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2008 Vol. 30, No. 2
Display Method:
2008, 30(2): 255-258.
doi: 10.3724/SP.J.1146.2007.00096
Abstract:
The problem of decision fusion for target recognition is usually solved by the uncertainty information processing methods. This paper presents a novel algorithm of decision fusion for target recognition based on the grey fixed weight clustering analysis. The problem of recognizing M classes target is transformed into M problems of recognizing two classes target, and then each problem of recognizing two classes target is solved by the grey fixed weight clustering. The whitenization weight functions of each two classes are assessed by training samples. The experiment conducted on three classifiers and five classes radar target data demonstrates this method can effectively improve the recognition performance.
The problem of decision fusion for target recognition is usually solved by the uncertainty information processing methods. This paper presents a novel algorithm of decision fusion for target recognition based on the grey fixed weight clustering analysis. The problem of recognizing M classes target is transformed into M problems of recognizing two classes target, and then each problem of recognizing two classes target is solved by the grey fixed weight clustering. The whitenization weight functions of each two classes are assessed by training samples. The experiment conducted on three classifiers and five classes radar target data demonstrates this method can effectively improve the recognition performance.
2008, 30(2): 259-262.
doi: 10.3724/SP.J.1146.2006.01090
Abstract:
Though traditional meanshift method has the virtue of simplicity and availability, it does not work well when the target gets an occlusion. In the meanwhile, particle filter can solve this problem easily. Unfortunately, its performance relies heavily on the numbers of the used particles. It makes the tracking technique by particle filtering have difficulty in satisfying the requirement of real time computing. To settle the problem, this article brings about a hybrid algorithm by combining the mean shift and the particle filter tracking technique on the basis of the color histogram distribution. By adopting the strategy that the number of particles is adaptively determined, it amalgamates the virtues of the two techniques. It reduces the computational cost and ensures the performance simultaneously. The experimental results show that the proposed method is effective and robust.
Though traditional meanshift method has the virtue of simplicity and availability, it does not work well when the target gets an occlusion. In the meanwhile, particle filter can solve this problem easily. Unfortunately, its performance relies heavily on the numbers of the used particles. It makes the tracking technique by particle filtering have difficulty in satisfying the requirement of real time computing. To settle the problem, this article brings about a hybrid algorithm by combining the mean shift and the particle filter tracking technique on the basis of the color histogram distribution. By adopting the strategy that the number of particles is adaptively determined, it amalgamates the virtues of the two techniques. It reduces the computational cost and ensures the performance simultaneously. The experimental results show that the proposed method is effective and robust.
2008, 30(2): 263-266.
doi: 10.3724/SP.J.1146.2007.00405
Abstract:
A novel image recognition algorithm, Synergetic Neural Networks (SNN) based on immune clonal lgorithm, is proposed in this paper. The presented method introduces the global optimal searching ability of immune clonal select algorithm to construct data clustering algorithm, which used to solve the prototype vector in SNN. The simulation result of the Brodatz images and Synthetic Aperture Radar (SAR) images show the proposed algorithm can improve the performance of SNN as compared with the standard SNN and it can reduce greatly the training and test time leave the classification accuracy almost unchanged as compared with the traditional support vector machine.
A novel image recognition algorithm, Synergetic Neural Networks (SNN) based on immune clonal lgorithm, is proposed in this paper. The presented method introduces the global optimal searching ability of immune clonal select algorithm to construct data clustering algorithm, which used to solve the prototype vector in SNN. The simulation result of the Brodatz images and Synthetic Aperture Radar (SAR) images show the proposed algorithm can improve the performance of SNN as compared with the standard SNN and it can reduce greatly the training and test time leave the classification accuracy almost unchanged as compared with the traditional support vector machine.
2008, 30(2): 267-271.
doi: 10.3724/SP.J.1146.2006.01140
Abstract:
An anomaly target detection method based on the high correlation band subsets and fuzzy integral fusion is presented to deal with detecting unknown target in unknown background for hyperspectral imagery. Original hyperspectral data is divided into several continuous band subsets according to the high correlation within the subset. Applying nonparametric kernel density estimation to the RX detector output of each subset to obtain its probability density function (pdf), and a nonparametric fuzzy membership function is constructed; based on the eigenvalues in spectral dimension, a target signal-noise-ratio is defined to measure the degree of importance of detection result from each subset; finally, decision fusion is implemented through Sugeno fuzzy integral method. Experiments on visible/near-infrared OMIS-I hyperspectral imagery justify the effectiveness of the algorithm.
An anomaly target detection method based on the high correlation band subsets and fuzzy integral fusion is presented to deal with detecting unknown target in unknown background for hyperspectral imagery. Original hyperspectral data is divided into several continuous band subsets according to the high correlation within the subset. Applying nonparametric kernel density estimation to the RX detector output of each subset to obtain its probability density function (pdf), and a nonparametric fuzzy membership function is constructed; based on the eigenvalues in spectral dimension, a target signal-noise-ratio is defined to measure the degree of importance of detection result from each subset; finally, decision fusion is implemented through Sugeno fuzzy integral method. Experiments on visible/near-infrared OMIS-I hyperspectral imagery justify the effectiveness of the algorithm.
2008, 30(2): 272-276.
doi: 10.3724/SP.J.1146.2006.01129
Abstract:
Global analysis method and individual analysis method are proposed in this paper. By analyzing their traits, it is concluded that individual analysis method is more suitable for machine-printed Chinese font recognition. A feature point based individual analysis method is proposed to resolve Chinese font recognition problem. Compared with previous methods, there are mainly three advantages: The recognition reliability is controllable; the processing speed is fast; it is suitable for multi-lingual document image processing. Experimental results show that the proposed method is more effective than previous methods.
Global analysis method and individual analysis method are proposed in this paper. By analyzing their traits, it is concluded that individual analysis method is more suitable for machine-printed Chinese font recognition. A feature point based individual analysis method is proposed to resolve Chinese font recognition problem. Compared with previous methods, there are mainly three advantages: The recognition reliability is controllable; the processing speed is fast; it is suitable for multi-lingual document image processing. Experimental results show that the proposed method is more effective than previous methods.
2008, 30(2): 277-281.
doi: 10.3724/SP.J.1146.2006.00999
Abstract:
The assumption of conditional independence in the relationship between adjacent blocks has been proposed by others to reduce the complexity of 2D HMM. In this paper, a more general 2D HMM relaxing this assumption is proposed. More general recursive forms of the forward and the backward algorithms are derived. And the model provides more flexibility by adjusting the weight between horizontal and vertical information. The application to image segmentation verifies the effectiveness of the model.
The assumption of conditional independence in the relationship between adjacent blocks has been proposed by others to reduce the complexity of 2D HMM. In this paper, a more general 2D HMM relaxing this assumption is proposed. More general recursive forms of the forward and the backward algorithms are derived. And the model provides more flexibility by adjusting the weight between horizontal and vertical information. The application to image segmentation verifies the effectiveness of the model.
2008, 30(2): 282-285.
doi: 10.3724/SP.J.1146.2006.01030
Abstract:
This paper describes a simple adaptive pattern control method based on Linearly Constrained Minimum Variance (LCMV). The quiescent pattern weights are imposed in constrain which make the overall beamformer sidelobe response equal the desired quiescent response and form nulls in the direction of interference at the same time. The sidelobe exhibits large ripples in condition of small training sample size and the diagonal loading method is combined with this method, which improve the convergence speed in sidelobe. The effectiveness of this new method is illustrated by a few designed examples.
This paper describes a simple adaptive pattern control method based on Linearly Constrained Minimum Variance (LCMV). The quiescent pattern weights are imposed in constrain which make the overall beamformer sidelobe response equal the desired quiescent response and form nulls in the direction of interference at the same time. The sidelobe exhibits large ripples in condition of small training sample size and the diagonal loading method is combined with this method, which improve the convergence speed in sidelobe. The effectiveness of this new method is illustrated by a few designed examples.
2008, 30(2): 286-289.
doi: 10.3724/SP.J.1146.2006.01835
Abstract:
The Polynomial Wigner-Ville Distribution (PWVD) is a time-frequency signal analysis tool for representing Polynomial Phase Signal (PPS). An algorithm for implementation of the PWVD based on the convolution in frequency domain according to the structure of the PWVD is presented in this paper. By decomposing the PWVD into a series of convolutions of WVD or LWVD, the cross-terms can be reduced just because the WVD or LWVD can be calculated by the STFT, which is a linear transform. At the same time, the PWVD have a high time frequency convergence. The discrete implementation method and the corresponding computation complexity are analyzed and the effectiveness of the method is illustrated with numerical examples.
The Polynomial Wigner-Ville Distribution (PWVD) is a time-frequency signal analysis tool for representing Polynomial Phase Signal (PPS). An algorithm for implementation of the PWVD based on the convolution in frequency domain according to the structure of the PWVD is presented in this paper. By decomposing the PWVD into a series of convolutions of WVD or LWVD, the cross-terms can be reduced just because the WVD or LWVD can be calculated by the STFT, which is a linear transform. At the same time, the PWVD have a high time frequency convergence. The discrete implementation method and the corresponding computation complexity are analyzed and the effectiveness of the method is illustrated with numerical examples.
