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2007 Vol. 29, No. 8
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2007, 29(8): 1779-1783.
doi: 10.3724/SP.J.1146.2006.01071
Abstract:
Considering the statistical characteristics of SAR images, a novel speckle reduction algorithm is presented in this paper. This technique is by virtue of generalized cross validation and constructs an object function to acquire the asymptotic optimal threshold without of estimating noise variance. After applying the wavelet shrinkage on SAR image, cycle spinning strategy is introduced to wipe off the visible ringing effects along the edges. Numerical tests show that the proposed SAR speckle reduction algorithm provides improvements both in visual effects and quantitative analysis, which can smooth image effectively and remain the edges and texture clearly.
Considering the statistical characteristics of SAR images, a novel speckle reduction algorithm is presented in this paper. This technique is by virtue of generalized cross validation and constructs an object function to acquire the asymptotic optimal threshold without of estimating noise variance. After applying the wavelet shrinkage on SAR image, cycle spinning strategy is introduced to wipe off the visible ringing effects along the edges. Numerical tests show that the proposed SAR speckle reduction algorithm provides improvements both in visual effects and quantitative analysis, which can smooth image effectively and remain the edges and texture clearly.
2007, 29(8): 1784-1788.
doi: 10.3724/SP.J.1146.2005.01689
Abstract:
In this paper, an algorithm for compressing synthetic aperture radar raw data is proposed. This algorithm is based on the combination of discrete cosine transform and block-adaptive quantization. The known results that a block normalized SAR raw signal is a Gaussian stationary process are exploited in order to re-array the DCT coefficients. Coupled with a proper bit allocation strategy and block-adaptive quantization on re-arrayed coefficients matrix, this algorithm exhibits notably an interesting performance/complexity trade-off with respect to conventional methods such as BAQ. Simulation results on real-world SAR raw data also show that the proposed algorithm outperforms methods based on wavelets as to SNR and PSNR.
In this paper, an algorithm for compressing synthetic aperture radar raw data is proposed. This algorithm is based on the combination of discrete cosine transform and block-adaptive quantization. The known results that a block normalized SAR raw signal is a Gaussian stationary process are exploited in order to re-array the DCT coefficients. Coupled with a proper bit allocation strategy and block-adaptive quantization on re-arrayed coefficients matrix, this algorithm exhibits notably an interesting performance/complexity trade-off with respect to conventional methods such as BAQ. Simulation results on real-world SAR raw data also show that the proposed algorithm outperforms methods based on wavelets as to SNR and PSNR.
2007, 29(8): 1789-1793.
doi: 10.3724/SP.J.1146.2005.01696
Abstract:
A novel method for high speed moving targets ISAR imaging based on moving reference dechirp signal is presented in this paper. Firstly target track fitting is accomplished by utilizing assistant low-resolution range measurement results and envelope alignment for the target high-resolution range profiles. Then the target track is used for dechirp processing as a moving reference to accomplish motion compensation within a pulse period and coherent processing. Finally，Keystone transform is applied to correct the Migration Through Resolution Cells (MTRC) due to target rotation. Steps of this method for high speed moving targets are detailed. Simulations show the effectiveness of the new method.
A novel method for high speed moving targets ISAR imaging based on moving reference dechirp signal is presented in this paper. Firstly target track fitting is accomplished by utilizing assistant low-resolution range measurement results and envelope alignment for the target high-resolution range profiles. Then the target track is used for dechirp processing as a moving reference to accomplish motion compensation within a pulse period and coherent processing. Finally，Keystone transform is applied to correct the Migration Through Resolution Cells (MTRC) due to target rotation. Steps of this method for high speed moving targets are detailed. Simulations show the effectiveness of the new method.
2007, 29(8): 1794-1798.
doi: 10.3724/SP.J.1146.2005.01535
Abstract:
In view of unsteadily flying, the helicopter brings about great errors to moving targets imaging, especially SAR imaging of moving ship. So this paper shows an effective method based on an idea that uses motion compensation, general second-step keystone transform twice and at the same time, finds an isolated point and adopts WVD transform to estimate Doppler parameters for removing range walk and curvature. And what is more, the detailed deductions are given in this paper.Finally, the SAR image of moving ship is acquired in the azimuth frequency field. The simulation results of three moving point-targets and the imaging result of real ship data confirme this method.
In view of unsteadily flying, the helicopter brings about great errors to moving targets imaging, especially SAR imaging of moving ship. So this paper shows an effective method based on an idea that uses motion compensation, general second-step keystone transform twice and at the same time, finds an isolated point and adopts WVD transform to estimate Doppler parameters for removing range walk and curvature. And what is more, the detailed deductions are given in this paper.Finally, the SAR image of moving ship is acquired in the azimuth frequency field. The simulation results of three moving point-targets and the imaging result of real ship data confirme this method.
2007, 29(8): 1799-1801.
doi: 10.3724/SP.J.1146.2006.00072
Abstract:
The problem of inherent consistency between phase compensation and Minimum Entropy Auto-focusing (MEA) method in ISAR imaging is investigated in this paper. The mathematical analysis in the paper proves the conclusion that, for ISAR range-Doppler imaging, the phase compensating component probably may not be the extreme value of image entropy function when the residual translational phase is equal to zero after phase compensation being completed, and this is concerned with ISAR imaging target. Simulation experiment also shows that the residual translational phase may not surely be equal to zero to make the image entropy minimal. However only when the image entropy of target itself is not larger than those imaging entropies corresponding to any non-zero residual translational phase can the consistency be achieved between minimum entropy auto-focusing and phase compensation in ISAR imaging.
The problem of inherent consistency between phase compensation and Minimum Entropy Auto-focusing (MEA) method in ISAR imaging is investigated in this paper. The mathematical analysis in the paper proves the conclusion that, for ISAR range-Doppler imaging, the phase compensating component probably may not be the extreme value of image entropy function when the residual translational phase is equal to zero after phase compensation being completed, and this is concerned with ISAR imaging target. Simulation experiment also shows that the residual translational phase may not surely be equal to zero to make the image entropy minimal. However only when the image entropy of target itself is not larger than those imaging entropies corresponding to any non-zero residual translational phase can the consistency be achieved between minimum entropy auto-focusing and phase compensation in ISAR imaging.
2007, 29(8): 1802-1804.
doi: 10.3724/SP.J.1146.2005.01481
Abstract:
This paper introduces a method to compensate IMU air-borne SAR platform. Because GEOSTAR system error does not increase with time, GEOSTAR system and IMU to cancel IMU system errror which increases with time. It can improve precision of IMU positioning and lighten burden of motion compensation of SAR processor.
This paper introduces a method to compensate IMU air-borne SAR platform. Because GEOSTAR system error does not increase with time, GEOSTAR system and IMU to cancel IMU system errror which increases with time. It can improve precision of IMU positioning and lighten burden of motion compensation of SAR processor.
2007, 29(8): 1805-1808.
doi: 10.3724/SP.J.1146.2005.01468
Abstract:
Ultra-wide band SAR has the capability of detecting minefield and single mine from a safe standoff distance. In this paper, an ultra-wide band SAR landmine detection experimental system，referred as Rail-GPSAR system, with its information processing techniques are introduced, which is developed by the National University of Defense Technology (NUDT). It is concluded from large amounts of experiment results that the ultra-wide band SAR system can detect landmines buried under the ground.
Ultra-wide band SAR has the capability of detecting minefield and single mine from a safe standoff distance. In this paper, an ultra-wide band SAR landmine detection experimental system，referred as Rail-GPSAR system, with its information processing techniques are introduced, which is developed by the National University of Defense Technology (NUDT). It is concluded from large amounts of experiment results that the ultra-wide band SAR system can detect landmines buried under the ground.
2007, 29(8): 1809-1812.
doi: 10.3724/SP.J.1146.2005.01474
Abstract:
The sea clutter of S-band radar shows nonlinearities and time variation of its spectrum. However, the spectrum analysis method cannot reflect the evolution of the sea clutter of S-band radar in time domain. Adopting the model of Fractional Brownian Motion (FBM), this paper deduces Hurst exponent for the first time based on the observed data. Furthermore, the fractal dimension of the S-band sea clutter is also deduced. Then the largest Lyapunov exponent is obtained by Rosenstein method, which proves its chaos and fractal characteristic. Finally, the computer simulation is processed and the results prove the validity and veracity of the conclusion proposed in this paper. This conclusion provides a new approach for target detection with the S-band sea radar.
The sea clutter of S-band radar shows nonlinearities and time variation of its spectrum. However, the spectrum analysis method cannot reflect the evolution of the sea clutter of S-band radar in time domain. Adopting the model of Fractional Brownian Motion (FBM), this paper deduces Hurst exponent for the first time based on the observed data. Furthermore, the fractal dimension of the S-band sea clutter is also deduced. Then the largest Lyapunov exponent is obtained by Rosenstein method, which proves its chaos and fractal characteristic. Finally, the computer simulation is processed and the results prove the validity and veracity of the conclusion proposed in this paper. This conclusion provides a new approach for target detection with the S-band sea radar.
