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2009 Vol. 31, No. 9
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2009, 31(9): 2033-2038.
doi: 10.3724/SP.J.1146.2008.01239
Abstract:
According to the character of Passive Radar based on DTTB illuminator, spatial filtering is used to suppress the direct-path interference. The adaptive beamforming algorithms combined with broad null are adopted in echo receiving channel. To reference channel, the improved structure of general sidelobe canceller to realize the adaptive beamformer is used, simultaneity which is combined with the broad null algorithm. The simulations based on the DTTB signal show applying the proposed method has better the performance of target detection.
According to the character of Passive Radar based on DTTB illuminator, spatial filtering is used to suppress the direct-path interference. The adaptive beamforming algorithms combined with broad null are adopted in echo receiving channel. To reference channel, the improved structure of general sidelobe canceller to realize the adaptive beamformer is used, simultaneity which is combined with the broad null algorithm. The simulations based on the DTTB signal show applying the proposed method has better the performance of target detection.
2009, 31(9): 2039-2043.
doi: 10.3724/SP.J.1146.2008.01557
Abstract:
Research of asymmetric spaceborne-airborne bistatic SAR imaging algorithm is one of difficult issues in field of bistatic SAR. In this paper, a fast numerical Range Migration Algorithm (RMA) is proposed for GPS signal based continuous wave spaceborne-airborne bistatic SAR. A two dimentional precise analytic expression in frequency domain of system response signal is deduced by using approach of instantaneous Doppler wavenumber, and the match function and interpolation function of the proposed algorithm can be obtained numerically. The proposed algorithm has the characteristics of fast speed and high precision of RMA. In addition, it also has the same wide application range compared with Back Projection (BP) algorithm.
Research of asymmetric spaceborne-airborne bistatic SAR imaging algorithm is one of difficult issues in field of bistatic SAR. In this paper, a fast numerical Range Migration Algorithm (RMA) is proposed for GPS signal based continuous wave spaceborne-airborne bistatic SAR. A two dimentional precise analytic expression in frequency domain of system response signal is deduced by using approach of instantaneous Doppler wavenumber, and the match function and interpolation function of the proposed algorithm can be obtained numerically. The proposed algorithm has the characteristics of fast speed and high precision of RMA. In addition, it also has the same wide application range compared with Back Projection (BP) algorithm.
2009, 31(9): 2044-2047.
doi: 10.3724/SP.J.1146.2008.01230
Abstract:
This paper focuses on the translation-invariant bistatic SAR Doppler ambiguity resolving by using Single-Transmitter-Multiply-Receivers (STMR) mounted on different platforms. The range dependent Doppler in the bistatic configuration is analyzed, based on which a bistatic Doppler ambiguity suppression algorithm is proposed. The approach obtains the range dependent steering vectors of ambiguous signal components in the same Doppler bins by numerical calculation, and the spatial domain filtering is used to reconstruct the full bandwidth Doppler spectrum. Finally, the available bistatic imaging algorithms can be used to obtain the wide swath and high resolution SAR image. Simulation confirms the validity of the approach.
This paper focuses on the translation-invariant bistatic SAR Doppler ambiguity resolving by using Single-Transmitter-Multiply-Receivers (STMR) mounted on different platforms. The range dependent Doppler in the bistatic configuration is analyzed, based on which a bistatic Doppler ambiguity suppression algorithm is proposed. The approach obtains the range dependent steering vectors of ambiguous signal components in the same Doppler bins by numerical calculation, and the spatial domain filtering is used to reconstruct the full bandwidth Doppler spectrum. Finally, the available bistatic imaging algorithms can be used to obtain the wide swath and high resolution SAR image. Simulation confirms the validity of the approach.
2009, 31(9): 2048-2052.
doi: 10.3724/SP.J.1146.2008.00808
Abstract:
The signal model of MCF-MIMO (Multi-Carrier-Frequency MIMO) Radar are constructed first in this paper. Then an equivalent array with NtNr antennas is formed after the signal preprocessing, where Nt and Nr are respectively the transmitted and received antenna number, and the equivalent steering vector is the kronecker product of transmitted steering vector and received steering vector in the case of narrow band signal. And it is proposed to adopt the Spatial-Temporal MUSIC (MUltiple SIgnal Characterization) method to realize the super resolution of range and angle based on the above characteristics and to improve the estimating precision of range and angle when there are many targets. The Cramer-Rao bound of range and angle estimation are derived and also the variation of estimation variance of range and angle with Signal to Noise Ratio (SNR), snap number and direction of arrival are studied and simulated. Finally the simulation results of multi-dimensional spatial-temporal super resolution algorithm with planar array are presented and they validate the application of the algorithm in the case of planar array and multi-dimensional.
The signal model of MCF-MIMO (Multi-Carrier-Frequency MIMO) Radar are constructed first in this paper. Then an equivalent array with NtNr antennas is formed after the signal preprocessing, where Nt and Nr are respectively the transmitted and received antenna number, and the equivalent steering vector is the kronecker product of transmitted steering vector and received steering vector in the case of narrow band signal. And it is proposed to adopt the Spatial-Temporal MUSIC (MUltiple SIgnal Characterization) method to realize the super resolution of range and angle based on the above characteristics and to improve the estimating precision of range and angle when there are many targets. The Cramer-Rao bound of range and angle estimation are derived and also the variation of estimation variance of range and angle with Signal to Noise Ratio (SNR), snap number and direction of arrival are studied and simulated. Finally the simulation results of multi-dimensional spatial-temporal super resolution algorithm with planar array are presented and they validate the application of the algorithm in the case of planar array and multi-dimensional.
2009, 31(9): 2053-2058.
doi: 10.3724/SP.J.1146.2008.00639
Abstract:
The go-stop assumption applied to the conventional SAR can not be used in the SAR system using step frequency waveforms. For the reason that the time spent on the coherent processing is too long. Accordingly the fast-time Doppler effect induced by the movement of the radar platform can not be neglected as usual. In this paper, a new wavenumber domain based on fast-time Doppler effect compensation method is proposed. This new method is implemented through 2D-FFT and 2D-IFFT.Comparing with the time domain compensation method, the new method has almost the same compensation precision but with less processing time, which is more beneficial to the real-time compensation in the practical step-frequency SAR system.
The go-stop assumption applied to the conventional SAR can not be used in the SAR system using step frequency waveforms. For the reason that the time spent on the coherent processing is too long. Accordingly the fast-time Doppler effect induced by the movement of the radar platform can not be neglected as usual. In this paper, a new wavenumber domain based on fast-time Doppler effect compensation method is proposed. This new method is implemented through 2D-FFT and 2D-IFFT.Comparing with the time domain compensation method, the new method has almost the same compensation precision but with less processing time, which is more beneficial to the real-time compensation in the practical step-frequency SAR system.
2009, 31(9): 2059-2064.
doi: 10.3724/SP.J.1146.2008.00892
Abstract:
Two new methods to compensate clutter range dependence for bistatic airborne radar are proposed in this paper. These methods are called DBU (Derivative Based Updating). The receiving slope distance and receiving elevation angle cosine in the direction of the main lobe of beam pattern are respectively utilized as updating parameter. The methods can mitigate the clutter range dependence, and improve the performance of Space-Time Adaptive Processing (STAP) in Ground Moving Target Indication (GMTI). The results of computer simulation show the effectiveness of the methods.
Two new methods to compensate clutter range dependence for bistatic airborne radar are proposed in this paper. These methods are called DBU (Derivative Based Updating). The receiving slope distance and receiving elevation angle cosine in the direction of the main lobe of beam pattern are respectively utilized as updating parameter. The methods can mitigate the clutter range dependence, and improve the performance of Space-Time Adaptive Processing (STAP) in Ground Moving Target Indication (GMTI). The results of computer simulation show the effectiveness of the methods.