2008, 30(2): 290-292.
doi: 10.3724/SP.J.1146.2006.01178
Abstract:
Traditional partition function-based multifractal formalism provides only global estimates of singularity exponents, no local information is offered. However, it is more important to recover the local singularity. A novel algorithm for determining the local singularity exponents is proposed, which provides the local scaling information of interest, whilst a singularity-spectrum-like histogram is constructed to describe the global statistical distribution of the local singularity strengths. The validity is verified by numerical experiment.
Traditional partition function-based multifractal formalism provides only global estimates of singularity exponents, no local information is offered. However, it is more important to recover the local singularity. A novel algorithm for determining the local singularity exponents is proposed, which provides the local scaling information of interest, whilst a singularity-spectrum-like histogram is constructed to describe the global statistical distribution of the local singularity strengths. The validity is verified by numerical experiment.
2008, 30(2): 293-297.
doi: 10.3724/SP.J.1146.2006.00804
Abstract:
To estimate sinusoidal signals real frequency ,amplitude and original phase precisely under noisy circumstances, a novel phase difference correcting spectrum method which combines both all-phase FFT and conventional FFT is proposed. This technique is of low computation complexity and convenient. The frequency and amplitude estimation can be acquired by implementing simple operation on these two spectral analysis results at main spectral position, moreover the all-phase FFT phase- spectrum value at main spectral position can be directly viewed as the original phase without any correcting measures. Due to all-phase FFTs excellent property of inhibiting spectral leakage, the proposed method is also feasible in the cases of dense spectrum distribution. And the phase estimation error is very tiny in the 10#61485;7 resolution level with no noise added.
To estimate sinusoidal signals real frequency ,amplitude and original phase precisely under noisy circumstances, a novel phase difference correcting spectrum method which combines both all-phase FFT and conventional FFT is proposed. This technique is of low computation complexity and convenient. The frequency and amplitude estimation can be acquired by implementing simple operation on these two spectral analysis results at main spectral position, moreover the all-phase FFT phase- spectrum value at main spectral position can be directly viewed as the original phase without any correcting measures. Due to all-phase FFTs excellent property of inhibiting spectral leakage, the proposed method is also feasible in the cases of dense spectrum distribution. And the phase estimation error is very tiny in the 10#61485;7 resolution level with no noise added.
2008, 30(2): 298-301.
doi: 10.3724/SP.J.1146.2006.01111
Abstract:
The multi-fractal spectrum of the DNA sequence of a chromosome reflects its probability distribution, and the joint multi-fractal spectrum of two DNA sequences can be used to discriminate their distributions. By employing joint multi-fractal spectrum to analyze the DNA sequences of chromosomes and randomly generated sequences according to predefined distributions, it has been shown that, different chromosomes of the same specie can be viewed as being generated from the same information source, and chromosomes of different species can not be thought so, but all are different from randomly generated sequences. The joint multi-fractal can also be used in other fields for signal modeling and analyzing.
The multi-fractal spectrum of the DNA sequence of a chromosome reflects its probability distribution, and the joint multi-fractal spectrum of two DNA sequences can be used to discriminate their distributions. By employing joint multi-fractal spectrum to analyze the DNA sequences of chromosomes and randomly generated sequences according to predefined distributions, it has been shown that, different chromosomes of the same specie can be viewed as being generated from the same information source, and chromosomes of different species can not be thought so, but all are different from randomly generated sequences. The joint multi-fractal can also be used in other fields for signal modeling and analyzing.
2008, 30(2): 302-305.
doi: 10.3724/SP.J.1146.2006.01035
Abstract:
The synchronization by using physical link for coast-ship bistatic SIAR is impractical due to the fact that the receiver is installed on a moving ship. The direct-path wave is used to calibrate the phase and complete the transmit beamforming. The factors that have effects on the accuracy of phase calibration include truncation, discretization, DFT, the motion of the receiver, multi-path and so on. The effects are analyzed and the corresponding compensation is given. The method introduced has been proved feasible by the processing of both the computer simulation and the real data.
The synchronization by using physical link for coast-ship bistatic SIAR is impractical due to the fact that the receiver is installed on a moving ship. The direct-path wave is used to calibrate the phase and complete the transmit beamforming. The factors that have effects on the accuracy of phase calibration include truncation, discretization, DFT, the motion of the receiver, multi-path and so on. The effects are analyzed and the corresponding compensation is given. The method introduced has been proved feasible by the processing of both the computer simulation and the real data.
2008, 30(2): 306-309.
doi: 10.3724/SP.J.1146.2006.00988
Abstract:
A new modified StepTransform algorithm based on CZT is provided in this paper in order to compensate for the insufficiencies of the traditional StepTransform algorithm. The order of the traditional StepTransform algorithm is changed by FFT for the fine resolution analysis on the first stage and CZT for the coarse resolution analysis on the second stage. The phenomenon of grating lobes and amplitude modulation is avoided and ideal LFM pulse compression result can be gotten in this new method. The validity and feasibility of the new algorithm is tested by the deduction of the formulation and simulation of the theory.
A new modified StepTransform algorithm based on CZT is provided in this paper in order to compensate for the insufficiencies of the traditional StepTransform algorithm. The order of the traditional StepTransform algorithm is changed by FFT for the fine resolution analysis on the first stage and CZT for the coarse resolution analysis on the second stage. The phenomenon of grating lobes and amplitude modulation is avoided and ideal LFM pulse compression result can be gotten in this new method. The validity and feasibility of the new algorithm is tested by the deduction of the formulation and simulation of the theory.
2008, 30(2): 310-313.
doi: 10.3724/SP.J.1146.2006.00986
Abstract:
Synthetic Aperture Radar (SAR) with multiple antennas can realize High-Resolution Wide-Swath (HRWS) imaging，improve Signal to Noise Ratio (SNR) and improve ambiguity suppression for Moving Target Indication (MTI). This paper proposes an algorithm can realize HRWS imaging based on conversion bi-static data into mono-static data. The algorithm can correct phase according to velocity fluctuation of platform change. Furthermore the algorithm has high efficiency, for azimuth data need only one time FFT operation. Performance analysis and computer simulation are presented to illustrate the validity of the algorithm.
Synthetic Aperture Radar (SAR) with multiple antennas can realize High-Resolution Wide-Swath (HRWS) imaging，improve Signal to Noise Ratio (SNR) and improve ambiguity suppression for Moving Target Indication (MTI). This paper proposes an algorithm can realize HRWS imaging based on conversion bi-static data into mono-static data. The algorithm can correct phase according to velocity fluctuation of platform change. Furthermore the algorithm has high efficiency, for azimuth data need only one time FFT operation. Performance analysis and computer simulation are presented to illustrate the validity of the algorithm.
2008, 30(2): 314-317.
doi: 10.3724/SP.J.1146.2006.01125
Abstract:
A new CFAR method for SAR image target detection based on ODVI-AC is proposed in this paper. The reference cells of the test cell are firstly processed by an automatic censoring algorithm in order to remove the cells of clutter and interfering targets in the reference window. The remaining cells which are homogeneous can be used to describe the statistical property of the local environments and to evaluate the parameters of the probability density function. The remaining cells can also used to yield the test statistics of two-parameter CFAR detector and calculate the adaptive CFAR threshold. The performance of ODVI-AC CFAR detector is analyzed theoretically to show its superiority. Finally, the field X band SAR image data is used as test data for this algorithm, and the comparison with other CFAR methods is favorable to the ODVI-AC CFAR in this paper.
A new CFAR method for SAR image target detection based on ODVI-AC is proposed in this paper. The reference cells of the test cell are firstly processed by an automatic censoring algorithm in order to remove the cells of clutter and interfering targets in the reference window. The remaining cells which are homogeneous can be used to describe the statistical property of the local environments and to evaluate the parameters of the probability density function. The remaining cells can also used to yield the test statistics of two-parameter CFAR detector and calculate the adaptive CFAR threshold. The performance of ODVI-AC CFAR detector is analyzed theoretically to show its superiority. Finally, the field X band SAR image data is used as test data for this algorithm, and the comparison with other CFAR methods is favorable to the ODVI-AC CFAR in this paper.
2008, 30(2): 318-321.
doi: 10.3724/SP.J.1146.2006.00960
Abstract:
Along-Track Interferometry (ATI) or Displaced Phase Centre Antenna (DPCA) technique can be applied to detect ground moving targets for airborne and space-based radars. As the first step of data processing, co-registration of the data received from different channels is necessary. In this paper, a new algorithm of data co-registration is proposed. Firstly, the received data is co-registered coarsely according to radar parameters measured primarily. Then in order to improve the co-registration accuracy further, time lag is estimated precisely via phase compensation idea based on the received data in range-Doppler domain. This algorithm does not require interpolation operation, therefore reducing the processing burden. The simulation results demonstrate that this algorithm can meet the real-time co-registration requirement.
