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2008 Vol. 30, No. 10
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2008, 30(10): 2287-2290.
doi: 10.3724/SP.J.1146.2007.01553
Abstract:
A robust spatio-temporal video denoising algorithm is proposed based on the motion estimation, which is embedded into the video encoder. On one hand, this algorithm can be used in the space domain to eliminate the false similar pixels from neighbor pixels and improve the efficiency of pixels; it also can be used in the time domain to reduce the flicker among frames, and avoid motion blur. On the other hand, the algorithm can realize the adaptive strength of the filter and protect the special detail, when the size or the weight of the filters is adaptively adjusted by the strength of the noise and the edge information.
A robust spatio-temporal video denoising algorithm is proposed based on the motion estimation, which is embedded into the video encoder. On one hand, this algorithm can be used in the space domain to eliminate the false similar pixels from neighbor pixels and improve the efficiency of pixels; it also can be used in the time domain to reduce the flicker among frames, and avoid motion blur. On the other hand, the algorithm can realize the adaptive strength of the filter and protect the special detail, when the size or the weight of the filters is adaptively adjusted by the strength of the noise and the edge information.
2008, 30(10): 2291-2294.
doi: 10.3724/SP.J.1146.2007.00534
Abstract:
To resolve the issue of window width selection, an adaptive algorithm for Gabor transform is proposed, which improves the concentration and time-frequency resolution of Gabor representation. The value range of Shannon entropy is mended to make it more adequate for measuring concentration of time-frequency distribution. Moreover, basing on entropy, an optimal window width can be searched adaptively. Simulation results show that the proposed algorithm chooses the optimal window width for mono-component signal or multi-component signal, giving the best Gabor representation with high concentration and time-frequency resolution. Additionally, the algorithm behaves well under low signal noise ratio.
To resolve the issue of window width selection, an adaptive algorithm for Gabor transform is proposed, which improves the concentration and time-frequency resolution of Gabor representation. The value range of Shannon entropy is mended to make it more adequate for measuring concentration of time-frequency distribution. Moreover, basing on entropy, an optimal window width can be searched adaptively. Simulation results show that the proposed algorithm chooses the optimal window width for mono-component signal or multi-component signal, giving the best Gabor representation with high concentration and time-frequency resolution. Additionally, the algorithm behaves well under low signal noise ratio.
2008, 30(10): 2295-2298.
doi: 10.3724/SP.J.1146.2007.00388
Abstract:
A novel method is proposed to estimate 2-dimensional (2-D) angles of arrival (AOAs) of wideband chirp signals in direction-dependent sensor complex gain condition. In this method, via the algebraic structure of wideband chirp signals time-varying manifold, a manifold time-frequency transform is presented to obtain closed-form 2-D angles estimation and sensor errors elimination. The efficacy of the proposed method is verified by simulation results.
A novel method is proposed to estimate 2-dimensional (2-D) angles of arrival (AOAs) of wideband chirp signals in direction-dependent sensor complex gain condition. In this method, via the algebraic structure of wideband chirp signals time-varying manifold, a manifold time-frequency transform is presented to obtain closed-form 2-D angles estimation and sensor errors elimination. The efficacy of the proposed method is verified by simulation results.
2008, 30(10): 2299-2302.
doi: 10.3724/SP.J.1146.2007.00483
Abstract:
The rules of correlation between auto-terms and cross-terms of Wigner-Ville Distribution(WVD) are obtained by analyzing the WVD and a new method to suppress cross-terms of WVD using Adaptive Short-Time Fourier Transform (ASTFT) spectrum is put forward. Firstly, the signal ASTFT spectrum which can determine the signal component positions in the time-frequency plane is obtained. Then, window function, ASTFT spectrum, is selected to process the signal WVD. Thus the cross-term interference can be effectively restrained, and it retains the much finer characteristics of WVD, such as high resolution jointly in time and frequency and energy centralizing. The examples indicate that a better resolution and more effective suppression of cross-term interference is obtained in the end.
The rules of correlation between auto-terms and cross-terms of Wigner-Ville Distribution(WVD) are obtained by analyzing the WVD and a new method to suppress cross-terms of WVD using Adaptive Short-Time Fourier Transform (ASTFT) spectrum is put forward. Firstly, the signal ASTFT spectrum which can determine the signal component positions in the time-frequency plane is obtained. Then, window function, ASTFT spectrum, is selected to process the signal WVD. Thus the cross-term interference can be effectively restrained, and it retains the much finer characteristics of WVD, such as high resolution jointly in time and frequency and energy centralizing. The examples indicate that a better resolution and more effective suppression of cross-term interference is obtained in the end.
2008, 30(10): 2303-2306.
doi: 10.3724/SP.J.1146.2007.00617
Abstract:
PCM signal is a kind of pulse compression signal which is widely used in low probability of intercept adopting pulse compression radar system. An accurate estimation of Doppler frequency rate-of-change from received signal is a key technology in the passive locating and tracking system of single observer based on particle kinematics theory. In consideration of the in-pulse phase modulation and Doppler frequency rate-of-changes subtleness, a fast and accurate algorithm is proposed. The influence to parameter estimation with phase modulation is dismissed by time domain correlation between neighboring pulses. Signal noise ratio is increased by frequency domain accumulation. Frequency domain correlation is used to realize phase unwrapping and enhance the Doppler frequency rate-of-change based on the coherent characteristic between pulses. This algorithm has small computation which provides well condition for application to practice. The computer simulation results demonstrate the efficiency of this algorithm.
PCM signal is a kind of pulse compression signal which is widely used in low probability of intercept adopting pulse compression radar system. An accurate estimation of Doppler frequency rate-of-change from received signal is a key technology in the passive locating and tracking system of single observer based on particle kinematics theory. In consideration of the in-pulse phase modulation and Doppler frequency rate-of-changes subtleness, a fast and accurate algorithm is proposed. The influence to parameter estimation with phase modulation is dismissed by time domain correlation between neighboring pulses. Signal noise ratio is increased by frequency domain accumulation. Frequency domain correlation is used to realize phase unwrapping and enhance the Doppler frequency rate-of-change based on the coherent characteristic between pulses. This algorithm has small computation which provides well condition for application to practice. The computer simulation results demonstrate the efficiency of this algorithm.
2008, 30(10): 2307-2310.
doi: 10.3724/SP.J.1146.2007.00384
Abstract:
A DWT domain multiple watermarking scheme based on blind source separation is proposed in this paper. In consideration of the embedding order and safety, two original watermarks are mixed with a chaotic sequence to generate an embedding watermark signal. Then the host audio signal is transformed into wavelet domain to obtain the low frequency coefficients and the embedding watermark is embedded in with the linear mixing model. In the extraction procedure, the FastICA is applied to obtain the embedding watermark signal and the original watermark signals. The scheme is a blind watermarking method and need not consider the embedding order. The experimental results show that the method proposed in this paper is robust against most common signal processing and the time-scale modification.
A DWT domain multiple watermarking scheme based on blind source separation is proposed in this paper. In consideration of the embedding order and safety, two original watermarks are mixed with a chaotic sequence to generate an embedding watermark signal. Then the host audio signal is transformed into wavelet domain to obtain the low frequency coefficients and the embedding watermark is embedded in with the linear mixing model. In the extraction procedure, the FastICA is applied to obtain the embedding watermark signal and the original watermark signals. The scheme is a blind watermarking method and need not consider the embedding order. The experimental results show that the method proposed in this paper is robust against most common signal processing and the time-scale modification.
2008, 30(10): 2311-2314.
doi: 10.3724/SP.J.1146.2007.01666
Abstract:
A novel fast multi-mode motion estimation algorithm based on the quantum clonal selection is proposed. According to the predictive motion vectors derived from spatio-temporal coherence of video sequences, the type of searching modes can be confirmed adaptively. In the stationary macroblock mode, current search is terminated immediately. In the mild motion mode, CDS method is used directly. In the drastic motion mode, a combined QCS/CDS search strategy is utilized. Firstly, the QCS method is used to search the appropriate optimal motion vector, then the CDS method is used to search global optimal motion vector. Experimental results show that the algorithm can speed up the process of motion estimation with fewer search points, while maintaining the average PSNR by using the full search algorithm with little loss.
A novel fast multi-mode motion estimation algorithm based on the quantum clonal selection is proposed. According to the predictive motion vectors derived from spatio-temporal coherence of video sequences, the type of searching modes can be confirmed adaptively. In the stationary macroblock mode, current search is terminated immediately. In the mild motion mode, CDS method is used directly. In the drastic motion mode, a combined QCS/CDS search strategy is utilized. Firstly, the QCS method is used to search the appropriate optimal motion vector, then the CDS method is used to search global optimal motion vector. Experimental results show that the algorithm can speed up the process of motion estimation with fewer search points, while maintaining the average PSNR by using the full search algorithm with little loss.