2007, 29(8): 1813-1816.
doi: 10.3724/SP.J.1146.2005.01518
Abstract:
Based on the characteristics of good sparsity and capturing effectively the smooth contours in natural images for Contourlet transform, a new independent component analysis algorithm is proposed by using the block-wise Contourlet transform in this paper. Experimental results show that the proposed algorithm is able to achieve a better performance in image separation.
Based on the characteristics of good sparsity and capturing effectively the smooth contours in natural images for Contourlet transform, a new independent component analysis algorithm is proposed by using the block-wise Contourlet transform in this paper. Experimental results show that the proposed algorithm is able to achieve a better performance in image separation.
2007, 29(8): 1817-1820.
doi: 10.3724/SP.J.1146.2005.01459
Abstract:
In this paper, allied strategy is introduced into PSO and a parallel and two-stage blind signal separation based on particle swarm optimization (parallel particle swarm optimizationgradient algorithm) is proposed. This algorithm is characteristic of rapid convergent speed and high separation precision. The simulation results show that this algorithm proposed is superior to particle swarm optimization in which allied strategy is not applied, and this algorithm is superior to traditional gradient algorithm and genetic algorithm in convergent speed and separation effect.
In this paper, allied strategy is introduced into PSO and a parallel and two-stage blind signal separation based on particle swarm optimization (parallel particle swarm optimizationgradient algorithm) is proposed. This algorithm is characteristic of rapid convergent speed and high separation precision. The simulation results show that this algorithm proposed is superior to particle swarm optimization in which allied strategy is not applied, and this algorithm is superior to traditional gradient algorithm and genetic algorithm in convergent speed and separation effect.
2007, 29(8): 1821-1825.
doi: 10.3724/SP.J.1146.2005.01510
Abstract:
The research of previous palmprint identification algorithms are mainly focus on ROI districts cropped from the central part of palmprint images, but always ignore the color features like grayscale distribution. Under regular illumination, the texture and skin color of different position within a palmprint image will lead to differentiable grayscale distribution. In this paper, a novel hierarchical method of palmprint identification is presented, which extracts hand geometry and angle values as the coarse-level features, and calculates the unit information entropy of each subimage to describe the images grayscale distribution as the fine-level feature. Distinctive to other identification methods existed, the proposed method do not need to extract ROI districts but utilize the skin colors distinction caused by locations of principle lines, wrinkles and minutias. The experimental results on the database containing 990 images from 99 individuals show the effectiveness and robustness of the proposed method compared with the traditional method PCA and LDA.
The research of previous palmprint identification algorithms are mainly focus on ROI districts cropped from the central part of palmprint images, but always ignore the color features like grayscale distribution. Under regular illumination, the texture and skin color of different position within a palmprint image will lead to differentiable grayscale distribution. In this paper, a novel hierarchical method of palmprint identification is presented, which extracts hand geometry and angle values as the coarse-level features, and calculates the unit information entropy of each subimage to describe the images grayscale distribution as the fine-level feature. Distinctive to other identification methods existed, the proposed method do not need to extract ROI districts but utilize the skin colors distinction caused by locations of principle lines, wrinkles and minutias. The experimental results on the database containing 990 images from 99 individuals show the effectiveness and robustness of the proposed method compared with the traditional method PCA and LDA.
2007, 29(8): 1826-1828.
doi: 10.3724/SP.J.1146.2005.01506
Abstract:
A vision inspection technique is provided, which can be used to estimate the position and orientation of the ball and its center axis hole by its projected image. When the focus length of digital camera is given, with the size of circular and spherical feature is also known, their position and/or orientation can be estimated using monocular vision. Thus, the ball pose is acquired from several spherical and circular features shaped by the contour of the ball and its axis. Besides, with the existence of image noise and fitting error of the projection ellipses, the solution base on sole feature is not concurrent with each other. The non-linear least squares algorithm is used to refine above rough solutions and to improve the estimate precise。Experiments with simulated data as well as real image is also presented to validate the algorithms.
A vision inspection technique is provided, which can be used to estimate the position and orientation of the ball and its center axis hole by its projected image. When the focus length of digital camera is given, with the size of circular and spherical feature is also known, their position and/or orientation can be estimated using monocular vision. Thus, the ball pose is acquired from several spherical and circular features shaped by the contour of the ball and its axis. Besides, with the existence of image noise and fitting error of the projection ellipses, the solution base on sole feature is not concurrent with each other. The non-linear least squares algorithm is used to refine above rough solutions and to improve the estimate precise。Experiments with simulated data as well as real image is also presented to validate the algorithms.
2007, 29(8): 1829-1832.
doi: 10.3724/SP.J.1146.2006.00037
Abstract:
Detection of long range targets in thermal infrared image sequences is of interest in many applications such as military field and surveillance system. Incoming targets at long range where the motion is small and signal to noise is poor are difficult to detect in cluttered thermal infrared image sequences. In this paper, long range target detection in cluttered thermal infrared image sequences is presented. At first, possible targets are detected using top-hat detector in thermal infrared video. Next, motion feature is analyzed by measure the correlation of a target in different frames. Targets with reasonable motion characteristics are decided as long range moving target. In the proposed method background estimation is not needed and heavy noise could be avoided. By modify motion model, targets with different motion features could be detected. Experiments show that the proposed method is feasible and robust.
Detection of long range targets in thermal infrared image sequences is of interest in many applications such as military field and surveillance system. Incoming targets at long range where the motion is small and signal to noise is poor are difficult to detect in cluttered thermal infrared image sequences. In this paper, long range target detection in cluttered thermal infrared image sequences is presented. At first, possible targets are detected using top-hat detector in thermal infrared video. Next, motion feature is analyzed by measure the correlation of a target in different frames. Targets with reasonable motion characteristics are decided as long range moving target. In the proposed method background estimation is not needed and heavy noise could be avoided. By modify motion model, targets with different motion features could be detected. Experiments show that the proposed method is feasible and robust.
2007, 29(8): 1833-1836.
doi: 10.3724/SP.J.1146.2006.00100
Abstract:
Large tracking error has been found in the use of classic extended Kalman filter in LOS/NLOS hybrid environment. This paper presents a modified particle filter algorithm based on the LOS/NLOS binary state information of propagation environment using the numerical method of the Probability Density Function (PDF) about the hybrid noise. Simulation results show that the new scheme integrated the LOS/NLOS environment information and the hybrid noise density can improve the tracking estimation accuracy effectively.
Large tracking error has been found in the use of classic extended Kalman filter in LOS/NLOS hybrid environment. This paper presents a modified particle filter algorithm based on the LOS/NLOS binary state information of propagation environment using the numerical method of the Probability Density Function (PDF) about the hybrid noise. Simulation results show that the new scheme integrated the LOS/NLOS environment information and the hybrid noise density can improve the tracking estimation accuracy effectively.
2007, 29(8): 1837-1840.
doi: 10.3724/SP.J.1146.2006.00015
Abstract:
To maneuvering target tracking with multiple passive sensors in clutter environment, a novel algorithm based on particle filter is proposed. In this algorithm, the likelihood function of particle filter in clutter is derived. Then the particle filter and Interactive Multiple Model (IMM) method are integrated. The former solves the proplem of passive target manoeuvre and the latter deals with the nonlinear problem of the measurement equation. In order to avoid the unobservability problem of passive target tracking, a nonlinear measurement model of multiple passive sensors is founded, and the algorithm can deal with the case of non-gaussian noise. Finally, the simulation results show that the proposed algorithm is effective, and its performance is superiority over the interacting multiple model-probabilistic data association filter (IMM-PDAF).
To maneuvering target tracking with multiple passive sensors in clutter environment, a novel algorithm based on particle filter is proposed. In this algorithm, the likelihood function of particle filter in clutter is derived. Then the particle filter and Interactive Multiple Model (IMM) method are integrated. The former solves the proplem of passive target manoeuvre and the latter deals with the nonlinear problem of the measurement equation. In order to avoid the unobservability problem of passive target tracking, a nonlinear measurement model of multiple passive sensors is founded, and the algorithm can deal with the case of non-gaussian noise. Finally, the simulation results show that the proposed algorithm is effective, and its performance is superiority over the interacting multiple model-probabilistic data association filter (IMM-PDAF).
