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2012 Vol. 34, No. 11
Display Method:
2012, 34(11): 2541-2547.
doi: 10.3724/SP.J.1146.2012.00547
Abstract:
The single hydrophone matched field localization for non-cooperative underwater acoustic pulse signals is studied. The frequency of underwater acoustic pulse signals is firstly estimated by means of designing the time-frequency distribution with adaptive radially-gaussian kernel according to the characteristic of nonstationary and short duration transient of underwater acoustic pulse signals. And then the ocean channel impulse can be calculated from an acoustic propagation model. Using the received signal of single hydrophone and the ocean channel pulse response, the replica signal for every grid location over search region can be estimated employing the least squares solution in the time domain. Finally, matched field localization of using single hydrophone for non-cooperative underwater acoustic pulse signals is realized by comparing the difference between the received signal and the replica signal yielding the ambiguity surface of localizer function. Simulation and sea-experiment results demonstrate the effectiveness of the proposed method.
The single hydrophone matched field localization for non-cooperative underwater acoustic pulse signals is studied. The frequency of underwater acoustic pulse signals is firstly estimated by means of designing the time-frequency distribution with adaptive radially-gaussian kernel according to the characteristic of nonstationary and short duration transient of underwater acoustic pulse signals. And then the ocean channel impulse can be calculated from an acoustic propagation model. Using the received signal of single hydrophone and the ocean channel pulse response, the replica signal for every grid location over search region can be estimated employing the least squares solution in the time domain. Finally, matched field localization of using single hydrophone for non-cooperative underwater acoustic pulse signals is realized by comparing the difference between the received signal and the replica signal yielding the ambiguity surface of localizer function. Simulation and sea-experiment results demonstrate the effectiveness of the proposed method.
2012, 34(11): 2548-2553.
doi: 10.3724/SP.J.1146.2012.00411
Abstract:
The impulsive interference occurred in the received signals causes bad performance in signal processing. Thus noise should be suppressed. In this paper, a novel method based on polarization analysis is proposed to reject transient noise. With the polarization parameters of the vector signals, a polarization filter is built up. When the filter is applied to the received signals, the impulsive interferences are wiped off at the same time. The data segments contaminated by the interference are found out via the modulate function of the polarization filter, and then the polarization model is used to reconstruct the signal segments. The validity of the suggested approach is demonstrated by simulation results and experiment data.
The impulsive interference occurred in the received signals causes bad performance in signal processing. Thus noise should be suppressed. In this paper, a novel method based on polarization analysis is proposed to reject transient noise. With the polarization parameters of the vector signals, a polarization filter is built up. When the filter is applied to the received signals, the impulsive interferences are wiped off at the same time. The data segments contaminated by the interference are found out via the modulate function of the polarization filter, and then the polarization model is used to reconstruct the signal segments. The validity of the suggested approach is demonstrated by simulation results and experiment data.
2012, 34(11): 2554-2560.
doi: 10.3724/SP.J.1146.2012.00347
Abstract:
In the current Compressed Sensing (CS) theory, signal reconstruction depends on presetting an appropriate sparsifying dictionary. For signals characterized by parametric models, this dictionary is known to be a parameterized dictionary of a certain form, but the values of the parameters are difficult to determine. If the parameters are set to a group of uniform grid points, the mismatch between the assumed and the actual sparsifying dictionaries will cause the performance of conventional CS reconstruction methods to degrade considerably. To address this, a CS reconstruction method that utilizes dynamic dictionaries is proposed. By iteratively optimizing dictionary parameters, the method refines the dictionary dynamically during signal reconstruction. To achieve joint sparse recovery and dictionary refinement, the method alternates between steps of signal coefficients estimation and dictionary parameters optimization under the framework of the variational Expectation-Maximization (EM) algorithm. Experimental results demonstrate the effectiveness of the proposed method.
In the current Compressed Sensing (CS) theory, signal reconstruction depends on presetting an appropriate sparsifying dictionary. For signals characterized by parametric models, this dictionary is known to be a parameterized dictionary of a certain form, but the values of the parameters are difficult to determine. If the parameters are set to a group of uniform grid points, the mismatch between the assumed and the actual sparsifying dictionaries will cause the performance of conventional CS reconstruction methods to degrade considerably. To address this, a CS reconstruction method that utilizes dynamic dictionaries is proposed. By iteratively optimizing dictionary parameters, the method refines the dictionary dynamically during signal reconstruction. To achieve joint sparse recovery and dictionary refinement, the method alternates between steps of signal coefficients estimation and dictionary parameters optimization under the framework of the variational Expectation-Maximization (EM) algorithm. Experimental results demonstrate the effectiveness of the proposed method.
2012, 34(11): 2561-2567.
doi: 10.3724/SP.J.1146.2012.00510
Abstract:
Traditional example based audio retrieval algorithms use forward index, with which, retrieval processing need to traverse the whole database, resulting in intolerable response time. This paper proposes an inverted-index based audio retrieval method. Through constructing super-vector comprising several audio features, audio stream is first segmented into short segments with small feature fluctuation; Based on a pre-trained audio word dictionary, short audio segment sequence is then transformed into audio word sequence, from which inverted index is constructed; During the retrieval phase, the query audio sample is transformed into audio words and retrieval is carried out, candidate segments are ranked according to the similarity with the query. Match term ranking, same type ratio, overlap ratio and retrieval time are used to evaluate the performance of the proposed algorithm. The experiment gives 92.58% retrieval precision within average response time of 1.101 s.
Traditional example based audio retrieval algorithms use forward index, with which, retrieval processing need to traverse the whole database, resulting in intolerable response time. This paper proposes an inverted-index based audio retrieval method. Through constructing super-vector comprising several audio features, audio stream is first segmented into short segments with small feature fluctuation; Based on a pre-trained audio word dictionary, short audio segment sequence is then transformed into audio word sequence, from which inverted index is constructed; During the retrieval phase, the query audio sample is transformed into audio words and retrieval is carried out, candidate segments are ranked according to the similarity with the query. Match term ranking, same type ratio, overlap ratio and retrieval time are used to evaluate the performance of the proposed algorithm. The experiment gives 92.58% retrieval precision within average response time of 1.101 s.
2012, 34(11): 2568-2573.
doi: 10.3724/SP.J.1146.2012.00646
Abstract:
Multi-view stereo angle is the key factor for FTV (Free-viewpoint TV) acquisition/stereo display. A multi-view stereo angle model is established. With the model, factors which impact on stereo angle can be found out. Using stereo angle model, multi-view stereo display system can be simulated quantitatively and the relationship between shooting distance and stereo angle is shown. Depending on formula for max fusion limit of human eyes，relationship among max stereo angle, shooting distance and viewing distance can be got. Finally relationship between stereo angle and number of views can be found. The simulation experiments have been verified above results. This results provide a theoretical basis for optimizing multi-view acquisition/stereo display system.
Multi-view stereo angle is the key factor for FTV (Free-viewpoint TV) acquisition/stereo display. A multi-view stereo angle model is established. With the model, factors which impact on stereo angle can be found out. Using stereo angle model, multi-view stereo display system can be simulated quantitatively and the relationship between shooting distance and stereo angle is shown. Depending on formula for max fusion limit of human eyes，relationship among max stereo angle, shooting distance and viewing distance can be got. Finally relationship between stereo angle and number of views can be found. The simulation experiments have been verified above results. This results provide a theoretical basis for optimizing multi-view acquisition/stereo display system.