Along-Track Interferometry (ATI) or Displaced Phase Centre Antenna (DPCA) technique can be applied to detect ground moving targets for airborne and space-based radars. As the first step of data processing, co-registration of the data received from different channels is necessary. In this paper, a new algorithm of data co-registration is proposed. Firstly, the received data is co-registered coarsely according to radar parameters measured primarily. Then in order to improve the co-registration accuracy further, time lag is estimated precisely via phase compensation idea based on the received data in range-Doppler domain. This algorithm does not require interpolation operation, therefore reducing the processing burden. The simulation results demonstrate that this algorithm can meet the real-time co-registration requirement.
2008, 30(2): 322-325.
doi: 10.3724/SP.J.1146.2006.01085
Abstract:
In this paper, an algorithm is proposed to resolve the precise imaging problem of space-borne SAR with large cell migration. This algorithm is derived in detail based on the squinted equivalent range model. A distinct difference from other algorithms is that this algorithm begins with range walk correction in the time domain, which obviously reduces the coupling between range and azimuth signal. This algorithm is compared with a common squint mode chirp scaling algorithm through the computer simulation, and the result shows that the imaging method presented in this paper is effective.
In this paper, an algorithm is proposed to resolve the precise imaging problem of space-borne SAR with large cell migration. This algorithm is derived in detail based on the squinted equivalent range model. A distinct difference from other algorithms is that this algorithm begins with range walk correction in the time domain, which obviously reduces the coupling between range and azimuth signal. This algorithm is compared with a common squint mode chirp scaling algorithm through the computer simulation, and the result shows that the imaging method presented in this paper is effective.
2008, 30(2): 326-330.
doi: 10.3724/SP.J.1146.2006.01144
Abstract:
To overcome the shortcomings of the conventional method of SAR moving target detection and imaging based on the Fractional Fourier Transform(FrFT), a modified method, which combines filtering in fractional Fourier domain, reassigned spectrogram and CLEAN, is presented for the detection, parameter estimation and imaging of moving targets. This method is able to estimate precisely the initial Doppler frequency and the Doppler centroid, and to distinguish between multiple targets lying in the same line in the time-frequency plane. The transform formulas between FrFT numeral results and Doppler parameters are also given in the paper. Simulated results prove the validity of the approach.
To overcome the shortcomings of the conventional method of SAR moving target detection and imaging based on the Fractional Fourier Transform(FrFT), a modified method, which combines filtering in fractional Fourier domain, reassigned spectrogram and CLEAN, is presented for the detection, parameter estimation and imaging of moving targets. This method is able to estimate precisely the initial Doppler frequency and the Doppler centroid, and to distinguish between multiple targets lying in the same line in the time-frequency plane. The transform formulas between FrFT numeral results and Doppler parameters are also given in the paper. Simulated results prove the validity of the approach.
2008, 30(2): 331-334.
doi: 10.3724/SP.J.1146.2006.01343
Abstract:
In according with the difference of the CS imaging processing algorithm and the RD imaging processing algorithm, the signal and the jamming imaging processing gain of the two algorithms is analyzed at the environment of noise jamming. And the formula of the signal-to-jam ratio (SJR) processing gain is deduced and analyzed. The analyzing result demonstrates that the SJR processing gains of the RD and CS imaging algorithm are uniform at the condition of the sampling rate is only larger a little than the band width of the signal. And at the condition of the over sampling rate, the SJR processing gain using RD algorithm is larger than using CS algorithm due to the two dimension matching filter of RD algorithm. However, if the over sampling signal is filtered, the SJR processing gain of CS algorithm is uniform with the RD algorithm. The computer simulation testifies the validity and the availability of the conclusion.
In according with the difference of the CS imaging processing algorithm and the RD imaging processing algorithm, the signal and the jamming imaging processing gain of the two algorithms is analyzed at the environment of noise jamming. And the formula of the signal-to-jam ratio (SJR) processing gain is deduced and analyzed. The analyzing result demonstrates that the SJR processing gains of the RD and CS imaging algorithm are uniform at the condition of the sampling rate is only larger a little than the band width of the signal. And at the condition of the over sampling rate, the SJR processing gain using RD algorithm is larger than using CS algorithm due to the two dimension matching filter of RD algorithm. However, if the over sampling signal is filtered, the SJR processing gain of CS algorithm is uniform with the RD algorithm. The computer simulation testifies the validity and the availability of the conclusion.
2008, 30(2): 335-338.
doi: 10.3724/SP.J.1146.2006.01101
Abstract:
A mathematical model of the illumination intensity, which is imposed on the point target by the radar beam step steered, is proposed for the hybrid mode SAR system. By the analysis of azimuth compressed echo signal, combining mathematical deduction, the effects of beam pointing on the image quality are proposed, which are including: the steering time of beam pointing causes infinite paired echo; the hybrid factor causes the extension of the main lobe, which results in the decrease of azimuth resolution; the hybrid factor causes the decrease of the side lobe, which increases the effect of paired echo on the image quality; the interaction of the hybrid factor and the steering time of beam pointing causes aberration of echo. These are also demonstrated by the simulation. Finally, the suggestion of establishment of the hybrid mode SAR antenna beam point steering is proposed.
A mathematical model of the illumination intensity, which is imposed on the point target by the radar beam step steered, is proposed for the hybrid mode SAR system. By the analysis of azimuth compressed echo signal, combining mathematical deduction, the effects of beam pointing on the image quality are proposed, which are including: the steering time of beam pointing causes infinite paired echo; the hybrid factor causes the extension of the main lobe, which results in the decrease of azimuth resolution; the hybrid factor causes the decrease of the side lobe, which increases the effect of paired echo on the image quality; the interaction of the hybrid factor and the steering time of beam pointing causes aberration of echo. These are also demonstrated by the simulation. Finally, the suggestion of establishment of the hybrid mode SAR antenna beam point steering is proposed.
2008, 30(2): 339-342.
doi: 10.3724/SP.J.1146.2006.01096
Abstract:
Direction of Arrival (DOA) technology based on neural network is discussed. In the paper, the DOA method based on function approach and model classification with coding is presented and it employs two kinds of neural networks: Radial Basis Function Network(RBFN) and General Regression Neural Net (GRNN). The paper introduces the network structure, simulation and the application to High Frequency Ground Wave Radar(HFGWR). The simulation and real data processing verifies that the model classification method based on GRNN offers better performance than others, its performance is good even the signal-to-noise of the signal is low until 4 dB.
Direction of Arrival (DOA) technology based on neural network is discussed. In the paper, the DOA method based on function approach and model classification with coding is presented and it employs two kinds of neural networks: Radial Basis Function Network(RBFN) and General Regression Neural Net (GRNN). The paper introduces the network structure, simulation and the application to High Frequency Ground Wave Radar(HFGWR). The simulation and real data processing verifies that the model classification method based on GRNN offers better performance than others, its performance is good even the signal-to-noise of the signal is low until 4 dB.
2008, 30(2): 343-345.
doi: 10.3724/SP.J.1146.2006.01103
Abstract:
Discrete vegetation scattering model based no distorted Born approximation solution is derived. The backscattering mechanism is illustrated. Scattering amplitude functions and model for calculating permittivity are presented. Comparisons between model predictions and field measurements on radar backscattering coefficients for corn canopy showed a reasonable good agreement at L-band for HH,VV polarizations.
Discrete vegetation scattering model based no distorted Born approximation solution is derived. The backscattering mechanism is illustrated. Scattering amplitude functions and model for calculating permittivity are presented. Comparisons between model predictions and field measurements on radar backscattering coefficients for corn canopy showed a reasonable good agreement at L-band for HH,VV polarizations.
2008, 30(2): 346-349.
doi: 10.3724/SP.J.1146.2006.01093
Abstract:
Aiming at the real application of the communication countermeasures and OFDM signal demodulation, a method is proposed to estimate the sub-carriers of OFDM signal using the high-order cyclic cumulants. Due to the fact that the high-order cyclic cumulants can suppress the stationary and non-stationary Gaussian noise, it is proved by theoretical analysis under the above noise background that the specific four-order cyclic cumulants of the OFDM signal with the 2/4 PSK modulation exist only at the location of its sub-carriers, so that the sub-carrier estimation can be implemented by detecting the cyclo-frequencies. The proposed method can also be popularized on the OFDM signal with star-QAM and high-order PSK modulation. And simulation proves the effectiveness of the proposed method.
Aiming at the real application of the communication countermeasures and OFDM signal demodulation, a method is proposed to estimate the sub-carriers of OFDM signal using the high-order cyclic cumulants. Due to the fact that the high-order cyclic cumulants can suppress the stationary and non-stationary Gaussian noise, it is proved by theoretical analysis under the above noise background that the specific four-order cyclic cumulants of the OFDM signal with the 2/4 PSK modulation exist only at the location of its sub-carriers, so that the sub-carrier estimation can be implemented by detecting the cyclo-frequencies. The proposed method can also be popularized on the OFDM signal with star-QAM and high-order PSK modulation. And simulation proves the effectiveness of the proposed method.
