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2005 Vol. 27, No. 9
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2005, 27(9): 1345-1348.
Abstract:
To analyze several key problems about effectiveness analysis of spaceborne parasitic SAR system，firstly,an index system ofefectiveness assessment is established based on the m ission request ofdistributed SAR system；combined with orbit characteristics of distributed small satellites，the model of system capability is established；based on system working state，Markov model of system reliability is established；based on capability model and reliability model，the model of effectiveness assessment is established．The simulation results indicate the proposed models provide theoretic dependence for effectiveness analysis of spaceborne parasitic distributed SAR system.
To analyze several key problems about effectiveness analysis of spaceborne parasitic SAR system，firstly,an index system ofefectiveness assessment is established based on the m ission request ofdistributed SAR system；combined with orbit characteristics of distributed small satellites，the model of system capability is established；based on system working state，Markov model of system reliability is established；based on capability model and reliability model，the model of effectiveness assessment is established．The simulation results indicate the proposed models provide theoretic dependence for effectiveness analysis of spaceborne parasitic distributed SAR system.
2005, 27(9): 1349-1352.
Abstract:
Phase Gradient Algorithm （PGA） is accomodated to focus the StripMap SAR data in this article. A new approach to StripMap SAR autofocus, StripMap PGA（SPGA）, is developed based on the difference between the received signal of StripMap SAR and SpotLight SAR and the classic PGA is referenced. The focused SAR images from SPGAdoes not have the problem of the shift between the blocks which can be found in the images from the traditional StripMap autofocus method. SPGA can get well focused SAR images from more universal scene because of the employment of phase error surface.
Phase Gradient Algorithm （PGA） is accomodated to focus the StripMap SAR data in this article. A new approach to StripMap SAR autofocus, StripMap PGA（SPGA）, is developed based on the difference between the received signal of StripMap SAR and SpotLight SAR and the classic PGA is referenced. The focused SAR images from SPGAdoes not have the problem of the shift between the blocks which can be found in the images from the traditional StripMap autofocus method. SPGA can get well focused SAR images from more universal scene because of the employment of phase error surface.
2005, 27(9): 1353-1356.
Abstract:
A robust correcting method for discrete spectrum in CW radar velocity measuring is proposed in this paper, t is named the method of triangle. This method, with low compution and high accuracy, is theoretically simple and easily carried out. The paper introduces the principle of this method, analyzes its correcting effects changed with noise and spectrum line numbers used, the simulation result is also given. Finally, the method of triangle is compared with energy centrobaric correction method, with the conclusion that noise has less effects on the method of triangle.
A robust correcting method for discrete spectrum in CW radar velocity measuring is proposed in this paper, t is named the method of triangle. This method, with low compution and high accuracy, is theoretically simple and easily carried out. The paper introduces the principle of this method, analyzes its correcting effects changed with noise and spectrum line numbers used, the simulation result is also given. Finally, the method of triangle is compared with energy centrobaric correction method, with the conclusion that noise has less effects on the method of triangle.
2005, 27(9): 1357-1360.
Abstract:
In some condition the present most of the methods are wake of ship or the natural interwave can be observed in remote sensing imagery. In used to detect linear features. This paper puts forward a method, which uses static boundary contour system based on biological vision and image morphological filter based on mathematical morphology to process images. And after conversion into binary image, the non-linear features are classified using binary morphological filter. The effectiveness of this algorithm is demonstrated by the test results of simulating wake images and actual SAR images of ship wakes
In some condition the present most of the methods are wake of ship or the natural interwave can be observed in remote sensing imagery. In used to detect linear features. This paper puts forward a method, which uses static boundary contour system based on biological vision and image morphological filter based on mathematical morphology to process images. And after conversion into binary image, the non-linear features are classified using binary morphological filter. The effectiveness of this algorithm is demonstrated by the test results of simulating wake images and actual SAR images of ship wakes
2005, 27(9): 1361-1364.
Abstract:
This paper is proposes to detecting radial moving ground targets from SAR image. Radical moving targets have focused image just as fixed ground clutters. The algorithm for detection and parameter estimation of radical targets has three steps. The first step isolates the SAR image frequency spectrum to positive band and negative band, then uses IFFT transform to reform two images. The second step subtracts the two-look image amplitude, It offers an approach of suppressing ground clutters and simultaneously indicating the true location of the slant-range moving target image. Finally the radical ground speed of the moving target is carried out by the estimating its Doppler centroid. This combined method is implemented by using real clutter data combined with simulated moving targets. Typical computer results are presented, which illustrate this technique＇s availability.
