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2007 Vol. 29, No. 1
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2007, 29(1): 1-5.
doi: 10.3724/SP.J.1146.2005.00590
Abstract:
Based on the principles of ISAR and interferometric observation, a three-dimensional (3D) imaging method of Interferometric ISAR (InISAR) is developed. Making use of compensation of the resultant angular motion parameters for the echoes in the raw data level, two complex images from interferometric antennas are, sequentially, co-registered. A 3D image of a moving target is reconstructed from the spatial coordinates of these scatter centers of the target. Also, a stretch processing of LFM signal to remove the background clutter is discussed. This method is simple and easily implemented in engineering. Simulations show that this 3D imaging method works well even for a moving target in strong clutters.
Based on the principles of ISAR and interferometric observation, a three-dimensional (3D) imaging method of Interferometric ISAR (InISAR) is developed. Making use of compensation of the resultant angular motion parameters for the echoes in the raw data level, two complex images from interferometric antennas are, sequentially, co-registered. A 3D image of a moving target is reconstructed from the spatial coordinates of these scatter centers of the target. Also, a stretch processing of LFM signal to remove the background clutter is discussed. This method is simple and easily implemented in engineering. Simulations show that this 3D imaging method works well even for a moving target in strong clutters.
2007, 29(1): 6-11.
doi: 10.3724/SP.J.1146.2005.00634
Abstract:
In this paper the two-dimensional frequency expression of SAR echoes are first analyzed. Then, the standard chirp scaling algorithm and its several modified forms used both in high frequency narrow band SAR and low frequency Ultra WideBand (UWB) SAR are compared in a united frame of two-dimensional frequency expression. The approximations made by different algorithms are evaluated in detail. So a new depiction for SAR image formation is proposed, which is a process of constructing phase compensating factors in frequency or time domain according to the characteristics of echo spectrum. Especially, the accuracy of phase compensating factors for UWB SAR echoes has a direct impact on point targets focusing. Simulation results verify that the modified non-linear chirp scaling algorithm, which can compensate the more third orders phase coupling, can arrive an ideal focusing UWB SAR image in the certain of scope. Further more, the algorithm has been used successfully in raw UWB SAR data processing.
In this paper the two-dimensional frequency expression of SAR echoes are first analyzed. Then, the standard chirp scaling algorithm and its several modified forms used both in high frequency narrow band SAR and low frequency Ultra WideBand (UWB) SAR are compared in a united frame of two-dimensional frequency expression. The approximations made by different algorithms are evaluated in detail. So a new depiction for SAR image formation is proposed, which is a process of constructing phase compensating factors in frequency or time domain according to the characteristics of echo spectrum. Especially, the accuracy of phase compensating factors for UWB SAR echoes has a direct impact on point targets focusing. Simulation results verify that the modified non-linear chirp scaling algorithm, which can compensate the more third orders phase coupling, can arrive an ideal focusing UWB SAR image in the certain of scope. Further more, the algorithm has been used successfully in raw UWB SAR data processing.
2007, 29(1): 12-14.
doi: 10.3724/SP.J.1146.2005.00649
Abstract:
Minimum Total Variation Autofocus (MTVA) algorithm for SAR imaging is studied. Firstly, the relationship between total variation of SAR image and 2nd-order phase error is analyzed. The results show that total variation is a single peak function of 2nd-order phase error. Total variation reaches minimum when zero phase error. Then total variation norm is used as performance function. Golden selection method is adopted to get focused SAR image. Finally, experimental results show that MTVA algorithm has good performance and is better than Phase Gradient Autofocus (PGA) algorithm. Study of complexity shows that MTVAs computation amount is nearly half of PGAs.
Minimum Total Variation Autofocus (MTVA) algorithm for SAR imaging is studied. Firstly, the relationship between total variation of SAR image and 2nd-order phase error is analyzed. The results show that total variation is a single peak function of 2nd-order phase error. Total variation reaches minimum when zero phase error. Then total variation norm is used as performance function. Golden selection method is adopted to get focused SAR image. Finally, experimental results show that MTVA algorithm has good performance and is better than Phase Gradient Autofocus (PGA) algorithm. Study of complexity shows that MTVAs computation amount is nearly half of PGAs.
2007, 29(1): 15-18.
doi: 10.3724/SP.J.1146.2005.00442
Abstract:
The passive distributed microsatellites Synthetic Aperture Radar(SAR) system has the capabilities in improving image resolution, detecting ground moving targets and computing digital elevation models. But the input Signal-to-Noise Ratio (SNR) of the system will largely reduce compared with the active spaceborne radar because of the decrease of its receiving antennas area, which will degrade the performance of the system. This paper analyses the effect of the SNRs reduction on SAR imagery, Digital Elevation Model (DEM) and Ground Moving Target Indication (GMTI), based on the JERS-1 acted as the active satellite, and comes to a conclusion that the SNR obtained from the system would be lower than what the system required. Some methods to improve the systems output SNR by coherent or noncoherent operating are also discussed.
The passive distributed microsatellites Synthetic Aperture Radar(SAR) system has the capabilities in improving image resolution, detecting ground moving targets and computing digital elevation models. But the input Signal-to-Noise Ratio (SNR) of the system will largely reduce compared with the active spaceborne radar because of the decrease of its receiving antennas area, which will degrade the performance of the system. This paper analyses the effect of the SNRs reduction on SAR imagery, Digital Elevation Model (DEM) and Ground Moving Target Indication (GMTI), based on the JERS-1 acted as the active satellite, and comes to a conclusion that the SNR obtained from the system would be lower than what the system required. Some methods to improve the systems output SNR by coherent or noncoherent operating are also discussed.
2007, 29(1): 19-22.
doi: 10.3724/SP.J.1146.2005.00269
Abstract:
In this paper, a GMTI method for -beams is investigated, which is achieved by incorporating the along-track interferometric SAR/ GMTI technique with signal subspace processing. The principle of along-track interferometric SAR/ GMTI is analyzed, and the spatial cancellation matrix used to preprocess the image is derived. In practice, because of the channel errors (gain and phase error), a two-dimensional signal subspace processing method is used, which can blindly calibrate the sensors error and achieve the moving targets detection. The simulation results are presented to demonstrate the validity of this scheme.
In this paper, a GMTI method for -beams is investigated, which is achieved by incorporating the along-track interferometric SAR/ GMTI technique with signal subspace processing. The principle of along-track interferometric SAR/ GMTI is analyzed, and the spatial cancellation matrix used to preprocess the image is derived. In practice, because of the channel errors (gain and phase error), a two-dimensional signal subspace processing method is used, which can blindly calibrate the sensors error and achieve the moving targets detection. The simulation results are presented to demonstrate the validity of this scheme.
Parameters estimation of Wideband/ Ultra-Wideband LFM Signal Based on Spectrum Compressing Receiving
2007, 29(1): 23-25.
doi: 10.3724/SP.J.1146.2005.00398
Abstract:
An new method, which compresses the spectrum of the wideband / ultra -wideband LFM signal in radio channel to turn the wideband/ ultra -wideband signal into the narrowband signal, is presented in this paper. Using the inverse compression function, the compressed signal is reconstructed by nonlinear interpolation in digital domain. Moreover, the modulation slope and initial frequency of the original signal can still be estimated from the reconstructed LFM signal precisely. Computer simulation shows its validity.
An new method, which compresses the spectrum of the wideband / ultra -wideband LFM signal in radio channel to turn the wideband/ ultra -wideband signal into the narrowband signal, is presented in this paper. Using the inverse compression function, the compressed signal is reconstructed by nonlinear interpolation in digital domain. Moreover, the modulation slope and initial frequency of the original signal can still be estimated from the reconstructed LFM signal precisely. Computer simulation shows its validity.
2007, 29(1): 26-29.
doi: 10.3724/SP.J.1146.2005.00585
Abstract:
Sliding spotlight SAR is a novel mode of SAR imaging, which can improve azimuth resolution by controlling the speed of antenna footprint to increase coherent accumulation time. This paper analyzes the sliding-spotlight mode at the aspects of imaging principle, echo model, resolution, antenna operational mode, swath width, etc. And it presents the wavenumber domain algorithm of sliding-spotlight SAR. Compared with stripmap and spotlight SAR imaging, both stripmap and spotlight are special forms of sliding-spotlight mode.
