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2006 Vol. 28, No. 4
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2006, 28(4): 577-581.
Abstract:
For many reasons, the artifacts can not be avoided in restored images such as Gibbs effect, grain noise and edge ring. Therefore, a new regularized approach for image restoration is proposed based on edge restoration and artifacts removing. Two new regularized constraint items are constructed in the approach with preserving classical smoothing regularized constraint item. Firstly, the degraded image is divided into edge region, texture region and flat region. Then, the increasing local variance of edge region and decreasing local variance of flat region after image restoration are used respectively to construct regularized constraint item as edge restoration constraint and artifacts removing constraint. Experimental results show the proposed approach is better than classical method in image restoration effect with two above-mentioned additional regularized constraint items.
For many reasons, the artifacts can not be avoided in restored images such as Gibbs effect, grain noise and edge ring. Therefore, a new regularized approach for image restoration is proposed based on edge restoration and artifacts removing. Two new regularized constraint items are constructed in the approach with preserving classical smoothing regularized constraint item. Firstly, the degraded image is divided into edge region, texture region and flat region. Then, the increasing local variance of edge region and decreasing local variance of flat region after image restoration are used respectively to construct regularized constraint item as edge restoration constraint and artifacts removing constraint. Experimental results show the proposed approach is better than classical method in image restoration effect with two above-mentioned additional regularized constraint items.
2006, 28(4): 582-586.
Abstract:
Mutual information is an important method for multimodal medical image registration. It measures Kullback-Leibler (KL) divergence between two probability distributions. The connection between KL divergence and Shannon inequality is investigated. Base on the connection, a novel measure, Arithmetic-Geometric (AG) mean divergence, is proposed. It can be used for alignment of remote sensing images acquired by different sensors. Unlike KL divergence, the new measure is symmetry and do not require the condition of absolute continuity to be satisfied by the probability distribution involved. AG divergence measure is applied to one-dimensional simulated signals, and to affine registration of Thematic Mapper (TM), Satellite POsitioning and Tracking (SPOT) and Synthetic Aperture Radar (SAR) remote sensing images. The performance of AG divergence measure is validated by experiments. The results show that AG measure do not require the approximate linear relation of pixel intensity value in image pairs, and is practicable even though the gray values of images are much different from each other.
Mutual information is an important method for multimodal medical image registration. It measures Kullback-Leibler (KL) divergence between two probability distributions. The connection between KL divergence and Shannon inequality is investigated. Base on the connection, a novel measure, Arithmetic-Geometric (AG) mean divergence, is proposed. It can be used for alignment of remote sensing images acquired by different sensors. Unlike KL divergence, the new measure is symmetry and do not require the condition of absolute continuity to be satisfied by the probability distribution involved. AG divergence measure is applied to one-dimensional simulated signals, and to affine registration of Thematic Mapper (TM), Satellite POsitioning and Tracking (SPOT) and Synthetic Aperture Radar (SAR) remote sensing images. The performance of AG divergence measure is validated by experiments. The results show that AG measure do not require the approximate linear relation of pixel intensity value in image pairs, and is practicable even though the gray values of images are much different from each other.
2006, 28(4): 587-591.
Abstract:
Bridge detection in remote sensing imagery has been a topic of considerable interest. In this paper, a new flow of bridge recognition in high-resolution optical imagery is proposed. Based on the prior knowledge of bridge, potential river regions are segmented and thus the centerline of rivers can be extracted after morphology erosion and dilation operations. Then the bridge detector is implemented along the river centerline in ROI regions. After that, the detected bridges are identified by using two knowledge rules and the characteristics such as location, length, width and orientation of detected bridges can be obtained. Experiments are executed on the SPOT-5 5m-resolution panchromatic imagery, and the results are showing to confirm the validity of the proposed method.
Bridge detection in remote sensing imagery has been a topic of considerable interest. In this paper, a new flow of bridge recognition in high-resolution optical imagery is proposed. Based on the prior knowledge of bridge, potential river regions are segmented and thus the centerline of rivers can be extracted after morphology erosion and dilation operations. Then the bridge detector is implemented along the river centerline in ROI regions. After that, the detected bridges are identified by using two knowledge rules and the characteristics such as location, length, width and orientation of detected bridges can be obtained. Experiments are executed on the SPOT-5 5m-resolution panchromatic imagery, and the results are showing to confirm the validity of the proposed method.
2006, 28(4): 592-596.
Abstract:
Blur identification is usually necessary in image recovery. In this paper, an improved approach is proposed on the basis of VQ-based blur identification algorithm developed by Nakagaki, In this method, Sobel operator is used for extracting feature vectors, so that the selection of the parameter of the LOG filter is avoided and this method is robust to different types of images. The dimensionality of the vector is reduced by utilizing DCT. Meantime, extension of this method to blind super-resolution image restoration is achieved. After blur identification, a super-resolution image is reconstructed from several low-resolution images obtained by different foci. Simulation results demonstrate the feasibility and validity of the method.
Blur identification is usually necessary in image recovery. In this paper, an improved approach is proposed on the basis of VQ-based blur identification algorithm developed by Nakagaki, In this method, Sobel operator is used for extracting feature vectors, so that the selection of the parameter of the LOG filter is avoided and this method is robust to different types of images. The dimensionality of the vector is reduced by utilizing DCT. Meantime, extension of this method to blind super-resolution image restoration is achieved. After blur identification, a super-resolution image is reconstructed from several low-resolution images obtained by different foci. Simulation results demonstrate the feasibility and validity of the method.
2006, 28(4): 597-602.