2007, 29(8): 1841-1844.
doi: 10.3724/SP.J.1146.2006.00104
Abstract:
A method for the recovery of JPEG compressed image sequences is proposed in this paper. The method is based on the reduction of compression artifacts, and it is inspired with the thoughts of super-resolution reconstruction. To minimize the quantization errors and restore the discrete cosine transformation components, the method utilizes the theory of Projection Onto Convex Sets (POCS) and Iterative Back Projection (IBP) algorithm, which helps computing the projections. It also applies Maximum A Posteriori (MAP) estimation techniques to remove Gaussian noise without damaging edges or details of the image. Experimental results show that the proposed method produces good Peak Signal to Noise Ratio (PSNR) results, and could not only remove blocking and ringing artifacts, but also recover details of images, especially in low bit-rate conditions.
A method for the recovery of JPEG compressed image sequences is proposed in this paper. The method is based on the reduction of compression artifacts, and it is inspired with the thoughts of super-resolution reconstruction. To minimize the quantization errors and restore the discrete cosine transformation components, the method utilizes the theory of Projection Onto Convex Sets (POCS) and Iterative Back Projection (IBP) algorithm, which helps computing the projections. It also applies Maximum A Posteriori (MAP) estimation techniques to remove Gaussian noise without damaging edges or details of the image. Experimental results show that the proposed method produces good Peak Signal to Noise Ratio (PSNR) results, and could not only remove blocking and ringing artifacts, but also recover details of images, especially in low bit-rate conditions.
2007, 29(8): 1845-1849.
doi: 10.3724/SP.J.1146.2006.00137
Abstract:
A system on the layout of objects in a 3D scene is researched and designed in the paper to realize the automatic layout. The system is based on natural language understanding and realized through two steps. Three contents are described in this paper. The first part is how to identify the space relations between objects described in the text based on linear classifier; the second is to qualify the zone of objects based on boxes (the first step); and the last is to layout objects in 3D scene based on generic algorithm (the second step). Finally, the experiments are given. It is proved that the method is satisfactory.
A system on the layout of objects in a 3D scene is researched and designed in the paper to realize the automatic layout. The system is based on natural language understanding and realized through two steps. Three contents are described in this paper. The first part is how to identify the space relations between objects described in the text based on linear classifier; the second is to qualify the zone of objects based on boxes (the first step); and the last is to layout objects in 3D scene based on generic algorithm (the second step). Finally, the experiments are given. It is proved that the method is satisfactory.
2007, 29(8): 1850-1854.
doi: 10.3724/SP.J.1146.2005.01471
Abstract:
For the multisensor system with unknown noise statistics, and with the measurement matrices having a same right factor, based on Weighted Least Squares(WLS) method, an equivalent fusion measurement equation is obtained. Using the modern time series analysis method, based on on-line identification of the innovation model parameters, unknown noise variances can be estimated, and a self-tuning weighted measurement fusion Kalman filter is presented. Under the assumptions that the parameter estimation of the innovation model is consistent and the measurement data are bounded, it is proved that the self-tuning Kalman filter converges to globally optimal fusion Kalman filter with known noise statistics, so that it has asymptotic global optimality. A simulation example for a tracking system with 4-sensor shows its effectiveness.
For the multisensor system with unknown noise statistics, and with the measurement matrices having a same right factor, based on Weighted Least Squares(WLS) method, an equivalent fusion measurement equation is obtained. Using the modern time series analysis method, based on on-line identification of the innovation model parameters, unknown noise variances can be estimated, and a self-tuning weighted measurement fusion Kalman filter is presented. Under the assumptions that the parameter estimation of the innovation model is consistent and the measurement data are bounded, it is proved that the self-tuning Kalman filter converges to globally optimal fusion Kalman filter with known noise statistics, so that it has asymptotic global optimality. A simulation example for a tracking system with 4-sensor shows its effectiveness.
2007, 29(8): 1855-1859.
doi: 10.3724/SP.J.1146.2006.00014
Abstract:
The methods of similarity measure between vague values (sets) in existence, some errors and limitations in some former result are analyzed. A new definition of similarity measure between values (sets) is presented, and two ameliorative similarity measures between values (sets) are presented. Finally，the ameliorative similarity measures between values (sets) are validated with experimental data.
The methods of similarity measure between vague values (sets) in existence, some errors and limitations in some former result are analyzed. A new definition of similarity measure between values (sets) is presented, and two ameliorative similarity measures between values (sets) are presented. Finally，the ameliorative similarity measures between values (sets) are validated with experimental data.
2007, 29(8): 1860-1863.
doi: 10.3724/SP.J.1146.2005.01480
Abstract:
The signal is done un-decimated wavelet transform using Anti-Symmetrical Biorthogonal Wavelets (ASBW). Because of the ASBWs approximate derivative property, the local maxima of the wavelet decomposition coefficients can be obtained, which is the corresponding edge of the signal at every scale. Only keeping the local maxima, the Gaussian function is used to fit the wavelet coefficients directly, then inverse wavelet translation is used to reconstruct signal. Numerical results show that the reconstruction algorithm is much faster than the dyadic wavelet translation.
The signal is done un-decimated wavelet transform using Anti-Symmetrical Biorthogonal Wavelets (ASBW). Because of the ASBWs approximate derivative property, the local maxima of the wavelet decomposition coefficients can be obtained, which is the corresponding edge of the signal at every scale. Only keeping the local maxima, the Gaussian function is used to fit the wavelet coefficients directly, then inverse wavelet translation is used to reconstruct signal. Numerical results show that the reconstruction algorithm is much faster than the dyadic wavelet translation.
2007, 29(8): 1864-1867.
doi: 10.3724/SP.J.1146.2005.01465
Abstract:
Compared with Gaussian noise, Heavy-tailed noise has more outliers, and the traditional neural network can not suppress outliers. A new neural network based on median filter is proposed. After suppressing the outliers in signal through median filter, the BP (Back Propagation) is used and remained noise is eliminated further. The experiment based on the error analyses shows that compared with the traditional neural network, the proposed method can suppress heavy-tailed noise and detect target signal more effectively. It can perform well for both heavy-tailed noise and Gaussian noise background, which shows its robustness and adaptiveness.
Compared with Gaussian noise, Heavy-tailed noise has more outliers, and the traditional neural network can not suppress outliers. A new neural network based on median filter is proposed. After suppressing the outliers in signal through median filter, the BP (Back Propagation) is used and remained noise is eliminated further. The experiment based on the error analyses shows that compared with the traditional neural network, the proposed method can suppress heavy-tailed noise and detect target signal more effectively. It can perform well for both heavy-tailed noise and Gaussian noise background, which shows its robustness and adaptiveness.
2007, 29(8): 1868-1871.
doi: 10.3724/SP.J.1146.2006.00117
Abstract:
A new algorithm for detecting P-wave is proposed by an adaptive QRS-T cancellation technique based on wavelet transform. In this paper, Mallat algorithm of the Marr wavelet transforms is used to prosecute multi-resolution analysis for the ECG signal, for each scale, only the local extrema of the transformation are kept while the other values are set equal to zero. Then QRS waves are located based on modulus maximum values, and QT interval is estimated subsequently. The QRS-T adaptive cancellation is conducted in the transformed domain by keeping only the DWT extrema present outside the QRS-T interval. The residual signal including the P wave is magnified by the nonlinear transform, and P wave position is achieved by the adaptive threshold detection of modulus maximum values. This method is used to detect the P-wave of ECG data from MIT-BIH, and got satisfactory results.
A new algorithm for detecting P-wave is proposed by an adaptive QRS-T cancellation technique based on wavelet transform. In this paper, Mallat algorithm of the Marr wavelet transforms is used to prosecute multi-resolution analysis for the ECG signal, for each scale, only the local extrema of the transformation are kept while the other values are set equal to zero. Then QRS waves are located based on modulus maximum values, and QT interval is estimated subsequently. The QRS-T adaptive cancellation is conducted in the transformed domain by keeping only the DWT extrema present outside the QRS-T interval. The residual signal including the P wave is magnified by the nonlinear transform, and P wave position is achieved by the adaptive threshold detection of modulus maximum values. This method is used to detect the P-wave of ECG data from MIT-BIH, and got satisfactory results.
2007, 29(8): 1872-1876.
doi: 10.3724/SP.J.1146.2005.01457
Abstract:
Combing space-time trellis codes and layered space-time codes, a new Generalized Recursive Space-Time Trellis Code(G-RSTTC) is designed for a Serial Concatenated Space-Time Code(SCSTC). Compared with SCSTC using the traditional recursive STTC as the inner code, the G-RSTTC based SCSTC can increase the data rate with the increase of the transmit antenna number. Compared with the SCSTC using BLAST as the inner code, the G-RSTTC based SCSTC achieve higher diversity gains and coding gains.
