and the classification and the acquirement of relationships between the output types can be finished simultaneously. Using the Landsat TM remote sensing data of Beijing eastern area acquired in May of 1994, 2001 and 2003 for the experiment, the experimental results indicate that the DBN-based change detection method is a new effective method of remote sensing change detection, and show its great potential for the research on the analysis of the dynamic changes of remote sensing time-series data.
Utilizing Dynamic Bayesian Networks (DBNs) to deal with multi-temporal remote sensing data, the multi-temporal data of different time can be input simultaneously, and the classification and the acquirement of relationships between the output types can be finished simultaneously. Using the Landsat TM remote sensing data of Beijing eastern area acquired in May of 1994, 2001 and 2003 for the experiment, the experimental results indicate that the DBN-based change detection method is a new effective method of remote sensing change detection, and show its great potential for the research on the analysis of the dynamic changes of remote sensing time-series data.
2007, 29(3): 553-556.
doi: 10.3724/SP.J.1146.2005.01585
Abstract:
This paper presents the arrangement strategy of ground stations for a regional positioning system and derives the formulas for calculating GDOP with 4 grounds stations. With the flying users known altitude, the highest positioning precision can be acquired quickly. Since the formulas do not involve the multiplication and inverse of matrix, the calculations are reduced.
This paper presents the arrangement strategy of ground stations for a regional positioning system and derives the formulas for calculating GDOP with 4 grounds stations. With the flying users known altitude, the highest positioning precision can be acquired quickly. Since the formulas do not involve the multiplication and inverse of matrix, the calculations are reduced.
2007, 29(3): 557-559.
doi: 10.3724/SP.J.1146.2005.00999
Abstract:
In this paper, a high performance frequency domain cancellation algorithm is presented to suppress the noise amplitude modulation interference. By the logarithm transform, the carrier frequency and initial phase of the jamming signal are estimated from the imaginary part of the transformed echo signal including jamming, and then, the echo signal is demodulated with the estimated jamming carrier frequency. Finally, the jamming may be suppressed with frequency domain cancellation. Simulation shows that the proposed method has a low computational cost and high performance.
In this paper, a high performance frequency domain cancellation algorithm is presented to suppress the noise amplitude modulation interference. By the logarithm transform, the carrier frequency and initial phase of the jamming signal are estimated from the imaginary part of the transformed echo signal including jamming, and then, the echo signal is demodulated with the estimated jamming carrier frequency. Finally, the jamming may be suppressed with frequency domain cancellation. Simulation shows that the proposed method has a low computational cost and high performance.
2007, 29(3): 560-564.
doi: 10.3724/SP.J.1146.2006.00882
Abstract:
There are many uncertain decision-making questions, in which the information is incomplete and vague, in the electronic equipment test system. The grey system theory is a powerful tool to settle the kind question. The component of the electronic equipment test system and its characteristic in the traditional sense are summarized firstly. Then from the view of system, the grey characteristics, including structure grey, relation grey, model grey and cognition grey, of the electronic equipment test system are proposed. Finally, the source and the grey model of uncertain information in electronic equipment tests are studied. The uncertainty measurement model of the test datum and the average uncertainty measurement model of the system are introduced. The research conclusions can offer theoretic supports for the increasing application of the grey system theory to the domain of the electronic equipment test system.
There are many uncertain decision-making questions, in which the information is incomplete and vague, in the electronic equipment test system. The grey system theory is a powerful tool to settle the kind question. The component of the electronic equipment test system and its characteristic in the traditional sense are summarized firstly. Then from the view of system, the grey characteristics, including structure grey, relation grey, model grey and cognition grey, of the electronic equipment test system are proposed. Finally, the source and the grey model of uncertain information in electronic equipment tests are studied. The uncertainty measurement model of the test datum and the average uncertainty measurement model of the system are introduced. The research conclusions can offer theoretic supports for the increasing application of the grey system theory to the domain of the electronic equipment test system.
2007, 29(3): 565-569.
doi: 10.3724/SP.J.1146.2004.01296
Abstract:
Target locating based on the measuring of the azimuth and elevation data of targets is a new way of target passive locating. In this paper, a algorithm formula for three station locating is put forward, several filtering algorithms is discussed, precision analysis for different targets locating and filtering algorithms is completed, and finally the result is imitated by computer. The research shows that target passive locating and tracking can be achieved by measuring of the azimuth and elevation data of targets. The academic research and discussion in the article actually is of particular applied value.
Target locating based on the measuring of the azimuth and elevation data of targets is a new way of target passive locating. In this paper, a algorithm formula for three station locating is put forward, several filtering algorithms is discussed, precision analysis for different targets locating and filtering algorithms is completed, and finally the result is imitated by computer. The research shows that target passive locating and tracking can be achieved by measuring of the azimuth and elevation data of targets. The academic research and discussion in the article actually is of particular applied value.
2007, 29(3): 570-573.
doi: 10.3724/SP.J.1146.2005.00857
Abstract:
Based on fractional wave packet transform, a new hybrid time-frequency transform: Gauss Short-time Fractional Fourier Transform (GSFrFT) is proposed for the detection and estimation of Linear Frequency-Modulated (LFM) signals. Multiple LFM signals can be detected in low SNR by choosing the rotated angle and cross-items can be avoided. Analytical expression of the transform result is given. The simulation results also show that the GSFrFT is valid.
Based on fractional wave packet transform, a new hybrid time-frequency transform: Gauss Short-time Fractional Fourier Transform (GSFrFT) is proposed for the detection and estimation of Linear Frequency-Modulated (LFM) signals. Multiple LFM signals can be detected in low SNR by choosing the rotated angle and cross-items can be avoided. Analytical expression of the transform result is given. The simulation results also show that the GSFrFT is valid.
2007, 29(3): 574-577.
doi: 10.3724/SP.J.1146.2005.00728
Abstract:
Aiming at the problem of phase error caused by normal filters in signal processing, this paper summarizes the important meaning of digital filtering with zero-phase error, and introduces the all phase method as a new design method of digital filter with zero-phase based on the two traditional methods, that is FRR and RRF methods. And gives the demonstrations on the simulation experiments about the three methods, solving the problem of phase error in digital signal processing. It points out that all phase method is a good method of designing zero-phase digital filter, and this method is mechanically realizable but the two tradition methods can not on analyzing and comparing the three design methods. Finally, recommends the implement fields of the all phase method as a new method of designing digital filter.
Aiming at the problem of phase error caused by normal filters in signal processing, this paper summarizes the important meaning of digital filtering with zero-phase error, and introduces the all phase method as a new design method of digital filter with zero-phase based on the two traditional methods, that is FRR and RRF methods. And gives the demonstrations on the simulation experiments about the three methods, solving the problem of phase error in digital signal processing. It points out that all phase method is a good method of designing zero-phase digital filter, and this method is mechanically realizable but the two tradition methods can not on analyzing and comparing the three design methods. Finally, recommends the implement fields of the all phase method as a new method of designing digital filter.
