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2006 Vol. 28, No. 12
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2006, 28(12): 2209-2213.
Abstract:
Aiming at giving a precise estimation of the statistic distribution of high-resolution Synthetic Aperture Radar (SAR) images, a segmentation method of SAR images using technique of non-parametric density estimate with kernel method and Markovian contexture is proposed in this paper, after studying the traditional models based on parametric technique. First, a non-parametric density estimate method based on kernel function is adopted to estimate the statistic distribution of the SAR images, and then, the SAR images is segmented with Markovian contexture by maximizing a MAP estimator, taking the former estimation as its likelihood term. And the results of the new proposed method and methods based on parametric statistical models are compared by software simulation. It shows that non-parametric density estimate technique based on kernel function can provide better results by just depending on real data, when there is no available analytical distribution function. Experiments on real SAR images also show that the non-parametric method can model the complex scenes of high-resolution SAR images such as urban areas well and get better results of segmentation.
Aiming at giving a precise estimation of the statistic distribution of high-resolution Synthetic Aperture Radar (SAR) images, a segmentation method of SAR images using technique of non-parametric density estimate with kernel method and Markovian contexture is proposed in this paper, after studying the traditional models based on parametric technique. First, a non-parametric density estimate method based on kernel function is adopted to estimate the statistic distribution of the SAR images, and then, the SAR images is segmented with Markovian contexture by maximizing a MAP estimator, taking the former estimation as its likelihood term. And the results of the new proposed method and methods based on parametric statistical models are compared by software simulation. It shows that non-parametric density estimate technique based on kernel function can provide better results by just depending on real data, when there is no available analytical distribution function. Experiments on real SAR images also show that the non-parametric method can model the complex scenes of high-resolution SAR images such as urban areas well and get better results of segmentation.
2006, 28(12): 2214-2218.
Abstract:
In usual spatial-time processing for diversity reception of UWB pulses, the channel delays are not easy to be implemented accurately. This paper firstly discusses the principle of UWB pulse array beamforming. Then a beamforming scheme is presented based on multi-rate filter bank, which is suitable for UWB pulse signals. The proposed method avoids the hardness of delays control in time domain, and can obtain the uniform frequency invariant array response in such a wideband for UWB signals. The way of realizing the multi-rate filtering is analyzed in detail, and it proves to be of easy design. Moreover, its computational cost is independent of the number of subbands. Additionally, the discontinuity of UWB pulse signals makes it possible to employ a relatively simple interpolation algorithm in time domain. The simulation results verified the feasibility and the effectiveness of this presented method.
In usual spatial-time processing for diversity reception of UWB pulses, the channel delays are not easy to be implemented accurately. This paper firstly discusses the principle of UWB pulse array beamforming. Then a beamforming scheme is presented based on multi-rate filter bank, which is suitable for UWB pulse signals. The proposed method avoids the hardness of delays control in time domain, and can obtain the uniform frequency invariant array response in such a wideband for UWB signals. The way of realizing the multi-rate filtering is analyzed in detail, and it proves to be of easy design. Moreover, its computational cost is independent of the number of subbands. Additionally, the discontinuity of UWB pulse signals makes it possible to employ a relatively simple interpolation algorithm in time domain. The simulation results verified the feasibility and the effectiveness of this presented method.
2006, 28(12): 2219-2223.
Abstract:
According to the characteristic that Forward Looking Ground Penetrating Radar (FLGPR) wave incidents aslant and propagates through two layer medium of the air and the ground, the Frequency-Wavenumber (F-W) Synthetic Aperture Imaging (SAI) method of FLGPR is proposed based on equivalent wavefield and hologram imaging. The proposed method images the recorded section above the ground by F-W SAI based on the hologram imaging method. Then, the recorded section underground is SAI with the equivalent wave field in the swath on the ground surface. The proposed method reduces the SAI in two layers to SAI in every layer respectively. The experimental results show that the proposed method is effective.
According to the characteristic that Forward Looking Ground Penetrating Radar (FLGPR) wave incidents aslant and propagates through two layer medium of the air and the ground, the Frequency-Wavenumber (F-W) Synthetic Aperture Imaging (SAI) method of FLGPR is proposed based on equivalent wavefield and hologram imaging. The proposed method images the recorded section above the ground by F-W SAI based on the hologram imaging method. Then, the recorded section underground is SAI with the equivalent wave field in the swath on the ground surface. The proposed method reduces the SAI in two layers to SAI in every layer respectively. The experimental results show that the proposed method is effective.
2006, 28(12): 2224-2227.
Abstract:
The Space-Time Adaptive Processing (STAP) algorithm of multi-channel airborne radar requires very high computing power and hardly implements. In this paper, detail analysis of computation steps of partially adaptive STAP algorithm is presents, which indicates that there is a natural, inherent parallelism in STAP algorithm. A parallel algorithm based on multi-DSP system of partially adaptive STAP is presented. The execution model, task mapping strategy and performance evaluation functions of this algorithm are also illustrated. Data remapping is used between successive computation steps of STAP. The effectiveness of the implementation is demonstrated with experimental results.
The Space-Time Adaptive Processing (STAP) algorithm of multi-channel airborne radar requires very high computing power and hardly implements. In this paper, detail analysis of computation steps of partially adaptive STAP algorithm is presents, which indicates that there is a natural, inherent parallelism in STAP algorithm. A parallel algorithm based on multi-DSP system of partially adaptive STAP is presented. The execution model, task mapping strategy and performance evaluation functions of this algorithm are also illustrated. Data remapping is used between successive computation steps of STAP. The effectiveness of the implementation is demonstrated with experimental results.
2006, 28(12): 2228-2231.
Abstract:
In order to transmit directly E-pulse for target identification, a general coefficient expression of the Fourier series for a special coded signal with a rectangle base is theoretically deduced in this paper. Then an E-pulse waveform synthesis method using Fourier series expression is proposed, as well as the principles for its parameters choice and system block diagram for E-pulse waveform synthesis. The target identification performance simulations of synthesis E-pulse and theoretical E-pulse based three finite thin wires scattering data show that the proposed method in this paper is effective. Key words Target identification, Fourier series, Waveform synthesis
In order to transmit directly E-pulse for target identification, a general coefficient expression of the Fourier series for a special coded signal with a rectangle base is theoretically deduced in this paper. Then an E-pulse waveform synthesis method using Fourier series expression is proposed, as well as the principles for its parameters choice and system block diagram for E-pulse waveform synthesis. The target identification performance simulations of synthesis E-pulse and theoretical E-pulse based three finite thin wires scattering data show that the proposed method in this paper is effective. Key words Target identification, Fourier series, Waveform synthesis
2006, 28(12): 2232-2235.