Combing space-time trellis codes and layered space-time codes, a new Generalized Recursive Space-Time Trellis Code(G-RSTTC) is designed for a Serial Concatenated Space-Time Code(SCSTC). Compared with SCSTC using the traditional recursive STTC as the inner code, the G-RSTTC based SCSTC can increase the data rate with the increase of the transmit antenna number. Compared with the SCSTC using BLAST as the inner code, the G-RSTTC based SCSTC achieve higher diversity gains and coding gains.
2007, 29(8): 1877-1881.
doi: 10.3724/SP.J.1146.2005.01656
Abstract:
In this paper, a unified model of the random impulse radio signals is presented based on the characters of a variety of UWB modulation signals. The Power Spectral Density(PSD)for the signals is carried out using stochastic theory. This PSD expression is used widely, such as for various modulation forms, various multi-access forms, either binary or M-ary systems. The PSD expressions for several typical modulation signals with or without the uniformly distributed timing jitter are taken for example and analyzed in details. The results show that the timing jitter smoothes the spectrum and alleviates the interferences on other narrowband communication systems. Furthermore, the results can be used to estimate the effect of changes in various parameters on PSD of transmitted signal, without going through the detailed design procedure.
In this paper, a unified model of the random impulse radio signals is presented based on the characters of a variety of UWB modulation signals. The Power Spectral Density(PSD)for the signals is carried out using stochastic theory. This PSD expression is used widely, such as for various modulation forms, various multi-access forms, either binary or M-ary systems. The PSD expressions for several typical modulation signals with or without the uniformly distributed timing jitter are taken for example and analyzed in details. The results show that the timing jitter smoothes the spectrum and alleviates the interferences on other narrowband communication systems. Furthermore, the results can be used to estimate the effect of changes in various parameters on PSD of transmitted signal, without going through the detailed design procedure.
2007, 29(8): 1882-1886.
doi: 10.3724/SP.J.1146.2005.01693
Abstract:
This paper proposes an identification algorithm for higher order QAM modulated signals based on the improved HY-NCMA blind equalization method in multi-path environments. Compared with the existing algorithms, the equalizer can recover the phase offset and have faster convergence, furthermore, not only are the sample size and the complexity of the proposed algorithm reduced, but also the identification rate is improved by means of the new identification feature. Simulation results demonstrate the efficiency of the modulation identification at middle or high SNR (Signal to Noise Ratio).
This paper proposes an identification algorithm for higher order QAM modulated signals based on the improved HY-NCMA blind equalization method in multi-path environments. Compared with the existing algorithms, the equalizer can recover the phase offset and have faster convergence, furthermore, not only are the sample size and the complexity of the proposed algorithm reduced, but also the identification rate is improved by means of the new identification feature. Simulation results demonstrate the efficiency of the modulation identification at middle or high SNR (Signal to Noise Ratio).
2007, 29(8): 1887-1890.
doi: 10.3724/SP.J.1146.2005.01464
Abstract:
A turbo equalizer is able to overcome severe inter-symbol-interferences because it benefits from the channel decoding gain by iteratively performing equalization and channel decoding. This paper proposes a scheme of turbo equalization and iterative channel estimation for blind receiver. The scheme exploits a conventional blind equalizer to bootstrap the iterative process and thus is independent of training sequence and a priori information of the transmitted symbols. In such a scheme, the initial blind equalization algorithm is critical and should be able to provide enough information for the following turbo equalization and channel estimation even when channel distortion is severe. Based on analysis of characteristics of turbo equalization, the super exponential algorithm is chosen as the initial blind equalization. Simulation results illustrating performance of the proposed scheme are also given.
A turbo equalizer is able to overcome severe inter-symbol-interferences because it benefits from the channel decoding gain by iteratively performing equalization and channel decoding. This paper proposes a scheme of turbo equalization and iterative channel estimation for blind receiver. The scheme exploits a conventional blind equalizer to bootstrap the iterative process and thus is independent of training sequence and a priori information of the transmitted symbols. In such a scheme, the initial blind equalization algorithm is critical and should be able to provide enough information for the following turbo equalization and channel estimation even when channel distortion is severe. Based on analysis of characteristics of turbo equalization, the super exponential algorithm is chosen as the initial blind equalization. Simulation results illustrating performance of the proposed scheme are also given.
2007, 29(8): 1891-1894.
doi: 10.3724/SP.J.1146.2006.00067
Abstract:
First, this paper analyzes the very reason of efficiency in the existing efficient architecture for wideband Digital Down Conversion (DDC) and points out some problems, and then deduces a novel method: decimation prior to filtering and synchro-tuning by the use of Goertzel filter. By comparing it with the typical architecture and the existing efficient architecture for wideband DDC, performance of new method is discussed to be flexible, efficient and finite cost. Computer simulation illustrates its feasibility.
First, this paper analyzes the very reason of efficiency in the existing efficient architecture for wideband Digital Down Conversion (DDC) and points out some problems, and then deduces a novel method: decimation prior to filtering and synchro-tuning by the use of Goertzel filter. By comparing it with the typical architecture and the existing efficient architecture for wideband DDC, performance of new method is discussed to be flexible, efficient and finite cost. Computer simulation illustrates its feasibility.
2007, 29(8): 1895-1899.
doi: 10.3724/SP.J.1146.2005.01707
Abstract:
A robust blind symbol-timing synchronization scheme applicable to UWB-OFDM systems is presented. The proposed method is based on ZP(Zero-padded Prefix) power collection in the UWB-OFDM symbols whose ZP average power distribute regularly in the slide windows. The synchronization schemes in both Gaussian channel and UWB channel are investigated. Average power distribution of the received signal in UWB channel is analysed detailedly in order that symbol synchronizes accurately. A multi_slide_windows method is designed in order to improve the performance of synchronization. Finally computer results are also demonstrate the superior performance of the new method in both Gaussian channel and UWB channel.
A robust blind symbol-timing synchronization scheme applicable to UWB-OFDM systems is presented. The proposed method is based on ZP(Zero-padded Prefix) power collection in the UWB-OFDM symbols whose ZP average power distribute regularly in the slide windows. The synchronization schemes in both Gaussian channel and UWB channel are investigated. Average power distribution of the received signal in UWB channel is analysed detailedly in order that symbol synchronizes accurately. A multi_slide_windows method is designed in order to improve the performance of synchronization. Finally computer results are also demonstrate the superior performance of the new method in both Gaussian channel and UWB channel.
2007, 29(8): 1900-1902.
doi: 10.3724/SP.J.1146.2006.00212
Abstract:
An algorithm of improved reduced spatial resolution video transcoding is proposed in this paper. An adaptive intra-refresh scheme is presented based on the relation between drift error and motion activity of inter-coded blocks. The thresholds are dynamically adjusted according to the difference between the target bit rate and actual bit rate. This method can reduce the bit rate of intra coded frames while still maintating error robustness and limiting temporal propagation of errors. Besides, a linear rate control strategy is also present. In order to reduce computational complexity, the rate-distortion function can be mapped into a linear function. The simulation results show that the buffer fullness tend to be stabilized and the PSNR of the reconstructed image is raised.
An algorithm of improved reduced spatial resolution video transcoding is proposed in this paper. An adaptive intra-refresh scheme is presented based on the relation between drift error and motion activity of inter-coded blocks. The thresholds are dynamically adjusted according to the difference between the target bit rate and actual bit rate. This method can reduce the bit rate of intra coded frames while still maintating error robustness and limiting temporal propagation of errors. Besides, a linear rate control strategy is also present. In order to reduce computational complexity, the rate-distortion function can be mapped into a linear function. The simulation results show that the buffer fullness tend to be stabilized and the PSNR of the reconstructed image is raised.
2007, 29(8): 1903-1905.
doi: 10.3724/SP.J.1146.2006.00431
Abstract:
Time-Division Duplex (TDD) and Multiple-Input Multiple-Output (MIMO) are the key techniques in the beyond third generation (B3G) mobile communication systems. In the conventional literatures on TDD, the channel state information at transmitter is obtained by assuming the reciprocity between uplink and downlink. However, affected by the unbalance of the Radio-Frequency (RF) circuitries in practice, the reciprocity between uplink and downlink can not be maintained, which will cause a decrease of the performance. In this paper, the asymmetry effect is analyzed in detail and the RF feedback strategy is proposed to eliminate it. Simulation results show that the RF feedback strategy performs much better than the conventional uplink reuse and the capacity of the MIMO systems is greatly improved.
Time-Division Duplex (TDD) and Multiple-Input Multiple-Output (MIMO) are the key techniques in the beyond third generation (B3G) mobile communication systems. In the conventional literatures on TDD, the channel state information at transmitter is obtained by assuming the reciprocity between uplink and downlink. However, affected by the unbalance of the Radio-Frequency (RF) circuitries in practice, the reciprocity between uplink and downlink can not be maintained, which will cause a decrease of the performance. In this paper, the asymmetry effect is analyzed in detail and the RF feedback strategy is proposed to eliminate it. Simulation results show that the RF feedback strategy performs much better than the conventional uplink reuse and the capacity of the MIMO systems is greatly improved.