2012, 34(11): 2574-2581.
doi: 10.3724/SP.J.1146.2012.00548
Abstract:
To solve the problem of strong randomicity and high memory cost of fast retrieval method Locality Sensitive Hashing (LSH) based on random projection, a fast retrieval method is presented based on multi table frequent items voting and bucket map chain on the basis of Exact Euclidean Locality Sensitive Hashing (E2LSH). The method constructs an index matrix with retrieval vectors, and performs frequent items voting and calibration on this matrix to decrease the randomocity. It also reduces the number of points loaded into memory by making use of the data partition property of E2LSH to decrease the memory cost. The experiments show that this method can decrease the randomicity and efficiently reduce the memory cost of retrieval. This is very important for increasing the feasibility of large scale information retrieval especially image retrieval.
To solve the problem of strong randomicity and high memory cost of fast retrieval method Locality Sensitive Hashing (LSH) based on random projection, a fast retrieval method is presented based on multi table frequent items voting and bucket map chain on the basis of Exact Euclidean Locality Sensitive Hashing (E2LSH). The method constructs an index matrix with retrieval vectors, and performs frequent items voting and calibration on this matrix to decrease the randomocity. It also reduces the number of points loaded into memory by making use of the data partition property of E2LSH to decrease the memory cost. The experiments show that this method can decrease the randomicity and efficiently reduce the memory cost of retrieval. This is very important for increasing the feasibility of large scale information retrieval especially image retrieval.
2012, 34(11): 2582-2586.
doi: 10.3724/SP.J.1146.2012.00610
Abstract:
Radio Frequency IDentification (RFID) tag search protocols are used in a situation where an reader finds a specific tag among multiple tags, which play important roles in many RFID applications. However, the existing protocols either have security weaknesses or exhibit poor efficiency. In this paper, a server-less RFID tag secure search protocol is proposed, which utilizes hash function and timestamp. GNY logic is used to prove its correctness. Analysis shows that presented protocol can be used to search a particular tag efficiently, and preserve tags privacy against all major attacks.
Radio Frequency IDentification (RFID) tag search protocols are used in a situation where an reader finds a specific tag among multiple tags, which play important roles in many RFID applications. However, the existing protocols either have security weaknesses or exhibit poor efficiency. In this paper, a server-less RFID tag secure search protocol is proposed, which utilizes hash function and timestamp. GNY logic is used to prove its correctness. Analysis shows that presented protocol can be used to search a particular tag efficiently, and preserve tags privacy against all major attacks.
2012, 34(11): 2587-2593.
doi: 10.3724/SP.J.1146.2012.00441
Abstract:
Compared with the traditional strip map mode, as a new imaging mode, Circular Scanning SAR (CSSAR) can be used to perform imaging with a wider area in a shorter time. However, due to the influence of the circular orbit, it is difficult to obtain the two-dimension spectrum of the target echo signal which brings a lot of obstacles to the following imaging processing. Thus, a new method for CSSAR imaging based on series reversion is proposed in this paper. By unfolding the Doppler frequency, the stationary phase point expansion coefficients are obtained, making it easy to access the signals two-dimension spectrum, through which range compression and range cell migration correction can be implemented effectively. Furthermore, the accuracy of the spectrum is controlled by keeping enough terms in the two series expansions, which is helpful to the imaging analysis and the following processing. Finally, the feasibility of the proposed approach is validated with the point target simulations and the comparison results.
Compared with the traditional strip map mode, as a new imaging mode, Circular Scanning SAR (CSSAR) can be used to perform imaging with a wider area in a shorter time. However, due to the influence of the circular orbit, it is difficult to obtain the two-dimension spectrum of the target echo signal which brings a lot of obstacles to the following imaging processing. Thus, a new method for CSSAR imaging based on series reversion is proposed in this paper. By unfolding the Doppler frequency, the stationary phase point expansion coefficients are obtained, making it easy to access the signals two-dimension spectrum, through which range compression and range cell migration correction can be implemented effectively. Furthermore, the accuracy of the spectrum is controlled by keeping enough terms in the two series expansions, which is helpful to the imaging analysis and the following processing. Finally, the feasibility of the proposed approach is validated with the point target simulations and the comparison results.
2012, 34(11): 2594-2600.
doi: 10.3724/SP.J.1146.2012.00377
Abstract:
Different signal acquisitions and imaging algorithms have been presented for the wide swath imaging. However, most of these methods used in ScanSAR and Terrain Observation by Progressive scans SAR (TOPSAR) decrease the azimuth resolution for the whole scene. To mitigate this issue, a new lateral swing mode for wide swath imaging is proposed. With the angle of the beam changing, the sparse representation is used to deal with the high bandwidth caused by the wide swath coverage, being the tradeoff against the azimuth resolution, and then the proposed algorithm can produce the unambiguous imaging for the wideswath scene. The simulation results validate the presented approach, which preserves the high resolution in the center of the scene for the wide swath imaging.
Different signal acquisitions and imaging algorithms have been presented for the wide swath imaging. However, most of these methods used in ScanSAR and Terrain Observation by Progressive scans SAR (TOPSAR) decrease the azimuth resolution for the whole scene. To mitigate this issue, a new lateral swing mode for wide swath imaging is proposed. With the angle of the beam changing, the sparse representation is used to deal with the high bandwidth caused by the wide swath coverage, being the tradeoff against the azimuth resolution, and then the proposed algorithm can produce the unambiguous imaging for the wideswath scene. The simulation results validate the presented approach, which preserves the high resolution in the center of the scene for the wide swath imaging.
2012, 34(11): 2601-2607.
doi: 10.3724/SP.J.1146.2012.00298
Abstract:
The UWB radar is a promising technique in fire rescue operations, police awareness, urban-warfare, life-threatening and other fields for noncontact measurement of the tracking and imaging of moving persons behind walls. Based on the UWB short-pulse through-wall radar, a strategy of the topology of the MIMO array is illustrated and the modified Kirchhoff algorithm is applied to slow-moving persons real-time imaging using a simple but effective imaging procedure. A video-like radar image with 5 Hz imaging rates is provided. Simulation results indicate that the topology of the MIMO array is useful for the through-wall radar system. The laboratory experiments are conducted to validate that the proposed imaging procedure is feasible and effective for slow-moving persons real-time imaging. The reasonable moving target trajectory can be obtained after the tracking and filtering process using the imaging results.
The UWB radar is a promising technique in fire rescue operations, police awareness, urban-warfare, life-threatening and other fields for noncontact measurement of the tracking and imaging of moving persons behind walls. Based on the UWB short-pulse through-wall radar, a strategy of the topology of the MIMO array is illustrated and the modified Kirchhoff algorithm is applied to slow-moving persons real-time imaging using a simple but effective imaging procedure. A video-like radar image with 5 Hz imaging rates is provided. Simulation results indicate that the topology of the MIMO array is useful for the through-wall radar system. The laboratory experiments are conducted to validate that the proposed imaging procedure is feasible and effective for slow-moving persons real-time imaging. The reasonable moving target trajectory can be obtained after the tracking and filtering process using the imaging results.