Sliding spotlight SAR is a novel mode of SAR imaging, which can improve azimuth resolution by controlling the speed of antenna footprint to increase coherent accumulation time. This paper analyzes the sliding-spotlight mode at the aspects of imaging principle, echo model, resolution, antenna operational mode, swath width, etc. And it presents the wavenumber domain algorithm of sliding-spotlight SAR. Compared with stripmap and spotlight SAR imaging, both stripmap and spotlight are special forms of sliding-spotlight mode.
2007, 29(1): 30-34.
doi: 10.3724/SP.J.1146.2005.00635
Abstract:
A new method for unsupervised classification of terrain types using fully POLarimetric Synthetic Aperture Radar (POLSAR) data is proposed in this paper. The method is a combination of the unsupervised classification based on Cloudes H- decomposition and the modified C-mean algorithm. The fully polarimetric SAR image is initially classified using Cloudes method. The classification map is used as input of the modified C-mean algorithm, and then iteration is performed. It is important to determine the number of iteration in the modified C-mean algorithm, and a new termination criterion is presented using image entropy to do so. Compared with H- decomposition, not only scattering mechanisms of all classes can be preserved, but also terrain classification is effectively performed using this method. The effectiveness of this method is demonstrated using an L-band fully polarimetric SAR image of San Francisco, acquired by the NASA/JPL AIRSAR sensor.
A new method for unsupervised classification of terrain types using fully POLarimetric Synthetic Aperture Radar (POLSAR) data is proposed in this paper. The method is a combination of the unsupervised classification based on Cloudes H- decomposition and the modified C-mean algorithm. The fully polarimetric SAR image is initially classified using Cloudes method. The classification map is used as input of the modified C-mean algorithm, and then iteration is performed. It is important to determine the number of iteration in the modified C-mean algorithm, and a new termination criterion is presented using image entropy to do so. Compared with H- decomposition, not only scattering mechanisms of all classes can be preserved, but also terrain classification is effectively performed using this method. The effectiveness of this method is demonstrated using an L-band fully polarimetric SAR image of San Francisco, acquired by the NASA/JPL AIRSAR sensor.
2007, 29(1): 35-38.
doi: 10.3724/SP.J.1146.2005.00545
Abstract:
As for the RST transform in image registration, corresponding formula of box distance transform is dieduced. Compared with traditional formula of general affine Hausdorff box distance, search range of distance is reduced. The paper proposes regional Voronoi surface combining comparison of sliding windows when computing Hausdorff distance, characterized by reducing calculating-cost for Voronoi surface. It also has the advantages of eliminating trivial edges and preserving longer edges for calculating. Experimental results show that calculation speed of image regeistation based on Huasdorff distances is improved.
As for the RST transform in image registration, corresponding formula of box distance transform is dieduced. Compared with traditional formula of general affine Hausdorff box distance, search range of distance is reduced. The paper proposes regional Voronoi surface combining comparison of sliding windows when computing Hausdorff distance, characterized by reducing calculating-cost for Voronoi surface. It also has the advantages of eliminating trivial edges and preserving longer edges for calculating. Experimental results show that calculation speed of image regeistation based on Huasdorff distances is improved.
2007, 29(1): 39-42.
doi: 10.3724/SP.J.1146.2005.00485
Abstract:
It is extremely needed to conserve and restore old films. Intensity flicker is a common artifact in old black-and-white film sequences. Unfortunately, the existing algorithms removing intensity flicker do not consider the effect of local motion. To improve this point, a method based on the cosine basis and the successive over-relaxation is developed in this paper. Both local motion and local flicker are considered in this method. Experiments for real-world old film sequences shows that the result is satisfactory.
It is extremely needed to conserve and restore old films. Intensity flicker is a common artifact in old black-and-white film sequences. Unfortunately, the existing algorithms removing intensity flicker do not consider the effect of local motion. To improve this point, a method based on the cosine basis and the successive over-relaxation is developed in this paper. Both local motion and local flicker are considered in this method. Experiments for real-world old film sequences shows that the result is satisfactory.
2007, 29(1): 43-46.
doi: 10.3724/SP.J.1146.2005.00781
Abstract:
In this paper, a new method of image denoising is presented ,which is built upon the ideas of Embedded Zerotree Wavelet (EZW) encoder and separate character of signals and noises. This method is not only less than Tree-Adapted Wavelet Shrinkage (TAWS) method in operation amounts but also excellent in image denoising results and reservation of singularity information.
In this paper, a new method of image denoising is presented ,which is built upon the ideas of Embedded Zerotree Wavelet (EZW) encoder and separate character of signals and noises. This method is not only less than Tree-Adapted Wavelet Shrinkage (TAWS) method in operation amounts but also excellent in image denoising results and reservation of singularity information.
2007, 29(1): 47-49.
doi: 10.3724/SP.J.1146.2005.00438
Abstract:
In the research of super-resolution image processing, the precision and speed of the sub-pixel registration are the key factors. It is difficult for the Taylors series expansion method to do in real-time, and the hierarchical block-match method with less levels can achieve only a lower precision. The bicubic curve function method with hierarchical block-match drawn in this paper can not only obtain a higher precision, but also be implemented in real-time.
In the research of super-resolution image processing, the precision and speed of the sub-pixel registration are the key factors. It is difficult for the Taylors series expansion method to do in real-time, and the hierarchical block-match method with less levels can achieve only a lower precision. The bicubic curve function method with hierarchical block-match drawn in this paper can not only obtain a higher precision, but also be implemented in real-time.
2007, 29(1): 50-53.
doi: 10.3724/SP.J.1146.2005.00905
Abstract:
This paper proposes a novel spectrum-compressed digital receiving method using Laguerre transformation for LFM signal. Firstly, the frequency-warped characteristic of Laguerre transformation and its spectrum-compressed characteristic for LFM signal are discussed. Then, the spectrum-compressed network with variable compression degree is constructed by utilizing the digital structure of Laguerre transformation to keep the signal bandwidth within the receiver bandwidth, which reduces the amount of data to be processed in baseband. The spectrum-compressed signal can be reconstructed by using the spectrum-reconstructed network. The modulation rate and initial frequency of the spectrum-reconstructed LFM signal can be estimated precisely. Finally, the simulation results show the correctness and validity of the method.
This paper proposes a novel spectrum-compressed digital receiving method using Laguerre transformation for LFM signal. Firstly, the frequency-warped characteristic of Laguerre transformation and its spectrum-compressed characteristic for LFM signal are discussed. Then, the spectrum-compressed network with variable compression degree is constructed by utilizing the digital structure of Laguerre transformation to keep the signal bandwidth within the receiver bandwidth, which reduces the amount of data to be processed in baseband. The spectrum-compressed signal can be reconstructed by using the spectrum-reconstructed network. The modulation rate and initial frequency of the spectrum-reconstructed LFM signal can be estimated precisely. Finally, the simulation results show the correctness and validity of the method.
2007, 29(1): 54-58.
doi: 10.3724/SP.J.1146.2005.00468
Abstract:
Alpha stable distribution, a generalization of Gaussian, is better for modeling impulsive noises than Gaussian distribution in signal processing. This class of process has no close form of probability density function and finite second order moments. In this paper, a new adaptive generalized recursive least p-norm filtering algorithm is proposed based on SSG noise model. The simulation experiments show that the proposed new algorithm is more robust than the conventional algorithm.
Alpha stable distribution, a generalization of Gaussian, is better for modeling impulsive noises than Gaussian distribution in signal processing. This class of process has no close form of probability density function and finite second order moments. In this paper, a new adaptive generalized recursive least p-norm filtering algorithm is proposed based on SSG noise model. The simulation experiments show that the proposed new algorithm is more robust than the conventional algorithm.
2007, 29(1): 59-62.
doi: 10.3724/SP.J.1146.2005.00582
Abstract:
Epsilon machine is a new algorithm that tries to discover hidden patterns from data. Recently, the scholars in Santefe Institute have already applied it in symbol series successfully, but new problems emerge in traditional time series. A symbolization method transforming the sampling data into symbol series is presented, which implies some information of the expectation and variance. After Causal-State Splitting Reconstruction (CSSR), hundreds of states are lumped in the result, and a new recursion program can pick out the deterministic states very easily. Noise and nonstationarity will stunt the epsilon machine and they are the main problems to be researched in the future.
