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2009 Vol. 31, No. 3
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2009, 31(3): 509-513.
doi: 10.3724/SP.J.1146.2008.00557
Abstract:
The curse of high dimensionality is usually a major cause of limitations of many machine learning algorithms. A novel algorithm called Neighborhood Margin Fisher Discriminant Analysis (NMFDA) is proposed for supervised linear dimensionality reduction. For every point, NMFDA tries to enlarge the margin of the farthest point with the same class label and the nearest point with the different class label. Also the Kernel NMFDA is proposed for nonlinear dimensionality reduction. The contrastive experiments on several benchmark face database show the effectiveness of proposed method.
The curse of high dimensionality is usually a major cause of limitations of many machine learning algorithms. A novel algorithm called Neighborhood Margin Fisher Discriminant Analysis (NMFDA) is proposed for supervised linear dimensionality reduction. For every point, NMFDA tries to enlarge the margin of the farthest point with the same class label and the nearest point with the different class label. Also the Kernel NMFDA is proposed for nonlinear dimensionality reduction. The contrastive experiments on several benchmark face database show the effectiveness of proposed method.
2009, 31(3): 514-518.
doi: 10.3724/SP.J.1146.2007.01711
Abstract:
Support vector machine has been applied in many research fields, such as pattern recognition and function estimate. There is a shortcoming in Weighted SVM and Fuzzy SVM, which take the importance of sample into account but neglect the relative importance of each feature with respect to the classification task. In this paper a SVM approach is proposed based on the feature weighting, i.e. Feature Weighted SVM (FWSVM). This method first estimates the relative importance (weight) of each feature by computing the information gain. Then, it utilizes the weights for computing the inner product and Euclidean distance in kernel functions. In this way the computing of kernel function can avoid being dominated by trivial relevant or irrelevant features. Theoretical analysis and experimental results show that the FWSVM is more robust and has the better performance of generalization than the traditional SVM.
Support vector machine has been applied in many research fields, such as pattern recognition and function estimate. There is a shortcoming in Weighted SVM and Fuzzy SVM, which take the importance of sample into account but neglect the relative importance of each feature with respect to the classification task. In this paper a SVM approach is proposed based on the feature weighting, i.e. Feature Weighted SVM (FWSVM). This method first estimates the relative importance (weight) of each feature by computing the information gain. Then, it utilizes the weights for computing the inner product and Euclidean distance in kernel functions. In this way the computing of kernel function can avoid being dominated by trivial relevant or irrelevant features. Theoretical analysis and experimental results show that the FWSVM is more robust and has the better performance of generalization than the traditional SVM.
2009, 31(3): 519-522.
doi: 10.3724/SP.J.1146.2007.01593
Abstract:
Coalition generation is a key problem in multi-agent systems. Discrete particle swarm optimization is adopted to solve the problem, and random perturbation of particles is used to avoid premature convergence. A novel two-dimensional binary encoding is designed to realize complicated coalition parallel generation, and the operation of conflict resolution, feasibility checking, and compensation strategy are brought into effect to surmount the resource conflict and coalition lock in the course of problem solving. Finally, several typical simulation studies are carried out to illustrate its validity.
Coalition generation is a key problem in multi-agent systems. Discrete particle swarm optimization is adopted to solve the problem, and random perturbation of particles is used to avoid premature convergence. A novel two-dimensional binary encoding is designed to realize complicated coalition parallel generation, and the operation of conflict resolution, feasibility checking, and compensation strategy are brought into effect to surmount the resource conflict and coalition lock in the course of problem solving. Finally, several typical simulation studies are carried out to illustrate its validity.
2009, 31(3): 523-526.
doi: 10.3724/SP.J.1146.2007.01626
Abstract:
In this paper, a modified model of random walk is proposed, and then a clustering algorithm is developed based on this model. In the algorithm, at first a weighted and undirected graph G(V,E,d) is constructed among data points in a dataset according to the model, where each data point corresponds to a vertex in the graph, and is regarded as an agent who can move randomly in space. Next, the transition probabilities of data points are computed, and then each data point chooses a neighbor randomly in its neighborhood as a transition direction and takes a step to it. As all data points walk in space at random repeatedly, the data points that belong to the same class are located at a same position, whereas those that belong to different classes are away from one another. Consequently, the experimental results demonstrate that data points in datasets are clustered reasonably and efficiently. Moreover, the comparison with other algorithms also provides an indication of the effectiveness of the algorithm.
In this paper, a modified model of random walk is proposed, and then a clustering algorithm is developed based on this model. In the algorithm, at first a weighted and undirected graph G(V,E,d) is constructed among data points in a dataset according to the model, where each data point corresponds to a vertex in the graph, and is regarded as an agent who can move randomly in space. Next, the transition probabilities of data points are computed, and then each data point chooses a neighbor randomly in its neighborhood as a transition direction and takes a step to it. As all data points walk in space at random repeatedly, the data points that belong to the same class are located at a same position, whereas those that belong to different classes are away from one another. Consequently, the experimental results demonstrate that data points in datasets are clustered reasonably and efficiently. Moreover, the comparison with other algorithms also provides an indication of the effectiveness of the algorithm.
2009, 31(3): 527-531.
doi: 10.3724/SP.J.1146.2007.01621
Abstract:
A novel dimensionality reduction method called Local Marginal Discriminant Analysis (LMDA) is proposed in this paper based on spectral graph theory and manifold learning. Based on Neighborhood Preserving Projections (NPP), the reconstruction distortion in the intra-class caused by linear projections is minimized, and at the same time the integrity of the Laplacian matrix of the intra-class graph is kept, and margin between inter-class and intra-class is also maximized by constructing a weighted compactness nearest-neighbor graphs and a counterpart penalty graph. Finally, the numerical experimental results compared to other methods show that LMDA outperforms NPP.
A novel dimensionality reduction method called Local Marginal Discriminant Analysis (LMDA) is proposed in this paper based on spectral graph theory and manifold learning. Based on Neighborhood Preserving Projections (NPP), the reconstruction distortion in the intra-class caused by linear projections is minimized, and at the same time the integrity of the Laplacian matrix of the intra-class graph is kept, and margin between inter-class and intra-class is also maximized by constructing a weighted compactness nearest-neighbor graphs and a counterpart penalty graph. Finally, the numerical experimental results compared to other methods show that LMDA outperforms NPP.
2009, 31(3): 532-536.
doi: 10.3724/SP.J.1146.2007.01791
Abstract:
As the main prevailing denoising method, how the threshold function works and whats the threshold value are the greatest importance techniques. Consider the dependencies between the coefficients and their parents, a non-Gaussian bivariate distribution is given, and corresponding nonlinear threshold function is derived from the model using Bayesian estimation theory. According to non-subsampled Contourlet transform and bivariate threshold function, a novel Non-Subsampled Contourlet Transform based on Bivariate threshold function (NSCTBI) for image denoising is proposed. This scheme achieves enhanced estimation results for images that are corrupted with additive Gaussian noise over a wide range of noise variance. To evaluate the performance of the proposed algorithms, the results are compared with existent algorithms, such as non-subsampled Contourlet transform and wavelet-based bivariate threshold function method for image denoising. The simulation results indicate that the proposed method outperforms the others 0.5~2.3dB in PSNR, and keep better visual result in edges information reservation as well.
As the main prevailing denoising method, how the threshold function works and whats the threshold value are the greatest importance techniques. Consider the dependencies between the coefficients and their parents, a non-Gaussian bivariate distribution is given, and corresponding nonlinear threshold function is derived from the model using Bayesian estimation theory. According to non-subsampled Contourlet transform and bivariate threshold function, a novel Non-Subsampled Contourlet Transform based on Bivariate threshold function (NSCTBI) for image denoising is proposed. This scheme achieves enhanced estimation results for images that are corrupted with additive Gaussian noise over a wide range of noise variance. To evaluate the performance of the proposed algorithms, the results are compared with existent algorithms, such as non-subsampled Contourlet transform and wavelet-based bivariate threshold function method for image denoising. The simulation results indicate that the proposed method outperforms the others 0.5~2.3dB in PSNR, and keep better visual result in edges information reservation as well.
2009, 31(3): 537-541.
doi: 10.3724/SP.J.1146.2007.01702
Abstract:
In this paper Haar wavelet is used to construct the simulated natural terrain based on the FBM model and fractal features. Relations between fractal coefficients of truly terrains and wavelet decomposition coefficients of which are anlysised firstly, which help to set up the Haar wavelet-based terrain construction model. Then the fractal features are statisticed through coefficients in different wavelet decomposition levels of truly natural terrain. And subsequently, the simulated terrain is constructed reling on the fractal features, connected with the terrain construction model established. The algorithm has less computational complexity with low cross-entropy, and simulation experiments show the effective of the algorithm.