2008, 30(10): 2315-2319.
doi: 10.3724/SP.J.1146.2007.00499
Abstract:
In order to extract effectively the feature of SEMG signal, an improved method of feature extraction based on correlation analysis is proposed. Firstly, the paper decreases the noise included in two channel SEMG signals using spatial correlation filtering. Secondly, the paper analyzes SEMG signal after de-noising with 4-scale wavelet transformation and extract wavelet coefficient of the main fringe by arithmetic of correlation analysis. A 6-dimension eigenvector which is constructed with sum of squares of the wavelet coefficient is inputted SVM. The result shows that four movements (wrist spreads, wrist bends, hand extension, hand grasps) are successfully identified by the method of SVM combined with the eigenvector which is constructed at the condition of correlation analysis and wavelet transformation. The more precise classified results can be get than neural network sorter with this method.
In order to extract effectively the feature of SEMG signal, an improved method of feature extraction based on correlation analysis is proposed. Firstly, the paper decreases the noise included in two channel SEMG signals using spatial correlation filtering. Secondly, the paper analyzes SEMG signal after de-noising with 4-scale wavelet transformation and extract wavelet coefficient of the main fringe by arithmetic of correlation analysis. A 6-dimension eigenvector which is constructed with sum of squares of the wavelet coefficient is inputted SVM. The result shows that four movements (wrist spreads, wrist bends, hand extension, hand grasps) are successfully identified by the method of SVM combined with the eigenvector which is constructed at the condition of correlation analysis and wavelet transformation. The more precise classified results can be get than neural network sorter with this method.
2008, 30(10): 2320-2324.
doi: 10.3724/SP.J.1146.2007.00566
Abstract:
Based on the particle swarm optimization and antibody clonal selection theory, a novel Orthogonal Immune Clone Particle Swarm Algorithm (OICPSO) is presented to solve multiobjective optimization. According to the problem characters, clone operator, immune gene operator and clone selection operator are designed in this paper. And discrete orthogonal crossover operator is used in immune gene operations to obtain uniformity of the objective space and the idea Pareto solutions. And crowding-comparison approach is adopted to obtain the uniformity of the population distribution. In experiments, the results of OICPSO are compared with NSGA-II and MOPSO, and the quality of solutions is analyzed with parameters. The results indicate that OICPSO not only can increase the solutions diversity but also can obtain the Pareto solutions. OICPSO is effective on multiobjective optimizations.
Based on the particle swarm optimization and antibody clonal selection theory, a novel Orthogonal Immune Clone Particle Swarm Algorithm (OICPSO) is presented to solve multiobjective optimization. According to the problem characters, clone operator, immune gene operator and clone selection operator are designed in this paper. And discrete orthogonal crossover operator is used in immune gene operations to obtain uniformity of the objective space and the idea Pareto solutions. And crowding-comparison approach is adopted to obtain the uniformity of the population distribution. In experiments, the results of OICPSO are compared with NSGA-II and MOPSO, and the quality of solutions is analyzed with parameters. The results indicate that OICPSO not only can increase the solutions diversity but also can obtain the Pareto solutions. OICPSO is effective on multiobjective optimizations.
2008, 30(10): 2325-2328.
doi: 10.3724/SP.J.1146.2007.00417
Abstract:
The automatic detection of building boundaries in a single high-resolution urban SAR (Synthetic Aperture Radar) image based on watershed transform with markers is proposed in this paper. According to the strong radar backscatter energy and shape feature of a building in SAR images, markers are extracted mainly by a CFAR detector and direction-correlation analysis. Then the minima imposition is used to modify the gradient of the initial SAR image with the help of markers. Finally, the building boundaries are obtained by computing the watersheds of the modified gradient image. The experiment shows the feasibility of our method.
The automatic detection of building boundaries in a single high-resolution urban SAR (Synthetic Aperture Radar) image based on watershed transform with markers is proposed in this paper. According to the strong radar backscatter energy and shape feature of a building in SAR images, markers are extracted mainly by a CFAR detector and direction-correlation analysis. Then the minima imposition is used to modify the gradient of the initial SAR image with the help of markers. Finally, the building boundaries are obtained by computing the watersheds of the modified gradient image. The experiment shows the feasibility of our method.
2008, 30(10): 2329-2332.
doi: 10.3724/SP.J.1146.2007.00251
Abstract:
An algorithm for measuring missile-target miss distance using radar data processing is presented. Based on accurate three-dimensional motion mode, the curve of square-distance translated from radar data between missile and target is fitted with nonlinear method, and differentiated and sought on the zero point to confirm the miss time. The vector miss distance and scalar miss distance can be obtained by fitting three-dimensional motion function and substituting the miss time into that. The simulation experiment shows that the algorithm has good accuracy and stability, which can apply valid result for practical applying.
An algorithm for measuring missile-target miss distance using radar data processing is presented. Based on accurate three-dimensional motion mode, the curve of square-distance translated from radar data between missile and target is fitted with nonlinear method, and differentiated and sought on the zero point to confirm the miss time. The vector miss distance and scalar miss distance can be obtained by fitting three-dimensional motion function and substituting the miss time into that. The simulation experiment shows that the algorithm has good accuracy and stability, which can apply valid result for practical applying.
Preprocessing of Target Recognition of the Instantaneous Polarimetric Radar in the Jamming Situation
2008, 30(10): 2333-2337.
doi: 10.3724/SP.J.1146.2007.01525
Abstract:
The polarization scattering matrix characteristic of the active decoys produced by the single polarized repeater is analysed under the background of the anti-jamming of the instantaneous polarimetric radar. It is shown that the characteristics of active decoys measured by the interleaved-pulse polarization agile radar and the instantaneous polarimetric radar are different, though the active decoys is produced by the same jamming mode. Further more, considering the scattering matrix may not be able to be measured accurately in the jamming situation, a preprocessing method in target reorganization based on the inadequate polarization characteristics is produced, employing which the three series of scattering matrix of target can be obtained which can be used as the robust features in target recognition.
The polarization scattering matrix characteristic of the active decoys produced by the single polarized repeater is analysed under the background of the anti-jamming of the instantaneous polarimetric radar. It is shown that the characteristics of active decoys measured by the interleaved-pulse polarization agile radar and the instantaneous polarimetric radar are different, though the active decoys is produced by the same jamming mode. Further more, considering the scattering matrix may not be able to be measured accurately in the jamming situation, a preprocessing method in target reorganization based on the inadequate polarization characteristics is produced, employing which the three series of scattering matrix of target can be obtained which can be used as the robust features in target recognition.
2008, 30(10): 2338-2342.
doi: 10.3724/SP.J.1146.2007.00545
Abstract:
Secondary data acquired with sliding window method can accurately estimate clutter statistics of target-gate under localized stationary environment. In this paper, a recursive QR factorization method based on sliding window is presented, which adopts hyperbolic Househoulder transformation to realize the recursion of QR factorization. The method can not only suppress localized stationary clutter effectively, but also exhibit good numerical stability and low complexity. Simulation data processing results and real data processing results are given to demonstrate the effectiveness of the method.
Secondary data acquired with sliding window method can accurately estimate clutter statistics of target-gate under localized stationary environment. In this paper, a recursive QR factorization method based on sliding window is presented, which adopts hyperbolic Househoulder transformation to realize the recursion of QR factorization. The method can not only suppress localized stationary clutter effectively, but also exhibit good numerical stability and low complexity. Simulation data processing results and real data processing results are given to demonstrate the effectiveness of the method.
2008, 30(10): 2343-2346.
doi: 10.3724/SP.J.1146.2007.00418
Abstract:
In order to satisfy some special demands for detection and recognition to the guiding radar of Air Defense Missile Weapon System (ADMWS) using an active radar seeker, an analysis method of planar slotted array antennal RCS is stressly studied based on the theory of the antennal electromagnetic scattering mechanism. An electromagnetic scattering model of the antennas is established, and it introduces the detailed calculation procedure. The influences to antennas RCS of factors such as antenna size, frequency and quantity of slot etc are detailedly discussed. The simulation result shows that RCS of radar antenna is biggish and possesses obvious periodicity, and the range characteristic and period characteristic can be regarded the important basis of recognition. The work is meaningful for the research on detection and recognition algorithm for ground-based radar stations.
In order to satisfy some special demands for detection and recognition to the guiding radar of Air Defense Missile Weapon System (ADMWS) using an active radar seeker, an analysis method of planar slotted array antennal RCS is stressly studied based on the theory of the antennal electromagnetic scattering mechanism. An electromagnetic scattering model of the antennas is established, and it introduces the detailed calculation procedure. The influences to antennas RCS of factors such as antenna size, frequency and quantity of slot etc are detailedly discussed. The simulation result shows that RCS of radar antenna is biggish and possesses obvious periodicity, and the range characteristic and period characteristic can be regarded the important basis of recognition. The work is meaningful for the research on detection and recognition algorithm for ground-based radar stations.
2008, 30(10): 2347-2351.
doi: 10.3724/SP.J.1146.2007.00346
Abstract:
A new feature selection algorithm is presented using SVM, and then it is integrated into the classification procedure of polarimetric SAR images to construct a novel SVM-based classification method. In the novel method, the sequential backward selection strategy is used to search feature subsets, and the number of support vectors is taken as the estimation index. Compared with those using the initial feature set and the classical RELIEF-F algorithm, higher classification accuracy with less or equivalent number of features is observed in a wider range of SVM parameters using the novel method.
