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2010 Vol. 32, No. 8
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2010, 32(8): 1779-1785.
doi: 10.3724/SP.J.1146.2009.01194
Abstract:
Image quality estimation is an important part of performance evaluation for Automatic Target Recognition (ATR). Traditional image metrics are focused on single image, and there is no valid method to estimate the quality of image sequence. According to the above problem, this paper proposes the concept Inter-Frame Change Degree of Target (IFCDT) which is used for quantitatively describing image sequence quality for the first time. There are three key elements in the formula of the proposed metric, which embody the information of inter-frame change of target image texture, inter-frame change of target size and inter-frame change of target position respectively. To validate this image sequence metric, this paper designs an experiment for analyzing the relationship of IFCDT and ATR algorithm performance, while the samples of this experiment are actual target image sequences. The experiment result shows that there is a good monotone relationship between the image sequence metric and algorithm actual performance. Therefore, it can be concluded that the metric is a valid criterion to evaluate the quality of target image sequence.
Image quality estimation is an important part of performance evaluation for Automatic Target Recognition (ATR). Traditional image metrics are focused on single image, and there is no valid method to estimate the quality of image sequence. According to the above problem, this paper proposes the concept Inter-Frame Change Degree of Target (IFCDT) which is used for quantitatively describing image sequence quality for the first time. There are three key elements in the formula of the proposed metric, which embody the information of inter-frame change of target image texture, inter-frame change of target size and inter-frame change of target position respectively. To validate this image sequence metric, this paper designs an experiment for analyzing the relationship of IFCDT and ATR algorithm performance, while the samples of this experiment are actual target image sequences. The experiment result shows that there is a good monotone relationship between the image sequence metric and algorithm actual performance. Therefore, it can be concluded that the metric is a valid criterion to evaluate the quality of target image sequence.
2010, 32(8): 1786-1791.
doi: 10.3724/SP.J.1146.2009.01120
Abstract:
Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) can track the brain white matter fiber by tracing the local tensor orientation and reconstruct the three dimensional image noninvasively. The commonly used tracking method is usually based on the local diffusion information and insufficient to consider the geometrical structure and fractional anisotropy which is constrained by anatomical structure and physiological function of human been. Therefore, a novel method of fiber tracking based on Bayesian constrained stochastic framework is proposed. In this method, the correlation of tracking direction to both the diffusion directions of the current voxel and the structure information of the current fiber segment is considered synthetically. Meanwhile, the two components are constrained by the fractional anisotropy and angle of the fiber curve respectively. The probability distributions of the tracking directions of the next voxel is estimated under the Bayesian constrained stochastic framework. Then, according to the probability distributions, the fiber bundle is sampled with Markov Chain Monte Carlo method and the 3D image of its structure is reconstructed under multiply tracking. By the method, imaging simulations using a synthetic diffusion tensor dataset and imaging experiments using an in vivo brain DT-MRI dataset have been done. The results of the simulations and experiments demonstrate that using the method proposed, brain white matter fiber can be reconstructed properly as expected, more reliably and reproducibly compared with the common methods.
Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) can track the brain white matter fiber by tracing the local tensor orientation and reconstruct the three dimensional image noninvasively. The commonly used tracking method is usually based on the local diffusion information and insufficient to consider the geometrical structure and fractional anisotropy which is constrained by anatomical structure and physiological function of human been. Therefore, a novel method of fiber tracking based on Bayesian constrained stochastic framework is proposed. In this method, the correlation of tracking direction to both the diffusion directions of the current voxel and the structure information of the current fiber segment is considered synthetically. Meanwhile, the two components are constrained by the fractional anisotropy and angle of the fiber curve respectively. The probability distributions of the tracking directions of the next voxel is estimated under the Bayesian constrained stochastic framework. Then, according to the probability distributions, the fiber bundle is sampled with Markov Chain Monte Carlo method and the 3D image of its structure is reconstructed under multiply tracking. By the method, imaging simulations using a synthetic diffusion tensor dataset and imaging experiments using an in vivo brain DT-MRI dataset have been done. The results of the simulations and experiments demonstrate that using the method proposed, brain white matter fiber can be reconstructed properly as expected, more reliably and reproducibly compared with the common methods.
2010, 32(8): 1792-1796.
doi: 10.3724/SP.J.1146.2009.00922
Abstract:
A novel color image segmentation method is proposed in this paper. Multidimensional space is defined by using the PCA technique to computing the most discriminating color components for a given color image among a set of conventional color spaces. Then, training samples for every region in the color image is selected and these samples is trained by clonal selection algorithm to obtain clustering center of every region. Finally, output the segmentation result according to these clustering centers. Due to the nonlinear classification property of clonal selection algorithm and adaptive definition of a multidimensional space for a given color image, the segmentation result can be obtained accurately and quickly. In experiments, different color images are used to test the performance of the suggested method. The result indicated that this method performs more robustness and adaptability.
A novel color image segmentation method is proposed in this paper. Multidimensional space is defined by using the PCA technique to computing the most discriminating color components for a given color image among a set of conventional color spaces. Then, training samples for every region in the color image is selected and these samples is trained by clonal selection algorithm to obtain clustering center of every region. Finally, output the segmentation result according to these clustering centers. Due to the nonlinear classification property of clonal selection algorithm and adaptive definition of a multidimensional space for a given color image, the segmentation result can be obtained accurately and quickly. In experiments, different color images are used to test the performance of the suggested method. The result indicated that this method performs more robustness and adaptability.
2010, 32(8): 1797-1801.
doi: 10.3724/SP.J.1146.2009.01210
Abstract:
A novel signal model with missing-data is proposed to directly blindly despread the long-code Direct Sequence Spread Spectrum (DS-SS) signals with unknown carrier frequency. The long-code DS-SS signals are represented as the short-code ones with missing data, and then the blind synchronization algorithm of the short-code DS-SS signals is extended to the long-code ones. Finally, the Alternative Projection (AP) algorithm is used to restore the signal subspace so that blind despreading can be obtained. The simulation results show that the proposed approach is immune to the unknown carrier and show good performance in low-SNR scenarios.
A novel signal model with missing-data is proposed to directly blindly despread the long-code Direct Sequence Spread Spectrum (DS-SS) signals with unknown carrier frequency. The long-code DS-SS signals are represented as the short-code ones with missing data, and then the blind synchronization algorithm of the short-code DS-SS signals is extended to the long-code ones. Finally, the Alternative Projection (AP) algorithm is used to restore the signal subspace so that blind despreading can be obtained. The simulation results show that the proposed approach is immune to the unknown carrier and show good performance in low-SNR scenarios.
2010, 32(8): 1802-1805.
doi: 10.3724/SP.J.1146.2009.00718
Abstract:
The Chinese remainder theorem is not robust in the sense that a small error in its remainders may cause a large error in the determined integer by the CRT. In this paper, a Generalized Robust Chinese Remainder Theorem (GRCRT) is presented when moduli are not pair-wisely co-prime and the remainders have errors. The new theorem is proofed in detail; The formulas of the estimated integer and estimation error upper bound are provided. The RCRT is then applied to determine the frequency when the signal waveforms are undersampled. Simulation results show that new algorithm is robust with considering residue errors and can use to the area of digital signal processing and will have more applications to other areas.
The Chinese remainder theorem is not robust in the sense that a small error in its remainders may cause a large error in the determined integer by the CRT. In this paper, a Generalized Robust Chinese Remainder Theorem (GRCRT) is presented when moduli are not pair-wisely co-prime and the remainders have errors. The new theorem is proofed in detail; The formulas of the estimated integer and estimation error upper bound are provided. The RCRT is then applied to determine the frequency when the signal waveforms are undersampled. Simulation results show that new algorithm is robust with considering residue errors and can use to the area of digital signal processing and will have more applications to other areas.
