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2006 Vol. 28, No. 7
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2006, 28(7): 1153-1159.
Abstract:
A hybrid algorithm of the BP-ANN/GA (Back Propagation Artificial Neural Network and Genetic Algorithm) is developed to optimize the initial weights and make fast convergence of the BP-ANN. This algorithm is applied to classification of urban terrain surfaces with fused data of Landsat ETM+ and ERS-2 SAR. An example of the Shanghai Pudong area using both the Landsat ETM+ and ERS-2 SAR image data well demonstrates the classification speed and accuracy of the algorithm.
A hybrid algorithm of the BP-ANN/GA (Back Propagation Artificial Neural Network and Genetic Algorithm) is developed to optimize the initial weights and make fast convergence of the BP-ANN. This algorithm is applied to classification of urban terrain surfaces with fused data of Landsat ETM+ and ERS-2 SAR. An example of the Shanghai Pudong area using both the Landsat ETM+ and ERS-2 SAR image data well demonstrates the classification speed and accuracy of the algorithm.
2006, 28(7): 1160-1164.
Abstract:
Colorization of gray-scale image is in general an active and challenging area of research in image processing. In this paper current colorizing algorithms are summarized, of which Levins method is analyzed in particular. According to the speed dropping of Levins method in processing large scale images, a new scheme based on over-segmentation is proposed. Experiments show that the new scheme can remarkably quicken the processing of large scale images, nearly without degrading the colorizing effect.
Colorization of gray-scale image is in general an active and challenging area of research in image processing. In this paper current colorizing algorithms are summarized, of which Levins method is analyzed in particular. According to the speed dropping of Levins method in processing large scale images, a new scheme based on over-segmentation is proposed. Experiments show that the new scheme can remarkably quicken the processing of large scale images, nearly without degrading the colorizing effect.
2006, 28(7): 1165-1168.
Abstract:
A hybrid filter training and design method for adaptive image noise cancellation with establishing noise channel model is presented in this paper. Trainings are performed with input and output test images for channels of different types and/or different intensities to establish channel-adaptive hybrid filter models. In practice the image transferred through the specific channel is filtered blindly by corresponding model to maintain detail and eliminate noise simultaneously. For certificating the efficiency of this design method, Gaussian weighted median filters are adopted to remove well known channel noise, i.e., pepper and salt noise and uniform distributed impulse noise, in this framework. The results outperform some prior methods markedly. This design method can be generalized to other filters with adaptability to treat different channel noise flexibly.
A hybrid filter training and design method for adaptive image noise cancellation with establishing noise channel model is presented in this paper. Trainings are performed with input and output test images for channels of different types and/or different intensities to establish channel-adaptive hybrid filter models. In practice the image transferred through the specific channel is filtered blindly by corresponding model to maintain detail and eliminate noise simultaneously. For certificating the efficiency of this design method, Gaussian weighted median filters are adopted to remove well known channel noise, i.e., pepper and salt noise and uniform distributed impulse noise, in this framework. The results outperform some prior methods markedly. This design method can be generalized to other filters with adaptability to treat different channel noise flexibly.
2006, 28(7): 1169-1173.
Abstract:
Image segmentation is a significant part in image processing field. Inspired by the threshold-based segmentation methods, a novel algorithm based on immune clone selection and optimal entropy theory is presented in this paper. Immune clone selection algorithm performs not only local but also global search, and has better performance than Genetic Algorithm(GA) in searching for the optimal entropy threshold of images. The algorithm is depicted in detail and the computational complexity is given. In experiments, natural image and SAR image are selected, and the algorithm runs ten times independently and the mean numbers of function values are presented as the evaluation of the algorithm complexity. It shows that the algorithm presented in this paper can find better solutions with small generation and mean numbers of function values. So this method has better performance in stabilization and convergence than GA. Experimental results show that this method is feasible and effective.
Image segmentation is a significant part in image processing field. Inspired by the threshold-based segmentation methods, a novel algorithm based on immune clone selection and optimal entropy theory is presented in this paper. Immune clone selection algorithm performs not only local but also global search, and has better performance than Genetic Algorithm(GA) in searching for the optimal entropy threshold of images. The algorithm is depicted in detail and the computational complexity is given. In experiments, natural image and SAR image are selected, and the algorithm runs ten times independently and the mean numbers of function values are presented as the evaluation of the algorithm complexity. It shows that the algorithm presented in this paper can find better solutions with small generation and mean numbers of function values. So this method has better performance in stabilization and convergence than GA. Experimental results show that this method is feasible and effective.
2006, 28(7): 1174-1178.
Abstract:
Electronic Digital Image Stabilization (EDIS) system has a large amount of data and intensive computation. The real-time implementation of EDIS system entails rapid processing of data. The characteristics of video and image series process are the data high parallelism and repeating computation. According to the requirements and characteristics of system, using efficient C++ with inline SIMD (Single Instruction Multiple Data) and multi-thread programming to achieve real-time performance of the system in conventional PC. The block-matching motion estimation, with SAD (Sum of Absolute Differences) criterion, with modified three-step search strategy in conjunction with diamond search technology, is used to reduce computation and accelerate the execution. The stabilization system uses Kalman filter to remove high-frequency image jitter with retained smooth global movements. The results of test show that it is possible to implement an efficient and robust real-time stabilization system in conventional PC.
Electronic Digital Image Stabilization (EDIS) system has a large amount of data and intensive computation. The real-time implementation of EDIS system entails rapid processing of data. The characteristics of video and image series process are the data high parallelism and repeating computation. According to the requirements and characteristics of system, using efficient C++ with inline SIMD (Single Instruction Multiple Data) and multi-thread programming to achieve real-time performance of the system in conventional PC. The block-matching motion estimation, with SAD (Sum of Absolute Differences) criterion, with modified three-step search strategy in conjunction with diamond search technology, is used to reduce computation and accelerate the execution. The stabilization system uses Kalman filter to remove high-frequency image jitter with retained smooth global movements. The results of test show that it is possible to implement an efficient and robust real-time stabilization system in conventional PC.