Abstract:
Chirp Scaling (CS) imaging algorithm is derived and implemented in this paper, which is adapted to bistatic and squinted radar in distributed satellites Interferometric Synthetic Aperture Radar (InSAR) system. Considering the characteristic of baseline instability in this system, an effective method is proposed to eliminate the effect of baseline instability on SAR image and interferometric measure. The simulation results validate the property of phase preserving of bistatic and squinted CS algorithm and the effectiveness of compensated method of baseline instability.
Chirp Scaling (CS) imaging algorithm is derived and implemented in this paper, which is adapted to bistatic and squinted radar in distributed satellites Interferometric Synthetic Aperture Radar (InSAR) system. Considering the characteristic of baseline instability in this system, an effective method is proposed to eliminate the effect of baseline instability on SAR image and interferometric measure. The simulation results validate the property of phase preserving of bistatic and squinted CS algorithm and the effectiveness of compensated method of baseline instability.
2006, 28(12): 2236-2239.
Abstract:
Relative height accuracy is one of key indexes for SAR interferometry. In this paper, based on actual geometrical condition for master satellite and distributed small satellite SAR system, height measure principle is established. Based on geometrical condition of relative height measure, the relations between relative height accuracy and interferometric phase error are deduced. Then, noise decorrelation, baseline decorrelation and pixel misregistration decorrelation and so on, are analyzed, and the image correlation coefficient is deduced. Finally, the effect of image decorrelations to relative height accuracy is analyzed, the results indicate, for flat surface, noise decorrelation and pixel misregistration decorrelation are the main factors, and baseline decorrelation is the minor factor.
Relative height accuracy is one of key indexes for SAR interferometry. In this paper, based on actual geometrical condition for master satellite and distributed small satellite SAR system, height measure principle is established. Based on geometrical condition of relative height measure, the relations between relative height accuracy and interferometric phase error are deduced. Then, noise decorrelation, baseline decorrelation and pixel misregistration decorrelation and so on, are analyzed, and the image correlation coefficient is deduced. Finally, the effect of image decorrelations to relative height accuracy is analyzed, the results indicate, for flat surface, noise decorrelation and pixel misregistration decorrelation are the main factors, and baseline decorrelation is the minor factor.
2006, 28(12): 2240-2243.
Abstract:
The effect of transponder time-delay on amplitude and phase of both range-compressed and azimuth-compressed signal are researched. Through simulation, the impact of transponder time-delay on imaging location, main-lobe, side-lobe of point target pulse response are analyzed and discussed under different resolution, different length of time-delay. Besides, the factors which need to be taken into consideration during time-delay setting are presented.
The effect of transponder time-delay on amplitude and phase of both range-compressed and azimuth-compressed signal are researched. Through simulation, the impact of transponder time-delay on imaging location, main-lobe, side-lobe of point target pulse response are analyzed and discussed under different resolution, different length of time-delay. Besides, the factors which need to be taken into consideration during time-delay setting are presented.
2006, 28(12): 2244-2247.
Abstract:
The characteristic of the echo of the wide swath airborne Synthetic Aperture Radar (SAR) is analyzed, then the expression of the shaped beam radiation pattern in the range plane of antenna is induced . The pattern is synthesized using the Schelkunoff unit circle method with null filling, and the exciting amplitude and phase of the 5 elements are given. The two sample microstrip arrays with different dielectric are fabricated, and the measured results are basically in accordance with the simulated and synthesized results. The valid conclusion of the synthesized and realized the shaped beam pattern can be drawn and the technology route is feasible.
The characteristic of the echo of the wide swath airborne Synthetic Aperture Radar (SAR) is analyzed, then the expression of the shaped beam radiation pattern in the range plane of antenna is induced . The pattern is synthesized using the Schelkunoff unit circle method with null filling, and the exciting amplitude and phase of the 5 elements are given. The two sample microstrip arrays with different dielectric are fabricated, and the measured results are basically in accordance with the simulated and synthesized results. The valid conclusion of the synthesized and realized the shaped beam pattern can be drawn and the technology route is feasible.
2006, 28(12): 2248-2251.
Abstract:
some research on adaptive calibration of LFM signal is implemented in this paper. Via theoretic analysis, the optimum step size and minimum misadjustment are obtained. At last, computer simulation indicate that the theoretic analysis has some value of guidance.
some research on adaptive calibration of LFM signal is implemented in this paper. Via theoretic analysis, the optimum step size and minimum misadjustment are obtained. At last, computer simulation indicate that the theoretic analysis has some value of guidance.
2006, 28(12): 2252-2255.
Abstract:
Analyzing errors of single observer-sequential BO (Bearing Only) passive location technology, a Maximum likelihood method is introduced based on 1-D coding improved genetic algorithm, in which basic least square algorithm is applied for pre-estimation. Simulations show that the method has both high precision and high practicality, for it overcomes the large search space of genetic algorithms in 2-D location.
Analyzing errors of single observer-sequential BO (Bearing Only) passive location technology, a Maximum likelihood method is introduced based on 1-D coding improved genetic algorithm, in which basic least square algorithm is applied for pre-estimation. Simulations show that the method has both high precision and high practicality, for it overcomes the large search space of genetic algorithms in 2-D location.
2006, 28(12): 2256-2258.
Abstract:
The problem that this paper discusses is how to separate the origin signals from the mixed satellite signals. The traditional method to solve the kind of problem adopts the algorithm of blind convolution which needs much account to adjust the all pathway parameters. However using the characteristic of satellite channel this paper put forwards the blind separation algorithm based on maximum entropy which can deduce the calculation too much.The results of simulations testify the validity .
The problem that this paper discusses is how to separate the origin signals from the mixed satellite signals. The traditional method to solve the kind of problem adopts the algorithm of blind convolution which needs much account to adjust the all pathway parameters. However using the characteristic of satellite channel this paper put forwards the blind separation algorithm based on maximum entropy which can deduce the calculation too much.The results of simulations testify the validity .