2007, 29(3): 578-581.
doi: 10.3724/SP.J.1146.2005.00724
Abstract:
The paper simplifies the joint diagonalization of matrices into optimization problem which only includes the eigen matrix. For solving the problem conveniently, each row vector of the eigen matrix is parameterized, then utilizes the improved genetic algorithm to get the optimal parameter. The algorithm improves the choose of chromosome and probability of cross with variation, introduces simulated anneal technology into operator of crossing and variation. Finally it unifies the gradient algorithm to seek local optimality. The simulation result verify the algorithm.
The paper simplifies the joint diagonalization of matrices into optimization problem which only includes the eigen matrix. For solving the problem conveniently, each row vector of the eigen matrix is parameterized, then utilizes the improved genetic algorithm to get the optimal parameter. The algorithm improves the choose of chromosome and probability of cross with variation, introduces simulated anneal technology into operator of crossing and variation. Finally it unifies the gradient algorithm to seek local optimality. The simulation result verify the algorithm.
2007, 29(3): 582-584.
doi: 10.3724/SP.J.1146.2005.00756
Abstract:
This paper provides the Cramer-Rao lower bound of alternating separation algorithm. In the Cramer-Rao bound, the #61485; inversion of a definite matrix must be established, which extends the theory of Cramer-Rao bound. In additional, this Cramer-Rao bound displays the multiple signal effect in the parameter estimated process. By discussion the Cramer-Rao lower bound of Alternating Separation algorithm, some properties of the signal separation operator matrix are given.
This paper provides the Cramer-Rao lower bound of alternating separation algorithm. In the Cramer-Rao bound, the #61485; inversion of a definite matrix must be established, which extends the theory of Cramer-Rao bound. In additional, this Cramer-Rao bound displays the multiple signal effect in the parameter estimated process. By discussion the Cramer-Rao lower bound of Alternating Separation algorithm, some properties of the signal separation operator matrix are given.
2007, 29(3): 585-588.
doi: 10.3724/SP.J.1146.2005.00836
Abstract:
According to simple computation, good anti-noise ability and low precision of Katz algorithm and complex computation and good precision of box-counting dimension and correlation dimension, an Improvement fractal algorithm Based on Wave (IBW) is presented and analyzed through the fractal Brown curve and noisy speech according to the characteristic of the box dimension and Katz dimension. The theory analyse and experiment show that IBW-FD has lower computation and higher precision than Katz dimension and box-counting dimension. IBW-FD also has stronger ability of anti-noise and distinguish Gaussian noise and speech than the others. It shows that IBW-FD is the good speech fractal algorithm because of low complexity, good precision and nice anti-noise ability.
According to simple computation, good anti-noise ability and low precision of Katz algorithm and complex computation and good precision of box-counting dimension and correlation dimension, an Improvement fractal algorithm Based on Wave (IBW) is presented and analyzed through the fractal Brown curve and noisy speech according to the characteristic of the box dimension and Katz dimension. The theory analyse and experiment show that IBW-FD has lower computation and higher precision than Katz dimension and box-counting dimension. IBW-FD also has stronger ability of anti-noise and distinguish Gaussian noise and speech than the others. It shows that IBW-FD is the good speech fractal algorithm because of low complexity, good precision and nice anti-noise ability.
2007, 29(3): 589-592.
doi: 10.3724/SP.J.1146.2005.00717
Abstract:
A Voice Activity Detection (VAD) method for microphone array signals in directional noise field is proposed. As the noises received by different microphones are correlated with each other in directional noise field, relatively pure speech can be derived from any two array signals by using Blind Source Separation (BSS) method. The generalized correlation method is used to estimate time delay between this relatively pure signal and every channel signals of microphone array. In the same time, a long-term speech information method is applied to the relatively pure speech signal to obtain its VAD result. Then this VAD result is used as reference to produce those of all array signals by the time shifting of it according to each time delay values. Simulation results illustrate the validity of the proposed method.
A Voice Activity Detection (VAD) method for microphone array signals in directional noise field is proposed. As the noises received by different microphones are correlated with each other in directional noise field, relatively pure speech can be derived from any two array signals by using Blind Source Separation (BSS) method. The generalized correlation method is used to estimate time delay between this relatively pure signal and every channel signals of microphone array. In the same time, a long-term speech information method is applied to the relatively pure speech signal to obtain its VAD result. Then this VAD result is used as reference to produce those of all array signals by the time shifting of it according to each time delay values. Simulation results illustrate the validity of the proposed method.
2007, 29(3): 593-597.
doi: 10.3724/SP.J.1146.2005.00941
Abstract:
To take full advantage of the anisotropic texture information and multidimensional singular information in an image, a novel method for image fusion based on anisotropic texture information is presented in this paper. And the local energy operator is provided as the fusion strategies. This method can capture and preserve the anisotropic edge information and detail direction texture of collected images effectively, and it is integrated with brushlet transform to the fusion of natural images, aerial photos and medical images. Objective parameters of evaluating the fusion performance are provided via entropy and cross entropy. Comparisons of performance of Brushlet-based and wavelet-based fusion methods are provided. It is shown that the proposed method has improved the fusion result of wavelet-based ones not only in visual effect but also in objective evaluating parameters.
To take full advantage of the anisotropic texture information and multidimensional singular information in an image, a novel method for image fusion based on anisotropic texture information is presented in this paper. And the local energy operator is provided as the fusion strategies. This method can capture and preserve the anisotropic edge information and detail direction texture of collected images effectively, and it is integrated with brushlet transform to the fusion of natural images, aerial photos and medical images. Objective parameters of evaluating the fusion performance are provided via entropy and cross entropy. Comparisons of performance of Brushlet-based and wavelet-based fusion methods are provided. It is shown that the proposed method has improved the fusion result of wavelet-based ones not only in visual effect but also in objective evaluating parameters.
2007, 29(3): 598-600.
doi: 10.3724/SP.J.1146.2005.00975
Abstract:
In the real world, it is a common problem how to estimate the state of nonlinear systems with colored noise. The Extended Kalman Filter (EKF) is generally used to linearize the state or measure equations of the nonlinear system, and the linear method can be used. However, the performance of the EKF may not be always good due to the linearization error. In this paper, a new method is proposed. Firstly, the method transforms the measure equation of the system, so the colored noise of the equation can be changed into white noise. Then, the Unscented Kalman Filter (UKF) can be used to estimate the state of the system. Although, the linearization of the equations is also needed in this method, it will not affect the precision of the method, because the linearization is performed during the course of computing the error of the new measure equation. The results of the simulation show that the new method can effectively get the precision state estimation of the nonlinear system with colored nois.