2008, 30(2): 350-352.
doi: 10.3724/SP.J.1146.2006.01056
Abstract:
In this paper, a new algorithm for multi-target location of sonobuoys field is presented. It is based the technique of the Blind Source Separation (BSS), and focus on the sonobuoys field that every sonobuoy has only one sensor. Computer simulation shows that the algorithm could get both the targets signal and the precision position.
In this paper, a new algorithm for multi-target location of sonobuoys field is presented. It is based the technique of the Blind Source Separation (BSS), and focus on the sonobuoys field that every sonobuoy has only one sensor. Computer simulation shows that the algorithm could get both the targets signal and the precision position.
2008, 30(2): 353-356.
doi: 10.3724/SP.J.1146.2006.01066
Abstract:
This paper proposes a robust pitch period detection method based on wavelet transformation. A Voiced Regions Detection(VRD)algorithm based on wavelet transform and Teager energy operator is proposed firstly. Then an algorithm based on spatial correlation function for estimating pitch frequency only in voiced regions is presented. Experiments show that this algorithm has a better robustness and more precision compared with the classical wavelet-based methods and auto-correlated function (ACF).
This paper proposes a robust pitch period detection method based on wavelet transformation. A Voiced Regions Detection(VRD)algorithm based on wavelet transform and Teager energy operator is proposed firstly. Then an algorithm based on spatial correlation function for estimating pitch frequency only in voiced regions is presented. Experiments show that this algorithm has a better robustness and more precision compared with the classical wavelet-based methods and auto-correlated function (ACF).
2008, 30(2): 357-361.
doi: 10.3724/SP.J.1146.2005.01655
Abstract:
This paper applies the microphone array speech enhancement method to the single microphone speech enhancement method, and proposes a new speech enhancement method based on Singular Value Decomposition(SVD). First, for the input matrix, the method adopts Jacobi singular value decomposition to get the singular value vector as the speech enhancement filter. Then the method multiplies the input matrix and the coefficient matrix of the filter to constitute the so called each channel signals. Finally, the method adopts microphone array beamforming method to gain the enhanced speech. The simulation shows that the proposed method can get rid of the addictive noise very well, and improve the speech quality.
This paper applies the microphone array speech enhancement method to the single microphone speech enhancement method, and proposes a new speech enhancement method based on Singular Value Decomposition(SVD). First, for the input matrix, the method adopts Jacobi singular value decomposition to get the singular value vector as the speech enhancement filter. Then the method multiplies the input matrix and the coefficient matrix of the filter to constitute the so called each channel signals. Finally, the method adopts microphone array beamforming method to gain the enhanced speech. The simulation shows that the proposed method can get rid of the addictive noise very well, and improve the speech quality.
2008, 30(2): 362-366.
doi: 10.3724/SP.J.1146.2006.01021
Abstract:
Whispered speech is the especial form of peoples pronunciation. There is lower Signal-to-Noise Ratio (SNR) in whispers and unobvious pitch waveform compared with the normal speech, so it is more difficult to process the whispered speech. The endpoint detection of whispers is the first pivotal step of whispered speech signal processing. This paper uses the Empirical Mode Decomposition (EMD) of Hilbert-Huang Transform (HHT) to solve the problem, and firstly proposes a novel algorithm of endpoint detection of whispered speech based on the fitting characteristic of EMD. Normalize the energy of Intrinsic Mode Function (IMF) obtained by EMD, and use the fitting parameters of the energy as the characteristic and then the endpoint of whispers can be easily divided. The results of experiments show that it is very useful in endpoint detection of whispers, and the accurate rate is 98.25% in 1200 samples (SNR=2～10dB).
Whispered speech is the especial form of peoples pronunciation. There is lower Signal-to-Noise Ratio (SNR) in whispers and unobvious pitch waveform compared with the normal speech, so it is more difficult to process the whispered speech. The endpoint detection of whispers is the first pivotal step of whispered speech signal processing. This paper uses the Empirical Mode Decomposition (EMD) of Hilbert-Huang Transform (HHT) to solve the problem, and firstly proposes a novel algorithm of endpoint detection of whispered speech based on the fitting characteristic of EMD. Normalize the energy of Intrinsic Mode Function (IMF) obtained by EMD, and use the fitting parameters of the energy as the characteristic and then the endpoint of whispers can be easily divided. The results of experiments show that it is very useful in endpoint detection of whispers, and the accurate rate is 98.25% in 1200 samples (SNR=2～10dB).
2008, 30(2): 367-370.
doi: 10.3724/SP.J.1146.2006.01081
Abstract:
A novel support vector regression method AEPSVR is proposed in this paper. First, an approximate regression function is obtained using -SVR method, and then a new adaptive error penalization function is introduced to enhance the robust performance of SVR such that a robust support vector regression is derived. Because the proposed AEPSVR here is based on -SVR, so various optimization methods for SVR can be used. Experimental results show that the proposed AEPSVR can reduce the affect of outliers, and have the very good generalization capability.
A novel support vector regression method AEPSVR is proposed in this paper. First, an approximate regression function is obtained using -SVR method, and then a new adaptive error penalization function is introduced to enhance the robust performance of SVR such that a robust support vector regression is derived. Because the proposed AEPSVR here is based on -SVR, so various optimization methods for SVR can be used. Experimental results show that the proposed AEPSVR can reduce the affect of outliers, and have the very good generalization capability.
2008, 30(2): 371-374.
doi: 10.3724/SP.J.1146.2007.00396
Abstract:
The presence of homoclinic tangencies and homoclinic intersection makes it very difficult, sometimes even impossible, to estimate the shadowing trajectory of the non-hyperbolic nonlinear system. A new algorithm for shadowing the non-hyperbolic nonlinear system is presented in this paper, which is geometrical in nature and tries to exploit the properties of the chaotic systems. Different from former methods, this method computes the stable and unstable manifolds of the noisy trajectory firstly, and then the locations of the homoclinic tangencies are determined. Thus the effects of the homoclinic tangencies on the algorithm can be decreased to a great extent, and the length of the shadowing trajectories are estimated by the locations of these homoclinic tangencies. Also different from those methods which take it as granted that the mechanism of failure of shadowing algorithms is related with the homoclinic tangencies only, experiments in this paper demonstrate a quantitative relation between the minimal distance of homoclinic intersections and the amplitude of noise. Thus the probability that the algorithm converges to the true trajectory can be boosted efficiently, and without any doubts, this strategy can be as a heuristic approach to other methods.
The presence of homoclinic tangencies and homoclinic intersection makes it very difficult, sometimes even impossible, to estimate the shadowing trajectory of the non-hyperbolic nonlinear system. A new algorithm for shadowing the non-hyperbolic nonlinear system is presented in this paper, which is geometrical in nature and tries to exploit the properties of the chaotic systems. Different from former methods, this method computes the stable and unstable manifolds of the noisy trajectory firstly, and then the locations of the homoclinic tangencies are determined. Thus the effects of the homoclinic tangencies on the algorithm can be decreased to a great extent, and the length of the shadowing trajectories are estimated by the locations of these homoclinic tangencies. Also different from those methods which take it as granted that the mechanism of failure of shadowing algorithms is related with the homoclinic tangencies only, experiments in this paper demonstrate a quantitative relation between the minimal distance of homoclinic intersections and the amplitude of noise. Thus the probability that the algorithm converges to the true trajectory can be boosted efficiently, and without any doubts, this strategy can be as a heuristic approach to other methods.
2008, 30(2): 375-378.
doi: 10.3724/SP.J.1146.2006.01020
Abstract:
Many of the super resolution DOA(Direction-Of-Arrival) estimation algorithms presume the number of signal sources. Since the sample snapshot is limited, however, the available algorithms on source number estimation may fail at lower SNR. In this paper, a novel algorithm for high resolution DOA estimation is proposed, which not only skips sources number estimation and EVD, but also behaves satisfactorily with a few snapshot, it may be viewed as a combination of merit of conventional Capon and MUSIC method. The algorithms feasibility and robustness are analyzed and verified by the simulation and actual experiment data.
Many of the super resolution DOA(Direction-Of-Arrival) estimation algorithms presume the number of signal sources. Since the sample snapshot is limited, however, the available algorithms on source number estimation may fail at lower SNR. In this paper, a novel algorithm for high resolution DOA estimation is proposed, which not only skips sources number estimation and EVD, but also behaves satisfactorily with a few snapshot, it may be viewed as a combination of merit of conventional Capon and MUSIC method. The algorithms feasibility and robustness are analyzed and verified by the simulation and actual experiment data.
2008, 30(2): 379-382.
doi: 10.3724/SP.J.1146.2006.01131
Abstract:
In this paper, a Space-Time Block-Coded MultiCarrier Direct-Sequence Code-Division Multiple-Access (STBC MC-DS-CDMA) system is proposed. By constructing the unified signal model of STBC MC-DS-CDMA system, the subspace-based blind channel estimation is achieved and its efficiency is shown by simulation results. Based on the estimation results, consequently, the Minimum Mean-Squared Error (MMSE) multiuser detection for the STBC MC-DS-CDMA is also realized which improves the system performance significantly.