Epsilon machine is a new algorithm that tries to discover hidden patterns from data. Recently, the scholars in Santefe Institute have already applied it in symbol series successfully, but new problems emerge in traditional time series. A symbolization method transforming the sampling data into symbol series is presented, which implies some information of the expectation and variance. After Causal-State Splitting Reconstruction (CSSR), hundreds of states are lumped in the result, and a new recursion program can pick out the deterministic states very easily. Noise and nonstationarity will stunt the epsilon machine and they are the main problems to be researched in the future.
2007, 29(1): 63-66.
doi: 10.3724/SP.J.1146.2005.00569
Abstract:
Motion compensation is very important for high resolution SAS image. In this paper , the process of motion compensation based on inertial measuring system is discussed in detail, and then an improved point-by-point compensate image algorithm based on actual azimuth track is presented, which solves the problem that the traditional point-by-point image algorithm cant use directly for motion compensation. At last, simulation and lake experiment results confirm the efficiency of the algorithm.
Motion compensation is very important for high resolution SAS image. In this paper , the process of motion compensation based on inertial measuring system is discussed in detail, and then an improved point-by-point compensate image algorithm based on actual azimuth track is presented, which solves the problem that the traditional point-by-point image algorithm cant use directly for motion compensation. At last, simulation and lake experiment results confirm the efficiency of the algorithm.
2007, 29(1): 67-70.
doi: 10.3724/SP.J.1146.2005.00660
Abstract:
When using a microphone array for hands-free speech acquisition in enclosure environments, one can be faced with the problem of wave propagation in near-field. In this paper, therefore, a near-field beamforming method for microphone array based speech enhancement is introduced which modified subband adaptive beamforming method. The proposed method takes full advantage of spherical nature of the sound wavefront, in which the distance discrimination reduces the effect of reverberation as well as noise on the desired speech signal. Simulations experimental results demonstrate that the proposed microphone array based speech enhancement method exhibits a better noise reduction performance than other methods.
When using a microphone array for hands-free speech acquisition in enclosure environments, one can be faced with the problem of wave propagation in near-field. In this paper, therefore, a near-field beamforming method for microphone array based speech enhancement is introduced which modified subband adaptive beamforming method. The proposed method takes full advantage of spherical nature of the sound wavefront, in which the distance discrimination reduces the effect of reverberation as well as noise on the desired speech signal. Simulations experimental results demonstrate that the proposed microphone array based speech enhancement method exhibits a better noise reduction performance than other methods.
2007, 29(1): 71-75.
doi: 10.3724/SP.J.1146.2005.00452
Abstract:
The fundamental frequency contour (F0 contour) for utterance in rule-based speech synthesis system, is shaped by many functional unit in phonetics, not only the simple concatenation of F0 contour among the nearby syllables. In order to improve the naturalness of synthesized speech, this paper proposes a new forward idea of F0 contour optimization in Chinese prosodic chunk, which can integrate the environmental factors (such as, the stress, the distortion of syllable, the articulation velocity, etc.) into the F0 contour. And based on the idea of optimization, this paper inversely extracts the parameters associated with optimization (namely the top-line, the bottom-line, the smoothness, the distortion, the stress) from the clustered F0 contour using the MMSE principle for the monosyllable, the disyllable, the trisyllable chunks. Further, this paper analyzes the influence of position and tone to the parameters associated with optimization. The analyzed result shows the reliability of the extracted parameters and the rationality of the optimization theory on the whole, so the rules of the parameters associated with optimization can be got for the different prosodic chunk in speech synthesis system. The actual listening test shows that, the scores of intelligibility are 3.25 and 3.35 before and after the optimization, and the scores of naturalness are 2.9 and 3.31.
The fundamental frequency contour (F0 contour) for utterance in rule-based speech synthesis system, is shaped by many functional unit in phonetics, not only the simple concatenation of F0 contour among the nearby syllables. In order to improve the naturalness of synthesized speech, this paper proposes a new forward idea of F0 contour optimization in Chinese prosodic chunk, which can integrate the environmental factors (such as, the stress, the distortion of syllable, the articulation velocity, etc.) into the F0 contour. And based on the idea of optimization, this paper inversely extracts the parameters associated with optimization (namely the top-line, the bottom-line, the smoothness, the distortion, the stress) from the clustered F0 contour using the MMSE principle for the monosyllable, the disyllable, the trisyllable chunks. Further, this paper analyzes the influence of position and tone to the parameters associated with optimization. The analyzed result shows the reliability of the extracted parameters and the rationality of the optimization theory on the whole, so the rules of the parameters associated with optimization can be got for the different prosodic chunk in speech synthesis system. The actual listening test shows that, the scores of intelligibility are 3.25 and 3.35 before and after the optimization, and the scores of naturalness are 2.9 and 3.31.
2007, 29(1): 76-80.
doi: 10.3724/SP.J.1146.2005.00646
Abstract:
At present, most image watermarking schemes can not effectively resist geometrical attacks, which restricts the applications of digital watermarking techniques. RST (Rotation, Scaling, Translation) are frequently used geometrical attacks. In this paper a general multi-bit watermarking scheme for digital image that can resist to RST attacks is proposed. The measures taken in the scheme include: (1) a moment-based image normalization method is proposed to resist RST; (2) The multi-bit message is hidden in a 2D CDMA watermark using spread spectrum technique; (3) The watermark is embedded into cover image exploiting the properties of HVS to obtain the compromise between watermark robustness and invisibility. (4) The watermark is estimated according to MAP and detected by means of correlation-detection. Experimental results show the scheme is robust to compression, filtering as well as RST attacks.
At present, most image watermarking schemes can not effectively resist geometrical attacks, which restricts the applications of digital watermarking techniques. RST (Rotation, Scaling, Translation) are frequently used geometrical attacks. In this paper a general multi-bit watermarking scheme for digital image that can resist to RST attacks is proposed. The measures taken in the scheme include: (1) a moment-based image normalization method is proposed to resist RST; (2) The multi-bit message is hidden in a 2D CDMA watermark using spread spectrum technique; (3) The watermark is embedded into cover image exploiting the properties of HVS to obtain the compromise between watermark robustness and invisibility. (4) The watermark is estimated according to MAP and detected by means of correlation-detection. Experimental results show the scheme is robust to compression, filtering as well as RST attacks.
2007, 29(1): 81-86.
doi: 10.3724/SP.J.1146.2005.00515
Abstract:
Texture feature is one kind of important image features in multi-spectral images except with spectral characteristics. In this paper, the characteristics of orientation texture features are analyzed. And then the concept and method of integrated orientation texture feature are proposed and developed. On the basis of this, Significant Central Coefficient (SCC) image fusion algorithm based on integrated orientation texture feature in redundant wavelet field is proposed. The algorithm can combine spectral and morphological information in multi-spectral images successfully. It can pertain the spectral characteristics of source images and also take effect on fusion result of texture features into account. The new multi-spectral image fusion algorithm is carried out with emphases on the novelty of the fusion algorithm and the demonstration by using both simulated and real multi-spectral images. The subjective qualitative evaluation and objective quantitative analysis of the experimental results are made, appearing that the new algorithm can fuse the information and retain the texture features of source images more effectively compared with several existing fusion algorithms for multi-spectral images.
Texture feature is one kind of important image features in multi-spectral images except with spectral characteristics. In this paper, the characteristics of orientation texture features are analyzed. And then the concept and method of integrated orientation texture feature are proposed and developed. On the basis of this, Significant Central Coefficient (SCC) image fusion algorithm based on integrated orientation texture feature in redundant wavelet field is proposed. The algorithm can combine spectral and morphological information in multi-spectral images successfully. It can pertain the spectral characteristics of source images and also take effect on fusion result of texture features into account. The new multi-spectral image fusion algorithm is carried out with emphases on the novelty of the fusion algorithm and the demonstration by using both simulated and real multi-spectral images. The subjective qualitative evaluation and objective quantitative analysis of the experimental results are made, appearing that the new algorithm can fuse the information and retain the texture features of source images more effectively compared with several existing fusion algorithms for multi-spectral images.
2007, 29(1): 87-91.
doi: 10.3724/SP.J.1146.2005.00641
Abstract:
To avoid over segmentation produced by watershed segment algorithm, an image segment algorithm based on the adaptive preprocessing is proposed in this paper. This algorithm is based on the watershed transform. First the gradient image is preprocessed according to the pixels intensity and spatial information. After the points in the neighborhood of each image pixel are classified，their distribution situations are used to estimate the location of the image pixel, in the center or near the boundary of a region. Each pixels gradient magnitude is adaptive adjusted according to its location. Then the flat regions larger than 200 pixels in the preprocessed gradient magnitude image are extracted as markers. According to the markers, the preprocessed gradient magnitude image is segmented by the watershed transform. Experimental results indicate that this algorithm provides a good segmentation for segment-based image coding.