This paper is proposes to detecting radial moving ground targets from SAR image. Radical moving targets have focused image just as fixed ground clutters. The algorithm for detection and parameter estimation of radical targets has three steps. The first step isolates the SAR image frequency spectrum to positive band and negative band, then uses IFFT transform to reform two images. The second step subtracts the two-look image amplitude, It offers an approach of suppressing ground clutters and simultaneously indicating the true location of the slant-range moving target image. Finally the radical ground speed of the moving target is carried out by the estimating its Doppler centroid. This combined method is implemented by using real clutter data combined with simulated moving targets. Typical computer results are presented, which illustrate this technique＇s availability.
2005, 27(9): 1365-1369.
Abstract:
Traditional speckle removal methods generally result in the lost of image features. This paper presents a new approach to edge-preserving smoothing of digital SAR images based on the PDE's. A brief analysis of the principle of anisotropic nonlinear diffusion equation for image restoration is introduced, and then an edge indicator is showed in the final update equation to constrain the image edge, staying as close as possible to the input image and to restore discontinuities, which improve the ability of speckle noise removal. Comparison and experimental result show the new proposed algorithm has high performance.
Traditional speckle removal methods generally result in the lost of image features. This paper presents a new approach to edge-preserving smoothing of digital SAR images based on the PDE's. A brief analysis of the principle of anisotropic nonlinear diffusion equation for image restoration is introduced, and then an edge indicator is showed in the final update equation to constrain the image edge, staying as close as possible to the input image and to restore discontinuities, which improve the ability of speckle noise removal. Comparison and experimental result show the new proposed algorithm has high performance.
2005, 27(9): 1370-1374.
Abstract:
A practical modified autofocus algorithm for synthetic aperture radar, the iterative shift-and-correlation algorithm, is presented, Comparing with the original shift-and-correlation algorithm, the modified one can obtain more accurate estimations in worse case by incorporating the appropriate iterations, the new weightings and the auto-selecting width of the detecting window. Both the theoretical analyses and the test results indicate that the iterative shift-and-correlation algorithm can obtain more reliable results with a cost of slight increment of the computational complexity.
A practical modified autofocus algorithm for synthetic aperture radar, the iterative shift-and-correlation algorithm, is presented, Comparing with the original shift-and-correlation algorithm, the modified one can obtain more accurate estimations in worse case by incorporating the appropriate iterations, the new weightings and the auto-selecting width of the detecting window. Both the theoretical analyses and the test results indicate that the iterative shift-and-correlation algorithm can obtain more reliable results with a cost of slight increment of the computational complexity.
2005, 27(9): 1375-1378.
Abstract:
This paper detailedly analyzes precise Range Cell Migration（RCM） correction of the targets and motion error compensation of platforrn in high resolution airborne SAR data processing. The motion error of platforrn is divided into space-invariant component and space-variant component. Then the paper proposes an approach of combining RCM correction and platform MOCO using transfer function of airborne SAR system and Scaled Fourier Transform algorithm. The data simulation results verify the validity of the new method.
This paper detailedly analyzes precise Range Cell Migration（RCM） correction of the targets and motion error compensation of platforrn in high resolution airborne SAR data processing. The motion error of platforrn is divided into space-invariant component and space-variant component. Then the paper proposes an approach of combining RCM correction and platform MOCO using transfer function of airborne SAR system and Scaled Fourier Transform algorithm. The data simulation results verify the validity of the new method.
2005, 27(9): 1379-1382.
Abstract:
The key problem of calibration for low frequency ultra wide band synthetic aperture radar system is the acquisition of the scattering information of calibrators and suitable signal processing model. In this paper, the RCS of trihedral triangle reflector changing with the frequency and aspect angle is obtained using methed of moment and AWE method, and the calibration model is proposed based on time domain. The computer simulation is used to verify this calibration method, and result is agreed with the theory analysis.
The key problem of calibration for low frequency ultra wide band synthetic aperture radar system is the acquisition of the scattering information of calibrators and suitable signal processing model. In this paper, the RCS of trihedral triangle reflector changing with the frequency and aspect angle is obtained using methed of moment and AWE method, and the calibration model is proposed based on time domain. The computer simulation is used to verify this calibration method, and result is agreed with the theory analysis.
2005, 27(9): 1383-1387.
Abstract:
Range multi-aperture imaging algorithm is proved by theory that it can widen the swath and obtain high resolution at the same time. To evaluate the practicality of range multi-aperture SAR system, this paper gives quantitative errors analysis of this system and presents the corresponding amendment to the imaging algorithm.
Range multi-aperture imaging algorithm is proved by theory that it can widen the swath and obtain high resolution at the same time. To evaluate the practicality of range multi-aperture SAR system, this paper gives quantitative errors analysis of this system and presents the corresponding amendment to the imaging algorithm.