In this paper Haar wavelet is used to construct the simulated natural terrain based on the FBM model and fractal features. Relations between fractal coefficients of truly terrains and wavelet decomposition coefficients of which are anlysised firstly, which help to set up the Haar wavelet-based terrain construction model. Then the fractal features are statisticed through coefficients in different wavelet decomposition levels of truly natural terrain. And subsequently, the simulated terrain is constructed reling on the fractal features, connected with the terrain construction model established. The algorithm has less computational complexity with low cross-entropy, and simulation experiments show the effective of the algorithm.
2009, 31(3): 542-545.
doi: 10.3724/SP.J.1146.2007.01745
Abstract:
Registration of the consecutive frames is quite essential in dynamic video super resolution. In this paper, a multi-scale least square affine-based block-match method is proposed. An index Dmv is defined to evaluate global and local matching performances of the images. Then a multi-scale scheme is designed to adjust the block size automatically according to the motions between frames, which guaranteed well performances in both planar and un-planar regions. Different from the traditional block-match method, the affine-based least square estimation algorithm is introduced for registration of each pair of blocks. Convergence of the estimating process for different size of blocks is resolved by unification of the update step, which results in improvements in both estimating precision and speed. Finally, the proposed algorithm is evaluated in both the registration performance and its affects to the performance of the super resolution algorithm. Experimental results show that the proposed algorithm not only can provide more accurate motion estimation, when be applied to the Maximum A Posterior (MAP) based super resolution method, it shows obvious enhancement in both reconstruction performances and efficiencies.
Registration of the consecutive frames is quite essential in dynamic video super resolution. In this paper, a multi-scale least square affine-based block-match method is proposed. An index Dmv is defined to evaluate global and local matching performances of the images. Then a multi-scale scheme is designed to adjust the block size automatically according to the motions between frames, which guaranteed well performances in both planar and un-planar regions. Different from the traditional block-match method, the affine-based least square estimation algorithm is introduced for registration of each pair of blocks. Convergence of the estimating process for different size of blocks is resolved by unification of the update step, which results in improvements in both estimating precision and speed. Finally, the proposed algorithm is evaluated in both the registration performance and its affects to the performance of the super resolution algorithm. Experimental results show that the proposed algorithm not only can provide more accurate motion estimation, when be applied to the Maximum A Posterior (MAP) based super resolution method, it shows obvious enhancement in both reconstruction performances and efficiencies.
2009, 31(3): 546-551.
doi: 10.3724/SP.J.1146.2007.01569
Abstract:
The single watermark algorithms always merely have single function. In order to overcome the drawback, a multi-purpose dual watermark algorithm is proposed in the paper, taking advantage of the stability of singular values. It divides the original image into several blocks, and inserts robust watermark into their singular values. Then it inserts the fragile watermark into LSB in the space domain of previous watermarked image. Moreover, it designs a rule to distinguish malicious tamper from unintentional tamper. It tests not only robust watermarks robustness towards attacks, but also fragile watermarks influence towards robustness as well as the ability to tamper detection and localization. The experimental results show that the robust watermark possesses strong robustness to resist attacks, and that the fragile watermark is very sensitive to tamper and has good accuracy of tamper localization. Therefore it can achieve copyright protection and content authentication at the same time.
The single watermark algorithms always merely have single function. In order to overcome the drawback, a multi-purpose dual watermark algorithm is proposed in the paper, taking advantage of the stability of singular values. It divides the original image into several blocks, and inserts robust watermark into their singular values. Then it inserts the fragile watermark into LSB in the space domain of previous watermarked image. Moreover, it designs a rule to distinguish malicious tamper from unintentional tamper. It tests not only robust watermarks robustness towards attacks, but also fragile watermarks influence towards robustness as well as the ability to tamper detection and localization. The experimental results show that the robust watermark possesses strong robustness to resist attacks, and that the fragile watermark is very sensitive to tamper and has good accuracy of tamper localization. Therefore it can achieve copyright protection and content authentication at the same time.
2009, 31(3): 552-555.
doi: 10.3724/SP.J.1146.2007.01652
Abstract:
Quantization step is one of the key factors affecting the performances of quantization watermarking. In this paper, a new quantization watermarking algorithm is proposed using the JPEG quantization table to choose the quantization step of dither modulation adaptively, and another new adaptive quantization watermarking algorithm is proposed by combining the JPEG quantization table and the Watson model. Experimental results show that the proposed two algorithms are robust to noise and image transformations. Besides, the results also show that both the JPEG quantization table and the Watson model can be used to reduce the sensitivity of quantization watermarking to noise, and the best performance can be achieved when both of them are used.
Quantization step is one of the key factors affecting the performances of quantization watermarking. In this paper, a new quantization watermarking algorithm is proposed using the JPEG quantization table to choose the quantization step of dither modulation adaptively, and another new adaptive quantization watermarking algorithm is proposed by combining the JPEG quantization table and the Watson model. Experimental results show that the proposed two algorithms are robust to noise and image transformations. Besides, the results also show that both the JPEG quantization table and the Watson model can be used to reduce the sensitivity of quantization watermarking to noise, and the best performance can be achieved when both of them are used.
2009, 31(3): 556-560.
doi: 10.3724/SP.J.1146.2007.01530
Abstract:
For the multisensor linear discrete time-invariant stochastic control systems with correlated input and measurement white noises, and with correlated measurement white muses, a weighted measurement fusion steady-state Kalman filtering algorithm is presented by using the Weighted Least Squares(WLS)method. It can handle the fused filtering , smoothing and prediction problems for the state, white noise and signal. Based on the steady-state information filter, it is proved that it is completely functionally equivalent to the centralized measurement fusion steady-state Kalman filtering algorithm, so that it has asymptotic global optimality, and can reduced the computational burden. A simulation examples for tracking systems verifies its functional equivalence.
For the multisensor linear discrete time-invariant stochastic control systems with correlated input and measurement white noises, and with correlated measurement white muses, a weighted measurement fusion steady-state Kalman filtering algorithm is presented by using the Weighted Least Squares(WLS)method. It can handle the fused filtering , smoothing and prediction problems for the state, white noise and signal. Based on the steady-state information filter, it is proved that it is completely functionally equivalent to the centralized measurement fusion steady-state Kalman filtering algorithm, so that it has asymptotic global optimality, and can reduced the computational burden. A simulation examples for tracking systems verifies its functional equivalence.
2009, 31(3): 561-565.
doi: 10.3724/SP.J.1146.2007.01636
Abstract:
This paper proposes a new image denoising method based on the NonsubSampled Contourlet Transform(NSCT) and the bivariate model under the framework of Bayesian MAP estimation theory. The proposed algorithm uses the NSCTs advantages of translation-invariant and multidirection-selectivity, exploits the intra-scale and inter-scale correlations of NSCT coefficients, and elaborates the method of noise estimation. Compared with some current outstanding denoising methods, the simulation results and analysis show that the proposed algorithm obviously outperforms in both Peak Signal-to-Noise Ratio(PSNR) and visual quality, and effectively preserves detail and texture information of original images.
This paper proposes a new image denoising method based on the NonsubSampled Contourlet Transform(NSCT) and the bivariate model under the framework of Bayesian MAP estimation theory. The proposed algorithm uses the NSCTs advantages of translation-invariant and multidirection-selectivity, exploits the intra-scale and inter-scale correlations of NSCT coefficients, and elaborates the method of noise estimation. Compared with some current outstanding denoising methods, the simulation results and analysis show that the proposed algorithm obviously outperforms in both Peak Signal-to-Noise Ratio(PSNR) and visual quality, and effectively preserves detail and texture information of original images.
2009, 31(3): 566-569.
doi: 10.3724/SP.J.1146.2007.01792
Abstract:
A new algorithm is proposed for blind separation of two MPSK mixture signals obtained by a single- channel receiver. The proposed algorithm is based on optimal Bayesian Estimation criteria, and implemented via the particle filtering that is used to sequentially estimate the transmitted symbols and parameters. By over-sampling, more information of received signal waveform is utilized, so better noise suppression is achieved. Simulation results show that the proposed algorithm can obviously improve the Bit Error Rate (BER) performance in noise environment. The performance limit of the proposed algorithm is also analyzed from the perspective of Maximum Likelihood criteria.
A new algorithm is proposed for blind separation of two MPSK mixture signals obtained by a single- channel receiver. The proposed algorithm is based on optimal Bayesian Estimation criteria, and implemented via the particle filtering that is used to sequentially estimate the transmitted symbols and parameters. By over-sampling, more information of received signal waveform is utilized, so better noise suppression is achieved. Simulation results show that the proposed algorithm can obviously improve the Bit Error Rate (BER) performance in noise environment. The performance limit of the proposed algorithm is also analyzed from the perspective of Maximum Likelihood criteria.
2009, 31(3): 570-573.
doi: 10.3724/SP.J.1146.2007.01662
Abstract:
This paper mainly studies the sufficient necessary condition of linear separability and the essential of soft margin in SVM, which is used in target recognition. In this paper, the sufficient necessary condition of linear separability is proved using a brief and clear method, and also proved and explained the new essential of penalty factor in SVM.