2009, 31(9): 2065-2068.
doi: 10.3724/SP.J.1146.2008.01289
Abstract:
The novelty of MIMO radar is to improve the performance of radar utilizing spatial diversity and waveform diversity. To achieve full diversity, this paper considers the problem of spatio-temporal signal design for MIMO radar based on channel estimation with the clutter statistical properties known. The method obtains the optimized spatio-temporal signal though minimizing the mean-square error of the channels linear Bayes estimation. It shows that the optimized spatio-temporal signal is a function of the clutter covariance matrix, which is verified from information theoretical point of view. Finally the simulation results show that the optimized spatio-temporal signal improves the target detection performance.
The novelty of MIMO radar is to improve the performance of radar utilizing spatial diversity and waveform diversity. To achieve full diversity, this paper considers the problem of spatio-temporal signal design for MIMO radar based on channel estimation with the clutter statistical properties known. The method obtains the optimized spatio-temporal signal though minimizing the mean-square error of the channels linear Bayes estimation. It shows that the optimized spatio-temporal signal is a function of the clutter covariance matrix, which is verified from information theoretical point of view. Finally the simulation results show that the optimized spatio-temporal signal improves the target detection performance.
2009, 31(9): 2069-2073.
doi: 10.3724/SP.J.1146.2008.01203
Abstract:
Spinning-rate estimate is the base of rapidly spinning target imaging. A new spinning-rate estimating method is proposed in this paper. Base on the characteristic of rapidly spinning target in the range-time image, a primary estimate using Fourier transform is put forward. And it is refined in specified range by calculating the entropy of the whole image, which is independent of single scatter point. Simulations with synthetic data demonstrate the performance of the new method. The results confirm its effectiveness.
Spinning-rate estimate is the base of rapidly spinning target imaging. A new spinning-rate estimating method is proposed in this paper. Base on the characteristic of rapidly spinning target in the range-time image, a primary estimate using Fourier transform is put forward. And it is refined in specified range by calculating the entropy of the whole image, which is independent of single scatter point. Simulations with synthetic data demonstrate the performance of the new method. The results confirm its effectiveness.
2009, 31(9): 2074-2078.
doi: 10.3724/SP.J.1146.2009.00080
Abstract:
Double threshold detection based on constraint judgment is proposed for weak signal detection. The improvement effect on Probability of False Alarm (PFA) and influence on Probability of Detection (PD) are quantitatively analyzed with constraint judgment. The mathematical models of total PFA and PD of double threshold detection based on constraint judgment are built, and the validity of the mathematical models is verified by simulation tests. The simulation results show that the signal-to-noise ratio under scheduled PFA and PD can be decreased by introducing constraint judgment to double threshold detection.
Double threshold detection based on constraint judgment is proposed for weak signal detection. The improvement effect on Probability of False Alarm (PFA) and influence on Probability of Detection (PD) are quantitatively analyzed with constraint judgment. The mathematical models of total PFA and PD of double threshold detection based on constraint judgment are built, and the validity of the mathematical models is verified by simulation tests. The simulation results show that the signal-to-noise ratio under scheduled PFA and PD can be decreased by introducing constraint judgment to double threshold detection.
2009, 31(9): 2079-2083.
doi: 10.3724/SP.J.1146.2008.01222
Abstract:
To deal with the parameter uncertainty in emitter recognition problem, this paper presents a viable recognition method based on cloud model. First, for getting the degree of membership of the measurement parameter, it applies this theory to model the interval type parameters in template database with normal cloud model. Then it uses the characteristic of the transformation between qualitative concepts and their quantitative expression to describe the matching degree of the discrete parameters. At the same time, a new method of determining weight coefficients is proposed, by which the coefficient can be adjusted dynamically. Simulation results show that the method is applicable and effective.
To deal with the parameter uncertainty in emitter recognition problem, this paper presents a viable recognition method based on cloud model. First, for getting the degree of membership of the measurement parameter, it applies this theory to model the interval type parameters in template database with normal cloud model. Then it uses the characteristic of the transformation between qualitative concepts and their quantitative expression to describe the matching degree of the discrete parameters. At the same time, a new method of determining weight coefficients is proposed, by which the coefficient can be adjusted dynamically. Simulation results show that the method is applicable and effective.
2009, 31(9): 2084-2087.
doi: 10.3724/SP.J.1146.2008.01279
Abstract:
This paper de-noises in image by diffusion filter. And a method of finding optimal stopping time is proposed. The criterion of stopping time is that the variance of image smoothed out is bigger than the variance of noise smoothed out. In order to estimate the variance of noise in iteration correctly, a pure synthesis noise as an image is synchronously iterated with the observation image in iteration, and the variance of pure noise image is taken as the estimation of the variance of noise in estimated image. According to the anisotropy of the regularization, a novel regularization term that can ensure the synchronous changing of the synthesis noise and real noise was proposed in this article. The new regularization term is put into use only in iteration of pure noise image, and the similarity of statistical properties between real noise and synthesis noise can be kept in iteration. Experiment confirms the effectiveness of proposed method to select optimal stopping time.
This paper de-noises in image by diffusion filter. And a method of finding optimal stopping time is proposed. The criterion of stopping time is that the variance of image smoothed out is bigger than the variance of noise smoothed out. In order to estimate the variance of noise in iteration correctly, a pure synthesis noise as an image is synchronously iterated with the observation image in iteration, and the variance of pure noise image is taken as the estimation of the variance of noise in estimated image. According to the anisotropy of the regularization, a novel regularization term that can ensure the synchronous changing of the synthesis noise and real noise was proposed in this article. The new regularization term is put into use only in iteration of pure noise image, and the similarity of statistical properties between real noise and synthesis noise can be kept in iteration. Experiment confirms the effectiveness of proposed method to select optimal stopping time.
2009, 31(9): 2088-2092.
doi: 10.3724/SP.J.1146.2008.00774
Abstract:
To solve the problem of the passive tracking of the space objects with perturbation in space-based optical surveillance, the hybrid coordinates SPKF method is put forward. The Unscented Transformation (UT) and hybrid coordinates are introduced to avoid the influence of the linearization error and enhance the robustness of the tracking filter. The state prediction is performed in Cartesian coordinates utilizing UT and the perturbation influence could be considered at the same time, then the filter updating procedure is performed in modified sphere coordinates. Simulation results indicate that this approach has more advantage on rapidity of convergence and stability under the condition of the dense or sparse measurements.
To solve the problem of the passive tracking of the space objects with perturbation in space-based optical surveillance, the hybrid coordinates SPKF method is put forward. The Unscented Transformation (UT) and hybrid coordinates are introduced to avoid the influence of the linearization error and enhance the robustness of the tracking filter. The state prediction is performed in Cartesian coordinates utilizing UT and the perturbation influence could be considered at the same time, then the filter updating procedure is performed in modified sphere coordinates. Simulation results indicate that this approach has more advantage on rapidity of convergence and stability under the condition of the dense or sparse measurements.
2009, 31(9): 2093-2098.
doi: 10.3724/SP.J.1146.2008.01106
Abstract:
A method of analyzing the lightning pulse interference into the carbon fiber cabin in airplane is developed based on FDTD. The lightning channel is equivalent to be a linear antenna which is vertical on the conductor ground. Therefore the conception of antenna field partition is used to compartmentalize the lightning field. A plane-wave source can be set up beside cabin with FDTD to analyze far-field effect of lightning field. In near field region a segment of filamentary current which is extended into the Perfectly Matched Layer (PML) reaching the Perfectly Electric Conductor (PEC) boundary outside the PML is set up beside cabin to simulate a part of lightning channel using FDTD. This method avoids the charge effect at the two end-points of the linear current. The FDTD results are accurate compared with analytic results. And then the electric field in the cabin of airplane is calculated in near and far field region using this method, providing the warranty for electromagnetic compatibility design of the carbon fiber cabin.