2010, 32(8): 1806-1811.
doi: 10.3724/SP.J.1146.2009.01015
Abstract:
The modeling and reasoning with uncertain context information is one of key problems of building context-aware applications in pervasive computing environment. In this paper, a method of modeling uncertain contexts is proposed by combining the D-S theory with ontology model. And also an improved evidences combination rule is presented not only to solve the D-S theory limitations in the case of high-degree conflict evidences but also to make the reasoning have self-adaptability. Then the uncertain reasoning algorithm is designed and implemented. Finally, the feasibility, rationality and effectiveness of this approach are verified through an e-health use case of the prototype system.
The modeling and reasoning with uncertain context information is one of key problems of building context-aware applications in pervasive computing environment. In this paper, a method of modeling uncertain contexts is proposed by combining the D-S theory with ontology model. And also an improved evidences combination rule is presented not only to solve the D-S theory limitations in the case of high-degree conflict evidences but also to make the reasoning have self-adaptability. Then the uncertain reasoning algorithm is designed and implemented. Finally, the feasibility, rationality and effectiveness of this approach are verified through an e-health use case of the prototype system.
2010, 32(8): 1812-1817.
doi: 10.3724/SP.J.1146.2009.01127
Abstract:
Spatial motion feature is one of main target features for missile target identification. This paper investigates micro-motion of the missile target. Time-frequency analysis is used to extract micro-Doppler signature, based on which an approach is proposed for estimating the linear sum of the micro-Dopplers of scatters. Motion parameters can be extracted by applying Fourier Transform to the sum. Then waveform entropy is presented for the missile identification. The simulation results and the recognition results validate the effectiveness of theoretical analysis.
Spatial motion feature is one of main target features for missile target identification. This paper investigates micro-motion of the missile target. Time-frequency analysis is used to extract micro-Doppler signature, based on which an approach is proposed for estimating the linear sum of the micro-Dopplers of scatters. Motion parameters can be extracted by applying Fourier Transform to the sum. Then waveform entropy is presented for the missile identification. The simulation results and the recognition results validate the effectiveness of theoretical analysis.
2010, 32(8): 1818-1824.
doi: 10.3724/SP.J.1146.2009.00870
Abstract:
The conventional methods for the stepped-frequency high resolution ISAR imaging are usually difficult to accurately estimate the velocity and acceleration of a moving target. Thus, the residual phase error via the motion compensation has a serious effect on an ISAR image. Consequently, a novel method based on the adjacent correlation and the coherent processing for realizing the high resolution ISAR imaging is proposed in this paper. The motion parameters can be estimated by the adjacent correlation and be used for the compensation of the range migration. Then, the phase error among all sub-pulse in a pulse team also can be obtained and compensated by the coherent processing. Thus, by the bandwidth combination in the frequency dimension and the range-Doppler algorithm, the high resolution ISAR image can be obtained. This method has some advantages of the precise phase compensation and the light computation load. Finally, the simulated and real data confirm the effectiveness of proposed method in this paper.
The conventional methods for the stepped-frequency high resolution ISAR imaging are usually difficult to accurately estimate the velocity and acceleration of a moving target. Thus, the residual phase error via the motion compensation has a serious effect on an ISAR image. Consequently, a novel method based on the adjacent correlation and the coherent processing for realizing the high resolution ISAR imaging is proposed in this paper. The motion parameters can be estimated by the adjacent correlation and be used for the compensation of the range migration. Then, the phase error among all sub-pulse in a pulse team also can be obtained and compensated by the coherent processing. Thus, by the bandwidth combination in the frequency dimension and the range-Doppler algorithm, the high resolution ISAR image can be obtained. This method has some advantages of the precise phase compensation and the light computation load. Finally, the simulated and real data confirm the effectiveness of proposed method in this paper.
2010, 32(8): 1825-1830.
doi: 10.3724/SP.J.1146.2009.00835
Abstract:
Estimating targets dimension using High Resolution Range Profile (HRRP) is an important means of character extraction and target recognition of ballistic missile mid-course defense radars. In this paper, a new estimation method of middle-course ballistic missiles dimension using multiple HRRPs under the condition of precession is presented. The function of the targets HRRP length and the targets real dimension and precession parameters is derived, and the measurement model of HRRP length is constructed, based on which a maximal likelihood estimation method is adopted to realize the estimation of the targets dimension. Finally, the simulation results of dimension estimation based on both simulation data and measurement data of one real warhead are given, which validates the validity of the method.
Estimating targets dimension using High Resolution Range Profile (HRRP) is an important means of character extraction and target recognition of ballistic missile mid-course defense radars. In this paper, a new estimation method of middle-course ballistic missiles dimension using multiple HRRPs under the condition of precession is presented. The function of the targets HRRP length and the targets real dimension and precession parameters is derived, and the measurement model of HRRP length is constructed, based on which a maximal likelihood estimation method is adopted to realize the estimation of the targets dimension. Finally, the simulation results of dimension estimation based on both simulation data and measurement data of one real warhead are given, which validates the validity of the method.
2010, 32(8): 1831-1836.
doi: 10.3724/SP.J.1146.2009.00979
Abstract:
Adaptive space-time coding design is investigated for improving the detection performance of MIMO array radar, with multiple targets and space-time correlation property of clutter RCS considered in this paper. Optimal principle and two suboptimal principles are derived for adaptive space-time coding design, and the interrelation among the three principles, orthogonal space-time coding design and beampattern matching design is clarified. The numerical simulations show that all of the adaptive space-time coding vectors designed by the three principles can significantly enhance the signal-to-clutter plus noise-ratio at the output of the detector, and thus improve the detection performance of the MIMO array radar.
Adaptive space-time coding design is investigated for improving the detection performance of MIMO array radar, with multiple targets and space-time correlation property of clutter RCS considered in this paper. Optimal principle and two suboptimal principles are derived for adaptive space-time coding design, and the interrelation among the three principles, orthogonal space-time coding design and beampattern matching design is clarified. The numerical simulations show that all of the adaptive space-time coding vectors designed by the three principles can significantly enhance the signal-to-clutter plus noise-ratio at the output of the detector, and thus improve the detection performance of the MIMO array radar.
2010, 32(8): 1837-1842.
doi: 10.3724/SP.J.1146.2009.01080
Abstract:
Wideband radars have higher range resolution than narrowband radars, and the target fluctuation is less. The wideband and narrowband returns of the wideband non-fluctuation target model, the wideband Rayleigh target model and the wideband Ricean target model are analyzed, and the detection probabilities of them in white Gaussian noise are deduced. The detection curves show that the wideband radars outperform the narrowband radars in the case of high detection probabilities; but the integration loss of the wideband radar energy integration detector is increased with the increasing of the wideband radar range resolution, and this factor causes that the detection predominance of the wideband radars to the narrowband radars is meaningless when the bandwidth of the radar is increased to a certain extent.
Wideband radars have higher range resolution than narrowband radars, and the target fluctuation is less. The wideband and narrowband returns of the wideband non-fluctuation target model, the wideband Rayleigh target model and the wideband Ricean target model are analyzed, and the detection probabilities of them in white Gaussian noise are deduced. The detection curves show that the wideband radars outperform the narrowband radars in the case of high detection probabilities; but the integration loss of the wideband radar energy integration detector is increased with the increasing of the wideband radar range resolution, and this factor causes that the detection predominance of the wideband radars to the narrowband radars is meaningless when the bandwidth of the radar is increased to a certain extent.
2010, 32(8): 1843-1848.
doi: 10.3724/SP.J.1146.2009.01133
Abstract:
A new algorithm to jointly estimate the DOD-DOA and Doppler frequency of bistatic MIMO radar is proposed based on the parallel factor. The receiver signal expression is derived under SweilingII target model, which shows it has three-way array model characteristics. Therefore, the uniqueness of the low-rank three-way array model decomposition is analysed. And the three parameters are jointly estimated from three matrices that are obtained from the low-rank decomposition. The new algorithm uses all of the received data and eliminates the error propagation of the several eigen decompositions because each iteration possesses a typical least square problem with a unique closed solution. Hence the estimation accuracy is increased. Furthermore, the estimated parameters are automatically paired without the additional pairing method, which the computational complexity of the proposed algorithm is reduced. Finally, simulation results are presented to verify the effectiveness of the proposed method.