This paper mainly studies the sufficient necessary condition of linear separability and the essential of soft margin in SVM, which is used in target recognition. In this paper, the sufficient necessary condition of linear separability is proved using a brief and clear method, and also proved and explained the new essential of penalty factor in SVM.
2009, 31(3): 574-577.
doi: 10.3724/SP.J.1146.2007.01796
Abstract:
A steering-invariant constant beamwidth beamforming algorithm is proposed. On the basis of main-lobe shape controlling idea, the proposed algorithm uses the main-lobe on some direction as reference main-lobe, and constructs the reference beampattern whose main-lobe direction is changed with different designed main-lobe direction by parallel moving the reference main-lobe, and keeps the height of side-lobe adjusted adaptively. Some virtual interfere sources are set on the look-in domain, the proposed algorithm adjusts the intension of them iteratively and makes the designed main-lobe on arbitrary direction inosculated the reference main-lobe, then the steering-invariant constant beamwidth beampattern is obtained after some iterative calculations. It is shown by simulation that the proposed algorithm can form the steering-invariant constant beamwidth beampattern effectively under the designed main-lobe direction of 60.
A steering-invariant constant beamwidth beamforming algorithm is proposed. On the basis of main-lobe shape controlling idea, the proposed algorithm uses the main-lobe on some direction as reference main-lobe, and constructs the reference beampattern whose main-lobe direction is changed with different designed main-lobe direction by parallel moving the reference main-lobe, and keeps the height of side-lobe adjusted adaptively. Some virtual interfere sources are set on the look-in domain, the proposed algorithm adjusts the intension of them iteratively and makes the designed main-lobe on arbitrary direction inosculated the reference main-lobe, then the steering-invariant constant beamwidth beampattern is obtained after some iterative calculations. It is shown by simulation that the proposed algorithm can form the steering-invariant constant beamwidth beampattern effectively under the designed main-lobe direction of 60.
2009, 31(3): 578-582.
doi: 10.3724/SP.J.1146.2007.01771
Abstract:
This paper proposes a new system based on DPCA technology for the detection and position of moving target, namely three antennae are placed at a slant angle along airplane flying detection. The echo model of moving target is established based on three channels with the slant-placed antennae in terms of the equivalent phase center principle. The analysis of the detection of moving target, MVD and blind velocity relative to the slant-placed antenna is given and the improved DPCA technology is presented for the detection, velocity meansure and position. Finally, the simulated data confirm this new system and the improved DPCA technology.
This paper proposes a new system based on DPCA technology for the detection and position of moving target, namely three antennae are placed at a slant angle along airplane flying detection. The echo model of moving target is established based on three channels with the slant-placed antennae in terms of the equivalent phase center principle. The analysis of the detection of moving target, MVD and blind velocity relative to the slant-placed antenna is given and the improved DPCA technology is presented for the detection, velocity meansure and position. Finally, the simulated data confirm this new system and the improved DPCA technology.
2009, 31(3): 583-587.
doi: 10.3724/SP.J.1146.2007.01808
Abstract:
Micro-dynamics characteristics are related to targets structures and can be used for target classification. Rotation structure of target is modeled as a sum of directional point scatterers. With the directional point scatter model, the micro-Doppler effect induced by rotation structure is analyzed. Then the joint time-frequency characteristics of radar echoes from targets which include rotation structure are investigated, and verified by real radar data. Finally, an extraction method of micro-motion characteristics, such as rotation frequency, is presented, and it is attempted to extract micro-dynamics characteristics, and the results are satisfactory.
Micro-dynamics characteristics are related to targets structures and can be used for target classification. Rotation structure of target is modeled as a sum of directional point scatterers. With the directional point scatter model, the micro-Doppler effect induced by rotation structure is analyzed. Then the joint time-frequency characteristics of radar echoes from targets which include rotation structure are investigated, and verified by real radar data. Finally, an extraction method of micro-motion characteristics, such as rotation frequency, is presented, and it is attempted to extract micro-dynamics characteristics, and the results are satisfactory.
2009, 31(3): 588-591.
doi: 10.3724/SP.J.1146.2007.01889
Abstract:
This paper presents a method for synthetic aperture radar images target recognition based on wavelet domain non-negative matrix factorization feature extraction. Low-frequency sub-band image is obtained by 2-D discrete wavelet decomposition of a SAR image. Non-negative matrix factorization is used for extracting feature vectors from the low-frequency sub-band image as the feature of the target. Support vector machine is used to perform target recognition. The method is applied for recognizing three-class targets in MSTAR database and the highest correct probability of recognition arrives at 97.51% which is enhanced obviously. It is concluded that the method proposed in this paper is an effective method for SAR images feature extraction and target recognition.
This paper presents a method for synthetic aperture radar images target recognition based on wavelet domain non-negative matrix factorization feature extraction. Low-frequency sub-band image is obtained by 2-D discrete wavelet decomposition of a SAR image. Non-negative matrix factorization is used for extracting feature vectors from the low-frequency sub-band image as the feature of the target. Support vector machine is used to perform target recognition. The method is applied for recognizing three-class targets in MSTAR database and the highest correct probability of recognition arrives at 97.51% which is enhanced obviously. It is concluded that the method proposed in this paper is an effective method for SAR images feature extraction and target recognition.
2009, 31(3): 592-595.
doi: 10.3724/SP.J.1146.2007.01664
Abstract:
According to Doppler centroid shift and Doppler spectrum split, this paper proposes an adaptive Doppler nonuniform bit allocation approach based on one dimension Look-Up Table (LUT). Combined with one dimension quantization and coding LUT this approach forms the adaptive compression algorithm in frequency domain. Meanwhile, this paper deduces the spectrum analytic function of the echo in range and provides with the general scheme for nonuniform compression ratio allocation. Numerical experiments results based on real SAR data show that new algorithm has higher SNR and better robustness than traditional frequency domain algorithms. Theoretical analysis shows that the calculation load is small and can be easily applied in engineering.
According to Doppler centroid shift and Doppler spectrum split, this paper proposes an adaptive Doppler nonuniform bit allocation approach based on one dimension Look-Up Table (LUT). Combined with one dimension quantization and coding LUT this approach forms the adaptive compression algorithm in frequency domain. Meanwhile, this paper deduces the spectrum analytic function of the echo in range and provides with the general scheme for nonuniform compression ratio allocation. Numerical experiments results based on real SAR data show that new algorithm has higher SNR and better robustness than traditional frequency domain algorithms. Theoretical analysis shows that the calculation load is small and can be easily applied in engineering.
2009, 31(3): 596-600.
doi: 10.3724/SP.J.1146.2007.01683
Abstract:
Based on the system characteristics of MIMO radar，two kinds of MIMO radar CFAR detectors(termed OSCA-CFAR and LCIOSCA-CFAR) based on order statistic and mean level are presented. Firstly, formulas of false alarm probability and detection probability are given. Then detection performance under various clutter background is compared with classic CA-CFAR by simulating and analyzing. The simulation results show that performance of OSCA-CFAR and LCIOSCA-CFAR has a low-loss under uniform clutter and is improved greatly under multi-target interference compared with the CA-CFAR. So it is more robust than the CA-CFAR in practice. Finally，advantage and disadvantage of the two kinds of CFAR detector are indicated．
Based on the system characteristics of MIMO radar，two kinds of MIMO radar CFAR detectors(termed OSCA-CFAR and LCIOSCA-CFAR) based on order statistic and mean level are presented. Firstly, formulas of false alarm probability and detection probability are given. Then detection performance under various clutter background is compared with classic CA-CFAR by simulating and analyzing. The simulation results show that performance of OSCA-CFAR and LCIOSCA-CFAR has a low-loss under uniform clutter and is improved greatly under multi-target interference compared with the CA-CFAR. So it is more robust than the CA-CFAR in practice. Finally，advantage and disadvantage of the two kinds of CFAR detector are indicated．
2009, 31(3): 601-605.
doi: 10.3724/SP.J.1146.2007.01655
Abstract:
The motion of the ballistic target in midcourse is very complex, which has high flight speed and micro-motion such as spin, precession and tumble. According to its complex motion, wideband radar echo model after dechirping is firstly built. Then the influence of the high speed motion and micro-motion on the High Resolution Range Profile (HRRP) of the ballistic target is quantitatively analyzed. In order to improve the quality of the ballistic targets HRRP, a new motion compensation algorithm is proposed. The basic idea is to estimate velocity through Doppler tracking to a scatter, and the Doppler tracking is performed via an Adaptive Joint Time-Frequency (AJTF) technique and Particle Swarm Optimization (PSO) algorithm. Simulations show that the distorted HRRP can be corrected effectively by the proposed method which has a high estimate accuracy, low computational cost and good robust property.
