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2013 Vol. 35, No. 1
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2013, 35(1): 1-7.
doi: 10.3724/SP.J.1146.2012.00851
Abstract:
In the inverse synthetic aperture radar imaging of ballistic mid-course targets with unsymmetrical appendix parts, the image of the main body may be shadowed by the echo component induced by the unsymmetrical appendix parts. In this paper, the echo model of ballistic mid-course targets with unsymmetrical appendix parts is established, and the micro-Doppler difference between the main body and the appendix parts is analyzed. Then, an algorithm utilizing the Complex-value Empirical Mode Decomposition (CEMD) is proposed to separate the echo of the appendix parts. The echo component of the main body and the appendix parts can be separated and reconstructed with the proposed algorithm adaptively. The results of the simulation verify that a much better image of the main body can be obtained after the separation.
In the inverse synthetic aperture radar imaging of ballistic mid-course targets with unsymmetrical appendix parts, the image of the main body may be shadowed by the echo component induced by the unsymmetrical appendix parts. In this paper, the echo model of ballistic mid-course targets with unsymmetrical appendix parts is established, and the micro-Doppler difference between the main body and the appendix parts is analyzed. Then, an algorithm utilizing the Complex-value Empirical Mode Decomposition (CEMD) is proposed to separate the echo of the appendix parts. The echo component of the main body and the appendix parts can be separated and reconstructed with the proposed algorithm adaptively. The results of the simulation verify that a much better image of the main body can be obtained after the separation.
2013, 35(1): 8-14.
doi: 10.3724/SP.J.1146.2012.00749
Abstract:
A new practical approach for ground fast-moving target detection and imaging is presented for the three-channel SAR-Ground Moving Target Indication (SAR-GMTI) system based on the forward-looking configuration. Considering the facts that fast-moving targets defocus in SAR image and Doppler spectrum folding demands complicated processing, fast-moving targets after clutter suppression are refocused in order to detect these targets, in the procedure of which the Doppler spectrum is adequately compressed before range walk correction which avoids effectively Doppler spectrum folding. The simulation results validate the effectiveness of the approach presented in this paper.
A new practical approach for ground fast-moving target detection and imaging is presented for the three-channel SAR-Ground Moving Target Indication (SAR-GMTI) system based on the forward-looking configuration. Considering the facts that fast-moving targets defocus in SAR image and Doppler spectrum folding demands complicated processing, fast-moving targets after clutter suppression are refocused in order to detect these targets, in the procedure of which the Doppler spectrum is adequately compressed before range walk correction which avoids effectively Doppler spectrum folding. The simulation results validate the effectiveness of the approach presented in this paper.
2013, 35(1): 15-23.
doi: 10.3724/SP.J.1146.2012.01094
Abstract:
The Across Range Unit (ARU) effect, mismatch issue in the matched filter and the aperture fill phenomenon can badly deteriorate the performance of high-speed weak target detection in wideband Digital Array Radar (DAR). To address these issues, a novel long-time coherent integration method, namely, Wideband Space- Time Radon Fourier Transform (WST-RFT) is proposed. Based on the 3D echo model of DAR, the system response function of wideband matched filter is given, and by jointly searching the 3D parameter space, the ARU effect, mismatch problem of the matched filter and the aperture fill phenomenon can be simultaneously addressed. Then, the optimality of the WST-RFT based detector is demonstrated. Furthermore, to solve high computation cost problem caused by ergodic search in the WST-RFT, a fast implementation based on Chirp-Z Transform (CZT) is given. Finally, numerical experiments demonstrate the effectiveness of the proposed method.
The Across Range Unit (ARU) effect, mismatch issue in the matched filter and the aperture fill phenomenon can badly deteriorate the performance of high-speed weak target detection in wideband Digital Array Radar (DAR). To address these issues, a novel long-time coherent integration method, namely, Wideband Space- Time Radon Fourier Transform (WST-RFT) is proposed. Based on the 3D echo model of DAR, the system response function of wideband matched filter is given, and by jointly searching the 3D parameter space, the ARU effect, mismatch problem of the matched filter and the aperture fill phenomenon can be simultaneously addressed. Then, the optimality of the WST-RFT based detector is demonstrated. Furthermore, to solve high computation cost problem caused by ergodic search in the WST-RFT, a fast implementation based on Chirp-Z Transform (CZT) is given. Finally, numerical experiments demonstrate the effectiveness of the proposed method.