2006, 28(12): 2259-2262.
Abstract:
A new blind beamforming algorithm for non-Gaussian signals with arbitrary kurtosis is presented in this paper. Based on Kurtosis Maximization Algorithm (KMA), a new cost function is defined by introducing the cross-correlation of two signals. This method can estimate the weights of beamformers blindly by maximizing the new cost function, so as to separate the multitargets and find the direction. At the same time, a Genetic Algorithm (GA) with complex encoding is used to compute the weight vectors, which not only avoids the local extremum but also improves the computing speed. Simulation proves correctness of this algorithm.
A new blind beamforming algorithm for non-Gaussian signals with arbitrary kurtosis is presented in this paper. Based on Kurtosis Maximization Algorithm (KMA), a new cost function is defined by introducing the cross-correlation of two signals. This method can estimate the weights of beamformers blindly by maximizing the new cost function, so as to separate the multitargets and find the direction. At the same time, a Genetic Algorithm (GA) with complex encoding is used to compute the weight vectors, which not only avoids the local extremum but also improves the computing speed. Simulation proves correctness of this algorithm.
2006, 28(12): 2263-2268.
Abstract:
An adaptive weighted spatial smoothing algorithm is developed for adaptive arrays. By constructing a virtual issue of adaptive beamforming, the weight vector is obtained to weight the covariance matrixes of subarrays. Then, weighted spatial smoothing is processed and beamforming follows that. The theoretical analysis and simulation results show that the new algorithm can decorrelate the desired signal and the coherent interferences more efficiently, with the result that the number of sub-arrays needed decreases and the array aperture loss is reduced in spatial smoothing.
An adaptive weighted spatial smoothing algorithm is developed for adaptive arrays. By constructing a virtual issue of adaptive beamforming, the weight vector is obtained to weight the covariance matrixes of subarrays. Then, weighted spatial smoothing is processed and beamforming follows that. The theoretical analysis and simulation results show that the new algorithm can decorrelate the desired signal and the coherent interferences more efficiently, with the result that the number of sub-arrays needed decreases and the array aperture loss is reduced in spatial smoothing.
2006, 28(12): 2269-2272.
Abstract:
A modified Wiener post-filter beamforming for speech enhancement is presented. The proposed algorithm focuses on the estimation of the ideal signals power spectrum for the Wiener filter, both auto-correlation and cross-correlation are taken into consideration to obtain as more power spectrum estimations as possible, the average of which produces more accurate result. Meanwhile, the alteration of cross-correlation caused by the moving speaker is revised. The performance of the algorithm has been evaluated from Signal to Noise Ratio (SNR), Average Log Spectrum Distance (ALSD) and speech recognition rate. The SNR is improved by 5 dB. The command recognition rate based on Hidden Markov Model (HMM) in the car environment reaches 84%. The low frequency noise that still remains after the process of the primary method is reduced by the proposed method, and the speech signal distortion is also decreased.
A modified Wiener post-filter beamforming for speech enhancement is presented. The proposed algorithm focuses on the estimation of the ideal signals power spectrum for the Wiener filter, both auto-correlation and cross-correlation are taken into consideration to obtain as more power spectrum estimations as possible, the average of which produces more accurate result. Meanwhile, the alteration of cross-correlation caused by the moving speaker is revised. The performance of the algorithm has been evaluated from Signal to Noise Ratio (SNR), Average Log Spectrum Distance (ALSD) and speech recognition rate. The SNR is improved by 5 dB. The command recognition rate based on Hidden Markov Model (HMM) in the car environment reaches 84%. The low frequency noise that still remains after the process of the primary method is reduced by the proposed method, and the speech signal distortion is also decreased.
2006, 28(12): 2273-2276.
Abstract:
Ridgelet is a new signal analysis method; it is especially suitable for describing the 2-D signals which have linear or super-plane singularities. Recently, an orthonormal version of Ridgelet for discrete and finite-size images is presented, named Finite Ridgelet Transform (FRIT). In this paper, a new image de-noising method is proposed by using the threshold method based on nonparametric adaptive estimation which is presented by Birge-Massart in Ridgelet domain. Experiments show that this de-noising method represents better characteristic than traditional de-noising method in wavelet domain and the de-noising method based on Donoho strategy.
Ridgelet is a new signal analysis method; it is especially suitable for describing the 2-D signals which have linear or super-plane singularities. Recently, an orthonormal version of Ridgelet for discrete and finite-size images is presented, named Finite Ridgelet Transform (FRIT). In this paper, a new image de-noising method is proposed by using the threshold method based on nonparametric adaptive estimation which is presented by Birge-Massart in Ridgelet domain. Experiments show that this de-noising method represents better characteristic than traditional de-noising method in wavelet domain and the de-noising method based on Donoho strategy.
2006, 28(12): 2277-2282.
Abstract:
In this paper, a novel fast motion estimation algorithm called the motion vector field and direction adaptive search is proposed. According to center-bias property and spatial-temporal correlation of the motion vector field, the type of local motion activity is first determined. Based on the decision, different strategies are adaptively utilized. Stop criteria is introduced to detect the stationary macroblock, thus terminating current search immediately. Two novel search strategies with strong directional property are adopted, including the Line-Diamond Search for the macroblock with low or high motion activity, and the Hexagon-Diamond Search for the macroblock with middle motion. To achieve high searching speed for those macroblocks with large motion activity, the initial search center is predicted by the motion vector of its neighboring blocks. Experimental results show that the proposed algorithm provides faster speed and higher precision than most existing fast block-matching algorithm, while the distortion is almost the same as the FS.
In this paper, a novel fast motion estimation algorithm called the motion vector field and direction adaptive search is proposed. According to center-bias property and spatial-temporal correlation of the motion vector field, the type of local motion activity is first determined. Based on the decision, different strategies are adaptively utilized. Stop criteria is introduced to detect the stationary macroblock, thus terminating current search immediately. Two novel search strategies with strong directional property are adopted, including the Line-Diamond Search for the macroblock with low or high motion activity, and the Hexagon-Diamond Search for the macroblock with middle motion. To achieve high searching speed for those macroblocks with large motion activity, the initial search center is predicted by the motion vector of its neighboring blocks. Experimental results show that the proposed algorithm provides faster speed and higher precision than most existing fast block-matching algorithm, while the distortion is almost the same as the FS.