Abstract:
Based on the visual sampling principle, the generalized visual sampling based clustering approach VSC is proposed. The clustering approach incorporates the visual sampling principle with the famous Weber law such that it has two distinctive advantages: firstly, it is insensitive to initial conditions; secondly, the reasonable clustering number can be effectively determined by the new Weber-law-based clustering validity index. The experimental results demonstrate its success. Moreover, the link relationship between our approach and algorithm SCA (Similarity-based Clustering Algorithm) recently proposed by Yang Miin-Shen, et al. (2004) is derived. Both theoretic analyses and experimental results show that in many cases, the approach here has almost the same clustering results as algorithm SCA. This fact reveals that the approach can be used to overcome the drawback of SCA, i.e., the parameter is very difficult to be well determined.
Based on the visual sampling principle, the generalized visual sampling based clustering approach VSC is proposed. The clustering approach incorporates the visual sampling principle with the famous Weber law such that it has two distinctive advantages: firstly, it is insensitive to initial conditions; secondly, the reasonable clustering number can be effectively determined by the new Weber-law-based clustering validity index. The experimental results demonstrate its success. Moreover, the link relationship between our approach and algorithm SCA (Similarity-based Clustering Algorithm) recently proposed by Yang Miin-Shen, et al. (2004) is derived. Both theoretic analyses and experimental results show that in many cases, the approach here has almost the same clustering results as algorithm SCA. This fact reveals that the approach can be used to overcome the drawback of SCA, i.e., the parameter is very difficult to be well determined.
2006, 28(4): 603-605.
Abstract:
Collage error is a quantitative measure of the similarity between range block and best-match domain block. However, it is neglected by many fractal-based image retrieval techniques. In this paper, a new fractal coding based indexing technique using histogram of collage errors is proposed. Experimental results on a database of more than 200 texture images show that the proposed method not only reduces computational complexities, but also enhances the retrieval rate.
Collage error is a quantitative measure of the similarity between range block and best-match domain block. However, it is neglected by many fractal-based image retrieval techniques. In this paper, a new fractal coding based indexing technique using histogram of collage errors is proposed. Experimental results on a database of more than 200 texture images show that the proposed method not only reduces computational complexities, but also enhances the retrieval rate.
2006, 28(4): 606-609.
Abstract:
The rapid development of Information Retrieval(IR) and search engine improves recall rate greatly, whereas the enhancement on both precision rate and information retrieval efficiency is not clear. The research on document clustering and multi-document keyword extraction will help solve this problem. The basic idea is to cluster part of the documents returned by search engine, and automatically extract some keywords for each cluster. Thus user can judge whether the documents in each cluster are relevant to his need. In this paper the concept of document relevancy and cluster relevancy are proposed, and both word frequency and the concept relevancy model of HOWNET are used to compute cluster relevancy, which is used to guide the merging process of clusters. The experimental results show that the IR efficiency has improved greatly.
The rapid development of Information Retrieval(IR) and search engine improves recall rate greatly, whereas the enhancement on both precision rate and information retrieval efficiency is not clear. The research on document clustering and multi-document keyword extraction will help solve this problem. The basic idea is to cluster part of the documents returned by search engine, and automatically extract some keywords for each cluster. Thus user can judge whether the documents in each cluster are relevant to his need. In this paper the concept of document relevancy and cluster relevancy are proposed, and both word frequency and the concept relevancy model of HOWNET are used to compute cluster relevancy, which is used to guide the merging process of clusters. The experimental results show that the IR efficiency has improved greatly.
2006, 28(4): 610-613.
Abstract:
In this paper, the mathematic expressions of Intrinsic Mode Functions (IMFs) of the 2-dimension Local Wave Analysis (LWA) are put forward, and the 2-dimension decomposition method of HHT is developed. The clear image details have been extracted by using the method to adaptively decompose a digital image into a finite number of sub-images. That is very important for digital image processing.
In this paper, the mathematic expressions of Intrinsic Mode Functions (IMFs) of the 2-dimension Local Wave Analysis (LWA) are put forward, and the 2-dimension decomposition method of HHT is developed. The clear image details have been extracted by using the method to adaptively decompose a digital image into a finite number of sub-images. That is very important for digital image processing.
2006, 28(4): 614-618.
Abstract:
In this paper, after study of Matching Pursuit (MP) based signal sparse decomposition, a new sparse decomposition algorithm is presented based on analysis of structure property of the over-complete atom dictionary used in signal sparse decomposition. By making use of the structure property, firstly this new algorithm balances very well computers speed and memory. Then this algorithm converts very time-consuming inner product calculations in sparse decomposition into crosscorrelation calculations that are fast done by FFT. Therefore the new algorithm improves a lot the speed of signal sparse decomposition. Finally the experimental results show that the performance of the proposed algorithm is very good.
In this paper, after study of Matching Pursuit (MP) based signal sparse decomposition, a new sparse decomposition algorithm is presented based on analysis of structure property of the over-complete atom dictionary used in signal sparse decomposition. By making use of the structure property, firstly this new algorithm balances very well computers speed and memory. Then this algorithm converts very time-consuming inner product calculations in sparse decomposition into crosscorrelation calculations that are fast done by FFT. Therefore the new algorithm improves a lot the speed of signal sparse decomposition. Finally the experimental results show that the performance of the proposed algorithm is very good.
2006, 28(4): 619-623.
Abstract:
The development of Synthetic Aperture Radar (SAR) satellite is summarized. A new concept of high-elevation angle, double-side looking SAR satellite system is introduced According to the analysis of the users requirements and the key technical restriction, the performance of radar coverage is analyzed with the optimal orbital elements design for SAR satellite, and the beam position parameters design and system performance analysis are implemented. The space-ground integration approach of mission analysis for SAR satellite is proposed, basing on the characteristics of SAR payload. The computer simulation results are presented, which illustrates the validation of the new approach and the feasibility of high-elevation angle, double-side looking SAR satellite concept.