A method of analyzing the lightning pulse interference into the carbon fiber cabin in airplane is developed based on FDTD. The lightning channel is equivalent to be a linear antenna which is vertical on the conductor ground. Therefore the conception of antenna field partition is used to compartmentalize the lightning field. A plane-wave source can be set up beside cabin with FDTD to analyze far-field effect of lightning field. In near field region a segment of filamentary current which is extended into the Perfectly Matched Layer (PML) reaching the Perfectly Electric Conductor (PEC) boundary outside the PML is set up beside cabin to simulate a part of lightning channel using FDTD. This method avoids the charge effect at the two end-points of the linear current. The FDTD results are accurate compared with analytic results. And then the electric field in the cabin of airplane is calculated in near and far field region using this method, providing the warranty for electromagnetic compatibility design of the carbon fiber cabin.
2009, 31(9): 2099-2103.
doi: 10.3724/SP.J.1146.2008.00539
Abstract:
Using the principle of minimum variance, this paper computes the optimal weight coefficients for the phase estimation algorithm of the multi-frequencies signal, which is based on the phase weighted average of the partitions windowed-DFT. The variance formula of the estimator is derived. In addition, the issue of the DFT noise sensitive frequency region is precisely analyzed. Simulation results show the effectiveness of the algorithm and the rightness of the analysis.
Using the principle of minimum variance, this paper computes the optimal weight coefficients for the phase estimation algorithm of the multi-frequencies signal, which is based on the phase weighted average of the partitions windowed-DFT. The variance formula of the estimator is derived. In addition, the issue of the DFT noise sensitive frequency region is precisely analyzed. Simulation results show the effectiveness of the algorithm and the rightness of the analysis.
2009, 31(9): 2104-2108.
doi: 10.3724/SP.J.1146.2008.01253
Abstract:
This paper defines analogy measure of two random variables, and discusses the principle and algorithm of maximizing non-Gaussianity of observed data with a linear transformation to estimate independent components serially. It also proves the non-polynomial moment theorem by a generalized way, and states the feasibility that substitutes the analogy with the expectation of a non-quadratic smooth even function based on the theorem. A formula to compute sign of above algorithm is given. The algorithm overcomes the contradiction between the objective function and the sign computation formula.Comparing with Maximum likelihood ICA, the analogy is Maximum likelihood function of single source under pre-whited.
This paper defines analogy measure of two random variables, and discusses the principle and algorithm of maximizing non-Gaussianity of observed data with a linear transformation to estimate independent components serially. It also proves the non-polynomial moment theorem by a generalized way, and states the feasibility that substitutes the analogy with the expectation of a non-quadratic smooth even function based on the theorem. A formula to compute sign of above algorithm is given. The algorithm overcomes the contradiction between the objective function and the sign computation formula.Comparing with Maximum likelihood ICA, the analogy is Maximum likelihood function of single source under pre-whited.
2009, 31(9): 2109-2112.
doi: 10.3724/SP.J.1146.2008.00800
Abstract:
This paper introduces a steering-invariant constant beamwidth beamforming algorithm with Second-Order Cone Programming (SOCP) constraints. The optimizing criterion of the proposed algorithm is suppressing the designed sidelobe level utmost while keeping the mean-squared error between the designed mainlobe and the corresponding reference mainlobe on all look directions minimizing. The constrained optimizing formula can be reformed to a standard SOCP fashion and be solved with SeDuMi, an optimization toolbox. It is shown with simulation that the proposed algorithm can obtain the steering-invariant constant beamwidth beampattern effectively under the designed main-lobe direction of 60.
This paper introduces a steering-invariant constant beamwidth beamforming algorithm with Second-Order Cone Programming (SOCP) constraints. The optimizing criterion of the proposed algorithm is suppressing the designed sidelobe level utmost while keeping the mean-squared error between the designed mainlobe and the corresponding reference mainlobe on all look directions minimizing. The constrained optimizing formula can be reformed to a standard SOCP fashion and be solved with SeDuMi, an optimization toolbox. It is shown with simulation that the proposed algorithm can obtain the steering-invariant constant beamwidth beampattern effectively under the designed main-lobe direction of 60.
2009, 31(9): 2113-2117.
doi: 10.3724/SP.J.1146.2008.01051
Abstract:
A basic model is established for mixtures of two co-frequency modulated signals with error-control codes, then an M-PSP based algorithm is proposed to exploit the error-control codes in its single-channel blind separation, with special emphasis on the construction of state trellis, the evaluation of branch metric and the tracking of channel responses. Simulation results show that the proposed algorithm is superior to the algorithms which bypass the error-control codes. For BPSK signals with rate-1/2 convolutional codes, a gain of about 2 dB in signal-noise ratio can be obtained at a bit error rate of 10-4.
A basic model is established for mixtures of two co-frequency modulated signals with error-control codes, then an M-PSP based algorithm is proposed to exploit the error-control codes in its single-channel blind separation, with special emphasis on the construction of state trellis, the evaluation of branch metric and the tracking of channel responses. Simulation results show that the proposed algorithm is superior to the algorithms which bypass the error-control codes. For BPSK signals with rate-1/2 convolutional codes, a gain of about 2 dB in signal-noise ratio can be obtained at a bit error rate of 10-4.
2009, 31(9): 2118-2122.
doi: 10.3724/SP.J.1146.2008.01269
Abstract:
A novel intelligent DOA estimation technique for broadband signals is proposed, which transfer the problem of DOA estimation into a large mount of data intelligent learning and recognition problem. The upper triangular half of the correlation matrix of knowing direction signals is extracted to form training set. This paper used region direction detection neural network and DOA estimation neural networks to estimate DOA for unknown signal. The main advantage of this new approach is dramatic reduction the size and complex of the training set required for each smaller neural network. The specific steps are presented. The simulation results show the DOA estimation technique for broadband signals has very high precision, and effectiveness for future application.
A novel intelligent DOA estimation technique for broadband signals is proposed, which transfer the problem of DOA estimation into a large mount of data intelligent learning and recognition problem. The upper triangular half of the correlation matrix of knowing direction signals is extracted to form training set. This paper used region direction detection neural network and DOA estimation neural networks to estimate DOA for unknown signal. The main advantage of this new approach is dramatic reduction the size and complex of the training set required for each smaller neural network. The specific steps are presented. The simulation results show the DOA estimation technique for broadband signals has very high precision, and effectiveness for future application.
2009, 31(9): 2123-2131.
doi: 10.3724/SP.J.1146.2008.00857
Abstract:
Asynchronous fusion is common in processing multisensor data fusion problems and the asynchronous track fusion which adopts distributed fusion architecture has an extensive application among asynchronous fusion. In current asynchronous track fusion algorithms, the global feedback is mostly not established from fusion center to local sensors, so the local estimate can not be improved by the global estimate. Another defect among these algorithms is the correlation between the local prediction track estimate errors is ignored; thereby the accuracy of global estimate is reduced. In order to improve the estimate precision of the fusion system, the correlation is considered and the global feedback is introduced in this paper, accordingly a novel optimal asynchronous track fusion algorithm with feedback is presented. Compared with the current algorithm without global feedback and correlation, the proposed method can improve the estimate performance of the fusion system. The algorithm analysis and simulations both show the advantages of the novel algorithm.
Asynchronous fusion is common in processing multisensor data fusion problems and the asynchronous track fusion which adopts distributed fusion architecture has an extensive application among asynchronous fusion. In current asynchronous track fusion algorithms, the global feedback is mostly not established from fusion center to local sensors, so the local estimate can not be improved by the global estimate. Another defect among these algorithms is the correlation between the local prediction track estimate errors is ignored; thereby the accuracy of global estimate is reduced. In order to improve the estimate precision of the fusion system, the correlation is considered and the global feedback is introduced in this paper, accordingly a novel optimal asynchronous track fusion algorithm with feedback is presented. Compared with the current algorithm without global feedback and correlation, the proposed method can improve the estimate performance of the fusion system. The algorithm analysis and simulations both show the advantages of the novel algorithm.
2009, 31(9): 2132-2136.
doi: 10.3724/SP.J.1146.2008.00666
Abstract:
The stability control problem is considered for a class of Fuzzy Bilinear Systems (FBS) with time- varying delay in both state and input. Based on the Parallel Distributed Compensation (PDC) method and free-weighting matrices,some sufficient conditions are derived to guarantee the global asymptotically stability of the overall fuzzy system. The stabilization conditions are further formulated into Linear Matrix Inequalities (LMIs) so that the desired controller can be easily obtained by using the Matlab LMI toolbox. A numerical example is given to show the effectiveness of the presented approach.