2006, 28(7): 1179-1182.
Abstract:
Based on the Kalman filtering method and white noise estimation theory, under the linear minimum variance optimal information fusion criterion weighted by matrices，a multisensor distributed fusion optimal white noise deconvolution filter is presented for systems with ARMA colored measurement noise，where the formulas of computing cross-covariances among local estimation errors by Lyapunov equations are derived，which is applied to compute optimal weights．Compared to the single sensor case， the accuracy of fused estimators is improved． It can be applied to signal processing in oil seismic exploration． A simulation example for three-sensor distributed fusion Bernoulli-Gaussian white noise deconvolution smoother shows its effectiveness．
Based on the Kalman filtering method and white noise estimation theory, under the linear minimum variance optimal information fusion criterion weighted by matrices，a multisensor distributed fusion optimal white noise deconvolution filter is presented for systems with ARMA colored measurement noise，where the formulas of computing cross-covariances among local estimation errors by Lyapunov equations are derived，which is applied to compute optimal weights．Compared to the single sensor case， the accuracy of fused estimators is improved． It can be applied to signal processing in oil seismic exploration． A simulation example for three-sensor distributed fusion Bernoulli-Gaussian white noise deconvolution smoother shows its effectiveness．
2006, 28(7): 1183-1187.
Abstract:
This paper first proposes a new method for evaluating the reliability of cepstral components and extends the marginalisation technique to cepstral recognizers. Then a noise adaptive multi-stream hybrid sub-band approach is proposed for robust speech recognition by making use of the complemental performances between full-band and sub-band cepstral marginalisation recognizers in different noises. Experimental results show that the proposed approach can turn to the less distorted data stream automatically and improve the robustness of the speech recognizer in various noisy environments effectively.
This paper first proposes a new method for evaluating the reliability of cepstral components and extends the marginalisation technique to cepstral recognizers. Then a noise adaptive multi-stream hybrid sub-band approach is proposed for robust speech recognition by making use of the complemental performances between full-band and sub-band cepstral marginalisation recognizers in different noises. Experimental results show that the proposed approach can turn to the less distorted data stream automatically and improve the robustness of the speech recognizer in various noisy environments effectively.
2006, 28(7): 1188-1191.
Abstract:
The characteristics of Uyghur, Chinese and English scripts are totally different. A Uyghur, Chinese and English multilingual document recognition system is implemented the first time based on the multilingual OCR system design principle, which includes multi-layer character language estimation and suitable adjustment. At first, the language property of each text block is estimated according to the characteristics of Uyghur, Chinese and English scripts. After that, language-oriented character segmentation algorithms are performed on text blocks, and the character recognition confidence is used to judge whether the results of character segmentation and language property estimation of a text block are right. Experimental results show the recognition accuracy of Uyghur, Chinese and English multilingual documents achieves 96.4% and above.
The characteristics of Uyghur, Chinese and English scripts are totally different. A Uyghur, Chinese and English multilingual document recognition system is implemented the first time based on the multilingual OCR system design principle, which includes multi-layer character language estimation and suitable adjustment. At first, the language property of each text block is estimated according to the characteristics of Uyghur, Chinese and English scripts. After that, language-oriented character segmentation algorithms are performed on text blocks, and the character recognition confidence is used to judge whether the results of character segmentation and language property estimation of a text block are right. Experimental results show the recognition accuracy of Uyghur, Chinese and English multilingual documents achieves 96.4% and above.
2006, 28(7): 1192-1195.
Abstract:
Walsh-Haar function system is a new kind of function systems that has good global/local property. Discrete Walsh-Haar transformation is an orthogonal transformation that can be widely used in signal processing. In this paper, a new type of transformation,discrete Walsh-Haar transformation, is proposed, and the fast algorithm of discrete Walsh-Haar transformation is studied based on the dichotomous technique. The idea and method used to design the fast algorithm in this paper can be used to study the fast algorithms of other order discrete Walsh-Haar transformations and other discrete orthogonal transformations.
Walsh-Haar function system is a new kind of function systems that has good global/local property. Discrete Walsh-Haar transformation is an orthogonal transformation that can be widely used in signal processing. In this paper, a new type of transformation,discrete Walsh-Haar transformation, is proposed, and the fast algorithm of discrete Walsh-Haar transformation is studied based on the dichotomous technique. The idea and method used to design the fast algorithm in this paper can be used to study the fast algorithms of other order discrete Walsh-Haar transformations and other discrete orthogonal transformations.
2006, 28(7): 1196-1200.
Abstract:
The traditional Constant Modulus (CM) beamformers are found to degrade in impulsive noise environment. In this paper， -stable distribution is introduced as a model of impulsive noise. And a robust CM beamformer is proposed. Steady -state of the beamformer is analyzed based on fractional low-order statistics theory. Computer simulations verify the analysis.
The traditional Constant Modulus (CM) beamformers are found to degrade in impulsive noise environment. In this paper， -stable distribution is introduced as a model of impulsive noise. And a robust CM beamformer is proposed. Steady -state of the beamformer is analyzed based on fractional low-order statistics theory. Computer simulations verify the analysis.
2006, 28(7): 1201-1203.
Abstract:
After comparing Learning Vector Quantization (LVQ) algorithm and Generalized Learning Vector Quantization (GLVQ) algorithm, this paper establishes a GLVQ-based classification model for remote sensing image. With the experimental applications of land-over classification with the presented model, the GLVQ classifier has higher recognition rate, faster convergence speed and wider adaption range than conventional classifier and LVQ classifier.