2012, 34(11): 2608-2614.
doi: 10.3724/SP.J.1146.2012.00724
Abstract:
The Blind Speed Side Lobes (BSSL) may increase the false alarm probability and deteriorate the detection performance of the long time coherent integration method, namely, the Radon-Fourier Transform (RFT). A novel BSSL suppression method based on the design of radar Pulse Recurrence Interval (PRI) is proposed. First, detailed PRI design method is given based on the BSSL locations and velocity resolutions. Then, by jointly processing the RFT outputs of two adjacent Coherent Processing Inlervals (CPIs), the BSSL suppression can be realized without deteriorating the integration performance of the RFT. Finally, detailed numerical experiments are provided to demonstrate the effectiveness of the proposed method.
The Blind Speed Side Lobes (BSSL) may increase the false alarm probability and deteriorate the detection performance of the long time coherent integration method, namely, the Radon-Fourier Transform (RFT). A novel BSSL suppression method based on the design of radar Pulse Recurrence Interval (PRI) is proposed. First, detailed PRI design method is given based on the BSSL locations and velocity resolutions. Then, by jointly processing the RFT outputs of two adjacent Coherent Processing Inlervals (CPIs), the BSSL suppression can be realized without deteriorating the integration performance of the RFT. Finally, detailed numerical experiments are provided to demonstrate the effectiveness of the proposed method.
2012, 34(11): 2615-2620.
doi: 10.3724/SP.J.1146.2012.00582
Abstract:
A method of miss distance parameters estimation by utilizing simultaneously Doppler frequency and range information is proposed. According to the noise covariance of measured data, the proposed method first deals with Doppler frequency and range information of echo through the non-linear weighted data fusion, and establishes the corresponding cost function of least squares process, then utilizes the nonlinear optimization method to solve the miss distance parameters. The improvement of estimation performance of the proposed method, compared with the single observable measurement, Doppler frequency or range information, is illustrated by the theoretical derivation of Cramr-Rao Lower Bound (CRLB). Meanwhile, numerical calculation of CRLB is used to analyze the estimation performance. Finally, the computer simulation verifies the validity of the method.
A method of miss distance parameters estimation by utilizing simultaneously Doppler frequency and range information is proposed. According to the noise covariance of measured data, the proposed method first deals with Doppler frequency and range information of echo through the non-linear weighted data fusion, and establishes the corresponding cost function of least squares process, then utilizes the nonlinear optimization method to solve the miss distance parameters. The improvement of estimation performance of the proposed method, compared with the single observable measurement, Doppler frequency or range information, is illustrated by the theoretical derivation of Cramr-Rao Lower Bound (CRLB). Meanwhile, numerical calculation of CRLB is used to analyze the estimation performance. Finally, the computer simulation verifies the validity of the method.
2012, 34(11): 2621-2627.
doi: 10.3724/SP.J.1146.2012.00043
Abstract:
Due to wide beam and low angular accuracy for VHF radar, distributed coherent arrays are proposed for aperture extension and high angular accuracy, which is based on interferometric radar principles and 2-dimensional Direction Of Arrival (DOA) estimation algorithms. Coherently combining distributed subarrays results in grating lobes and angular ambiguities for the baselines greater than subarray apertures between the phase centers of the subarrays. Two-dimensional DOA estimations with high accuracy are accomplished by dual-size unitary ESPRIT algorithm for angular ambiguities resolution and the proposed azimuth-elevation pairing algorithm based on asymptotical orthogonality between signal space and noise space. Then distributed coherent arrays achieve effectively a large equivalent aperture. The threshold effect is analyzed with Method of Interval Error (MIE) and simple approximation computering methods for fillfactor threshold and SNR threshold are derived. Simulation results are presented verifying the effectiveness of the two-dimensional DOA estimation algorithm and high angular accuracy of the distributed coherent arrays.
Due to wide beam and low angular accuracy for VHF radar, distributed coherent arrays are proposed for aperture extension and high angular accuracy, which is based on interferometric radar principles and 2-dimensional Direction Of Arrival (DOA) estimation algorithms. Coherently combining distributed subarrays results in grating lobes and angular ambiguities for the baselines greater than subarray apertures between the phase centers of the subarrays. Two-dimensional DOA estimations with high accuracy are accomplished by dual-size unitary ESPRIT algorithm for angular ambiguities resolution and the proposed azimuth-elevation pairing algorithm based on asymptotical orthogonality between signal space and noise space. Then distributed coherent arrays achieve effectively a large equivalent aperture. The threshold effect is analyzed with Method of Interval Error (MIE) and simple approximation computering methods for fillfactor threshold and SNR threshold are derived. Simulation results are presented verifying the effectiveness of the two-dimensional DOA estimation algorithm and high angular accuracy of the distributed coherent arrays.
2012, 34(11): 2628-2634.
doi: 10.3724/SP.J.1146.2012.00448
Abstract:
An unsupervised classification algorithm established on the Bayesian Information Criterion (BIC) is presented for Polarimetric and Interferometric SAR (PolInSAR) images. First, an initial classification result is obtained by using Shannon entropy characteristic. Then, the result is optimized by Expectation-Maximization (EM) iteration algorithm and LabelCost optimization algorithm. Meanwhile, the method uses BIC to determine the number of clusters automatically. The experimental results show that the proposed method can not only obtain satisfied classification results, but also automatically determine the number of clusters.
An unsupervised classification algorithm established on the Bayesian Information Criterion (BIC) is presented for Polarimetric and Interferometric SAR (PolInSAR) images. First, an initial classification result is obtained by using Shannon entropy characteristic. Then, the result is optimized by Expectation-Maximization (EM) iteration algorithm and LabelCost optimization algorithm. Meanwhile, the method uses BIC to determine the number of clusters automatically. The experimental results show that the proposed method can not only obtain satisfied classification results, but also automatically determine the number of clusters.
2012, 34(11): 2635-2641.
doi: 10.3724/SP.J.1146.2012.00407
Abstract:
Combination of the interferometric theory and MIMO radar with simplified vector sensors, a novel algorithm for joint Direction Of Departure (DOD), Direction Of Arrival (DOA) and polarization estimation in the interferometric MIMO radar with vector sensors is proposed. A short baseline and long baseline of the transmitting array are utilized to obtain high accuracy DOD estimation via the multiresolution ESPRIT. Similarly, the high accuracy DOA estimation can be obtained by utilizing the simplified vector sensor receive array. The polarization rotational invariant, which is irrespective of array geometry, is utilized to estimate the auxiliary polarization angle and polarization phase difference. Finally, the closed-form Cramr-Rao bound under the stochastic signal model is derived. The proposed system can obtain the waveform diversity offered by MIMO radar and the polarization diversity offered by vector sensor simultaneously. And it is capable of extending array aperture without increasing sensors and hardware costs, which can improve the angle estimation accuracy greatly. Moreover, the mutual coupling is decreased via using simplified vector sensor instead of traditional vector sensor, which makes the proposed system easier to implement. Simulation results verify the effectiveness of the proposed algorithm for multiple parameters estimation.