The development of Synthetic Aperture Radar (SAR) satellite is summarized. A new concept of high-elevation angle, double-side looking SAR satellite system is introduced According to the analysis of the users requirements and the key technical restriction, the performance of radar coverage is analyzed with the optimal orbital elements design for SAR satellite, and the beam position parameters design and system performance analysis are implemented. The space-ground integration approach of mission analysis for SAR satellite is proposed, basing on the characteristics of SAR payload. The computer simulation results are presented, which illustrates the validation of the new approach and the feasibility of high-elevation angle, double-side looking SAR satellite concept.
2006, 28(4): 624-627.
Abstract:
The SAR imaging of moving ship targets at sea is investigated based on high resolution airborne SAR with longer synthetic aperture time. Because the scatterers at different range cells may have different Doppler characteristics, the range migration correction for moving ship is completed by coarse and fine correction procedures. The compensations of second and higher order phase terms are implemented in range frequency - azimuth time domain. A new time-frequency analysis imaging method is presented for higher image resolution by means of the combination of Short Time Fourier Transform (STFT) and Complex Dual Apodization (CDA). The imaging results of real SAR data show the effectiveness of this method.
The SAR imaging of moving ship targets at sea is investigated based on high resolution airborne SAR with longer synthetic aperture time. Because the scatterers at different range cells may have different Doppler characteristics, the range migration correction for moving ship is completed by coarse and fine correction procedures. The compensations of second and higher order phase terms are implemented in range frequency - azimuth time domain. A new time-frequency analysis imaging method is presented for higher image resolution by means of the combination of Short Time Fourier Transform (STFT) and Complex Dual Apodization (CDA). The imaging results of real SAR data show the effectiveness of this method.
2006, 28(4): 628-631.
Abstract:
This paper presents a new method for moving target detection using SAR. With the help of short FFT analyses and CFAR detection, this method calculates the moving parameter of the target from range migration effect. An analysis on the detection precision and range of target speed is given in the following characters. The advantage and the limit of this method are indicated and the detection results from real data demonstrate the accuracy of the conclusion.
This paper presents a new method for moving target detection using SAR. With the help of short FFT analyses and CFAR detection, this method calculates the moving parameter of the target from range migration effect. An analysis on the detection precision and range of target speed is given in the following characters. The advantage and the limit of this method are indicated and the detection results from real data demonstrate the accuracy of the conclusion.
2006, 28(4): 632-637.
Abstract:
The Parametric Adaptive Matched Filter (PAMF) is a good method for the Ground Moving Target Indication (GMTI) of bistatic airborne radars. In this paper the reason for the good GMTI qualities of PAMF is worked out with the theory of matrix perturbations, and the rules of how to determinate the PAMFs order is proposed. So, the context of this paper is a potent supplement for PAMF in bistatic airborne radars.
The Parametric Adaptive Matched Filter (PAMF) is a good method for the Ground Moving Target Indication (GMTI) of bistatic airborne radars. In this paper the reason for the good GMTI qualities of PAMF is worked out with the theory of matrix perturbations, and the rules of how to determinate the PAMFs order is proposed. So, the context of this paper is a potent supplement for PAMF in bistatic airborne radars.
2006, 28(4): 638-642.
Abstract:
Target discrimination is a key technique in missile defense system, and after analyzing the defense system configuration, an integrated target discrimination mathematical model based on recursive temporal-spatial data fusion is performed, which brings the expert knowledge, environmental information and measure information into the integrated discrimination flow. During spatial fusion process, the reliability of discrimination approach is measured by Analytical Hierarchy Process (AHP), and the concept of fusion weight is introduced to measure the value of discrimination approach for participating in fusion, which is determined by reliability of discrimination approach and consensus among sensors results. During temporal fusion process, the fusion discrimination result is inherited and updated by Dempster-Shafer theory. Simulation results show that the integrated discrimination model can fuse the local decision from discrimination approaches effectively, restrain the influence of singularity and tolerate the erro=、r of discrimination.
Target discrimination is a key technique in missile defense system, and after analyzing the defense system configuration, an integrated target discrimination mathematical model based on recursive temporal-spatial data fusion is performed, which brings the expert knowledge, environmental information and measure information into the integrated discrimination flow. During spatial fusion process, the reliability of discrimination approach is measured by Analytical Hierarchy Process (AHP), and the concept of fusion weight is introduced to measure the value of discrimination approach for participating in fusion, which is determined by reliability of discrimination approach and consensus among sensors results. During temporal fusion process, the fusion discrimination result is inherited and updated by Dempster-Shafer theory. Simulation results show that the integrated discrimination model can fuse the local decision from discrimination approaches effectively, restrain the influence of singularity and tolerate the erro=、r of discrimination.
2006, 28(4): 643-646.
Abstract:
In this paper, the development of radar identification of ballistic missile warhead is summarized. Conceptions of micro-precession and micro-RCS are introduced. The aspect angle expression of a precession target is derived, and the relationship between micro-RCS and aspect angle is analyzed. Then the precession parameters and inertia ratio are estimated with micro-RCS. Inertia ratio is then used to discriminate warheads and decoys. Finally, a simulation result is provided.
In this paper, the development of radar identification of ballistic missile warhead is summarized. Conceptions of micro-precession and micro-RCS are introduced. The aspect angle expression of a precession target is derived, and the relationship between micro-RCS and aspect angle is analyzed. Then the precession parameters and inertia ratio are estimated with micro-RCS. Inertia ratio is then used to discriminate warheads and decoys. Finally, a simulation result is provided.
2006, 28(4): 647-649.
Abstract:
In this paper, numerical simulation models of crosstalk for optical switch in time-delay beamforming network and of optically phased array are built. Based on the computer simulation, influences of crosstalk on pattern, including pointing deviation and sidelobe level, and on compression of LFM received by an array are studied. Simulation results indicate that the crosstalk ratio in optical switch must be less than 20dB.