After comparing Learning Vector Quantization (LVQ) algorithm and Generalized Learning Vector Quantization (GLVQ) algorithm, this paper establishes a GLVQ-based classification model for remote sensing image. With the experimental applications of land-over classification with the presented model, the GLVQ classifier has higher recognition rate, faster convergence speed and wider adaption range than conventional classifier and LVQ classifier.
2006, 28(7): 1204-1208.
Abstract:
A new multitarget tracking method based on multidimensional assignment algorithm is developed for passive DOA systems in the paper. The method combines 3D datum line least cost algorithm and dynamic 2D assignment algorithm. The key features of the proposed approach are as follows: First, 3D datum line least cost algorithm is a fast measure data association approach, which cuts candidate associations very fast and reduces the calculations of association costs and completes track initiation. Second, the associations of measurements and tracks are made by dynamic 2D assignment algorithm. Simulation results prove that the proposed algorithm is effective to multitarget tracking for passive DOA system.
A new multitarget tracking method based on multidimensional assignment algorithm is developed for passive DOA systems in the paper. The method combines 3D datum line least cost algorithm and dynamic 2D assignment algorithm. The key features of the proposed approach are as follows: First, 3D datum line least cost algorithm is a fast measure data association approach, which cuts candidate associations very fast and reduces the calculations of association costs and completes track initiation. Second, the associations of measurements and tracks are made by dynamic 2D assignment algorithm. Simulation results prove that the proposed algorithm is effective to multitarget tracking for passive DOA system.
2006, 28(7): 1209-1214.
Abstract:
The surveillance space of Phased Array Radar(PAR) supported by early warning system is studied in the paper under the background of Ballistic Missile Defense(BMD). Firstly, surveillance space of PAR without prior indication information is discussed. After analyzing the trajectory prediction and its precision, the recurrence algorithms for positions and radiuses, and coordinates transformation are presented, and the small-window surveillance spaces model for PAR based on trajectory prediction is established. Additionally its detection performance is compared with whole-space searching. Finally, the model is demonstrated using simulation.
The surveillance space of Phased Array Radar(PAR) supported by early warning system is studied in the paper under the background of Ballistic Missile Defense(BMD). Firstly, surveillance space of PAR without prior indication information is discussed. After analyzing the trajectory prediction and its precision, the recurrence algorithms for positions and radiuses, and coordinates transformation are presented, and the small-window surveillance spaces model for PAR based on trajectory prediction is established. Additionally its detection performance is compared with whole-space searching. Finally, the model is demonstrated using simulation.
2006, 28(7): 1215-1218.
Abstract:
The redundant contourlet transform implemented by undecimated pyramidal decomposition and directional filter bank is proposed. The circular symmetric filter bank satisfying perfect reconstruction conditions in the undecimated pyramidal decomposition is designed by McClellan transform. The adaptive local statistical model in the redundant contourlet domain and MAP estimator are employed to reduce speckle noise in SAR images. Compared with the despeckling methods based on stationary wavelet and contourlet transform, the proposed algorithm can reduce speckle noise more effectively while preserving the edges of the SAR images.
The redundant contourlet transform implemented by undecimated pyramidal decomposition and directional filter bank is proposed. The circular symmetric filter bank satisfying perfect reconstruction conditions in the undecimated pyramidal decomposition is designed by McClellan transform. The adaptive local statistical model in the redundant contourlet domain and MAP estimator are employed to reduce speckle noise in SAR images. Compared with the despeckling methods based on stationary wavelet and contourlet transform, the proposed algorithm can reduce speckle noise more effectively while preserving the edges of the SAR images.
2006, 28(7): 1219-1222.
Abstract:
Multi-polarization, low frequency Ultra Wide Band Synthetic Aperture Radar (UWB SAR) is one of the most important aspects of the radar technology. The low frequency, UWB and large processing angle result that the polarimetric calibration for regular SAR system cannot be used. In this paper, based on the frequency-domain processing model of the multi-polarization, low frequency UWB SAR system, with the consideration of the low frequency UWB electromagnetic scattering characteristics of the calibrators, the polarimetric calibration method is proposed. The computer simulation is used to validate the method.
Multi-polarization, low frequency Ultra Wide Band Synthetic Aperture Radar (UWB SAR) is one of the most important aspects of the radar technology. The low frequency, UWB and large processing angle result that the polarimetric calibration for regular SAR system cannot be used. In this paper, based on the frequency-domain processing model of the multi-polarization, low frequency UWB SAR system, with the consideration of the low frequency UWB electromagnetic scattering characteristics of the calibrators, the polarimetric calibration method is proposed. The computer simulation is used to validate the method.
2006, 28(7): 1223-1227.
Abstract:
A method, which combines Steered Response Power with PHAse Transform (SRP-PHAT), is a robust speech localization approach with microphone arrays. A relatively precise direction of arrival (DOA) estimation can be achieved by using it in the environment of weak noise and moderate reverberation. However, the localization performance degrades sharply in the environment of low SNR and strong reverberation. Moreover, a real-time localization system is also difficult to be realized due to its heavy computation load. Aiming at these problems, a modified SRP-PHAT localization algorithm is proposed in order to improve the performance of speech localization system. The modified SRP-PHAT algorithm reduces computation load greatly. The results of simulation experiment indicate that the proposed method gives higher localization precision even in an environment of low SNR and strong reverberation.
A method, which combines Steered Response Power with PHAse Transform (SRP-PHAT), is a robust speech localization approach with microphone arrays. A relatively precise direction of arrival (DOA) estimation can be achieved by using it in the environment of weak noise and moderate reverberation. However, the localization performance degrades sharply in the environment of low SNR and strong reverberation. Moreover, a real-time localization system is also difficult to be realized due to its heavy computation load. Aiming at these problems, a modified SRP-PHAT localization algorithm is proposed in order to improve the performance of speech localization system. The modified SRP-PHAT algorithm reduces computation load greatly. The results of simulation experiment indicate that the proposed method gives higher localization precision even in an environment of low SNR and strong reverberation.