In the real world, it is a common problem how to estimate the state of nonlinear systems with colored noise. The Extended Kalman Filter (EKF) is generally used to linearize the state or measure equations of the nonlinear system, and the linear method can be used. However, the performance of the EKF may not be always good due to the linearization error. In this paper, a new method is proposed. Firstly, the method transforms the measure equation of the system, so the colored noise of the equation can be changed into white noise. Then, the Unscented Kalman Filter (UKF) can be used to estimate the state of the system. Although, the linearization of the equations is also needed in this method, it will not affect the precision of the method, because the linearization is performed during the course of computing the error of the new measure equation. The results of the simulation show that the new method can effectively get the precision state estimation of the nonlinear system with colored nois.
2007, 29(3): 601-605.
doi: 10.3724/SP.J.1146.2005.01015
Abstract:
With the volume of information available on the Internet and corporate intranets continues to increase, text classification has become one of the key technology in organizing and processing large amount of document data. This paper gives a novel method of Chinese text categorization based on a combination of ontology with statistical method. In this study, first, linguistic ontology knowledge bank will be respectively acquired by learning training corpus for various classes to determine the various categorizations. For a actual document, the evaluation value will respectively be gotten by various linguistic ontology knowledge bank and the categorization will be judged by the highest evaluation value. This method is compared with Bayes, k-nearest neighbor and support vector machine, The primary experimental results show that the method outperforms that previous work.
With the volume of information available on the Internet and corporate intranets continues to increase, text classification has become one of the key technology in organizing and processing large amount of document data. This paper gives a novel method of Chinese text categorization based on a combination of ontology with statistical method. In this study, first, linguistic ontology knowledge bank will be respectively acquired by learning training corpus for various classes to determine the various categorizations. For a actual document, the evaluation value will respectively be gotten by various linguistic ontology knowledge bank and the categorization will be judged by the highest evaluation value. This method is compared with Bayes, k-nearest neighbor and support vector machine, The primary experimental results show that the method outperforms that previous work.
2007, 29(3): 606-610.
doi: 10.3724/SP.J.1146.2005.00770
Abstract:
Based on cross sub-image block, a novel algorithm of digital image stabilization is presented, which makes use of the similar features existed between adjacent images. First, the representative points which represent global features are acquired through crossing sub-image blocks. Then, on the basis of motion model, energy function is structured, through which, the representative points between adjacent images are matched and global motion parameters can be estimated. Finally, the image stabilization process is realized via motion compensation with cumulated global motion parameters. The combination of representative points and motion model could produce good performance when the image fluctuation contains both translational and rotational motions. And results of strong noise experiments show the robust of the algorithm.
Based on cross sub-image block, a novel algorithm of digital image stabilization is presented, which makes use of the similar features existed between adjacent images. First, the representative points which represent global features are acquired through crossing sub-image blocks. Then, on the basis of motion model, energy function is structured, through which, the representative points between adjacent images are matched and global motion parameters can be estimated. Finally, the image stabilization process is realized via motion compensation with cumulated global motion parameters. The combination of representative points and motion model could produce good performance when the image fluctuation contains both translational and rotational motions. And results of strong noise experiments show the robust of the algorithm.
2007, 29(3): 611-615.
doi: 10.3724/SP.J.1146.2005.01069
Abstract:
In this paper, based on rough logic theory, the design of rough neural network in the meaning of rough logic is studied. The character of rough logic neural network and fuzzy logic neural network are analyzed and compared. The validity of the rough logic neural network can be verified in the land cover classification experiment of the Landsat TM remote sensing image of Chongqing area. The rough logic neural network has superiorities at the aspect of structure and convergence.
In this paper, based on rough logic theory, the design of rough neural network in the meaning of rough logic is studied. The character of rough logic neural network and fuzzy logic neural network are analyzed and compared. The validity of the rough logic neural network can be verified in the land cover classification experiment of the Landsat TM remote sensing image of Chongqing area. The rough logic neural network has superiorities at the aspect of structure and convergence.
2007, 29(3): 616-621.
doi: 10.3724/SP.J.1146.2005.01029
Abstract:
In order to decrease the communication bandwidth and save the transmitting power in the wireless endoscopy capsule, this paper presents a low complexity and high efficient near-lossless and lossless image compression algorithm for hardware design based on the Bayer format image. The algorithm can provide better compression performance and lower complexity than conventional interpolation-first methods and other existing similar compression-first methods. Moreover, the algorithm can provide lossless compression for the region of interest (ROI) and high quality compression for other regions. This algorithm can provide low average compression rate (2.18bit/pixel) with high image quality (larger than 47.57dB) for wireless endoscopic images.
In order to decrease the communication bandwidth and save the transmitting power in the wireless endoscopy capsule, this paper presents a low complexity and high efficient near-lossless and lossless image compression algorithm for hardware design based on the Bayer format image. The algorithm can provide better compression performance and lower complexity than conventional interpolation-first methods and other existing similar compression-first methods. Moreover, the algorithm can provide lossless compression for the region of interest (ROI) and high quality compression for other regions. This algorithm can provide low average compression rate (2.18bit/pixel) with high image quality (larger than 47.57dB) for wireless endoscopic images.
2007, 29(3): 622-625.
doi: 10.3724/SP.J.1146.2005.01010
Abstract:
Image registration based on mutual information is of high accuracy and robustness. Hence, it has received much attention these years. Unfortunately, the mutual information function is generally not a smooth function but one containing many local maxima, which has a large influence on optimization. This paper proposes a registration method based on wavelet representation. In this method the mutual information is used as the similarity measure and a hybrid algorithm combined by ant colony algorithm and Powells method as the search technique. This method is applied to the 3D registration of CT and MR. Experiments shows that this registration method could efficiently restrain local maxima of mutual information function and the subvoxel accuracy can be achieved.
Image registration based on mutual information is of high accuracy and robustness. Hence, it has received much attention these years. Unfortunately, the mutual information function is generally not a smooth function but one containing many local maxima, which has a large influence on optimization. This paper proposes a registration method based on wavelet representation. In this method the mutual information is used as the similarity measure and a hybrid algorithm combined by ant colony algorithm and Powells method as the search technique. This method is applied to the 3D registration of CT and MR. Experiments shows that this registration method could efficiently restrain local maxima of mutual information function and the subvoxel accuracy can be achieved.
2007, 29(3): 626-630.
doi: 10.3724/SP.J.1146.2006.00306
Abstract:
In this paper, a GPSA face recognition approach by probabilistic subspace analysis in Gabor wavelet domain is presented. First, an improved Gabor representation scheme for face images is given, then a Gabor based probabilistic subspace model is built, so recognition is performed in a manner of probabilistic matching. The discriminatory information yielded from both probabilistic subspace analysis and Gabor representation is exploited altogether in GPSA method, and hence the robustness of face recognition system is enhanced effectively. The experimental results on a mixture face database including 190 individuals show that the proposed GPSA method outperforms the existing PSA method.