In this paper, numerical simulation models of crosstalk for optical switch in time-delay beamforming network and of optically phased array are built. Based on the computer simulation, influences of crosstalk on pattern, including pointing deviation and sidelobe level, and on compression of LFM received by an array are studied. Simulation results indicate that the crosstalk ratio in optical switch must be less than 20dB.
2006, 28(4): 650-653.
Abstract:
This paper is about energy problem in SAR jamming. A new concept of Jamming Energy Equivalence (JEE) is presented here. The concept implies that SAR warfare is still power warfare, though SAR is interference radar. This paper indicates that different jamming methods only lead to different distribution of the jamming energy in SAR image, which is useful to the choice of jamming method and the building of jamming system. In addition, this paper gives the jamming equation of SAR.
This paper is about energy problem in SAR jamming. A new concept of Jamming Energy Equivalence (JEE) is presented here. The concept implies that SAR warfare is still power warfare, though SAR is interference radar. This paper indicates that different jamming methods only lead to different distribution of the jamming energy in SAR image, which is useful to the choice of jamming method and the building of jamming system. In addition, this paper gives the jamming equation of SAR.
2006, 28(4): 654-657.
Abstract:
The Ground-Penetrating Radar (GPR) systems usually use broadband electromagnetic pulse, so the antennas must be wideband and can couple electromagnetic energy into the ground. A novel GPR antenna that the dipole with discrete exponential resistive loading is above the image plane is present in this paper. Radiation characteristics of the antenna are researched through the Finite Difference Time Domain (FDTD) method. The results show that the antenna in the paper terminates the reflections at the end of antennas through resistive loading, and it can be applied in GPR systems. Several different modes of employed antennas to influence the coupled signal and the scatter signal are also studied.
The Ground-Penetrating Radar (GPR) systems usually use broadband electromagnetic pulse, so the antennas must be wideband and can couple electromagnetic energy into the ground. A novel GPR antenna that the dipole with discrete exponential resistive loading is above the image plane is present in this paper. Radiation characteristics of the antenna are researched through the Finite Difference Time Domain (FDTD) method. The results show that the antenna in the paper terminates the reflections at the end of antennas through resistive loading, and it can be applied in GPR systems. Several different modes of employed antennas to influence the coupled signal and the scatter signal are also studied.
2006, 28(4): 658-662.
Abstract:
In the Adaptive Side Lobe Cancellation(ASLC) system of general radar, the mismatched phase of transmission line between the antenna and the former of the receiver can not be ignored usually. Otherwise, the existing method of adaptive channel equalization can only equalize the mismatched amplitude and phase of the receiver while it is disabled of the mismatched phase of the transmission line, because the reference signal is inputted in front of the receiver. Therefore the performance of ASLC is affected. Two methods of modified adaptive channel equalization are provided in this article. The mismatched amplitude and phase of the receiver and the transmission line can be revised at the same time by these two methods. The effect of them is proved with the theory analysis and experimental results.
In the Adaptive Side Lobe Cancellation(ASLC) system of general radar, the mismatched phase of transmission line between the antenna and the former of the receiver can not be ignored usually. Otherwise, the existing method of adaptive channel equalization can only equalize the mismatched amplitude and phase of the receiver while it is disabled of the mismatched phase of the transmission line, because the reference signal is inputted in front of the receiver. Therefore the performance of ASLC is affected. Two methods of modified adaptive channel equalization are provided in this article. The mismatched amplitude and phase of the receiver and the transmission line can be revised at the same time by these two methods. The effect of them is proved with the theory analysis and experimental results.
2006, 28(4): 663-666.
Abstract:
On the basis of existing references, this paper proposes a new G function algorithm for the HF high speed FH CHESS radio system. In the algorithm, the frequencies are grouped into m=2BPH subsets. The next hopping frequency is chosen according to the coding series and the corresponding relationship between the codes and the frequency subsets. The performance test results show that the algorithm has more superiority in 1-dimensional uniformity, 2-dimensional continuity and randomness of the hopping series compared with previous G function algorithm.
On the basis of existing references, this paper proposes a new G function algorithm for the HF high speed FH CHESS radio system. In the algorithm, the frequencies are grouped into m=2BPH subsets. The next hopping frequency is chosen according to the coding series and the corresponding relationship between the codes and the frequency subsets. The performance test results show that the algorithm has more superiority in 1-dimensional uniformity, 2-dimensional continuity and randomness of the hopping series compared with previous G function algorithm.
2006, 28(4): 667-670.
Abstract:
The high-resolution eigenstructure-based DOA estimation methods, such as MUSIC algorithm, have an excellent performance in ideal cases. Their performance is susceptible to noise perturbation and array error and degrade significantly when array is with error. An blind calibration method MUSIC-based is present in this paper. It need only one RF signal generator placed in the far-field without knowledge of DOA of incidence signal. Computer simulations illustrate that the method is effective and the calibration result is perfect.
The high-resolution eigenstructure-based DOA estimation methods, such as MUSIC algorithm, have an excellent performance in ideal cases. Their performance is susceptible to noise perturbation and array error and degrade significantly when array is with error. An blind calibration method MUSIC-based is present in this paper. It need only one RF signal generator placed in the far-field without knowledge of DOA of incidence signal. Computer simulations illustrate that the method is effective and the calibration result is perfect.
2006, 28(4): 671-674.
Abstract:
An new method for fast fading channel prediction using Recurrent Least Squares Support Vector Machines (RLS-SVM) combined with reconstructed embedding phase space is investigated. This algorithm is based on the chaotic behavior of the mobile multipath fading channel.The phase space of these mobile multipath fading channel coefficients are reconstructed by the theory of time delays. Based on the stability and the fractal of the chaotic attractor, the fast fading channel coefficients are predicted in their phase space based on the RLS-SVM.The proposed algorithm is a better candidate for long range prediction of the fading channel in the noise context . The experiment is carried out by utilizing fading channel data which spanes 63.829 ms. The simulation results show that the better prediction performance is acquired than the AR method when the signal to noise ratio is 15dB.