Combination of the interferometric theory and MIMO radar with simplified vector sensors, a novel algorithm for joint Direction Of Departure (DOD), Direction Of Arrival (DOA) and polarization estimation in the interferometric MIMO radar with vector sensors is proposed. A short baseline and long baseline of the transmitting array are utilized to obtain high accuracy DOD estimation via the multiresolution ESPRIT. Similarly, the high accuracy DOA estimation can be obtained by utilizing the simplified vector sensor receive array. The polarization rotational invariant, which is irrespective of array geometry, is utilized to estimate the auxiliary polarization angle and polarization phase difference. Finally, the closed-form Cramr-Rao bound under the stochastic signal model is derived. The proposed system can obtain the waveform diversity offered by MIMO radar and the polarization diversity offered by vector sensor simultaneously. And it is capable of extending array aperture without increasing sensors and hardware costs, which can improve the angle estimation accuracy greatly. Moreover, the mutual coupling is decreased via using simplified vector sensor instead of traditional vector sensor, which makes the proposed system easier to implement. Simulation results verify the effectiveness of the proposed algorithm for multiple parameters estimation.
2012, 34(11): 2642-2647.
doi: 10.3724/SP.J.1146.2012.00148
Abstract:
In this paper, three aspects which are the orbital eccentricity, the ellipsoidal earth model and the Earths self-rotation are considered to calculate the accurate values of Doppler centroid and Doppler FM rate of spaceborne SAR. Since the 2-D attitude steering is necessary for Geo-SAR, this paper analyzes the Doppler parameters with and without the attitude steering respectively next. The conclusions are proved as the effective approach with high practicality for the Doppler parameter estimation of Geo-SAR. The analytical expressions of Doppler can be used for the spaceborne SAR at any orbital altitude with any space resolution, and the accuracy is high. Based on the conclusion, the Doppler centroid and Doppler FM rate properties of Geo-SAR moving in elliptical orbit are analyzed.
In this paper, three aspects which are the orbital eccentricity, the ellipsoidal earth model and the Earths self-rotation are considered to calculate the accurate values of Doppler centroid and Doppler FM rate of spaceborne SAR. Since the 2-D attitude steering is necessary for Geo-SAR, this paper analyzes the Doppler parameters with and without the attitude steering respectively next. The conclusions are proved as the effective approach with high practicality for the Doppler parameter estimation of Geo-SAR. The analytical expressions of Doppler can be used for the spaceborne SAR at any orbital altitude with any space resolution, and the accuracy is high. Based on the conclusion, the Doppler centroid and Doppler FM rate properties of Geo-SAR moving in elliptical orbit are analyzed.
2012, 34(11): 2648-2653.
doi: 10.3724/SP.J.1146.2012.00540
Abstract:
The signal structure of China Mobile Multimedia Broadcasting (CMMB) is significantly different from Europe Digital Video Broadcasting-Terrestrial (DVB-T) signal, which implies that the CMMB-based passive bistatic radar faces some new problems in signal processing methods and real-time parallel computation. In accordance with the signal structure of CMMB, this paper proposes a coherent integration method based on nonuniform sampling which is inherently easy to be implemented parallelly. The internal mechanism and processing procedure are clarified first. Then its resolution and sidelobe performance are demonstrated. Finally, real-life data processing confirms the effectiveness of the proposed method.
The signal structure of China Mobile Multimedia Broadcasting (CMMB) is significantly different from Europe Digital Video Broadcasting-Terrestrial (DVB-T) signal, which implies that the CMMB-based passive bistatic radar faces some new problems in signal processing methods and real-time parallel computation. In accordance with the signal structure of CMMB, this paper proposes a coherent integration method based on nonuniform sampling which is inherently easy to be implemented parallelly. The internal mechanism and processing procedure are clarified first. Then its resolution and sidelobe performance are demonstrated. Finally, real-life data processing confirms the effectiveness of the proposed method.
2012, 34(11): 2654-2659.
doi: 10.3724/SP.J.1146.2012.00400
Abstract:
Characteristics of Unintentional Modulation On Pulse (UMOP) are key and fundamental for radar Specific Emitter Identification (SEI). In this paper, the common used unintentional frequency and phase modulation features are compared with the consideration of Doppler effect. Under the assumptions of Gaussian White Noise (GWN) and moderate to high Signal-to-Noise Ratio (SNR) level, a simplified observation model of the intrapulse phase is presented. Feature definition is carried out, based on the analysis of existing feature extraction procedure. Then the separabilities of features are theoretically compared by using a criterion derived from intra-class and inter-class scatter matrixes. Result shows that the unintentional phase modulation on pulse feature is more robust to noise. This result is validated by simulations and real SEI tests with 104 radar instances.
Characteristics of Unintentional Modulation On Pulse (UMOP) are key and fundamental for radar Specific Emitter Identification (SEI). In this paper, the common used unintentional frequency and phase modulation features are compared with the consideration of Doppler effect. Under the assumptions of Gaussian White Noise (GWN) and moderate to high Signal-to-Noise Ratio (SNR) level, a simplified observation model of the intrapulse phase is presented. Feature definition is carried out, based on the analysis of existing feature extraction procedure. Then the separabilities of features are theoretically compared by using a criterion derived from intra-class and inter-class scatter matrixes. Result shows that the unintentional phase modulation on pulse feature is more robust to noise. This result is validated by simulations and real SEI tests with 104 radar instances.
2012, 34(11): 2660-2665.
doi: 10.3724/SP.J.1146.2012.00381
Abstract:
In this paper, the shortcomings of traditional methods for wave motions removing are analyzed and an iterative method for ocean surface current retrieval by Along-Track Interferometric SAR (ATI-SAR) based on a microwave ocean imaging simulation model is developed. This iterative model is used to obtain the ocean surface current using the JPL AIRSAR ATI-SAR data. The retrieved surface current is compared with the output of Princeton Ocean Model (POM). Both surface currents are in good agreement with each other, which proves the effectiveness of this iterative inversion method.
In this paper, the shortcomings of traditional methods for wave motions removing are analyzed and an iterative method for ocean surface current retrieval by Along-Track Interferometric SAR (ATI-SAR) based on a microwave ocean imaging simulation model is developed. This iterative model is used to obtain the ocean surface current using the JPL AIRSAR ATI-SAR data. The retrieved surface current is compared with the output of Princeton Ocean Model (POM). Both surface currents are in good agreement with each other, which proves the effectiveness of this iterative inversion method.
2012, 34(11): 2666-2671.
doi: 10.3724/SP.J.1146.2012.00577
Abstract:
A novel classification method of hyperspectral image based on sparse representation is proposed. First, the training data is used to design a structured dictionary, and a classification model of hyperspectral image is built based on sparse representation; Then the spatial correlation and the spatial information of training data are added to improve the accuracy of this model; Finally it is solved by the rapid alternating direction method of multipliers. The experimental results show that the proposed method can improve the classification results, and the results are stable.
A novel classification method of hyperspectral image based on sparse representation is proposed. First, the training data is used to design a structured dictionary, and a classification model of hyperspectral image is built based on sparse representation; Then the spatial correlation and the spatial information of training data are added to improve the accuracy of this model; Finally it is solved by the rapid alternating direction method of multipliers. The experimental results show that the proposed method can improve the classification results, and the results are stable.