2007, 29(8): 1906-1910.
doi: 10.3724/SP.J.1146.2005.01691
Abstract:
This paper proposes a subspace-based semiblind channel estimation method in MC-CDMA systems. Combined with the characteristic of the signal model in MC-CDMA systems, this semiblind method solves the problem of slow convergence by the initial channel estimation, estimates the scalar ambiguities by inserting some users pilots and makes the algorithm complexity low by an iterative operation. All of these make the reality of semiblind channel estimation to be possible. The results of computer simulation prove the correctness of the method.
This paper proposes a subspace-based semiblind channel estimation method in MC-CDMA systems. Combined with the characteristic of the signal model in MC-CDMA systems, this semiblind method solves the problem of slow convergence by the initial channel estimation, estimates the scalar ambiguities by inserting some users pilots and makes the algorithm complexity low by an iterative operation. All of these make the reality of semiblind channel estimation to be possible. The results of computer simulation prove the correctness of the method.
2007, 29(8): 1911-1915.
doi: 10.3724/SP.J.1146.2006.01512
Abstract:
Based on the performance analysis of the Orthogonal Frequency Division Multiplexing (OFDM) system, this paper proposes a scheme for sub-carrier allocation and power control in a multi-user multi-rate OFDM system. For the downlink transmission employing P-QAM, if all Channel State Information (CSI) are known, under the constraint of the Quality of Service (QoS) of each user being satisfied, the CBR (Constant Bit Rate) users are allocated with channels prior to the VBR (Variable Bit Rate) users. The VBR users are allocated with remain channels with the rule of link gain maximization. Signal powers are assigned with the water-filling policy: the larger is the link gain of the sub-channel, the more power is assigned. Simulation results show that the proposed sub-carrier allocation and power distribution scheme can achieve higher system capacity than Jangs method.
Based on the performance analysis of the Orthogonal Frequency Division Multiplexing (OFDM) system, this paper proposes a scheme for sub-carrier allocation and power control in a multi-user multi-rate OFDM system. For the downlink transmission employing P-QAM, if all Channel State Information (CSI) are known, under the constraint of the Quality of Service (QoS) of each user being satisfied, the CBR (Constant Bit Rate) users are allocated with channels prior to the VBR (Variable Bit Rate) users. The VBR users are allocated with remain channels with the rule of link gain maximization. Signal powers are assigned with the water-filling policy: the larger is the link gain of the sub-channel, the more power is assigned. Simulation results show that the proposed sub-carrier allocation and power distribution scheme can achieve higher system capacity than Jangs method.
2007, 29(8): 1916-1918.
doi: 10.3724/SP.J.1146.2006.00062
Abstract:
An improved anti-frequency-offset method by windowing in OFDM systems is proposed. The cyclic prefix added at the transmitter side is first removed at the receiver, and then a new cyclic prefix is appended, finally the new signal is windowed by a Nyquist window, which is optimized numerical solution. Numerical results show that the anti-frequency-offset capability of the optimized window is much better than other windows.
An improved anti-frequency-offset method by windowing in OFDM systems is proposed. The cyclic prefix added at the transmitter side is first removed at the receiver, and then a new cyclic prefix is appended, finally the new signal is windowed by a Nyquist window, which is optimized numerical solution. Numerical results show that the anti-frequency-offset capability of the optimized window is much better than other windows.
2007, 29(8): 1919-1923.
doi: 10.3724/SP.J.1146.2005.01569
Abstract:
A novel system based on cooperative Distributed Space-Time Block Code and Multi-Carrier Code Division Multiple Access (DSTBC-MC-CDMA) is presented which works well in multi-user wireless networks with single-antenna user in frequency selective fading channel. And an analytical model for describing the symbol decoding error between the interusers is established to analyze the qualitative influence to the bit error rate (BER) performance of the system. Then the simulation is complimented to versify the analytic result above, and the diagrams also show that the BER performance of DSTBC-MC-CDMA outgoes MC-CDMA with distinctive gains.
A novel system based on cooperative Distributed Space-Time Block Code and Multi-Carrier Code Division Multiple Access (DSTBC-MC-CDMA) is presented which works well in multi-user wireless networks with single-antenna user in frequency selective fading channel. And an analytical model for describing the symbol decoding error between the interusers is established to analyze the qualitative influence to the bit error rate (BER) performance of the system. Then the simulation is complimented to versify the analytic result above, and the diagrams also show that the BER performance of DSTBC-MC-CDMA outgoes MC-CDMA with distinctive gains.
2007, 29(8): 1924-1928.
doi: 10.3724/SP.J.1146.2006.00763
Abstract:
In orthogonal frequency-division multiple access (OFDMA), closely spaced multiple subcarrier are assigned to different users for parallel signal transmission. An interleaved subcarrier-assignment scheme is preferred because it provides maximum frequency diversity and increases the capacity in frequency-selective fading channels. Carrier-frequency offsets (CFOs) between the transmitter and the receiver destroy the orthogonality and introduce Inter-Carrier Interferences (ICI) and Multi-User Interferences (MUI). In this paper, the signal structure at the Interleaved-OFDMA uplink is first present. Then a CFO compensation method for the system, which uses adaptive beamformer, is proposed as an alternative to the circular convolution method. And two adaptive beamformers, i.e. matched filter and MMSE method are introduced. Simulation results indicate that the MMSE beamformer outperforms the matched filter and the circular convolution method.
In orthogonal frequency-division multiple access (OFDMA), closely spaced multiple subcarrier are assigned to different users for parallel signal transmission. An interleaved subcarrier-assignment scheme is preferred because it provides maximum frequency diversity and increases the capacity in frequency-selective fading channels. Carrier-frequency offsets (CFOs) between the transmitter and the receiver destroy the orthogonality and introduce Inter-Carrier Interferences (ICI) and Multi-User Interferences (MUI). In this paper, the signal structure at the Interleaved-OFDMA uplink is first present. Then a CFO compensation method for the system, which uses adaptive beamformer, is proposed as an alternative to the circular convolution method. And two adaptive beamformers, i.e. matched filter and MMSE method are introduced. Simulation results indicate that the MMSE beamformer outperforms the matched filter and the circular convolution method.
2007, 29(8): 1929-1933.
doi: 10.3724/SP.J.1146.2006.00237
Abstract:
Distributed noncooperative power control game for wireless data is considered in multiple-input multiple-output (MIMO) CDMA system. Utility functions are established for wireless data over the MIMO CDMA system. The spectral efficiency and power efficiency are both referred to as utility which reflects the level of satisfaction a data user gets. According to the utility functions, two noncooperative power control games are developed, and establish the existence, uniqueness of the Nash equilibria of them. The pricing mechanism is studied for the power control games. We also present power control algorithms to get the Nash equilibria and analyze the performance of the proposed power control games.
Distributed noncooperative power control game for wireless data is considered in multiple-input multiple-output (MIMO) CDMA system. Utility functions are established for wireless data over the MIMO CDMA system. The spectral efficiency and power efficiency are both referred to as utility which reflects the level of satisfaction a data user gets. According to the utility functions, two noncooperative power control games are developed, and establish the existence, uniqueness of the Nash equilibria of them. The pricing mechanism is studied for the power control games. We also present power control algorithms to get the Nash equilibria and analyze the performance of the proposed power control games.
2007, 29(8): 1934-1937.
doi: 10.3724/SP.J.1146.2006.00118
Abstract:
The samples of stochastic bridge processes are employed to model propagation trajectories of Multi-Path Components (MPCs) in short range wireless propagation channels. Under some specialized mapping rules, the basic random variables constructed from samples of stochastic bridge processes are used to model the parameters of space-time channels, such as time delay, gains, direction-of-arrivals, etc. The Brownian bridge process, as a special example of stochastic bridge processes, is utilized to simulate the space-time characteristics both in the environment filled with scatterers randomly and in the special bounded propagation environment. The simulation results demonstrate that the direction-of-arrival of MPCs described by the elevation and the azimuth are slightly locally favorable in two propagation environment. Their distribution can not be regarded as uniform. And there is some regularity in the domain of elevation-azimuth-time delay.
The samples of stochastic bridge processes are employed to model propagation trajectories of Multi-Path Components (MPCs) in short range wireless propagation channels. Under some specialized mapping rules, the basic random variables constructed from samples of stochastic bridge processes are used to model the parameters of space-time channels, such as time delay, gains, direction-of-arrivals, etc. The Brownian bridge process, as a special example of stochastic bridge processes, is utilized to simulate the space-time characteristics both in the environment filled with scatterers randomly and in the special bounded propagation environment. The simulation results demonstrate that the direction-of-arrival of MPCs described by the elevation and the azimuth are slightly locally favorable in two propagation environment. Their distribution can not be regarded as uniform. And there is some regularity in the domain of elevation-azimuth-time delay.