The motion of the ballistic target in midcourse is very complex, which has high flight speed and micro-motion such as spin, precession and tumble. According to its complex motion, wideband radar echo model after dechirping is firstly built. Then the influence of the high speed motion and micro-motion on the High Resolution Range Profile (HRRP) of the ballistic target is quantitatively analyzed. In order to improve the quality of the ballistic targets HRRP, a new motion compensation algorithm is proposed. The basic idea is to estimate velocity through Doppler tracking to a scatter, and the Doppler tracking is performed via an Adaptive Joint Time-Frequency (AJTF) technique and Particle Swarm Optimization (PSO) algorithm. Simulations show that the distorted HRRP can be corrected effectively by the proposed method which has a high estimate accuracy, low computational cost and good robust property.
2009, 31(3): 606-609.
doi: 10.3724/SP.J.1146.2007.01790
Abstract:
This paper mainly deals with the optimal inteferometric coherence of the residual images in frequency domain in detection and location of moving target with polarimetric SAR. The essential procedure of clutter cancellation in doppler frequency is presented. A novel method for improving the estimated accuracy of the motion parameters is proposed by taking the optimal polarimetric interferometry processing with residual images in frequency domain. Referring to the theory of optimal polarimetric interferometry, the interferometric coherences of the residual images with different polarization are analyzed. Simulation results show the effectiveness of proposed method.
This paper mainly deals with the optimal inteferometric coherence of the residual images in frequency domain in detection and location of moving target with polarimetric SAR. The essential procedure of clutter cancellation in doppler frequency is presented. A novel method for improving the estimated accuracy of the motion parameters is proposed by taking the optimal polarimetric interferometry processing with residual images in frequency domain. Referring to the theory of optimal polarimetric interferometry, the interferometric coherences of the residual images with different polarization are analyzed. Simulation results show the effectiveness of proposed method.
2009, 31(3): 610-613.
doi: 10.3724/SP.J.1146.2007.01885
Abstract:
Based on the character of SAR imaging procedure, this paper proposes a new passive SAR barrage jamming approach, utilizing the rotating angular reflectors. This method makes use of micro-Doppler modulation induced by rotating angle reflectors in order to form jamming strips along azimuth and arrays of rotating angle reflectors to interfere SAR imaging in the range direction. Then, the targets can be covered effectively. In addition, the selection of the key parameter of the rotating angular reflectors is discussed in detail, and then a project of reflectors array is proposed. The results for both simulated and experimental?data have proved the validity of this method.
Based on the character of SAR imaging procedure, this paper proposes a new passive SAR barrage jamming approach, utilizing the rotating angular reflectors. This method makes use of micro-Doppler modulation induced by rotating angle reflectors in order to form jamming strips along azimuth and arrays of rotating angle reflectors to interfere SAR imaging in the range direction. Then, the targets can be covered effectively. In addition, the selection of the key parameter of the rotating angular reflectors is discussed in detail, and then a project of reflectors array is proposed. The results for both simulated and experimental?data have proved the validity of this method.
2009, 31(3): 614-618.
doi: 10.3724/SP.J.1146.2007.01659
Abstract:
To calibrate the channel errors with gain and phase uncertainty for bistatic HF surface wave Synthesis Impulse and Aperture Radar (SIAR), a self-calibration approach for evaluating the gain-phase errors is presented in this paper. The impact of channel errors on spatial-temporal super-resolution is firstly analyzed. Using the direct wave of high Signal-to-Noise Ratio (SNR), the method conducts the estimation of the gain-phase matrix prior to that of range and angle, instead of the conventional joint-estimation. So the method has a small amount of computation and is easy to be implemented. Some influential factors are discussed as well in the paper. The numerical simulations show the validity of the proposed method.
To calibrate the channel errors with gain and phase uncertainty for bistatic HF surface wave Synthesis Impulse and Aperture Radar (SIAR), a self-calibration approach for evaluating the gain-phase errors is presented in this paper. The impact of channel errors on spatial-temporal super-resolution is firstly analyzed. Using the direct wave of high Signal-to-Noise Ratio (SNR), the method conducts the estimation of the gain-phase matrix prior to that of range and angle, instead of the conventional joint-estimation. So the method has a small amount of computation and is easy to be implemented. Some influential factors are discussed as well in the paper. The numerical simulations show the validity of the proposed method.
2009, 31(3): 619-622.
doi: 10.3724/SP.J.1146.2007.01642
Abstract:
When Ground Penetrating Radar is applied in actual projects, medium parameter (the permittivity is main) is a necessary data for users to position the depth of underground targets and the thickness of medium layers correctly. An inversion algorithm for underground medium parameter estimation based on MUSIC spectrum estimation is put forward in this paper. After estimating the time delay and amplitude of LFMCW GPR echo, the accurate medium parameter is worked out and then the right medium structure underground is gotten in succession. The simulating results show that the new algorithm improves much on the precision comparing with traditional electromagnetism inversion algorithms.
When Ground Penetrating Radar is applied in actual projects, medium parameter (the permittivity is main) is a necessary data for users to position the depth of underground targets and the thickness of medium layers correctly. An inversion algorithm for underground medium parameter estimation based on MUSIC spectrum estimation is put forward in this paper. After estimating the time delay and amplitude of LFMCW GPR echo, the accurate medium parameter is worked out and then the right medium structure underground is gotten in succession. The simulating results show that the new algorithm improves much on the precision comparing with traditional electromagnetism inversion algorithms.
2009, 31(3): 623-627.
doi: 10.3724/SP.J.1146.2007.01506
Abstract:
This paper analyzes the two scattering models and inversion techniques for bare soil surface, which were proposed by Oh(1992) and Dubois(1995), respectively. A method to validate the parameter inversion results of both two models was developed under the condition that no in-situ measurements were collected. Since Integral Equation Method (IEM) provides the relationship between backscattering coefficient and surface parameters in a rather wide range of roughness and moisture conditions, the modeling method of empirical and theoretical models are deeply analyzed and then combined. AIRSAR data are employed to perform the experiments, and the results show that the proposed method is effective to validate the surface parameters of bare soil which are obtained from the empirical models.
This paper analyzes the two scattering models and inversion techniques for bare soil surface, which were proposed by Oh(1992) and Dubois(1995), respectively. A method to validate the parameter inversion results of both two models was developed under the condition that no in-situ measurements were collected. Since Integral Equation Method (IEM) provides the relationship between backscattering coefficient and surface parameters in a rather wide range of roughness and moisture conditions, the modeling method of empirical and theoretical models are deeply analyzed and then combined. AIRSAR data are employed to perform the experiments, and the results show that the proposed method is effective to validate the surface parameters of bare soil which are obtained from the empirical models.
2009, 31(3): 628-631.
doi: 10.3724/SP.J.1146.2007.01807
Abstract:
The reflection coefficient of the receiver load of the feed system model for the cells in the active phased-array antenna is analyzed by S parameters. The scattering field of the active phased-array antenna is analyzed by submitting the reflection coefficient to the basic theoretical formula of the scattering fields of array antenna. The antenna model scattering of the active phased-array antenna is analyzed by dividing it into antenna model reflective scattering and antenna model phased scattering, and the analyzing results is testified by a one dimension array antenna, which plays a guidance role in the computation of the scattering fields of the phased array and its RCS control.
The reflection coefficient of the receiver load of the feed system model for the cells in the active phased-array antenna is analyzed by S parameters. The scattering field of the active phased-array antenna is analyzed by submitting the reflection coefficient to the basic theoretical formula of the scattering fields of array antenna. The antenna model scattering of the active phased-array antenna is analyzed by dividing it into antenna model reflective scattering and antenna model phased scattering, and the analyzing results is testified by a one dimension array antenna, which plays a guidance role in the computation of the scattering fields of the phased array and its RCS control.
2009, 31(3): 632-635.
doi: 10.3724/SP.J.1146.2007.01836
Abstract:
Through establishing structure model, the relation is presented among radiation power density of radiation source and effective permittivity and effective permeability. Simultaneously, the relations are numerically analyzed between radiation power density and permittivity, thickness, location of radiation source and operation frequency. The results show that radiation power density is directly proportional to the ratio of effective permittivity and effective permeability; relative low permittivity may remarkably improve radiation power density of radiation source; the maximum of radiation power density is the periodic function of thickness, and is less relation with the location of radiation source; the operation frequency band is very narrow in which the radiation power density can obtain larger values. The results may explain the reason theoretically that low permittivity metamaterials as a cover can enhance the gain of antenna.
Through establishing structure model, the relation is presented among radiation power density of radiation source and effective permittivity and effective permeability. Simultaneously, the relations are numerically analyzed between radiation power density and permittivity, thickness, location of radiation source and operation frequency. The results show that radiation power density is directly proportional to the ratio of effective permittivity and effective permeability; relative low permittivity may remarkably improve radiation power density of radiation source; the maximum of radiation power density is the periodic function of thickness, and is less relation with the location of radiation source; the operation frequency band is very narrow in which the radiation power density can obtain larger values. The results may explain the reason theoretically that low permittivity metamaterials as a cover can enhance the gain of antenna.