In this paper, a Space-Time Block-Coded MultiCarrier Direct-Sequence Code-Division Multiple-Access (STBC MC-DS-CDMA) system is proposed. By constructing the unified signal model of STBC MC-DS-CDMA system, the subspace-based blind channel estimation is achieved and its efficiency is shown by simulation results. Based on the estimation results, consequently, the Minimum Mean-Squared Error (MMSE) multiuser detection for the STBC MC-DS-CDMA is also realized which improves the system performance significantly.
2008, 30(2): 383-387.
doi: 10.3724/SP.J.1146.2006.01114
Abstract:
An algorithm using auto-correlation matrix of received data for OFDM timing and carrier frequency offset estimation is presented in this paper. The algorithm does not need training data. Fractional frequency offset tracking and frame synchronization are implemented by minimizing the modular sum of off-diagonal elements and diagonal elements whose position is corresponding to virtual carriers number respectively. Integral frequency offset is estimated exactly based on the position movements of diagonal elements. Mathematical derivation is also provided in the paper. The simulation results show that the proposed algorithm has a large estimation range and a high resolution.
An algorithm using auto-correlation matrix of received data for OFDM timing and carrier frequency offset estimation is presented in this paper. The algorithm does not need training data. Fractional frequency offset tracking and frame synchronization are implemented by minimizing the modular sum of off-diagonal elements and diagonal elements whose position is corresponding to virtual carriers number respectively. Integral frequency offset is estimated exactly based on the position movements of diagonal elements. Mathematical derivation is also provided in the paper. The simulation results show that the proposed algorithm has a large estimation range and a high resolution.
2008, 30(2): 388-391.
doi: 10.3724/SP.J.1146.2006.01159
Abstract:
In this paper, two multiple modulus algorithms(MMA+SDD and SMMA+SDD) are proposed based on the characteristic of the QAM signals, which overcome CMAs larger residual error and recover the rotation of the phase at the same time. Computer simulations show that the proposed algorithms lead to faster convergence rates and lower steady-state Mean Square Error(MSE) after convergence compared with the concurrent CMA and SDD algorithm. The MMA+SDD has the best performance and the SMMA+SDD has the least complexity among the three algorithms.
In this paper, two multiple modulus algorithms(MMA+SDD and SMMA+SDD) are proposed based on the characteristic of the QAM signals, which overcome CMAs larger residual error and recover the rotation of the phase at the same time. Computer simulations show that the proposed algorithms lead to faster convergence rates and lower steady-state Mean Square Error(MSE) after convergence compared with the concurrent CMA and SDD algorithm. The MMA+SDD has the best performance and the SMMA+SDD has the least complexity among the three algorithms.
2008, 30(2): 392-396.
doi: 10.3724/SP.J.1146.2006.00889
Abstract:
This paper put great emphasis on spectral correlation of MPSK signals. The cyclic spectrum density function of BPSK, QPSK, 8PSK, 16PSK signals based on a new MPSK signal expression is proposed; Extensive computer simulation of four signals based on engineering calculation formula of the spectral correlation function show the accuracy of cyclic spectrum density function.
This paper put great emphasis on spectral correlation of MPSK signals. The cyclic spectrum density function of BPSK, QPSK, 8PSK, 16PSK signals based on a new MPSK signal expression is proposed; Extensive computer simulation of four signals based on engineering calculation formula of the spectral correlation function show the accuracy of cyclic spectrum density function.
2008, 30(2): 397-400.
doi: 10.3724/SP.J.1146.2006.01284
Abstract:
The impact of spatial correlation on performance of unitary space-time codes is focused on in this paper. Based on pair-wise error probability the upper bound of bit and codeword error ratio are given in this paper. The proof of equivalence between the derived result and existed result is presented when the channels are independent. Mento-Carlo simulation results show that the spatial correlation results in performance loss and the amount of this loss depends on the extent of spatial correlation.
The impact of spatial correlation on performance of unitary space-time codes is focused on in this paper. Based on pair-wise error probability the upper bound of bit and codeword error ratio are given in this paper. The proof of equivalence between the derived result and existed result is presented when the channels are independent. Mento-Carlo simulation results show that the spatial correlation results in performance loss and the amount of this loss depends on the extent of spatial correlation.
2008, 30(2): 401-403.
doi: 10.3724/SP.J.1146.2006.01123
Abstract:
For improving the performance of MIMO system with quasi-orthogonal STBC exploiting the channel knowledge, a new transmitter scheme combining the linear precoding matrix is proposed. Before sending out from the transmit antennas, the information is sent into the space-time encoder, then is processed by a precoder matrix. Exploiting the channel correlation and mean, the linear precoder is designed based on the Pair-wise Error Probability (PEP). Simulation results show that significant gain in BER of the new system can be obtained compared with the unprecoded system.
For improving the performance of MIMO system with quasi-orthogonal STBC exploiting the channel knowledge, a new transmitter scheme combining the linear precoding matrix is proposed. Before sending out from the transmit antennas, the information is sent into the space-time encoder, then is processed by a precoder matrix. Exploiting the channel correlation and mean, the linear precoder is designed based on the Pair-wise Error Probability (PEP). Simulation results show that significant gain in BER of the new system can be obtained compared with the unprecoded system.
2008, 30(2): 404-407.
doi: 10.3724/SP.J.1146.2006.00966
Abstract:
In this paper, an algorithm of LDPC codes and adaptive bit power allocation in MIMO-OFDM system is proposed. The algorithms of LDPC codes with two different code rate and adaptive OFDM/MIMO-OFDM are simulated, at the same time, the adaptive algorithms of OFDM/MIMO-OFDM without coding are simulated. The simulation results show that, with the same transmission bandwidth and the same transmission entropy, the performance of adaptive OFDM system with lower rate LDPC codes is better than that without coding. Furthermore, the performance of adaptive OFDM system with high rate LDPC codes is better than that of adaptive OFDM, but worse than that of adaptive MIMO-OFDM.
In this paper, an algorithm of LDPC codes and adaptive bit power allocation in MIMO-OFDM system is proposed. The algorithms of LDPC codes with two different code rate and adaptive OFDM/MIMO-OFDM are simulated, at the same time, the adaptive algorithms of OFDM/MIMO-OFDM without coding are simulated. The simulation results show that, with the same transmission bandwidth and the same transmission entropy, the performance of adaptive OFDM system with lower rate LDPC codes is better than that without coding. Furthermore, the performance of adaptive OFDM system with high rate LDPC codes is better than that of adaptive OFDM, but worse than that of adaptive MIMO-OFDM.
2008, 30(2): 408-411.
doi: 10.3724/SP.J.1146.2006.01084
Abstract:
Combined beamforming with Alamouti space-time block coding may not be optimal under many situations since it only provides two equal power loading beams. A new scheme which combines beamforming with space-time block coding is proposed in this paper. The number of beams the new scheme provides is determined by the channel correlation matrix eigenvalues, and is not more than the number of transmit antennas. Condition on the number of space-time block coding transmit antennas is the same as the number of beams, the new scheme combines beamforming with space-time block coding of any code rate.Gauss-Chebyshev quadrature is used to calculate the symbol error rate of the new scheme for linear modulation and a simple numerical method is derived. The new scheme could improve the performance dramatically by providing diversity gain and beamforming gain simultaneously.
Combined beamforming with Alamouti space-time block coding may not be optimal under many situations since it only provides two equal power loading beams. A new scheme which combines beamforming with space-time block coding is proposed in this paper. The number of beams the new scheme provides is determined by the channel correlation matrix eigenvalues, and is not more than the number of transmit antennas. Condition on the number of space-time block coding transmit antennas is the same as the number of beams, the new scheme combines beamforming with space-time block coding of any code rate.Gauss-Chebyshev quadrature is used to calculate the symbol error rate of the new scheme for linear modulation and a simple numerical method is derived. The new scheme could improve the performance dramatically by providing diversity gain and beamforming gain simultaneously.
2008, 30(2): 412-415.
doi: 10.3724/SP.J.1146.2006.01083
Abstract:
Random variables of non-Gaussian distribution are produced by diffusion processes. Under the assumption of ergodicity, the stationary distribution of Markov diffusion processes described by a Stochastic Differential Equation (SDE) is obtained, which is determined by drift coefficient and diffusion coefficient. Let the drift coefficient be the first order power of x, and then the diffusion coefficient can be derived as a function of diffusion coefficient and aimed probability density function. As a result, the SDE is determined, and its solution by using Milstein high order method produces the aimed random variables. The correlation of the random samples can be adjusted through changing the constant of diffusion coefficient. Taking the Nakagami distribution and K-distribution as examples, simulation results are similar to the theoretical value, which validates the effectiveness of this method.
Random variables of non-Gaussian distribution are produced by diffusion processes. Under the assumption of ergodicity, the stationary distribution of Markov diffusion processes described by a Stochastic Differential Equation (SDE) is obtained, which is determined by drift coefficient and diffusion coefficient. Let the drift coefficient be the first order power of x, and then the diffusion coefficient can be derived as a function of diffusion coefficient and aimed probability density function. As a result, the SDE is determined, and its solution by using Milstein high order method produces the aimed random variables. The correlation of the random samples can be adjusted through changing the constant of diffusion coefficient. Taking the Nakagami distribution and K-distribution as examples, simulation results are similar to the theoretical value, which validates the effectiveness of this method.