A new feature selection algorithm is presented using SVM, and then it is integrated into the classification procedure of polarimetric SAR images to construct a novel SVM-based classification method. In the novel method, the sequential backward selection strategy is used to search feature subsets, and the number of support vectors is taken as the estimation index. Compared with those using the initial feature set and the classical RELIEF-F algorithm, higher classification accuracy with less or equivalent number of features is observed in a wider range of SVM parameters using the novel method.
2008, 30(10): 2352-2355.
doi: 10.3724/SP.J.1146.2007.00469
Abstract:
In order to store MODIS multispectral images effectively, a new hybrid compression algorithm based on optimal inter-band prediction and integer wavelet transform is proposed. First, an optimal inter-band predictor is designed for de-correlating the spectral redundancy, and the error images are created for later use. Next, spatial redundancy is removed by using an efficient integer wavelet coding method and SPIHT algorithm. Then, the adaptive arithmetic encoder is employed for binary code stream. The proposed method can implement the lossless compression, near-lossless compression and lossy compression with high compression ratio. The experimental results show that this method is more efficient than the traditional 3D-SPIHT algorithm and other wavelet transform methods with different wavelet bases.
In order to store MODIS multispectral images effectively, a new hybrid compression algorithm based on optimal inter-band prediction and integer wavelet transform is proposed. First, an optimal inter-band predictor is designed for de-correlating the spectral redundancy, and the error images are created for later use. Next, spatial redundancy is removed by using an efficient integer wavelet coding method and SPIHT algorithm. Then, the adaptive arithmetic encoder is employed for binary code stream. The proposed method can implement the lossless compression, near-lossless compression and lossy compression with high compression ratio. The experimental results show that this method is more efficient than the traditional 3D-SPIHT algorithm and other wavelet transform methods with different wavelet bases.
2008, 30(10): 2356-2359.
doi: 10.3724/SP.J.1146.2007.00482
Abstract:
Threshold denoising in wavelet domain is an efficient method to reduce the white noise which is easy to program, so that it is widely applied to the image and signal denoising. According to the wavelet transformation characteristic of the MMV target radiation signal, the non-negative wavelet coefficient is used to replace the wavelet coefficient of the signal. For the definite threshold, denoising method of the non-negative wavelet coefficient is inferred when the MSE of the reconfigurable signal is minimized. Experiments show that the method can suppress the noise effectively.
Threshold denoising in wavelet domain is an efficient method to reduce the white noise which is easy to program, so that it is widely applied to the image and signal denoising. According to the wavelet transformation characteristic of the MMV target radiation signal, the non-negative wavelet coefficient is used to replace the wavelet coefficient of the signal. For the definite threshold, denoising method of the non-negative wavelet coefficient is inferred when the MSE of the reconfigurable signal is minimized. Experiments show that the method can suppress the noise effectively.
2008, 30(10): 2360-2363.
doi: 10.3724/SP.J.1146.2007.00419
Abstract:
A parallel algorithm via Element Level Vector Finite Element Method(ELVFEM) and Adaptive Multilevel Fast Multipole Algorithm(AMLFMA) is introduced. In this algorithm the calculation of finite element method can be finished at elementary level and no need to form the global coefficient matrix. By expanding the basis functions and testing functions with Dirac functions on different position, the integration calculation of the multilevel fast multipole algorithm can be simplified and transformation procedure can be calculated by FFT. Combining this algorithm with Asymptotic Wave form Evaluation (AWE) technique, the RCS of electrically large coated scatters can be calculated fast. The numerical results show the effectiveness of the presented parallel algorithm.
A parallel algorithm via Element Level Vector Finite Element Method(ELVFEM) and Adaptive Multilevel Fast Multipole Algorithm(AMLFMA) is introduced. In this algorithm the calculation of finite element method can be finished at elementary level and no need to form the global coefficient matrix. By expanding the basis functions and testing functions with Dirac functions on different position, the integration calculation of the multilevel fast multipole algorithm can be simplified and transformation procedure can be calculated by FFT. Combining this algorithm with Asymptotic Wave form Evaluation (AWE) technique, the RCS of electrically large coated scatters can be calculated fast. The numerical results show the effectiveness of the presented parallel algorithm.
2008, 30(10): 2364-2368.
doi: 10.3724/SP.J.1146.2007.00540
Abstract:
In this paper, an Adaptively Modified Characteristic Basis Function Method (AMCBFM) based on partitioning object geometry into blocks is proposed. Firstly, the primary CBFs arising from the self-interaction within the self-block are generated, then the primary current vector is elicited; subsequently, the second CBFs which account for the mutual coupling effects from the other distinct domains expect the own ones by using the inter-impedances, primary current vectors and the modulus of the primary CBFs coefficients, is gotten. And a more accurate current vector is obtained. The higher CBFs can be also derived with the same way. The difference of the currents convergence speeds between the new CBFM and conventional CBFMs under diverse models via a new convenient method of controlling the result precision is discussed, and the results show that the new CBFM is better than those of conventional ones. Finally, the relationship between the block number and the unknowns under the condition of improving calculating speed is analyzed. The numerical results indicate that the new method has a series of merits: reducing the size of the matrix equation into a small level, the satisfying precision, high calculating speed and simple error control condition.
In this paper, an Adaptively Modified Characteristic Basis Function Method (AMCBFM) based on partitioning object geometry into blocks is proposed. Firstly, the primary CBFs arising from the self-interaction within the self-block are generated, then the primary current vector is elicited; subsequently, the second CBFs which account for the mutual coupling effects from the other distinct domains expect the own ones by using the inter-impedances, primary current vectors and the modulus of the primary CBFs coefficients, is gotten. And a more accurate current vector is obtained. The higher CBFs can be also derived with the same way. The difference of the currents convergence speeds between the new CBFM and conventional CBFMs under diverse models via a new convenient method of controlling the result precision is discussed, and the results show that the new CBFM is better than those of conventional ones. Finally, the relationship between the block number and the unknowns under the condition of improving calculating speed is analyzed. The numerical results indicate that the new method has a series of merits: reducing the size of the matrix equation into a small level, the satisfying precision, high calculating speed and simple error control condition.
2008, 30(10): 2369-2372.
doi: 10.3724/SP.J.1146.2007.00380
Abstract:
This paper introduces a new family of cost function for blind equalization. This cost function family has clear mathematic meanings. This cost function includes the well-know Decision-Directed algorithm, Sato algorithm, CMA algorithm and its mutations. And new Bussgang method can be got by this cost function. This paper presents two new method originated from this cost function. Simulation results verify these two methods convergence.
This paper introduces a new family of cost function for blind equalization. This cost function family has clear mathematic meanings. This cost function includes the well-know Decision-Directed algorithm, Sato algorithm, CMA algorithm and its mutations. And new Bussgang method can be got by this cost function. This paper presents two new method originated from this cost function. Simulation results verify these two methods convergence.
2008, 30(10): 2373-2376.
doi: 10.3724/SP.J.1146.2007.00582
Abstract:
A novel Volterra equalizer based on minimum bit error rate principle is proposed in this paper for interference suppression in communications. The Volterra kernels are estimated based on minimum bit error rate principle and this is different from the previous literatures which are based on minimum mean square error. Simulation results show that when extended binary phase shifting keying signals are contaminated by relatively strong narrowband interference, the performance of matched filters and linear equalizers degenerate rapidly, but Volterra equalizers based on minimum bit error rate provide very low bit error rate, and their performance is also far better than that of Volterra equalizers based on minimum mean square error. Furthermore, it is found that odd and third-order Volterra equalizers are more practical than other order Volterra equalizers.
A novel Volterra equalizer based on minimum bit error rate principle is proposed in this paper for interference suppression in communications. The Volterra kernels are estimated based on minimum bit error rate principle and this is different from the previous literatures which are based on minimum mean square error. Simulation results show that when extended binary phase shifting keying signals are contaminated by relatively strong narrowband interference, the performance of matched filters and linear equalizers degenerate rapidly, but Volterra equalizers based on minimum bit error rate provide very low bit error rate, and their performance is also far better than that of Volterra equalizers based on minimum mean square error. Furthermore, it is found that odd and third-order Volterra equalizers are more practical than other order Volterra equalizers.
2008, 30(10): 2377-2380.
doi: 10.3724/SP.J.1146.2007.01261
Abstract:
Block prefix is usually added in block transmission system for facilitating channel identification. With cyclic prefix, the channel matrix exhibits block circulant property which is exploited to blindly identify periodically modulated block transmission system in an existing method. In this paper, this method is extended to multi-user system and some identifiability conditions are given. Though also as a second order statistics based scheme, not like many subspace based methods, this new approach owns the advantage of not sensitive to noises, channel order mismatching or channel zero locations. Simulation examples demonstrate its good performance under low SNR.