2006, 28(12): 2283-2286.
Abstract:
The procedure of captured iris requires considerable cooperation from the user. The method using wavefront to extend the depth-of-field of the image capture system is expatiated in the paper. The feasibility and method of realization are given in detail. Finally, the result of iris recognition contrast experimentation using this system is introduced. The method has high value for popularizing iris recognition.
The procedure of captured iris requires considerable cooperation from the user. The method using wavefront to extend the depth-of-field of the image capture system is expatiated in the paper. The feasibility and method of realization are given in detail. Finally, the result of iris recognition contrast experimentation using this system is introduced. The method has high value for popularizing iris recognition.
2006, 28(12): 2287-2291.
Abstract:
To improve the performance of the image segmentation algorithm, a relative fuzzy connected interactive segmentation algorithm is presented based on Redundant Wavelet Transform (RWT). In comparison with the original scale-based algorithm, the proposed one, with almost the same accuracy, accelerates the segmentation speed by tens times. And it is insensitive to different noise models. In addition, a study of the influence of different redundant wavelet decomposition scales is also included. The experimental results illustrate that the proposed algorithm can obtain the object regions of interest from medical as well as man-made noisy images quickly and reliably with only a little interaction.
To improve the performance of the image segmentation algorithm, a relative fuzzy connected interactive segmentation algorithm is presented based on Redundant Wavelet Transform (RWT). In comparison with the original scale-based algorithm, the proposed one, with almost the same accuracy, accelerates the segmentation speed by tens times. And it is insensitive to different noise models. In addition, a study of the influence of different redundant wavelet decomposition scales is also included. The experimental results illustrate that the proposed algorithm can obtain the object regions of interest from medical as well as man-made noisy images quickly and reliably with only a little interaction.
2006, 28(12): 2292-2295.
Abstract:
This paper describes the work on the development of an audio segmentation and classification system applied to a broadcast news task for Chinese language. Three-phase automatic audio segmentation algorithm is provided. Audio stream is cut to audio segments (or sentences) by simply segmentation, fine segmentation and smoothing. Two different fine segmentation algorithms are given. They are dynamic noise tracking segmentation algorithm and segmentation based on mono-phone decoder algorithm respectively. Classifier based on mixture Gaussian model is used to classify audio segment into four groups: noise, music, male and female. The experiments on Xin Wen Lian Bo broadcast news show the performance of automatic segmentation and classification is almost equivalent to that of manual segmentation and classification.
This paper describes the work on the development of an audio segmentation and classification system applied to a broadcast news task for Chinese language. Three-phase automatic audio segmentation algorithm is provided. Audio stream is cut to audio segments (or sentences) by simply segmentation, fine segmentation and smoothing. Two different fine segmentation algorithms are given. They are dynamic noise tracking segmentation algorithm and segmentation based on mono-phone decoder algorithm respectively. Classifier based on mixture Gaussian model is used to classify audio segment into four groups: noise, music, male and female. The experiments on Xin Wen Lian Bo broadcast news show the performance of automatic segmentation and classification is almost equivalent to that of manual segmentation and classification.
2006, 28(12): 2296-2300.
Abstract:
Face recognition tasks always encounter Small Sample Size (SSS) problem, which leads to the ill-posed problem in Fisher Linear Discriminant Analysis (FLDA). The Discriminative Common Vector (DCV) successfully overcomes this problem for FLDA. In this paper, the DCV is extended to nonlinear case, by performing the Gram-Schmidt orthogonalization twice in feature space, which involving computing two kernel matrices and performing a Cholesky decomposition of a kernel matrix. The experimental results demonstrate that the proposed KDCV achieve better performance than the DCV method.
Face recognition tasks always encounter Small Sample Size (SSS) problem, which leads to the ill-posed problem in Fisher Linear Discriminant Analysis (FLDA). The Discriminative Common Vector (DCV) successfully overcomes this problem for FLDA. In this paper, the DCV is extended to nonlinear case, by performing the Gram-Schmidt orthogonalization twice in feature space, which involving computing two kernel matrices and performing a Cholesky decomposition of a kernel matrix. The experimental results demonstrate that the proposed KDCV achieve better performance than the DCV method.
2006, 28(12): 2301-2304.
Abstract:
Markov Random Field Model (MRFM) is separated into four Markov chains which are used to represent the residuals of encoded image source. Combined with the soft output of Low Density Parity Check (LDPC) code, this simplified model is used in joint source channel decoding. Different correlation in different direction in source is regarded as a kind of natural channel code. In order to utilize the correlation, a serial decoding using forward-backward algorithm and a parallel decoding using sum-product algorithm are proposed respectively. Simulations show that compared with the traditional joint source channel decoding algorithm based on the MRFM, the proposed algorithm has lower complexity and better PSNR of the rebuilt images.
Markov Random Field Model (MRFM) is separated into four Markov chains which are used to represent the residuals of encoded image source. Combined with the soft output of Low Density Parity Check (LDPC) code, this simplified model is used in joint source channel decoding. Different correlation in different direction in source is regarded as a kind of natural channel code. In order to utilize the correlation, a serial decoding using forward-backward algorithm and a parallel decoding using sum-product algorithm are proposed respectively. Simulations show that compared with the traditional joint source channel decoding algorithm based on the MRFM, the proposed algorithm has lower complexity and better PSNR of the rebuilt images.
2006, 28(12): 2305-2309.
Abstract:
In this paper, a iterative receiver is introduced for convolutionally coded distributed MIMO with V-BLAST architecture. A maximum-likelihood (ML) iterative detector and a low-complexity Turbo detection scheme are proposed. The computational complexity is O(2MTSlogM) and O(M2TM2RS2M) respectively. Simulation results in quasi-stationary, single-path Rayleigh fading channel demonstrate that the proposed low-complexity iterative detection algorithm offers significant performance improvement about 7.5dB at than the non-iterative zero-forcing detection. At same BER (Bit Error Rate), 1 iterations Eb/N0 is 3dB above 6 iterations. Performance improvement gradually declines as the number of iteration increases.