To avoid over segmentation produced by watershed segment algorithm, an image segment algorithm based on the adaptive preprocessing is proposed in this paper. This algorithm is based on the watershed transform. First the gradient image is preprocessed according to the pixels intensity and spatial information. After the points in the neighborhood of each image pixel are classified，their distribution situations are used to estimate the location of the image pixel, in the center or near the boundary of a region. Each pixels gradient magnitude is adaptive adjusted according to its location. Then the flat regions larger than 200 pixels in the preprocessed gradient magnitude image are extracted as markers. According to the markers, the preprocessed gradient magnitude image is segmented by the watershed transform. Experimental results indicate that this algorithm provides a good segmentation for segment-based image coding.
2007, 29(1): 92-95.
doi: 10.3724/SP.J.1146.2005.00492
Abstract:
In this paper, an adaptive particle filter for moving objects tracking is proposed. Mean shift is optimization algorithm based on gradient descended, which tracks moving targets through iterations. Particle filter is a robust method of tracking in non-Gauss and non-linear case. Firstly, a target model based on statistical histogram is proposed, which improves the classical histogram. Then Mean Shift algorithm and particle filter are integrated novelly through the statistical histogram target model. The parameters are modified according to the processing of tracking, so the effects caused by changed light or occlusion can be overcome. Experiments show that the method proposed by this paper can track moving target more powerful than Mean Shift tracked. Otherwise, even in complicated case, this method can still efficiently work.
In this paper, an adaptive particle filter for moving objects tracking is proposed. Mean shift is optimization algorithm based on gradient descended, which tracks moving targets through iterations. Particle filter is a robust method of tracking in non-Gauss and non-linear case. Firstly, a target model based on statistical histogram is proposed, which improves the classical histogram. Then Mean Shift algorithm and particle filter are integrated novelly through the statistical histogram target model. The parameters are modified according to the processing of tracking, so the effects caused by changed light or occlusion can be overcome. Experiments show that the method proposed by this paper can track moving target more powerful than Mean Shift tracked. Otherwise, even in complicated case, this method can still efficiently work.
2007, 29(1): 96-100.
doi: 10.3724/SP.J.1146.2005.00567
Abstract:
This paper presents a new method of estimating numbers and frequencies for sinusoid signals based on TransDimensional Simulated Annealing(TDSA) algorithm. This paper introduces penalty term and least square into TDSA, and gives a method that simultaneously estimates the numbers and frequencies of sinusoids signals in white gaussian noise. Finally, the validity of this method is well verified by the simulation.
This paper presents a new method of estimating numbers and frequencies for sinusoid signals based on TransDimensional Simulated Annealing(TDSA) algorithm. This paper introduces penalty term and least square into TDSA, and gives a method that simultaneously estimates the numbers and frequencies of sinusoids signals in white gaussian noise. Finally, the validity of this method is well verified by the simulation.
2007, 29(1): 101-104.
doi: 10.3724/SP.J.1146.2005.00597
Abstract:
Based on uniform linear array and 4th order cumulant of array output signals, a novel blind algorithm for spatial signature estimation was presented in this paper, and was applied to estimate spatial signature of multi-user with coherent multi-path. Using 4th order cumulant, the author constructed a spatial signature matrix , and then proved that multi-users spatial signature can be obtained through eigen decomposition of the matrix. The algorithm is not depended upon the specific characteristic of signal, and can be employed to additive arbitrary Gaussian (white or colored) noise. Theoretical analysis and computer simulation confirmed the availability and robustness of the algorithm.
Based on uniform linear array and 4th order cumulant of array output signals, a novel blind algorithm for spatial signature estimation was presented in this paper, and was applied to estimate spatial signature of multi-user with coherent multi-path. Using 4th order cumulant, the author constructed a spatial signature matrix , and then proved that multi-users spatial signature can be obtained through eigen decomposition of the matrix. The algorithm is not depended upon the specific characteristic of signal, and can be employed to additive arbitrary Gaussian (white or colored) noise. Theoretical analysis and computer simulation confirmed the availability and robustness of the algorithm.
2007, 29(1): 105-108.
doi: 10.3724/SP.J.1146.2005.00558
Abstract:
Theoretical investigations have proven that the system combining beamforming with space-time block coding can improve the performance efficiently, compared to the conventional single beamforming or space-time block coding only schemes. The conventional decoding schemes, which need accurate Channel State Information (CSI), are usually based on channel estimation. When the CSI is hard to achieve in some cases, the system performance would be affected heavily. Independent component analysis (ICA), one classical blind signal separation technique, can be used to detect the transmitted signals without channel estimation. Aiming at signals structure at the receiver, this paper proposed an orthogonal detecting scheme based on ICA. Simulations were carried out to compare the performance of the new scheme with conventional schemes. Simulation results for Rayleigh fading channels demonstrated that the new scheme could enhance the flexibility of the communication system and achieve better Bit Error Rate (BER) performance.
Theoretical investigations have proven that the system combining beamforming with space-time block coding can improve the performance efficiently, compared to the conventional single beamforming or space-time block coding only schemes. The conventional decoding schemes, which need accurate Channel State Information (CSI), are usually based on channel estimation. When the CSI is hard to achieve in some cases, the system performance would be affected heavily. Independent component analysis (ICA), one classical blind signal separation technique, can be used to detect the transmitted signals without channel estimation. Aiming at signals structure at the receiver, this paper proposed an orthogonal detecting scheme based on ICA. Simulations were carried out to compare the performance of the new scheme with conventional schemes. Simulation results for Rayleigh fading channels demonstrated that the new scheme could enhance the flexibility of the communication system and achieve better Bit Error Rate (BER) performance.
2007, 29(1): 109-112.
doi: 10.3724/SP.J.1146.2005.00529
Abstract:
In this paper, a DOA estimation algorithm for non-stationary signals embedded in impulsive SS noise environments is proposed. Firstly, a Spatial Ambiguity Function based on the Fractional Lower Order Statistics (FLOS-SAF) is defined to separate signals by exploiting the ambiguity domain characteristic. Then the average of ambiguity-domain points is carefully selected to perform the subspace analysis. Finally the MUSIC algorithm is applied to obtain DOA estimates. Comparison with the spatial processing method using fractional lower order statistics, the proposed algorithm provides more precise DOA estimates by using the ambiguity domain information of signals. Computer simulation results show the effectiveness of the algorithm.
In this paper, a DOA estimation algorithm for non-stationary signals embedded in impulsive SS noise environments is proposed. Firstly, a Spatial Ambiguity Function based on the Fractional Lower Order Statistics (FLOS-SAF) is defined to separate signals by exploiting the ambiguity domain characteristic. Then the average of ambiguity-domain points is carefully selected to perform the subspace analysis. Finally the MUSIC algorithm is applied to obtain DOA estimates. Comparison with the spatial processing method using fractional lower order statistics, the proposed algorithm provides more precise DOA estimates by using the ambiguity domain information of signals. Computer simulation results show the effectiveness of the algorithm.
2007, 29(1): 113-116.
doi: 10.3724/SP.J.1146.2005.00528
Abstract:
In Orthogonal Frequency-Division Multiplexing (OFDM) systems, how to estimate rapidly time-varying channels exactly is a challenge issue. In this paper, relying on a basis expansion channel model, a channel estimation scheme of rapidly time-varying channels is proposed for OFDM systems. Along with the channel estimation scheme, the optimal pilot sequence and optimal placement of the pilot tones are also derived with respect to the mean square error (MSE) of the channel estimate. It is shown that the optimal pilot sequence consists of some adjacent equipowered and equispaced subsequences, and each of them is constrained by certain phase conditions. Simulation results demonstrate the effectiveness of the proposed channel estimation scheme in rapidly time-varying scenarios and the superiority of using the derived optimal pilot sequences.