An new method for fast fading channel prediction using Recurrent Least Squares Support Vector Machines (RLS-SVM) combined with reconstructed embedding phase space is investigated. This algorithm is based on the chaotic behavior of the mobile multipath fading channel.The phase space of these mobile multipath fading channel coefficients are reconstructed by the theory of time delays. Based on the stability and the fractal of the chaotic attractor, the fast fading channel coefficients are predicted in their phase space based on the RLS-SVM.The proposed algorithm is a better candidate for long range prediction of the fading channel in the noise context . The experiment is carried out by utilizing fading channel data which spanes 63.829 ms. The simulation results show that the better prediction performance is acquired than the AR method when the signal to noise ratio is 15dB.
2006, 28(4): 675-679.
Abstract:
In this paper a novel non-coherent all-digital timing tracking scheme is described and analyzed for chip timing synchronization in direct sequence spread spectrum systems. Results of the theoretical analysis and computer simulations show that the scheme improves tracking performance as compared with the traditional delay-locked loop (DLL) in an AWGN environment. Also, the new scheme enhances the hardware simplification with respect to other traditional non-coherent schemes.
In this paper a novel non-coherent all-digital timing tracking scheme is described and analyzed for chip timing synchronization in direct sequence spread spectrum systems. Results of the theoretical analysis and computer simulations show that the scheme improves tracking performance as compared with the traditional delay-locked loop (DLL) in an AWGN environment. Also, the new scheme enhances the hardware simplification with respect to other traditional non-coherent schemes.
2006, 28(4): 680-684.
Abstract:
Wireless packet scheduling algorithms, which have been proposed for Quality of Service (QoS) for mobile users in cellular networks, depend on the fundamental idea that the service rate allocated to each user is proportional to a positive weight. Previous work on this problem has typically assumed that the channel conditions between the base station and the users are governed by a stationary stochastic process. However, such stationary assumption is not always reasonable and the study shows that the algorithms based on the stationary assumption, such as a popular algorithm known as M-LWDF，would have extremely poor performance over non-stationary channels. In this paper an opportunistic scheduling model is designed by means of fuzzy logic, which can exploit the time-vary nature of channel conditions to enhance system capacity while satisfying diverse QoS requirements. Simulations illustrate that this design can achieve better performance than previous algorithms under both stationary channel conditions and non-stationary channel conditions.
Wireless packet scheduling algorithms, which have been proposed for Quality of Service (QoS) for mobile users in cellular networks, depend on the fundamental idea that the service rate allocated to each user is proportional to a positive weight. Previous work on this problem has typically assumed that the channel conditions between the base station and the users are governed by a stationary stochastic process. However, such stationary assumption is not always reasonable and the study shows that the algorithms based on the stationary assumption, such as a popular algorithm known as M-LWDF，would have extremely poor performance over non-stationary channels. In this paper an opportunistic scheduling model is designed by means of fuzzy logic, which can exploit the time-vary nature of channel conditions to enhance system capacity while satisfying diverse QoS requirements. Simulations illustrate that this design can achieve better performance than previous algorithms under both stationary channel conditions and non-stationary channel conditions.
2006, 28(4): 685-689.
Abstract:
In this paper, a phase estimator of serial search acquisition is proposed for Direct-Sequences Spread- Spectrum(DS/SS) systems. According to the cross correlation between the PN signal and the auxiliary signals with the different phases, an exact and valid estimation of improving direction and magnitude for the local PN generator is given, by which half the mean acquisition can be reduced. Analysis in theory and numerical results show that the proposed method can achieve acquisition at least two times faster than the conventional serial search method for the PN sequences which periods are more than 511 in normal operating condition.
In this paper, a phase estimator of serial search acquisition is proposed for Direct-Sequences Spread- Spectrum(DS/SS) systems. According to the cross correlation between the PN signal and the auxiliary signals with the different phases, an exact and valid estimation of improving direction and magnitude for the local PN generator is given, by which half the mean acquisition can be reduced. Analysis in theory and numerical results show that the proposed method can achieve acquisition at least two times faster than the conventional serial search method for the PN sequences which periods are more than 511 in normal operating condition.
2006, 28(4): 690-692.
Abstract:
An improved nonlinear technology of narrow-band interference suppression in DSSS communications is proposed. Compared with other Volterra filters, the algorithm proposed here can largely reduce the computational weight in a very simple way. Based on this algorithm, a DSSS receiver based on Volterra filters is investigated and simulation result proves its advantages.
An improved nonlinear technology of narrow-band interference suppression in DSSS communications is proposed. Compared with other Volterra filters, the algorithm proposed here can largely reduce the computational weight in a very simple way. Based on this algorithm, a DSSS receiver based on Volterra filters is investigated and simulation result proves its advantages.
2006, 28(4): 693-697.
Abstract:
Symbol timing estimation is one of key problems in OFDM systems. In this paper a new symbol timing estimation algorithm based on a training symbol is proposed. The study shows that the new algorithm is not affected by carrier frequency offset basically, and has strong characteristic of resisting noise. Through adopting this algorithm the timing error is shortened to a half of the sample time interval. Furthermore the frequency-domain training symbol can be used to estimate carrier frequency offset, so only a training symbol is needed to complete joint acquisition of symbol timing and carrier frequency offset.
Symbol timing estimation is one of key problems in OFDM systems. In this paper a new symbol timing estimation algorithm based on a training symbol is proposed. The study shows that the new algorithm is not affected by carrier frequency offset basically, and has strong characteristic of resisting noise. Through adopting this algorithm the timing error is shortened to a half of the sample time interval. Furthermore the frequency-domain training symbol can be used to estimate carrier frequency offset, so only a training symbol is needed to complete joint acquisition of symbol timing and carrier frequency offset.