In this paper, a iterative receiver is introduced for convolutionally coded distributed MIMO with V-BLAST architecture. A maximum-likelihood (ML) iterative detector and a low-complexity Turbo detection scheme are proposed. The computational complexity is O(2MTSlogM) and O(M2TM2RS2M) respectively. Simulation results in quasi-stationary, single-path Rayleigh fading channel demonstrate that the proposed low-complexity iterative detection algorithm offers significant performance improvement about 7.5dB at than the non-iterative zero-forcing detection. At same BER (Bit Error Rate), 1 iterations Eb/N0 is 3dB above 6 iterations. Performance improvement gradually declines as the number of iteration increases.
2006, 28(12): 2310-2314.
Abstract:
Based on the type-Ⅱand type-Ⅲ Hybrid Automatic Repeat reQuest (HARQ) system and Rata Compatible Punctured Convolutional (RCPC) code, a new HARQ system is proposed in which F sub-packets could be transmitted in one data packet, at receiver the same F sub-packets are combined with each other to form a reliable packet equal to the punctured combined sequence after F retransmission. The optimal number of repeat sub-packets is obtained to improve the performance of new HARQ system. The new HARQ system has the advantages of type-Ⅱand type-Ⅲ HARQ system, When the type-ⅡHARQ has higher throughput than the type-Ⅲ HARQ at higher Signal to Noise Ratio (SNR), the throughput and the retransmission times of the new system is close to type-Ⅱ HARQ. The new HARQ system spares the redundancy bits, whereas the type-Ⅲ HARQ retransmits too much redundancy at high SNR. On the other hand when the type-Ⅲ HARQ has higher throughput than the type-ⅡHARQ at lower SNR, the throughput and average retransmission times are close to that of the type-Ⅲ HARQ. Unlike the too much retransmission times of type-ⅡHARQ in the low SNR, the new HARQ spare the number of retransmission times.
Based on the type-Ⅱand type-Ⅲ Hybrid Automatic Repeat reQuest (HARQ) system and Rata Compatible Punctured Convolutional (RCPC) code, a new HARQ system is proposed in which F sub-packets could be transmitted in one data packet, at receiver the same F sub-packets are combined with each other to form a reliable packet equal to the punctured combined sequence after F retransmission. The optimal number of repeat sub-packets is obtained to improve the performance of new HARQ system. The new HARQ system has the advantages of type-Ⅱand type-Ⅲ HARQ system, When the type-ⅡHARQ has higher throughput than the type-Ⅲ HARQ at higher Signal to Noise Ratio (SNR), the throughput and the retransmission times of the new system is close to type-Ⅱ HARQ. The new HARQ system spares the redundancy bits, whereas the type-Ⅲ HARQ retransmits too much redundancy at high SNR. On the other hand when the type-Ⅲ HARQ has higher throughput than the type-ⅡHARQ at lower SNR, the throughput and average retransmission times are close to that of the type-Ⅲ HARQ. Unlike the too much retransmission times of type-ⅡHARQ in the low SNR, the new HARQ spare the number of retransmission times.
2006, 28(12): 2315-2317.
Abstract:
In this paper, based on (n,2,k) regular Low Density Parity-Check (LDPC) codes without short cycles, a geometry method for the construction of(n,3,k) regular LDPC codes with 8-girth is proposed,which is simple,intuitionistic and effective. Simulation results show that these codes achieve obviously better performance than randomly constructed regular LDPC codes over AWGN channals.
In this paper, based on (n,2,k) regular Low Density Parity-Check (LDPC) codes without short cycles, a geometry method for the construction of(n,3,k) regular LDPC codes with 8-girth is proposed,which is simple,intuitionistic and effective. Simulation results show that these codes achieve obviously better performance than randomly constructed regular LDPC codes over AWGN channals.
2006, 28(12): 2318-2322.
Abstract:
A time-frequency analysis method, named HHT(Hilbert-Huang Transformation), is applied to the demodulation of 2FSK systems. This method, based on the characteristics of the signal itself, is often used to analyze the instantaneous frequency distributions for non-stationary signals, and in this thesis, it is adopted to realize the demodulation of 2FSK systems. The rationality and feasibility in the process of demodulation is discussed by comparison with traditional methods. Simulation results prove the anti-noise capability and demodulation effectiveness of this new method.
A time-frequency analysis method, named HHT(Hilbert-Huang Transformation), is applied to the demodulation of 2FSK systems. This method, based on the characteristics of the signal itself, is often used to analyze the instantaneous frequency distributions for non-stationary signals, and in this thesis, it is adopted to realize the demodulation of 2FSK systems. The rationality and feasibility in the process of demodulation is discussed by comparison with traditional methods. Simulation results prove the anti-noise capability and demodulation effectiveness of this new method.
2006, 28(12): 2323-2324.
Abstract:
One of key assumptions of currently popular space-time processing technology is that receiver knows MIMO channel state information(CSI). Because MIMO channel is time-varying, how to track channel is veryimportant. In this paper, blind tracking of narrow-band MIMO channel based on sequential Monte Carlo is proposed. Simulation results show the good tracking of the proposed method.
One of key assumptions of currently popular space-time processing technology is that receiver knows MIMO channel state information(CSI). Because MIMO channel is time-varying, how to track channel is veryimportant. In this paper, blind tracking of narrow-band MIMO channel based on sequential Monte Carlo is proposed. Simulation results show the good tracking of the proposed method.
2006, 28(12): 2325-2329.
Abstract:
Frequency offset tracking is one of the key technologies that affect OFDM systems performance. Based on early-late gate phase-locked loop, a new frequency offset tracking algorithm is proposed in this paper. The study shows that the algorithm can complete frequency offset tracking in AWGN channel and multipath fading channel. Furthermore under lower SNR the performance of the proposed algorithm is better by several orders compared to the common frequency offset tracking methods. If the systems have not very special requirements on timing tracking this algorithm also can complete joint tracking of frequency and timing.
Frequency offset tracking is one of the key technologies that affect OFDM systems performance. Based on early-late gate phase-locked loop, a new frequency offset tracking algorithm is proposed in this paper. The study shows that the algorithm can complete frequency offset tracking in AWGN channel and multipath fading channel. Furthermore under lower SNR the performance of the proposed algorithm is better by several orders compared to the common frequency offset tracking methods. If the systems have not very special requirements on timing tracking this algorithm also can complete joint tracking of frequency and timing.
2006, 28(12): 2330-2333.