2013, 35(1): 24-28.
doi: 10.3724/SP.J.1146.2012.00758
Abstract:
Fierce sea clutter submerges the slow weak target echo which makes the target detection difficult. To address the problem, a Constant False Alarm Rate (CFAR) detection method based on orthogonal projection is proposed in this paper. Utilizing the correlation of the clutter between neighbored range cells, this method suppresses clutter by orthogonal projection at first, and then carries out the CFAR detection. The structure chart of the CFAR detector using orthogonal projection is given. And the performance of clutter suppression and computation amount for orthogonal projection method and singular value decomposition method are compared. Theoretical analysis and simulation results with the experimental data show the superiority of the proposed method.
Fierce sea clutter submerges the slow weak target echo which makes the target detection difficult. To address the problem, a Constant False Alarm Rate (CFAR) detection method based on orthogonal projection is proposed in this paper. Utilizing the correlation of the clutter between neighbored range cells, this method suppresses clutter by orthogonal projection at first, and then carries out the CFAR detection. The structure chart of the CFAR detector using orthogonal projection is given. And the performance of clutter suppression and computation amount for orthogonal projection method and singular value decomposition method are compared. Theoretical analysis and simulation results with the experimental data show the superiority of the proposed method.
2013, 35(1): 29-35.
doi: 10.3724/SP.J.1146.2011.01370
Abstract:
In order to meet the growing demands for high resolution SAR imaging, this paper describes a new single channel transmit, multi-channel parallel receive high resolution SAR system. The system operates with 8 parallel receive channels to obtain a wide bandwidth up to 3.2 GHz, and also features high resolution, InSAR and PolSAR imaging capability. A novel method of transfer error measurement and compensation is presented in the paper. This method based on radiation calibration and frequency shift correction estimation could implement multi-channel amplitude and phase correction effectively. For the first time in China, a resolution of better than 0.1 m is achieved with the airborne SAR system. This paper introduces the architecture and main specifications of the SAR system, and discusses several important aspects of high resolution imaging in detail, including the bandwidth synthesis, transfer error correction, motion compensation and image formation. Flight experiments demonstrate the high resolution imaging capability of the SAR system.
In order to meet the growing demands for high resolution SAR imaging, this paper describes a new single channel transmit, multi-channel parallel receive high resolution SAR system. The system operates with 8 parallel receive channels to obtain a wide bandwidth up to 3.2 GHz, and also features high resolution, InSAR and PolSAR imaging capability. A novel method of transfer error measurement and compensation is presented in the paper. This method based on radiation calibration and frequency shift correction estimation could implement multi-channel amplitude and phase correction effectively. For the first time in China, a resolution of better than 0.1 m is achieved with the airborne SAR system. This paper introduces the architecture and main specifications of the SAR system, and discusses several important aspects of high resolution imaging in detail, including the bandwidth synthesis, transfer error correction, motion compensation and image formation. Flight experiments demonstrate the high resolution imaging capability of the SAR system.
2013, 35(1): 36-40.
doi: 10.3724/SP.J.1146.2012.00669
Abstract:
To reduce the computational complexity of conventional cancellation algorithm in passive radar system, a fast cancellation by the Pseudo-Noise (PN) sequence in the Digital Television Terrestrial Broadcasting (DTTB) illuminator is proposed. Based on the good correlation property of PN sequence, and the fact that DTTB illuminator is very sensitive to the Carrier Frequency Offset (CFO), the 2-D time delay and CFO estimation is proposed to improve the estimation accuracy. Once obtaining the time delay and CFO, the direct path signal reconstruction and cancellation can be made, remaining the target echoed signal and noise. Compared with the conventional cancellation method, the method has the smaller computational cost, and all the processing is on surveillance antenna, simplifying the passive radar system model by removing the reference antenna. Finally, the simulation experiments demonstrate the effectiveness of the method.