The stability control problem is considered for a class of Fuzzy Bilinear Systems (FBS) with time- varying delay in both state and input. Based on the Parallel Distributed Compensation (PDC) method and free-weighting matrices,some sufficient conditions are derived to guarantee the global asymptotically stability of the overall fuzzy system. The stabilization conditions are further formulated into Linear Matrix Inequalities (LMIs) so that the desired controller can be easily obtained by using the Matlab LMI toolbox. A numerical example is given to show the effectiveness of the presented approach.
2009, 31(9): 2137-2142.
doi: 10.3724/SP.J.1146.2008.01075
Abstract:
A non-coherent demodulation algorithm of CPM signal based on composite trellis processing is proposed in this paper. This algorithm figures out composite trellis diagram by combining root trellis diagram and multiple component trellis diagrams which are each a phase-displaced version of a root trellis diagram. It takes advantage of trellis coupling transitions between component trellis diagrams, which helps to trace the original phase of CPM signal and frequency offset effectively. Simulation results show the performance of the proposed algorithm approximates coherent demodulation perfectly when the number of component trellis diagram is greater than four. It is more appropriate to the situation of blind demodulation when carrier recovery is difficult.
A non-coherent demodulation algorithm of CPM signal based on composite trellis processing is proposed in this paper. This algorithm figures out composite trellis diagram by combining root trellis diagram and multiple component trellis diagrams which are each a phase-displaced version of a root trellis diagram. It takes advantage of trellis coupling transitions between component trellis diagrams, which helps to trace the original phase of CPM signal and frequency offset effectively. Simulation results show the performance of the proposed algorithm approximates coherent demodulation perfectly when the number of component trellis diagram is greater than four. It is more appropriate to the situation of blind demodulation when carrier recovery is difficult.
2009, 31(9): 2143-2147.
doi: 10.3724/SP.J.1146.2008.00778
Abstract:
Accumulated-Crossover Parallel-concatenated SPC (A-CPSPC) Codes, which have good bit error rate performance and simple encoding structure, is a class of novel error-correcting codes. A Maximum A Posteriori (MAP) algorithm based on the Sum-Product Algorithm (SPA), is proposed to solve the local decoding, and to eliminate the effect of short cycles. Analysis and simulation results show that the conventional Belief Propagation (BP) decoding algorithm is not suitable for A-CPSPC codes, and the proposed local decoding algorithm can achieve the same performance as the one based on the BCJR algorithm, but has much lower complexity.
Accumulated-Crossover Parallel-concatenated SPC (A-CPSPC) Codes, which have good bit error rate performance and simple encoding structure, is a class of novel error-correcting codes. A Maximum A Posteriori (MAP) algorithm based on the Sum-Product Algorithm (SPA), is proposed to solve the local decoding, and to eliminate the effect of short cycles. Analysis and simulation results show that the conventional Belief Propagation (BP) decoding algorithm is not suitable for A-CPSPC codes, and the proposed local decoding algorithm can achieve the same performance as the one based on the BCJR algorithm, but has much lower complexity.
2009, 31(9): 2148-2151.
doi: 10.3724/SP.J.1146.2008.01208
Abstract:
Cyclic shift permutation structure is an important part of partial parallel decoder for quasi-cyclic LDPC codes. When the information is exchanged, a connecting law of basic switch units in Reverse Banyan network is researched and proved. Then a nonblocking permutation structure based on presetting routing algorithm for cyclic shift is designed. Compared with Benes exchange structure and Reverse Banyan exchange structure, the novel structure increases the exchange speed for information cyclic shift and occupies less hardware resource and area. Finally, an output converting unit is designed, which is adaptable for all kinds of switch structures.
Cyclic shift permutation structure is an important part of partial parallel decoder for quasi-cyclic LDPC codes. When the information is exchanged, a connecting law of basic switch units in Reverse Banyan network is researched and proved. Then a nonblocking permutation structure based on presetting routing algorithm for cyclic shift is designed. Compared with Benes exchange structure and Reverse Banyan exchange structure, the novel structure increases the exchange speed for information cyclic shift and occupies less hardware resource and area. Finally, an output converting unit is designed, which is adaptable for all kinds of switch structures.
2009, 31(9): 2152-2156.
doi: 10.3724/SP.J.1146.2008.00916
Abstract:
A sequenced-based Block Decision-Aided Equalizer (BDAE) for turbo equalization is proposed, which can overcome the deficiency of symbol-by-symbol detection equalizers that the A Posteriori Probability (APP) of each symbol is calculated individually based on a Gaussian distribution assumption of the equalizer output. The proposed equalizer used the full decoders information instead of the extrinsic information to improve the reliability of the estimated sequences. Replacing hard decision with soft decision reduces the effects of the error propagation. Meanwhile, combining soft decision with sequence-based detection provides more reliable information for the calculation of the APP. Simulation results show the new proposed equalizer leads to better performance compared to the Linear Minimum Mean Square Error (LMMSE) equalizers and the BDFE with hard feedback without sacrificing the computational complexity.
A sequenced-based Block Decision-Aided Equalizer (BDAE) for turbo equalization is proposed, which can overcome the deficiency of symbol-by-symbol detection equalizers that the A Posteriori Probability (APP) of each symbol is calculated individually based on a Gaussian distribution assumption of the equalizer output. The proposed equalizer used the full decoders information instead of the extrinsic information to improve the reliability of the estimated sequences. Replacing hard decision with soft decision reduces the effects of the error propagation. Meanwhile, combining soft decision with sequence-based detection provides more reliable information for the calculation of the APP. Simulation results show the new proposed equalizer leads to better performance compared to the Linear Minimum Mean Square Error (LMMSE) equalizers and the BDFE with hard feedback without sacrificing the computational complexity.
2009, 31(9): 2157-2160.
doi: 10.3724/SP.J.1146.2007.00660
Abstract:
In high data rate Transmitted-Reference (TR) Ultra-WideBand (UWB) systems, the conventional autocorrelation receivers introduce the second-order Inter-Symbol Interference (ISI). This paper demonstrates that, through multiple antennas receive and Equal Gain Combining (EGC) significant diversity gain can be obtained. Furthermore, the multiple antennas combination can eliminate the BER floor with the alleviation of the model nonlinearities. The combined system can be simplified to a linear ISI model and the complexity of channel modeling and equalizer can be reduced greatly via a data-aided adaptive algorithm. The performance gap between the approximate linear model and the nonlinear model diminishes with increasing antennas.
In high data rate Transmitted-Reference (TR) Ultra-WideBand (UWB) systems, the conventional autocorrelation receivers introduce the second-order Inter-Symbol Interference (ISI). This paper demonstrates that, through multiple antennas receive and Equal Gain Combining (EGC) significant diversity gain can be obtained. Furthermore, the multiple antennas combination can eliminate the BER floor with the alleviation of the model nonlinearities. The combined system can be simplified to a linear ISI model and the complexity of channel modeling and equalizer can be reduced greatly via a data-aided adaptive algorithm. The performance gap between the approximate linear model and the nonlinear model diminishes with increasing antennas.
2009, 31(9): 2161-2165.
doi: 10.3724/SP.J.1146.2008.01258
Abstract:
In Time-Division Duplex (TDD) system, it is possible to obtain downlink channel metrics at the transmitter due to the channel reciprocity. However, there has a disposal delay between uplink channel and downlink channel in TDD systems, the delay will decrease MU-MIMO precoding performance in time-varying channels. System performance can be improved greatly by channel predictor technique, but the channel prediction error will bring the performance loss. An improved MU-MIMO precoding algorithm based on prediction error is proposed in this paper. Precoding vectors are amended by prediction Mean Square Error (MSE) in this method. Simulation results show that the proposed scheme gets more gains over traditional channel prediction scheme, especially in higher vehicle speed scenario.