Abstract:
This paper firstly analyzes the eigenvalue distribution in environment with different angle spread and DOA. Secondly, the performance of different beamforming algorithms are investigated first in diverse environment. Then a beamforming scheme based on eigenvalue distribution is proposed, which can adaptively utilize different beamforming algorithm according to the eigenvalue distribution. Simulation results show that the proposed method possesses almost the same performance as the Per-Path Per-Weight(PPPW) beamforming method, furthermore the complexity is reduced greatly.
This paper firstly analyzes the eigenvalue distribution in environment with different angle spread and DOA. Secondly, the performance of different beamforming algorithms are investigated first in diverse environment. Then a beamforming scheme based on eigenvalue distribution is proposed, which can adaptively utilize different beamforming algorithm according to the eigenvalue distribution. Simulation results show that the proposed method possesses almost the same performance as the Per-Path Per-Weight(PPPW) beamforming method, furthermore the complexity is reduced greatly.
2006, 28(12): 2334-2338.
Abstract:
Distributed radio mobile communications system consists of Base Station (BS) and some Remote Antenna Units (RAUs) connecting with BS by wireline or wireless transmission. RAU selection scheme will influence the system performance. In this paper, RAU selection criteria are investigated based on the analysis of capacity, signal transmission reliability and QoS guarantee of mobile communications system. Dynamic RAU selection methods are explored for system performance optimization. The results of selected RAU number and system performance of a dynamic RAU selection method for system capacity optimization are studied by simulation work in cellular and Manhattan scenario. Simulation results show that the system with this dynamic RAU selection method has higher system capacity and stable capacity distribution.
Distributed radio mobile communications system consists of Base Station (BS) and some Remote Antenna Units (RAUs) connecting with BS by wireline or wireless transmission. RAU selection scheme will influence the system performance. In this paper, RAU selection criteria are investigated based on the analysis of capacity, signal transmission reliability and QoS guarantee of mobile communications system. Dynamic RAU selection methods are explored for system performance optimization. The results of selected RAU number and system performance of a dynamic RAU selection method for system capacity optimization are studied by simulation work in cellular and Manhattan scenario. Simulation results show that the system with this dynamic RAU selection method has higher system capacity and stable capacity distribution.
2006, 28(12): 2339-2342.
Abstract:
The pilot-assisted channel estimation method is studied in time-division multiplexing Rayleigh fading channel. A channel tracking method is proposed by using the Chebyshev interpolation polynomials after the channel coefficients of pilot symbols in a time-slot being estimated employing ML estimation. It is compared with the segment linear interpolation method with regression. The simulation results show that the method can track the fading channel accurately. By using the proposed estimation method, the systems BER performance can be improved distinctly.
The pilot-assisted channel estimation method is studied in time-division multiplexing Rayleigh fading channel. A channel tracking method is proposed by using the Chebyshev interpolation polynomials after the channel coefficients of pilot symbols in a time-slot being estimated employing ML estimation. It is compared with the segment linear interpolation method with regression. The simulation results show that the method can track the fading channel accurately. By using the proposed estimation method, the systems BER performance can be improved distinctly.
2006, 28(12): 2343-2346.
Abstract:
Differential Unitary Space-Time Modulation (DUSTM), which is a multi-antenna modulation technique for time-varying fading channels, can obtain full diversity gains without channel state information at the receiver in slowly fading channels. For fast fading channels, however, its performance degrades considerably and suffers an irreducible error floor. In this paper, a novel Sub-Matrix Interleaved Differential Unitary Space-Time Modulation (SMI-DUSTM) scheme is proposed, in which matrix-segmentation and sub-matrix based interleaving are combined with conventional DUSTM. The constellation design criteria of SMI-DUSTM are also derived in this paper, based on the calculation of Pairwise Error Probability (PEP). The performance analysis and simulation results demonstrate that SMI-DUSTM can not only inherit the merit of DUSTM in slowly fading channels, but also maintain a good performance in fast fading channels.
Differential Unitary Space-Time Modulation (DUSTM), which is a multi-antenna modulation technique for time-varying fading channels, can obtain full diversity gains without channel state information at the receiver in slowly fading channels. For fast fading channels, however, its performance degrades considerably and suffers an irreducible error floor. In this paper, a novel Sub-Matrix Interleaved Differential Unitary Space-Time Modulation (SMI-DUSTM) scheme is proposed, in which matrix-segmentation and sub-matrix based interleaving are combined with conventional DUSTM. The constellation design criteria of SMI-DUSTM are also derived in this paper, based on the calculation of Pairwise Error Probability (PEP). The performance analysis and simulation results demonstrate that SMI-DUSTM can not only inherit the merit of DUSTM in slowly fading channels, but also maintain a good performance in fast fading channels.
2006, 28(12): 2347-2350.
Abstract:
Based on perfect sequences and orthogonal sequence sets, a new class of mutually orthogonal sets of zero correlation zone sequences is presented. Different from the construction given by Rathinakumar and Chaturvedi, the proposed method can generate more mutually orthogonal sets of zero correlation zone sequences.
Based on perfect sequences and orthogonal sequence sets, a new class of mutually orthogonal sets of zero correlation zone sequences is presented. Different from the construction given by Rathinakumar and Chaturvedi, the proposed method can generate more mutually orthogonal sets of zero correlation zone sequences.
2006, 28(12): 2351-2354.
Abstract:
Directed by Shannons disorder theory, this paper present a scheme for generating key sequences by using the sensitivity to initial values and the long time unpredictability of chaos motion. The generating scheme and process of the key sequence are described in detail. The size of the key space, randomness testing and linear complexity testing are carefully studied by computer simulation. The results indicate that the key sequences satisfy the requirements of data encrypting.
Directed by Shannons disorder theory, this paper present a scheme for generating key sequences by using the sensitivity to initial values and the long time unpredictability of chaos motion. The generating scheme and process of the key sequence are described in detail. The size of the key space, randomness testing and linear complexity testing are carefully studied by computer simulation. The results indicate that the key sequences satisfy the requirements of data encrypting.
2006, 28(12): 2355-2358.
Abstract:
Maitra and Sarkar provided a recursive construction method of balanced correlation-immune Boolean functions on n variables in 1999. In this paper, a new method is provided to construct balanced m-th order correlation-immune Boolean functions on n variables with high nonlinearity and algebraic degree n -m- 1. Compared with the original one, this method can get more functions with the same characteristics.