2008, 30(2): 416-420.
doi: 10.3724/SP.J.1146.2006.01117
Abstract:
A novel random multi-beam multiplexing technique is proposed in this paper, which improves the system throughput by exploiting both multiuser diversity and spatial freedom degrees of multiple transmit antennas at the base station. Different from conventional random beamforming techniques, the proposed one first randomly selects one codeword from a given codebook of precoding matrices, then schedules several spatially multiplexing users and determines other precoding matrices. A successive scheduling algorithm is proposed, which selects a main transmit user and determines the secondary precoding matrix for the other user in the first training phase, then the secondary transmit user is selected based on the secondary precoding matrix in the second training phase. This successive scheduling way is capable of fully suppress the mutual interference between multiplexing users at cost of little feedback overhead. Also, the proposed technique can be extended to heterogeneous cases where users may be configured with different number of receive antennas. Simulation results demonstrate that the proposed technique achieves good throughput over different correlated channel environments.
A novel random multi-beam multiplexing technique is proposed in this paper, which improves the system throughput by exploiting both multiuser diversity and spatial freedom degrees of multiple transmit antennas at the base station. Different from conventional random beamforming techniques, the proposed one first randomly selects one codeword from a given codebook of precoding matrices, then schedules several spatially multiplexing users and determines other precoding matrices. A successive scheduling algorithm is proposed, which selects a main transmit user and determines the secondary precoding matrix for the other user in the first training phase, then the secondary transmit user is selected based on the secondary precoding matrix in the second training phase. This successive scheduling way is capable of fully suppress the mutual interference between multiplexing users at cost of little feedback overhead. Also, the proposed technique can be extended to heterogeneous cases where users may be configured with different number of receive antennas. Simulation results demonstrate that the proposed technique achieves good throughput over different correlated channel environments.
2008, 30(2): 421-425.
doi: 10.3724/SP.J.1146.2006.01472
Abstract:
A cross-layer scheduling algorithm for downlink of multi-user OFDM system is proposed, the algorithm considers users QoS requirement, fairness, packet queue state information of MAC layer and channel state information, power constraint of physical layer. Multi-user OFDM system can make efficient use of different parameter characters of the both layers through the proposed algorithm, to achieve the goal of guarantee users QoS and maximize wireless resource utility efficiency. Simulation results show that when mobile users have different receive SNR, the proposed algorithm has steady QoS, low drop rate and low complexity.
A cross-layer scheduling algorithm for downlink of multi-user OFDM system is proposed, the algorithm considers users QoS requirement, fairness, packet queue state information of MAC layer and channel state information, power constraint of physical layer. Multi-user OFDM system can make efficient use of different parameter characters of the both layers through the proposed algorithm, to achieve the goal of guarantee users QoS and maximize wireless resource utility efficiency. Simulation results show that when mobile users have different receive SNR, the proposed algorithm has steady QoS, low drop rate and low complexity.
2008, 30(2): 426-429.
doi: 10.3724/SP.J.1146.2007.00017
Abstract:
In this paper, the impact of feedback delay on the performance of one closed multi-antennas system based transmit antenna selection is investigated. In such system, the receiver uses the maximum instantaneous SNR to select a target transmit antenna, then feedback the selected information to the receiver for transmit selection through the feedback link. The impact of feedback delay on the ergodic capacity, system outage probability and the bit error rate based on BPSK modulation are researched and the analytic results are presented. Simulations also demonstrate the effect of feedback delay on system performance.
In this paper, the impact of feedback delay on the performance of one closed multi-antennas system based transmit antenna selection is investigated. In such system, the receiver uses the maximum instantaneous SNR to select a target transmit antenna, then feedback the selected information to the receiver for transmit selection through the feedback link. The impact of feedback delay on the ergodic capacity, system outage probability and the bit error rate based on BPSK modulation are researched and the analytic results are presented. Simulations also demonstrate the effect of feedback delay on system performance.
2008, 30(2): 430-434.
doi: 10.3724/SP.J.1146.2007.00521
Abstract:
In the traditional schemes, the collided packets will be discarded and retransmitted, which results in a lower performance. In this article, Generalized Hybrid Forward Packets Collision Resolution (GHF-PCR) scheme based on virtual-MIMO techniques is studied and discussed. A kind of theoretic analytic model is established, and two kinds of cooperative nodes selection algorithms are also improved. Two PCR schemes are proposed and the average capacity, packets error rate, slot equivalent throughput and optimal transmission probability are analyzed. The proposed schemes could support random amount of collided nodes by selecting cooperative nodes to form virtual parallel channels and hence can deal with the collisions. The simulation results show that the proposed schemes can obtain better performance gain and be used in broader domain of application comparing with traditional schemes and other congener ones.
In the traditional schemes, the collided packets will be discarded and retransmitted, which results in a lower performance. In this article, Generalized Hybrid Forward Packets Collision Resolution (GHF-PCR) scheme based on virtual-MIMO techniques is studied and discussed. A kind of theoretic analytic model is established, and two kinds of cooperative nodes selection algorithms are also improved. Two PCR schemes are proposed and the average capacity, packets error rate, slot equivalent throughput and optimal transmission probability are analyzed. The proposed schemes could support random amount of collided nodes by selecting cooperative nodes to form virtual parallel channels and hence can deal with the collisions. The simulation results show that the proposed schemes can obtain better performance gain and be used in broader domain of application comparing with traditional schemes and other congener ones.
2008, 30(2): 435-438.
doi: 10.3724/SP.J.1146.2006.01054
Abstract:
A soft-detector with low complexity is proposed for Differential Unitary Space-Time Modulation (DUSTM). Based on the multiple symbol differential detection, the detector provides log-likelihood ratios of coded bits for the successive soft-decision decoding. Simulation results show that by using the proposed algorithm in a coded DUSTM system, the signal power efficiency is improved by 2~4dB compared with the counterpart of hard-decision decoding within an acceptable range of bit error rate, and the error floor caused by a single symbol differential soft-detector is eliminated in fast fading.
A soft-detector with low complexity is proposed for Differential Unitary Space-Time Modulation (DUSTM). Based on the multiple symbol differential detection, the detector provides log-likelihood ratios of coded bits for the successive soft-decision decoding. Simulation results show that by using the proposed algorithm in a coded DUSTM system, the signal power efficiency is improved by 2~4dB compared with the counterpart of hard-decision decoding within an acceptable range of bit error rate, and the error floor caused by a single symbol differential soft-detector is eliminated in fast fading.
2008, 30(2): 439-442.
doi: 10.3724/SP.J.1146.2006.01075
Abstract:
A novel acquisition performance analysis approach is proposed based on matrix analysis. Given the first step transition probability matrix, the transfer function of acquisition system can be obtained by utilizing the symbol operation function of computer programming such as MAPLE, MATLAB and so on, and the mean acquisition time can be computed by differentiating the transfer function. The transfer function of acquisition system can be computed perfectly by matrix analysis, it not only complements the items neglected in that of conventional serial acquisition scheme but also corrects the error items in that of nonconsecutive acquisition scheme.
A novel acquisition performance analysis approach is proposed based on matrix analysis. Given the first step transition probability matrix, the transfer function of acquisition system can be obtained by utilizing the symbol operation function of computer programming such as MAPLE, MATLAB and so on, and the mean acquisition time can be computed by differentiating the transfer function. The transfer function of acquisition system can be computed perfectly by matrix analysis, it not only complements the items neglected in that of conventional serial acquisition scheme but also corrects the error items in that of nonconsecutive acquisition scheme.
2008, 30(2): 443-446.
doi: 10.3724/SP.J.1146.2007.00200
Abstract:
In this paper, a novel algorithm for distributed power control in cellular CDMA system based on game theory is proposed and an effective cost function is designed for this scheme. Then the existence and uniqueness of the Nash equilibrium are proved for the proposed algorithm. The simulation results show that the proposed algorithm, which compared with several classical distributed algorithms, not only can speed up the convergence but also reduce the transmit power while the terminals are more than 20.
In this paper, a novel algorithm for distributed power control in cellular CDMA system based on game theory is proposed and an effective cost function is designed for this scheme. Then the existence and uniqueness of the Nash equilibrium are proved for the proposed algorithm. The simulation results show that the proposed algorithm, which compared with several classical distributed algorithms, not only can speed up the convergence but also reduce the transmit power while the terminals are more than 20.
2008, 30(2): 447-450.
doi: 10.3724/SP.J.1146.2006.01010
Abstract:
In this paper, an adaptive multiuser receiver for variable spreading length direct-sequence code- division multiple-access systems in multi-path channel is proposed. The signature vectors are estimated by projection onto the intersectant subspaces. Based on the estimated signature vectors, the multiuser detector is constructed. By exploiting the structure of the subspace tracking algorithm, the low-complexity adaptive signature vectors estimator and multiuser receiver are developed. Simulation results demonstrate that the proposed algorithm has the same performance，but lower computational complexity compared with the reference algorithm.