A new algorithm to jointly estimate the DOD-DOA and Doppler frequency of bistatic MIMO radar is proposed based on the parallel factor. The receiver signal expression is derived under SweilingII target model, which shows it has three-way array model characteristics. Therefore, the uniqueness of the low-rank three-way array model decomposition is analysed. And the three parameters are jointly estimated from three matrices that are obtained from the low-rank decomposition. The new algorithm uses all of the received data and eliminates the error propagation of the several eigen decompositions because each iteration possesses a typical least square problem with a unique closed solution. Hence the estimation accuracy is increased. Furthermore, the estimated parameters are automatically paired without the additional pairing method, which the computational complexity of the proposed algorithm is reduced. Finally, simulation results are presented to verify the effectiveness of the proposed method.
2010, 32(8): 1849-1854.
doi: 10.3724/SP.J.1146.2009.01146
Abstract:
In order to process the multi-channel received data coherently in a convenient way, this paper simplifies MIMO (Multiple-Input Multiple-Output) radar signal model using phase center approximation, firstly. The multiple-transmit multiple-receive array architecture of MIMO radar is transformed into monostatic situation at the cost of causing displaced phase center error. Through the geometry of phase center approximation, definition of displaced phase center error is obtained. Displaced phase center error is analyzed in depth and some basic properties related to error correction are derived. Error correction expression of displaced phase center is designed according to the extent of space between receive and transmit phase center. Finally, the numerical experiments are provided to demonstrate the effectiveness of the theoretical analysis in this paper.
In order to process the multi-channel received data coherently in a convenient way, this paper simplifies MIMO (Multiple-Input Multiple-Output) radar signal model using phase center approximation, firstly. The multiple-transmit multiple-receive array architecture of MIMO radar is transformed into monostatic situation at the cost of causing displaced phase center error. Through the geometry of phase center approximation, definition of displaced phase center error is obtained. Displaced phase center error is analyzed in depth and some basic properties related to error correction are derived. Error correction expression of displaced phase center is designed according to the extent of space between receive and transmit phase center. Finally, the numerical experiments are provided to demonstrate the effectiveness of the theoretical analysis in this paper.
2010, 32(8): 1855-1862.
doi: 10.3724/SP.J.1146.2009.00706
Abstract:
This paper discusses mainly the image plane of the bistatic ISAR. The image plane is modeled by two different methods separately. One is modeling the image plane according to the bistatic SAR image plane; the other is to model the plane by target rotation vector analysis. The modeling process is presented in detail. They are then testified by applying them to interpret the bistatic turntable imaging. The simulation results show the validity of the second model. Based on the image plane analysis, the application condition of the turntable imaging model is analyzed. And the common used bistatic ISAR echo model is modified. Simulation results show the validity of the modified model. Finally, the image plane estimation method is also given according to different target motion situation.
This paper discusses mainly the image plane of the bistatic ISAR. The image plane is modeled by two different methods separately. One is modeling the image plane according to the bistatic SAR image plane; the other is to model the plane by target rotation vector analysis. The modeling process is presented in detail. They are then testified by applying them to interpret the bistatic turntable imaging. The simulation results show the validity of the second model. Based on the image plane analysis, the application condition of the turntable imaging model is analyzed. And the common used bistatic ISAR echo model is modified. Simulation results show the validity of the modified model. Finally, the image plane estimation method is also given according to different target motion situation.
2010, 32(8): 1863-1868.
doi: 10.3724/SP.J.1146.2009.01136
Abstract:
In this paper, the GEO spaceborne/airborne multistatic SAR geometry model with one fixed transmitter and multiple receivers is proposed, and the spectrum shift between different receiver echoes is derived. Based on the spectrum shift, a new algorithm for improving range resolution of this model by composing spectrums of different receivers is proposed. The overlapped interference term, which is induced during spectrum composing, and its influence on range resolution, is analyzed in detail, and a method by weight filtering is provided to remove the interference term. Finally, simulation is employed to test validity of the algorithm.
In this paper, the GEO spaceborne/airborne multistatic SAR geometry model with one fixed transmitter and multiple receivers is proposed, and the spectrum shift between different receiver echoes is derived. Based on the spectrum shift, a new algorithm for improving range resolution of this model by composing spectrums of different receivers is proposed. The overlapped interference term, which is induced during spectrum composing, and its influence on range resolution, is analyzed in detail, and a method by weight filtering is provided to remove the interference term. Finally, simulation is employed to test validity of the algorithm.
Three-dimensional Spatial-temporal Two-step Dimension-reduced Adaptive Processing for Airborne Radar
2010, 32(8): 1869-1873.
doi: 10.3724/SP.J.1146.2009.01248
Abstract:
Three-dimensional Space-Time Adaptive Processor (3D-STAP) is studied in this paper for airborne radar system, and a new kind of two-step dimension-reduced suboptimum STAP technique is proposed based on the frame of pre-Doppler followed by spatial adaptive processing (mDT-SAP). The Doppler filter with fixed configuration is performed on each spatially sampled element to reduce the correlation in the temporal domain, followed by spatial bi-iterative adaptive processing on the azimuth and elevation of the platform array based on the two separable weight vectors. It is shown that the proposed method has lower the computation load and needs smaller training data size compared to the traditional method. In additional, the effectiveness and robustness of the proposed method are demonstrated via numerical experiment.
Three-dimensional Space-Time Adaptive Processor (3D-STAP) is studied in this paper for airborne radar system, and a new kind of two-step dimension-reduced suboptimum STAP technique is proposed based on the frame of pre-Doppler followed by spatial adaptive processing (mDT-SAP). The Doppler filter with fixed configuration is performed on each spatially sampled element to reduce the correlation in the temporal domain, followed by spatial bi-iterative adaptive processing on the azimuth and elevation of the platform array based on the two separable weight vectors. It is shown that the proposed method has lower the computation load and needs smaller training data size compared to the traditional method. In additional, the effectiveness and robustness of the proposed method are demonstrated via numerical experiment.
2010, 32(8): 1874-1878.
doi: 10.3724/SP.J.1146.2009.00738
Abstract:
To solve the problem of height finding of dual-frequency radar, based on the phase interference theory, the height finding technique of dual-frequency radar is studied. Firstly, the basic principle of phase interference angle measurement is given in the paper, and the corresponding problem of phase blur in the use of dual-frequency radar height finding is analyzed in detail, then the resolving phase difference ambiguity method which is based on Chinese Remainder Theorem (CRT) is provided. Finally, the height finding precision is discussed. As a result, it is a feasible height finding technique of dual-frequency radar, of which the validity is also proved by the simulation of computer.
To solve the problem of height finding of dual-frequency radar, based on the phase interference theory, the height finding technique of dual-frequency radar is studied. Firstly, the basic principle of phase interference angle measurement is given in the paper, and the corresponding problem of phase blur in the use of dual-frequency radar height finding is analyzed in detail, then the resolving phase difference ambiguity method which is based on Chinese Remainder Theorem (CRT) is provided. Finally, the height finding precision is discussed. As a result, it is a feasible height finding technique of dual-frequency radar, of which the validity is also proved by the simulation of computer.
2010, 32(8): 1879-1884.
doi: 10.3724/SP.J.1146.2009.00745
Abstract:
Monitoring the weak ocean surface current is one of the most important applications for microwave remote sensing. It is significant for both civil and martial maritime activities. Signal Clutter Ratio (SCR) between ocean surface weak current and wind-generated waves is defined, in the frame of which the optimal configurations of RAR/SAR/biSAR with parallel flight squint mode are studied, under wind speed statistical distributions in South China Sea. The comparision results among the SCRs of the three sensor systems show that RAR, with the highest SCR, is the best system for weak ocean surface current observation.