In Time-Division Duplex (TDD) system, it is possible to obtain downlink channel metrics at the transmitter due to the channel reciprocity. However, there has a disposal delay between uplink channel and downlink channel in TDD systems, the delay will decrease MU-MIMO precoding performance in time-varying channels. System performance can be improved greatly by channel predictor technique, but the channel prediction error will bring the performance loss. An improved MU-MIMO precoding algorithm based on prediction error is proposed in this paper. Precoding vectors are amended by prediction Mean Square Error (MSE) in this method. Simulation results show that the proposed scheme gets more gains over traditional channel prediction scheme, especially in higher vehicle speed scenario.
2009, 31(9): 2166-2170.
doi: 10.3724/SP.J.1146.2008.00282
Abstract:
Carrier synchronization is one of the most important parts in communications. This paper makes analysis on PLLs phase error during EBPSK carrier recovery. Firstly, under the narrow band Gauss noise condition, PLL linear model is established and output phase noise variance is figured out. Then, comparisons are made with the squiring loop and Costas loop of BPSK. Some simulations are carried out with different input SNR and loop Bandwidth. The results demonstrate that EPBSK signal with duty ratio of 1:9, phase shift of /4, and SNR lower than 6dB performs better than BPSK in carrier recovery.
Carrier synchronization is one of the most important parts in communications. This paper makes analysis on PLLs phase error during EBPSK carrier recovery. Firstly, under the narrow band Gauss noise condition, PLL linear model is established and output phase noise variance is figured out. Then, comparisons are made with the squiring loop and Costas loop of BPSK. Some simulations are carried out with different input SNR and loop Bandwidth. The results demonstrate that EPBSK signal with duty ratio of 1:9, phase shift of /4, and SNR lower than 6dB performs better than BPSK in carrier recovery.
2009, 31(9): 2171-2176.
doi: 10.3724/SP.J.1146.2008.01192
Abstract:
In wireless Multiple-Input Single-Output (MISO) systems with limited feedback of channel information, transmit beamforming can provide both transmit diversity gain and array gain with simple implementation. Most of prior research includes several ideal assumptions, such as block-fading channels, perfect channel information at the receiver, or error-free and zero-delay feedback link. This paper investigates a more realistic Jakes time-varying channel with estimation error and feedback delay, and analyzes the average Bit Error Rate (BER) of the system with square/rectangle Quadrature-Amplitude-Modulation (QAM) constellations. The results show that the analyses are fully consistent with simulations, increasing feedback bits only brings array gain while no diversity gain to the system, beamforming outperforms orthogonal space-time block coding remarkably in slow fading channels, the BER is affected by both channel estimation error and Doppler spread, especially sensitive to the latter.
In wireless Multiple-Input Single-Output (MISO) systems with limited feedback of channel information, transmit beamforming can provide both transmit diversity gain and array gain with simple implementation. Most of prior research includes several ideal assumptions, such as block-fading channels, perfect channel information at the receiver, or error-free and zero-delay feedback link. This paper investigates a more realistic Jakes time-varying channel with estimation error and feedback delay, and analyzes the average Bit Error Rate (BER) of the system with square/rectangle Quadrature-Amplitude-Modulation (QAM) constellations. The results show that the analyses are fully consistent with simulations, increasing feedback bits only brings array gain while no diversity gain to the system, beamforming outperforms orthogonal space-time block coding remarkably in slow fading channels, the BER is affected by both channel estimation error and Doppler spread, especially sensitive to the latter.
2009, 31(9): 2177-2182.
doi: 10.3724/SP.J.1146.2008.00709
Abstract:
To solve the cooperative spectrum sensing problem under constrained control bandwidth in cognitive radio systems, the maximum likelihood cooperative spectrum sensing algorithm based on contracted information is developed in this paper. The contracted information module is used to reduce the network overhead, and the detection based on the Maximum Likelihood (ML) criterion is used to enhance the spectrum sensing performance in the base station. The theoretic analysis and simulation results show that the proposed algorithm can efficaciously improve the spectrum sensing performance with lesser network overhead, especially in the case of the lager discrepancy between the received signal-to-noises of cognitive users.
To solve the cooperative spectrum sensing problem under constrained control bandwidth in cognitive radio systems, the maximum likelihood cooperative spectrum sensing algorithm based on contracted information is developed in this paper. The contracted information module is used to reduce the network overhead, and the detection based on the Maximum Likelihood (ML) criterion is used to enhance the spectrum sensing performance in the base station. The theoretic analysis and simulation results show that the proposed algorithm can efficaciously improve the spectrum sensing performance with lesser network overhead, especially in the case of the lager discrepancy between the received signal-to-noises of cognitive users.
2009, 31(9): 2183-2187.
doi: 10.3724/SP.J.1146.2008.00831
Abstract:
A new antenna selection criterion for Vertical Bell Labs layered Space-Time (V-BLAST) systems based on Zero Forcing (ZF) Successive Interference Cancellation (SIC) detection, which is named minimizing the maximum row norm of the channel matrix, is proposed. Based on the greedy algorithm, incremental selection approach is used to minimize the increment of the norm step by step for transmit antenna selection, and decremental selection approach is used to maximize the decrement of the norm step by step for receive antenna selection. Simulations show the new criterion outperforms the existing so-called max-first layer criterion obviously, and the corresponding fast selection algorithm can obtain the most of the diversity benefit of the optimal exhaustive selection system based on the max-min criterion with a low complexity.
A new antenna selection criterion for Vertical Bell Labs layered Space-Time (V-BLAST) systems based on Zero Forcing (ZF) Successive Interference Cancellation (SIC) detection, which is named minimizing the maximum row norm of the channel matrix, is proposed. Based on the greedy algorithm, incremental selection approach is used to minimize the increment of the norm step by step for transmit antenna selection, and decremental selection approach is used to maximize the decrement of the norm step by step for receive antenna selection. Simulations show the new criterion outperforms the existing so-called max-first layer criterion obviously, and the corresponding fast selection algorithm can obtain the most of the diversity benefit of the optimal exhaustive selection system based on the max-min criterion with a low complexity.
2009, 31(9): 2188-2192.
doi: 10.3724/SP.J.1146.2008.00868
Abstract:
A low rate CSI (Channel State Information) feedback scheme based on linear prediction is proposed for closed-loop multi-user MIMO-OFDM systems. The subcarriers in OFDM system are divided into several sub-bands according to the coherence bandwidth. MS (Mobile Station) predicts CSI of each sub-band, then feedbacks the quantized and coded prediction error to BS (Base Station). BS recovers CSI from feedback information with the same linear predictor, and performs multi-user spatial multiplexing by zero-forcing beamforming with recovered CSI. The downlink capacities are analyzed in theory, where water-filling power allocation method is assumed. Numerical simulations verify that, BS can recover CSI precisely even if the feedback data (real part or imaginary part) is quantized only by one bit. Compared with the 3GPP LTEs feedback scheme based on codebook, the proposed scheme can suppress CCI better, and achieve much larger capacity. Meanwhile the feedback payload is same as that of 3GPP LTEs scheme.
A low rate CSI (Channel State Information) feedback scheme based on linear prediction is proposed for closed-loop multi-user MIMO-OFDM systems. The subcarriers in OFDM system are divided into several sub-bands according to the coherence bandwidth. MS (Mobile Station) predicts CSI of each sub-band, then feedbacks the quantized and coded prediction error to BS (Base Station). BS recovers CSI from feedback information with the same linear predictor, and performs multi-user spatial multiplexing by zero-forcing beamforming with recovered CSI. The downlink capacities are analyzed in theory, where water-filling power allocation method is assumed. Numerical simulations verify that, BS can recover CSI precisely even if the feedback data (real part or imaginary part) is quantized only by one bit. Compared with the 3GPP LTEs feedback scheme based on codebook, the proposed scheme can suppress CCI better, and achieve much larger capacity. Meanwhile the feedback payload is same as that of 3GPP LTEs scheme.