In this paper, an adaptive multiuser receiver for variable spreading length direct-sequence code- division multiple-access systems in multi-path channel is proposed. The signature vectors are estimated by projection onto the intersectant subspaces. Based on the estimated signature vectors, the multiuser detector is constructed. By exploiting the structure of the subspace tracking algorithm, the low-complexity adaptive signature vectors estimator and multiuser receiver are developed. Simulation results demonstrate that the proposed algorithm has the same performance，but lower computational complexity compared with the reference algorithm.
2008, 30(2): 451-454.
doi: 10.3724/SP.J.1146.2006.01116
Abstract:
A novel blind channel estimation scheme is presented for Space-Time Coded OFDM (STC-OFDM) systems. This scheme is composed of rude channel estimation by exploiting the finite-alphabet property of information signals and fine channel estimation by using decision-directed method, which employs the priori knowledge of the transmitted signals other than the finite-alphabet property of mapping constellation. At the cost of a little more computational complexity, it achieves better performance than the competitive one, hence it is suitable for STC-OFDM systems with a small number of subcarriers in slowly time-varying and not severely frequency selective channels. The scheme is tested with simulations and also compared with the subspace-based channel estimation.
A novel blind channel estimation scheme is presented for Space-Time Coded OFDM (STC-OFDM) systems. This scheme is composed of rude channel estimation by exploiting the finite-alphabet property of information signals and fine channel estimation by using decision-directed method, which employs the priori knowledge of the transmitted signals other than the finite-alphabet property of mapping constellation. At the cost of a little more computational complexity, it achieves better performance than the competitive one, hence it is suitable for STC-OFDM systems with a small number of subcarriers in slowly time-varying and not severely frequency selective channels. The scheme is tested with simulations and also compared with the subspace-based channel estimation.
2008, 30(2): 455-458.
doi: 10.3724/SP.J.1146.2006.01049
Abstract:
Based on the theory of queue, a blocking probability model M/M/T/T is presented for a simple and cost-effective architecture of all optical wavelength router to investigate the blocking probability of the wavelength router in WDM wavelength routed all-optical network. It is found that the blocking probability is relevant to the number of wavelength per link and the number of access fiber link ports, and with or without wavelength conversion. Especially, more attention is paid to the blocking performance of the router with limited wavelength convertible capability. And it is seen by the numerical computing that low conversion degree of the wavelength converter is more realistic to construct a wavelength router system with accurately tunable devices not used, not only switching time is to be minished, but also the complexity of carrying out in engineering is reduced.
Based on the theory of queue, a blocking probability model M/M/T/T is presented for a simple and cost-effective architecture of all optical wavelength router to investigate the blocking probability of the wavelength router in WDM wavelength routed all-optical network. It is found that the blocking probability is relevant to the number of wavelength per link and the number of access fiber link ports, and with or without wavelength conversion. Especially, more attention is paid to the blocking performance of the router with limited wavelength convertible capability. And it is seen by the numerical computing that low conversion degree of the wavelength converter is more realistic to construct a wavelength router system with accurately tunable devices not used, not only switching time is to be minished, but also the complexity of carrying out in engineering is reduced.
2008, 30(2): 459-463.
doi: 10.3724/SP.J.1146.2007.00002
Abstract:
An implementation and network platform independent model for NGN service description, FE-FR SDM (Four Elements - Full Relations Service Description Model), is proposed. This model consists of four elements: EP (EndPoint), CL (Communication Link), REL (Relations between Endpoints and Links) and RL (Relations between Links). The characteristics and the attributes of EP and CL are analyzed which are static parts of a service and REL and RL are described by directed graphs which model all possible behavior of the service. This model contains most basic properties used for requirements analysis and service architecture design, can support arbitrary number of users and one user can communicate with others in an arbitrary way. The comparison analysis with FE-FR SDM and other existent models is made, and a multimedia service is described to verify the practicability of this model.
An implementation and network platform independent model for NGN service description, FE-FR SDM (Four Elements - Full Relations Service Description Model), is proposed. This model consists of four elements: EP (EndPoint), CL (Communication Link), REL (Relations between Endpoints and Links) and RL (Relations between Links). The characteristics and the attributes of EP and CL are analyzed which are static parts of a service and REL and RL are described by directed graphs which model all possible behavior of the service. This model contains most basic properties used for requirements analysis and service architecture design, can support arbitrary number of users and one user can communicate with others in an arbitrary way. The comparison analysis with FE-FR SDM and other existent models is made, and a multimedia service is described to verify the practicability of this model.
2008, 30(2): 464-467.
doi: 10.3724/SP.J.1146.2006.00980
Abstract:
The process of service context information is the foundation of future ubiquitous convergent telecommunication services intelligence. Uncertainty is an unavoidable problem of service context information process. In this article, based on Bayesian network theory, one construction approach for service context recognition model of supporting uncertainty reasoning is presented to resolve the convergence and classification of uncertain service context information. Furthermore, the rationality and usability of this model are verified by simulations.
The process of service context information is the foundation of future ubiquitous convergent telecommunication services intelligence. Uncertainty is an unavoidable problem of service context information process. In this article, based on Bayesian network theory, one construction approach for service context recognition model of supporting uncertainty reasoning is presented to resolve the convergence and classification of uncertain service context information. Furthermore, the rationality and usability of this model are verified by simulations.
2008, 30(2): 468-471.
doi: 10.3724/SP.J.1146.2006.01034
Abstract:
In this paper, a novel packet scheduling algorithm is proposed for the video traffic in the wireless Ad hoc network. This algorithm considers the special requirements of video traffic, process every packet of video data flow individually and then distributes them to specific path according to the result of computation. This algorithm voids packet reordering on the receiver, reduces significantly the delay on the receiver and the buffer requirement. The simulation results demonstrate the correctness of the algorithm.
In this paper, a novel packet scheduling algorithm is proposed for the video traffic in the wireless Ad hoc network. This algorithm considers the special requirements of video traffic, process every packet of video data flow individually and then distributes them to specific path according to the result of computation. This algorithm voids packet reordering on the receiver, reduces significantly the delay on the receiver and the buffer requirement. The simulation results demonstrate the correctness of the algorithm.
2008, 30(2): 472-476.
doi: 10.3724/SP.J.1146.2006.01022
Abstract:
In this paper, the impact of physical carrier-sense mechanism on the fairness of the IEEE 802.11DCF MAC protocol in multi-hop Ad hoc networks is investigated, considering that physical carrier-sense range is much lager than communication range. This paper discovers that the IEEE 802.11 DCF MAC protocol may suffers from a great fairness problem because of the carrier interference. To solve this problem, a Collisions and Interferences Aware Backoff (CIAB) algorithm is then proposed. Simulation results show that this algorithm can greatly improve the fairness of the IEEE 802.11 DCF MAC protocol without significantly impairing aggregate throughput in Ad hoc networks.
In this paper, the impact of physical carrier-sense mechanism on the fairness of the IEEE 802.11DCF MAC protocol in multi-hop Ad hoc networks is investigated, considering that physical carrier-sense range is much lager than communication range. This paper discovers that the IEEE 802.11 DCF MAC protocol may suffers from a great fairness problem because of the carrier interference. To solve this problem, a Collisions and Interferences Aware Backoff (CIAB) algorithm is then proposed. Simulation results show that this algorithm can greatly improve the fairness of the IEEE 802.11 DCF MAC protocol without significantly impairing aggregate throughput in Ad hoc networks.
2008, 30(2): 477-481.
doi: 10.3724/SP.J.1146.2006.01860
Abstract:
According to wireless Ad hoc networks being able to adjust transmission rate, this paper studies the rate adaptation for network lifetime maximization. The problem is formulated as a mixed integer nonlinear programming, which can be solved using branch and bound methods. Further, a greedy distributed Maximizing Network Lifetime Rate Adaptation Algorithm (MNLRAA) is present. MNLRAA tries to selects the lower transmission rates for each link based on the traffic and the remaining energy at nodes so as to reduce energy consumption. The simulation results show that MNLRAA can improve more than 20% the network lifetime than the classic technique that all nodes transmit packet with the highest rate.
According to wireless Ad hoc networks being able to adjust transmission rate, this paper studies the rate adaptation for network lifetime maximization. The problem is formulated as a mixed integer nonlinear programming, which can be solved using branch and bound methods. Further, a greedy distributed Maximizing Network Lifetime Rate Adaptation Algorithm (MNLRAA) is present. MNLRAA tries to selects the lower transmission rates for each link based on the traffic and the remaining energy at nodes so as to reduce energy consumption. The simulation results show that MNLRAA can improve more than 20% the network lifetime than the classic technique that all nodes transmit packet with the highest rate.