2005, 27(9): 1388-1392.
Abstract:
People can use measuring information provided by guider to establish optimal burst control algorithm in order to realize optimal burst. It is an important direction of burst control technology of missile. The optimal burst algorithm includes the estimation of time-to-go, miss distance and miss angle. In order to improve estimation accuracy and satisfy application request, it is important to filter measuring information provided by guider. The paper studied the application of converted measuring Kalman filter in parameters estimation of burst control. The algorithm filtered the information which was converted from polar coordinates to rectangle coordinates. At the same time, it eliminated the divergence caused by coordinate transform. Simulation results indicate that the application of this algorithm improved the estimation accuracy of burst control.
People can use measuring information provided by guider to establish optimal burst control algorithm in order to realize optimal burst. It is an important direction of burst control technology of missile. The optimal burst algorithm includes the estimation of time-to-go, miss distance and miss angle. In order to improve estimation accuracy and satisfy application request, it is important to filter measuring information provided by guider. The paper studied the application of converted measuring Kalman filter in parameters estimation of burst control. The algorithm filtered the information which was converted from polar coordinates to rectangle coordinates. At the same time, it eliminated the divergence caused by coordinate transform. Simulation results indicate that the application of this algorithm improved the estimation accuracy of burst control.
2005, 27(9): 1393-1397.
Abstract:
The performance of Cyclic Adaptive Beamforming （CAB） algorithm degrades severely when the estimation of the cycle frequency is not accurate. A robust CAB algorithm is proposed in this paper which overcomes the sensitivity to the Cycle Frequency Error （CFE）. Simulations show that the performance of the proposed method when applied to CFE cases is almost as good as that of the original CAB method for the case without CFE.
The performance of Cyclic Adaptive Beamforming （CAB） algorithm degrades severely when the estimation of the cycle frequency is not accurate. A robust CAB algorithm is proposed in this paper which overcomes the sensitivity to the Cycle Frequency Error （CFE）. Simulations show that the performance of the proposed method when applied to CFE cases is almost as good as that of the original CAB method for the case without CFE.
2005, 27(9): 1398-1403.
Abstract:
The Chirplet Transform（CT） have being become one of the most popular field in signal processing, which is extend from the Wavelet Transform（WT）. This paper calculate the Gaussian Chirplet Transform（GCT） by the Short-Time Fourier Transform（STFT）. At the same time, its parameters is optimized by making use of FRFT and Generalized Time-Bandwidth Product（GTBP）. Compared with WVD and STFT, GCT has been show excellent performance for the time-frequency concentration.
The Chirplet Transform（CT） have being become one of the most popular field in signal processing, which is extend from the Wavelet Transform（WT）. This paper calculate the Gaussian Chirplet Transform（GCT） by the Short-Time Fourier Transform（STFT）. At the same time, its parameters is optimized by making use of FRFT and Generalized Time-Bandwidth Product（GTBP）. Compared with WVD and STFT, GCT has been show excellent performance for the time-frequency concentration.
2005, 27(9): 1404-1407.
Abstract:
This paper proposes a new estimator for estimating the parameters of K-distribution which combines U estimator with X estimator efficiently. Simulations show that this new estimator yields shape parameter estimates with lower variance when compared with previous estimators. Parameter estimates obtained from new estimator are approximately equal to the numerically evaluated Maximum Likelihood（ML） estimates when v is low.
This paper proposes a new estimator for estimating the parameters of K-distribution which combines U estimator with X estimator efficiently. Simulations show that this new estimator yields shape parameter estimates with lower variance when compared with previous estimators. Parameter estimates obtained from new estimator are approximately equal to the numerically evaluated Maximum Likelihood（ML） estimates when v is low.
2005, 27(9): 1408-1411.
Abstract:
Coherence diffusion is an important preprocessing step for analyzing oriented structures in the image. Previous coherence diffusion methods for image enhancement could not recognize weak boundaries. In this paper, an efficient diffusion approach is presented. A new structure tensor integrating the second-order directional derivative information is designed, which can precisely analyze complex weak edges in the image. By combining the proposed structure tensor and the classical one as complementary descriptor, the improved diffusion tensor is constructed to detect strong edges simultaneously. Furthermore, parallel AOS （Additive Operator Splitting） scheme is applied to implement numerical solution, which is faster than usual numerical approach. Promising experimental results of several real images demonstrate that the new diffusion approach can preserve important strong edges and weak edges precisely while removing the noise.