2006, 28(7): 1228-1232.
Abstract:
The switched beam antenna is analyzed and its model in system level is presented. Based on analyzing the impact of multi-user detection (MUD) and switched beam antenna on the uplink capacity in TDD-CDMA systems, a novel uplink admission control algorithm is proposed. The theoretical and simulation results show that MUD and the number of antenna element have a great impact on uplink performance. The proposed scheme can provide higher gain for TDD-CDMA if the proper noise rise threshold is set.
The switched beam antenna is analyzed and its model in system level is presented. Based on analyzing the impact of multi-user detection (MUD) and switched beam antenna on the uplink capacity in TDD-CDMA systems, a novel uplink admission control algorithm is proposed. The theoretical and simulation results show that MUD and the number of antenna element have a great impact on uplink performance. The proposed scheme can provide higher gain for TDD-CDMA if the proper noise rise threshold is set.
2006, 28(7): 1233-1237.
Abstract:
A novel method is proposed for digital modulation classification based on Markov chain Monte Carlo (MCMC). Considering the difficulty for Bayesian classifier with unknown residual carrier phase and frequency, marginal likelihood probability density is estimated by Metropolis-Hastings (M-H) algorithm, which kept the theoretical optimality and robustness of Bayesian classifier. The simulated results show that the novel classifier outperforms the one based on cumulants.
A novel method is proposed for digital modulation classification based on Markov chain Monte Carlo (MCMC). Considering the difficulty for Bayesian classifier with unknown residual carrier phase and frequency, marginal likelihood probability density is estimated by Metropolis-Hastings (M-H) algorithm, which kept the theoretical optimality and robustness of Bayesian classifier. The simulated results show that the novel classifier outperforms the one based on cumulants.
2006, 28(7): 1238-1241.
Abstract:
A reduced-complexity all-digital timing tracking scheme suited for multi-carrier CDMA signals is proposed and studied. Based on samples selecting and vector rotation of correlation output vector at only on time channel, timing error detection statistics are approximately acquired and timing adjustment are carried out. Theoretical and numerical results show that the new scheme has an improved performance and remarkable complexity simplicity as compared with the classical digital delay-locked loop.
A reduced-complexity all-digital timing tracking scheme suited for multi-carrier CDMA signals is proposed and studied. Based on samples selecting and vector rotation of correlation output vector at only on time channel, timing error detection statistics are approximately acquired and timing adjustment are carried out. Theoretical and numerical results show that the new scheme has an improved performance and remarkable complexity simplicity as compared with the classical digital delay-locked loop.
2006, 28(7): 1242-1245.
Abstract:
Multiple Access Interference(MAI) is a well-known bottleneck which limits the capacity of CDMA systems, and as is known to all, hybrid ARQ has been widely used in wireless communication systems to support error free high rate data transmission. A combined differentiated MAI control scheme for CDMA networks with hybrid ARQ type-II is proposed in this paper, taking into account that different trials of data packets have different error-correcting capabilities against MAI and largely different quantities. Simulation shows that this method has better delay and throughput performance than traditional MAI control methods.
Multiple Access Interference(MAI) is a well-known bottleneck which limits the capacity of CDMA systems, and as is known to all, hybrid ARQ has been widely used in wireless communication systems to support error free high rate data transmission. A combined differentiated MAI control scheme for CDMA networks with hybrid ARQ type-II is proposed in this paper, taking into account that different trials of data packets have different error-correcting capabilities against MAI and largely different quantities. Simulation shows that this method has better delay and throughput performance than traditional MAI control methods.
2006, 28(7): 1246-1250.
Abstract:
This paper investigates blind space-time interference suppression for MultiCarrier CDMA (MC-CDMA) system in frequency selective Rayleigh fading channel. It is considered that the fading coefficients corresponding to subcarriers are discrete Fourier transform of multipath coefficients. By investigating the code space in frequency domain and the data vector space of the multipath signals, the noise-subspace-based approach is used to perform blind channel estimation. To suppress multiuser access interference (MAI), a Projection-based Auxiliary Vector (PAV) algorithm is proposed. A reconstructed Maximum Ratio Combining (MRC) filtering vector can be evaluated by using the outputs of the last filtering vector. Taking the orthogonal projection of the reconstructed filtering vector onto the space spanned by the basic filtering vector and the previously derived auxiliary vector as an auxiliary vector, a new filtering vector can be formed by linearly combining the last filtering vector and newly generated auxiliary vector. Simulation results show the effectiveness of the proposed algorithms.
This paper investigates blind space-time interference suppression for MultiCarrier CDMA (MC-CDMA) system in frequency selective Rayleigh fading channel. It is considered that the fading coefficients corresponding to subcarriers are discrete Fourier transform of multipath coefficients. By investigating the code space in frequency domain and the data vector space of the multipath signals, the noise-subspace-based approach is used to perform blind channel estimation. To suppress multiuser access interference (MAI), a Projection-based Auxiliary Vector (PAV) algorithm is proposed. A reconstructed Maximum Ratio Combining (MRC) filtering vector can be evaluated by using the outputs of the last filtering vector. Taking the orthogonal projection of the reconstructed filtering vector onto the space spanned by the basic filtering vector and the previously derived auxiliary vector as an auxiliary vector, a new filtering vector can be formed by linearly combining the last filtering vector and newly generated auxiliary vector. Simulation results show the effectiveness of the proposed algorithms.
2006, 28(7): 1251-1254.