Monitoring the weak ocean surface current is one of the most important applications for microwave remote sensing. It is significant for both civil and martial maritime activities. Signal Clutter Ratio (SCR) between ocean surface weak current and wind-generated waves is defined, in the frame of which the optimal configurations of RAR/SAR/biSAR with parallel flight squint mode are studied, under wind speed statistical distributions in South China Sea. The comparision results among the SCRs of the three sensor systems show that RAR, with the highest SCR, is the best system for weak ocean surface current observation.
Star Sensor Attitude Measuring Data Processing Technique in Condition of Complex Satellite Dithering
2010, 32(8): 1885-1891.
doi: 10.3724/SP.J.1146.2009.01079
Abstract:
Because dithering and vibrating exist inevitably while complex satellite running, this will lead to nonsteady and lower precision for star-sensor measurement data and difficult in data processing at low SNR. Therefore, in this paper, the data processing method in the condition of complex satellite dithering is discussed. Firstly, the measure principle and error mechanism of star sensor in satellite attitude determination are analyzed, and then on the basis of these analysis, the attitude measurement data processing technique in condition of satellite dithering is researched detailedly. Combined with the amplitude and frequency character of dithering signal, the influence of dithering to the measurement precision of star sensor is analyzed by using of searching the boundary point of amplitude and frequency for treating dithering error. In addition, integrating with the process of satellite attitude determination, the measurement data processing method of star sensor in the dithering condition is presented, which can effectively enhance the data precision for star sensor observation and make it possible to utilize dithering measurement data without steady state control. The method has the advantages of decreasing design cost and shortening design period.
Because dithering and vibrating exist inevitably while complex satellite running, this will lead to nonsteady and lower precision for star-sensor measurement data and difficult in data processing at low SNR. Therefore, in this paper, the data processing method in the condition of complex satellite dithering is discussed. Firstly, the measure principle and error mechanism of star sensor in satellite attitude determination are analyzed, and then on the basis of these analysis, the attitude measurement data processing technique in condition of satellite dithering is researched detailedly. Combined with the amplitude and frequency character of dithering signal, the influence of dithering to the measurement precision of star sensor is analyzed by using of searching the boundary point of amplitude and frequency for treating dithering error. In addition, integrating with the process of satellite attitude determination, the measurement data processing method of star sensor in the dithering condition is presented, which can effectively enhance the data precision for star sensor observation and make it possible to utilize dithering measurement data without steady state control. The method has the advantages of decreasing design cost and shortening design period.
2010, 32(8): 1892-1897.
doi: 10.3724/SP.J.1146.2009.01048
Abstract:
Link disruption and connection have a considerable impact on satellite networks routing issues. A link disruption tolerant routing strategy is proposed for multilayered satellite networks. In this strategy, the route table is calculated by means of the topology predictability of satellite networks in nonuniform slots to resolve the routing problems under link disruption circumstances caused by satellite movements, and a dynamic congestion control mechanism and a flood strategy are suggested to ensure the packets correct forwarding during system failure period. The simulation results show that this strategy has higher link utilization and less time-space cost of dynamic route calculation, including delay information collection and route table generation.
Link disruption and connection have a considerable impact on satellite networks routing issues. A link disruption tolerant routing strategy is proposed for multilayered satellite networks. In this strategy, the route table is calculated by means of the topology predictability of satellite networks in nonuniform slots to resolve the routing problems under link disruption circumstances caused by satellite movements, and a dynamic congestion control mechanism and a flood strategy are suggested to ensure the packets correct forwarding during system failure period. The simulation results show that this strategy has higher link utilization and less time-space cost of dynamic route calculation, including delay information collection and route table generation.
2010, 32(8): 1898-1903.
doi: 10.3724/SP.J.1146.2009.01105
Abstract:
A concatenated scheme of Luby Transform (LT) code and q-ary Low Density Parity Check (q-LDPC) code is proposed for the requirement of deep space communications long erasure correcting codes. Considering the performance and complexity of the concatenated system, 8PSK modulation coded with 8-LDPC codes over AWGN channels is chosen to act as equivalent erasure channels and LT codes with flexible code length and low encoding and decoding complexity correct erasure errors. Two short 8-LDPC codes are designed. Simulations are conducted on the performance of packet error of two 8-LDPC codes and the overall performance of the concatenated system. Simulation results show that both the 8-LDPC codes outperform the corresponding binary LDPC (B-LDPC) codes with the same source rate and code rate and the bit error rate of the concatenated system is null with probability 1 when the packet erasure rate is not more than 0.1.
A concatenated scheme of Luby Transform (LT) code and q-ary Low Density Parity Check (q-LDPC) code is proposed for the requirement of deep space communications long erasure correcting codes. Considering the performance and complexity of the concatenated system, 8PSK modulation coded with 8-LDPC codes over AWGN channels is chosen to act as equivalent erasure channels and LT codes with flexible code length and low encoding and decoding complexity correct erasure errors. Two short 8-LDPC codes are designed. Simulations are conducted on the performance of packet error of two 8-LDPC codes and the overall performance of the concatenated system. Simulation results show that both the 8-LDPC codes outperform the corresponding binary LDPC (B-LDPC) codes with the same source rate and code rate and the bit error rate of the concatenated system is null with probability 1 when the packet erasure rate is not more than 0.1.
2010, 32(8): 1904-1909.
doi: 10.3724/SP.J.1146.2009.00464
Abstract:
In order to satisfy the requirement of aerocrafts multi- transmission for further development, this paper leads to a resolution about on-board SpaceWire routing technology. Based on the network level analysis of SpaceWire standard, it built the architecture of router with wormhole routing theory and non-blocking switch mechanism. A simulation model of router had been set to verify the design, and braking-problem from wormhole routing-blocking had been solved with BWR (Buffered Wormhole Routing), it reduces 70% average packet-losing ratio on full load communication.
In order to satisfy the requirement of aerocrafts multi- transmission for further development, this paper leads to a resolution about on-board SpaceWire routing technology. Based on the network level analysis of SpaceWire standard, it built the architecture of router with wormhole routing theory and non-blocking switch mechanism. A simulation model of router had been set to verify the design, and braking-problem from wormhole routing-blocking had been solved with BWR (Buffered Wormhole Routing), it reduces 70% average packet-losing ratio on full load communication.
2010, 32(8): 1910-1913.
doi: 10.3724/SP.J.1146.2009.01188
Abstract:
In this paper, a sub-optimal transmission technique is proposed for uplink MU-MIMO systems, which is called Maximum Eigenmode BeamForming (MEBF). Compared with the optimal transmission technique (i.e., Multi-User Iterative Water-Filling, MU-IWF), the complexity of MEBF is very low since each User Equipment (UE) transmits only in its maximum eigenmode direction. Theoretical analyses show that MEBF is asymptotically optimal with the number of UEs increasing. It is also shown by simulation results that for a finite number of UEs, MEBF is nearly optimal.
In this paper, a sub-optimal transmission technique is proposed for uplink MU-MIMO systems, which is called Maximum Eigenmode BeamForming (MEBF). Compared with the optimal transmission technique (i.e., Multi-User Iterative Water-Filling, MU-IWF), the complexity of MEBF is very low since each User Equipment (UE) transmits only in its maximum eigenmode direction. Theoretical analyses show that MEBF is asymptotically optimal with the number of UEs increasing. It is also shown by simulation results that for a finite number of UEs, MEBF is nearly optimal.