In Orthogonal Frequency-Division Multiplexing (OFDM) systems, how to estimate rapidly time-varying channels exactly is a challenge issue. In this paper, relying on a basis expansion channel model, a channel estimation scheme of rapidly time-varying channels is proposed for OFDM systems. Along with the channel estimation scheme, the optimal pilot sequence and optimal placement of the pilot tones are also derived with respect to the mean square error (MSE) of the channel estimate. It is shown that the optimal pilot sequence consists of some adjacent equipowered and equispaced subsequences, and each of them is constrained by certain phase conditions. Simulation results demonstrate the effectiveness of the proposed channel estimation scheme in rapidly time-varying scenarios and the superiority of using the derived optimal pilot sequences.
2007, 29(1): 117-120.
doi: 10.3724/SP.J.1146.2005.00439
Abstract:
MMSE estimator is a common channel estimator in coherent OFDM systems. Against mismatch problem of MMSE estimator, an improved MMSE channel estimator based on adaptive order determination is proposed. This algorithm estimates the maximum multipath delay, and calculates the channel autocorrelation function adaptively. It is shown that the proposed method performance is close to the optimal matched MMSE estimator.
MMSE estimator is a common channel estimator in coherent OFDM systems. Against mismatch problem of MMSE estimator, an improved MMSE channel estimator based on adaptive order determination is proposed. This algorithm estimates the maximum multipath delay, and calculates the channel autocorrelation function adaptively. It is shown that the proposed method performance is close to the optimal matched MMSE estimator.
2007, 29(1): 121-124.
doi: 10.3724/SP.J.1146.2005.00681
Abstract:
Artificial Fish School Algorithm (AFSA) is a new kind of intelligence optimization algorithm, which has some advantages that Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) do not have. But this algorithm has several disadvantages such as the blindness of searching at the later stage and the poor ability to keep the balance of exploration and exploitation, which reduce its probability of searching the best result. To overcome these problems, two improved AFSA named AAFSA_FP and AAFSA_SP were proposed based on idea of adaptive. Then the new algorithms are applied to solve the multiuser detection problems. Simulation results show that the proposed detectors outperform GA detector and PSO detector in terms of BER, near-far resistant and convergence performance.
Artificial Fish School Algorithm (AFSA) is a new kind of intelligence optimization algorithm, which has some advantages that Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) do not have. But this algorithm has several disadvantages such as the blindness of searching at the later stage and the poor ability to keep the balance of exploration and exploitation, which reduce its probability of searching the best result. To overcome these problems, two improved AFSA named AAFSA_FP and AAFSA_SP were proposed based on idea of adaptive. Then the new algorithms are applied to solve the multiuser detection problems. Simulation results show that the proposed detectors outperform GA detector and PSO detector in terms of BER, near-far resistant and convergence performance.
2007, 29(1): 125-128.
doi: 10.3724/SP.J.1146.2005.00602
Abstract:
An algorithm based on higher-order cyclic cumulants for the automatic classification of SQAM signals is proposed. The algorithm utilizes the cyclostationary property of communication signals and presents classification feature in cyclic cumulants domain. It is robust to the presence of carrier frequency offsets, time delay and phase offsets. Interesting signals can also be classified under the presence of interference signals and carrier frequency offsets. The efficiency of the proposed classification algorithm is verified via theoretical analysis and extensive simulations.
An algorithm based on higher-order cyclic cumulants for the automatic classification of SQAM signals is proposed. The algorithm utilizes the cyclostationary property of communication signals and presents classification feature in cyclic cumulants domain. It is robust to the presence of carrier frequency offsets, time delay and phase offsets. Interesting signals can also be classified under the presence of interference signals and carrier frequency offsets. The efficiency of the proposed classification algorithm is verified via theoretical analysis and extensive simulations.
2007, 29(1): 129-132.
doi: 10.3724/SP.J.1146.2005.00575
Abstract:
From the mathematical point of view, information sources can be 1-to-1 mapped to stochastic processes. Known from the theory of chaos, multi-fractal of stochastic process is a key characteristic of its dynamics, of which entropy rate is a special fractal dimension named information dimension. The paper introduces methods of statistical physics to compute the multi-fractal of stochastic process so that the entropy rate of source can be obtained at once. Take binary hidden Markov processes as example, the paper demonstrate how this approach works. The results shows that the methods is applicable to numerically approximate the entropy rate of binary hidden Markov processes (BHMPs) in practical applications, and it can be applied in more generalized kinds of information sources.
From the mathematical point of view, information sources can be 1-to-1 mapped to stochastic processes. Known from the theory of chaos, multi-fractal of stochastic process is a key characteristic of its dynamics, of which entropy rate is a special fractal dimension named information dimension. The paper introduces methods of statistical physics to compute the multi-fractal of stochastic process so that the entropy rate of source can be obtained at once. Take binary hidden Markov processes as example, the paper demonstrate how this approach works. The results shows that the methods is applicable to numerically approximate the entropy rate of binary hidden Markov processes (BHMPs) in practical applications, and it can be applied in more generalized kinds of information sources.
2007, 29(1): 133-137.
doi: 10.3724/SP.J.1146.2005.00470
Abstract:
The LMMSE channel estimation algorithms based on Pilot-Assisted is investigated for MIMO-OFDM systems，and the Low-Bound of MSE for LMMSE channel estimation is derived. A low rank channel estimator, at first, by using Singular Value Decomposition (SVD) is presented to reduce the complexity; Secondly, a simplified algorithm by using optimal pilot design is proposed. The simplified algorithm reduces not only the complexity evidently, but also attains the best estimation performance; Finally, The methods for estimating channel properties are developed.
The LMMSE channel estimation algorithms based on Pilot-Assisted is investigated for MIMO-OFDM systems，and the Low-Bound of MSE for LMMSE channel estimation is derived. A low rank channel estimator, at first, by using Singular Value Decomposition (SVD) is presented to reduce the complexity; Secondly, a simplified algorithm by using optimal pilot design is proposed. The simplified algorithm reduces not only the complexity evidently, but also attains the best estimation performance; Finally, The methods for estimating channel properties are developed.
2007, 29(1): 138-142.
doi: 10.3724/SP.J.1146.2005.00612
Abstract:
Providing Quality of Service (QoS) in wireless communication system is studied in this paper. First, the Round Robin (RR) scheduler and the joint KH/RR scheduler are analyzed by employing the ergodic capacity of fading channel. Then, a novel Partial Multiuser Diversity Scheduler (PMDS) is proposed. A frame is initially divided into several subframes whose size and current users are determined by the bit rate requirement of each user in the resource allocation module. Each subframe is then assigned to the user with the largest channel gain among its current users in the scheduler. Simulation results show that the proposed PMDS takes fewer channel usage and has a higher channel capacity than both the RR scheduler and joint KH/RR scheduler.
Providing Quality of Service (QoS) in wireless communication system is studied in this paper. First, the Round Robin (RR) scheduler and the joint KH/RR scheduler are analyzed by employing the ergodic capacity of fading channel. Then, a novel Partial Multiuser Diversity Scheduler (PMDS) is proposed. A frame is initially divided into several subframes whose size and current users are determined by the bit rate requirement of each user in the resource allocation module. Each subframe is then assigned to the user with the largest channel gain among its current users in the scheduler. Simulation results show that the proposed PMDS takes fewer channel usage and has a higher channel capacity than both the RR scheduler and joint KH/RR scheduler.
2007, 29(1): 143-147.
doi: 10.3724/SP.J.1146.2005.00571
Abstract:
BLAST can effectively increase information rate in multi-antenna system. The simplest space multiplex method is V-BLAST, which has simple detection algorithm such as ZF-DFE, MMSE-DFE, ML and ML-DFE etc. This paper discussed methods to improve the ML-DFE algorithm, proposed combined LSD and DFE detection algorithm based on ZF and MMSE criteria. Simulation results show that large performance improvement can be obtained when the LSD algorithm output only 3 detection results, and the algorithm based on MMSE criteria has better performance than based on ZF criteria.
BLAST can effectively increase information rate in multi-antenna system. The simplest space multiplex method is V-BLAST, which has simple detection algorithm such as ZF-DFE, MMSE-DFE, ML and ML-DFE etc. This paper discussed methods to improve the ML-DFE algorithm, proposed combined LSD and DFE detection algorithm based on ZF and MMSE criteria. Simulation results show that large performance improvement can be obtained when the LSD algorithm output only 3 detection results, and the algorithm based on MMSE criteria has better performance than based on ZF criteria.