In this paper, a GPSA face recognition approach by probabilistic subspace analysis in Gabor wavelet domain is presented. First, an improved Gabor representation scheme for face images is given, then a Gabor based probabilistic subspace model is built, so recognition is performed in a manner of probabilistic matching. The discriminatory information yielded from both probabilistic subspace analysis and Gabor representation is exploited altogether in GPSA method, and hence the robustness of face recognition system is enhanced effectively. The experimental results on a mixture face database including 190 individuals show that the proposed GPSA method outperforms the existing PSA method.
2007, 29(3): 631-634.
doi: 10.3724/SP.J.1146.2005.00852
Abstract:
A new concept of time-frequency rate distribution is proposed. It can serve as an effective tool for superimposed LFM signal parameter estimation. A new method based on the time-frequency rate distribution is also proposed. Performance analysis shows the new method is an asymptotically optimal method. Simulation results show the new method possesses excellent properties, and is suitable for low SNR environment.
A new concept of time-frequency rate distribution is proposed. It can serve as an effective tool for superimposed LFM signal parameter estimation. A new method based on the time-frequency rate distribution is also proposed. Performance analysis shows the new method is an asymptotically optimal method. Simulation results show the new method possesses excellent properties, and is suitable for low SNR environment.
2007, 29(3): 635-638.
doi: 10.3724/SP.J.1146.2005.00685
Abstract:
In Orthogonal Frequency Division Multiplexing (OFDM) systems, to avoid influence of the low-pass filter on the transmitter side, some subcarriers on both edges of the allocated bandwidth are not used for transmission. These subcarriers are usually called virtual subcarriers which cause approach of conventional uniformly placed pilot tones inapplicable in some situations. Therefore, in this letter, based on nonuniform pilot tone placement, the optimal pilot sequences are derived, which can achieve the minimum mean square error of the least squares estimate for Multiple-Input Multiple-Output (MIMO) OFDM systems. Simulation results demonstrate the effectiveness of the proposed approach.
In Orthogonal Frequency Division Multiplexing (OFDM) systems, to avoid influence of the low-pass filter on the transmitter side, some subcarriers on both edges of the allocated bandwidth are not used for transmission. These subcarriers are usually called virtual subcarriers which cause approach of conventional uniformly placed pilot tones inapplicable in some situations. Therefore, in this letter, based on nonuniform pilot tone placement, the optimal pilot sequences are derived, which can achieve the minimum mean square error of the least squares estimate for Multiple-Input Multiple-Output (MIMO) OFDM systems. Simulation results demonstrate the effectiveness of the proposed approach.
2007, 29(3): 639-642.
doi: 10.3724/SP.J.1146.2006.00376
Abstract:
A Constant False Alarm Rate (CFAR) detector based on automatic censored algorithm in presence of reverberation is proposed in the paper. It automatically censors the interfering points in reference cells, so the limitation of method proposed by Barnard et al. (2004) can be overcomed. The analytic expressions of average false alarm and average detection probabilities are derived for the detector. Its superior performance is justified by processing of the simulation data and experimental data.
A Constant False Alarm Rate (CFAR) detector based on automatic censored algorithm in presence of reverberation is proposed in the paper. It automatically censors the interfering points in reference cells, so the limitation of method proposed by Barnard et al. (2004) can be overcomed. The analytic expressions of average false alarm and average detection probabilities are derived for the detector. Its superior performance is justified by processing of the simulation data and experimental data.
2007, 29(3): 643-647.
doi: 10.3724/SP.J.1146.2005.00787
Abstract:
In this paper, a new technique about long distance source localization with active and passive towed line array is presented. At first, a acoustic scattering field receiving equation for active and passive line array is derived. Then, this new method is described in detail that obtains a long distant azimuth, range and depth source localization by the normal-mode filter and the large synthetic aperture through horizontal moving of a short line array. The simulated results indicate that the estimation of accuracy in azimuth and range source localization is improved by this method. In addition, it is certificated that the active and passive line array can realize effectively long distant source localization by normal-mode filtering method.
In this paper, a new technique about long distance source localization with active and passive towed line array is presented. At first, a acoustic scattering field receiving equation for active and passive line array is derived. Then, this new method is described in detail that obtains a long distant azimuth, range and depth source localization by the normal-mode filter and the large synthetic aperture through horizontal moving of a short line array. The simulated results indicate that the estimation of accuracy in azimuth and range source localization is improved by this method. In addition, it is certificated that the active and passive line array can realize effectively long distant source localization by normal-mode filtering method.
2007, 29(3): 648-651.
doi: 10.3724/SP.J.1146.2005.01037
Abstract:
A binary tree scheme to construct Zero Correlation Window (ZCW) complementary codes is presented. The gap between the code number of the construction method and that of the theoretic bound is at most one when the code is long enough. In order to obtain more usable codes, a set of codes can be constructed through the direct product of the complementary code and an extend matrix. The correlation property of the code in one set lies on the extend matrix, nevertheless the ZCW still exists between any two codes in any different code sets.
A binary tree scheme to construct Zero Correlation Window (ZCW) complementary codes is presented. The gap between the code number of the construction method and that of the theoretic bound is at most one when the code is long enough. In order to obtain more usable codes, a set of codes can be constructed through the direct product of the complementary code and an extend matrix. The correlation property of the code in one set lies on the extend matrix, nevertheless the ZCW still exists between any two codes in any different code sets.
2007, 29(3): 652-656.
doi: 10.3724/SP.J.1146.2005.00970
Abstract:
For MIMO systems where channel state information is not acquired either at the receiver or at the transmitter, a novel family of full diversity unitary space-time block coding scheme is proposed in this paper, which combines Cayley transformation and the Diagonal Block Orthogonal Algebraic Space-Time (DBOAST) codes. The proposed space-time block codes can be applied to MIMO systems with even number of transmit antennas, which can achieve full transmit diversity and the rate of 1.5 symbol per channel use. The decoding of the proposed codes can be implemented by the sphere decoder at low computation complexity to achieve suboptimal results.
For MIMO systems where channel state information is not acquired either at the receiver or at the transmitter, a novel family of full diversity unitary space-time block coding scheme is proposed in this paper, which combines Cayley transformation and the Diagonal Block Orthogonal Algebraic Space-Time (DBOAST) codes. The proposed space-time block codes can be applied to MIMO systems with even number of transmit antennas, which can achieve full transmit diversity and the rate of 1.5 symbol per channel use. The decoding of the proposed codes can be implemented by the sphere decoder at low computation complexity to achieve suboptimal results.