Abstract:
In this paper, the performance of Spread spectrum ALOHA Multiple Access (SAMA) system is deeply studied. The general formula of average bit-error-rate for SAMA system is derived, and the expression for calculating throughput and delay of transmission in SAMA system is also presented, and moreover, the performance improvement in throughput and delay when using forward-error-control technique is analyzed. Numerical results show that a significant performance improvement can be gained by using spread spectrum ALOHA other than conventional ALOHA system, and the improvement will be increased with the increasing of processing gain. Consequently, SAMA is very suitable for applications in distributed packet radio networks.
In this paper, the performance of Spread spectrum ALOHA Multiple Access (SAMA) system is deeply studied. The general formula of average bit-error-rate for SAMA system is derived, and the expression for calculating throughput and delay of transmission in SAMA system is also presented, and moreover, the performance improvement in throughput and delay when using forward-error-control technique is analyzed. Numerical results show that a significant performance improvement can be gained by using spread spectrum ALOHA other than conventional ALOHA system, and the improvement will be increased with the increasing of processing gain. Consequently, SAMA is very suitable for applications in distributed packet radio networks.
2006, 28(7): 1255-1257.
Abstract:
In view of the performance of the spreading sequences for spread-spectrum communication system, a novel method of obtaining chaotic digital sequences based on the extended chaotic map is given in this paper. The correlation and balance performances of the new sequences are analysed, furthermore, an advanced method of generating the digital sequences is proposed, in order to get excellent balance performance. The simulation results show that the chaotic spreading sequences generated by the advanced method possess excellent performance and security, specially for CDMA communication system.
In view of the performance of the spreading sequences for spread-spectrum communication system, a novel method of obtaining chaotic digital sequences based on the extended chaotic map is given in this paper. The correlation and balance performances of the new sequences are analysed, furthermore, an advanced method of generating the digital sequences is proposed, in order to get excellent balance performance. The simulation results show that the chaotic spreading sequences generated by the advanced method possess excellent performance and security, specially for CDMA communication system.
2006, 28(7): 1258-1261.
Abstract:
This paper presents the formula of Chrestenson spectrum of m-value composition logical function by using inversion formula, and gives the formula of auto-correlation function of m-value composition logical function. Furthermore, this paper gives some conditions under which m-value composition logical function is separate balanced or correlation-immune, and analyzes the auto-correlation function of m-value composition logical function and its charateristic. Moreover, this paper gets the Chrestenson spectrum formular of nonzero linear combination of several m-value composition logical functions.
This paper presents the formula of Chrestenson spectrum of m-value composition logical function by using inversion formula, and gives the formula of auto-correlation function of m-value composition logical function. Furthermore, this paper gives some conditions under which m-value composition logical function is separate balanced or correlation-immune, and analyzes the auto-correlation function of m-value composition logical function and its charateristic. Moreover, this paper gets the Chrestenson spectrum formular of nonzero linear combination of several m-value composition logical functions.
2006, 28(7): 1262-1265.
Abstract:
This paper proposes hybrid mapping to generate chaotic sequence, by altering initial value periodically. The results show that the properties of the hybrid chaotic sequence are good，and the sequence generator can be easily realized. It is a class of promising pseudo-random sequence in practical applications.
This paper proposes hybrid mapping to generate chaotic sequence, by altering initial value periodically. The results show that the properties of the hybrid chaotic sequence are good，and the sequence generator can be easily realized. It is a class of promising pseudo-random sequence in practical applications.
2006, 28(7): 1266-1269.
Abstract:
Wideband OFDM communications are easily been interfered by narrowband signal. The attenuation is worse in low SNR. Based on Nilssons wideband OFDM system, a relative threshold exciser for narrowband interference is designed here. The choice of relative threshold and the power estimation of noise are investigated under low SNR. To reduce noise interference, the method of channel compensation is modified for noisy environment. Theoretic analysis and simulations show the performance of the system with this relative threshold exciser can keep up with the ideal interference exciser in HF communications under low SNR.
Wideband OFDM communications are easily been interfered by narrowband signal. The attenuation is worse in low SNR. Based on Nilssons wideband OFDM system, a relative threshold exciser for narrowband interference is designed here. The choice of relative threshold and the power estimation of noise are investigated under low SNR. To reduce noise interference, the method of channel compensation is modified for noisy environment. Theoretic analysis and simulations show the performance of the system with this relative threshold exciser can keep up with the ideal interference exciser in HF communications under low SNR.
2006, 28(7): 1270-1273.
Abstract:
Different from MAP, the soft output of SOVA is not the exact a posteriori probability, and few literatures describe SOVA in mathematical form. This paper gives a new comprehensive mathematical expression of SOVA, and deduces two MAP-equivalent SISO decoding methods in the form of SOVA. The first method is just OSA algorithm given by Li et al, (1995)which is suitable for continuous decoding. The other one is the improved version of OSA，whose output is equivalent to that of OSA with the decrease of complexity.
Different from MAP, the soft output of SOVA is not the exact a posteriori probability, and few literatures describe SOVA in mathematical form. This paper gives a new comprehensive mathematical expression of SOVA, and deduces two MAP-equivalent SISO decoding methods in the form of SOVA. The first method is just OSA algorithm given by Li et al, (1995)which is suitable for continuous decoding. The other one is the improved version of OSA，whose output is equivalent to that of OSA with the decrease of complexity.
2006, 28(7): 1274-1278.
Abstract:
Lattice Orthogonal Frequency Division Multiplexing(LOFDM) is a promising technique for high data-rate transmission in double(namely time-frequency) dispersive channel. But, as pulse shaping filters of LOFDM system is badly-localized, it is certainty that ISI and/or ICI be introduced. Therefore, design of pulse shaping filters is an important task for design of optimal LOFDM system. Currently, Strohmer and Beaver(2001, 2003) present an approach to design of pulse shaping filters for optimal LOFDM systems, but, it is computatively complex. In this paper, a generalized Gabor transform is proposed. Utilizing an approach of attained generalized tight Gabor atoms, the time-frequency well-localized pulse shaping filters can be designed for optimal LOFDM system. It is showed through theory analysis and simulative experiment that this method is more efficient and simpler than that of Strohmer and Beaver(2001, 2003).