2007, 29(1): 148-151.
doi: 10.3724/SP.J.1146.2005.00552
Abstract:
To handle co-antenna interference, intersymbol interference (ISI) and intercarrier interference (ICI) caused by insufficient cyclic prefix, a MMSE-based Turbo per-tone equalization is presented for MIMO OFDM systems in this paper. A Soft-Input Soft-Out (SISO) per-tone equalizer exchanges soft information with SISO channel decoder through iterative process. Simulation results show that the proposed Turbo per-tone equalizers can effectively exploit time diversity and space diversity and offer performance gain over non-iterative equalizers.
To handle co-antenna interference, intersymbol interference (ISI) and intercarrier interference (ICI) caused by insufficient cyclic prefix, a MMSE-based Turbo per-tone equalization is presented for MIMO OFDM systems in this paper. A Soft-Input Soft-Out (SISO) per-tone equalizer exchanges soft information with SISO channel decoder through iterative process. Simulation results show that the proposed Turbo per-tone equalizers can effectively exploit time diversity and space diversity and offer performance gain over non-iterative equalizers.
2007, 29(1): 152-156.
doi: 10.3724/SP.J.1146.2005.00280
Abstract:
A joint WLMS channel estimation and detection algorithm based Turbo iteration is proposed in this paper. Using the soft information provided by the soft mapping and demapping algorithms, the proposed algorithm achieve its information exchange between detection module and channel estimation module. The channel response is updated symbol by symbol by using the WLMS channel estimation and tracking algorithm. The simulation results show that the BER performance had converged after two iterative, and there is only 0.4-0.5dB performance losing compared with ideal channel estimation at a system BER of 10-3.
A joint WLMS channel estimation and detection algorithm based Turbo iteration is proposed in this paper. Using the soft information provided by the soft mapping and demapping algorithms, the proposed algorithm achieve its information exchange between detection module and channel estimation module. The channel response is updated symbol by symbol by using the WLMS channel estimation and tracking algorithm. The simulation results show that the BER performance had converged after two iterative, and there is only 0.4-0.5dB performance losing compared with ideal channel estimation at a system BER of 10-3.
2007, 29(1): 157-160.
doi: 10.3724/SP.J.1146.2005.00705
Abstract:
All the traditional channel estimation methods have the same default: they use too many pilots which decreases the frequency efficiency. The subject of this paper mainly focuses on the research of new algorithms and proposes the channel estimation principle explicitly: separate the estimation of multi-path amplitude and delay. Periodic block type pilot are used for the path delay. And for amplitude, a dynamic pilot pattern is proposed. Simulation shows that, comparing to the traditional low pass filter methods, the proposed method has better performance, lower complexity, and saving more than 70 percent of the pilots.
All the traditional channel estimation methods have the same default: they use too many pilots which decreases the frequency efficiency. The subject of this paper mainly focuses on the research of new algorithms and proposes the channel estimation principle explicitly: separate the estimation of multi-path amplitude and delay. Periodic block type pilot are used for the path delay. And for amplitude, a dynamic pilot pattern is proposed. Simulation shows that, comparing to the traditional low pass filter methods, the proposed method has better performance, lower complexity, and saving more than 70 percent of the pilots.
2007, 29(1): 161-165.
doi: 10.3724/SP.J.1146.2005.00549
Abstract:
A tool of intra prediction is introduced in the new video coding standard-H.264, which can cut down the spatial redundancy effectively. Though intra prediction can reduce the bit rate, it is undoubtedly computationally intensive. To overcome this drawback, a novel fast intra prediction algorithm is proposed in this paper. By make use of the information in the transform domain, the direction of texture is estimated at first and then the intra mode decision will be made among several most possible mode, which can diminish the number of calculation. To variable video sequences, the simulation results show that with the proposed algorithm the time of the intra coding can be reduce about 70% while keep the equivalent precision. It is conclusion that the proposed algorithm is suitable to the real-time implements with rigorous requirement on delay.
A tool of intra prediction is introduced in the new video coding standard-H.264, which can cut down the spatial redundancy effectively. Though intra prediction can reduce the bit rate, it is undoubtedly computationally intensive. To overcome this drawback, a novel fast intra prediction algorithm is proposed in this paper. By make use of the information in the transform domain, the direction of texture is estimated at first and then the intra mode decision will be made among several most possible mode, which can diminish the number of calculation. To variable video sequences, the simulation results show that with the proposed algorithm the time of the intra coding can be reduce about 70% while keep the equivalent precision. It is conclusion that the proposed algorithm is suitable to the real-time implements with rigorous requirement on delay.
2007, 29(1): 166-168.
doi: 10.3724/SP.J.1146.2005.00580
Abstract:
In a wide variety of broadband applications, there is a need to distribute information to a potentially large number of receiver sites that are widely dispersed from each other. Communication satellites are a natural technology option and are extremely well suited for carrying such services because of the inherent broadcast capability of the satellite channel. Despite the potential of satellite multicast, there exists little support for reliable multicast services over satellite networks. Although several multicast protocols have been proposed for use over the Internet, they are not optimized for satellite networks. One of the key multicast components that are affected when satellite networks are involved in the communication is the transport layer. A novel Agent-based Satellite reliable Multicast Transport Protocols (ASMTP) is proposed in this paper for data dissemination over broadband satellite networks. This protocol employs agent in receivers group to implement reliable multicast transport for satellite networks. Packet level FEC and local error recovery are used to recover the correlated and uncorrelated packet losses. Flow and congestion control scheme are deployed also in ASMTP. Performance evaluation by simulations shows that ASMTP generally outperforms MFTP and achieves high scalability.
In a wide variety of broadband applications, there is a need to distribute information to a potentially large number of receiver sites that are widely dispersed from each other. Communication satellites are a natural technology option and are extremely well suited for carrying such services because of the inherent broadcast capability of the satellite channel. Despite the potential of satellite multicast, there exists little support for reliable multicast services over satellite networks. Although several multicast protocols have been proposed for use over the Internet, they are not optimized for satellite networks. One of the key multicast components that are affected when satellite networks are involved in the communication is the transport layer. A novel Agent-based Satellite reliable Multicast Transport Protocols (ASMTP) is proposed in this paper for data dissemination over broadband satellite networks. This protocol employs agent in receivers group to implement reliable multicast transport for satellite networks. Packet level FEC and local error recovery are used to recover the correlated and uncorrelated packet losses. Flow and congestion control scheme are deployed also in ASMTP. Performance evaluation by simulations shows that ASMTP generally outperforms MFTP and achieves high scalability.
2007, 29(1): 169-173.
doi: 10.3724/SP.J.1146.2005.00513
Abstract:
Theorelical and mathematical analyses of multicarrier CDMA capacity planning are proposed and the expressions of capacity for multicarrier CDMA are derived both in uplink and downlink. Through extremum of a multivariate function (by Lagrange multipliers), the maximum capacity of multicarrier CDMA is achieved from the viewpoint of voice and data, respectively. Simultaneously, the important conclusions are got for multicarrier CDMA: when BS maximum transmit power is average distributed for all subcarriers, the maximum of capacity is achieved. Simulation results show that capacity of all kinds of service will decrease rapidly as average path loss increase. The essence is opened out between capacity and coverage: capacity and coverage restrict each other, decreasing in capacity means extend in coverage, and vice versa. When transmit power is in higher level, increasing power is not an effective way to improve capacity. From comparison between GSM, WCDMA and multicarrier CDMA, the conclusion are achieved that the spectrum efficiency of multicarrier CDMA is 1.7 times that of WCDMA, and 2.7 times that of GSM in downlink; and 2.1 time that of WCDMA, and 2.4 times that of GSM in uplink.
Theorelical and mathematical analyses of multicarrier CDMA capacity planning are proposed and the expressions of capacity for multicarrier CDMA are derived both in uplink and downlink. Through extremum of a multivariate function (by Lagrange multipliers), the maximum capacity of multicarrier CDMA is achieved from the viewpoint of voice and data, respectively. Simultaneously, the important conclusions are got for multicarrier CDMA: when BS maximum transmit power is average distributed for all subcarriers, the maximum of capacity is achieved. Simulation results show that capacity of all kinds of service will decrease rapidly as average path loss increase. The essence is opened out between capacity and coverage: capacity and coverage restrict each other, decreasing in capacity means extend in coverage, and vice versa. When transmit power is in higher level, increasing power is not an effective way to improve capacity. From comparison between GSM, WCDMA and multicarrier CDMA, the conclusion are achieved that the spectrum efficiency of multicarrier CDMA is 1.7 times that of WCDMA, and 2.7 times that of GSM in downlink; and 2.1 time that of WCDMA, and 2.4 times that of GSM in uplink.