2007, 29(8): 1938-1941.
doi: 10.3724/SP.J.1146.2006.00038
Abstract:
Ultra-wideband communication system is generally organized in the form of Ad hoc network. In this paper, two strategies of admission controlthe throughput control on overall network or each link, are simply analyzed for Ad hoc network which uses DS-UWB technology as PHY layer. According to the requirements of Quality of Service (QoS) on each link, the number of admitted users in the networks is simulated under perfect power control. It shows that the factors affecting the quality of links such as the periods of orthogonal code and signal to noise ratio have large influence on the number of the admitted users in the UWB Ad hoc networks.
Ultra-wideband communication system is generally organized in the form of Ad hoc network. In this paper, two strategies of admission controlthe throughput control on overall network or each link, are simply analyzed for Ad hoc network which uses DS-UWB technology as PHY layer. According to the requirements of Quality of Service (QoS) on each link, the number of admitted users in the networks is simulated under perfect power control. It shows that the factors affecting the quality of links such as the periods of orthogonal code and signal to noise ratio have large influence on the number of the admitted users in the UWB Ad hoc networks.
2007, 29(8): 1942-1945.
doi: 10.3724/SP.J.1146.2005.01637
Abstract:
The article provides applying DSTC(Deskewed Short-Time Correlator)to code acquisition system on serious code frequency offset. Firstly, performance of acquisition system affected by code frequency offset is analyzed. Considering complication and performance of algorithm, code frequency offset is compensated by using DSTC. Secondly, specific and realizable solution of code acquisition system is given. Finally, probability of detection of acquisition system before applying DSTC is compared with that after applying DSTC, And it is confirmed that applying DSTC can greatly improve probability of detection, which is important for code acquisition in low signal-to-noise rate.
The article provides applying DSTC(Deskewed Short-Time Correlator)to code acquisition system on serious code frequency offset. Firstly, performance of acquisition system affected by code frequency offset is analyzed. Considering complication and performance of algorithm, code frequency offset is compensated by using DSTC. Secondly, specific and realizable solution of code acquisition system is given. Finally, probability of detection of acquisition system before applying DSTC is compared with that after applying DSTC, And it is confirmed that applying DSTC can greatly improve probability of detection, which is important for code acquisition in low signal-to-noise rate.
2007, 29(8): 1946-1950.
doi: 10.3724/SP.J.1146.2006.00058
Abstract:
This paper proposes a Path Based-Optimized Shared-Protection algorithm for Multicast sessions (PB-OSPM) against single link failure in WDM mesh networks. Based on the Optimal Path-Pair-based Shared Disjoint Paths (OPP-SDP) algorithm, PB-OSPM introduces wavelength usage matrix and wavelength reservation matrix to record the detailed usage of wavelengths reserved in the past so that the sharing of reserved wavelengths between protection paths of different multicast sessions can be enabled if the paths are not going to act at the same time. Study uses the topology of European Optical Network (EON) to simulate the network redundancy with an increasing network load and the blocking probability under various conditions of wavelength resources and dynamic network loads. The simulation results demonstrate the superiority of PB-OSPM over OPP-SDP and prove sharing wavelengths between different multicast sessions to be an effective way to improve wavelength usage.
This paper proposes a Path Based-Optimized Shared-Protection algorithm for Multicast sessions (PB-OSPM) against single link failure in WDM mesh networks. Based on the Optimal Path-Pair-based Shared Disjoint Paths (OPP-SDP) algorithm, PB-OSPM introduces wavelength usage matrix and wavelength reservation matrix to record the detailed usage of wavelengths reserved in the past so that the sharing of reserved wavelengths between protection paths of different multicast sessions can be enabled if the paths are not going to act at the same time. Study uses the topology of European Optical Network (EON) to simulate the network redundancy with an increasing network load and the blocking probability under various conditions of wavelength resources and dynamic network loads. The simulation results demonstrate the superiority of PB-OSPM over OPP-SDP and prove sharing wavelengths between different multicast sessions to be an effective way to improve wavelength usage.
2007, 29(8): 1951-1955.
doi: 10.3724/SP.J.1146.2005.01503
Abstract:
Optical Burst Switching (OBS) is a promising paradigm for the next-generation internet infrastructure. Based on analyzing the influence of the special transmission mode in Optical Burst Switching (OBS) networks upon the performance of TCP, this paper studies the impact of the number of TCP/IP packets of same connection assembled in one burst on the performance of TCP Reno throughput. A closed form equation is obtained which represents the relationship between the throughput and the burst loss rate, number of TCP/IP packets contained in one burst, and the Round Trip Time (RTT). The correctness of the analysis is then tested by simulation. Both the results of analysis and simulation show that an optimum number of TCP/IP packets of same connection assembled in one burst exists to make the TCP throughput maximum when the access link bandwidth is relatively large.
Optical Burst Switching (OBS) is a promising paradigm for the next-generation internet infrastructure. Based on analyzing the influence of the special transmission mode in Optical Burst Switching (OBS) networks upon the performance of TCP, this paper studies the impact of the number of TCP/IP packets of same connection assembled in one burst on the performance of TCP Reno throughput. A closed form equation is obtained which represents the relationship between the throughput and the burst loss rate, number of TCP/IP packets contained in one burst, and the Round Trip Time (RTT). The correctness of the analysis is then tested by simulation. Both the results of analysis and simulation show that an optimum number of TCP/IP packets of same connection assembled in one burst exists to make the TCP throughput maximum when the access link bandwidth is relatively large.
2007, 29(8): 1956-1960.
doi: 10.3724/SP.J.1146.2005.01649
Abstract:
The concept of DTN (Delay-Tolerant Network) is abstracted from many new emerging network instances, which experience frequent long-duration partitions. This particular topology feature makes DTNs routing mechanism very different from typical Internet, in which the existence of a path from source to destination is always guaranteed. This paper focuses on one of DTNs routing algorithmED(Earliest-Delivery). A Time-Precision factor is employed to modify the cost of a contact, and then a new algorithm named AED(Advanced ED) is introduced. Otherwise, this paper describes a new stochastic process model that is used to implement AED.
The concept of DTN (Delay-Tolerant Network) is abstracted from many new emerging network instances, which experience frequent long-duration partitions. This particular topology feature makes DTNs routing mechanism very different from typical Internet, in which the existence of a path from source to destination is always guaranteed. This paper focuses on one of DTNs routing algorithmED(Earliest-Delivery). A Time-Precision factor is employed to modify the cost of a contact, and then a new algorithm named AED(Advanced ED) is introduced. Otherwise, this paper describes a new stochastic process model that is used to implement AED.
2007, 29(8): 1961-1965.
doi: 10.3724/SP.J.1146.2005.01654
Abstract:
The multi-layers handover in communication based on IMS(IP Multimedia Subsystem)results in the long interruption time of application, which reduces the Quality of Service (QoS) of the system. The process of handover signaling in R6 adopts the handover between SGSNs when one MS moves from one network to another, which will lead to the bypass of the data among the networks and will aspect the efficient of the handover and add the network traffic. The process of handover is improved by a hander between GGSN. It can fast the handover process and reduce the end-to-end delay for the roaming MS and the traffic of the network.
The multi-layers handover in communication based on IMS(IP Multimedia Subsystem)results in the long interruption time of application, which reduces the Quality of Service (QoS) of the system. The process of handover signaling in R6 adopts the handover between SGSNs when one MS moves from one network to another, which will lead to the bypass of the data among the networks and will aspect the efficient of the handover and add the network traffic. The process of handover is improved by a hander between GGSN. It can fast the handover process and reduce the end-to-end delay for the roaming MS and the traffic of the network.
2007, 29(8): 1966-1969.
doi: 10.3724/SP.J.1146.2005.01694
Abstract:
This paper presents a new efficient scheme to implement multicast communication in wormhole switching torus networks. Relied on the concept of partition, divided the network into several blocks, this scheme can achieve high degree of parallelism. Combined with adaptive routing algorithm for unicast, the multicast algorithm can achieve low communication delay, low standard deviation and high throughput. Performance results of a simulation study on torus with 512 nodes are also given.
This paper presents a new efficient scheme to implement multicast communication in wormhole switching torus networks. Relied on the concept of partition, divided the network into several blocks, this scheme can achieve high degree of parallelism. Combined with adaptive routing algorithm for unicast, the multicast algorithm can achieve low communication delay, low standard deviation and high throughput. Performance results of a simulation study on torus with 512 nodes are also given.