Lattice Orthogonal Frequency Division Multiplexing(LOFDM) is a promising technique for high data-rate transmission in double(namely time-frequency) dispersive channel. But, as pulse shaping filters of LOFDM system is badly-localized, it is certainty that ISI and/or ICI be introduced. Therefore, design of pulse shaping filters is an important task for design of optimal LOFDM system. Currently, Strohmer and Beaver(2001, 2003) present an approach to design of pulse shaping filters for optimal LOFDM systems, but, it is computatively complex. In this paper, a generalized Gabor transform is proposed. Utilizing an approach of attained generalized tight Gabor atoms, the time-frequency well-localized pulse shaping filters can be designed for optimal LOFDM system. It is showed through theory analysis and simulative experiment that this method is more efficient and simpler than that of Strohmer and Beaver(2001, 2003).
2006, 28(7): 1279-1281.
Abstract:
An efficient power and bit allocation algorithm is proposed for wireless OFDM systems aiming at minimization of the bit error rate under the constraint of total transmit power and data rate. The algorithm is based on the water-filling approach and adopts a new iterative method to improve its stability. Simulation results show the proposed algorithm has a better performance and a lower computational complexity compared to the previous ones.
An efficient power and bit allocation algorithm is proposed for wireless OFDM systems aiming at minimization of the bit error rate under the constraint of total transmit power and data rate. The algorithm is based on the water-filling approach and adopts a new iterative method to improve its stability. Simulation results show the proposed algorithm has a better performance and a lower computational complexity compared to the previous ones.
2006, 28(7): 1282-1286.
Abstract:
This paper presents a prediction model of frequency parameters of short-wave communication based on Adaptive Neural Fuzzy Inference System(ANFIS). The system parameters of the model are adjusted by delaminating-adaptation genetic algorithm. The model is simulated and compared with other nonlinear methods. The model shows some standout excellences, such as higher precision of prediction, faster speed of convergence, better across-the-board astringency and intelligence of adjusting system parameters.
This paper presents a prediction model of frequency parameters of short-wave communication based on Adaptive Neural Fuzzy Inference System(ANFIS). The system parameters of the model are adjusted by delaminating-adaptation genetic algorithm. The model is simulated and compared with other nonlinear methods. The model shows some standout excellences, such as higher precision of prediction, faster speed of convergence, better across-the-board astringency and intelligence of adjusting system parameters.
2006, 28(7): 1287-1290.
Abstract:
An algorithm for the blind estimation of uplink OFDMA synchronization parameters is introduced in this article. The algorithm exploits the second-order cyclostationarity of the received signal to estimate the frequency offset and time delay，in the different tone assignment schemes. The performance of high resolution and immune to the effect of noise and interference is evaluated through simulation results.
An algorithm for the blind estimation of uplink OFDMA synchronization parameters is introduced in this article. The algorithm exploits the second-order cyclostationarity of the received signal to estimate the frequency offset and time delay，in the different tone assignment schemes. The performance of high resolution and immune to the effect of noise and interference is evaluated through simulation results.
2006, 28(7): 1291-1294.
Abstract:
A new blind symbol timing-tracking algorithm is proposed, using the special OFDM frame structure with cyclic prefix and cyclic postfix. Analysis and simulation results show that the mean square error of timing offset estimation for proposed method is superior to that of Maximum Likelihood (ML) method.
A new blind symbol timing-tracking algorithm is proposed, using the special OFDM frame structure with cyclic prefix and cyclic postfix. Analysis and simulation results show that the mean square error of timing offset estimation for proposed method is superior to that of Maximum Likelihood (ML) method.
2006, 28(7): 1295-1297.
Abstract:
In this paper, a subspace-based detection method is proposed for analog space-time codes wedded with ultra-wideband (UWB) transmissions. Without estimating the channels at the receiver, the proposed algorithm yields the estimation of transmitted symbols by minimizing some quadratic form built on the orthogonality between signal and noise subspaces. Simulations in flat-faded application scenarios show that, the subspace method can achieve the same diversity order with the coherent reception, and outperforms the noncoherent decoder in existence with multiple successive space-time codes being decoded jointly.
In this paper, a subspace-based detection method is proposed for analog space-time codes wedded with ultra-wideband (UWB) transmissions. Without estimating the channels at the receiver, the proposed algorithm yields the estimation of transmitted symbols by minimizing some quadratic form built on the orthogonality between signal and noise subspaces. Simulations in flat-faded application scenarios show that, the subspace method can achieve the same diversity order with the coherent reception, and outperforms the noncoherent decoder in existence with multiple successive space-time codes being decoded jointly.
2006, 28(7): 1298-1302.
Abstract:
In mobile Ad hoc networks, the topology is dynamic, the energy of node is always limited, and there are always asymmetric links between nodes. This paper presents an Energy-Aware Multipath Routing Algorithm(EAMRA) which intends to prolong the TTL(Time-To-Live) of this kind of mobile Ad hoc networks. EAMRA is a connection-oriented and reactive path-pool-based routing algorithm which chooses randomly the routing for user data according to path metrics. The path metrics, reliability and residual-energy, are updated in communication process. The simulation results show that EAMRA can effectively prolong the TTL of mobile Ad hoc networks.