2007, 29(1): 174-176.
doi: 10.3724/SP.J.1146.2005.00589
Abstract:
This paper researches low complexity detection scheme based on joint transmission scheme in multi-user MIMO downlink. Firstly, a model of multi-user MIMO downlink is introduced. A data transmission algorithm is got which can greatly reduce receivers calculative cost for multi-user MIMO downlink. And each mobile station receiver needs only one linear filter. Then through simulation and analysis in the TD-SCDMA system, Multi-user JT MIMO demonstrates its superiority and application prosperity.
This paper researches low complexity detection scheme based on joint transmission scheme in multi-user MIMO downlink. Firstly, a model of multi-user MIMO downlink is introduced. A data transmission algorithm is got which can greatly reduce receivers calculative cost for multi-user MIMO downlink. And each mobile station receiver needs only one linear filter. Then through simulation and analysis in the TD-SCDMA system, Multi-user JT MIMO demonstrates its superiority and application prosperity.
2007, 29(1): 177-181.
doi: 10.3724/SP.J.1146.2005.00748
Abstract:
High energy efficiency is one of the most important requirements for Wireless Sensor Network (WSN) design, and energy efficient routing is an important measure to achieve this goal. In this paper, a routing algorithm is proposed for WSN, GLB-DMECR, which adopts the Minimum Energy Consumption (MEC) as the metric. Comparing with other algorithms, GLB-DMECR has three obvious features: Firstly, GLB-DMECR adopts a novel routing idea, that is, the ideal MEC path is used to guide the routing procedure to find a practical MEC path. Secondly, GLB-DMECR adopts a decentralized and localized routing decision mechanism, which makes it more stable and scalable. Finally, GLB-DMECR exploits the utility of nodes Geographic Location Information (GLI) in routing and it adds little burden to the network. The implementation of GLB-DMECR is relatively simple, and it has been verified by simulation that the MEC performance of GLB-DMECR is better than or equivalent to that of present other typical MEC algorithms under wide network circumstances.
High energy efficiency is one of the most important requirements for Wireless Sensor Network (WSN) design, and energy efficient routing is an important measure to achieve this goal. In this paper, a routing algorithm is proposed for WSN, GLB-DMECR, which adopts the Minimum Energy Consumption (MEC) as the metric. Comparing with other algorithms, GLB-DMECR has three obvious features: Firstly, GLB-DMECR adopts a novel routing idea, that is, the ideal MEC path is used to guide the routing procedure to find a practical MEC path. Secondly, GLB-DMECR adopts a decentralized and localized routing decision mechanism, which makes it more stable and scalable. Finally, GLB-DMECR exploits the utility of nodes Geographic Location Information (GLI) in routing and it adds little burden to the network. The implementation of GLB-DMECR is relatively simple, and it has been verified by simulation that the MEC performance of GLB-DMECR is better than or equivalent to that of present other typical MEC algorithms under wide network circumstances.
2007, 29(1): 182-184.
doi: 10.3724/SP.J.1146.2005.00650
Abstract:
An attack is mounted on a group signature scheme based on Chinese Remainder Theory(Chen-Scheme). It shows the Chen-Scheme is insecure: A colluding subset of group members can find the private key of other members and forge their signatures; The dishonest group center can produce a valid signature on behalf of group members. Using Schnorr signature scheme this paper proposes an improve scheme, which has good characteristics: A colluding subset of group members can not produce a valid signature that the group manager can not open; A dishonest group center can not sign messages on behalf of other members; The revocation of the membership is efficient .
An attack is mounted on a group signature scheme based on Chinese Remainder Theory(Chen-Scheme). It shows the Chen-Scheme is insecure: A colluding subset of group members can find the private key of other members and forge their signatures; The dishonest group center can produce a valid signature on behalf of group members. Using Schnorr signature scheme this paper proposes an improve scheme, which has good characteristics: A colluding subset of group members can not produce a valid signature that the group manager can not open; A dishonest group center can not sign messages on behalf of other members; The revocation of the membership is efficient .
2007, 29(1): 185-188.
doi: 10.3724/SP.J.1146.2005.00656
Abstract:
LUC public-key cryptosystem is analyzed, two new public-key cryptosystems on Lucas sequence LUC-RSA, LUC-Rabin are presented, their security are stonger than LUC, RSA, and the rate of throughput of the data are greater than LUC.
LUC public-key cryptosystem is analyzed, two new public-key cryptosystems on Lucas sequence LUC-RSA, LUC-Rabin are presented, their security are stonger than LUC, RSA, and the rate of throughput of the data are greater than LUC.
2007, 29(1): 189-192.
doi: 10.3724/SP.J.1146.2005.00346
Abstract:
This paper designs a communion key distribution protocol based on asymmetric cipher system, and an authentication protocol based on symmetric cipher system for the requirement of digital mobile communication system. Then this protocol is analyzed by using the Spi calculus and its security is proved.
This paper designs a communion key distribution protocol based on asymmetric cipher system, and an authentication protocol based on symmetric cipher system for the requirement of digital mobile communication system. Then this protocol is analyzed by using the Spi calculus and its security is proved.
2007, 29(1): 193-196.
doi: 10.3724/SP.J.1146.2005.00486
Abstract:
This paper points out that the stream cipher model in construction and properties of balance feedforword sequences is a filter-combination model with generalized semi-Bent function as feedforward function, and analyses the stream cipher model simply.
This paper points out that the stream cipher model in construction and properties of balance feedforword sequences is a filter-combination model with generalized semi-Bent function as feedforward function, and analyses the stream cipher model simply.
2007, 29(1): 197-200.
doi: 10.3724/SP.J.1146.2005.00329
Abstract:
Hyper Bent functions achieve the maximal minimum distance to all the m sequences．In this paper, the relationship between the hyper Bent function on F22m and the Bent function on GF2m(2) is studied and two methods for constructing vectorial hyper Bent functions on Fp2m are proposed as well．
Hyper Bent functions achieve the maximal minimum distance to all the m sequences．In this paper, the relationship between the hyper Bent function on F22m and the Bent function on GF2m(2) is studied and two methods for constructing vectorial hyper Bent functions on Fp2m are proposed as well．
2007, 29(1): 201-204.
doi: 10.3724/SP.J.1146.2005.00574
Abstract:
The security of the two ring signature schemes proposed by Xu(2004) and Zhang(2004) is analyzed, and its found that both the ring signature schemes are susceptible to group-changing attack. In addition, Zhangs scheme can easily be attacked by multiple-known-signature existential forgery. To guard against the two attacks, the two ring signature schemes are improved, which can make the improved schemes is still secure even in the strongest security model (proposed by Joseph in 2004).
The security of the two ring signature schemes proposed by Xu(2004) and Zhang(2004) is analyzed, and its found that both the ring signature schemes are susceptible to group-changing attack. In addition, Zhangs scheme can easily be attacked by multiple-known-signature existential forgery. To guard against the two attacks, the two ring signature schemes are improved, which can make the improved schemes is still secure even in the strongest security model (proposed by Joseph in 2004).
2007, 29(1): 205-208.
doi: 10.3724/SP.J.1146.2005.00453
Abstract:
An extended layered graph of MPLS over WDM mesh networks is designed in this paper, which overcomes the shortcomings of original layered graph and involves the limited optical transceivers at routing nodes. Based on different QoS constraint, the priority of label switch paths is classified and the corresponding routing algorithm DIRA (Differentiating Integrated Routing Algorithm) is proposed and studied. The LSPs QoS and optimized network resources utilization are taken into account comprehensively in DIRA. The comparison of DIRA with the representative optical routing algorithms via simulation shows that it can reduce the blocking probability of delay-constraint LSP and improve the network throughput.
An extended layered graph of MPLS over WDM mesh networks is designed in this paper, which overcomes the shortcomings of original layered graph and involves the limited optical transceivers at routing nodes. Based on different QoS constraint, the priority of label switch paths is classified and the corresponding routing algorithm DIRA (Differentiating Integrated Routing Algorithm) is proposed and studied. The LSPs QoS and optimized network resources utilization are taken into account comprehensively in DIRA. The comparison of DIRA with the representative optical routing algorithms via simulation shows that it can reduce the blocking probability of delay-constraint LSP and improve the network throughput.