2009, 31(9): 2193-2198.
doi: 10.3724/SP.J.1146.2008.01441
Abstract:
An energy-efficient adaptive cooperative node selection scheme is proposed for energy-constrained wireless sensor networks. It determines the candidates of the Cooperative Node (CN) based on predetermined energy threshold, and then chooses the best node as the CN of Cluster Head Node (CHN) by considering the residual energy of the candidates as well as the channel state information. It can obtain the optimum energy threshold of different distances by minimizing the total energy consumption. Then the energy threshold is adaptively predetermined for minimizing the total energy consumption according to the distance between the CHN and the Data Fusion Center (DFC). The results of the theoretical analysis and simulation show that the proposed scheme can efficiently balance the transmission energy consumption and the circuit energy consumption so that it can efficiently reduce the total energy consumption, and can obtain the minimum of the total energy consumption.
An energy-efficient adaptive cooperative node selection scheme is proposed for energy-constrained wireless sensor networks. It determines the candidates of the Cooperative Node (CN) based on predetermined energy threshold, and then chooses the best node as the CN of Cluster Head Node (CHN) by considering the residual energy of the candidates as well as the channel state information. It can obtain the optimum energy threshold of different distances by minimizing the total energy consumption. Then the energy threshold is adaptively predetermined for minimizing the total energy consumption according to the distance between the CHN and the Data Fusion Center (DFC). The results of the theoretical analysis and simulation show that the proposed scheme can efficiently balance the transmission energy consumption and the circuit energy consumption so that it can efficiently reduce the total energy consumption, and can obtain the minimum of the total energy consumption.
2009, 31(9): 2199-2204.
doi: 10.3724/SP.J.1146.2008.00305
Abstract:
In this paper, based on localized subcarrier allocation in frequency domain and cyclic-shift allocation in time domain, a kind of ranging time and frequency structure for SC-FDMA system is designed, and adaptive detection thresholds computing method based on concept of peak-filtering to estimate interference and noise power is proposed for the detection of ranging signal. Theoretical analysis and simulation results show that, while ranging signals adopt different ranging code and different cyclic-shift, SINR requirements of 99% successful detection get reduce by 0.5~1 dB compared with traditional method adopting ensemble average correlation power, and the probabilities of false alarm get controlled in the meantime.
In this paper, based on localized subcarrier allocation in frequency domain and cyclic-shift allocation in time domain, a kind of ranging time and frequency structure for SC-FDMA system is designed, and adaptive detection thresholds computing method based on concept of peak-filtering to estimate interference and noise power is proposed for the detection of ranging signal. Theoretical analysis and simulation results show that, while ranging signals adopt different ranging code and different cyclic-shift, SINR requirements of 99% successful detection get reduce by 0.5~1 dB compared with traditional method adopting ensemble average correlation power, and the probabilities of false alarm get controlled in the meantime.
2009, 31(9): 2205-2208.
doi: 10.3724/SP.J.1146.2008.01096
Abstract:
Linear complexity is one of the most important indexes for measuring the randomness properties of sequences. Based on Whiteman-generalized cyclotomy, a new class of generalized cyclotomic sequences with length qp and order 2 is constructed. It is proved that the lower bound of linear complexity of the sequence is pq-p-q+1 with the proper selection of parameters p and q, and the sequence has balance property. Finally, this paper points out the method for determine linear complexity.
Linear complexity is one of the most important indexes for measuring the randomness properties of sequences. Based on Whiteman-generalized cyclotomy, a new class of generalized cyclotomic sequences with length qp and order 2 is constructed. It is proved that the lower bound of linear complexity of the sequence is pq-p-q+1 with the proper selection of parameters p and q, and the sequence has balance property. Finally, this paper points out the method for determine linear complexity.
2009, 31(9): 2209-2213.
doi: 10.3724/SP.J.1146.2008.01231
Abstract:
The paper proposes a mode-adaptive OFDM parameters design method for Digital Frequency Modulation (DFM) radio used in the VHF-FM, and designes two transmission modes according to the Doppler shift range under different channel profiles. In order to effectively counteract frequency-selective fading, it is necessary to set the length-ratio between cyclic prefix and useful part of the OFDM symbol; reasonably choosing the length of the useful part, makes more sub-carriers acquired within the limited bandwidth and the sensitivity to Doppler shift decreased; considering the influence to engineering complexity and data transmission efficiency brought by the number of available sub-carriers, the suitable choice of the number can realize a good trade off. Contrast to the existing parameter suggestions in the DRM-Plus system which has the same channel circumstances, the proposed method can not only counteract frequency-selective fading, but also have advantages of lower sensitivity to Doppler shift, lower engineering complexity and higher data transmission efficiency. Simulated with the existing synchronization acquisition algorithms in time domain, the results show that the proposed parameters can be used in the DFM system.
The paper proposes a mode-adaptive OFDM parameters design method for Digital Frequency Modulation (DFM) radio used in the VHF-FM, and designes two transmission modes according to the Doppler shift range under different channel profiles. In order to effectively counteract frequency-selective fading, it is necessary to set the length-ratio between cyclic prefix and useful part of the OFDM symbol; reasonably choosing the length of the useful part, makes more sub-carriers acquired within the limited bandwidth and the sensitivity to Doppler shift decreased; considering the influence to engineering complexity and data transmission efficiency brought by the number of available sub-carriers, the suitable choice of the number can realize a good trade off. Contrast to the existing parameter suggestions in the DRM-Plus system which has the same channel circumstances, the proposed method can not only counteract frequency-selective fading, but also have advantages of lower sensitivity to Doppler shift, lower engineering complexity and higher data transmission efficiency. Simulated with the existing synchronization acquisition algorithms in time domain, the results show that the proposed parameters can be used in the DFM system.
2009, 31(9): 2214-2219.
doi: 10.3724/SP.J.1146.2008.00466
Abstract:
To overcome the multi-channel hidden terminal problem in distributed cognitive wireless networks as well as improve the performance of the network, a general convex programming model is formulated. The access probability of each cognitive user can be derived from this model. A Distributed Spectrum Access Control (DSAC) algorithm is proposed based on convex optimization. The simulation results show that DSAC can converge during a few intervals, and DSAC can also increase the number of transmission links in the network so as to improve the spectrum efficiency and the network throughput.
To overcome the multi-channel hidden terminal problem in distributed cognitive wireless networks as well as improve the performance of the network, a general convex programming model is formulated. The access probability of each cognitive user can be derived from this model. A Distributed Spectrum Access Control (DSAC) algorithm is proposed based on convex optimization. The simulation results show that DSAC can converge during a few intervals, and DSAC can also increase the number of transmission links in the network so as to improve the spectrum efficiency and the network throughput.
2009, 31(9): 2220-2225.
doi: 10.3724/SP.J.1146.2008.01196
Abstract:
With operation and maintenance mode of telecommunication network changing from network oriented to subscriber oriented, network performance management should also be changed from passive monitoring to proactive monitoring. Proactive Performance Monitoring (PPM) enables a fast fault correction by detecting anomalies designating performance degradation. In this paper, a novel anomaly detection approach is proposed taking advantage of time series prediction and associated confidence interval based on Support Vector Machines (SVM). In addition a novel meta-parameters selection approach is proposed by checking if the training residual is white noise. Theoretical analysis and experimental results verify the correctness of the meta-parameter selection approach and the effectiveness of anomaly detection mechanism.
With operation and maintenance mode of telecommunication network changing from network oriented to subscriber oriented, network performance management should also be changed from passive monitoring to proactive monitoring. Proactive Performance Monitoring (PPM) enables a fast fault correction by detecting anomalies designating performance degradation. In this paper, a novel anomaly detection approach is proposed taking advantage of time series prediction and associated confidence interval based on Support Vector Machines (SVM). In addition a novel meta-parameters selection approach is proposed by checking if the training residual is white noise. Theoretical analysis and experimental results verify the correctness of the meta-parameter selection approach and the effectiveness of anomaly detection mechanism.