Block prefix is usually added in block transmission system for facilitating channel identification. With cyclic prefix, the channel matrix exhibits block circulant property which is exploited to blindly identify periodically modulated block transmission system in an existing method. In this paper, this method is extended to multi-user system and some identifiability conditions are given. Though also as a second order statistics based scheme, not like many subspace based methods, this new approach owns the advantage of not sensitive to noises, channel order mismatching or channel zero locations. Simulation examples demonstrate its good performance under low SNR.
2008, 30(10): 2381-2383.
doi: 10.3724/SP.J.1146.2007.00749
Abstract:
In this paper, a novel blind channel estimation algorithm based on tap detecting is proposed for the chip-rate discrete channel of the TH-PPM Ultra Wide-Band(UWB) communications. In this algorithm, the cyclic convolution property of the receive signals expectation is used to model the question of channel estimation, and the sparse and cluster structure of UWB channel is used to avoid non-important zero taps estimation which promoted the performance of the algorithm. Simulation results demonstrated that the mean square error of the UWB-TDLS is 5.5dBs lower than UWB-LS in the situation of low signal to noise ratio(0-15dB), while it is 3.5dB lower in the situation of high signal to noise ratio(15dB), moreover the UWB-TDLS also has better signal-error-ratio performance than UWB-LS.
In this paper, a novel blind channel estimation algorithm based on tap detecting is proposed for the chip-rate discrete channel of the TH-PPM Ultra Wide-Band(UWB) communications. In this algorithm, the cyclic convolution property of the receive signals expectation is used to model the question of channel estimation, and the sparse and cluster structure of UWB channel is used to avoid non-important zero taps estimation which promoted the performance of the algorithm. Simulation results demonstrated that the mean square error of the UWB-TDLS is 5.5dBs lower than UWB-LS in the situation of low signal to noise ratio(0-15dB), while it is 3.5dB lower in the situation of high signal to noise ratio(15dB), moreover the UWB-TDLS also has better signal-error-ratio performance than UWB-LS.
2008, 30(10): 2384-2387.
doi: 10.3724/SP.J.1146.2007.00526
Abstract:
Quasi Cyclic LDPC (QC-LDPC) codes are of particular interest in various areas. In this paper, a method to construct a class of QC-LDPC codes based on circulant permutation matrices is showed. The method chooses the position of each non-zero sub-matrix in the bipartite graph based on blocks. Then the circulant permutation value of each sub-matrix is decided. With the proposed algorithm, a few LDPC codes were constructed with the code length from 1008 bit to 8064 bit and with code rate from 1/2 to 7/8. Simulation results show that the proposed LDPC codes are superior to QC-LDPC codes with other construction algorithms.
Quasi Cyclic LDPC (QC-LDPC) codes are of particular interest in various areas. In this paper, a method to construct a class of QC-LDPC codes based on circulant permutation matrices is showed. The method chooses the position of each non-zero sub-matrix in the bipartite graph based on blocks. Then the circulant permutation value of each sub-matrix is decided. With the proposed algorithm, a few LDPC codes were constructed with the code length from 1008 bit to 8064 bit and with code rate from 1/2 to 7/8. Simulation results show that the proposed LDPC codes are superior to QC-LDPC codes with other construction algorithms.
2008, 30(10): 2388-2391.
doi: 10.3724/SP.J.1146.2007.00503
Abstract:
A general structure of CSS-type quantum convolutional codes is presented. The standard form of stabilizers, operators and operators are also given. Encoding and decoding of the codes are discussed with emphasis and corresponding networks are described. Only Hadamard and controlled NOT operations are involved in the whole process of encoding and decoding CSS-type quantum convolutional codes, so simple networks are obtained with low complexity.
A general structure of CSS-type quantum convolutional codes is presented. The standard form of stabilizers, operators and operators are also given. Encoding and decoding of the codes are discussed with emphasis and corresponding networks are described. Only Hadamard and controlled NOT operations are involved in the whole process of encoding and decoding CSS-type quantum convolutional codes, so simple networks are obtained with low complexity.
2008, 30(10): 2392-2396.
doi: 10.3724/SP.J.1146.2007.00491
Abstract:
A turbo-type scheme that uses parallel concatenation and Turbo Block Decision Feedback Equalization (TBDFE) is proposed for transmission over linear intersymbol interference channels. The scheme can offer significant improvement in performance. However, the performance gain is even higher when the detector uses an imperfect channel estimate. In the case of SNR mismatch, both TBDFE and IBDFE algorithms are more sensitive to SNR overestimation than underestimation.
A turbo-type scheme that uses parallel concatenation and Turbo Block Decision Feedback Equalization (TBDFE) is proposed for transmission over linear intersymbol interference channels. The scheme can offer significant improvement in performance. However, the performance gain is even higher when the detector uses an imperfect channel estimate. In the case of SNR mismatch, both TBDFE and IBDFE algorithms are more sensitive to SNR overestimation than underestimation.
2008, 30(10): 2397-2401.
doi: 10.3724/SP.J.1146.2007.00390
Abstract:
This paper presents an improved maximum a posteriori probability (MAP) decoding algorithm for optimal decoding of parallel concatenated convolutional codes (Turbo codes). Compared with the Log-MAP algorithms based on logarithm domain, the proposed algorithm does not introduce logarithm domain, but it can eliminate large amount of exponential and logarithm arithmetic operations required with the standard MAP algorithm in the iterative decoding process. Simulations demonstrate that he proposed algorithm, with optimal error correction performance, can significantly reduce the running time, such that its decoding efficiency is even slightly superior to that of the fastest logarithm domain MAP algorithm(Max-Log-MAP) which sacrifices considerable error correction performance.
This paper presents an improved maximum a posteriori probability (MAP) decoding algorithm for optimal decoding of parallel concatenated convolutional codes (Turbo codes). Compared with the Log-MAP algorithms based on logarithm domain, the proposed algorithm does not introduce logarithm domain, but it can eliminate large amount of exponential and logarithm arithmetic operations required with the standard MAP algorithm in the iterative decoding process. Simulations demonstrate that he proposed algorithm, with optimal error correction performance, can significantly reduce the running time, such that its decoding efficiency is even slightly superior to that of the fastest logarithm domain MAP algorithm(Max-Log-MAP) which sacrifices considerable error correction performance.
2008, 30(10): 2402-2406.
doi: 10.3724/SP.J.1146.2007.01970
Abstract:
Research on roaming management is a very important part for mobile multimedia broadcasting services. However, both OMA (Open Mobile Alliance) and 3GPP (3rd Generation Partnership Project) just give a brief description without further study, all of the signaling for authentication and subscription returning to the home server,which prolongs the transmission time and adds the cost, so the quality of experience may get worse. This paper provides a new approach to optimize the roaming service flow and set the cache on the visiting server to store the keys and subscription information. This approach shortens the transmission time and improves users experience. The calculation and analysis demonstrate that the new approach for roaming management increases the transmission efficiency and makes much better improvement on performance than the existing approach.
Research on roaming management is a very important part for mobile multimedia broadcasting services. However, both OMA (Open Mobile Alliance) and 3GPP (3rd Generation Partnership Project) just give a brief description without further study, all of the signaling for authentication and subscription returning to the home server,which prolongs the transmission time and adds the cost, so the quality of experience may get worse. This paper provides a new approach to optimize the roaming service flow and set the cache on the visiting server to store the keys and subscription information. This approach shortens the transmission time and improves users experience. The calculation and analysis demonstrate that the new approach for roaming management increases the transmission efficiency and makes much better improvement on performance than the existing approach.
2008, 30(10): 2407-2410.
doi: 10.3724/SP.J.1146.2007.00411
Abstract:
To address the problem that TCP performance degrades significantly on the Satellite communication networks, a new transport control protocol, TP-Satellite is introduced. In order to increase the Congestion Window (cwnd) rapidly at the beginning of data transmission, the traditional Slow Start strategy is replaced by a new strategy, named as Super Start. In order to decouple congestion decision from errors, a new scheme, which is based on two class priority IP packets alternately sending, is included in TP-Satellite. Bandwidth asymmetry problem is addressed by adoption of a ACK periodically sending strategy. Theoretical analyses and simulations indicate that TP-Satellite can increase the sending rate rapidly, discriminate the reason of packet loss effectively, enhance throughput performance significantly, and reduce the bandwidth used in the reverse path sharply.
To address the problem that TCP performance degrades significantly on the Satellite communication networks, a new transport control protocol, TP-Satellite is introduced. In order to increase the Congestion Window (cwnd) rapidly at the beginning of data transmission, the traditional Slow Start strategy is replaced by a new strategy, named as Super Start. In order to decouple congestion decision from errors, a new scheme, which is based on two class priority IP packets alternately sending, is included in TP-Satellite. Bandwidth asymmetry problem is addressed by adoption of a ACK periodically sending strategy. Theoretical analyses and simulations indicate that TP-Satellite can increase the sending rate rapidly, discriminate the reason of packet loss effectively, enhance throughput performance significantly, and reduce the bandwidth used in the reverse path sharply.