Coherence diffusion is an important preprocessing step for analyzing oriented structures in the image. Previous coherence diffusion methods for image enhancement could not recognize weak boundaries. In this paper, an efficient diffusion approach is presented. A new structure tensor integrating the second-order directional derivative information is designed, which can precisely analyze complex weak edges in the image. By combining the proposed structure tensor and the classical one as complementary descriptor, the improved diffusion tensor is constructed to detect strong edges simultaneously. Furthermore, parallel AOS （Additive Operator Splitting） scheme is applied to implement numerical solution, which is faster than usual numerical approach. Promising experimental results of several real images demonstrate that the new diffusion approach can preserve important strong edges and weak edges precisely while removing the noise.
2005, 27(9): 1412-1415.
Abstract:
In this paper, a mistake made the multi-rate kinematic model is improv by Hong （2001） is pointed ed. And then, a multi-scan out and corrected, and the estimation performance of probabilistic data association algorithm is presented With the introduction of double gates, the calculation amount of the presented algorithm is decreased efficiently. Finally, the performance of multi-scan probabilistic data association is studied under different clutter density.
In this paper, a mistake made the multi-rate kinematic model is improv by Hong （2001） is pointed ed. And then, a multi-scan out and corrected, and the estimation performance of probabilistic data association algorithm is presented With the introduction of double gates, the calculation amount of the presented algorithm is decreased efficiently. Finally, the performance of multi-scan probabilistic data association is studied under different clutter density.
2005, 27(9): 1416-1419.
Abstract:
Using the Kalman filtering method, based on white noise estimation theory, under the linear minimum variance information fusion criterion, two-sensor information fusion steady-state optimal Wiener filter, smoother and predictor are presented for the multichannel Auto-Regressive Moving Average（ARMA） signals, where the optimal weighting matrices and minimum fused error variance matrix are given. Compared with the single sensor case, the accuracy of the filter is improved. A simulation example of a radar tracking system shows its effectiveness.
Using the Kalman filtering method, based on white noise estimation theory, under the linear minimum variance information fusion criterion, two-sensor information fusion steady-state optimal Wiener filter, smoother and predictor are presented for the multichannel Auto-Regressive Moving Average（ARMA） signals, where the optimal weighting matrices and minimum fused error variance matrix are given. Compared with the single sensor case, the accuracy of the filter is improved. A simulation example of a radar tracking system shows its effectiveness.
2005, 27(9): 1420-1424.
Abstract:
Automatic segmentation of brain magnetic resonance images is a critical problem in many medical imaging applications. In this paper, a robust automated segmentation algorithm is presented for the brain magnetic resonance images. The segmentation framework is composed of three stages. First, it uses level set method to perform the brain stripping operation. In the second stage, it compensates for nonuniformity in the brain image based on computing estimates of tissue intensity variation. Finally, a maximum aposteriori classifier is used to partition the brain into gray matter, white matter, and cerebrospinal fluid. The proposed method has been tested using magnetic resonance dada. This algorithm may be applied to various research and clinical investigations in which brain segmentation and volume measurement involving Magnetic resonance images dada are needed.
Automatic segmentation of brain magnetic resonance images is a critical problem in many medical imaging applications. In this paper, a robust automated segmentation algorithm is presented for the brain magnetic resonance images. The segmentation framework is composed of three stages. First, it uses level set method to perform the brain stripping operation. In the second stage, it compensates for nonuniformity in the brain image based on computing estimates of tissue intensity variation. Finally, a maximum aposteriori classifier is used to partition the brain into gray matter, white matter, and cerebrospinal fluid. The proposed method has been tested using magnetic resonance dada. This algorithm may be applied to various research and clinical investigations in which brain segmentation and volume measurement involving Magnetic resonance images dada are needed.
2005, 27(9): 1425-1428.
Abstract:
By exploring the phase information among symbols of the Direct Sequence Spread Spectrum （DS-SS） signal, a novel de-noising approach, used in low signal noise ratio environment, is presented. By coherent integration, this method can fully retain the signal characters and separate I/Q components of the QPSK signal while restraining noise. Combined with conventional parameter estimation methods, the carrier frequency and chip rate of the DS-SS signal can be estimated. Computer simulation confirms its effectiveness.
By exploring the phase information among symbols of the Direct Sequence Spread Spectrum （DS-SS） signal, a novel de-noising approach, used in low signal noise ratio environment, is presented. By coherent integration, this method can fully retain the signal characters and separate I/Q components of the QPSK signal while restraining noise. Combined with conventional parameter estimation methods, the carrier frequency and chip rate of the DS-SS signal can be estimated. Computer simulation confirms its effectiveness.
2005, 27(9): 1429-1432.