2007, 29(8): 1970-1973.
doi: 10.3724/SP.J.1146.2006.00069
Abstract:
One M/G/1/n queuing network model based on non-preemptive multi-priority messages is proposed for the performance analysis of softswitch entity, which contained multiple processes sharing the same CPU resources. In this model, processing time of messages is drawn from uniform distribution but not exponential distribution and messages exceeding the queue length threshold are discarded orderly according to their priorities. A formula for the mean time of message processing is derived. Academic analysis and simulation results validate that M/G/1/n model with multi-priority messages has larger throughput and higher effective CPU payload than M/G/1/n model with non-priority messages, but has a little longer message processing procedure. Simulation results also indicate that message buffer has a considerable influence on the performance of queuing system.
One M/G/1/n queuing network model based on non-preemptive multi-priority messages is proposed for the performance analysis of softswitch entity, which contained multiple processes sharing the same CPU resources. In this model, processing time of messages is drawn from uniform distribution but not exponential distribution and messages exceeding the queue length threshold are discarded orderly according to their priorities. A formula for the mean time of message processing is derived. Academic analysis and simulation results validate that M/G/1/n model with multi-priority messages has larger throughput and higher effective CPU payload than M/G/1/n model with non-priority messages, but has a little longer message processing procedure. Simulation results also indicate that message buffer has a considerable influence on the performance of queuing system.
2007, 29(8): 1974-1978.
doi: 10.3724/SP.J.1146.2005.01513
Abstract:
To improve the throughout of the networks and develop the integrated services LAN, a new medium access mode of LANdouble token and double loop protocol is put forward firstly, and then the mathematical modeling research on it is carried through. After the service time being assumed short and the virtual waiter being put forward, the system of double token and double loop LAN which has two physical waiter is equivalent to the followed queue model of the interim service with one virtual waiter. The simulation experiment shows that this double loop LAN can not only improve the dependability of the loop LAN, but also enhance the throughput of the networks in a large range, so the academic foundation for the application of this double loop LAN is provided under the condition of the integrated services.
To improve the throughout of the networks and develop the integrated services LAN, a new medium access mode of LANdouble token and double loop protocol is put forward firstly, and then the mathematical modeling research on it is carried through. After the service time being assumed short and the virtual waiter being put forward, the system of double token and double loop LAN which has two physical waiter is equivalent to the followed queue model of the interim service with one virtual waiter. The simulation experiment shows that this double loop LAN can not only improve the dependability of the loop LAN, but also enhance the throughput of the networks in a large range, so the academic foundation for the application of this double loop LAN is provided under the condition of the integrated services.
2007, 29(8): 1979-1983.
doi: 10.3724/SP.J.1146.2005.01515
Abstract:
To satisfy the requirement of large-scale streaming application with dispersive users, a novel system architecture of Multi-controller based Cluster Streaming Cache Proxy (MCSCP) is proposed. Two subsystems are introduced in this architecture: a control subsystem consists of multiple candidate cooperative controllers, and a storage subsystem is composed of content storage group. Key techniques in the control subsystem are discussed deeply: based on the graph theory, an algorithm for the selection of candidate controllers is presented; a protocol of Priority based Master controller Election and Handover (PMEH) is designed. The mathematical models are achieved to analyze the improvement in system reliability by using cooperative controllers architecture, to discuss the performance of controller election algorithm and to evaluate the relationship between the system cost and the variable of message interval. Simulation experiment is also carried out to obtain the optimal range for the value of this variable.
To satisfy the requirement of large-scale streaming application with dispersive users, a novel system architecture of Multi-controller based Cluster Streaming Cache Proxy (MCSCP) is proposed. Two subsystems are introduced in this architecture: a control subsystem consists of multiple candidate cooperative controllers, and a storage subsystem is composed of content storage group. Key techniques in the control subsystem are discussed deeply: based on the graph theory, an algorithm for the selection of candidate controllers is presented; a protocol of Priority based Master controller Election and Handover (PMEH) is designed. The mathematical models are achieved to analyze the improvement in system reliability by using cooperative controllers architecture, to discuss the performance of controller election algorithm and to evaluate the relationship between the system cost and the variable of message interval. Simulation experiment is also carried out to obtain the optimal range for the value of this variable.
2007, 29(8): 1984-1986.
doi: 10.3724/SP.J.1146.2006.00102
Abstract:
Hidden authentication oblivious transfer based on k-out-of-n oblivious transfer and hidden credentials is proposed which solved the problem that standard certificated-based access control to oblivious transfer may exposure some sensitive information of the receiver. The scheme proposed has the property that only the receiver who has the required attribute credentials can open the message it chooses and the receiver need not provide to the sender any credentials. The sender can not decide whether the receiver can open the messages or not and the sender can not know which messages that the receiver acquires also. The security in the random oracle model is proved under the BDH assumption and the CT-CDH assumption.
Hidden authentication oblivious transfer based on k-out-of-n oblivious transfer and hidden credentials is proposed which solved the problem that standard certificated-based access control to oblivious transfer may exposure some sensitive information of the receiver. The scheme proposed has the property that only the receiver who has the required attribute credentials can open the message it chooses and the receiver need not provide to the sender any credentials. The sender can not decide whether the receiver can open the messages or not and the sender can not know which messages that the receiver acquires also. The security in the random oracle model is proved under the BDH assumption and the CT-CDH assumption.
2007, 29(8): 1987-1991.
doi: 10.3724/SP.J.1146.2006.00041
Abstract:
A Mobile Robots Path Planning Algorithm based on Immune Evolutionary Negative Selection (MRPPA-IENS) mechanism is proposed in this paper. This algorithm adopts negative selection operators to avoid the bad individuals generation during evolution, which can generate good individuals earlier and accelerate the algorithms convergence. Furthermore, MRPPA-IENS adopts the gene rearrangement operator to maintain the populations diversity. The simulation experimental results demonstrate that the MRPPA-IENS algorithm proposed in this paper is an efficient mobile robots path planning algorithm and the performance of the algorithm is better than that of the traditional evolutionary algorithm when obstacles are perfectly known in static environment or partially known in dynamic environment.
A Mobile Robots Path Planning Algorithm based on Immune Evolutionary Negative Selection (MRPPA-IENS) mechanism is proposed in this paper. This algorithm adopts negative selection operators to avoid the bad individuals generation during evolution, which can generate good individuals earlier and accelerate the algorithms convergence. Furthermore, MRPPA-IENS adopts the gene rearrangement operator to maintain the populations diversity. The simulation experimental results demonstrate that the MRPPA-IENS algorithm proposed in this paper is an efficient mobile robots path planning algorithm and the performance of the algorithm is better than that of the traditional evolutionary algorithm when obstacles are perfectly known in static environment or partially known in dynamic environment.
2007, 29(8): 1992-1996.
doi: 10.3724/SP.J.1146.2006.00042
Abstract:
A novel approach to arbitrary array pattern synthesis based on biorthogonal modes is presented in this paper. The algorithm involving arrays with arbitrary geometry and incorporating mutual coupling effect, can accurately determine element excitations required to yield desired patterns. The mutual orthogonality of modes is used to ensure the agreement between the desired and computed patterns. When the weighted field is applied, the double integral can be simplified by performing one variable integral, so synthesis procedure is less time-consuming. The effectiveness of the approach is demonstrated with several numerical examples.
A novel approach to arbitrary array pattern synthesis based on biorthogonal modes is presented in this paper. The algorithm involving arrays with arbitrary geometry and incorporating mutual coupling effect, can accurately determine element excitations required to yield desired patterns. The mutual orthogonality of modes is used to ensure the agreement between the desired and computed patterns. When the weighted field is applied, the double integral can be simplified by performing one variable integral, so synthesis procedure is less time-consuming. The effectiveness of the approach is demonstrated with several numerical examples.
2007, 29(8): 1997-2000.
doi: 10.3724/SP.J.1146.2005.01646
Abstract:
A computation approach of scattering by buried objects is presented by using Finite-Difference Time-Domain (FDTD) method, the Uniaxial Perfectly Matched Layer (UPML), and reciprocity principle. The numerical performance of this approach is in detail investigated by numerical experiments. The Radar Cross Section (RCS) of various buried objects with different electrical size, shape, dielectric constant, are computed and analyzed, from which useful conclusions are obtained.
A computation approach of scattering by buried objects is presented by using Finite-Difference Time-Domain (FDTD) method, the Uniaxial Perfectly Matched Layer (UPML), and reciprocity principle. The numerical performance of this approach is in detail investigated by numerical experiments. The Radar Cross Section (RCS) of various buried objects with different electrical size, shape, dielectric constant, are computed and analyzed, from which useful conclusions are obtained.