In mobile Ad hoc networks, the topology is dynamic, the energy of node is always limited, and there are always asymmetric links between nodes. This paper presents an Energy-Aware Multipath Routing Algorithm(EAMRA) which intends to prolong the TTL(Time-To-Live) of this kind of mobile Ad hoc networks. EAMRA is a connection-oriented and reactive path-pool-based routing algorithm which chooses randomly the routing for user data according to path metrics. The path metrics, reliability and residual-energy, are updated in communication process. The simulation results show that EAMRA can effectively prolong the TTL of mobile Ad hoc networks.
2006, 28(7): 1303-1307.
Abstract:
In this paper, an alternative AQM(Active Queue Management) is designed: WDSE (Wavelet-Decomposed Signal Energy) approach is capable of detecting and managing self-similar traffic. This approach uses wavelets and measures the energy of input traffic at the output of each dyadic subband filter. The scheme is based on the wavelet multiresolution analysis, which can be used to predict short and long term fluctuations in the incoming traffic pattern and readjust the marking drop probabilities without the difficulty of parameters selection in advance unlike RED. Comparing the WDSE and RED about the dynamic performance, improved transient performance of WDSE is illustrate. As evident from the simulation, the WDSE performs better, responding more quickly to load variations than the RED. Moreover, the WDSE is superior in robustly regulating the steady-state value of the queue level.
In this paper, an alternative AQM(Active Queue Management) is designed: WDSE (Wavelet-Decomposed Signal Energy) approach is capable of detecting and managing self-similar traffic. This approach uses wavelets and measures the energy of input traffic at the output of each dyadic subband filter. The scheme is based on the wavelet multiresolution analysis, which can be used to predict short and long term fluctuations in the incoming traffic pattern and readjust the marking drop probabilities without the difficulty of parameters selection in advance unlike RED. Comparing the WDSE and RED about the dynamic performance, improved transient performance of WDSE is illustrate. As evident from the simulation, the WDSE performs better, responding more quickly to load variations than the RED. Moreover, the WDSE is superior in robustly regulating the steady-state value of the queue level.
2006, 28(7): 1308-1311.
Abstract:
A secure threshold proxy signature scheme is proposed aiming at conspiracy attack, that is, any t (t is threshold value) or more malicious proxy signatures may work together to reconstruct the secret polynomial of the proxy group and derive the secret keys of other members in the proxy group, consequently they can impersonate some other proxy signers to generate a valid threshold proxy signature. The new scheme can not only satisfy the properties of the threshold proxy signature, but also withstand the conspiracy attack. Furthermore, the proxy signers proxy signing capability can be revoked if the original signer needs.
A secure threshold proxy signature scheme is proposed aiming at conspiracy attack, that is, any t (t is threshold value) or more malicious proxy signatures may work together to reconstruct the secret polynomial of the proxy group and derive the secret keys of other members in the proxy group, consequently they can impersonate some other proxy signers to generate a valid threshold proxy signature. The new scheme can not only satisfy the properties of the threshold proxy signature, but also withstand the conspiracy attack. Furthermore, the proxy signers proxy signing capability can be revoked if the original signer needs.
2006, 28(7): 1312-1316.
Abstract:
The distributed decryption scheme for simple addition stream ciphers proposed by Magnus berg is analyzed. Its main disadvantages, i.e. the operations of encryption and decryption are implemented in different finite fields, and the orders of the two fields must be primes satisfying a certain relation, are pointed out. A new distributed decryption scheme for word-oriented stream ciphers is presented. Compared with Magnus bergs scheme, the proposed scheme has two main advantages. Firstly, in the new scheme, the encryption and decryption operations are implemented in the same finite field, and the size of the field is not required to be a prime. Secondly, the security and efficiency of the new scheme are greatly improved. For applications, the new scheme can be applied in the protection of data confidentiality in a database, distributed key management in Ad-hoc networks, etc.
The distributed decryption scheme for simple addition stream ciphers proposed by Magnus berg is analyzed. Its main disadvantages, i.e. the operations of encryption and decryption are implemented in different finite fields, and the orders of the two fields must be primes satisfying a certain relation, are pointed out. A new distributed decryption scheme for word-oriented stream ciphers is presented. Compared with Magnus bergs scheme, the proposed scheme has two main advantages. Firstly, in the new scheme, the encryption and decryption operations are implemented in the same finite field, and the size of the field is not required to be a prime. Secondly, the security and efficiency of the new scheme are greatly improved. For applications, the new scheme can be applied in the protection of data confidentiality in a database, distributed key management in Ad-hoc networks, etc.
2006, 28(7): 1317-1321.
Abstract:
An LSP extension mechanism is proposed to decrease the signaling overhead and handoff delay and to eliminate the packet loss in MPLS based mobile IP networks. For the LSP extension mechanism, some loops may exist in extended LSP, and the criterion used for breaking down the extended LSP is not proposed. Aiming to these problems, this paper firstly gives a method to avoid forming loops in extended LSP. Then, a criterion, i.e. user information cost function and signal information cost function, are defined to breaking down the extended LSP, and the analysis is provided to calculate these cost functions. How to utilize the cost functions to break down the extended LSP is also discussed. The performance evaluation results denote that overhead of LSP extension mechanism can be decreased by breaking down the extended LSP according to the proposed criterion.
An LSP extension mechanism is proposed to decrease the signaling overhead and handoff delay and to eliminate the packet loss in MPLS based mobile IP networks. For the LSP extension mechanism, some loops may exist in extended LSP, and the criterion used for breaking down the extended LSP is not proposed. Aiming to these problems, this paper firstly gives a method to avoid forming loops in extended LSP. Then, a criterion, i.e. user information cost function and signal information cost function, are defined to breaking down the extended LSP, and the analysis is provided to calculate these cost functions. How to utilize the cost functions to break down the extended LSP is also discussed. The performance evaluation results denote that overhead of LSP extension mechanism can be decreased by breaking down the extended LSP according to the proposed criterion.
2006, 28(7): 1322-1326.