2009, 31(3): 636-639.
doi: 10.3724/SP.J.1146.2007.01876
Abstract:
For MIMO system, as an efficient algorithm to replace ML detection, Sphere Decoding (SD) can reduce the detection complexity greatly. Whereas the bad channel with large condition number still aggravates the computation complexity of SD. In this paper, the reason of this phenomenon is firstly analyzed. Secondly, an algorithm of combining weight at high layer is proposed for SD, aiming to reduce the probability of accessing into the high layer of the tree in the searching process of SD so as to decrease the complexity. The simulation results prove that the proposed algorithm can cut down the complexity distinctly, even to more than 20% at low SNR and high condition number.
For MIMO system, as an efficient algorithm to replace ML detection, Sphere Decoding (SD) can reduce the detection complexity greatly. Whereas the bad channel with large condition number still aggravates the computation complexity of SD. In this paper, the reason of this phenomenon is firstly analyzed. Secondly, an algorithm of combining weight at high layer is proposed for SD, aiming to reduce the probability of accessing into the high layer of the tree in the searching process of SD so as to decrease the complexity. The simulation results prove that the proposed algorithm can cut down the complexity distinctly, even to more than 20% at low SNR and high condition number.
2009, 31(3): 640-644.
doi: 10.3724/SP.J.1146.2007.01730
Abstract:
Performance of Discrete Fourier Transform (DFT) based channel estimation for Space Time Block Code-Orthogonal Frequency Division Multiplexing (STBC-OFDM) systems with virtual subcarriers is analyzed. The concise expressions for Mean Squared Error (MSE) and corresponding Bit Error Rate (BER) with the effect of virtual subcarriers are provided. Besides, a new channel estimation method based on zero-forcing is presented to eliminate aliasing distortion caused by virtual subcarriers. Simulation results demonstrate the accuracy of the analysis and the efficiency of new method.
Performance of Discrete Fourier Transform (DFT) based channel estimation for Space Time Block Code-Orthogonal Frequency Division Multiplexing (STBC-OFDM) systems with virtual subcarriers is analyzed. The concise expressions for Mean Squared Error (MSE) and corresponding Bit Error Rate (BER) with the effect of virtual subcarriers are provided. Besides, a new channel estimation method based on zero-forcing is presented to eliminate aliasing distortion caused by virtual subcarriers. Simulation results demonstrate the accuracy of the analysis and the efficiency of new method.
2009, 31(3): 645-648.
doi: 10.3724/SP.J.1146.2007.01658
Abstract:
A semi-blind multi-user constant modulus receiving system for downlink MIMO MC-CDMA system is proposed. The received signals are pre-processed before constant modulus detection, then the MIMO receiving system is transformed into several SISO receiving systems. The received signals are detected by SISO modulus algorithm. The improved method reduces the influence of multi-user interference and multi-path interference. It improves the detection performance obviously.
A semi-blind multi-user constant modulus receiving system for downlink MIMO MC-CDMA system is proposed. The received signals are pre-processed before constant modulus detection, then the MIMO receiving system is transformed into several SISO receiving systems. The received signals are detected by SISO modulus algorithm. The improved method reduces the influence of multi-user interference and multi-path interference. It improves the detection performance obviously.
2009, 31(3): 649-652.
doi: 10.3724/SP.J.1146.2007.01780
Abstract:
In order to tackle the inter-user interference issue of the limited feedback SDMA which uses a fixed number of active beams to simultaneously transmit signal, this paper proposes a novel limited feedback SDMA capable of adaptively selecting the optimal number of simultaneous beams, i.e., the optimal multiplexing order. In particular, the base station uses the feedback information from users and the spatial correlation matrix at the transmitter to ML estimate the maximum supported sum throughput for different number of active beams, thus the multiplexing order with the optimal performance can be chosen in each implementation of SDMA. Simulation results demonstrate that the proposed SDMA considerably outperforms the conventional SDMA in terms of throughput, with a small additional feedback overhead.
In order to tackle the inter-user interference issue of the limited feedback SDMA which uses a fixed number of active beams to simultaneously transmit signal, this paper proposes a novel limited feedback SDMA capable of adaptively selecting the optimal number of simultaneous beams, i.e., the optimal multiplexing order. In particular, the base station uses the feedback information from users and the spatial correlation matrix at the transmitter to ML estimate the maximum supported sum throughput for different number of active beams, thus the multiplexing order with the optimal performance can be chosen in each implementation of SDMA. Simulation results demonstrate that the proposed SDMA considerably outperforms the conventional SDMA in terms of throughput, with a small additional feedback overhead.
2009, 31(3): 653-656.
doi: 10.3724/SP.J.1146.2007.01862
Abstract:
For broadband OFDM systems, Doppler effect induced by high mobility gives rise to the InterCarrier Interference (ICI). By fully exploiting the ICI distribution property and partial channel information, two novel complexity-reduced Minimum Mean Square Error (MMSE) and Decision-Feedback Equalizer (DFE) are derived. Theoretical analysis and simulations illustrate that the new schemes provide a flexible and controllable approach to obtain the tradeoff between performance and complexity. When compared with existing schemes, the proposed DFE equalizer mitigates the error floor effect at the classical receiver and obtains performance improvement with the same computational overheads.
For broadband OFDM systems, Doppler effect induced by high mobility gives rise to the InterCarrier Interference (ICI). By fully exploiting the ICI distribution property and partial channel information, two novel complexity-reduced Minimum Mean Square Error (MMSE) and Decision-Feedback Equalizer (DFE) are derived. Theoretical analysis and simulations illustrate that the new schemes provide a flexible and controllable approach to obtain the tradeoff between performance and complexity. When compared with existing schemes, the proposed DFE equalizer mitigates the error floor effect at the classical receiver and obtains performance improvement with the same computational overheads.
2009, 31(3): 657-660.
doi: 10.3724/SP.J.1146.2007.01477
Abstract:
Traditional Tomlinson-Harashima Precoding (THP), which leaves all the equalization tasks to the transmitter, prevent from fully utilizing the advantages of MIMO techniques. In this paper, a THP scheme for multiuser MIMO system is proposed. The inter-user interference is preequalized at transmitter, while the intra-user interference is equalized at each receiver. Through block lower triangular decomposition of channel matrix and waterfilling under throughput maximization criterion, the proposed scheme achieves much better sum rate performance when compared to traditional THP designed for single antenna system.
Traditional Tomlinson-Harashima Precoding (THP), which leaves all the equalization tasks to the transmitter, prevent from fully utilizing the advantages of MIMO techniques. In this paper, a THP scheme for multiuser MIMO system is proposed. The inter-user interference is preequalized at transmitter, while the intra-user interference is equalized at each receiver. Through block lower triangular decomposition of channel matrix and waterfilling under throughput maximization criterion, the proposed scheme achieves much better sum rate performance when compared to traditional THP designed for single antenna system.
2009, 31(3): 661-665.
doi: 10.3724/SP.J.1146.2007.01742
Abstract:
In this paper, the relative content is researched for resolving the problem that a lot of wireless resource is expended by feedback information in MIMO-OFDM system. A novel algorithm including cluster, quantization and feedback is proposed. By utilizing the frequency correlation of the wireless channel, adjacent subcarriers are divided into several cluster and a cluster is seen as a feedback cell. Quantization is proposed by quantized values indicating the modulation level, because a discrete finite set of candidate constellation sizes is applied to practical systems. Finally, partial cluster quality information is transmitted to basestation through ordering and setting threshold. Theory deduction and simulation result show that the proposed algorithm needs only a little feedback information and has a trivial loss in terms of spectrum efficiency.
In this paper, the relative content is researched for resolving the problem that a lot of wireless resource is expended by feedback information in MIMO-OFDM system. A novel algorithm including cluster, quantization and feedback is proposed. By utilizing the frequency correlation of the wireless channel, adjacent subcarriers are divided into several cluster and a cluster is seen as a feedback cell. Quantization is proposed by quantized values indicating the modulation level, because a discrete finite set of candidate constellation sizes is applied to practical systems. Finally, partial cluster quality information is transmitted to basestation through ordering and setting threshold. Theory deduction and simulation result show that the proposed algorithm needs only a little feedback information and has a trivial loss in terms of spectrum efficiency.
2009, 31(3): 666-670.
doi: 10.3724/SP.J.1146.2007.01670
Abstract:
In this paper, a novel synchronization acquisition approach using the early-late gate for FFH/BFSK system is proposed, and it is based on frequency-PN sequence double pattern. Analytical and numerical results show the following advantages: the decision of threshold is more simple and accurate, and it overcomes the unreliableness of one-hop data demodulation, the unreliableness is caused by the not-alignment hop window of transmitter and receiver. The acquisition scheme can significantly improve the acquisition performance. When , where is the bit error rate and is the probability of synchronization acquisition. The analytical and numerical results are verified by a FFH testbed.