2010, 32(8): 1914-1919.
doi: 10.3724/SP.J.1146.2009.01182
Abstract:
A segmented maximum likelihood iterative detection algorithm is proposed for distributed space- frequency coded cooperative communication system with multiple relay nodes over frequency-selective fading channels. The destination node divides each distributed space-frequency coding vector into several sub-segment evenly in frequency domain, and performs maximum likelihood detection on them respectively. Theoretical analysis and simulation results confirm the fast convergence speed, the low complexity and the high practicality of the proposed iterative detection algorithm.
A segmented maximum likelihood iterative detection algorithm is proposed for distributed space- frequency coded cooperative communication system with multiple relay nodes over frequency-selective fading channels. The destination node divides each distributed space-frequency coding vector into several sub-segment evenly in frequency domain, and performs maximum likelihood detection on them respectively. Theoretical analysis and simulation results confirm the fast convergence speed, the low complexity and the high practicality of the proposed iterative detection algorithm.
2010, 32(8): 1920-1925.
doi: 10.3724/SP.J.1146.2009.01316
Abstract:
In this article, a relay selection and power allocation strategy based on buyer-seller game is proposed for Decode-and-Forward (DF) cooperative relay network. The user is modeled as a buyer which selects the optimal relay and determines the optimal amount of power bought from the relay based on the maximum utility criterion. The relay is modeled as a seller which determines the price of the power using market-first-profit-second strategy to achieve the maximum profit. The equilibrium conditions of the game between the two sides are analyzed. The simulation results verify the existence of the Nash equilibrium point and illustrate the small amount of calculation, the fast convergence and the practicability of the strategy. The results also illustrate that using the strategy may increase the transmission rate of the user, the coverage of the base station and improve the power efficiency taking into account the interests of the user and the relay nodes.
In this article, a relay selection and power allocation strategy based on buyer-seller game is proposed for Decode-and-Forward (DF) cooperative relay network. The user is modeled as a buyer which selects the optimal relay and determines the optimal amount of power bought from the relay based on the maximum utility criterion. The relay is modeled as a seller which determines the price of the power using market-first-profit-second strategy to achieve the maximum profit. The equilibrium conditions of the game between the two sides are analyzed. The simulation results verify the existence of the Nash equilibrium point and illustrate the small amount of calculation, the fast convergence and the practicability of the strategy. The results also illustrate that using the strategy may increase the transmission rate of the user, the coverage of the base station and improve the power efficiency taking into account the interests of the user and the relay nodes.
2010, 32(8): 1926-1931.
doi: 10.3724/SP.J.1146.2009.01089
Abstract:
考虑一对多天线的信源信宿通过一个单天线的放大前传(AF)中继辅助通信的两跳半双工无线网络。假设通信终端完全获知信道状态信息(CSI)。该文提出了该中继系统的最优波束成型方案，然后对采用此方案时的系统接收信噪比作高SNR下的统计特性分析，推导出瑞利平衰落信道下系统的遍历容量上界和平均误符号率(ASEP)的闭合表达式，并得出相应的分集度和阵列增益。理论分析结果显示了系统性能与天线数和发射功率的确切关系，并且在高SNR时不同的调制方式不影响分集度，只改变阵列增益。蒙特卡罗(Monte Carlo)数值仿真结果验证了理论分析的正确性。
考虑一对多天线的信源信宿通过一个单天线的放大前传(AF)中继辅助通信的两跳半双工无线网络。假设通信终端完全获知信道状态信息(CSI)。该文提出了该中继系统的最优波束成型方案，然后对采用此方案时的系统接收信噪比作高SNR下的统计特性分析，推导出瑞利平衰落信道下系统的遍历容量上界和平均误符号率(ASEP)的闭合表达式，并得出相应的分集度和阵列增益。理论分析结果显示了系统性能与天线数和发射功率的确切关系，并且在高SNR时不同的调制方式不影响分集度，只改变阵列增益。蒙特卡罗(Monte Carlo)数值仿真结果验证了理论分析的正确性。
2010, 32(8): 1932-1937.
doi: 10.3724/SP.J.1146.2009.00728
Abstract:
This paper studies the network throughput capacity gain of Physical-layer Network Coding (PNC) in data-gathering wireless ad hoc networks. The throughput upper bound and lower bound with the PNC scheme are derived by utilizing the sparsity-cut capacity analysis. The result of this paper implies that by using PNC, an order capacity gain can be obtained over traditional routing and network coding schemes in wireless data-gathering Ad hoc networks.
This paper studies the network throughput capacity gain of Physical-layer Network Coding (PNC) in data-gathering wireless ad hoc networks. The throughput upper bound and lower bound with the PNC scheme are derived by utilizing the sparsity-cut capacity analysis. The result of this paper implies that by using PNC, an order capacity gain can be obtained over traditional routing and network coding schemes in wireless data-gathering Ad hoc networks.
2010, 32(8): 1938-1942.
doi: 10.3724/SP.J.1146.2009.00814
Abstract:
In order to determine the sending time for the mobile station, a novel synchronous control mechanism for the uplink in the LTE TDD system is proposed in this paper. Firstly, the principle of synchronous control is introduced. Secondly, according to the information used to estimate the channel status, the initial, peak and end position of impulse response is detected reasonably; Moreover, the method for controlling the synchronous of uplink is proposed. Results show the effectiveness of the mechanism under scenarios with different velocity and the degree of signal to noise, additionally, the ISI induced by the inaccurate timing can be avoided.
In order to determine the sending time for the mobile station, a novel synchronous control mechanism for the uplink in the LTE TDD system is proposed in this paper. Firstly, the principle of synchronous control is introduced. Secondly, according to the information used to estimate the channel status, the initial, peak and end position of impulse response is detected reasonably; Moreover, the method for controlling the synchronous of uplink is proposed. Results show the effectiveness of the mechanism under scenarios with different velocity and the degree of signal to noise, additionally, the ISI induced by the inaccurate timing can be avoided.
2010, 32(8): 1943-1947.
doi: 10.3724/SP.J.1146.2009.00665
Abstract:
The spread-spectrum system usually works in the multipath environment, along with the additive noise there always be some multiplicative noise. In order to solve the Pseudo-Noise (PN) code acquisition in multiplicative noise channel, a new detector using signed-rank-based nonparametric detector is proposed in this paper. Modeling the acquisition problem as a hypothesis testing problem, a detector is derived for multiplicative noise, based on signed-rank statistics using the locally optimum detection technique. Then the Locally Suboptimum Rank (LSR) detector is proposed by using approximate score functions. Numerical results show that the LSR detector can offer substantial performance improvement over the conventional squared-sum detector in multiplicative noise channels and asymptotically has almost the same performance as the locally optimum detector in multiplicative noise.
The spread-spectrum system usually works in the multipath environment, along with the additive noise there always be some multiplicative noise. In order to solve the Pseudo-Noise (PN) code acquisition in multiplicative noise channel, a new detector using signed-rank-based nonparametric detector is proposed in this paper. Modeling the acquisition problem as a hypothesis testing problem, a detector is derived for multiplicative noise, based on signed-rank statistics using the locally optimum detection technique. Then the Locally Suboptimum Rank (LSR) detector is proposed by using approximate score functions. Numerical results show that the LSR detector can offer substantial performance improvement over the conventional squared-sum detector in multiplicative noise channels and asymptotically has almost the same performance as the locally optimum detector in multiplicative noise.
2010, 32(8): 1948-1952.
doi: 10.3724/SP.J.1146.2009.00824
Abstract:
Many existing three Party Password-Authenticated Key Exchange (3PAKE) protocols are found insecure. An ideal functionality of 3PAKE is defined in the universal composability model，and a 3PAKE protocol is constructed to realize the 3PAKE ideal functionality in the hybrid model which aided by two party password-authenticated key exchange ideal functionality. The new protocol comprises of three phases: intermediate key generation, message authentication transmission and session key generation. The protocol is UC-secure, and has simpler structure.