2012, 34(11): 2672-2679.
doi: 10.3724/SP.J.1146.2012.00859
Abstract:
Because of the shortage of noise removal and small target preservation for the conventional three- dimensional Otsu (3D-Otsu) method, a new method based on adaptive Gaussian weighted directional window is proposed. The new method improves the window setting method of the 3D-Otsu. The window size, scale and filtering direction are adaptively determined by the local characters. Then, based on the proposed non-local multiple directions similarity measurement, the pattern redundancy in the image can be captured effectively. Finally, the 3D histogram is constructed based on the gray value, weighted mean value and weighted median value, and the threshold vector is computed by the maximum between-class variance method to segment the image. Compared with the commonly-used 2D Otsu method, 2D max-entropy method and 3D-Otsu method, the proposed method has better segmentation performance, with better performance for noise removal and small target preservation.
Because of the shortage of noise removal and small target preservation for the conventional three- dimensional Otsu (3D-Otsu) method, a new method based on adaptive Gaussian weighted directional window is proposed. The new method improves the window setting method of the 3D-Otsu. The window size, scale and filtering direction are adaptively determined by the local characters. Then, based on the proposed non-local multiple directions similarity measurement, the pattern redundancy in the image can be captured effectively. Finally, the 3D histogram is constructed based on the gray value, weighted mean value and weighted median value, and the threshold vector is computed by the maximum between-class variance method to segment the image. Compared with the commonly-used 2D Otsu method, 2D max-entropy method and 3D-Otsu method, the proposed method has better segmentation performance, with better performance for noise removal and small target preservation.
2012, 34(11): 2680-2686.
doi: 10.3724/SP.J.1146.2012.00342
Abstract:
Signcryption combines the functionalities of signature and encryption and costs less than that required by the traditional signature-then-encryption approach. On the basis of Li et al. (2010) attribute-based signature, a new attributes-based signcryption is proposed in this paper, in which not only confidentiality and authentication is provided but also attribute-signcryptor privacy and multi-recipient is achieved. This scheme is provable secure in the random oracle model and it satisfies indistinguishability against adaptive chosen ciphertext attack based on Decisional Bilinear Diffie-Hellman (DBDH) assumption and satisfies existential unforgeability against adaptive chosen message attack based on the standard Computational Diffie-Hellman (CDH) assumption.
Signcryption combines the functionalities of signature and encryption and costs less than that required by the traditional signature-then-encryption approach. On the basis of Li et al. (2010) attribute-based signature, a new attributes-based signcryption is proposed in this paper, in which not only confidentiality and authentication is provided but also attribute-signcryptor privacy and multi-recipient is achieved. This scheme is provable secure in the random oracle model and it satisfies indistinguishability against adaptive chosen ciphertext attack based on Decisional Bilinear Diffie-Hellman (DBDH) assumption and satisfies existential unforgeability against adaptive chosen message attack based on the standard Computational Diffie-Hellman (CDH) assumption.
2012, 34(11): 2687-2693.
doi: 10.3724/SP.J.1146.2012.00554
Abstract:
Single sparse matrix can not meet the complexity of the compressed sensing process in wireless sensor networks. Cooperative compressed sensing mechanism is proposed in this paper. According to the energy consumption status of nodes, the sparse matrix can be established with the collaborative manner between the nodes. Further, the sparse degrees in the process of data presentation can be improved through the designed redundant dictionary, and robustness of the transmission process is improved. Finally, the purpose of reducing energy consumption can be achieved. Results show that the proposed strategy is effective to prolong the network survival time and greatly improves the accuracy of recovered data.
Single sparse matrix can not meet the complexity of the compressed sensing process in wireless sensor networks. Cooperative compressed sensing mechanism is proposed in this paper. According to the energy consumption status of nodes, the sparse matrix can be established with the collaborative manner between the nodes. Further, the sparse degrees in the process of data presentation can be improved through the designed redundant dictionary, and robustness of the transmission process is improved. Finally, the purpose of reducing energy consumption can be achieved. Results show that the proposed strategy is effective to prolong the network survival time and greatly improves the accuracy of recovered data.
2012, 34(11): 2694-2699.
doi: 10.3724/SP.J.1146.2012.00636
Abstract:
Smart Micro Grid (SMG), the system integrating distributed renewable generation, energy storage devices and intelligent inverter, provides efficient approach to utilize energy and decrease carbon emission. To achieve the reliable automated operation, intelligent control and transmission models should be employed in SMG system. Based on the theory of traffic engineering and distributed agent techniques, this paper proposes a novel Electric Information Flow Multi-QoS Constraints routing algorithm (EIF-MQC) applying to SMG advance measurement infrastructure. A Differentiated Services Code Point (DSCP) mapping model to abstract variety electric information from intelligent electronic devices into different QoS class traffic is designed. EIF-MQC computing optimal routing paths for each QoS class flow. In the paper, the mathematical proof to show the routing path computed by EIF-MQC is the shortest path is presented. Based on the infrastructure of Consortium for Electric Reliability Technology Solutions (CERTS) smart micro grid, the computer simulation to evaluate EIF-MQC is finished, compared with Open Shortest Path First (OSPF) and a routing protocol that is based on Load Balancing and a commonly used Shortest Path Routing protocol (LB-SPR). In both of the light communication load period and severe load ones, EIF-MQC has the excellent performance with balance bandwidth utilization rate, short transmission delay and low loss packets rate, all of which will be benefit to avoid transmitting congestion and improve the capability of Advance Measurement Infrastructure (AMI) system.
Smart Micro Grid (SMG), the system integrating distributed renewable generation, energy storage devices and intelligent inverter, provides efficient approach to utilize energy and decrease carbon emission. To achieve the reliable automated operation, intelligent control and transmission models should be employed in SMG system. Based on the theory of traffic engineering and distributed agent techniques, this paper proposes a novel Electric Information Flow Multi-QoS Constraints routing algorithm (EIF-MQC) applying to SMG advance measurement infrastructure. A Differentiated Services Code Point (DSCP) mapping model to abstract variety electric information from intelligent electronic devices into different QoS class traffic is designed. EIF-MQC computing optimal routing paths for each QoS class flow. In the paper, the mathematical proof to show the routing path computed by EIF-MQC is the shortest path is presented. Based on the infrastructure of Consortium for Electric Reliability Technology Solutions (CERTS) smart micro grid, the computer simulation to evaluate EIF-MQC is finished, compared with Open Shortest Path First (OSPF) and a routing protocol that is based on Load Balancing and a commonly used Shortest Path Routing protocol (LB-SPR). In both of the light communication load period and severe load ones, EIF-MQC has the excellent performance with balance bandwidth utilization rate, short transmission delay and low loss packets rate, all of which will be benefit to avoid transmitting congestion and improve the capability of Advance Measurement Infrastructure (AMI) system.
2012, 34(11): 2700-2706.
doi: 10.3724/SP.J.1146.2012.00491
Abstract:
DataBase Complex Networks (DBCN) is a kind of metric for management information systems, which provides a simplified and visualized description of business logic and a self-introduced documentary. To extract DBCNs, two algorithms are proposed: (1) based on the primary and foreign key associations of database tables algorithm; (2) based on the hidden semanteme associations algorithm and its extension. Through the analysis on 9 software databases, the statistical features of DBCN are investigated and found that in-degree distribution is more disperse than that of out-degree, and tables with greater in-degree are the backbone nodes. In order to accurately construct DBCN to facilitate the software engineering, a group of naming criteria is proposed for hidden semanteme associations.