Abstract:
Chaos Neural Network（CNN）is applied to solve channel assignment problem in this paper. Energy function expression of channel assignment as well as mathematic model of CNN are put forward. Lyapunov exponent is calculated to judge whether there is chaos in CNN, and the influence on chaos characteristic caused by parameters of CNN model is discussed, then channel assignment algorithm based on CNN is proposed. Simulation results indicate that CNN has stronger ability to search global optimal solution and quicker convergence speed than Hopfield network, for its complicated transient chaos characteristic.
Chaos Neural Network（CNN）is applied to solve channel assignment problem in this paper. Energy function expression of channel assignment as well as mathematic model of CNN are put forward. Lyapunov exponent is calculated to judge whether there is chaos in CNN, and the influence on chaos characteristic caused by parameters of CNN model is discussed, then channel assignment algorithm based on CNN is proposed. Simulation results indicate that CNN has stronger ability to search global optimal solution and quicker convergence speed than Hopfield network, for its complicated transient chaos characteristic.
2005, 27(9): 1433-1436.
Abstract:
Orientation of the receive and transmit antenna arrays is always omitted while researching the performance of wireless channels. This paper investigates the impact on spatial correlation and capacity of MIMO （Multiple-lnput Multiple-Output） wireless channels, and obtains that the impact can not be neglected if angular spread is small, and that the antenna arrays should be rotated to make array＇s normal point to the mean direction of arrival or departure （DOA or DOD） to attain higher capacity. Numerical results verify the impact on spatial correlation, and show that it increases with the departure ofarray＇s normal from the mean DOA or DOD. The simulation results indicate that orientation of the array with smaller angular spread dominates the impact on MIMO channel capacity and that increasing angular spread diminishes, or even eliminates this impact.
Orientation of the receive and transmit antenna arrays is always omitted while researching the performance of wireless channels. This paper investigates the impact on spatial correlation and capacity of MIMO （Multiple-lnput Multiple-Output） wireless channels, and obtains that the impact can not be neglected if angular spread is small, and that the antenna arrays should be rotated to make array＇s normal point to the mean direction of arrival or departure （DOA or DOD） to attain higher capacity. Numerical results verify the impact on spatial correlation, and show that it increases with the departure ofarray＇s normal from the mean DOA or DOD. The simulation results indicate that orientation of the array with smaller angular spread dominates the impact on MIMO channel capacity and that increasing angular spread diminishes, or even eliminates this impact.
2005, 27(9): 1437-1440.
Abstract:
In this paper, an iterative joint channel-estimation and symbol-detection algorithm based on prediction is presented for orthogonal frequency-division multiplexing systems. Considering the correlation between impulse responses, the prediction method is introduced into the iterative channel estimation. The initial channel value of iterative estimation is predicted in each symbol. Several prediction methods are simulated and compared. The simulation results show that contrasted to the conventional scheme the proposed algorithm improves the convergence capability and system performance dramatically.
In this paper, an iterative joint channel-estimation and symbol-detection algorithm based on prediction is presented for orthogonal frequency-division multiplexing systems. Considering the correlation between impulse responses, the prediction method is introduced into the iterative channel estimation. The initial channel value of iterative estimation is predicted in each symbol. Several prediction methods are simulated and compared. The simulation results show that contrasted to the conventional scheme the proposed algorithm improves the convergence capability and system performance dramatically.
2005, 27(9): 1441-1445.
Abstract:
In this paper, the closed loop transmit diversity technique is investigated. The RAKE receiver model and the weighting vector algorithm are presented. Since the feedback delay in the practical systems has considerable effect on the receiver performance of the closed loop transmit diversity technique, the performance of the RAKE receiver with feedback delay in the time variant wireless channel is analyzed and compared with that of the open loop mode. Theoretical analysis and simulation results show that the closed loop transmit diversity technique outperforms the open loop technique in the environments with low speeds and low path signal-to-noise ratios.
In this paper, the closed loop transmit diversity technique is investigated. The RAKE receiver model and the weighting vector algorithm are presented. Since the feedback delay in the practical systems has considerable effect on the receiver performance of the closed loop transmit diversity technique, the performance of the RAKE receiver with feedback delay in the time variant wireless channel is analyzed and compared with that of the open loop mode. Theoretical analysis and simulation results show that the closed loop transmit diversity technique outperforms the open loop technique in the environments with low speeds and low path signal-to-noise ratios.
2005, 27(9): 1446-1449.
Abstract:
A subspace-based channel estimation method for Single-Carrier Block Transmission （SCBT） systems is presented, which estimates frequency-selective channel blindly in frequency domain, based on zero-padding technology in SCBT system. Sufficient conditions for identifiability are also given. The performance of this method is better than that of conventional oversampling methods, and it is robust to over-estimated channel order. Finally, computer simulations confirm its efficiency.