2008, 30(2): 482-485.
doi: 10.3724/SP.J.1146.2006.01341
Abstract:
In this article, a brand-new information retrieval model based on Agent technology is proposed, which is to counteract some significant deficiencies existing in current information retrieval systems, such as resource consuming much, information updating delayed and so on. The main idea of this model is to apply Agent technology into the information retrieval system in order to provide users a information retrieval model of new pattern, which could update on time, save resource through distributing the information retrieval task among clients, retrieval severs and information owners. And MWRA(Multi-weight Ranking Algorithm) is also proposed in this article to improve the ranking capability of the information retrieval system, which is based on several facts, including the inclination of users, the importance of information and the matching of query. In this article, we firstly introduced the agent-based information retrieval model. Then the multi-weight ranking algorithm, which included in the model, is analyzed. Finally, the performance of the model is discussed and the prototype system is tested through a series of examinations, the result of which addresses the Agent-based information retrieval model with MWRA is better in ranking and other capabilities.
In this article, a brand-new information retrieval model based on Agent technology is proposed, which is to counteract some significant deficiencies existing in current information retrieval systems, such as resource consuming much, information updating delayed and so on. The main idea of this model is to apply Agent technology into the information retrieval system in order to provide users a information retrieval model of new pattern, which could update on time, save resource through distributing the information retrieval task among clients, retrieval severs and information owners. And MWRA(Multi-weight Ranking Algorithm) is also proposed in this article to improve the ranking capability of the information retrieval system, which is based on several facts, including the inclination of users, the importance of information and the matching of query. In this article, we firstly introduced the agent-based information retrieval model. Then the multi-weight ranking algorithm, which included in the model, is analyzed. Finally, the performance of the model is discussed and the prototype system is tested through a series of examinations, the result of which addresses the Agent-based information retrieval model with MWRA is better in ranking and other capabilities.
2008, 30(2): 486-489.
doi: 10.3724/SP.J.1146.2006.00948
Abstract:
Signature-masked authentication scheme means: when a user obtains a signature (certificate) from CA, in order to get service from a service provider and to prevent any adversary from intercepting the signature or colluding with the service provider to frame him (or her), the user is intent on proving that he (or she) really owns the signature but not transmits it to the service provider directly. Considering previous schemes can not prevent CA from impersonating legitimate users, two different CAs are introduced in this paper, and under the assumption that these two CAs do not collude, three signature-masked authentication schemes are given which guarantee that anyone including CA can not impersonate the legitimate user to get service from the provider. The first scheme is a simple scheme of unilateral authentication. Moreover, under the assumption that the user has enough computation power, mutual authentication between the user and the provider is realized in the last two schemes. Furthermore considering the first two schemes above are vulnerable to denial of service (DoS) attack, under the assumption that CA is of certain reliability, the third scheme which can also partially realize the resistance to DoS attack is proposed.
Signature-masked authentication scheme means: when a user obtains a signature (certificate) from CA, in order to get service from a service provider and to prevent any adversary from intercepting the signature or colluding with the service provider to frame him (or her), the user is intent on proving that he (or she) really owns the signature but not transmits it to the service provider directly. Considering previous schemes can not prevent CA from impersonating legitimate users, two different CAs are introduced in this paper, and under the assumption that these two CAs do not collude, three signature-masked authentication schemes are given which guarantee that anyone including CA can not impersonate the legitimate user to get service from the provider. The first scheme is a simple scheme of unilateral authentication. Moreover, under the assumption that the user has enough computation power, mutual authentication between the user and the provider is realized in the last two schemes. Furthermore considering the first two schemes above are vulnerable to denial of service (DoS) attack, under the assumption that CA is of certain reliability, the third scheme which can also partially realize the resistance to DoS attack is proposed.
2008, 30(2): 490-493.
doi: 10.3724/SP.J.1146.2006.01102
Abstract:
The ElectroMagnetic (EM) scattering characteristic from the 3D conducting object above the random ocean-like rough surfaces is evaluated by using the Method of Moment (MoM) in this paper. The vector potential dyadic Greens function and the scalar potential Greens functions are calculated of the electric dipole and magnetic dipole in the half space media. Using them in the MoM, the water sea could be regarded as the half low space medium and the sea rough surfaces could be regarded as the dielectric surfaces above the sea. The scattering characteristic of this model is calculated by establishing the integral equation of the combined conducting/dielectric objects and solving the matrix equation with the iteration method. The numerical results show the method presented in this paper is valid.
The ElectroMagnetic (EM) scattering characteristic from the 3D conducting object above the random ocean-like rough surfaces is evaluated by using the Method of Moment (MoM) in this paper. The vector potential dyadic Greens function and the scalar potential Greens functions are calculated of the electric dipole and magnetic dipole in the half space media. Using them in the MoM, the water sea could be regarded as the half low space medium and the sea rough surfaces could be regarded as the dielectric surfaces above the sea. The scattering characteristic of this model is calculated by establishing the integral equation of the combined conducting/dielectric objects and solving the matrix equation with the iteration method. The numerical results show the method presented in this paper is valid.
2008, 30(2): 494-497.
doi: 10.3724/SP.J.1146.2006.01100
Abstract:
The time-domain EFIE and MFIE approaches produce late-time oscillation for transient scattering responses from conducting objects when the incident spectrum of the field contains frequency components, which may correspond to the internal resonance of the structure. A time-domain Combined Field Integral Equation (CFIE) is presented. This formulation is based on a linear combination of the time-domain EFIE with MFIE. Numerical results for the EFIE, MFIE, and CFIE are presented and compared with those obtained from the Inverse Discrete Fourier Transform (IDFT) of the frequency-domain CFIE solution. And the time-domain CFIE solutions devoid of any resonant components.
The time-domain EFIE and MFIE approaches produce late-time oscillation for transient scattering responses from conducting objects when the incident spectrum of the field contains frequency components, which may correspond to the internal resonance of the structure. A time-domain Combined Field Integral Equation (CFIE) is presented. This formulation is based on a linear combination of the time-domain EFIE with MFIE. Numerical results for the EFIE, MFIE, and CFIE are presented and compared with those obtained from the Inverse Discrete Fourier Transform (IDFT) of the frequency-domain CFIE solution. And the time-domain CFIE solutions devoid of any resonant components.
2008, 30(2): 498-500.
doi: 10.3724/SP.J.1146.2006.01016
Abstract:
The radiation and impedance characteristic of microstrip antenna may be influenced by cutting slots on the groundplane with applications to widening the frequency band. The Method of Moment(MoM)which is used to solve the scattering of microstrip patch antenna is presented. The effect of cutting groundplane slots on the RCS is analyzed and a scheme of cutting slots is put forward combining shorted-posts load. The results indicate that the RCS is reduced a lot during a very wide frequency band, while antenna radiation performance remains. The conclusion is useful for the antenna radar cross section reduction.
The radiation and impedance characteristic of microstrip antenna may be influenced by cutting slots on the groundplane with applications to widening the frequency band. The Method of Moment(MoM)which is used to solve the scattering of microstrip patch antenna is presented. The effect of cutting groundplane slots on the RCS is analyzed and a scheme of cutting slots is put forward combining shorted-posts load. The results indicate that the RCS is reduced a lot during a very wide frequency band, while antenna radiation performance remains. The conclusion is useful for the antenna radar cross section reduction.
2008, 30(2): 501-504.
doi: 10.3724/SP.J.1146.2006.01187
Abstract:
In this paper, an X-band TE01 output window is designed, which is suitable for high power klystron. TE01 window has its uniqueness to avoid voltage breakdown due to its mode pattern and window structure. Center frequency for this window is 9GHz and bandwidth can reach as high as 7% with standing wave ratio below 1.2:1. Theory about heating effect on the designed window has been established, which shows that window cracking due to temperature gap will not occur when high power microwave with its peak value of 50MW, pulse length of 1.5s and repetition rate of 180Hz is passing through.
In this paper, an X-band TE01 output window is designed, which is suitable for high power klystron. TE01 window has its uniqueness to avoid voltage breakdown due to its mode pattern and window structure. Center frequency for this window is 9GHz and bandwidth can reach as high as 7% with standing wave ratio below 1.2:1. Theory about heating effect on the designed window has been established, which shows that window cracking due to temperature gap will not occur when high power microwave with its peak value of 50MW, pulse length of 1.5s and repetition rate of 180Hz is passing through.
2008, 30(2): 505-508.
doi: 10.3724/SP.J.1146.2006.00962
Abstract:
Symbol rate estimation of PSK signals could be effectively implemented by employing the cyclic-autocorrelation function or cyclic-autocorrelation based cyclic statistics. Stationary noise, which does not possess cyclostationarity, has an influence on cyclic-autocorrelation based PSK symbol rate estimation in practice, and this is not consistent with the theoretical analysis. The origin of such influence is studied in this paper, and the analytic expressions of means and variances of those undesired items (which are produced by stationary noise), as well as the simplified forms for Gaussian white noise are derived. Simulation experiments have testified the analytic results.
Symbol rate estimation of PSK signals could be effectively implemented by employing the cyclic-autocorrelation function or cyclic-autocorrelation based cyclic statistics. Stationary noise, which does not possess cyclostationarity, has an influence on cyclic-autocorrelation based PSK symbol rate estimation in practice, and this is not consistent with the theoretical analysis. The origin of such influence is studied in this paper, and the analytic expressions of means and variances of those undesired items (which are produced by stationary noise), as well as the simplified forms for Gaussian white noise are derived. Simulation experiments have testified the analytic results.