2009, 31(9): 2226-2231.
doi: 10.3724/SP.J.1146.2008.00737
Abstract:
Based on the estimated link lifetime, a novel routing mechanism is proposed in this paper to establish the reliable end-to-end path in Ad hoc networks. In order to describe the received signal strength continuously in time domain, the Newton Interpolation Polynomial is constructed according to the received signal strength; and then, the link lifetime is estimated with no prediction on speed, direction and other movement parameters. With the constraint of link lifetime and hop counts, the source nodes set up the paths to destination nodes in hop-by-hop mode. Simulation results show that the received signal strength can be described by Newton interpolation polynomial accurately while the mobile nodes are moving randomly; moreover, the route discovery times and packet drop ratio can be reduced by the routing mechanism.
Based on the estimated link lifetime, a novel routing mechanism is proposed in this paper to establish the reliable end-to-end path in Ad hoc networks. In order to describe the received signal strength continuously in time domain, the Newton Interpolation Polynomial is constructed according to the received signal strength; and then, the link lifetime is estimated with no prediction on speed, direction and other movement parameters. With the constraint of link lifetime and hop counts, the source nodes set up the paths to destination nodes in hop-by-hop mode. Simulation results show that the received signal strength can be described by Newton interpolation polynomial accurately while the mobile nodes are moving randomly; moreover, the route discovery times and packet drop ratio can be reduced by the routing mechanism.
2009, 31(9): 2232-2236.
doi: 10.3724/SP.J.1146.2008.01267
Abstract:
The optimizing problem of content distribution which minimizes the blocking probability and storage consumption on clustered streaming media system is discussed, in the case of knowing every programs unchanged popularity. Firstly, the queuing theory is adopted to analysis the relationship between the servers access probability and the optimizing goal. The ideal access probability of every server can be obtained by some numerical methods, under the circumstance of minimal blocking probability. Content distribution determining each servers access probability, has been proved to be NP-Hard. The whole content distribution process consists of two strategies, i.e. duplicate swapping and peer duplicates access probability adjusting. All the heuristic arithmetic is designed to perform the content distribution in order to minimize the distance between the result of optimization and the ideal one, minimize the storage consumption and reduce the blocking probability. Finally, the correctness of system modeling and the efficiency of proposed arithmetic are verified by numerical analysis and discrete event simulation.
The optimizing problem of content distribution which minimizes the blocking probability and storage consumption on clustered streaming media system is discussed, in the case of knowing every programs unchanged popularity. Firstly, the queuing theory is adopted to analysis the relationship between the servers access probability and the optimizing goal. The ideal access probability of every server can be obtained by some numerical methods, under the circumstance of minimal blocking probability. Content distribution determining each servers access probability, has been proved to be NP-Hard. The whole content distribution process consists of two strategies, i.e. duplicate swapping and peer duplicates access probability adjusting. All the heuristic arithmetic is designed to perform the content distribution in order to minimize the distance between the result of optimization and the ideal one, minimize the storage consumption and reduce the blocking probability. Finally, the correctness of system modeling and the efficiency of proposed arithmetic are verified by numerical analysis and discrete event simulation.
2009, 31(9): 2237-2241.
doi: 10.3724/SP.J.1146.2008.01237
Abstract:
In this paper, a secure error-correcting network coding is proposed using a metric on the space of all subspaces of a message vector space. It shows that a minimum distance decoder for this metric can correct errors of a limited dimension. On the other hand, when the number of channels the adversary can eavesdrop on is less than the max-flow of a network, the adversary can not get any information about the source. Furthermore, when the source and the destination shares a Pseudo-Random number generator and a secret key, the coding scheme can prevent adversary who can eavesdrop on all the channels of a network.
In this paper, a secure error-correcting network coding is proposed using a metric on the space of all subspaces of a message vector space. It shows that a minimum distance decoder for this metric can correct errors of a limited dimension. On the other hand, when the number of channels the adversary can eavesdrop on is less than the max-flow of a network, the adversary can not get any information about the source. Furthermore, when the source and the destination shares a Pseudo-Random number generator and a secret key, the coding scheme can prevent adversary who can eavesdrop on all the channels of a network.
2009, 31(9): 2242-2246.
doi: 10.3724/SP.J.1146.2008.00667
Abstract:
This paper investigates the strategies of relaying based on network coding over wireless communication context with two users and one relay sending data to the base station. Differing from the assumption that the channels from users to relay are reliable, this paper supposes that all channels exit fading phenomenon. The effects on probability of system outage are compared among store-and-forwarding, deterministic network coding and opportunistic network coding. Results of numerical analysis indicate that opportunistic network coding is better than deterministic network coding.
This paper investigates the strategies of relaying based on network coding over wireless communication context with two users and one relay sending data to the base station. Differing from the assumption that the channels from users to relay are reliable, this paper supposes that all channels exit fading phenomenon. The effects on probability of system outage are compared among store-and-forwarding, deterministic network coding and opportunistic network coding. Results of numerical analysis indicate that opportunistic network coding is better than deterministic network coding.
2009, 31(9): 2247-2251.
doi: 10.3724/SP.J.1146.2008.01273
Abstract:
Authentication is critical to secure communication in Ad hoc networks. This paper discusses the shortcomings of distributed authentication schemes in Ad hoc networks with flat structure and the advantages of adopting clustering structure. A zone authentication scheme is proposed to enhance the efficiency of authentication services with less communication cost. The scheme adopts the clustering structure and divides the networks into independent authentication areas, and fits well in the large Ad hoc networks with better scalability and security.
Authentication is critical to secure communication in Ad hoc networks. This paper discusses the shortcomings of distributed authentication schemes in Ad hoc networks with flat structure and the advantages of adopting clustering structure. A zone authentication scheme is proposed to enhance the efficiency of authentication services with less communication cost. The scheme adopts the clustering structure and divides the networks into independent authentication areas, and fits well in the large Ad hoc networks with better scalability and security.
2009, 31(9): 2264-2268.
doi: 10.3724/SP.J.1146.2008.01135
Abstract:
In many literatures, Synthetic Aperture Radar (SAR) data is usually supposed to obey the unimodal distribution, unsuitable in the applications. To overcome the limitation, an Improved Clustering-based Discriminant Analysis (ICDA) method is proposed, which assumes the distribution of each class for SAR data is multimodal, a more reasonable and practical assumption. The detailed procedure of ICDA is to first partition each class of the SAR data into multiple clusters via the fast global k-means clustering algorithm, and then try to find the projection vectors such that the projections of every pair of clusters from different classes are well separated while the within-cluster scatter is minimized. Experimental results performing on SAR ground stationary targets based the Moving and Stationary Target Acquisition and Recognition (MSTAR) public database show that ICDA has better classification capabilities of three true objects classes and rejection capabilities of two confusers classes.
In many literatures, Synthetic Aperture Radar (SAR) data is usually supposed to obey the unimodal distribution, unsuitable in the applications. To overcome the limitation, an Improved Clustering-based Discriminant Analysis (ICDA) method is proposed, which assumes the distribution of each class for SAR data is multimodal, a more reasonable and practical assumption. The detailed procedure of ICDA is to first partition each class of the SAR data into multiple clusters via the fast global k-means clustering algorithm, and then try to find the projection vectors such that the projections of every pair of clusters from different classes are well separated while the within-cluster scatter is minimized. Experimental results performing on SAR ground stationary targets based the Moving and Stationary Target Acquisition and Recognition (MSTAR) public database show that ICDA has better classification capabilities of three true objects classes and rejection capabilities of two confusers classes.
2009, 31(9): 2269-2273.
doi: 10.3724/SP.J.1146.2008.00961
Abstract:
This paper takes the -stable distribution as the noise model and works on the Direction of Arrival (DOA) estimation problem of the cyclostationary signals in the impulsive-noise environment. Since the conventional algorithms based on the classical second order cyclic statistics degenerate severely in the impulsive-noise environment, this paper adopts the fractional lower order cyclic correlation and presents a new algorithm called fractional lower order cyclic MUSIC(FLOCC-MUSIC). It combines the fractional lower order cyclic correlation and MUSIC algorithm, for suppressing the impulse noise and interference in the same frequency band. Simulation results show that the proposed algorithm can give accurate DOA estimation under both Gaussian and impulsive-noise conditions, and its performance is superior to the Cyclic-MUSIC based on second order cyclic correlation.