2008, 30(10): 2411-2414.
doi: 10.3724/SP.J.1146.2007.00471
Abstract:
A LEO global traffic model is first built, then four access and handoff strategies for LEO satellite communication are proposed, and these strategies performance, including call blocking probability and call termination probability, is evaluated through computer simulation. Based on the simple average weighted scheme, a QoS based average weighted scheme is proposed according to the characteristics of the topography and traffic density all over the world. The simulation results show that the proposed scheme can reduce Call Blocking Probability (CBP) and Call Dropping Probability (CDP) considerably.
A LEO global traffic model is first built, then four access and handoff strategies for LEO satellite communication are proposed, and these strategies performance, including call blocking probability and call termination probability, is evaluated through computer simulation. Based on the simple average weighted scheme, a QoS based average weighted scheme is proposed according to the characteristics of the topography and traffic density all over the world. The simulation results show that the proposed scheme can reduce Call Blocking Probability (CBP) and Call Dropping Probability (CDP) considerably.
2008, 30(10): 2415-2418.
doi: 10.3724/SP.J.1146.2007.00560
Abstract:
In Orthogonal Frequency Division Multiplexing (OFDM) systems, there are large estimate errors of the received power in a traditional Automatic Gain Control (AGC). This paper proposes a distribution-function-based AGC method. This method estimates the received power by using the distribution function of the output signal from the Analog to Digital Converter (ADC), and overcomes the clipping effect introduced by the ADC. Simulation results demonstrate that, in OFDM systems, only after one time estimate, the proposed AGC method achieves less than 0.23dB estimate error, whereas the traditional AGC method provides less than 9dB estimate error. Therefore, the proposed AGC method estimates the received power more accurately, and increases greatly the system performance.
In Orthogonal Frequency Division Multiplexing (OFDM) systems, there are large estimate errors of the received power in a traditional Automatic Gain Control (AGC). This paper proposes a distribution-function-based AGC method. This method estimates the received power by using the distribution function of the output signal from the Analog to Digital Converter (ADC), and overcomes the clipping effect introduced by the ADC. Simulation results demonstrate that, in OFDM systems, only after one time estimate, the proposed AGC method achieves less than 0.23dB estimate error, whereas the traditional AGC method provides less than 9dB estimate error. Therefore, the proposed AGC method estimates the received power more accurately, and increases greatly the system performance.
2008, 30(10): 2419-2422.
doi: 10.3724/SP.J.1146.2007.00487
Abstract:
A non-unitary precoding system based on codebook for multi-user MIMO downlink transmission with limited feedback is proposed in this paper. The proposed scheme will perform scheduling and precoding just according to the limited feedback channel information SINR of each user to enhance the system capacity. A precoder codebook design method is related to Grassmannian line packing criterion and the vectors from the Grassmannian codebook are grouped into non-unitary matrices according to their correlation coefficient, which aims to enhance the precoding gain and suppress the multi-user co-channel interference. It has the advantages of low feedback as well as low complexity and outperforms the traditional single user MIMO system and the unitary precoding system based on codebook for multi-user MIMO under the same situation.
A non-unitary precoding system based on codebook for multi-user MIMO downlink transmission with limited feedback is proposed in this paper. The proposed scheme will perform scheduling and precoding just according to the limited feedback channel information SINR of each user to enhance the system capacity. A precoder codebook design method is related to Grassmannian line packing criterion and the vectors from the Grassmannian codebook are grouped into non-unitary matrices according to their correlation coefficient, which aims to enhance the precoding gain and suppress the multi-user co-channel interference. It has the advantages of low feedback as well as low complexity and outperforms the traditional single user MIMO system and the unitary precoding system based on codebook for multi-user MIMO under the same situation.
2008, 30(10): 2423-2426.
doi: 10.3724/SP.J.1146.2007.00553
Abstract:
High data rates and high mobility-induced Doppler shifts introduce time- and frequency-selectivity in wireless links. Recently, doubly selective channel estimation has attracted much attention. In this paper, using a basis expansion channel model, a scheme based on ideal autocorrelation sequence is proposed for the estimation of doubly selective channel parameters. The training sequences have constant modulus so that large peak-to-average ratio problem can be avoided. It has been shown that the employment of this optimal pilot sequence can minimize Mean-Square Error (MSE) of the channel estimation. Simulation results demonstrate that the peak-to-average ratio of the proposed scheme is considerably improved compared to the existing zero-padding scheme for the same MSE performance.
High data rates and high mobility-induced Doppler shifts introduce time- and frequency-selectivity in wireless links. Recently, doubly selective channel estimation has attracted much attention. In this paper, using a basis expansion channel model, a scheme based on ideal autocorrelation sequence is proposed for the estimation of doubly selective channel parameters. The training sequences have constant modulus so that large peak-to-average ratio problem can be avoided. It has been shown that the employment of this optimal pilot sequence can minimize Mean-Square Error (MSE) of the channel estimation. Simulation results demonstrate that the peak-to-average ratio of the proposed scheme is considerably improved compared to the existing zero-padding scheme for the same MSE performance.
2008, 30(10): 2427-2430.
doi: 10.3724/SP.J.1146.2007.00554
Abstract:
A new method of calculating the angle parameter in FRFT domain based on the eigenfunction of time-varying channel is proposed in this letter for FRFT-OFDM systems. The new scheme can estimate the angle parameter in real time based on the variation of the wireless channel. The relationship between the time-variant frequency of G-eigenfunction and time is approximated by linear function. Both theoretical analysis and computer simulation demonstrate that the new scheme has a low complexity compared with the traditional method. When the number of subcarriers is 128, the new scheme can reduce the complexity by 104 compared with the traditional method. This new scheme has advantage when the Doppler spread is large or the time variation of the channel is fast.
A new method of calculating the angle parameter in FRFT domain based on the eigenfunction of time-varying channel is proposed in this letter for FRFT-OFDM systems. The new scheme can estimate the angle parameter in real time based on the variation of the wireless channel. The relationship between the time-variant frequency of G-eigenfunction and time is approximated by linear function. Both theoretical analysis and computer simulation demonstrate that the new scheme has a low complexity compared with the traditional method. When the number of subcarriers is 128, the new scheme can reduce the complexity by 104 compared with the traditional method. This new scheme has advantage when the Doppler spread is large or the time variation of the channel is fast.
2008, 30(10): 2431-2434.
doi: 10.3724/SP.J.1146.2007.00523
Abstract:
To exploit multi-user diversity for multi-user MIMO system, a scheduling algorithm is proposed based on one-bit feedback information in this paper. It is proved in this paper that the value of threshold is important for the system performance, and the problem how to select the optimum threshold for multi-user MIMO systems is solved through theoretical analysis. Simulation results show that the proposed scheme achieves good performance in terms of the average system spectral efficiency by exploiting the multiuser diversity.
To exploit multi-user diversity for multi-user MIMO system, a scheduling algorithm is proposed based on one-bit feedback information in this paper. It is proved in this paper that the value of threshold is important for the system performance, and the problem how to select the optimum threshold for multi-user MIMO systems is solved through theoretical analysis. Simulation results show that the proposed scheme achieves good performance in terms of the average system spectral efficiency by exploiting the multiuser diversity.
2008, 30(10): 2435-2438.
doi: 10.3724/SP.J.1146.2007.00495
Abstract:
Cognitive UWB technology combines UWB technology and Cognitive Radio (CR) technology. Spectrum detection is one of key modules for Cognitive UWB wireless communication system. Cyclostationary characteristic is ubiquitous in almost all the modulated signals. This paper investigates a new detection method that is Cyclic Spectrum Feature Detection (CSFD). Setting OFDM signal as example, it gives out the software simulation and performance analysis. This Detection method can distinguishes desired signal, noise and interference signal, so it is optical for Cognitive UWB wireless communication system.
Cognitive UWB technology combines UWB technology and Cognitive Radio (CR) technology. Spectrum detection is one of key modules for Cognitive UWB wireless communication system. Cyclostationary characteristic is ubiquitous in almost all the modulated signals. This paper investigates a new detection method that is Cyclic Spectrum Feature Detection (CSFD). Setting OFDM signal as example, it gives out the software simulation and performance analysis. This Detection method can distinguishes desired signal, noise and interference signal, so it is optical for Cognitive UWB wireless communication system.
2008, 30(10): 2439-2441.
doi: 10.3724/SP.J.1146.2007.00494
Abstract:
In this paper, the relation between anti-interferences performances of Transform Domain Communication System(TDCS) and basis functions relational parameters are analyzed theoretically; a method of interferences mitigation one by one based on RAT+FRFT+IFRFT is proposed, it can avoid masking affection of strong jammer on weak jammer，and estimate the circumstance jams exactly; a method of system basis function generation based on sub-basis functions concatenation is proposed, these sub-basis functions are generated by the results of every jam estimation exactly and they are orthogonal with every corresponding jam, the circumstance jams spectrums are mitigated completely from system basis function with the method. The advantage anti-interferences performance and adaptability to communication circumstances for TDCS can be produced with the proposed methods.