A subspace-based channel estimation method for Single-Carrier Block Transmission （SCBT） systems is presented, which estimates frequency-selective channel blindly in frequency domain, based on zero-padding technology in SCBT system. Sufficient conditions for identifiability are also given. The performance of this method is better than that of conventional oversampling methods, and it is robust to over-estimated channel order. Finally, computer simulations confirm its efficiency.
2005, 27(9): 1450-1453.
Abstract:
In this paper, an improved method of constructing multiple quasi-orthogonal spreading codes and a new modulation and demodulation scheme based on position mapping are proposed on the research of methods of constructing multiple quasi-orthogonal codes, using new method of codes grouping and position mapping, and making the demodulating of the quasi-orthogonal branches into the combination of demodulating of orthogonal sequences codes, that will obtain better demodulation performance. Analysis and simulation prove that this scheme can reduce obviously the computer complexity in the receiver side. It will increase transmission speed of information and reduce bit error probability.
In this paper, an improved method of constructing multiple quasi-orthogonal spreading codes and a new modulation and demodulation scheme based on position mapping are proposed on the research of methods of constructing multiple quasi-orthogonal codes, using new method of codes grouping and position mapping, and making the demodulating of the quasi-orthogonal branches into the combination of demodulating of orthogonal sequences codes, that will obtain better demodulation performance. Analysis and simulation prove that this scheme can reduce obviously the computer complexity in the receiver side. It will increase transmission speed of information and reduce bit error probability.
2005, 27(9): 1454-1458.
Abstract:
In mobile OFDM system, this paper pays much attention to the character of time domain result of LS channel estimation. At the same time, it is noticed that the character of Channel Impulse Response （CIR） is finite impulse response. A new algorithm is proposed to estimate channel effective order, and then the estimated value is used to truncate the time-domain result of channel estimation achieved by LS algorithm in order to reduce Mean Square Error （MSE） of LS algorithm due to noise and Inter-Carrier Interference （ICI）. Performance improvement of LS algorithm and its enhancement on Symbol Error Rate （SER） have been evaluated by computer simulation.
In mobile OFDM system, this paper pays much attention to the character of time domain result of LS channel estimation. At the same time, it is noticed that the character of Channel Impulse Response （CIR） is finite impulse response. A new algorithm is proposed to estimate channel effective order, and then the estimated value is used to truncate the time-domain result of channel estimation achieved by LS algorithm in order to reduce Mean Square Error （MSE） of LS algorithm due to noise and Inter-Carrier Interference （ICI）. Performance improvement of LS algorithm and its enhancement on Symbol Error Rate （SER） have been evaluated by computer simulation.
2005, 27(9): 1459-1462.
Abstract:
Focused on the scenario that none of the current standards achieves user identity＇s confidentiality, two enhanced methods are proposed, respectively based on public key cryptography and symmetric key cryptography, in which each user＇s real identity is concealed among many users＇ identities. So attackers can not capture the concrete identity information and user identity confidentiality is improved obviously. The performance of the two methods is analyzed and compared. And the proposed methods can be used in other mobile communication technologies.
Focused on the scenario that none of the current standards achieves user identity＇s confidentiality, two enhanced methods are proposed, respectively based on public key cryptography and symmetric key cryptography, in which each user＇s real identity is concealed among many users＇ identities. So attackers can not capture the concrete identity information and user identity confidentiality is improved obviously. The performance of the two methods is analyzed and compared. And the proposed methods can be used in other mobile communication technologies.
2005, 27(9): 1463-1466.
Abstract:
Identifiability is one of several security requirements of general proxy signature schemes, i.e. a verifier can determine the identity of the corresponding proxy signer from a proxy signature. In special application, the original signer wants to conceal the identity of the corresponding proxy signer in the proxy signature. The verifier can not recognize the identity of the proxy signer from the proxy signature. In the case of a later dispute, the verifier can reveal the real identity of the proxy signer with the help of the original signer from the proxy signature. In the paper, a new proxy signature scheme should satisfy this requirement.
Identifiability is one of several security requirements of general proxy signature schemes, i.e. a verifier can determine the identity of the corresponding proxy signer from a proxy signature. In special application, the original signer wants to conceal the identity of the corresponding proxy signer in the proxy signature. The verifier can not recognize the identity of the proxy signer from the proxy signature. In the case of a later dispute, the verifier can reveal the real identity of the proxy signer with the help of the original signer from the proxy signature. In the paper, a new proxy signature scheme should satisfy this requirement.
2005, 27(9): 1467-1469.
Abstract:
In order to investigate the cryptographical properties of the Multi-outputting Boolean functions under non-uniformity of arguments, this paper defines the spectrum and eigenvalue, presents the general expression and estimation formula, and computes the upper bounds ofagonic functions and t -resilient functions.