In this paper, a novel synchronization acquisition approach using the early-late gate for FFH/BFSK system is proposed, and it is based on frequency-PN sequence double pattern. Analytical and numerical results show the following advantages: the decision of threshold is more simple and accurate, and it overcomes the unreliableness of one-hop data demodulation, the unreliableness is caused by the not-alignment hop window of transmitter and receiver. The acquisition scheme can significantly improve the acquisition performance. When , where is the bit error rate and is the probability of synchronization acquisition. The analytical and numerical results are verified by a FFH testbed.
2009, 31(3): 671-674.
doi: 10.3724/SP.J.1146.2007.01647
Abstract:
In this paper, the generalized orthogonal sequences and N-shift partial length D0 orthogonal sequences with partial correlations are investigated. In particular, the partial correlation properties of Loosely Synchronized (LS) sequences are analyzed in details. The results show that LS sequences have partial correlation orthogonal property at 4-shift with half length, which can be utilized to construct partial length auto-complementary sequences and even-shift partial length cross-complementary sequences. Multiple-access interference can be eliminated in synchronous Code Division Multiple Access(CDMA) systems if the N-shift partial length D0 sequences are adopted.
In this paper, the generalized orthogonal sequences and N-shift partial length D0 orthogonal sequences with partial correlations are investigated. In particular, the partial correlation properties of Loosely Synchronized (LS) sequences are analyzed in details. The results show that LS sequences have partial correlation orthogonal property at 4-shift with half length, which can be utilized to construct partial length auto-complementary sequences and even-shift partial length cross-complementary sequences. Multiple-access interference can be eliminated in synchronous Code Division Multiple Access(CDMA) systems if the N-shift partial length D0 sequences are adopted.
2009, 31(3): 675-678.
doi: 10.3724/SP.J.1146.2007.01617
Abstract:
Cooperative diversity with multi-relay provides dramatic gains in slow fading wireless environments. In terms of average Symbol-Error Rate(SER) at the destination, the performances of multi-relay cooperative transmission with Maximal Ratio Combining(MRC) detection and opportunistic relaying with multi-node listening were analyzed, one relay retransmitting in Amplify-and-Forward(AF) networks under independent Rayleigh slow fading channels. The closed-form expressions of SER for M-PSK and M-QAM modulations are also derived based on Moment Generating Function(MGF). Monte Carlo simulation results show that all the SER formulas proposed are tight bounds particularly at medium and high SNR. Moreover, it can be seen that the opportunistic relaying, whose diversity gains are proportional to the number of cooperative listening nodes, and performs better in SER than multi-relay cooperation using MRC detection algorithm.
Cooperative diversity with multi-relay provides dramatic gains in slow fading wireless environments. In terms of average Symbol-Error Rate(SER) at the destination, the performances of multi-relay cooperative transmission with Maximal Ratio Combining(MRC) detection and opportunistic relaying with multi-node listening were analyzed, one relay retransmitting in Amplify-and-Forward(AF) networks under independent Rayleigh slow fading channels. The closed-form expressions of SER for M-PSK and M-QAM modulations are also derived based on Moment Generating Function(MGF). Monte Carlo simulation results show that all the SER formulas proposed are tight bounds particularly at medium and high SNR. Moreover, it can be seen that the opportunistic relaying, whose diversity gains are proportional to the number of cooperative listening nodes, and performs better in SER than multi-relay cooperation using MRC detection algorithm.
2009, 31(3): 679-683.
doi: 10.3724/SP.J.1146.2007.01774
Abstract:
In order to improve the wavelength utilization in WDM networks, multiple traffic connections can be allowed to share the capacity of a wavelength via TDM technology. The resultant network is a WDM-TDM optical network, where the Routing, Wavelength and Timeslot Assignment (RWTA) problem is the key for setting up traffic connections. In this paper, the dynamic RWTA problem is studied, a Most-Used Based RWTA algorithm (MUB) and an Enhanced MUB algorithm (EMUB) are proposed, and their performances are evaluated through computer simulation. The results show that the EMUB algorithm outperforms the MUB algorithm, and improves the resource utilization of WDM-TDM optical network.
In order to improve the wavelength utilization in WDM networks, multiple traffic connections can be allowed to share the capacity of a wavelength via TDM technology. The resultant network is a WDM-TDM optical network, where the Routing, Wavelength and Timeslot Assignment (RWTA) problem is the key for setting up traffic connections. In this paper, the dynamic RWTA problem is studied, a Most-Used Based RWTA algorithm (MUB) and an Enhanced MUB algorithm (EMUB) are proposed, and their performances are evaluated through computer simulation. The results show that the EMUB algorithm outperforms the MUB algorithm, and improves the resource utilization of WDM-TDM optical network.
A Subcarrier Grouping Approach and Detection for MIMO-OFDM Systems with GFDFR Space-Frequency Coding
2009, 31(3): 684-688.
doi: 10.3724/SP.J.1146.2007.00201
Abstract:
In this paper, a subcarrier grouping approach for Group-wise Full-Diversity Full-Rate (GFDFR) coded MIMO-OFDM systems with virtual and DC subcarriers is proposed. A PDA-SD hard detection algorithm and a neighbor searching soft detection algorithm, which all have low complexities, are presented to decode the GFDFR code. A one-dimensional neighbor searching detection algorithm, which is based on the hard detection algorithm and can effectively reduces the detection complexity, is proposed. Simulation results show that the subcarrier grouping approach is robust and insensitive to the numbers of virtual and DC subcarriers and all the detection algorithms have better bit-error rate performance.
In this paper, a subcarrier grouping approach for Group-wise Full-Diversity Full-Rate (GFDFR) coded MIMO-OFDM systems with virtual and DC subcarriers is proposed. A PDA-SD hard detection algorithm and a neighbor searching soft detection algorithm, which all have low complexities, are presented to decode the GFDFR code. A one-dimensional neighbor searching detection algorithm, which is based on the hard detection algorithm and can effectively reduces the detection complexity, is proposed. Simulation results show that the subcarrier grouping approach is robust and insensitive to the numbers of virtual and DC subcarriers and all the detection algorithms have better bit-error rate performance.
2009, 31(3): 689-693.
doi: 10.3724/SP.J.1146.2007.01794
Abstract:
In high speed wideband wireless communications, the duration of channels impulse response is about hundreds of symbol periods, which causes the convergence speed of linear blind equalizer to be much slower. Based on subband decomposition technique, a new structure and algorithm of the blind equalizer is proposed for high speed wideband wireless transmission. The proposed blind equalizer effectively combines the subband decomposition technique and sub-convolution method, and its convergence speed is faster than that of the traditional blind equalizer in high speed wideband transmission. On the other hand, since down-sampling and parallel processing of subband signals are used, the proposed structure possesses lower computational complexity, which is beneficial to its real-time realization in engineering applications. Computer simulations are presented to illustrate the efficiency of the new blind equalizer.
In high speed wideband wireless communications, the duration of channels impulse response is about hundreds of symbol periods, which causes the convergence speed of linear blind equalizer to be much slower. Based on subband decomposition technique, a new structure and algorithm of the blind equalizer is proposed for high speed wideband wireless transmission. The proposed blind equalizer effectively combines the subband decomposition technique and sub-convolution method, and its convergence speed is faster than that of the traditional blind equalizer in high speed wideband transmission. On the other hand, since down-sampling and parallel processing of subband signals are used, the proposed structure possesses lower computational complexity, which is beneficial to its real-time realization in engineering applications. Computer simulations are presented to illustrate the efficiency of the new blind equalizer.
2009, 31(3): 694-697.
doi: 10.3724/SP.J.1146.2007.01760
Abstract:
According to the reality that the need of users is becoming more and more diversified in telecommunication service field, the model of semantic Web services in Internet is tailored and a semantic Web services based intelligent telecommunication service model is proposed. In this model, the telecommunication service domain ontology base is designed to achieve knowledge sharing throughout telecommunication service field; the ontology based user personality database is put forward to sharpen the mining of user interests, taking advantage of natural reasoning feature of ontology; Intelligent agent is presented to liberate user from choosing the right service from huge amount of services. A module generating XSLT, the semantic transformation code, is constructed to increase the efficiency of describing semantic Web services. The model is verified in practical testing environment, and a multimedia service is presented to illustrate the working principle of the model in the end.
According to the reality that the need of users is becoming more and more diversified in telecommunication service field, the model of semantic Web services in Internet is tailored and a semantic Web services based intelligent telecommunication service model is proposed. In this model, the telecommunication service domain ontology base is designed to achieve knowledge sharing throughout telecommunication service field; the ontology based user personality database is put forward to sharpen the mining of user interests, taking advantage of natural reasoning feature of ontology; Intelligent agent is presented to liberate user from choosing the right service from huge amount of services. A module generating XSLT, the semantic transformation code, is constructed to increase the efficiency of describing semantic Web services. The model is verified in practical testing environment, and a multimedia service is presented to illustrate the working principle of the model in the end.