2007, 29(3): 657-660.
doi: 10.3724/SP.J.1146.2005.00764
Abstract:
In this paper, the decoding algorithm of Low-Density Parity-Check (LDPC) codes is analyzed, and a new decoding algorithm based on the belief propagation (BP) algorithm to eliminate the influence of cycles in the factor graph is proposed. In the traditional BP algorithm, the cycles of factor graph will send message back to its source, and this will decrease the decoding performance. The new algorithm records each cycles path and length of each node, and cuts off the path by which message is propagated when the message will come back. It can advance the decoding performance by protect the message of good quality be propagated as widely as possible. The results of simulation show that the performance of new algorithm is not worse than that of traditional BP algorithm in the low SNR channel and the new algorithm significantly outperform traditional BP algorithm in good channel condition.
In this paper, the decoding algorithm of Low-Density Parity-Check (LDPC) codes is analyzed, and a new decoding algorithm based on the belief propagation (BP) algorithm to eliminate the influence of cycles in the factor graph is proposed. In the traditional BP algorithm, the cycles of factor graph will send message back to its source, and this will decrease the decoding performance. The new algorithm records each cycles path and length of each node, and cuts off the path by which message is propagated when the message will come back. It can advance the decoding performance by protect the message of good quality be propagated as widely as possible. The results of simulation show that the performance of new algorithm is not worse than that of traditional BP algorithm in the low SNR channel and the new algorithm significantly outperform traditional BP algorithm in good channel condition.
2007, 29(3): 661-665.
doi: 10.3724/SP.J.1146.2005.00668
Abstract:
A low complexity detection scheme for the MIMO system with distributed transmit antennas is presented. Based on a Sorted CHolesky Decomposition (SCHD), the additive gaussian color noise after match filter is whitened; The detection sequence according to the post signal noise ratio is reordered, and the risk of error propagation is degraded. The whole algorithm only requires one matrix inverse. Simulation results show that the presented algorithm has better performance and lower complexity compared to the existing detection scheme over Rayleigh fading channels.
A low complexity detection scheme for the MIMO system with distributed transmit antennas is presented. Based on a Sorted CHolesky Decomposition (SCHD), the additive gaussian color noise after match filter is whitened; The detection sequence according to the post signal noise ratio is reordered, and the risk of error propagation is degraded. The whole algorithm only requires one matrix inverse. Simulation results show that the presented algorithm has better performance and lower complexity compared to the existing detection scheme over Rayleigh fading channels.
2007, 29(3): 666-670.
doi: 10.3724/SP.J.1146.2005.00767
Abstract:
Space-Time Coding (STC) techniques, which combine antenna array signal processing and channel coding techniques, are very promising approaches to substantial capacity increase in wireless communications. In order to restrain the interference of co-channel users using Space-Time Block Coding (STBC), the anti-interference techniques is becoming a hot issue and the so-called turbo multi-user detection is applied in flat-fading channels. During iterations, extrinsic information is computed and exchanged between a soft decision multi-user detector (SDMUD) and a bank of turbo decoders, to achieve successively refined estimates of the users signals. The simulations show that the proposed iterative receiver provides significant performance improvement conventional noniterative methods around 2dB in both single-user and multi-user STBC systems. Furthermore, multi-user space-time processing techniques offer substantial performance gains by using more receive antennas.
Space-Time Coding (STC) techniques, which combine antenna array signal processing and channel coding techniques, are very promising approaches to substantial capacity increase in wireless communications. In order to restrain the interference of co-channel users using Space-Time Block Coding (STBC), the anti-interference techniques is becoming a hot issue and the so-called turbo multi-user detection is applied in flat-fading channels. During iterations, extrinsic information is computed and exchanged between a soft decision multi-user detector (SDMUD) and a bank of turbo decoders, to achieve successively refined estimates of the users signals. The simulations show that the proposed iterative receiver provides significant performance improvement conventional noniterative methods around 2dB in both single-user and multi-user STBC systems. Furthermore, multi-user space-time processing techniques offer substantial performance gains by using more receive antennas.
2007, 29(3): 671-673.
doi: 10.3724/SP.J.1146.2005.00696
Abstract:
A NLOS(Non Line Of Sight) high-resolution location algorithm is brought forward based on TOA(Time Of Arrival), AOA(Angle Of Arrival), which can be measured by two base station. The algorithm bases on the single reflect model, the simulation proves the algorithm validity in the NLOS scenarios.
A NLOS(Non Line Of Sight) high-resolution location algorithm is brought forward based on TOA(Time Of Arrival), AOA(Angle Of Arrival), which can be measured by two base station. The algorithm bases on the single reflect model, the simulation proves the algorithm validity in the NLOS scenarios.
2007, 29(3): 674-676.
doi: 10.3724/SP.J.1146.2005.00911
Abstract:
Considering the von Mises distribution as the received multipath power density distribution versus the AOA of scatter components, a formula for multipath angular spread corresponding to this distribution is presented in multi-antenna Rice channels, and an approximate expression for spatial correlation coefficient between compact antenna elements is proposed in small-scale Rice fading channels. The von Mises distributions concentration parameter makes a more visible impact on multipath angular spread than the Rice factor. It is concluded that spatial correlation between elements is weaker as long as multipath scattering is isotropic. It is also concluded that so far as multipath scattering is nonisotropic, the spatial correlation will acutely rises along with increasing of LOS power. The resulting analysis indicates that the angular spread and spacing between elements are main factors effecting on spatial fading correlation of received signals.
Considering the von Mises distribution as the received multipath power density distribution versus the AOA of scatter components, a formula for multipath angular spread corresponding to this distribution is presented in multi-antenna Rice channels, and an approximate expression for spatial correlation coefficient between compact antenna elements is proposed in small-scale Rice fading channels. The von Mises distributions concentration parameter makes a more visible impact on multipath angular spread than the Rice factor. It is concluded that spatial correlation between elements is weaker as long as multipath scattering is isotropic. It is also concluded that so far as multipath scattering is nonisotropic, the spatial correlation will acutely rises along with increasing of LOS power. The resulting analysis indicates that the angular spread and spacing between elements are main factors effecting on spatial fading correlation of received signals.
2007, 29(3): 677-680.
doi: 10.3724/SP.J.1146.2005.00780
Abstract:
Based on the Chaotic Pulse Position Modulation (CPPM) method, a novel communication scheme is proposed for Ultra-Wide Bandwidth Impulse radio Communication System (UWB-ICS) in this paper. The proposed scheme can overcome the disadvantages existing in CPPM, having the desired features of communication privacy, reliability and lower design complexity. It is shown by the analysis and simulation results that Chaotic Pulse On-Off-Keying (CPOOK) has better performance than CPPM in the case of non-ideal timing.
Based on the Chaotic Pulse Position Modulation (CPPM) method, a novel communication scheme is proposed for Ultra-Wide Bandwidth Impulse radio Communication System (UWB-ICS) in this paper. The proposed scheme can overcome the disadvantages existing in CPPM, having the desired features of communication privacy, reliability and lower design complexity. It is shown by the analysis and simulation results that Chaotic Pulse On-Off-Keying (CPOOK) has better performance than CPPM in the case of non-ideal timing.