In order to investigate the cryptographical properties of the Multi-outputting Boolean functions under non-uniformity of arguments, this paper defines the spectrum and eigenvalue, presents the general expression and estimation formula, and computes the upper bounds ofagonic functions and t -resilient functions.
2005, 27(9): 1470-1475.
Abstract:
The bluetooth combiner, a combiner with four bit memory, is the stream cipher used in bluetooth protocols. The expression and computation of correlation coefficients between inputs and outputs of this combiner is difficult, while this is the base of correlation analysis and correlation attack to it. In this paper, the formulas for correlation coefficients and conditional correlation coefficients of general combiners with memory are presented, with which the coefficients can be computed fast. By using these formulas, all kinds of correlation coefficients ofbluetooth combiner are computed, and some results are list in the paper.
The bluetooth combiner, a combiner with four bit memory, is the stream cipher used in bluetooth protocols. The expression and computation of correlation coefficients between inputs and outputs of this combiner is difficult, while this is the base of correlation analysis and correlation attack to it. In this paper, the formulas for correlation coefficients and conditional correlation coefficients of general combiners with memory are presented, with which the coefficients can be computed fast. By using these formulas, all kinds of correlation coefficients ofbluetooth combiner are computed, and some results are list in the paper.
2005, 27(9): 1476-1478.
Abstract:
A secure and efficient （t, n） multisecret sharing authenticating scheme based on double shadow is proposed. The main merits are that the participant can reuse his shadows to recover the sharing multiple secrets that the dealer given and it only needs three parameters to reconstruct one secret, and need not to perform a zero-knowledge protocol to prevent the participant cheating. The proposed scheme is clearly superior to the other existing schemes in terms of both computational costs and communication costs.
A secure and efficient （t, n） multisecret sharing authenticating scheme based on double shadow is proposed. The main merits are that the participant can reuse his shadows to recover the sharing multiple secrets that the dealer given and it only needs three parameters to reconstruct one secret, and need not to perform a zero-knowledge protocol to prevent the participant cheating. The proposed scheme is clearly superior to the other existing schemes in terms of both computational costs and communication costs.
2005, 27(9): 1479-1482.
Abstract:
The maximization of data rate under the constraint of total transmit power and bit error rate is a considerable issue in OFDM system. Recognizing that the number of bits on each subcarrier must be a discrete number for real systems, this paper proposed two bit allocation algorithms which are modified greedy algorithm and water filling level binary searching algorithm. Simulation results show that the complexity of modified greedy algorithm is 10% of that of greedy algorithm and 5-7 iterations are enough for 0.5% data rate loss when SNR is above 10dB.
The maximization of data rate under the constraint of total transmit power and bit error rate is a considerable issue in OFDM system. Recognizing that the number of bits on each subcarrier must be a discrete number for real systems, this paper proposed two bit allocation algorithms which are modified greedy algorithm and water filling level binary searching algorithm. Simulation results show that the complexity of modified greedy algorithm is 10% of that of greedy algorithm and 5-7 iterations are enough for 0.5% data rate loss when SNR is above 10dB.
2005, 27(9): 1483-1487.
Abstract:
Because the fiber links share the common physical resources, they have the Correlated Link Failure Probability （CLFP）. Based on CLFP and Differentiated Reliability （DiR）, the dual-link failures problem has been studied, and a novel protection algorithm, which is called Shared-Path Protection for Dual-Link Failures with DiR （SPPDLF-DiR）, has been proposed for survivable WDM networks. Under dynamic traffic with different load, the performances of SPPDLF-DiR are simulated. The results show that SPPDLF-DiR not only can satisfy the specific requirements of users but also can effectively improve the resource utilization ratio and reduce the blocking ratio.
Because the fiber links share the common physical resources, they have the Correlated Link Failure Probability （CLFP）. Based on CLFP and Differentiated Reliability （DiR）, the dual-link failures problem has been studied, and a novel protection algorithm, which is called Shared-Path Protection for Dual-Link Failures with DiR （SPPDLF-DiR）, has been proposed for survivable WDM networks. Under dynamic traffic with different load, the performances of SPPDLF-DiR are simulated. The results show that SPPDLF-DiR not only can satisfy the specific requirements of users but also can effectively improve the resource utilization ratio and reduce the blocking ratio.
2005, 27(9): 1488-1492.