2009, 31(3): 698-701.
doi: 10.3724/SP.J.1146.2007.01668
Abstract:
The probability of packet delivered in Ad hoc network can be guaranteed by the multi-path scheme, with the analysis on the path numbers, the decision method based on packet drop rate is introduced; furthermore, the segment adaptive multi-path routing protocol is proposed. The mobile node estimates its status with the threshold pre-defined by monitoring the packet drop rate on the link, so the segmented multi-path can be established under current network topology, then the relay nodes can be selected adaptively. Simulations results show that the protocol can provide the reliable transmission for data packet while utilizing the network resource effectively.
The probability of packet delivered in Ad hoc network can be guaranteed by the multi-path scheme, with the analysis on the path numbers, the decision method based on packet drop rate is introduced; furthermore, the segment adaptive multi-path routing protocol is proposed. The mobile node estimates its status with the threshold pre-defined by monitoring the packet drop rate on the link, so the segmented multi-path can be established under current network topology, then the relay nodes can be selected adaptively. Simulations results show that the protocol can provide the reliable transmission for data packet while utilizing the network resource effectively.
2009, 31(3): 702-706.
doi: 10.3724/SP.J.1146.2007.01740
Abstract:
All nodes in Chord can be viewed as being placed into a one-dimensional ring. In this paper, a novel concept of bi-dimensional P2P is introduced for mobile Ad hoc networks, in which nodes are placed into a square, so that more than one configurable ring can be created, and redundant lookup routes can be provided. Based on the concept, the multi-ring bi-dimensional P2P lookup protocol family is proposed. Applicable ring-configuration examples are provided and the performances are analyzed. Simulation results prove the performance improvement of the protocol family compared with Chord like protocols.
All nodes in Chord can be viewed as being placed into a one-dimensional ring. In this paper, a novel concept of bi-dimensional P2P is introduced for mobile Ad hoc networks, in which nodes are placed into a square, so that more than one configurable ring can be created, and redundant lookup routes can be provided. Based on the concept, the multi-ring bi-dimensional P2P lookup protocol family is proposed. Applicable ring-configuration examples are provided and the performances are analyzed. Simulation results prove the performance improvement of the protocol family compared with Chord like protocols.
2009, 31(3): 707-710.
doi: 10.3724/SP.J.1146.2007.01681
Abstract:
Peer-to-Peer (P2P) overlays are appealing, since they can aggregate resources of end systems without relying on sophisticated infrastructures. Unfortunately current peer-to-peer systems either offer exact keyword match or provide inefficient text search methods through centralized indexing or flooding. In this paper, a semantic search system is proposed for structured P2P overlays without relying on message flooding. LSH is used to map semantically related text vector to nearly node, and a mechanism is carefully designed to cope with load balancing. Experimental results show that this is a steady system with high recall, good load balance.
Peer-to-Peer (P2P) overlays are appealing, since they can aggregate resources of end systems without relying on sophisticated infrastructures. Unfortunately current peer-to-peer systems either offer exact keyword match or provide inefficient text search methods through centralized indexing or flooding. In this paper, a semantic search system is proposed for structured P2P overlays without relying on message flooding. LSH is used to map semantically related text vector to nearly node, and a mechanism is carefully designed to cope with load balancing. Experimental results show that this is a steady system with high recall, good load balance.
2009, 31(3): 711-715.
doi: 10.3724/SP.J.1146.2008.00924
Abstract:
Service description language, metadata storage and service matching algorithm are three critical factors influencing the efficiency and quality of service discovery. This paper presents a prototype system of Chord-based semantic service discovery with QoS(Quality of Service). The information of QoS is put into OWL-S (Web ontology language for services) to describe services, and Chord-based distributed storage is adopted, and OWL-QoS based matching algorithm is used to discovery services. Experiment results show that the approach presented in this paper can improve the efficiency and accuracy of service discovery commendably.
Service description language, metadata storage and service matching algorithm are three critical factors influencing the efficiency and quality of service discovery. This paper presents a prototype system of Chord-based semantic service discovery with QoS(Quality of Service). The information of QoS is put into OWL-S (Web ontology language for services) to describe services, and Chord-based distributed storage is adopted, and OWL-QoS based matching algorithm is used to discovery services. Experiment results show that the approach presented in this paper can improve the efficiency and accuracy of service discovery commendably.
2009, 31(3): 716-721.
doi: 10.3724/SP.J.1146.2008.00054
Abstract:
Mobile Agent(MA) is more suitable for wireless sensor networks than the C/S model in data fusion. In MA based data fusion, the order of nodes visited along the route by MA has a significant impact on the algorithm efficiency and life time of wireless sensor networks. This paper proposes a Mobile Agent Data Fusion (MADF) algorithm based on bayes sequential estimation for wireless sensor networks. By designing data packet and data table with specific structure, and considers MA in multihop environments and adopts gradient of Bayes sequential estimation to dispatch MA. MA accounts for performing data processing and making data aggregation decisions at nodes rather than bring data back to a central processor (sink), redundant sensory data will be eliminated. Theoretical analysis and experimental results show that the proposed scheme is able to provide less energy consumption and network delay compared to directed diffusion schemes.
Mobile Agent(MA) is more suitable for wireless sensor networks than the C/S model in data fusion. In MA based data fusion, the order of nodes visited along the route by MA has a significant impact on the algorithm efficiency and life time of wireless sensor networks. This paper proposes a Mobile Agent Data Fusion (MADF) algorithm based on bayes sequential estimation for wireless sensor networks. By designing data packet and data table with specific structure, and considers MA in multihop environments and adopts gradient of Bayes sequential estimation to dispatch MA. MA accounts for performing data processing and making data aggregation decisions at nodes rather than bring data back to a central processor (sink), redundant sensory data will be eliminated. Theoretical analysis and experimental results show that the proposed scheme is able to provide less energy consumption and network delay compared to directed diffusion schemes.
2009, 31(3): 722-726.
doi: 10.3724/SP.J.1146.2007.01753
Abstract:
As RFID becomes more and more popular, it is imperative to design authentication protocols to resist all possible attacks and threats. In order to overcome counterfeits of readers, a new authentication protocol is proposed based on key array. The new protocol can deal with the synchronization of key update by adding flags of key update. It can resist several possible attacks, including reply, tracking, blocking, proofing and inner attacks. Compared with other authentication protocols, the new protocol can improve the security of RFID systems effectively and does not increase the complexity of protocol.
As RFID becomes more and more popular, it is imperative to design authentication protocols to resist all possible attacks and threats. In order to overcome counterfeits of readers, a new authentication protocol is proposed based on key array. The new protocol can deal with the synchronization of key update by adding flags of key update. It can resist several possible attacks, including reply, tracking, blocking, proofing and inner attacks. Compared with other authentication protocols, the new protocol can improve the security of RFID systems effectively and does not increase the complexity of protocol.
2009, 31(3): 727-730.
doi: 10.3724/SP.J.1146.2007.01693
Abstract:
-LFSR is a word-oriented feedback shift register with a good tradeoff between security and efficiency. As an example, using -LFSR in ABC increases its period from 232(2127-1) to 232(2128-1) and, more important, its Hamming weight with the feedback polynomial of equivalent LFSR over binary field from 3 to 65, which is just half of the degree 128. Consequently, its resistance to fast correlation attack is consolidated while the guaranteed efficiency in software is almost the same.
-LFSR is a word-oriented feedback shift register with a good tradeoff between security and efficiency. As an example, using -LFSR in ABC increases its period from 232(2127-1) to 232(2128-1) and, more important, its Hamming weight with the feedback polynomial of equivalent LFSR over binary field from 3 to 65, which is just half of the degree 128. Consequently, its resistance to fast correlation attack is consolidated while the guaranteed efficiency in software is almost the same.
2009, 31(3): 731-735.
doi: 10.3724/SP.J.1146.2007.01637
Abstract:
Motivated by an enormous amount of storage between DWT and EBCOT in JPEG2000 hardware implementation, a novel memory-efficient scheme based on code block size is proposed. Further reuse of on-chip code block size memories and efficient scheduling of them reduce hardware cost in both area and power. In the implementation, line-based lifting DWT architecture and bit plane parallel EBCOT design are used. The resulting coding efficiency is improved and the whole architecture can achieve real time processing. Experimental results show that on demand of real time coding, when a tile with resolution up to 512-width and 512-height is decomposed with four levels in 9/7 or 5/3 filters and the size of code block is 3232, the wavelet coefficients memory needed in the proposed architecture is reduced by over 80%, compared with existing architectures that wavelet coefficients are directly deposited in off-chip memories. The whole design has been synthesized and mapped into Xilinx FPGA, passing the verification when the system is working at the clock of 100MHz.