Many existing three Party Password-Authenticated Key Exchange (3PAKE) protocols are found insecure. An ideal functionality of 3PAKE is defined in the universal composability model，and a 3PAKE protocol is constructed to realize the 3PAKE ideal functionality in the hybrid model which aided by two party password-authenticated key exchange ideal functionality. The new protocol comprises of three phases: intermediate key generation, message authentication transmission and session key generation. The protocol is UC-secure, and has simpler structure.
2010, 32(8): 1953-1955.
doi: 10.3724/SP.J.1146.2009.01313
Abstract:
This paper constructs a diamond structure multicollision with2k initial values and variant lengths, which is used to propose a new chosen target forced prefix preimage attack (herding attack) on hash functions with Strengthening Merkle-Damagard (SMD) construction to find a preimage with 2k+3 blocks. Since the number of the chaining values available in herding attack is increased, the computational complexity of herding attack is reduced toO(2n-k/3+2n/2+k+2) fromO(2n-2(k+1)+2n/2+k+5/2) for kn/4-1.05.
This paper constructs a diamond structure multicollision with2k initial values and variant lengths, which is used to propose a new chosen target forced prefix preimage attack (herding attack) on hash functions with Strengthening Merkle-Damagard (SMD) construction to find a preimage with 2k+3 blocks. Since the number of the chaining values available in herding attack is increased, the computational complexity of herding attack is reduced toO(2n-k/3+2n/2+k+2) fromO(2n-2(k+1)+2n/2+k+5/2) for kn/4-1.05.
2010, 32(8): 1956-1960.
doi: 10.3724/SP.J.1146.2009.01160
Abstract:
As layered algorithm can not be used in the decoding of the non-layered LDPC codes, a Parallel- Layered Belief-Propagation (PLBP) algorithm is proposed in this paper. The decoding of this algorithm is quite different from the original layered algorithm, for it uses parallel updating among all layers and serial updating within each layer. With such a decoding schedule, a variable node in different layers is updated at different time, which means the message is able to be updated layer by layer for each variable node. The simulation shows the PLBP algorithm not only achieves a better error performance, but also requires almost 50% less iterations than the Flooding algorithm with the same complexity. Additionally, a merged computation of the nodes is employed by the PLBP algorithm. As a result, the decoding speed of the PLBP algorithm can reach nearly 4 times as that of the original Flooding algorithm.
As layered algorithm can not be used in the decoding of the non-layered LDPC codes, a Parallel- Layered Belief-Propagation (PLBP) algorithm is proposed in this paper. The decoding of this algorithm is quite different from the original layered algorithm, for it uses parallel updating among all layers and serial updating within each layer. With such a decoding schedule, a variable node in different layers is updated at different time, which means the message is able to be updated layer by layer for each variable node. The simulation shows the PLBP algorithm not only achieves a better error performance, but also requires almost 50% less iterations than the Flooding algorithm with the same complexity. Additionally, a merged computation of the nodes is employed by the PLBP algorithm. As a result, the decoding speed of the PLBP algorithm can reach nearly 4 times as that of the original Flooding algorithm.
2010, 32(8): 1961-1967.
doi: 10.3724/SP.J.1146.2009.01038
Abstract:
Secure Wireless Roaming (SWR) allows a roaming user under the subscription of its home server to establish a secure session key with a foreign server in an authenticated way such that both the foreign server and the roaming user can mutually authenticate each other. Anonymous SWR provides an additional service to the roaming user so that the roaming user can keep anonymous and untraceable even if all the visited foreign servers are colluding with each other. In this paper, an anonymous SWR called SYM-SWR (SYMmetric key based SWR) is proposed. To best of our knowledge, it seems to be the first pure symmetric key based anonymous SWR. Compared with other existing SWR protocols both of the computation complexity and communication complexity of SYM-SWR are lowest, since it involves only 4 message flows and no PKI (Public Key Infrastructure) but only highly efficient cryptographic operations are needed which include Message Authentication Code (MAC) and symmetric key encryption.
Secure Wireless Roaming (SWR) allows a roaming user under the subscription of its home server to establish a secure session key with a foreign server in an authenticated way such that both the foreign server and the roaming user can mutually authenticate each other. Anonymous SWR provides an additional service to the roaming user so that the roaming user can keep anonymous and untraceable even if all the visited foreign servers are colluding with each other. In this paper, an anonymous SWR called SYM-SWR (SYMmetric key based SWR) is proposed. To best of our knowledge, it seems to be the first pure symmetric key based anonymous SWR. Compared with other existing SWR protocols both of the computation complexity and communication complexity of SYM-SWR are lowest, since it involves only 4 message flows and no PKI (Public Key Infrastructure) but only highly efficient cryptographic operations are needed which include Message Authentication Code (MAC) and symmetric key encryption.
2010, 32(8): 1968-1973.
doi: 10.3724/SP.J.1146.2009.00725
Abstract:
In order to estimate energy overhead of sensor nodes, it is necessary to model their power consumption reasonably and accurately. However, existing power models are not accurate enough. This paper proposes a novel power model based on power state machines with continuous parameters, which can be used for any type of sensor nodes. This model is able to predict power consumption of sensor nodes according to changes of supply voltage and operating frequency. By handling ATmega128 (L) microprocessor frequently used in typical sensor nodes with this model and comparing with independent measurement results, it is shown that prediction error of this model is less than 1% for active state and 9.7% for idle state. This model can be used to substitute existing models of sensor network simulators to provide more accurate prediction results of energy overhead for sensor nodes.
In order to estimate energy overhead of sensor nodes, it is necessary to model their power consumption reasonably and accurately. However, existing power models are not accurate enough. This paper proposes a novel power model based on power state machines with continuous parameters, which can be used for any type of sensor nodes. This model is able to predict power consumption of sensor nodes according to changes of supply voltage and operating frequency. By handling ATmega128 (L) microprocessor frequently used in typical sensor nodes with this model and comparing with independent measurement results, it is shown that prediction error of this model is less than 1% for active state and 9.7% for idle state. This model can be used to substitute existing models of sensor network simulators to provide more accurate prediction results of energy overhead for sensor nodes.
2010, 32(8): 1974-1979.
doi: 10.3724/SP.J.1146.2009.01147
Abstract:
Focusing on the energy consumption and the network delay in wireless sensor network applied to emergent event monitoring, a new Data Gathering algorithm based on Mobile Agent (DGMA) is proposed for the chain-based wireless sensor network. The process of dynamically clustering the sensor nodes is based on the event severity, by which the scale and lifetime of clusters are determined. And a virtual cluster is formed between sink and cluster heads regarded sink node as its cluster head. The next hop in route planning for mobile agents is determined by the residual energy, the path loss and the stimulus intensity. The mobile agents equipped on cluster heads can gather information by traversing all member nodes. The theory analysis and simulation results show that mobile agent model has a better performance in energy consumption and network delay compared to C/S model. Furthermore, DGMA will provide a more appropriate performance for wireless sensor network applied to a large scale emergent event monitoring.
Focusing on the energy consumption and the network delay in wireless sensor network applied to emergent event monitoring, a new Data Gathering algorithm based on Mobile Agent (DGMA) is proposed for the chain-based wireless sensor network. The process of dynamically clustering the sensor nodes is based on the event severity, by which the scale and lifetime of clusters are determined. And a virtual cluster is formed between sink and cluster heads regarded sink node as its cluster head. The next hop in route planning for mobile agents is determined by the residual energy, the path loss and the stimulus intensity. The mobile agents equipped on cluster heads can gather information by traversing all member nodes. The theory analysis and simulation results show that mobile agent model has a better performance in energy consumption and network delay compared to C/S model. Furthermore, DGMA will provide a more appropriate performance for wireless sensor network applied to a large scale emergent event monitoring.