This paper takes the -stable distribution as the noise model and works on the Direction of Arrival (DOA) estimation problem of the cyclostationary signals in the impulsive-noise environment. Since the conventional algorithms based on the classical second order cyclic statistics degenerate severely in the impulsive-noise environment, this paper adopts the fractional lower order cyclic correlation and presents a new algorithm called fractional lower order cyclic MUSIC(FLOCC-MUSIC). It combines the fractional lower order cyclic correlation and MUSIC algorithm, for suppressing the impulse noise and interference in the same frequency band. Simulation results show that the proposed algorithm can give accurate DOA estimation under both Gaussian and impulsive-noise conditions, and its performance is superior to the Cyclic-MUSIC based on second order cyclic correlation.
2009, 31(9): 2274-2277.
doi: 10.3724/SP.J.1146.2008.01357
Abstract:
A FastICA blind multi-user detection algorithm based on negentropy is proposed, which is based on independent component analysis combined with CDMA receiver in this paper. The non-quadratic function in FastICA algorithm is revised as function with power 4, therefore, based negentropy non-Gaussianity measurement can be transformed into kurtosis form, which could decrease the computational complexity. Meanwhile, by exploiting the independence of the source signals of different users and utilizing spreading codes of target user as training sequence and initialization of unmixing matrix, excellent symbol estimation performance are obtained through stochastic gradient method while the codes of the interfering users in downlink are unknown. Analysis for computational complexity of algorithm shows that computational complexity increases with length of receiving data and number of users. In this work, the ICA blind detection method is compared with traditional matched filter and well-known linear MMSE multi-user detector. Numerical simulations indicate that ICA based detection ability is comparable to MMSE detection performance when MAI is lower in synchronous CDMA channels. With the increase of MAI, the superior performance of ICA has significant improvement gains over exact-MMSE.
A FastICA blind multi-user detection algorithm based on negentropy is proposed, which is based on independent component analysis combined with CDMA receiver in this paper. The non-quadratic function in FastICA algorithm is revised as function with power 4, therefore, based negentropy non-Gaussianity measurement can be transformed into kurtosis form, which could decrease the computational complexity. Meanwhile, by exploiting the independence of the source signals of different users and utilizing spreading codes of target user as training sequence and initialization of unmixing matrix, excellent symbol estimation performance are obtained through stochastic gradient method while the codes of the interfering users in downlink are unknown. Analysis for computational complexity of algorithm shows that computational complexity increases with length of receiving data and number of users. In this work, the ICA blind detection method is compared with traditional matched filter and well-known linear MMSE multi-user detector. Numerical simulations indicate that ICA based detection ability is comparable to MMSE detection performance when MAI is lower in synchronous CDMA channels. With the increase of MAI, the superior performance of ICA has significant improvement gains over exact-MMSE.
2009, 31(9): 2278-2282.
doi: 10.3724/SP.J.1146.2008.01001
Abstract:
The machining quality of reflector antenna panels includes machining accuracy and surface quality, both of them will effect electrical performance of the antenna. For the surface quality which is studied less, surface texture is modeled by fractal function. Microscopic surface texture is introduced in the formula of antennas far field patterns by phase difference. Gaussian integral formula in triangular element is used in numerical solution of the formula. By simulation experiment, the effects of different amplitude, density and roughness of the antenna panels surface texture on antennas far field patterns is studied. Research shows that with the increase of amplitude, the far field pattern changes more; with the increase of density and roughness, the far field pattern change less. And the effect degree of amplitude is the first, the density is the second, the roughness is the least. A new way of studing the effects of surface texture on far field patterns of the reflector antenna is proposed, and the conclusion can be referenced in practice.
The machining quality of reflector antenna panels includes machining accuracy and surface quality, both of them will effect electrical performance of the antenna. For the surface quality which is studied less, surface texture is modeled by fractal function. Microscopic surface texture is introduced in the formula of antennas far field patterns by phase difference. Gaussian integral formula in triangular element is used in numerical solution of the formula. By simulation experiment, the effects of different amplitude, density and roughness of the antenna panels surface texture on antennas far field patterns is studied. Research shows that with the increase of amplitude, the far field pattern changes more; with the increase of density and roughness, the far field pattern change less. And the effect degree of amplitude is the first, the density is the second, the roughness is the least. A new way of studing the effects of surface texture on far field patterns of the reflector antenna is proposed, and the conclusion can be referenced in practice.
2009, 31(9): 2283-2286.
doi: 10.3724/SP.J.1146.2008.00617
Abstract:
As a generalization of Bent functions and Partially Bent functions, Plateaued functions can achieve trade-off among many cryptographic criteria. Based on the relationships between the Walsh transform of a given function and the Walsh transform of its decomposing function, the normality of Plateaued functions is studied. Then a simpler algorithm for checking the normality of Plateaued functions is proposed. Finally, the normality of some known kind of Plateaued functions is discussed.
As a generalization of Bent functions and Partially Bent functions, Plateaued functions can achieve trade-off among many cryptographic criteria. Based on the relationships between the Walsh transform of a given function and the Walsh transform of its decomposing function, the normality of Plateaued functions is studied. Then a simpler algorithm for checking the normality of Plateaued functions is proposed. Finally, the normality of some known kind of Plateaued functions is discussed.
2009, 31(9): 2252-2259.
doi: 10.3724/SP.J.1146.2008.01073
Abstract:
The goal of the ubiquitous convergent network is to provide the dynamicly adaptive and context- awareness pervasive services. However, the existing telecommunication service opening architecture based on the traditional distributed computing technologies is unable to meet the development trends and characteristics of the future user-centric intelligent convergent services. This paper presents the great changes of user-centric convergent service provision pattern. And then the semantic interoperability-enabled user-centric convergent service architecture and key technologies are proposed. This approach can seamlessly integrate the telecommunications and Internet services in the semantic level and then create a virtual convergent service computing environment.
The goal of the ubiquitous convergent network is to provide the dynamicly adaptive and context- awareness pervasive services. However, the existing telecommunication service opening architecture based on the traditional distributed computing technologies is unable to meet the development trends and characteristics of the future user-centric intelligent convergent services. This paper presents the great changes of user-centric convergent service provision pattern. And then the semantic interoperability-enabled user-centric convergent service architecture and key technologies are proposed. This approach can seamlessly integrate the telecommunications and Internet services in the semantic level and then create a virtual convergent service computing environment.
2009, 31(9): 2260-2263.
doi: 10.3724/SP.J.1146.2008.01206
Abstract:
According to the structure properties of CLEFIA , new 8-round distinguishers for Square attack are presented, and the wrong 8-round distinguishers originally found by the designers are pointed out. Based on the new distinguisher, the square attack on CLEFIA can be improved as follows: 10-round CLEFIA-128\192\256 is attacked with data complexity 297 and time complexity 292.7, 11-round CLEFIA-192/256 is attacked with data complexity 298 and time complexity 2157.6, and 12-round CLEFIA-256 is breakable with data complexity 298.6 and time complexity 2222. These results demonstrate that under the case of 10-round CLEFIA, both data and time complexity of our attack are better than those given by the designers.
According to the structure properties of CLEFIA , new 8-round distinguishers for Square attack are presented, and the wrong 8-round distinguishers originally found by the designers are pointed out. Based on the new distinguisher, the square attack on CLEFIA can be improved as follows: 10-round CLEFIA-128\192\256 is attacked with data complexity 297 and time complexity 292.7, 11-round CLEFIA-192/256 is attacked with data complexity 298 and time complexity 2157.6, and 12-round CLEFIA-256 is breakable with data complexity 298.6 and time complexity 2222. These results demonstrate that under the case of 10-round CLEFIA, both data and time complexity of our attack are better than those given by the designers.