DataBase Complex Networks (DBCN) is a kind of metric for management information systems, which provides a simplified and visualized description of business logic and a self-introduced documentary. To extract DBCNs, two algorithms are proposed: (1) based on the primary and foreign key associations of database tables algorithm; (2) based on the hidden semanteme associations algorithm and its extension. Through the analysis on 9 software databases, the statistical features of DBCN are investigated and found that in-degree distribution is more disperse than that of out-degree, and tables with greater in-degree are the backbone nodes. In order to accurately construct DBCN to facilitate the software engineering, a group of naming criteria is proposed for hidden semanteme associations.
2012, 34(11): 2707-2714.
doi: 10.3724/SP.J.1146.2012.00508
Abstract:
An Autonomic Energy-Saving Management Mechanism (AESMM) based on autonomic management is proposed for saving energy in wireless cellular networks. Energy-saving model is analyzed firstly, and then procedures of AESMM are introduced. As two key issues of AESMM, regional BS opposite-pair compensation method and autonomic intelligent optimization algorithm for coverage compensation are proposed. Objective is maximizing regional saving energy and meanwhile guaranteeing regional coverage and service quality. AESMM is simulated under WCDMA/HSDPA scenario. Comparing to other two methods adopted in the references, results show that AESMM can save maximal energy (about 17% of regional energy consumption) while keep regional coverage and service quality acceptable.
An Autonomic Energy-Saving Management Mechanism (AESMM) based on autonomic management is proposed for saving energy in wireless cellular networks. Energy-saving model is analyzed firstly, and then procedures of AESMM are introduced. As two key issues of AESMM, regional BS opposite-pair compensation method and autonomic intelligent optimization algorithm for coverage compensation are proposed. Objective is maximizing regional saving energy and meanwhile guaranteeing regional coverage and service quality. AESMM is simulated under WCDMA/HSDPA scenario. Comparing to other two methods adopted in the references, results show that AESMM can save maximal energy (about 17% of regional energy consumption) while keep regional coverage and service quality acceptable.
2012, 34(11): 2715-2720.
doi: 10.3724/SP.J.1146.2012.00617
Abstract:
Compared with other types of Clos-netwok switch, the Memory-Memory-Memory (MMM) switch minimizes the time required to configure a Clos-network switch. However the use of buffers in the middle stage of an MMM switch can potentially cause the forwarding of cells to the outputs in out-of-sequence order. A novel scheduling algorithm, called Extended Padded Frame (EPF) scheme, is proposed, which provides in-sequence service for MMM Clos-network by adopting a frame-based approach. The new solution adopts a predetermined cyclic shift configuration at the first and third stages and the oldest-cell-first selection for arbitrations at the second stage. The algorithm is decentralized and requires no speedup. Analysis and simulation results show that the new algorithm is stable, that is to say, EPF can achieve 100% throughput under any admissible traffic patterns.
Compared with other types of Clos-netwok switch, the Memory-Memory-Memory (MMM) switch minimizes the time required to configure a Clos-network switch. However the use of buffers in the middle stage of an MMM switch can potentially cause the forwarding of cells to the outputs in out-of-sequence order. A novel scheduling algorithm, called Extended Padded Frame (EPF) scheme, is proposed, which provides in-sequence service for MMM Clos-network by adopting a frame-based approach. The new solution adopts a predetermined cyclic shift configuration at the first and third stages and the oldest-cell-first selection for arbitrations at the second stage. The algorithm is decentralized and requires no speedup. Analysis and simulation results show that the new algorithm is stable, that is to say, EPF can achieve 100% throughput under any admissible traffic patterns.
2012, 34(11): 2721-2727.
doi: 10.3724/SP.J.1146.2012.00364
Abstract:
Providing reliable multicast service in multi-hop wireless network faces many technique challenges, among which packet loss recovery is one of most important issues. In this paper, an efficient packet loss recovery framework is proposed based on random linear network coding in field for reliable multicast in multi-hop wireless networks, called Network Coding Reliable Multicast (NCRM). NCRM overcomes the limitations of the XOR encoding scheme. The original packets are classified into different generations and sent. Repair nodes employ random linear network coding to send encoded packets. A group member who experiences packet loss sends a Negative ACKnowledgement (NACK) with loss bit vector. Through neighborhood recovery, multi-hop recovery and/or source recovery, loss recovery is efficiently fulfilled. A mathematical model of homogeneous Markov chain is constucted to analyze the theoretical delay and average hops of retransmission. Simulation experiments based on NS2 and the numerical results demonstrate that NCRM significantly outperforms Pragmatic General Multicast (PGM) and CoreRM, in terms of network throughput and loss recovery latency.
Providing reliable multicast service in multi-hop wireless network faces many technique challenges, among which packet loss recovery is one of most important issues. In this paper, an efficient packet loss recovery framework is proposed based on random linear network coding in field for reliable multicast in multi-hop wireless networks, called Network Coding Reliable Multicast (NCRM). NCRM overcomes the limitations of the XOR encoding scheme. The original packets are classified into different generations and sent. Repair nodes employ random linear network coding to send encoded packets. A group member who experiences packet loss sends a Negative ACKnowledgement (NACK) with loss bit vector. Through neighborhood recovery, multi-hop recovery and/or source recovery, loss recovery is efficiently fulfilled. A mathematical model of homogeneous Markov chain is constucted to analyze the theoretical delay and average hops of retransmission. Simulation experiments based on NS2 and the numerical results demonstrate that NCRM significantly outperforms Pragmatic General Multicast (PGM) and CoreRM, in terms of network throughput and loss recovery latency.
2012, 34(11): 2728-2733.
doi: 10.3724/SP.J.1146.2012.00603
Abstract:
A hybrid beamforming technology for 60 GHz uplink communication system is proposed in order to compromise between performance and complexity. The beam-switching by a predefined beam codebook is applied at the transmitter, while DOA estimation based on the codebook and the optimum beamforming are used at the receiver. Meanwhile an improved Least Mean Square (LMS) algorithm is designed, which is able to increase the iterative performance effectively by providing the initial value. The simulation results show the hybrid beamforming algorithm, especially the improved LMS, can significantly enhance the SINR performance of receiver signal.
A hybrid beamforming technology for 60 GHz uplink communication system is proposed in order to compromise between performance and complexity. The beam-switching by a predefined beam codebook is applied at the transmitter, while DOA estimation based on the codebook and the optimum beamforming are used at the receiver. Meanwhile an improved Least Mean Square (LMS) algorithm is designed, which is able to increase the iterative performance effectively by providing the initial value. The simulation results show the hybrid beamforming algorithm, especially the improved LMS, can significantly enhance the SINR performance of receiver signal.
2012, 34(11): 2734-2740.
doi: 10.3724/SP.J.1146.2012.00553
Abstract:
With the special requirements of on-board switching for satellite communications, the divide-and- conquer dispatching scheme is proposed based on Memory-Space-Memory (MSM) Clos network switches. By introducing the notion of colliding fields, the matching for a Clos-network is simplified to the problem of how to select cells for central modules within a colliding field, which restricts the scope of collisions, and reduce the complexity of the dispatching. This dispatching scheme has low hardware complexity, and can achieve high performance under various traffic models. Simulation results show that divide-and-conquer dispatching scheme approaches 100% throughput under all the traffic conditions, and has a very low delay, which meets the requirements of satellite communication.