In this paper, the relation between anti-interferences performances of Transform Domain Communication System(TDCS) and basis functions relational parameters are analyzed theoretically; a method of interferences mitigation one by one based on RAT+FRFT+IFRFT is proposed, it can avoid masking affection of strong jammer on weak jammer，and estimate the circumstance jams exactly; a method of system basis function generation based on sub-basis functions concatenation is proposed, these sub-basis functions are generated by the results of every jam estimation exactly and they are orthogonal with every corresponding jam, the circumstance jams spectrums are mitigated completely from system basis function with the method. The advantage anti-interferences performance and adaptability to communication circumstances for TDCS can be produced with the proposed methods.
2008, 30(10): 2442-2445.
doi: 10.3724/SP.J.1146.2007.00397
Abstract:
The purpose of the paper is to optimize the pilot symbols in adaptive pilot symbols assisted coded modulation systems and to study the influences of the new algorithm on the whole system performances. A new algorithm is found to determine the interval of pilot symbols according to sampling theory and the second order statistics of fading channels. The partial measure and global measure are defined. The adaptation of the partial measure and the efficiency of the global measure are proved. It is also found that the global measure is a tighter and efficient interval bound.
The purpose of the paper is to optimize the pilot symbols in adaptive pilot symbols assisted coded modulation systems and to study the influences of the new algorithm on the whole system performances. A new algorithm is found to determine the interval of pilot symbols according to sampling theory and the second order statistics of fading channels. The partial measure and global measure are defined. The adaptation of the partial measure and the efficiency of the global measure are proved. It is also found that the global measure is a tighter and efficient interval bound.
2008, 30(10): 2446-2449.
doi: 10.3724/SP.J.1146.2007.00443
Abstract:
A new combined symbol timing and frequency synchronization and channel estimation technique by using the detected data is developed for OFDM systems. Open-loop and closed-loop schemes are described in details. The synchronization information contained in the channel estimated results which is gained by LS channel estimation method is extracted based on the Maximum Likelihood (ML) criterion for synchronization estimation，and then the estimated results of symbol timing and frequency are used to correct the initial estimated channel and make it be more equal to the real channel more. Select appropriate length of the block and the value of feedback factors, the algorithm can be used to tracking the time variable channel.
A new combined symbol timing and frequency synchronization and channel estimation technique by using the detected data is developed for OFDM systems. Open-loop and closed-loop schemes are described in details. The synchronization information contained in the channel estimated results which is gained by LS channel estimation method is extracted based on the Maximum Likelihood (ML) criterion for synchronization estimation，and then the estimated results of symbol timing and frequency are used to correct the initial estimated channel and make it be more equal to the real channel more. Select appropriate length of the block and the value of feedback factors, the algorithm can be used to tracking the time variable channel.
2008, 30(10): 2450-2453.
doi: 10.3724/SP.J.1146.2007.00576
Abstract:
To solve the direction-finding and communication of the micro aerial vehicle in peculiar environment, a new communication and tracking system is proposed. The main idea of this system is that the space-time OFDM signal carrying spatial information is transmitted. The transmitter adopts eight element antennas in this system, which are divided into four arrays to produce multi-beams. There are spatial information and communication message in the signal space of each OFDM subcarrier. The micro aerial vehicle with single antenna could determine the ambiguity resolution of multi-beams with many observed samples to estimate the precision direction of receiver relative to transmitter. This paper presents the geometry of antenna arrays, the space-time signal feeding antenna and the direction-finding algorithm of azimuth and elevation. The performances of bit error rate and direction-finding in the two-dimensional space through Gaussian channel are investigated.
To solve the direction-finding and communication of the micro aerial vehicle in peculiar environment, a new communication and tracking system is proposed. The main idea of this system is that the space-time OFDM signal carrying spatial information is transmitted. The transmitter adopts eight element antennas in this system, which are divided into four arrays to produce multi-beams. There are spatial information and communication message in the signal space of each OFDM subcarrier. The micro aerial vehicle with single antenna could determine the ambiguity resolution of multi-beams with many observed samples to estimate the precision direction of receiver relative to transmitter. This paper presents the geometry of antenna arrays, the space-time signal feeding antenna and the direction-finding algorithm of azimuth and elevation. The performances of bit error rate and direction-finding in the two-dimensional space through Gaussian channel are investigated.
2008, 30(10): 2454-2458.
doi: 10.3724/SP.J.1146.2007.00378
Abstract:
Antenna Selection (AS) technique and Virtual MIMO(VMIMO) technique have been widely used in uplink transmission, where the User Equipment (UE) has two antennas but only one Radio Frequency (RF) link. With a view to fully take the advantages of these two techniques, in this paper we apply the AS technique in the VMIMO system, as VMIMO-AS system. However, when both the VMIMO and the AS are applied, always choose the better antennas from the users to form the VMIMO could not guarantee the optimal performance. In this paper, the UE pairing algorithms for the VMIMO system with antenna selection was studied. Different user pairing algorithms are proposed and their throughput and fairness performance are compared. Simulation results show that the first UE should be selected by using the AS technique. Comparably, the selection of the pairing user does not need the AS process, considering the trade-off between the complexity and performance.
Antenna Selection (AS) technique and Virtual MIMO(VMIMO) technique have been widely used in uplink transmission, where the User Equipment (UE) has two antennas but only one Radio Frequency (RF) link. With a view to fully take the advantages of these two techniques, in this paper we apply the AS technique in the VMIMO system, as VMIMO-AS system. However, when both the VMIMO and the AS are applied, always choose the better antennas from the users to form the VMIMO could not guarantee the optimal performance. In this paper, the UE pairing algorithms for the VMIMO system with antenna selection was studied. Different user pairing algorithms are proposed and their throughput and fairness performance are compared. Simulation results show that the first UE should be selected by using the AS technique. Comparably, the selection of the pairing user does not need the AS process, considering the trade-off between the complexity and performance.
2008, 30(10): 2459-2463.
doi: 10.3724/SP.J.1146.2007.00533
Abstract:
According to the algebraic expression of the S-box in Rijndael algorithm, an algebraic system of multivariate quadratic equations over GF(28) are proposed to describe Rijndael. The variables of S boxes are supposed rationally and the relations between these variables are used to establish equations in this paper. The derived system of multivariate quadratic equations is sparse and overdefined. The key recovery of Rijndael can be regarded as a problem of solving this system. By comparing with other parallel systems, this system has fewer terms and variables. So it has a lower complexity while applying the XSL (eXtended Sparse Linearization) technique.
According to the algebraic expression of the S-box in Rijndael algorithm, an algebraic system of multivariate quadratic equations over GF(28) are proposed to describe Rijndael. The variables of S boxes are supposed rationally and the relations between these variables are used to establish equations in this paper. The derived system of multivariate quadratic equations is sparse and overdefined. The key recovery of Rijndael can be regarded as a problem of solving this system. By comparing with other parallel systems, this system has fewer terms and variables. So it has a lower complexity while applying the XSL (eXtended Sparse Linearization) technique.
2008, 30(10): 2464-2467.
doi: 10.3724/SP.J.1146.2007.00470
Abstract:
Based on the back tracking method and the correlation between input and output of the feedforward function, a new inversion attack is proposed to the feedforward stream cipher model with a linear feedback shift register based on a multiplication circuit by improving Golics inversion attack. The average computational complexity of back tracking method, and the average computational complexity of the new inversion attack are given. In comparison with Golics algorithm, both the space complexity and the average computational complexity of the new algorithm are less than that of Golics.
Based on the back tracking method and the correlation between input and output of the feedforward function, a new inversion attack is proposed to the feedforward stream cipher model with a linear feedback shift register based on a multiplication circuit by improving Golics inversion attack. The average computational complexity of back tracking method, and the average computational complexity of the new inversion attack are given. In comparison with Golics algorithm, both the space complexity and the average computational complexity of the new algorithm are less than that of Golics.
2008, 30(10): 2468-2471.
doi: 10.3724/SP.J.1146.2007.00423
Abstract:
According to the problems of proxy revocation, original signers forgery and proxy misuse in proxy signature, a secure proxy blind signature scheme with proxy revocation is proposed. In phase of signature, by embedding non-blind time-stamp in the Abe-Okamoto partially blind signature, the original signer can revoke delegation whenever necessary and all valid proxy signatures generated earlier can longer be verified. Besides having the basic properties of the proxy signature, the new scheme prevents proxy misuse, original signers forgery and public key substitution attack.
According to the problems of proxy revocation, original signers forgery and proxy misuse in proxy signature, a secure proxy blind signature scheme with proxy revocation is proposed. In phase of signature, by embedding non-blind time-stamp in the Abe-Okamoto partially blind signature, the original signer can revoke delegation whenever necessary and all valid proxy signatures generated earlier can longer be verified. Besides having the basic properties of the proxy signature, the new scheme prevents proxy misuse, original signers forgery and public key substitution attack.
2008, 30(10): 2472-2475.
doi: 10.3724/SP.J.1146.2007.00486
Abstract:
Many of the existing proposed routing protocols could not give well stability and reliability and not fit in the needs for Ad hoc network. Because of the problems of great overhead and the lower stability in Ad hoc routing technology, an improved ant colony algorithm is proposed to study an ant-based Ad hoc routing protocol. Compared with the AODV (Ad hoc On-Demand Distance Vector)routing protocol which is a very mature strategy in Ad hoc study, simulation results show that by bringing the node colony function into play，the improved ant colony routing protocol can reduce the end-to-end delay and the routing overhead and increase the packet delivery rate. The network performances such as the stability and the efficiency are improved effectively.