2006, 28(4): 698-702.
Abstract:
In this paper, the current analysis focuses on the influence of demodulation performance in multipath fading propagation environments, which results from the pilot power variation of Pilot Symbol Assisted Modulation (PSAM) M-QAM in Orthogonal Frequency Division Multiplexing (OFDM) systems. The Pilot-to-Data power Ratio (PDR) is optimized analytically, and the loss due to imperfect channel estimation is calculated. Theoretical and simulation results show that the optimum PDR is effected by the Signal-to-Noise Ratio (SNR), Doppler frequency and interpolation size etc. When the optimization parameter of PDR is used, the power of system transmission is the minimum but the same bit error rate (BER) is obtained.
In this paper, the current analysis focuses on the influence of demodulation performance in multipath fading propagation environments, which results from the pilot power variation of Pilot Symbol Assisted Modulation (PSAM) M-QAM in Orthogonal Frequency Division Multiplexing (OFDM) systems. The Pilot-to-Data power Ratio (PDR) is optimized analytically, and the loss due to imperfect channel estimation is calculated. Theoretical and simulation results show that the optimum PDR is effected by the Signal-to-Noise Ratio (SNR), Doppler frequency and interpolation size etc. When the optimization parameter of PDR is used, the power of system transmission is the minimum but the same bit error rate (BER) is obtained.
2006, 28(4): 703-706.
Abstract:
The rate control mechanism for reverse link of CDMA2000 is introduced, and an implementing scheme in CDMA2000 1x Release C is proposed. Analysis and system simulation show that the scheme can improve the throughput of reverse link with RoT (Rise-over-Thermal) stabilized, and lead to less delay than scheduling mode, which can better meet the requirement for delivering delay-sensitive services.
The rate control mechanism for reverse link of CDMA2000 is introduced, and an implementing scheme in CDMA2000 1x Release C is proposed. Analysis and system simulation show that the scheme can improve the throughput of reverse link with RoT (Rise-over-Thermal) stabilized, and lead to less delay than scheduling mode, which can better meet the requirement for delivering delay-sensitive services.
2006, 28(4): 707-711.
Abstract:
In this paper a novel block encryption algorithm, which is called CFCEA, is proposed by combining the one dimensional discrete chaotic map and Feistel network. The algorithm operates on 64bit plaintext blocks, and the master key is 128 bit long, and an auxiliary key with size of 128 bit is exploited. Within the round function, the logistic chaotic map and three algebraic group operations are mixed. Moreover, the subkeys schedule is specially designed for the consideration of the security. The cryptographic properties of the algorithm are analyzed, and the results indicate that this algorithm satisfies the strict avalanche criterion and as a result, the diffusion and confusion properties of the algorithm are very ideal. Furthermore, when the block length is 64bit, the approximately upper bound of differential probability and linear probability of CFCEA is 2-52.92 and 2-49.206, respectively. This shows that the algorithm can resist differential and linear cryptanalysis with some strength.
In this paper a novel block encryption algorithm, which is called CFCEA, is proposed by combining the one dimensional discrete chaotic map and Feistel network. The algorithm operates on 64bit plaintext blocks, and the master key is 128 bit long, and an auxiliary key with size of 128 bit is exploited. Within the round function, the logistic chaotic map and three algebraic group operations are mixed. Moreover, the subkeys schedule is specially designed for the consideration of the security. The cryptographic properties of the algorithm are analyzed, and the results indicate that this algorithm satisfies the strict avalanche criterion and as a result, the diffusion and confusion properties of the algorithm are very ideal. Furthermore, when the block length is 64bit, the approximately upper bound of differential probability and linear probability of CFCEA is 2-52.92 and 2-49.206, respectively. This shows that the algorithm can resist differential and linear cryptanalysis with some strength.
2006, 28(4): 712-716.
Abstract:
With characteristic matrix of Boolean function, a necessary and sufficient condition is given on a Boolean function satisfying the propagation criterion on vector sGFn(2), which provides n3. On the basis of it, the necessary and sufficient conditions are given on a Boolean function satisfying Strict Avalanche Criterion (SAC) and on a balanced SAC function which achieves the maximum degree and no nonzero linear structure. Finally, two special filling vacancies in the proper order methods of construction are presented.
With characteristic matrix of Boolean function, a necessary and sufficient condition is given on a Boolean function satisfying the propagation criterion on vector sGFn(2), which provides n3. On the basis of it, the necessary and sufficient conditions are given on a Boolean function satisfying Strict Avalanche Criterion (SAC) and on a balanced SAC function which achieves the maximum degree and no nonzero linear structure. Finally, two special filling vacancies in the proper order methods of construction are presented.
2006, 28(4): 717-720.
Abstract:
A reconfigurable and fast architecture over Galois field GF (2m )(1＜mM) is presented based on the improved serial multiplier. The value m, of the irreducible polynomial degree, can changed by adding a set of configuring signals and logic circuits, which results in that the multiplier architecture is reconfigurable and programmable without changing the hardware. The proposed multiplier architecture has high order of flexibility and low hardware complexity. Compared with the traditional serial multiplier, it can obtain twice speed-up. It suits high-security cryptographic applications with variable finite fields and low complexity requirements.
A reconfigurable and fast architecture over Galois field GF (2m )(1＜mM) is presented based on the improved serial multiplier. The value m, of the irreducible polynomial degree, can changed by adding a set of configuring signals and logic circuits, which results in that the multiplier architecture is reconfigurable and programmable without changing the hardware. The proposed multiplier architecture has high order of flexibility and low hardware complexity. Compared with the traditional serial multiplier, it can obtain twice speed-up. It suits high-security cryptographic applications with variable finite fields and low complexity requirements.