Abstract:
The problem that how to set the price to maximize revenue in WCDMA networks is investigated in this paper. Instead of adopting congestion pricing mechanism, this paper imposes fixed usage price on throughput of each user, which is assumed to be the function of network congestion and usage cost. Based on above assumptions, the net utility functions of users are provided and Stackelberg game is adopted to model the interaction between network and users. That is, network sets the price to maximize revenue, and in response to the price, users maximize their net utility functions to achieve equilibriums. The paper provides the quantitative relation between revenue and the number of admitted users, and infers that although, technically speaking, network can increase system capacity to admit more users through decreasing transmission rate of users, the network has no incentive to adopt this policy. Conversely, network has the incentive to pert＇arm congestion control.
The problem that how to set the price to maximize revenue in WCDMA networks is investigated in this paper. Instead of adopting congestion pricing mechanism, this paper imposes fixed usage price on throughput of each user, which is assumed to be the function of network congestion and usage cost. Based on above assumptions, the net utility functions of users are provided and Stackelberg game is adopted to model the interaction between network and users. That is, network sets the price to maximize revenue, and in response to the price, users maximize their net utility functions to achieve equilibriums. The paper provides the quantitative relation between revenue and the number of admitted users, and infers that although, technically speaking, network can increase system capacity to admit more users through decreasing transmission rate of users, the network has no incentive to adopt this policy. Conversely, network has the incentive to pert＇arm congestion control.
2005, 27(9): 1493-1497.
Abstract:
In multi-cell Wireless Local Area Networks （WLAN）, co-channel interference between access points, and interference between co-channel users located in neighbored cells are existed, which lead the system performance different from the situation in a single-cell WLAN. A system throughput estimation method is proposed. Three important features of this method are that co-channel overlapping is allowed, hybrid data rates are allowed, and non-uniform distribution of users is allowed. The simulation results on the access point placement and the channel assignment show that the estimation method meets system design.
In multi-cell Wireless Local Area Networks （WLAN）, co-channel interference between access points, and interference between co-channel users located in neighbored cells are existed, which lead the system performance different from the situation in a single-cell WLAN. A system throughput estimation method is proposed. Three important features of this method are that co-channel overlapping is allowed, hybrid data rates are allowed, and non-uniform distribution of users is allowed. The simulation results on the access point placement and the channel assignment show that the estimation method meets system design.
2005, 27(9): 1498-1502.
Abstract:
This paper studies on handoff management in hierarchically multi-hop wireless networks and proposes a novel user handoff algorithm and mobile base station route handoff strategy. The user handoff algorithm can reduce the number of handoff and balance the load among mobile base stations in dynamic topology. Meanwhile the mobile base station handoff algorithm always tries to find an alternate route from base station locally, which can achieve fast handoff and seamless handoffwith little overhead.
This paper studies on handoff management in hierarchically multi-hop wireless networks and proposes a novel user handoff algorithm and mobile base station route handoff strategy. The user handoff algorithm can reduce the number of handoff and balance the load among mobile base stations in dynamic topology. Meanwhile the mobile base station handoff algorithm always tries to find an alternate route from base station locally, which can achieve fast handoff and seamless handoffwith little overhead.
2005, 27(9): 1503-1506.
Abstract:
Trajectory estimation using the measurement of arrival angles from space-based infrared sensors is one of the key technologies in the space early warning system. This paper presents a pseudolinear measure-Kalman estimator for trajectory estimation in boost-phase. Compared with EKF and CRLB, this estimator is more precise.
Trajectory estimation using the measurement of arrival angles from space-based infrared sensors is one of the key technologies in the space early warning system. This paper presents a pseudolinear measure-Kalman estimator for trajectory estimation in boost-phase. Compared with EKF and CRLB, this estimator is more precise.
2005, 27(9): 1507-1509.
Abstract:
The paper presents a hybrid method based on FDTD and ADI-FDTD, introduces a method of weighted average to reduce the reflection caused by two different methods on the boundary, and presents a celerity method for the linear, lossless and isotropic medium. The simulation shows that the method is feasible.
The paper presents a hybrid method based on FDTD and ADI-FDTD, introduces a method of weighted average to reduce the reflection caused by two different methods on the boundary, and presents a celerity method for the linear, lossless and isotropic medium. The simulation shows that the method is feasible.
2005, 27(9): 1510-1512.
Abstract:
In this paper, a unified formulation to determine the terminal currents of an arbitrarily bended cable excited by a plane wave at any polarization angle is presented. Both the influence of the earth and the curve of cable on the terminal currents are considered in this paper. The method given in this paper is of great significance to the reinforcement of the electronic systems and EMC research.
In this paper, a unified formulation to determine the terminal currents of an arbitrarily bended cable excited by a plane wave at any polarization angle is presented. Both the influence of the earth and the curve of cable on the terminal currents are considered in this paper. The method given in this paper is of great significance to the reinforcement of the electronic systems and EMC research.