Maitra and Sarkar provided a recursive construction method of balanced correlation-immune Boolean functions on n variables in 1999. In this paper, a new method is provided to construct balanced m-th order correlation-immune Boolean functions on n variables with high nonlinearity and algebraic degree n -m- 1. Compared with the original one, this method can get more functions with the same characteristics.
2006, 28(12): 2359-2361.
Abstract:
Based on the characteristic of the chaotic secure communication system, transmitting the sending signal by the standard digital channel is proposed in this paper. The results show that this method is simple, flexible and reliable in the performance.
Based on the characteristic of the chaotic secure communication system, transmitting the sending signal by the standard digital channel is proposed in this paper. The results show that this method is simple, flexible and reliable in the performance.
2006, 28(12): 2362-2366.
Abstract:
EBCOT algorithm is an essential part of the new image compression standard, JPEG2000. The Tier1 part of EBCOT requires each bit-plane be scanned for three times in order to generate entropy contexts. Therefore the scanning efficiency is unacceptable，which fails to fulfill real-time compression of high quality images. So far some improvements have already been made, mainly based on PS/GOCS, and multi-window/pass-parallel coding technique. In this paper, a hardware-oriented, full pass-parallel coding architecture is presented, based on only one scanning window. This architecture is verified on FPGA. Experimental results show that its coding speed is superior to the other two main improvements. Furthermore, the coding logic adopted can be reused on the decoding stage, which facilitates sharing code/decode architecture.
EBCOT algorithm is an essential part of the new image compression standard, JPEG2000. The Tier1 part of EBCOT requires each bit-plane be scanned for three times in order to generate entropy contexts. Therefore the scanning efficiency is unacceptable，which fails to fulfill real-time compression of high quality images. So far some improvements have already been made, mainly based on PS/GOCS, and multi-window/pass-parallel coding technique. In this paper, a hardware-oriented, full pass-parallel coding architecture is presented, based on only one scanning window. This architecture is verified on FPGA. Experimental results show that its coding speed is superior to the other two main improvements. Furthermore, the coding logic adopted can be reused on the decoding stage, which facilitates sharing code/decode architecture.
2006, 28(12): 2367-2370.
Abstract:
A novel blind channel estimation scheme is proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems employing PSK modulation. This scheme is composed of obtaining a small number of possible channels by exploiting the constant modulus property and choosing a best fit over the possible channels by exploiting the finite alphabet property of information signals, thus it has low computation complexity. It estimates the channel by exploiting the second-order statistics rather than the high-order statistics of the received signal, which means that the new algorithm can achieve competitive performance. Simulation results show that the new scheme outperforms the finite-alphabet based channel estimator.
A novel blind channel estimation scheme is proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems employing PSK modulation. This scheme is composed of obtaining a small number of possible channels by exploiting the constant modulus property and choosing a best fit over the possible channels by exploiting the finite alphabet property of information signals, thus it has low computation complexity. It estimates the channel by exploiting the second-order statistics rather than the high-order statistics of the received signal, which means that the new algorithm can achieve competitive performance. Simulation results show that the new scheme outperforms the finite-alphabet based channel estimator.
2006, 28(12): 2371-2373.
Abstract:
In this paper, an iterative method is presented to estimate Hurst index, and it is applied to both FGN (Fractional Gaussian Noise) data and real traffic data. Experimental results demonstrate that this method is much faster and has smaller confidence interval compared with traditional method. Moreover, the method is stable on different scales, so it can be used as an on-line Hurst index estimator.
In this paper, an iterative method is presented to estimate Hurst index, and it is applied to both FGN (Fractional Gaussian Noise) data and real traffic data. Experimental results demonstrate that this method is much faster and has smaller confidence interval compared with traditional method. Moreover, the method is stable on different scales, so it can be used as an on-line Hurst index estimator.
2006, 28(12): 2374-2377.
Abstract:
Optical Burst Switching (OBS) is considered as an efficient switching technique for the next generation optical networks. QoS (Quality of Service) support is an important issue in OBS networks. This paper focuses mainly on the QoS algorithms based on wavelength grouping schemes, and proposes several new QoS algorithms. These algorithms can adjust the wavelengths used in each class dynamically, according to the variation of its traffic. Simulation results and comparisons with the existing algorithms show that these algorithms can provide better differentiated service, decrease the burst loss probability and improve the channel utilization.
Optical Burst Switching (OBS) is considered as an efficient switching technique for the next generation optical networks. QoS (Quality of Service) support is an important issue in OBS networks. This paper focuses mainly on the QoS algorithms based on wavelength grouping schemes, and proposes several new QoS algorithms. These algorithms can adjust the wavelengths used in each class dynamically, according to the variation of its traffic. Simulation results and comparisons with the existing algorithms show that these algorithms can provide better differentiated service, decrease the burst loss probability and improve the channel utilization.
2006, 28(12): 2378-2381.
Abstract:
This paper proposes Chinese Remainder Theorem-based Secret Sharing (CRTSS) scheme, a new Multicast Key Management (MKM) scheme, which adopts the Chinese remainder theorem and Shamirs secret sharing method. With comparing and analyzing GKMP and CRTSS schemes, the results show that CRTSS scheme overcomes high rekeying cost, the defect of conventional centralized flat schemes, improves the performance. It is a new reliable centralized flat MKM scheme.
This paper proposes Chinese Remainder Theorem-based Secret Sharing (CRTSS) scheme, a new Multicast Key Management (MKM) scheme, which adopts the Chinese remainder theorem and Shamirs secret sharing method. With comparing and analyzing GKMP and CRTSS schemes, the results show that CRTSS scheme overcomes high rekeying cost, the defect of conventional centralized flat schemes, improves the performance. It is a new reliable centralized flat MKM scheme.
2006, 28(12): 2382-2385.
Abstract:
In this paper, the principle of the network pricing strategy (Per-Packet Billing，PPB) which is based on per-packet is proposed, the concept model of PPB and the simple implementation scheme is also presented. Aimed at the three kinds of services FTP, HTTP and VoIP, comparison between PPB and traditional pricing strategy has been accomplished by NS2 simulation. The results show that the performance of PPB is better than the traditional pricing strategy in congestion control, and the packet-loss-rate is lower. Although the end-to-end delay increased, the influence to each kind of services is very small. PPB is fairness to each kind of user, and ISPs can also use price lever to optimize the network traffic and configure network resources properly.