2010, 32(8): 1980-1985.
doi: 10.3724/SP.J.1146.2009.01608
Abstract:
As a result of the research and design of Reconfiguration Router Unit (RRU), the producing of network equipment is turned into component composition as building block. Based on the component composition,the character of RRU, and situation that the third-party manufacturers provide components for a large number of the component library led to the rapid expansion of the difficulties of the urgent need to provide components,this paper proposes the CCS (Component Candidate Set). Based on the difference between the static load and dynamic load, the scheme of creating component candidate set is based on the neural network. The CSS is proposed to resolve the problem of automation and dynamic in the process of RRU component composition. According to the CCS, this paper describes the running state of component, self-determination running and adaptive evolution operation. Simulation experiment shows that this CCS-based method is precious and effective. The method that be successfully used in the reconfiguration router unit proves that the method is practical.
As a result of the research and design of Reconfiguration Router Unit (RRU), the producing of network equipment is turned into component composition as building block. Based on the component composition,the character of RRU, and situation that the third-party manufacturers provide components for a large number of the component library led to the rapid expansion of the difficulties of the urgent need to provide components,this paper proposes the CCS (Component Candidate Set). Based on the difference between the static load and dynamic load, the scheme of creating component candidate set is based on the neural network. The CSS is proposed to resolve the problem of automation and dynamic in the process of RRU component composition. According to the CCS, this paper describes the running state of component, self-determination running and adaptive evolution operation. Simulation experiment shows that this CCS-based method is precious and effective. The method that be successfully used in the reconfiguration router unit proves that the method is practical.
2010, 32(8): 1986-1991.
doi: 10.3724/SP.J.1146.2009.00953
Abstract:
This paper devotes to modeling and the stability study of a Ka-band TE01 mode gyrotron Traveling-Wave Tube (gyro-TWT) based on a modal selective circuit alternately loaded with lossy ceramic shells and metal rings. The linear theory and the self-consistent nonlinear theory are applied to analyze the stability of the equivalent interaction circuit. The study reveals that the lossy dielectric-loaded waveguide is with modal selective ability, and its propagation characteristics are similar to that of the circular empty waveguide. The internal feedback physics of the self-excited oscillations are revealed in the stability analysis. The consistency between the theoretical analysis and the experimental tests of American Naval Research Laboratory indicates the reliability of this study. The theoretical model in this paper brings guidance for future designing a gyro-TWT.
This paper devotes to modeling and the stability study of a Ka-band TE01 mode gyrotron Traveling-Wave Tube (gyro-TWT) based on a modal selective circuit alternately loaded with lossy ceramic shells and metal rings. The linear theory and the self-consistent nonlinear theory are applied to analyze the stability of the equivalent interaction circuit. The study reveals that the lossy dielectric-loaded waveguide is with modal selective ability, and its propagation characteristics are similar to that of the circular empty waveguide. The internal feedback physics of the self-excited oscillations are revealed in the stability analysis. The consistency between the theoretical analysis and the experimental tests of American Naval Research Laboratory indicates the reliability of this study. The theoretical model in this paper brings guidance for future designing a gyro-TWT.
2010, 32(8): 1992-1996.
doi: 10.3724/SP.J.1146.2009.00796
Abstract:
The space-frequency processing of sub-apertures that obtained from the single-antenna airborne SAR is proposed for the moving target detection. First the process of how to gain the sub-apertures is presented through the azimuth frequency processing. The sub-apertures that resemble the multi-channel are formed. Then the equivalent property for the space-time signal of the sub-apertures is particular analyzed. The echo signals of the sub-apertures gained in different synthesized center times are equal to the echo signals obtained from the same time and the different space positions. The time delay of the sub-aperture is used to gain the space information and the two-dimension signal model of the sub-apertures is established. Learned from the method of using multi-channels to suppress the clutter, the space-frequency adaptive processing of the sub-apertures is presented to realize the moving target detection and the clutter suppression. Finally, the simulation results demonstrate that the method is effective.
The space-frequency processing of sub-apertures that obtained from the single-antenna airborne SAR is proposed for the moving target detection. First the process of how to gain the sub-apertures is presented through the azimuth frequency processing. The sub-apertures that resemble the multi-channel are formed. Then the equivalent property for the space-time signal of the sub-apertures is particular analyzed. The echo signals of the sub-apertures gained in different synthesized center times are equal to the echo signals obtained from the same time and the different space positions. The time delay of the sub-aperture is used to gain the space information and the two-dimension signal model of the sub-apertures is established. Learned from the method of using multi-channels to suppress the clutter, the space-frequency adaptive processing of the sub-apertures is presented to realize the moving target detection and the clutter suppression. Finally, the simulation results demonstrate that the method is effective.
2010, 32(8): 1997-2001.
doi: 10.3724/SP.J.1146.2009.00937
Abstract:
Multi-input multi-output spaceborne SAR transmits orthogonal coding signals with multiple antennas from different transmitting phase centers, and receives returns from different receiving phase centers to form multi-channel signals. It can increase the spatial freedom considerably, which gives advantages to detecting ground moving targets. This paper researches the ground moving targets detection technologies for multi-input multi-output spaceborne SAR with space-time adaptive signal processing. Considering the characteristics of the returns of the spaceborne SAR, in the basis of research on the space-frequency adaptive processing algorithm, the text adapts eigen-structure based space-frequency adaptive processing algorithm to suppress the clutter and completes finally the detection of the moving targets. Simulation results proves the validity of proposed algorithm.
Multi-input multi-output spaceborne SAR transmits orthogonal coding signals with multiple antennas from different transmitting phase centers, and receives returns from different receiving phase centers to form multi-channel signals. It can increase the spatial freedom considerably, which gives advantages to detecting ground moving targets. This paper researches the ground moving targets detection technologies for multi-input multi-output spaceborne SAR with space-time adaptive signal processing. Considering the characteristics of the returns of the spaceborne SAR, in the basis of research on the space-frequency adaptive processing algorithm, the text adapts eigen-structure based space-frequency adaptive processing algorithm to suppress the clutter and completes finally the detection of the moving targets. Simulation results proves the validity of proposed algorithm.
2010, 32(8): 2002-2005.
doi: 10.3724/SP.J.1146.2009.01535
Abstract:
Schumann Resonance (SR) is closely related with atmospheric temperature changes and electromagnetic precursors of earthquakes. In this paper, a new method to monitor SR is proposed as the heavy environment constraints in the ground-based observing. That is to transmit High Frequency (HF) electromagnetic waves into the ionosphere, where the HF signals will be cross-modulated with SR. So it can be obtained by de-modulating the HF waves. The feasibility of the experiment is verified based on the nonlinear modulation model of HF waves and SR in the lower ionosphere，in which the fair weather electric filed is taken into account. The first 4 peaks of Schumann resonance respectively at 7 Hz, 14 Hz, 20 Hz, 26 Hz are obtained in demodulation spectra of short wave timing signal BPM at the first Schumann Resonance observatory of China. The theoretical and experimental results show that it is feasible to get SR signals in the lower ionosphere from the HF demodulation spectra.
Schumann Resonance (SR) is closely related with atmospheric temperature changes and electromagnetic precursors of earthquakes. In this paper, a new method to monitor SR is proposed as the heavy environment constraints in the ground-based observing. That is to transmit High Frequency (HF) electromagnetic waves into the ionosphere, where the HF signals will be cross-modulated with SR. So it can be obtained by de-modulating the HF waves. The feasibility of the experiment is verified based on the nonlinear modulation model of HF waves and SR in the lower ionosphere，in which the fair weather electric filed is taken into account. The first 4 peaks of Schumann resonance respectively at 7 Hz, 14 Hz, 20 Hz, 26 Hz are obtained in demodulation spectra of short wave timing signal BPM at the first Schumann Resonance observatory of China. The theoretical and experimental results show that it is feasible to get SR signals in the lower ionosphere from the HF demodulation spectra.