Many of the existing proposed routing protocols could not give well stability and reliability and not fit in the needs for Ad hoc network. Because of the problems of great overhead and the lower stability in Ad hoc routing technology, an improved ant colony algorithm is proposed to study an ant-based Ad hoc routing protocol. Compared with the AODV (Ad hoc On-Demand Distance Vector)routing protocol which is a very mature strategy in Ad hoc study, simulation results show that by bringing the node colony function into play，the improved ant colony routing protocol can reduce the end-to-end delay and the routing overhead and increase the packet delivery rate. The network performances such as the stability and the efficiency are improved effectively.
2008, 30(10): 2476-2480.
doi: 10.3724/SP.J.1146.2007.00463
Abstract:
The cross-layer adaptive problem for OFDM systems is researched. In order to overcome the problem that the present resource allocation algorithms do not consider frequency efficiency, impartiality and QoS simultaneously, a cross-layer adaptive algorithm based on the minimal mean delay time is proposed in this paper, which considers Channel State Information(CSI) and queue information simultaneously. The algorithm uses the utility theory in economics, and considers the mean delay time as optimal quantity to ensure QoS for different services. The algorithm also uses utility function to ensure the impartiality of different delay times and QoS. The simulation results show that the delay time of the proposed algorithm is slightly better than that of LWDF, and is very better than these of PF and EXP. Moreover, it can ensure the impartiality of delay time, and is applicable to the communications those are sensitive to delay time.
The cross-layer adaptive problem for OFDM systems is researched. In order to overcome the problem that the present resource allocation algorithms do not consider frequency efficiency, impartiality and QoS simultaneously, a cross-layer adaptive algorithm based on the minimal mean delay time is proposed in this paper, which considers Channel State Information(CSI) and queue information simultaneously. The algorithm uses the utility theory in economics, and considers the mean delay time as optimal quantity to ensure QoS for different services. The algorithm also uses utility function to ensure the impartiality of different delay times and QoS. The simulation results show that the delay time of the proposed algorithm is slightly better than that of LWDF, and is very better than these of PF and EXP. Moreover, it can ensure the impartiality of delay time, and is applicable to the communications those are sensitive to delay time.
2008, 30(10): 2481-2485.
doi: 10.3724/SP.J.1146.2007.00359
Abstract:
The Instant Messaging inter-working model based on Petri nets is set up to verify the mapping between SIMPLE and IMPS by a new universal coupling criteria of Petri nets model. After the strict mathematical analysis and verification for the model, which prove that the model meets all properties of a correct Petri nets model, the mapping is proved to be reasonable and viable.
The Instant Messaging inter-working model based on Petri nets is set up to verify the mapping between SIMPLE and IMPS by a new universal coupling criteria of Petri nets model. After the strict mathematical analysis and verification for the model, which prove that the model meets all properties of a correct Petri nets model, the mapping is proved to be reasonable and viable.
2008, 30(10): 2486-2489.
doi: 10.3724/SP.J.1146.2007.00478
Abstract:
A typical flow for SIP message exchange is studied, reasons that cause performance degradation are mainly analyzed, and an optimized algorithm that randomly makes the decision of acceptance or rejection of every packet is proposed for overload control of SIP signaling network. The algorithm is verified and analyzed with simulation, and the results show that this solution can restrain throughput jitter, lower service refuse rate, reduce buffer queue length, shorten call setup time and better meet the demand on SIP signaling network under heavy load.
A typical flow for SIP message exchange is studied, reasons that cause performance degradation are mainly analyzed, and an optimized algorithm that randomly makes the decision of acceptance or rejection of every packet is proposed for overload control of SIP signaling network. The algorithm is verified and analyzed with simulation, and the results show that this solution can restrain throughput jitter, lower service refuse rate, reduce buffer queue length, shorten call setup time and better meet the demand on SIP signaling network under heavy load.
2008, 30(10): 2490-2493.
doi: 10.3724/SP.J.1146.2007.00460
Abstract:
Major defensive mechanisms against DoS attacks in the Internet are reviewed. Especially the most recent capabilities techniques, such as basic concepts, stateless flow filtering and the Traffic Validation Architecture (TVA), are analyzed deeply. The related discussions about the shortcomings of current capabilities techniques, such as potential Denial-of-Capability (DoC) attacks, decrement of transmission efficiency, are given in detail. Some improvement methods are provided. They include protecting capabilities requests with notifications, bi-level capabilities, flexible and dynamical capabilities assignment, etc. These methods enhance the robustness and efficiency of capabilities. Theoretical evaluations and simulations show that the improvements outperform original schemes and are more practical in the Internet.
Major defensive mechanisms against DoS attacks in the Internet are reviewed. Especially the most recent capabilities techniques, such as basic concepts, stateless flow filtering and the Traffic Validation Architecture (TVA), are analyzed deeply. The related discussions about the shortcomings of current capabilities techniques, such as potential Denial-of-Capability (DoC) attacks, decrement of transmission efficiency, are given in detail. Some improvement methods are provided. They include protecting capabilities requests with notifications, bi-level capabilities, flexible and dynamical capabilities assignment, etc. These methods enhance the robustness and efficiency of capabilities. Theoretical evaluations and simulations show that the improvements outperform original schemes and are more practical in the Internet.
2008, 30(10): 2494-2498.
doi: 10.3724/SP.J.1146.2007.00459
Abstract:
Wireless sensor networks congestion often leads to increasing network latency, decreasing throughput and wasting the limited sensor node energy. In this paper, an energy-efficient congestion control scheme, which can alleviate congestion in wireless sensor networks, is proposed. The scheme includes hop-by-hop congestion message feedback and rate adjustment. Node periodically samples its queue occupancy and the packet rates of its upstream neighbors, and infers whether congestion will occur in the current time interval. Upon receiving the congestion feedback, these upstream nodes decrease their rate according to their local queue occupancies. Furthermore, sink adjusts the source rate related to some event which is beyond or below the application fidelity. The simulation results show that the proposed scheme is more effective and energy-efficient in congestion alleviation than CODA.
Wireless sensor networks congestion often leads to increasing network latency, decreasing throughput and wasting the limited sensor node energy. In this paper, an energy-efficient congestion control scheme, which can alleviate congestion in wireless sensor networks, is proposed. The scheme includes hop-by-hop congestion message feedback and rate adjustment. Node periodically samples its queue occupancy and the packet rates of its upstream neighbors, and infers whether congestion will occur in the current time interval. Upon receiving the congestion feedback, these upstream nodes decrease their rate according to their local queue occupancies. Furthermore, sink adjusts the source rate related to some event which is beyond or below the application fidelity. The simulation results show that the proposed scheme is more effective and energy-efficient in congestion alleviation than CODA.
2008, 30(10): 2499-2502.
doi: 10.3724/SP.J.1146.2007.00451
Abstract:
In this paper, a WAN network traffic prediction model based on wavelet transform and FIR neural networks is proposed. The model employs wavelet transform which decomposes the traffic into high frequency coefficients and low frequency coefficients , then these different frequency coefficients are reconstructed by single branch to the high frequency traffic parts and the low frequency traffic parts which are sent individually into different FIR neural networks for prediction. The synthesized outputs are the predicted results of the original network traffic. The experimental results with the real WAN network traffic show that the proposed model has much better prediction performance compared to the wavelet neural networks and the FIR neural networks.
In this paper, a WAN network traffic prediction model based on wavelet transform and FIR neural networks is proposed. The model employs wavelet transform which decomposes the traffic into high frequency coefficients and low frequency coefficients , then these different frequency coefficients are reconstructed by single branch to the high frequency traffic parts and the low frequency traffic parts which are sent individually into different FIR neural networks for prediction. The synthesized outputs are the predicted results of the original network traffic. The experimental results with the real WAN network traffic show that the proposed model has much better prediction performance compared to the wavelet neural networks and the FIR neural networks.
2008, 30(10): 2503-2506.
doi: 10.3724/SP.J.1146.2007.00562
Abstract:
This paper proposed a new algorithm called K2K (KPI to KQI) based on algorithm which had been proposed by TMF (Telemanagement Forum) proposes a general algorithm about how to map the key performance indicator (KPI) to the key quality indicator (KQI). K2K algorithm aggregates kinds of indicators to one single significative indicator to express the whole network status. However the algorithm provided by TMF only aggregates the same unit, so it couldnt extract few key indicators to express the whole network healthy status. K2K algorithm had been implemented in practice. It could express the real running status of systems.
This paper proposed a new algorithm called K2K (KPI to KQI) based on algorithm which had been proposed by TMF (Telemanagement Forum) proposes a general algorithm about how to map the key performance indicator (KPI) to the key quality indicator (KQI). K2K algorithm aggregates kinds of indicators to one single significative indicator to express the whole network status. However the algorithm provided by TMF only aggregates the same unit, so it couldnt extract few key indicators to express the whole network healthy status. K2K algorithm had been implemented in practice. It could express the real running status of systems.