With the special requirements of on-board switching for satellite communications, the divide-and- conquer dispatching scheme is proposed based on Memory-Space-Memory (MSM) Clos network switches. By introducing the notion of colliding fields, the matching for a Clos-network is simplified to the problem of how to select cells for central modules within a colliding field, which restricts the scope of collisions, and reduce the complexity of the dispatching. This dispatching scheme has low hardware complexity, and can achieve high performance under various traffic models. Simulation results show that divide-and-conquer dispatching scheme approaches 100% throughput under all the traffic conditions, and has a very low delay, which meets the requirements of satellite communication.
2012, 34(11): 2741-2747.
doi: 10.3724/SP.J.1146.2012.00466
Abstract:
Wireless relay and network coding are two critical techniques to improve the reliability and increase the throughput for wireless communication systems. The performance analysis and the related optimized design of Complex Field Network Coding (CFNC) scheme in non-orthogonal adaptive Multiple Access Relay Channel (MARC) with Selective Decode-and-Forward (SDF) relaying strategy are presented in this paper. Firstly, the upper bound of the symbol error probability, the diversity order and the coding gains are derived for the CFNC scheme in non-orthogonal adaptive MARC. Then the coding gain is utilized as the optimized criterion to determine the optimal power allocation ratio. Our analysis unveils that, for the CFNC scheme in the context of non-orthogonal MARC, the use of SDF strategy at relay can guarantee the full diversity performance, and achieve better reliability with simpler implementation complexity than the link-adaptive regeneration at the relay. Moreover, the optimized power allocation between all source nodes and the relay may effectively increase the realized coding gain, thus further improving the system reliability.
Wireless relay and network coding are two critical techniques to improve the reliability and increase the throughput for wireless communication systems. The performance analysis and the related optimized design of Complex Field Network Coding (CFNC) scheme in non-orthogonal adaptive Multiple Access Relay Channel (MARC) with Selective Decode-and-Forward (SDF) relaying strategy are presented in this paper. Firstly, the upper bound of the symbol error probability, the diversity order and the coding gains are derived for the CFNC scheme in non-orthogonal adaptive MARC. Then the coding gain is utilized as the optimized criterion to determine the optimal power allocation ratio. Our analysis unveils that, for the CFNC scheme in the context of non-orthogonal MARC, the use of SDF strategy at relay can guarantee the full diversity performance, and achieve better reliability with simpler implementation complexity than the link-adaptive regeneration at the relay. Moreover, the optimized power allocation between all source nodes and the relay may effectively increase the realized coding gain, thus further improving the system reliability.
2012, 34(11): 2748-2754.
doi: 10.3724/SP.J.1146.2012.00424
Abstract:
In practical communication of two-way relay channel, the transmission rate is always asymmetric because of the asymmetric channel quality, transmission power and rate requirement. This paper proposes two schemes of asymmetric transmission based on physical layer network coding. First one is cascaded channel coding, and second one is subset coding and subset modulation. The two schemes take advantage of the linearity of convolutional code so that the relay node can decode directly the superposition signal into the XOR bits. Simulation results show that the asymmetric schemes not only improve the transmission validity by increasing system capacity, but also guarantees the transmission reliability by lowering BER.
In practical communication of two-way relay channel, the transmission rate is always asymmetric because of the asymmetric channel quality, transmission power and rate requirement. This paper proposes two schemes of asymmetric transmission based on physical layer network coding. First one is cascaded channel coding, and second one is subset coding and subset modulation. The two schemes take advantage of the linearity of convolutional code so that the relay node can decode directly the superposition signal into the XOR bits. Simulation results show that the asymmetric schemes not only improve the transmission validity by increasing system capacity, but also guarantees the transmission reliability by lowering BER.
2012, 34(11): 2755-2760.
doi: 10.3724/SP.J.1146.2012.00518
Abstract:
How to achieve precise synchronization is a technical problem that must be addressed in today,s military operations in the highly dynamic conditions. In the conditions, the bit rate offset and carrier frequency offset will affect the precise synchronization accuracy. An improved Pseudo Noise (PN) code phase measurement method based on the least squares method is proposed, and the precise synchronization ability of this method in high-dynamic conditions is proved by theoretical analysis and simulation. The theoretical analysis shows that the method can eliminate the impact of carrier frequency offset and be of strong anti-noise ability. While the numerical simulation manifests that this method is not sensitive to bit rate offset when the length of the selected PN sequence is not very long, and proves that it is of strong anti-frequency offset. The measurement results demonstrate that this method not only achieves a high measurement accuracy, but also possesses good anti-noise and anti-frequency offset ability.
How to achieve precise synchronization is a technical problem that must be addressed in today,s military operations in the highly dynamic conditions. In the conditions, the bit rate offset and carrier frequency offset will affect the precise synchronization accuracy. An improved Pseudo Noise (PN) code phase measurement method based on the least squares method is proposed, and the precise synchronization ability of this method in high-dynamic conditions is proved by theoretical analysis and simulation. The theoretical analysis shows that the method can eliminate the impact of carrier frequency offset and be of strong anti-noise ability. While the numerical simulation manifests that this method is not sensitive to bit rate offset when the length of the selected PN sequence is not very long, and proves that it is of strong anti-frequency offset. The measurement results demonstrate that this method not only achieves a high measurement accuracy, but also possesses good anti-noise and anti-frequency offset ability.
2012, 34(11): 2761-2766.
doi: 10.3724/SP.J.1146.2012.00133
Abstract:
Compressed Sensing (CS) theory provides a new solution for low-rate sampling design of Impulse Radio Ultra-WideBand (IR-UWB) receiver, but the quantization process is usually idealized in existent CS based sampling architectures. In this paper, the influence of quantization noise is fully considered, and an IR-UWB signal reconstruction method with high anti-noise performance is proposed. Based on the analysis of the receiver noise distribution characteristics, the signal reconstruction optimization model is revised, and then the performance of Dantzig-Selector (DS) method is compared with the traditional signal reconstruction algorithms. Further, a joint DS-SP method which can self-adaptively select the reconstruction algorithms between DS and SP (Subspace Pursuit) is proposed. Simulation results show that the joint DS-SP method which has computational complexity trade-off between DS and SP can get the best performance under different noise regions and quantization precisions. Whats more, joint DS-SP has large performance improvement compared to the traditional reconstruction algorithms, thus provides a new strategy of CS signal reconstruction for the design of IR-UWB receivers digital back-end.
Compressed Sensing (CS) theory provides a new solution for low-rate sampling design of Impulse Radio Ultra-WideBand (IR-UWB) receiver, but the quantization process is usually idealized in existent CS based sampling architectures. In this paper, the influence of quantization noise is fully considered, and an IR-UWB signal reconstruction method with high anti-noise performance is proposed. Based on the analysis of the receiver noise distribution characteristics, the signal reconstruction optimization model is revised, and then the performance of Dantzig-Selector (DS) method is compared with the traditional signal reconstruction algorithms. Further, a joint DS-SP method which can self-adaptively select the reconstruction algorithms between DS and SP (Subspace Pursuit) is proposed. Simulation results show that the joint DS-SP method which has computational complexity trade-off between DS and SP can get the best performance under different noise regions and quantization precisions. Whats more, joint DS-SP has large performance improvement compared to the traditional reconstruction algorithms, thus provides a new strategy of CS signal reconstruction for the design of IR-UWB receivers digital back-end.