In this paper, the principle of the network pricing strategy (Per-Packet Billing，PPB) which is based on per-packet is proposed, the concept model of PPB and the simple implementation scheme is also presented. Aimed at the three kinds of services FTP, HTTP and VoIP, comparison between PPB and traditional pricing strategy has been accomplished by NS2 simulation. The results show that the performance of PPB is better than the traditional pricing strategy in congestion control, and the packet-loss-rate is lower. Although the end-to-end delay increased, the influence to each kind of services is very small. PPB is fairness to each kind of user, and ISPs can also use price lever to optimize the network traffic and configure network resources properly.
2006, 28(12): 2386-2389.
Abstract:
In this paper, a novel scheme to detect Byzantine fault on mobile Ad hoc network is presented. A fault-tolerant algorithm is introduced combined with CBRP, which improves the security and reliability of manet(mobile Ad hoc network). Algorithm analysis shows the scheme can reduce the messages complexity effectively.
In this paper, a novel scheme to detect Byzantine fault on mobile Ad hoc network is presented. A fault-tolerant algorithm is introduced combined with CBRP, which improves the security and reliability of manet(mobile Ad hoc network). Algorithm analysis shows the scheme can reduce the messages complexity effectively.
2006, 28(12): 2390-2393.
Abstract:
This article proposes a new easy knapsack problem, based on which a novel knapsack-type public key cryptosystem is derived. The cryptosystem obtains a high knapsack density, and hence it is secure against low density subset-sum attack. Some other attacks on the scheme are also analyzed.
This article proposes a new easy knapsack problem, based on which a novel knapsack-type public key cryptosystem is derived. The cryptosystem obtains a high knapsack density, and hence it is secure against low density subset-sum attack. Some other attacks on the scheme are also analyzed.
2006, 28(12): 2394-2397.
Abstract:
Key management is one of the most important technologies on the security mechanism of wireless sensor network. Compared with all kinds of key management schemes, group key management is more suitable for wireless sensor network. According to the root-controlling and distributing group key management schemes, this paper proposes a novel layer-cluster key management technique and resolves specific defects of the two schemes. Furthermore, secret sharing mechanism based on (t, n) threshold cryptography realizes the secure communication among groups. The new proposal can not only meet security demands of wireless sensor network but also improve executing performance.
Key management is one of the most important technologies on the security mechanism of wireless sensor network. Compared with all kinds of key management schemes, group key management is more suitable for wireless sensor network. According to the root-controlling and distributing group key management schemes, this paper proposes a novel layer-cluster key management technique and resolves specific defects of the two schemes. Furthermore, secret sharing mechanism based on (t, n) threshold cryptography realizes the secure communication among groups. The new proposal can not only meet security demands of wireless sensor network but also improve executing performance.
The Fast Calculation of RCS of Electrically Large Open-Ended Cavities
Combine IPO, FMM, RPFMM, FaFFA
2006, 28(12): 2398-2401.
Abstract:
IPO+FMM method can rapidly solve the scattering of three-dimensional cavity. In the conventional Fast Multipole Method (FMM), at all directions of translation between two groups should be computed, it is expensive. The Ray-Propagation Fast Multipole Method (RPFMM) is applied to simplify the translation when two groups are well separated. In fact, the amount of translators to be calculated should be decrease with the increase of distance between two groups, to take full advantage of the characteristics; a self-adaptive ray-propagation fast multipole algorithm which can modulate the bound of cone zone of RPFMM is adopted. When the distance between two groups is enough large, Fast Far-Field Approximation (FaFFA) is used to further simplify the translation. The numerical results show this method is accurate enough and can improve efficient computing speed than IPO+FMM.
IPO+FMM method can rapidly solve the scattering of three-dimensional cavity. In the conventional Fast Multipole Method (FMM), at all directions of translation between two groups should be computed, it is expensive. The Ray-Propagation Fast Multipole Method (RPFMM) is applied to simplify the translation when two groups are well separated. In fact, the amount of translators to be calculated should be decrease with the increase of distance between two groups, to take full advantage of the characteristics; a self-adaptive ray-propagation fast multipole algorithm which can modulate the bound of cone zone of RPFMM is adopted. When the distance between two groups is enough large, Fast Far-Field Approximation (FaFFA) is used to further simplify the translation. The numerical results show this method is accurate enough and can improve efficient computing speed than IPO+FMM.
2006, 28(12): 2402-2404.
Abstract:
In this paper, the field analysis method for calculating the characteristic parameters of the output circuit in the klystron is presented. The electromagnetic component under proper assumptions and the simple equivalence is studied by three-dimension electromagnetic simulation software ISFEL3D. The theoretical analysis and the calculation show that the field analysis method can provide the calculation of characteristic parameters such as gap-impedance, coupling degree, efficiency of output cavity, resonance frequency, characteristic impedance and so on in the output circuit of the klystron. The coincidence between the cold test data and the calculation result to a certain extent preliminarily verified the reliability of the field analysis method.
In this paper, the field analysis method for calculating the characteristic parameters of the output circuit in the klystron is presented. The electromagnetic component under proper assumptions and the simple equivalence is studied by three-dimension electromagnetic simulation software ISFEL3D. The theoretical analysis and the calculation show that the field analysis method can provide the calculation of characteristic parameters such as gap-impedance, coupling degree, efficiency of output cavity, resonance frequency, characteristic impedance and so on in the output circuit of the klystron. The coincidence between the cold test data and the calculation result to a certain extent preliminarily verified the reliability of the field analysis method.
2006, 28(12): 2405-2408.
Abstract:
A context-based quantization and sorting algorithm used in wavelet image coding is proposed. The context template in the scheme is the same as JPEG2000s. The optimum context-based quantization is achieved by the means of dynamic programming for minimum relative entropy, and the pixel sorting coding is combined with optimum context quantization in significance coding. The results indicate the compression performance of the proposed algorithm is better than that of JPEG2000, especially at low bit-rate compression.
A context-based quantization and sorting algorithm used in wavelet image coding is proposed. The context template in the scheme is the same as JPEG2000s. The optimum context-based quantization is achieved by the means of dynamic programming for minimum relative entropy, and the pixel sorting coding is combined with optimum context quantization in significance coding. The results indicate the compression performance of the proposed algorithm is better than that of JPEG2000, especially at low bit-rate compression.