2008, 30(10): 2507-2511.
doi: 10.3724/SP.J.1146.2007.00360
Abstract:
TPR-tree is the most popular indexing method for the current and future position of moving objects. In this paper, a new indexing method, ETPR-tree, which takes into account the distribution of both velocity domain and space domain is presented. First the velocity domain is split, and moving objects are classified into different velocity buckets by their velocities, thus the moving objects in one bucket have similar velocities. Then TPR-tree is used to index the moving objects in each bucket. Experimental results show that ETPR-tree update and query performance outperform any other indexing method including TPR*-tree.
TPR-tree is the most popular indexing method for the current and future position of moving objects. In this paper, a new indexing method, ETPR-tree, which takes into account the distribution of both velocity domain and space domain is presented. First the velocity domain is split, and moving objects are classified into different velocity buckets by their velocities, thus the moving objects in one bucket have similar velocities. Then TPR-tree is used to index the moving objects in each bucket. Experimental results show that ETPR-tree update and query performance outperform any other indexing method including TPR*-tree.
2008, 30(10): 2512-2515.
doi: 10.3724/SP.J.1146.2007.00493
Abstract:
A new document relevance calculating method based on lexical cohesion is presented in this paper. The main principle is: documents are formalized with lexicon chains which are constructed by extracting semantic-relative word clusters according to the lexicon cohesion principle under the help of semantic dictionary HowNet; then weight of each lexical chain is evaluated; finally relevance of documents is calculated with their representations. Experiments are conducted on corpus of Chinese Library Classification, and precision about 85.4% is achieved. The experimental results show that the method describes the semantic feature of documents to a certain extent, and it is an effective method for relevance calculating of documents.
A new document relevance calculating method based on lexical cohesion is presented in this paper. The main principle is: documents are formalized with lexicon chains which are constructed by extracting semantic-relative word clusters according to the lexicon cohesion principle under the help of semantic dictionary HowNet; then weight of each lexical chain is evaluated; finally relevance of documents is calculated with their representations. Experiments are conducted on corpus of Chinese Library Classification, and precision about 85.4% is achieved. The experimental results show that the method describes the semantic feature of documents to a certain extent, and it is an effective method for relevance calculating of documents.
2008, 30(10): 2516-2519.
doi: 10.3724/SP.J.1146.2007.00552
Abstract:
Based on the analysis of the Empirical Mode Decomposition (EMD) method, an improved algorithm for signal processing in IR optical gas detection is presented. It decomposes only frequency-modulated signal without need to decompose every Intrinsic Mode Function (IMF) component. Compared with the methods of low-pass filter and digital lock-in amplifier, the improved algorithm has advantages of short data set, fast computation speed and less signal energy loss. It is more effective and time-saving than the conventional EMD method. The changes of gas concentration can be diagnosed by the algorithm and the precision can be improved at the same time. Thereby the gas concentration can be determined accurately and efficiently and it is suitable for real-time detection.
Based on the analysis of the Empirical Mode Decomposition (EMD) method, an improved algorithm for signal processing in IR optical gas detection is presented. It decomposes only frequency-modulated signal without need to decompose every Intrinsic Mode Function (IMF) component. Compared with the methods of low-pass filter and digital lock-in amplifier, the improved algorithm has advantages of short data set, fast computation speed and less signal energy loss. It is more effective and time-saving than the conventional EMD method. The changes of gas concentration can be diagnosed by the algorithm and the precision can be improved at the same time. Thereby the gas concentration can be determined accurately and efficiently and it is suitable for real-time detection.
2008, 30(10): 2520-2524.
doi: 10.3724/SP.J.1146.2007.00479
Abstract:
HFSS is used to simulate helical, contrawound helix and coupled-cavity Slow-Wave Structures(SWS), which work in Ka-band, to investigate the backward-wave oscillation of millimeter-wave TWT. The results show that, space harmonics, which axial space harmonic number and azimuth space harmonic number are unequal, are evident in helical SWS, the SWS runs a risk of backward oscillation near the mode. Relatively, contrawound helix shows excellent ability in restraining backward oscillation by improving interaction impedance and the normalized frequency which can work without backward oscillation. And coupled-cavity should avoid working around those frequencies where phase shifts per cavity are or 2.
HFSS is used to simulate helical, contrawound helix and coupled-cavity Slow-Wave Structures(SWS), which work in Ka-band, to investigate the backward-wave oscillation of millimeter-wave TWT. The results show that, space harmonics, which axial space harmonic number and azimuth space harmonic number are unequal, are evident in helical SWS, the SWS runs a risk of backward oscillation near the mode. Relatively, contrawound helix shows excellent ability in restraining backward oscillation by improving interaction impedance and the normalized frequency which can work without backward oscillation. And coupled-cavity should avoid working around those frequencies where phase shifts per cavity are or 2.
2008, 30(10): 2525-2528.
doi: 10.3724/SP.J.1146.2007.00550
Abstract:
Approximated Maximum Likelihood (AML) estimator has been shown to be the best performance in short sampling wideband sources DOA estimation. However, the computation burden of AML is very large. In order to resolve the question of computation burden, Markov Monte Carlo methods are combined with Approximated Maximum Likelihood DOA estimator. A novel Approximated Maximum Likelihood DOA Estimator based on Gibbs Sampling (AMLGS) is proposed. AMLGS not only keeps the excellent performance of the original AML, but also reduces the computation greatly, from the computational complexityO(LK) of original method to O(KJNs).
Approximated Maximum Likelihood (AML) estimator has been shown to be the best performance in short sampling wideband sources DOA estimation. However, the computation burden of AML is very large. In order to resolve the question of computation burden, Markov Monte Carlo methods are combined with Approximated Maximum Likelihood DOA estimator. A novel Approximated Maximum Likelihood DOA Estimator based on Gibbs Sampling (AMLGS) is proposed. AMLGS not only keeps the excellent performance of the original AML, but also reduces the computation greatly, from the computational complexityO(LK) of original method to O(KJNs).
2008, 30(10): 2529-2532.
doi: 10.3724/SP.J.1146.2007.00383
Abstract:
Since the frequency stability of radio transmitter is high, the error of the carrier frequency is very small, and it is hard to obtain the individual stability difference using traditional approaches due to their low frequency extraction precision. In this paper, the stability of carrier frequency is used as the fine-grained characteristics of the individual communication transmitter based on the stability analysis. After that, the techniques of extracting frequency stability are well discussed, three approaches are put forward which can extract the fine-grained feature by some special processing the carrier signals. On the basis of analyzing principles of these methods, simulation and practical signals experiments are carried out, and the experimental results show that these approaches are effective.
Since the frequency stability of radio transmitter is high, the error of the carrier frequency is very small, and it is hard to obtain the individual stability difference using traditional approaches due to their low frequency extraction precision. In this paper, the stability of carrier frequency is used as the fine-grained characteristics of the individual communication transmitter based on the stability analysis. After that, the techniques of extracting frequency stability are well discussed, three approaches are put forward which can extract the fine-grained feature by some special processing the carrier signals. On the basis of analyzing principles of these methods, simulation and practical signals experiments are carried out, and the experimental results show that these approaches are effective.
2008, 30(10): 2533-2536.
doi: 10.3724/SP.J.1146.2007.00546
Abstract:
How to deploy efficiently sonobuoys is important in air ASW. The Genetic Algorithm(GA) is applied to sonobuoys deployment with reasonable crossover, mutation and the fitness function. A simulation is present to compare detection probability of sonobuoys array between produced by GA and standard method, and the results indicates that the GA can achieve a significant improvement in detection probability.
How to deploy efficiently sonobuoys is important in air ASW. The Genetic Algorithm(GA) is applied to sonobuoys deployment with reasonable crossover, mutation and the fitness function. A simulation is present to compare detection probability of sonobuoys array between produced by GA and standard method, and the results indicates that the GA can achieve a significant improvement in detection probability.
2008, 30(10): 2537-2540.
doi: 10.3724/SP.J.1146.2007.01490
Abstract:
This paper proposes one channel estimation scheme for multiuser MC DS-CDMA systems. Based on the averaged channel estimation in time domain, the averaged channel estimation in frequency domain is used to improve further the performance of channel estimation. The simulation results show that the averaged channel estimation in time domain could largely filter out the Multiple Access Interference (MAI) and noise and improve the accuracy of channel estimation. Followed by one averaged channel estimation in frequency domain, the BER performance of systems still has further improvement. After two times of channel estimation, the system performance approximates to that of the ideal channel estimation.
This paper proposes one channel estimation scheme for multiuser MC DS-CDMA systems. Based on the averaged channel estimation in time domain, the averaged channel estimation in frequency domain is used to improve further the performance of channel estimation. The simulation results show that the averaged channel estimation in time domain could largely filter out the Multiple Access Interference (MAI) and noise and improve the accuracy of channel estimation. Followed by one averaged channel estimation in frequency domain, the BER performance of systems still has further improvement. After two times of channel estimation, the system performance approximates to that of the ideal channel estimation.