2007, 29(1): 209-213.
doi: 10.3724/SP.J.1146.2005.00642
Abstract:
Robust multimedia transmission over heterogeneous wireless networks is challenging. A protocol architecture that considers cross layer interaction is required. In this paper, an adaptive cross layer unequal protection strategy is proposed for video transmission over wireless channels. This strategy performs joint optimization across application layer, link layer and physical layer to provide unequal protection ability for video bitstream with different priority. Experimental results show the extraordinary improvement in PSNR of the proposed adaptive cross layer strategy over a variety of channel conditions.
Robust multimedia transmission over heterogeneous wireless networks is challenging. A protocol architecture that considers cross layer interaction is required. In this paper, an adaptive cross layer unequal protection strategy is proposed for video transmission over wireless channels. This strategy performs joint optimization across application layer, link layer and physical layer to provide unequal protection ability for video bitstream with different priority. Experimental results show the extraordinary improvement in PSNR of the proposed adaptive cross layer strategy over a variety of channel conditions.
2007, 29(1): 214-217.
doi: 10.3724/SP.J.1146.2005.00947
Abstract:
Quality of Service (QoS) and Traffic Engineering (TE) capabilities are two important techniques in todays networks for supporting real-time applications. Multi Protocol Label Switching (MPLS) plays an important part in IP networks for providing QoS and TE features. A general method to configure network based on MPLS is firstly introduced, then, a method to allocate network resource based on constraints at the DiffServ domain in IP network is proposed. The mathematical model and simulation of the method is given too. The simulation results show that the proposed method can balance the network load while the increase of the network cost is little.
Quality of Service (QoS) and Traffic Engineering (TE) capabilities are two important techniques in todays networks for supporting real-time applications. Multi Protocol Label Switching (MPLS) plays an important part in IP networks for providing QoS and TE features. A general method to configure network based on MPLS is firstly introduced, then, a method to allocate network resource based on constraints at the DiffServ domain in IP network is proposed. The mathematical model and simulation of the method is given too. The simulation results show that the proposed method can balance the network load while the increase of the network cost is little.
2007, 29(1): 218-222.
doi: 10.3724/SP.J.1146.2005.00546
Abstract:
For lack of bandwidth allocation algorithm or proposal in IEEE802.16 wireless metropolitan area network standard, in this paper a unite model based on logarithm utility function derived from 802.16 service flows bandwidth allocation is present. Then the allocation is described by a nonlinear programming (NP) problem which will maximize the utility. Due to the real time need of practical application, a quick solution of logarithm utility function is proposed, which can solve the NP problem by linear operations with significant decrease in computational complexity. The simulation results show that the maximizing utility algorithm has evident advantages in both throughput and utility compared with the max-min fair algorithms. It is also shown that the parameters of the utility function can be flexibly shifted to meet different quality of service demand with efficient allocation.
For lack of bandwidth allocation algorithm or proposal in IEEE802.16 wireless metropolitan area network standard, in this paper a unite model based on logarithm utility function derived from 802.16 service flows bandwidth allocation is present. Then the allocation is described by a nonlinear programming (NP) problem which will maximize the utility. Due to the real time need of practical application, a quick solution of logarithm utility function is proposed, which can solve the NP problem by linear operations with significant decrease in computational complexity. The simulation results show that the maximizing utility algorithm has evident advantages in both throughput and utility compared with the max-min fair algorithms. It is also shown that the parameters of the utility function can be flexibly shifted to meet different quality of service demand with efficient allocation.
2007, 29(1): 223-226.
doi: 10.3724/SP.J.1146.2005.01313
Abstract:
Memory Cell is a basic and important macro block of SRAM. It has played a positive role in improving performance and reliability, lowering cost and power consumption. In this paper a new physical alpha-power law MOSEFT model is used to establish power and delay model related with SRAM memory cell. Adopting those performance models, memory cell area model and reliability analysis, a new memory cell structure optimization method is proposed. Experimental result shows SRAM power, access time and area are reduced by adopting this method, and computed performance parameter varies less than 10% compares with simulation result. Experiment results indicate the effectiveness and validity of the performance model and optimization method.
Memory Cell is a basic and important macro block of SRAM. It has played a positive role in improving performance and reliability, lowering cost and power consumption. In this paper a new physical alpha-power law MOSEFT model is used to establish power and delay model related with SRAM memory cell. Adopting those performance models, memory cell area model and reliability analysis, a new memory cell structure optimization method is proposed. Experimental result shows SRAM power, access time and area are reduced by adopting this method, and computed performance parameter varies less than 10% compares with simulation result. Experiment results indicate the effectiveness and validity of the performance model and optimization method.
2007, 29(1): 227-231.
doi: 10.3724/SP.J.1146.2005.00089
Abstract:
Method for realizing time-domain Continuous Wavelet Transform (CWT) using Switched-current (SI) technology is firstly presented in this paper. It is shown a new way for fast implementation of CWT based on amplitude modulation techniques for generating wavelet chain. SI low pass filter is synthesized with SI integrators based on bilinear transform. Thus, It provides a solution to manufacture integrated chip of time-domain CWT. The SI low pass filter is simulated using ASIZ and verified to be able to meet the needs of time-domain CWT.
Method for realizing time-domain Continuous Wavelet Transform (CWT) using Switched-current (SI) technology is firstly presented in this paper. It is shown a new way for fast implementation of CWT based on amplitude modulation techniques for generating wavelet chain. SI low pass filter is synthesized with SI integrators based on bilinear transform. Thus, It provides a solution to manufacture integrated chip of time-domain CWT. The SI low pass filter is simulated using ASIZ and verified to be able to meet the needs of time-domain CWT.
2007, 29(1): 232-235.
doi: 10.3724/SP.J.1146.2005.00889
Abstract:
For monitoring system which fixed on rotating component, the energy supply is a difficult problem for a long time. A non-contact energy transmission technology based on microstrip antennas is put forward to replace the traditional methods such as slip-rings or optoelectronic cell. Taking torque monitoring as the application background, the total scheme of the energy transmission system and the feeding method of antennas are presented. The various conditions of microstrip antennas in energy transmission course are studied and the influence of rotating velocity on energy transmission is analyzed.
For monitoring system which fixed on rotating component, the energy supply is a difficult problem for a long time. A non-contact energy transmission technology based on microstrip antennas is put forward to replace the traditional methods such as slip-rings or optoelectronic cell. Taking torque monitoring as the application background, the total scheme of the energy transmission system and the feeding method of antennas are presented. The various conditions of microstrip antennas in energy transmission course are studied and the influence of rotating velocity on energy transmission is analyzed.
2007, 29(1): 243-245.
doi: 10.3724/SP.J.1146.2005.00623
Abstract:
The paper presents the n-th order current mode filter circuit with multiple inputs and one output based on MCCCII (second generation Current Controlled Conveyor with Multiple outputs). The filter circuit which contains n active elements and n capacitors can produce nth order low-pass, band-pass, high-pass, band-stop filters. Various kinds of filters can be realized just by changing the amount and mode of joining external current signals to the circuit. Internal structure of circuit and amount of elements need not change. So the circuit is convenient to integrated .The paper also makes PSPICE simulation for the filter.
The paper presents the n-th order current mode filter circuit with multiple inputs and one output based on MCCCII (second generation Current Controlled Conveyor with Multiple outputs). The filter circuit which contains n active elements and n capacitors can produce nth order low-pass, band-pass, high-pass, band-stop filters. Various kinds of filters can be realized just by changing the amount and mode of joining external current signals to the circuit. Internal structure of circuit and amount of elements need not change. So the circuit is convenient to integrated .The paper also makes PSPICE simulation for the filter.
2007, 29(1): 236-242.
doi: 10.3724/SP.J.1146.2005.00233
Abstract:
Wavelet filtering is a new research in the field of signal processing in the last decade. It has predominance over the traditional filtering methods. This paper presents the principle, model and characteristics of wavelet denoising method, basing on the analysis and synthesis of developments in this research domain in the past few years. Wavelet denoising methods are sorted into three groups and they are commented. This paper pays attention to the key points, existing problems and the thought of how to solve these problems.
Wavelet filtering is a new research in the field of signal processing in the last decade. It has predominance over the traditional filtering methods. This paper presents the principle, model and characteristics of wavelet denoising method, basing on the analysis and synthesis of developments in this research domain in the past few years. Wavelet denoising methods are sorted into three groups and they are commented. This paper pays attention to the key points, existing problems and the thought of how to solve these problems.