2007, 29(8): 2001-2005.
doi: 10.3724/SP.J.1146.2005.01521
Abstract:
Charge pump plays an important role in low supply voltage integrated circuits. Three important issues of on-chip charge pump circuits are voltage gain, output voltage ripple and area efficiency. A new charge pump is proposed in this paper which introduces a subsidiary charge pump and two voltage level shifters. The new structure can generate different magnitude clocks to drive the gates of switch transistors, which will improve voltage gain of charge pump greatly by means of effective control of conduction of them. At the other hand, we can avoid the threshold voltage loss by taking PMOS transistors as switch transistors. Simulation results show: The new charge pumps have higher voltage gain, shorter start up time and small voltage ripple compared with those proposed in earlier papers, especially in low supply voltage environment.
Charge pump plays an important role in low supply voltage integrated circuits. Three important issues of on-chip charge pump circuits are voltage gain, output voltage ripple and area efficiency. A new charge pump is proposed in this paper which introduces a subsidiary charge pump and two voltage level shifters. The new structure can generate different magnitude clocks to drive the gates of switch transistors, which will improve voltage gain of charge pump greatly by means of effective control of conduction of them. At the other hand, we can avoid the threshold voltage loss by taking PMOS transistors as switch transistors. Simulation results show: The new charge pumps have higher voltage gain, shorter start up time and small voltage ripple compared with those proposed in earlier papers, especially in low supply voltage environment.
2007, 29(8): 2006-2008.
doi: 10.3724/SP.J.1146.2006.00122
Abstract:
Based on multi-stage comparison, a new theory incorporating Minimum Comparator Number Algorithm (MCNA) and Power-Conversion Rate Merit Model (PCRMM) is proposed, which releases the power dissipation from limitation of comparators, sub-DACs and residual amplifiers in high-speed high-resolution ADCs. Under 10-bit ADC resolution specific, theoretical analysis shows that this theory reduces the power dissipation of Flash ADC to minimum by applying 3-stage Pipelined ADC, while keeping ADC high-speed, and it also proves that two-step ADC is better than other type of multi-step ADC. This new theory can be used in designing and developing high-speed low-power ADCs.
Based on multi-stage comparison, a new theory incorporating Minimum Comparator Number Algorithm (MCNA) and Power-Conversion Rate Merit Model (PCRMM) is proposed, which releases the power dissipation from limitation of comparators, sub-DACs and residual amplifiers in high-speed high-resolution ADCs. Under 10-bit ADC resolution specific, theoretical analysis shows that this theory reduces the power dissipation of Flash ADC to minimum by applying 3-stage Pipelined ADC, while keeping ADC high-speed, and it also proves that two-step ADC is better than other type of multi-step ADC. This new theory can be used in designing and developing high-speed low-power ADCs.
2007, 29(8): 2009-2013.
doi: 10.3724/SP.J.1146.2005.01482
Abstract:
In this paper, the design procedure of a harmonic multiplying Gyro-TWT with three stage interaction circuits is presented. The starting oscillation condition of competing modes is studied with linear theory to select the working parameters for keeping the stability of working mode. The saturated output performance of the working mode is discussed by using a consistent non-linear theory. Based on large signal numerical analysis, a saturated peak power of 540kW with an efficiency of 21.6%, a gain of 58dB, and a 3dB bandwidth of 4.5% is predicted for the gyro-TWT driven by 100kV, 25A electron beam with a velocity ratio of 1.0 and velocity spread 5% at 34.6GHz.
In this paper, the design procedure of a harmonic multiplying Gyro-TWT with three stage interaction circuits is presented. The starting oscillation condition of competing modes is studied with linear theory to select the working parameters for keeping the stability of working mode. The saturated output performance of the working mode is discussed by using a consistent non-linear theory. Based on large signal numerical analysis, a saturated peak power of 540kW with an efficiency of 21.6%, a gain of 58dB, and a 3dB bandwidth of 4.5% is predicted for the gyro-TWT driven by 100kV, 25A electron beam with a velocity ratio of 1.0 and velocity spread 5% at 34.6GHz.
2007, 29(8): 2014-2018.
doi: 10.3724/SP.J.1146.2005.01590
Abstract:
In this paper, the beam-wave interaction of a Ka-band complex cavity gyrotron with gradual transition is studied according to a particle in cell simulation program. The effect of the cavity dimension, electron beam parameter and operating magnetic field on the electron efficiency is analyzed. The stability of the working mode is discussed. The results show that an electron efficiency of more than 60% and good stability is predicted for the complex cavity gyrotron with appropriate working parameters when driven by a 70kV, 17A electron beam with a velocity ratio of 1.5.
In this paper, the beam-wave interaction of a Ka-band complex cavity gyrotron with gradual transition is studied according to a particle in cell simulation program. The effect of the cavity dimension, electron beam parameter and operating magnetic field on the electron efficiency is analyzed. The stability of the working mode is discussed. The results show that an electron efficiency of more than 60% and good stability is predicted for the complex cavity gyrotron with appropriate working parameters when driven by a 70kV, 17A electron beam with a velocity ratio of 1.5.
2007, 29(8): 2019-2022.
doi: 10.3724/SP.J.1146.2005.01462
Abstract:
CVD diamond material, applying in broad band millimeter wave helical Traveling Wave Tube (TWT), is discussed. Two kinds of novel helical slow wave circuit, supported by CVD diamond, are presented. Dispersion, interaction impedance and attenuation of these circuits are simulated by MAFIA, compared with circuit supported by BeO rods. Nonlinear beam and wave interaction of the TWTs, replaced slow wave circuit supported by BeO rods with new circuit, are analyzed using BWI module in TWTCAD Integral Framework, which is a suite of helix TWT design code. The results show that Stud-Diamond helical slow wave circuit has broader band and excellent cooling capability is implied, it should has important apply to broad band millimeter wave power helical TWT.
CVD diamond material, applying in broad band millimeter wave helical Traveling Wave Tube (TWT), is discussed. Two kinds of novel helical slow wave circuit, supported by CVD diamond, are presented. Dispersion, interaction impedance and attenuation of these circuits are simulated by MAFIA, compared with circuit supported by BeO rods. Nonlinear beam and wave interaction of the TWTs, replaced slow wave circuit supported by BeO rods with new circuit, are analyzed using BWI module in TWTCAD Integral Framework, which is a suite of helix TWT design code. The results show that Stud-Diamond helical slow wave circuit has broader band and excellent cooling capability is implied, it should has important apply to broad band millimeter wave power helical TWT.
2007, 29(8): 2023-2025.
doi: 10.3724/SP.J.1146.2005.01476
Abstract:
Clover-leaf coupled cavity is a kind of slow-wave structure of high interaction impedance.The mathematic analyse and the engineering design are very difficult for its complex structure.In this paper, three- dimensional simulation codes Isfel3d，Mafia，HFSS are used to determine the dispersion and interaction impedance.Based on analyse of simulate results,the coupled cavity slow-wave structure is optimized primarily.The simulation results is consistent with the measurement results and is significant to design of the slow-wave structure.
Clover-leaf coupled cavity is a kind of slow-wave structure of high interaction impedance.The mathematic analyse and the engineering design are very difficult for its complex structure.In this paper, three- dimensional simulation codes Isfel3d，Mafia，HFSS are used to determine the dispersion and interaction impedance.Based on analyse of simulate results,the coupled cavity slow-wave structure is optimized primarily.The simulation results is consistent with the measurement results and is significant to design of the slow-wave structure.
2007, 29(8): 2026-2028.
doi: 10.3724/SP.J.1146.2006.00846
Abstract:
A method to construct secret authentication codes by using Cartesian codes is presented in the paper. On the condition of not changing the quantity of encoding rules, the proposed method uses Latin square to reconstruct the optimum Cartesian authentication codes into perfect secret authentication codes.
A method to construct secret authentication codes by using Cartesian codes is presented in the paper. On the condition of not changing the quantity of encoding rules, the proposed method uses Latin square to reconstruct the optimum Cartesian authentication codes into perfect secret authentication codes.
2007, 29(8): 2029-2032.
doi: 10.3724/SP.J.1146.2006.00112
Abstract:
In this paper, the theoretical model of multistage depressed collector for traveling wave tubes, including the technology of automatic mesh generation, the effects of secondary electrons, space charges, magnetic fields and the method of computation of collectors efficiency, is presented in detail. Based on this theory, a two-dimensional software is developed and is used in the design of symmetrical multistage depressed collectors. Finally, the recent development of the theory is summarized and some referable advices are suggested.
In this paper, the theoretical model of multistage depressed collector for traveling wave tubes, including the technology of automatic mesh generation, the effects of secondary electrons, space charges, magnetic fields and the method of computation of collectors efficiency, is presented in detail. Based on this theory, a two-dimensional software is developed and is used in the design of symmetrical multistage depressed collectors. Finally, the recent development of the theory is summarized and some referable advices are suggested.