2007, 29(3): 681-685.
doi: 10.3724/SP.J.1146.2005.00964
Abstract:
An optimal tradeoff formula between diversity gain and multiplexing gain was derived. The formula is a step decreasing and right continuous function，and the number of steps is equal to the number of receiving antennas. The diversity gain is relative to the block length, and can amount to the full diversity gain only when the block length is no less than the number of transmit antennas. The tradeoff shows that suitable space time codes would provide diversity gain and multiplexing gain simultaneously. However, two gains can not achieve the maximum level at the same time. By the tradeoff formula, the maximum diversity gain under a certain multiplexing gain can be estimated, and vice versa.
An optimal tradeoff formula between diversity gain and multiplexing gain was derived. The formula is a step decreasing and right continuous function，and the number of steps is equal to the number of receiving antennas. The diversity gain is relative to the block length, and can amount to the full diversity gain only when the block length is no less than the number of transmit antennas. The tradeoff shows that suitable space time codes would provide diversity gain and multiplexing gain simultaneously. However, two gains can not achieve the maximum level at the same time. By the tradeoff formula, the maximum diversity gain under a certain multiplexing gain can be estimated, and vice versa.
2007, 29(3): 686-689.
doi: 10.3724/SP.J.1146.2005.00928
Abstract:
Mean shift, an iterative procedure that shifts each data point to the average of data points in its neighborhood, has been applied to object tracking. However, with the changing structure of object in video sequences, traditional mean shift tracker by isotropic kernel often loses the object, especially when object structure varies fast. This paper implements object tracking with anisotropic kernel mean shift in which the shape, scale, and orientation of the kernels adapt to the changing object structure. The algorithm ensures tracking robust and real-time. Experimental results show it is effective.
Mean shift, an iterative procedure that shifts each data point to the average of data points in its neighborhood, has been applied to object tracking. However, with the changing structure of object in video sequences, traditional mean shift tracker by isotropic kernel often loses the object, especially when object structure varies fast. This paper implements object tracking with anisotropic kernel mean shift in which the shape, scale, and orientation of the kernels adapt to the changing object structure. The algorithm ensures tracking robust and real-time. Experimental results show it is effective.
2007, 29(3): 690-695.
doi: 10.3724/SP.J.1146.2005.01027
Abstract:
In multimedia conference, audio mixing is an essential component, which affects the communication between users. At present, the commonly used audio mixing algorithms have a protean volume. By analyzing those algorithms, the conclusion of mutative mixing weights bring on protean volume is drawn. Base on this, a novel algorithm named Asymmetrical Wave-Shrinking (AWS) is proposed. A fixed mixing weight independent of inputs is used to ensure the natural and fluent outputs without protean volume. Without multiplication and division operations, the algorithm is so simple and fast that it can be easily implemented by hardware and widely applied in large scale multimedia conference systems.
In multimedia conference, audio mixing is an essential component, which affects the communication between users. At present, the commonly used audio mixing algorithms have a protean volume. By analyzing those algorithms, the conclusion of mutative mixing weights bring on protean volume is drawn. Base on this, a novel algorithm named Asymmetrical Wave-Shrinking (AWS) is proposed. A fixed mixing weight independent of inputs is used to ensure the natural and fluent outputs without protean volume. Without multiplication and division operations, the algorithm is so simple and fast that it can be easily implemented by hardware and widely applied in large scale multimedia conference systems.
2007, 29(3): 696-698.
doi: 10.3724/SP.J.1146.2005.00773
Abstract:
In order to effectively reduce the effects of multi-access interference on the performance of optical code division multiple access (CDMA) communication systems with intensity modulation and direct detection，according to group information, a novel kind of multi-access interference cancellation scheme based on fiber Bragg grating(FBG)used with two dimensional address code MPC/OOC is presented. Considering the effects of multi-access interference, avalanche photodiode (APD) noise, and thermal noise, the performance of proposed optical CDMA communication systems is analyzed in detail. The result shows that this kind of multi-access interference cancellation scheme based on FBG can effectively reduce the influence of multi-access interference. And when received optical power is lager enough, the multi-access interference in two dimensional optical CDMA communication systems with MPC/OOC can be reduced completely.
In order to effectively reduce the effects of multi-access interference on the performance of optical code division multiple access (CDMA) communication systems with intensity modulation and direct detection，according to group information, a novel kind of multi-access interference cancellation scheme based on fiber Bragg grating(FBG)used with two dimensional address code MPC/OOC is presented. Considering the effects of multi-access interference, avalanche photodiode (APD) noise, and thermal noise, the performance of proposed optical CDMA communication systems is analyzed in detail. The result shows that this kind of multi-access interference cancellation scheme based on FBG can effectively reduce the influence of multi-access interference. And when received optical power is lager enough, the multi-access interference in two dimensional optical CDMA communication systems with MPC/OOC can be reduced completely.
2007, 29(3): 699-701.
doi: 10.3724/SP.J.1146.2005.00842
Abstract:
This paper discusses the reason of the security weakness of generalized state-space observers-based approaches for secure communication, using chaotic masking and chaotic nodulation of a Lorenz system and proposes a method to solve this problem. Theoretical analysis and simulation show this improvement realized chaotic masking. By comparison with the original system，this method improves the performance of secure communication system based on chaotic masking.
This paper discusses the reason of the security weakness of generalized state-space observers-based approaches for secure communication, using chaotic masking and chaotic nodulation of a Lorenz system and proposes a method to solve this problem. Theoretical analysis and simulation show this improvement realized chaotic masking. By comparison with the original system，this method improves the performance of secure communication system based on chaotic masking.
2007, 29(3): 702-706.
doi: 10.3724/SP.J.1146.2005.00667
Abstract:
To solve the QoS issue of the Internet including multi-services, a Priority-based Scheduling Structure (PSS) designed for high-speed packet networks is proposed. PSS divides packet scheduling into high-priority section and low-priority section. In the high-priority section, a sorted-priority algorithm with low implementation complexity is presented to avoid bandwidth preemption and to control effectively service rates of high-priority services. In the low-priority section, an improved framed-based algorithm is proposed, which decreases not only the algorithm complexity but also the hardware implementation cost. Computer simulation results as well as theoretic analysis show that the PSS mechanism has excellent performance in terms of the implementation complexity, fairness and delay properties.
To solve the QoS issue of the Internet including multi-services, a Priority-based Scheduling Structure (PSS) designed for high-speed packet networks is proposed. PSS divides packet scheduling into high-priority section and low-priority section. In the high-priority section, a sorted-priority algorithm with low implementation complexity is presented to avoid bandwidth preemption and to control effectively service rates of high-priority services. In the low-priority section, an improved framed-based algorithm is proposed, which decreases not only the algorithm complexity but also the hardware implementation cost. Computer simulation results as well as theoretic analysis show that the PSS mechanism has excellent performance in terms of the implementation complexity, fairness and delay properties.