2006, 28(4): 721-727.
Abstract:
All the existing chaotic communication techniques are simply classified into two catalogues，their implementation principles and characteristics are outlined，the corresponding valuable realizing schemes are introduced for comparing their advantages and disadvantages in application. Then a zero dynamical nonlinear invertible communication scheme with chaos driving is proposed. Its performances，such as encryption security，defending ciphertext attack， noise robust，etc. are extensively analysed by simulation. Its necessity to synchronization for application and the way to solve the problem are also discussed.
All the existing chaotic communication techniques are simply classified into two catalogues，their implementation principles and characteristics are outlined，the corresponding valuable realizing schemes are introduced for comparing their advantages and disadvantages in application. Then a zero dynamical nonlinear invertible communication scheme with chaos driving is proposed. Its performances，such as encryption security，defending ciphertext attack， noise robust，etc. are extensively analysed by simulation. Its necessity to synchronization for application and the way to solve the problem are also discussed.
2006, 28(4): 728-731.
Abstract:
A new no-reference quality assessment method for block-coding video is presented in this paper. Firstly, a new blocking artifact metric is presented based on Human Visual System(HVS) taking into account of the luminance masking and activity masking characteristics. Then, with consideration of the effect of filtering, a method is proposed for assessing the quality of the reconstructed videos compressed with different block-coding algorithms. Experimental results show that the proposed no-reference quality assessment method has good consistency with subjective quality assessment methods.
A new no-reference quality assessment method for block-coding video is presented in this paper. Firstly, a new blocking artifact metric is presented based on Human Visual System(HVS) taking into account of the luminance masking and activity masking characteristics. Then, with consideration of the effect of filtering, a method is proposed for assessing the quality of the reconstructed videos compressed with different block-coding algorithms. Experimental results show that the proposed no-reference quality assessment method has good consistency with subjective quality assessment methods.
2006, 28(4): 732-735.
Abstract:
A transmit preprocessing technique for downlink spatial multiplexing in multi-user MIMO channels is proposed in this paper. Through adding additional constraint to the joint TX-RX MMSE optimization scheme the equivalent channel can be changed from block-diagonalization to complete diagonalization. Thus both MUI (Multi-User Interference) and per-user multi-stream interference can be canceled simultaneously. Besides the general advantage of the algorithms based on block-diagonalization, the modified algorithm is much more feasible and has the advantage of simplifying the receivers.
A transmit preprocessing technique for downlink spatial multiplexing in multi-user MIMO channels is proposed in this paper. Through adding additional constraint to the joint TX-RX MMSE optimization scheme the equivalent channel can be changed from block-diagonalization to complete diagonalization. Thus both MUI (Multi-User Interference) and per-user multi-stream interference can be canceled simultaneously. Besides the general advantage of the algorithms based on block-diagonalization, the modified algorithm is much more feasible and has the advantage of simplifying the receivers.
2006, 28(4): 736-740.
Abstract:
This paper considers blind interference suppression for a space-time block coded MultiCarrier CDMA (MC-CDMA) system. By investigating the code space in frequency domain and the data vector space of the multipath signals, the noise-subspace-based approach is used to perform blind channel estimation. A modified ULV updating algorithm is applied to performing noise subspace tracking. The algorithm does not require rank estimation of the correlation matrix, and estimate directly the noise subspace. To suppress Multiuser Access Interference (MAI), a Projection-based Auxiliary Vector (PAV) algorithm is proposed. A reconstructed Maximum Ratio Combining (MRC) filtering vector can be evaluated by using the outputs of the last filtering vector. Taking the orthogonal projection of the reconstructed filtering vector onto the space spanned by the basic filtering vector and the previously derived auxiliary vector as an auxiliary vector, a new filtering vector can be formed by linearly combining the last filtering vector and newly generated auxiliary vector. Simulation results show the effectiveness of the proposed algorithms.
This paper considers blind interference suppression for a space-time block coded MultiCarrier CDMA (MC-CDMA) system. By investigating the code space in frequency domain and the data vector space of the multipath signals, the noise-subspace-based approach is used to perform blind channel estimation. A modified ULV updating algorithm is applied to performing noise subspace tracking. The algorithm does not require rank estimation of the correlation matrix, and estimate directly the noise subspace. To suppress Multiuser Access Interference (MAI), a Projection-based Auxiliary Vector (PAV) algorithm is proposed. A reconstructed Maximum Ratio Combining (MRC) filtering vector can be evaluated by using the outputs of the last filtering vector. Taking the orthogonal projection of the reconstructed filtering vector onto the space spanned by the basic filtering vector and the previously derived auxiliary vector as an auxiliary vector, a new filtering vector can be formed by linearly combining the last filtering vector and newly generated auxiliary vector. Simulation results show the effectiveness of the proposed algorithms.
2006, 28(4): 741-746.
Abstract:
An efficient JPEG2000 encoder is proposed and implemented with high pipeline and low memory architecture. Dual buffers to save the wavelet coefficients, pre-rate allocation and byte expression for Rate-Distortion (RD) slope are used to reduce on-chip memory size. Pipeline and parallel architecture is used in Discrete Wavelet Transform (DWT), Bit-Plane Encoder (BPE) and Arithmetic Encoder (AE) to increase the part circuits encoding speed, searching the truncated RD slope in byte address space increases the packet formatting speed of Tier2. Problems met in system implementation such as clock distribution, SDRAM control of frame buffer and chrominance-transformation are also designed with optimization. The encoder is verified on FPGA platform. Performance of the encoder is as follows: the size of tile is up to 256256 with code block in size of 3232, input sampling rate is up to 45Msamples/s when Tier1 is working at the clock of 100 MHz, difference of the PSNR of images compressed by the proposed encoder and JASPER is less than 0.5dB at the rate of 0.4 bit per sample (bps). Equivalent gates synthesized are about 109k and on-chip RAM is 862kb.