2010, 32(8): 2006-2009.
doi: 10.3724/SP.J.1146.2009.01072
Abstract:
To improve the precision of Speaker Segmentation (SS), this paper propose a two-step SS algorithm by making use of silence and gender information. Two-step criterion is used to decide the Speaker Change Point (SCP) within detected speech segmentations. In the first step, pitch difference between different speakers and gender model are used to locate the SCP within neighboring speech segments; In the second step, a gender-based modified T2 criterion formula is used to locate SCP among the same gender speakers, and potential speaker change point is detected based on chunk. The experiment results show that the proposed algorithm improved SS precision and F1 can reach 85.14%. For SS with duration less than 2 s, the algorithm can reduce missed detection rate of about 16%, compared with Bayesian information Criterion.
To improve the precision of Speaker Segmentation (SS), this paper propose a two-step SS algorithm by making use of silence and gender information. Two-step criterion is used to decide the Speaker Change Point (SCP) within detected speech segmentations. In the first step, pitch difference between different speakers and gender model are used to locate the SCP within neighboring speech segments; In the second step, a gender-based modified T2 criterion formula is used to locate SCP among the same gender speakers, and potential speaker change point is detected based on chunk. The experiment results show that the proposed algorithm improved SS precision and F1 can reach 85.14%. For SS with duration less than 2 s, the algorithm can reduce missed detection rate of about 16%, compared with Bayesian information Criterion.
2010, 32(8): 2010-2014.
doi: 10.3724/SP.J.1146.2009.00828
Abstract:
A space-time and multi-path diversity combining algorithm is presented in STBC block transmission system with two transmit antennas and one receive antenna. The primary detection is carried out by STBC-based Single Carrier Frequency Domain Equalizer (STBC-SC-FDE), then the multi-path components in the received signal are separated by the initial solution and channel state information. After all the multi-path components are processed by the STBC combining algorithm, the output branches are combined together using Maximal Ratio Combining (MRC) algorithm in the space-time two dimensional RAKE receiver. The new scheme can achieve transmit and multi-path diversity under low computational complexity, and the performance is evaluated by Monte Carlo simulations.
A space-time and multi-path diversity combining algorithm is presented in STBC block transmission system with two transmit antennas and one receive antenna. The primary detection is carried out by STBC-based Single Carrier Frequency Domain Equalizer (STBC-SC-FDE), then the multi-path components in the received signal are separated by the initial solution and channel state information. After all the multi-path components are processed by the STBC combining algorithm, the output branches are combined together using Maximal Ratio Combining (MRC) algorithm in the space-time two dimensional RAKE receiver. The new scheme can achieve transmit and multi-path diversity under low computational complexity, and the performance is evaluated by Monte Carlo simulations.
2010, 32(8): 2015-2018.
doi: 10.3724/SP.J.1146.2009.01071
Abstract:
The diffusion property of image encryption algorithms in block-and-permutation mode is investigated, where two new conceptions, the optimal diffusion and collision-free permutation are put forward. An image encryption algorithm in block-and-permutation mode fulfills the requirement of optimal diffusion when the global diffusion is achieved within the ideally least round, which is feasible if and only if the permutation is collision-free. Further more, a permutation algorithm based on quadtree structure is proposed, which is proved to fulfill the requirement of the optimal diffusein.
The diffusion property of image encryption algorithms in block-and-permutation mode is investigated, where two new conceptions, the optimal diffusion and collision-free permutation are put forward. An image encryption algorithm in block-and-permutation mode fulfills the requirement of optimal diffusion when the global diffusion is achieved within the ideally least round, which is feasible if and only if the permutation is collision-free. Further more, a permutation algorithm based on quadtree structure is proposed, which is proved to fulfill the requirement of the optimal diffusein.
2010, 32(8): 2019-2022.
doi: 10.3724/SP.J.1146.2009.01401
Abstract:
The fast matrix solving is the key of the moment method when computing the electrically large issues. LU decomposition is a efficient algorithm for solving linear equations. In this paper, Doolittle LU Decomposition is described detailedly. Based on the decomposition characteristics, a parallel solving method looping over squares is proposed in MPI (Message-Passing interface) parallel environment. The experiments indicate that the method can decrease communication quantity between processes and accelerate computing speed efficiently.
The fast matrix solving is the key of the moment method when computing the electrically large issues. LU decomposition is a efficient algorithm for solving linear equations. In this paper, Doolittle LU Decomposition is described detailedly. Based on the decomposition characteristics, a parallel solving method looping over squares is proposed in MPI (Message-Passing interface) parallel environment. The experiments indicate that the method can decrease communication quantity between processes and accelerate computing speed efficiently.
2010, 32(8): 2023-2027.
doi: 10.3724/SP.J.1146.2009.01007
Abstract:
Single-driver directional wires and multi-driver directional wires can both be used for FPGA interconnect. This paper compares them in area, performance, and their effect on topology of the routing architecture. Then a new type of FPGA routing architecture is proposed that utilizes a mixture of single-driver and multi-driver wires combined with various wire lengths and a two-stage optimization method is used to obtain the best routing architecture. Extensive experiments show that the best architecture optimized by area-delay product is 50% length 6 wires with single-driver, 25% length 8 wires with multi-driver and 25% length 8 wires with single-driver. This results in FPGA with 57%～86% gain in area-delay product.
Single-driver directional wires and multi-driver directional wires can both be used for FPGA interconnect. This paper compares them in area, performance, and their effect on topology of the routing architecture. Then a new type of FPGA routing architecture is proposed that utilizes a mixture of single-driver and multi-driver wires combined with various wire lengths and a two-stage optimization method is used to obtain the best routing architecture. Extensive experiments show that the best architecture optimized by area-delay product is 50% length 6 wires with single-driver, 25% length 8 wires with multi-driver and 25% length 8 wires with single-driver. This results in FPGA with 57%～86% gain in area-delay product.
2010, 32(8): 2028-2032.
doi: 10.3724/SP.J.1146.2009.01016
Abstract:
A monolithic SiGe Heterojunction Bipolar Transistor (HBT) Low Noise Amplifier (LNA) is designed and fabricated in this paper. Composite resistance feedback loops are adopted in this amplifier. Hence, reasonable bias conditions, good port matching and low Noise Figure (NF) are achieved simultaneously by adjusting different feedback resistor smartly. Based on the 0.35-m Si CMOS technology, the fabrication processes for monolithic amplifier integrated chip are developed. In the fabrication process of SiGe devices, base resistance of transistor is reduced by using titanium silicon (TiSi2) deposition in order to further decrease the NF of LNA. Finally, die area of this monolithic LNA is only 0.282 mm2 due to the absence of spiral inductor which occupies most of chip area. The measurement results indicate that, in the band from 0.2 to1.2 GHz, this LNA achieves the minimum NF of 2.5 dB, the maximum gain as high as 26.7 dB, and the input and output reflections (S11, S22) of less than -7.4 dB and -10 dB, respectively.
A monolithic SiGe Heterojunction Bipolar Transistor (HBT) Low Noise Amplifier (LNA) is designed and fabricated in this paper. Composite resistance feedback loops are adopted in this amplifier. Hence, reasonable bias conditions, good port matching and low Noise Figure (NF) are achieved simultaneously by adjusting different feedback resistor smartly. Based on the 0.35-m Si CMOS technology, the fabrication processes for monolithic amplifier integrated chip are developed. In the fabrication process of SiGe devices, base resistance of transistor is reduced by using titanium silicon (TiSi2) deposition in order to further decrease the NF of LNA. Finally, die area of this monolithic LNA is only 0.282 mm2 due to the absence of spiral inductor which occupies most of chip area. The measurement results indicate that, in the band from 0.2 to1.2 GHz, this LNA achieves the minimum NF of 2.5 dB, the maximum gain as high as 26.7 dB, and the input and output reflections (S11, S22) of less than -7.4 dB and -10 dB, respectively.