Motivated by an enormous amount of storage between DWT and EBCOT in JPEG2000 hardware implementation, a novel memory-efficient scheme based on code block size is proposed. Further reuse of on-chip code block size memories and efficient scheduling of them reduce hardware cost in both area and power. In the implementation, line-based lifting DWT architecture and bit plane parallel EBCOT design are used. The resulting coding efficiency is improved and the whole architecture can achieve real time processing. Experimental results show that on demand of real time coding, when a tile with resolution up to 512-width and 512-height is decomposed with four levels in 9/7 or 5/3 filters and the size of code block is 3232, the wavelet coefficients memory needed in the proposed architecture is reduced by over 80%, compared with existing architectures that wavelet coefficients are directly deposited in off-chip memories. The whole design has been synthesized and mapped into Xilinx FPGA, passing the verification when the system is working at the clock of 100MHz.
2009, 31(3): 736-739.
doi: 10.3724/SP.J.1146.2007.01761
Abstract:
The thermal statement of the helical slow wave structure is analyzed in detail in this paper, and an elliptical shell is firstly brought up to replace the conventional circle shell in the slow-wave structure. Then the 3D thermal analysis of the helical slow structure with elliptical shell is done with the help of ANSYS and the high-frequency characteristics simulation is also done with WMS CST. It is demonstrated that the ability of heat transfer of the helical slow structure with elliptical shell is much better than the conventional one and the more the support rods are, the better the heat transfer is. It is also found that the bandwidth of the elliptical shell is more wider than the circle one while the coupling impedance just decrease a little.
The thermal statement of the helical slow wave structure is analyzed in detail in this paper, and an elliptical shell is firstly brought up to replace the conventional circle shell in the slow-wave structure. Then the 3D thermal analysis of the helical slow structure with elliptical shell is done with the help of ANSYS and the high-frequency characteristics simulation is also done with WMS CST. It is demonstrated that the ability of heat transfer of the helical slow structure with elliptical shell is much better than the conventional one and the more the support rods are, the better the heat transfer is. It is also found that the bandwidth of the elliptical shell is more wider than the circle one while the coupling impedance just decrease a little.
2009, 31(3): 745-748.
doi: 10.3724/SP.J.1146.2007.01645
Abstract:
A novel MRF model called SPMRF (Structure Preserving MRF) is proposed for Bayesian despeckling of SAR images. In SPMRF every pixel within a neighborhood is associated with a weighting parameter which determines its contribution to the central pixels despeckling. And a temperature variable is introduced into SPMRF to control the weighting parameters estimating process which makes the model match with images local characteristics better. Experiments show as a prior model SPMRF can retain image structures efficiently with despeckling progressing.
A novel MRF model called SPMRF (Structure Preserving MRF) is proposed for Bayesian despeckling of SAR images. In SPMRF every pixel within a neighborhood is associated with a weighting parameter which determines its contribution to the central pixels despeckling. And a temperature variable is introduced into SPMRF to control the weighting parameters estimating process which makes the model match with images local characteristics better. Experiments show as a prior model SPMRF can retain image structures efficiently with despeckling progressing.
2009, 31(3): 749-751.
doi: 10.3724/SP.J.1146.2007.01835
Abstract:
In this article, an ultra-high speed SAR raw data recorder based on disk array is introduced, including its construct, working principle, and main features. Two kinds of data packet allocating method are proposed: the sequential allocating method and a dynamic allocating method based on statistical characteristics of the recording ability of each disk, also, the advantages and disadvantages of each method are pointed out. The performance table of two methods is put forward at the end of this article.
In this article, an ultra-high speed SAR raw data recorder based on disk array is introduced, including its construct, working principle, and main features. Two kinds of data packet allocating method are proposed: the sequential allocating method and a dynamic allocating method based on statistical characteristics of the recording ability of each disk, also, the advantages and disadvantages of each method are pointed out. The performance table of two methods is put forward at the end of this article.
2009, 31(3): 752-755.
doi: 10.3724/SP.J.1146.2007.01732
Abstract:
In this paper, a new transmit beamforming scheme with limited feedback is presented in Multiple-Input Single-Output Orthogonal Frequency Division Multiplexing (MISO-OFDM) systems. By dividing the total subcarriers of an OFDM symbol into a series of clusters, from the codebook a proper one minimizing the average Bit Error Rate (BER) per subcarrier of the considered cluster is chosen as the beamforming vector for this cluster. The scheme can reduce the feedback overhead remarkably while obtain good BER performance. Additionally, a simple sub-optimal algorithm based on the correlation of subcarriers is proposed to avoid exhaustive search in the optimal solution. The simulation results show that the proposed algorithm, with low computational complexity, provides improvement over existing schemes.
In this paper, a new transmit beamforming scheme with limited feedback is presented in Multiple-Input Single-Output Orthogonal Frequency Division Multiplexing (MISO-OFDM) systems. By dividing the total subcarriers of an OFDM symbol into a series of clusters, from the codebook a proper one minimizing the average Bit Error Rate (BER) per subcarrier of the considered cluster is chosen as the beamforming vector for this cluster. The scheme can reduce the feedback overhead remarkably while obtain good BER performance. Additionally, a simple sub-optimal algorithm based on the correlation of subcarriers is proposed to avoid exhaustive search in the optimal solution. The simulation results show that the proposed algorithm, with low computational complexity, provides improvement over existing schemes.
2009, 31(3): 756-758.
doi: 10.3724/SP.J.1146.2007.01649
Abstract:
The common multiple-access schemes for Differential Chaos Shift Keying (DCSK) system have two disadvantages. Firstly, all users share the same slot, only method to decrease multiple-access interference is utilizing the low correlativity of chaotic signal. Secondly, the transmitted signals for reference and symbol are not same or reverse, so the strong anti-multipath character is destroyed. A novel time-hopping multiple-access scheme for DCSK system is put forward. It assigns different PN time-hopping codes to different users. The signals for reference and symbol in a frame have the same time-hopping value. In AWGN channel the systems bit error rate is obtained in theory. Analysis and simulation show that time-hopping multiple-access scheme can overcome above two disadvantages and has lower bit error rate.
The common multiple-access schemes for Differential Chaos Shift Keying (DCSK) system have two disadvantages. Firstly, all users share the same slot, only method to decrease multiple-access interference is utilizing the low correlativity of chaotic signal. Secondly, the transmitted signals for reference and symbol are not same or reverse, so the strong anti-multipath character is destroyed. A novel time-hopping multiple-access scheme for DCSK system is put forward. It assigns different PN time-hopping codes to different users. The signals for reference and symbol in a frame have the same time-hopping value. In AWGN channel the systems bit error rate is obtained in theory. Analysis and simulation show that time-hopping multiple-access scheme can overcome above two disadvantages and has lower bit error rate.
2009, 31(3): 759-762.
doi: 10.3724/SP.J.1146.2008.00301
Abstract:
Identifying video stream quickly from the network flow is the foundation and prerequisite of network video surveillance and management. According to the analysis of characteristics of network video streams, a fast recognition and classification algorithm of network video stream based on multiple pattern matching is proposed, which constructs the matching machine with the features of different video streams. The proposed algorithm could determine whether the network packet contains video stream and type only by one incomplete scan. The experimental results show that the proposed algorithm has higher efficiency than traditional protocol analysis method under the requirement of accuracy.
Identifying video stream quickly from the network flow is the foundation and prerequisite of network video surveillance and management. According to the analysis of characteristics of network video streams, a fast recognition and classification algorithm of network video stream based on multiple pattern matching is proposed, which constructs the matching machine with the features of different video streams. The proposed algorithm could determine whether the network packet contains video stream and type only by one incomplete scan. The experimental results show that the proposed algorithm has higher efficiency than traditional protocol analysis method under the requirement of accuracy.
2009, 31(3): 740-744.
doi: 10.3724/SP.J.1146.2007.01562
Abstract:
Wang et al. (2005) proposed a collision attack on MD5 and gave a set of sufficient conditions to yield a MD5 collision. Yuto Nakano et al. (2006) pointed out that there were 16 redundant conditions in Wang et al.s set of sufficient conditions and explained why 14 out of them were redundant. This paper will propose that two of them are not redundant actually and present two new redundant conditions in the set of sufficient conditions presented by Liang Jie and Lai Xuejia in 2005. Additionally, it will show that there is a mistake in Liang Jie and Lai Xuejias collision attack algorithm for the second-block message because they do not consider the dependence in the sufficient conditions, and correct the mistake. Finally, a new set of sufficient conditions is obtained and it could always yield a MD5 collision according to computer simulations.
Wang et al. (2005) proposed a collision attack on MD5 and gave a set of sufficient conditions to yield a MD5 collision. Yuto Nakano et al. (2006) pointed out that there were 16 redundant conditions in Wang et al.s set of sufficient conditions and explained why 14 out of them were redundant. This paper will propose that two of them are not redundant actually and present two new redundant conditions in the set of sufficient conditions presented by Liang Jie and Lai Xuejia in 2005. Additionally, it will show that there is a mistake in Liang Jie and Lai Xuejias collision attack algorithm for the second-block message because they do not consider the dependence in the sufficient conditions, and correct the mistake. Finally, a new set of sufficient conditions is obtained and it could always yield a MD5 collision according to computer simulations.