An efficient JPEG2000 encoder is proposed and implemented with high pipeline and low memory architecture. Dual buffers to save the wavelet coefficients, pre-rate allocation and byte expression for Rate-Distortion (RD) slope are used to reduce on-chip memory size. Pipeline and parallel architecture is used in Discrete Wavelet Transform (DWT), Bit-Plane Encoder (BPE) and Arithmetic Encoder (AE) to increase the part circuits encoding speed, searching the truncated RD slope in byte address space increases the packet formatting speed of Tier2. Problems met in system implementation such as clock distribution, SDRAM control of frame buffer and chrominance-transformation are also designed with optimization. The encoder is verified on FPGA platform. Performance of the encoder is as follows: the size of tile is up to 256256 with code block in size of 3232, input sampling rate is up to 45Msamples/s when Tier1 is working at the clock of 100 MHz, difference of the PSNR of images compressed by the proposed encoder and JASPER is less than 0.5dB at the rate of 0.4 bit per sample (bps). Equivalent gates synthesized are about 109k and on-chip RAM is 862kb.
2006, 28(4): 747-752.
Abstract:
A contention resolution method based on the priority of the bursts for optical switching networks is proposed in this paper. When the contention occur, firstly, the burst segmentation method is used on the bursts, secondly, based on the burst segment method a burst composite assembly technique is proposed, finally, the computer simulation is made to verify the result of the method, the fact that the method could commendably protect the high-priority bursts and IP packets could been clearly seen from the simulation, so that it could support good QoS for the networks.
A contention resolution method based on the priority of the bursts for optical switching networks is proposed in this paper. When the contention occur, firstly, the burst segmentation method is used on the bursts, secondly, based on the burst segment method a burst composite assembly technique is proposed, finally, the computer simulation is made to verify the result of the method, the fact that the method could commendably protect the high-priority bursts and IP packets could been clearly seen from the simulation, so that it could support good QoS for the networks.
2006, 28(4): 753-756.
Abstract:
The problem of seeking monitor-nodes for measuring the network traffic is regarded as the problem of finding out the minimum weak vertex cover of a graph which is NP-hard. An approximation algorithm is proposed in this paper based on the concept of incidence matrix in Graph. Also the complexity of the algorithm is analyzed. Furthermore, the algorithm is expanded to seek the minimum weak vertex cover for a graph that has weights on the nodes. The theoretical analysis and the simulation results show that the novel algorithm is more scalable than the traditional algorithms, and can find smaller weak vertex cover.
The problem of seeking monitor-nodes for measuring the network traffic is regarded as the problem of finding out the minimum weak vertex cover of a graph which is NP-hard. An approximation algorithm is proposed in this paper based on the concept of incidence matrix in Graph. Also the complexity of the algorithm is analyzed. Furthermore, the algorithm is expanded to seek the minimum weak vertex cover for a graph that has weights on the nodes. The theoretical analysis and the simulation results show that the novel algorithm is more scalable than the traditional algorithms, and can find smaller weak vertex cover.
2006, 28(4): 757-759.
Abstract:
In this paper, the FDTD with least square fitting method is used to calculate the S parameters of PBG filter structures, Furthermore, the least square fitting method is employed combined with FDTD to reduce the iterative steps. To show the accuracy of the method, a simulated result is given in the latter part of the paper and various comparisons are made for such a demonstration.
In this paper, the FDTD with least square fitting method is used to calculate the S parameters of PBG filter structures, Furthermore, the least square fitting method is employed combined with FDTD to reduce the iterative steps. To show the accuracy of the method, a simulated result is given in the latter part of the paper and various comparisons are made for such a demonstration.
2006, 28(4): 760-764.
Abstract:
Based on the beam-wave mode-coupling theory, a principle of gyrotron device utilizing a hybrid interaction scheme of Backward-Wave Oscillator, Klystron Ballistic-Bunching and Traveling-Wave Tube (Gyro-BWO-KBB-TWT) is presented in this paper. Theoretical analysis of a Ka-band second harmonic tunable gyro-BWO-KBB-TWT indicates that the device efficiency of 40% and magnetic tuning bandwidth of 10% are achieved. A gyrotron oscillator employing the hybrid interaction scheme can realize highly efficient, high-power output and broadband continuous magnetic tuning in millimeter wave band.
Based on the beam-wave mode-coupling theory, a principle of gyrotron device utilizing a hybrid interaction scheme of Backward-Wave Oscillator, Klystron Ballistic-Bunching and Traveling-Wave Tube (Gyro-BWO-KBB-TWT) is presented in this paper. Theoretical analysis of a Ka-band second harmonic tunable gyro-BWO-KBB-TWT indicates that the device efficiency of 40% and magnetic tuning bandwidth of 10% are achieved. A gyrotron oscillator employing the hybrid interaction scheme can realize highly efficient, high-power output and broadband continuous magnetic tuning in millimeter wave band.
2006, 28(4): 765-768.
Abstract:
A new complex open-cavity structure is used for improving the mode selectivity of gyrotron resonator by means of setting a right rational position of the common wall and the shape of coupling slots between the inter- and outer- cavities. The characteristics of the resonant modes in the cavity are simulated and analyzed with Ansoft HFSS code. It is shown that mode competition can be effectively suppressed with the new cavity structure.
A new complex open-cavity structure is used for improving the mode selectivity of gyrotron resonator by means of setting a right rational position of the common wall and the shape of coupling slots between the inter- and outer- cavities. The characteristics of the resonant modes in the cavity are simulated and analyzed with Ansoft HFSS code. It is shown that mode competition can be effectively suppressed with the new cavity structure.