2007, 29(3): 707-710.
doi: 10.3724/SP.J.1146.2005.00679
Abstract:
This paper adopted space restrain mechanism in the plain of network nodes due to the lower performance of connectivity in wireless cellular Ad hoc networks, and the total interference of the networks is decreased by considering location information and increasing the plain to lower the co-interference between the nodes. The broadcast success ratio is analyzed, the lower bound of the space location for the network nodes is computed and the efficiency of the network under single-flow and multi-flow environments is discussed separately. The simulation results show that the novel method can improve the performance of the networks significantly.
This paper adopted space restrain mechanism in the plain of network nodes due to the lower performance of connectivity in wireless cellular Ad hoc networks, and the total interference of the networks is decreased by considering location information and increasing the plain to lower the co-interference between the nodes. The broadcast success ratio is analyzed, the lower bound of the space location for the network nodes is computed and the efficiency of the network under single-flow and multi-flow environments is discussed separately. The simulation results show that the novel method can improve the performance of the networks significantly.
2007, 29(3): 711-715.
doi: 10.3724/SP.J.1146.2005.00849
Abstract:
Admission Control (AC) plays a significant role in providing the desired Quality of Service (QoS) in Broadband Wireless Access (BWA). In this paper, a unitive Utility-ratio based adaptive Admission Control algorithm (UAC) with probability and the Enhanced algorithm EUAC which simplify the computation complexity are presented for miscellaneous QoS definition in IEEE802.16 network, followed by their performance analysis. The simulation results demonstrate the adaptive algorithms can adaptively shift admission strategy base on current resources and system load, obviously and reasonably classify service flows by their utility-ratio. The simulation also illustrate adaptive algorithms have notable advantages in both throughput and utility. Furthermore, the algorithms rationally restrict the flows with lower utility-ratio to avoid degrading admitted flows with higher utility-ratio while holding high resource utilization.
Admission Control (AC) plays a significant role in providing the desired Quality of Service (QoS) in Broadband Wireless Access (BWA). In this paper, a unitive Utility-ratio based adaptive Admission Control algorithm (UAC) with probability and the Enhanced algorithm EUAC which simplify the computation complexity are presented for miscellaneous QoS definition in IEEE802.16 network, followed by their performance analysis. The simulation results demonstrate the adaptive algorithms can adaptively shift admission strategy base on current resources and system load, obviously and reasonably classify service flows by their utility-ratio. The simulation also illustrate adaptive algorithms have notable advantages in both throughput and utility. Furthermore, the algorithms rationally restrict the flows with lower utility-ratio to avoid degrading admitted flows with higher utility-ratio while holding high resource utilization.
2007, 29(3): 716-718.
doi: 10.3724/SP.J.1146.2005.00874
Abstract:
The minimum cost multicast tree may boil down to Steiner tree problem which is NP-Complete. In multicast applications, heuristic algorithms are commonly used to calculate the suboptimal tree. In this paper, a new heuristic algorithm named Shared Path First Heuristic (SPFH) is proposed. In this algorithm, when destination nodes are joined into the multicast tree, two factors are considered. One is the distance between the destination nodes and the multicast tree, the other is the influence of earlier joined nodes to the later joined nodes. Among the nearest nodes to the constructing multicast tree, the node which can reduce the joining cost of other nodes are first chosen to join the tree. The simulation result shows that SPFH achieves the preferable performance.
The minimum cost multicast tree may boil down to Steiner tree problem which is NP-Complete. In multicast applications, heuristic algorithms are commonly used to calculate the suboptimal tree. In this paper, a new heuristic algorithm named Shared Path First Heuristic (SPFH) is proposed. In this algorithm, when destination nodes are joined into the multicast tree, two factors are considered. One is the distance between the destination nodes and the multicast tree, the other is the influence of earlier joined nodes to the later joined nodes. Among the nearest nodes to the constructing multicast tree, the node which can reduce the joining cost of other nodes are first chosen to join the tree. The simulation result shows that SPFH achieves the preferable performance.
2007, 29(3): 719-724.
doi: 10.3724/SP.J.1146.2005.00949
Abstract:
To provide a higher QoS for Ad hoc network, this paper presents a Probability-based Detection Multi-Channel and Multi-Access(PDMCMA) protocol. It analyzes the systemic throughput of fixed occupation and sequent occupation system along with the result of throughput based on priority. The results show that the computer simulation is in concordance with the theoretical analysis.
To provide a higher QoS for Ad hoc network, this paper presents a Probability-based Detection Multi-Channel and Multi-Access(PDMCMA) protocol. It analyzes the systemic throughput of fixed occupation and sequent occupation system along with the result of throughput based on priority. The results show that the computer simulation is in concordance with the theoretical analysis.
2007, 29(3): 725-728.
doi: 10.3724/SP.J.1146.2005.01005
Abstract:
Traffic prediction is the core of network quality of service problems, such as traffic engineering and congestion control, etc. According to the characters of traffic, a novel network traffic prediction algorithm in which Kalman filter and wavelet are mixed is presented and proved abstractly. The simulation results show that the proposed algorithm can guarantee higher precision and better real-time processing compared with traditional algorithm.
Traffic prediction is the core of network quality of service problems, such as traffic engineering and congestion control, etc. According to the characters of traffic, a novel network traffic prediction algorithm in which Kalman filter and wavelet are mixed is presented and proved abstractly. The simulation results show that the proposed algorithm can guarantee higher precision and better real-time processing compared with traditional algorithm.
2007, 29(3): 729-732.
doi: 10.3724/SP.J.1146.2005.00930
Abstract:
Supporting fast restoration for general mesh topologies with minimal network over build is a technically challenging problem. In order to solve the problem of assigning minimum protection capacity, some ideal topologies are given and the algorithm of spanning tree construction is analyzed, and then an algorithm based on these is proposed to solve the problem of one link failure. Simulation results testify the new algorithm can reserve much smaller protection capacity compared with algorithm of spanning tree construction.
Supporting fast restoration for general mesh topologies with minimal network over build is a technically challenging problem. In order to solve the problem of assigning minimum protection capacity, some ideal topologies are given and the algorithm of spanning tree construction is analyzed, and then an algorithm based on these is proposed to solve the problem of one link failure. Simulation results testify the new algorithm can reserve much smaller protection capacity compared with algorithm of spanning tree construction.
2007, 29(3): 733-738.
doi: 10.3724/SP.J.1146.2005.01192
Abstract:
An autonomous negotiation model is proposed in allusion to the application of E-commerce. In this model, some vectors are employed to describe the formalization of negotiation issues; the two utility functions are defined to depict the utility evaluation mechanism; the Bayesian decision making is introduced to realize the self-learning of agent during negotiation; the traditional contract net protocol is extended to control orderly the two-sided negotiation interaction; and integrating with the agent self-learning, three kinds of proposal strategies are provided. As is testified by practice, the model turns out to be effective and practical.