2012, 34(11): 2767-2773.
doi: 10.3724/SP.J.1146.2012.00165
Abstract:
In order to describe well the nonlinear time-varying characteristics of spectrum occupancy states which has not been related previously, a novel spectrum occupancy state time series modeling method based on Exponential Generalized Auto Regressive Conditional Heteroskedasticity process (EGARCH) is proposed. Firstly, due to the variance of spectrum occupancy Auto Regressive Moving Average (ARMA) time series model through conditional heteroskedasticity test, it is demonstrated that spectrum occupancy time series has volatility clustering characteristics. Secondly, due to the fitting models analysis results based on EGARCH process and monitoring data, the accuracy of fitting and predicting is better than ARMA model. Thirdly, the leverage coefficients of EGARCH model demonstrate that the influence from spectrum occupancy to electromagnetic environment fluctuation is asymmetric. All above results show that EGARCH model quantifies the complicated nonlinear time varying process of spectrum occupancy.
In order to describe well the nonlinear time-varying characteristics of spectrum occupancy states which has not been related previously, a novel spectrum occupancy state time series modeling method based on Exponential Generalized Auto Regressive Conditional Heteroskedasticity process (EGARCH) is proposed. Firstly, due to the variance of spectrum occupancy Auto Regressive Moving Average (ARMA) time series model through conditional heteroskedasticity test, it is demonstrated that spectrum occupancy time series has volatility clustering characteristics. Secondly, due to the fitting models analysis results based on EGARCH process and monitoring data, the accuracy of fitting and predicting is better than ARMA model. Thirdly, the leverage coefficients of EGARCH model demonstrate that the influence from spectrum occupancy to electromagnetic environment fluctuation is asymmetric. All above results show that EGARCH model quantifies the complicated nonlinear time varying process of spectrum occupancy.
2012, 34(11): 2774-2784.
doi: 10.3724/SP.J.1146.2012.00555
Abstract:
Differential Power Analysis (DPA) attacks exploit the data or instruction dependency of the power consumption of the cryptographic devices during encryption/decryption process. A large number of power traces are used to analyze the cipher key information on mathematics statistical methods. DPA attacks have been becoming a great threat to cipher security. In order to systematically and comprehensively understand DPA countermeasures, and actively promote the studying of high performance cryptographic chip, this paper introduces the basic principle of DPA, explains and analyzes the mainstream DPA countermeasures, and points out the advanced topics countermeasures. This paper focuses on the theory of DPA countermeasures, the flow path of algorithm, and the implementation of circuits, including masking technology, hiding technology, power disruption technology and so on. The advantages and disadvantages of these countermeasures are detailed discussed. Finally, the potential research directions and advanced topics on DPA countermeasures are provided.
Differential Power Analysis (DPA) attacks exploit the data or instruction dependency of the power consumption of the cryptographic devices during encryption/decryption process. A large number of power traces are used to analyze the cipher key information on mathematics statistical methods. DPA attacks have been becoming a great threat to cipher security. In order to systematically and comprehensively understand DPA countermeasures, and actively promote the studying of high performance cryptographic chip, this paper introduces the basic principle of DPA, explains and analyzes the mainstream DPA countermeasures, and points out the advanced topics countermeasures. This paper focuses on the theory of DPA countermeasures, the flow path of algorithm, and the implementation of circuits, including masking technology, hiding technology, power disruption technology and so on. The advantages and disadvantages of these countermeasures are detailed discussed. Finally, the potential research directions and advanced topics on DPA countermeasures are provided.
2012, 34(11): 2785-2789.
doi: 10.3724/SP.J.1146.2012.00596
Abstract:
With the maturity of current detecting technology based on high-frequency ground wave radar, current detecting precision has gained increasing attention. This paper aims at discussing the vector current velocity detecting precision of T/Rm-Rb system from the mean square error, and obtaining the optimal operating region of current velocity detecting. Firstly, the vector current velocity is obtained from the radial current velocity measured by T/Rm monostatic radar system and the hyperbolic current velocity measured by T/Rb bistatic radar system. Then the vector current velocity error is calculated from total differential and divided intoⅠtype error andⅡ type error to discuss the mean square error. I type error means the error resulted from the limited Doppler velocity resolution andⅡtype error means the error resulted from the scattering angle observing. Finally, the geometrical dilution of position is drawn and the optimal operating region of current velocity detecting is obtained. That is: the region near the baseline and the bistatic receiver Rbshould be avoided for vector current velocity detection of T/Rm-Rb system.
With the maturity of current detecting technology based on high-frequency ground wave radar, current detecting precision has gained increasing attention. This paper aims at discussing the vector current velocity detecting precision of T/Rm-Rb system from the mean square error, and obtaining the optimal operating region of current velocity detecting. Firstly, the vector current velocity is obtained from the radial current velocity measured by T/Rm monostatic radar system and the hyperbolic current velocity measured by T/Rb bistatic radar system. Then the vector current velocity error is calculated from total differential and divided intoⅠtype error andⅡ type error to discuss the mean square error. I type error means the error resulted from the limited Doppler velocity resolution andⅡtype error means the error resulted from the scattering angle observing. Finally, the geometrical dilution of position is drawn and the optimal operating region of current velocity detecting is obtained. That is: the region near the baseline and the bistatic receiver Rbshould be avoided for vector current velocity detection of T/Rm-Rb system.
2012, 34(11): 2790-2794.
doi: 10.3724/SP.J.1146.2012.00676
Abstract:
An ultra-thin metamaterial absorber is designed and applied to reducing in-band Radar Cross Section (RCS) of waveguide slot antenna. The absorber is consisted solely of two metallic layers separated by a lossy dielectric spacer. In spite of its very thin structure, almost/175, the absorber achieves a maximum absorptivity of 99.9% and shows an excellent absorption stability performance with respect to different polarizations and incidence angles. By analyzing equivalent circuit and simulating the the electric field distribution, current distribution on patch and metallic ground plane at the resonance frequency, its physical mechanism of absorption of the electromagnetic wave is theoretically investigated. Experimental results show that the application of the absorber to waveguide slot antenna has hardly influence on antennas radiation performance, while the in-band RCS reduction of antenna is above 3 dB from21 to 21, and the most reduction value exceeds 17 dB at the boresight direction.
An ultra-thin metamaterial absorber is designed and applied to reducing in-band Radar Cross Section (RCS) of waveguide slot antenna. The absorber is consisted solely of two metallic layers separated by a lossy dielectric spacer. In spite of its very thin structure, almost/175, the absorber achieves a maximum absorptivity of 99.9% and shows an excellent absorption stability performance with respect to different polarizations and incidence angles. By analyzing equivalent circuit and simulating the the electric field distribution, current distribution on patch and metallic ground plane at the resonance frequency, its physical mechanism of absorption of the electromagnetic wave is theoretically investigated. Experimental results show that the application of the absorber to waveguide slot antenna has hardly influence on antennas radiation performance, while the in-band RCS reduction of antenna is above 3 dB from21 to 21, and the most reduction value exceeds 17 dB at the boresight direction.