Abstract:
This paper proposes a new method of knowledge discovery based on the structured covering algorithm. Since the network of covering domains is constructed through a special method, it makes each covering domain a valuable pattern. Through analyzing the samples covered by the covering domain, certain valuable pattern will be found, which includes clustering information of samples, association rules among the data, the outlier analysis, etc. And in order to meet different requirement of users, different covering networks can be structured, therefore, multi-sides of data can be analysed. The experiments show that using the covering algorithm to discover knowledge of data is effective and feasible.
This paper proposes a new method of knowledge discovery based on the structured covering algorithm. Since the network of covering domains is constructed through a special method, it makes each covering domain a valuable pattern. Through analyzing the samples covered by the covering domain, certain valuable pattern will be found, which includes clustering information of samples, association rules among the data, the outlier analysis, etc. And in order to meet different requirement of users, different covering networks can be structured, therefore, multi-sides of data can be analysed. The experiments show that using the covering algorithm to discover knowledge of data is effective and feasible.
2006, 28(7): 1327-1330.
Abstract:
Attention is focused on a new method to reduce the numerical dispersion of the 3-D Alternating-Direction Implicit Finite-Difference Time-Domain(ADI-FDTD) method through artificial anisotropy. As the wave propagation can be speeded up by introducing proper anisotropy parameters into the 3-D ADI-FDTD method, the numerical dispersion can be reduced and the accuracy can be improved significantly. First, the numerical formulations of the 3-D ADI-FDTD method are modified. Secondly, the new numerical dispersion relation is derived. And consequently the relative permittivity tensor of artificial anisotropy can be obtained. In order to demonstrate the accuracy and efficiency of this new method, a hollow waveguide and a waveguide with discontinuous structure are simulated as examples. In addition the reduction of numerical dispersion is investigated as a function of the relative permittivity tensor of artificial anisotropy. Furthermore, the numerical results and the computational requirements of the proposed method are compared with those of the conventional 3-D ADI-FDTD method. It is found that this new method is accurate and efficient.
Attention is focused on a new method to reduce the numerical dispersion of the 3-D Alternating-Direction Implicit Finite-Difference Time-Domain(ADI-FDTD) method through artificial anisotropy. As the wave propagation can be speeded up by introducing proper anisotropy parameters into the 3-D ADI-FDTD method, the numerical dispersion can be reduced and the accuracy can be improved significantly. First, the numerical formulations of the 3-D ADI-FDTD method are modified. Secondly, the new numerical dispersion relation is derived. And consequently the relative permittivity tensor of artificial anisotropy can be obtained. In order to demonstrate the accuracy and efficiency of this new method, a hollow waveguide and a waveguide with discontinuous structure are simulated as examples. In addition the reduction of numerical dispersion is investigated as a function of the relative permittivity tensor of artificial anisotropy. Furthermore, the numerical results and the computational requirements of the proposed method are compared with those of the conventional 3-D ADI-FDTD method. It is found that this new method is accurate and efficient.
2006, 28(7): 1331-1334.
Abstract:
In this paper, a method of active filter design based on Programmable Operational Transconductance Amplifiers(POTA) is given. The transconductance is adjusted by software in order to improve accuracy. The design procedure is based on Jacobi method and similar diagonal matrix. The difficulties of finding the roots of high order polynomial can be avoided by using Jacobi method. Active filter circuit is composed of POTA and ground capacitors. It has the characteristics of high stability and low sensitivities. A design example is given and the simulated results show that the given method is suitable for continuous time active filter design.
In this paper, a method of active filter design based on Programmable Operational Transconductance Amplifiers(POTA) is given. The transconductance is adjusted by software in order to improve accuracy. The design procedure is based on Jacobi method and similar diagonal matrix. The difficulties of finding the roots of high order polynomial can be avoided by using Jacobi method. Active filter circuit is composed of POTA and ground capacitors. It has the characteristics of high stability and low sensitivities. A design example is given and the simulated results show that the given method is suitable for continuous time active filter design.
2006, 28(7): 1335-1339.
Abstract:
This paper presents a new circuit to tune Gm value of transconductor accurately which employs switched-capacitor technique to change the bias current of transconductor. A third order elliptical function lowpass filter with accurate tunable frequency is designed using transconductor that is not only with voltage common-mode negative feedback, but also with varying bias-triode transistors to improve the linearity of this circuit. Simulated results show that the practical frequency response of the filter is very near to that of idealized circumstance by applying TSMC 2-poly 4-metal 3.3V power supply 0.35m CMOS technology Spice model.
This paper presents a new circuit to tune Gm value of transconductor accurately which employs switched-capacitor technique to change the bias current of transconductor. A third order elliptical function lowpass filter with accurate tunable frequency is designed using transconductor that is not only with voltage common-mode negative feedback, but also with varying bias-triode transistors to improve the linearity of this circuit. Simulated results show that the practical frequency response of the filter is very near to that of idealized circumstance by applying TSMC 2-poly 4-metal 3.3V power supply 0.35m CMOS technology Spice model.
2006, 28(7): 1340-1344.
Abstract:
This paper presents an analog circuit data array description method and circuit-constructing rules that coordinately work with description language. With the prerequisite of no invalid circuit structure, circuit-constructing rules create high quality op-amp circuit structure. This new technique, starting from classic sub-circuit model, automatically creating op-amp circuit, guarantees the quality of circuit construction. Results are reported to validate the effectiveness of this approach for construction-design automation of op-amp circuit.
This paper presents an analog circuit data array description method and circuit-constructing rules that coordinately work with description language. With the prerequisite of no invalid circuit structure, circuit-constructing rules create high quality op-amp circuit structure. This new technique, starting from classic sub-circuit model, automatically creating op-amp circuit, guarantees the quality of circuit construction. Results are reported to validate the effectiveness of this approach for construction-design automation of op-amp circuit.