An autonomous negotiation model is proposed in allusion to the application of E-commerce. In this model, some vectors are employed to describe the formalization of negotiation issues; the two utility functions are defined to depict the utility evaluation mechanism; the Bayesian decision making is introduced to realize the self-learning of agent during negotiation; the traditional contract net protocol is extended to control orderly the two-sided negotiation interaction; and integrating with the agent self-learning, three kinds of proposal strategies are provided. As is testified by practice, the model turns out to be effective and practical.
2007, 29(3): 739-742.
doi: 10.3724/SP.J.1146.2005.00677
Abstract:
In this paper, the model of limited radius, residual balanced multicast routing problem is improved. Considering the degree-constraints, minimal radius and load balance simultaneously, we present the concepts of deficient degree and the saturate degree of the nodes, and then propose subtle measurements on load balance in the multicast routing from two evaluation models: one is the evaluation model based on the variance of absolute deficient degree; and the other is the evaluation model based on the variance of relative deficient degree. An elaborately designed example manifests that the concepts and models are significant and practical.
In this paper, the model of limited radius, residual balanced multicast routing problem is improved. Considering the degree-constraints, minimal radius and load balance simultaneously, we present the concepts of deficient degree and the saturate degree of the nodes, and then propose subtle measurements on load balance in the multicast routing from two evaluation models: one is the evaluation model based on the variance of absolute deficient degree; and the other is the evaluation model based on the variance of relative deficient degree. An elaborately designed example manifests that the concepts and models are significant and practical.
2007, 29(3): 743-746.
doi: 10.3724/SP.J.1146.2005.01263
Abstract:
In this article, a novel Clock Feedthrough Frequency Compensation (CFFC) method based on the Minimum-Settling-Time (MST) theory and step-response analysis of a second order system is presented. Cadence ADE simulation results of a folded-cascode OTA with CFFC designed with SMIC 0.35m 2P3M Polyside Si CMOS models show that the settling time of the CFFC compensated cascode OTA is reduced by 22.7%, MST state is obtained as well. With the capacitor load varies from 0.5pF to 2.5pF, the settling time changes linearly from 3.62ns to 4.46ns, and the circuit achieves MST state at each load value. This method can be applied to high-speed active switched capacitor networks and its related fields.
In this article, a novel Clock Feedthrough Frequency Compensation (CFFC) method based on the Minimum-Settling-Time (MST) theory and step-response analysis of a second order system is presented. Cadence ADE simulation results of a folded-cascode OTA with CFFC designed with SMIC 0.35m 2P3M Polyside Si CMOS models show that the settling time of the CFFC compensated cascode OTA is reduced by 22.7%, MST state is obtained as well. With the capacitor load varies from 0.5pF to 2.5pF, the settling time changes linearly from 3.62ns to 4.46ns, and the circuit achieves MST state at each load value. This method can be applied to high-speed active switched capacitor networks and its related fields.
2007, 29(3): 747-750.
doi: 10.3724/SP.J.1146.2005.00699
Abstract:
Vector hydrophone can measure energy and particle velocity at a point in space with one sensor and can estimate the bearing of target. This paper , sound pressure gradient method and acoustic intensity method and apply genetic algorithm for acoustic intensity method bearing of target are analyzed. Instable signal and intercross steady signal for upper precision through construct adaptive function and process genetic selection with construct adaptive function are abnegated. The result of computer simulation indicates the algorithm can effectively bearing of target and enhance the precision of bearing.
Vector hydrophone can measure energy and particle velocity at a point in space with one sensor and can estimate the bearing of target. This paper , sound pressure gradient method and acoustic intensity method and apply genetic algorithm for acoustic intensity method bearing of target are analyzed. Instable signal and intercross steady signal for upper precision through construct adaptive function and process genetic selection with construct adaptive function are abnegated. The result of computer simulation indicates the algorithm can effectively bearing of target and enhance the precision of bearing.
2007, 29(3): 751-755.
doi: 10.3724/SP.J.1146.2005.00957
Abstract:
An improved method for evaluating the dispersion and coupling impedance of a tape helix is utilized. The assumption about the surface current density distribution on the tape is avoided by expanding it in a series of Chebyshev polynomials. The propagation matrix and jump matrix are introduced when the dielectric layer is stratified. A program has been written to analyze some typical examples. It is found that the results obtained by computing and measuring agree to good accuracy. The maximal orders of spatial harmonic and Chebyshev expansion can be specified to ensure the convergence of the results. The number of the stratified dielectric depends on the degree of radial uniformity: the more uniform the dielectric, the less the number.
An improved method for evaluating the dispersion and coupling impedance of a tape helix is utilized. The assumption about the surface current density distribution on the tape is avoided by expanding it in a series of Chebyshev polynomials. The propagation matrix and jump matrix are introduced when the dielectric layer is stratified. A program has been written to analyze some typical examples. It is found that the results obtained by computing and measuring agree to good accuracy. The maximal orders of spatial harmonic and Chebyshev expansion can be specified to ensure the convergence of the results. The number of the stratified dielectric depends on the degree of radial uniformity: the more uniform the dielectric, the less the number.
2007, 29(3): 756-759.
doi: 10.3724/SP.J.1146.2005.00990
Abstract:
A new two parameter CFAR detector in K-distribution clutter based on enhanced M-estimator and OSGO-CFAR detector is proposed in this paper. The performance of the detector is analyzed against uniform clutter background. Compared to OSGO with given shape parameter, the OSGO with shape parameter estimation has little additional detection loss against uniform clutter background, and has broad adaptation to K-distributed clutter.
A new two parameter CFAR detector in K-distribution clutter based on enhanced M-estimator and OSGO-CFAR detector is proposed in this paper. The performance of the detector is analyzed against uniform clutter background. Compared to OSGO with given shape parameter, the OSGO with shape parameter estimation has little additional detection loss against uniform clutter background, and has broad adaptation to K-distributed clutter.
2007, 29(3): 760-762.
doi: 10.3724/SP.J.1146.2005.01039
Abstract:
A novel method for n-order current-mode filters using the Current Differencing Buffered Amplifier(CDBA) is presented. Based on the signal-flow-graph a systematic design formula is given in this papers. As examples, a new fifth-order butterworth low-pass, high-pass and fourth-order band-pass filters are realized. Simulation results from PSPICE are obtained to verify the theoretical analysis. The proposed filters have the characteristic of simple structure and less number of components.
A novel method for n-order current-mode filters using the Current Differencing Buffered Amplifier(CDBA) is presented. Based on the signal-flow-graph a systematic design formula is given in this papers. As examples, a new fifth-order butterworth low-pass, high-pass and fourth-order band-pass filters are realized. Simulation results from PSPICE are obtained to verify the theoretical analysis. The proposed filters have the characteristic of simple structure and less number of components.