To reduce the computational complexity of conventional cancellation algorithm in passive radar system, a fast cancellation by the Pseudo-Noise (PN) sequence in the Digital Television Terrestrial Broadcasting (DTTB) illuminator is proposed. Based on the good correlation property of PN sequence, and the fact that DTTB illuminator is very sensitive to the Carrier Frequency Offset (CFO), the 2-D time delay and CFO estimation is proposed to improve the estimation accuracy. Once obtaining the time delay and CFO, the direct path signal reconstruction and cancellation can be made, remaining the target echoed signal and noise. Compared with the conventional cancellation method, the method has the smaller computational cost, and all the processing is on surveillance antenna, simplifying the passive radar system model by removing the reference antenna. Finally, the simulation experiments demonstrate the effectiveness of the method.
2013, 35(1): 41-48.
doi: 10.3724/SP.J.1146.2012.00764
Abstract:
Multi-channel wideband radar requires not only the ability of high-resolution imaging for wide coverage, but also the ability of moving target detection. This paper proposes a method based on three-channel Terrain Observation by Progressive scan SAR (TOPSAR) mode for Ground Moving Target Indication (GMTI). First of all, the geometric model of the three-channel TOPSAR-GMTI system is established, and then full-aperture imaging method is used for processing the three-channel echo data. After that, the Displaced Phase Center Antenna (DPCA) and Constant False Alarm Rate (CFAR) methods are used to accomplish the detection of moving targets. Finally, the relationship between the interferometric phase and speed is deduced for seeking to estimate the speed of the target and remark its correct position in the SAR image. The results of simulation are provided to demonstrate the effectiveness of the proposed method.
Multi-channel wideband radar requires not only the ability of high-resolution imaging for wide coverage, but also the ability of moving target detection. This paper proposes a method based on three-channel Terrain Observation by Progressive scan SAR (TOPSAR) mode for Ground Moving Target Indication (GMTI). First of all, the geometric model of the three-channel TOPSAR-GMTI system is established, and then full-aperture imaging method is used for processing the three-channel echo data. After that, the Displaced Phase Center Antenna (DPCA) and Constant False Alarm Rate (CFAR) methods are used to accomplish the detection of moving targets. Finally, the relationship between the interferometric phase and speed is deduced for seeking to estimate the speed of the target and remark its correct position in the SAR image. The results of simulation are provided to demonstrate the effectiveness of the proposed method.
2013, 35(1): 49-55.
doi: 10.3724/SP.J.1146.2011.01162
Abstract:
Considering the phase wrapping issue in the cross-range scaling of interferometric ISAR, a novel algorithm of cross-range scaling is proposed based on Randomized Hough Transform (RHT). Using the linear relationship between the azimuth positions derived from the wrapping interferometric phases and the Doppler frequencies of the dominant scatters in ISAR image, the proposed algorithm estimates the scale factor between true azimuth position and Doppler frequency by RHT and determines the ISAR image scale in the cross-range direction, consequently avoiding the complex phase unwrapping procedure. The simulation results verify the validity and anti-noise capability of the proposed algorithm.
Considering the phase wrapping issue in the cross-range scaling of interferometric ISAR, a novel algorithm of cross-range scaling is proposed based on Randomized Hough Transform (RHT). Using the linear relationship between the azimuth positions derived from the wrapping interferometric phases and the Doppler frequencies of the dominant scatters in ISAR image, the proposed algorithm estimates the scale factor between true azimuth position and Doppler frequency by RHT and determines the ISAR image scale in the cross-range direction, consequently avoiding the complex phase unwrapping procedure. The simulation results verify the validity and anti-noise capability of the proposed algorithm.
2013, 35(1): 56-62.
doi: 10.3724/SP.J.1146.2012.00647
Abstract:
This paper aims at analyzing the applicability of the hyperbolic range model meeting resolution higher than one meter for low-earth orbital spaceborne SAR. How long the integration time can the range model be applied to, and the corresponding azimuth resolution are main issues of this paper. An accurate geometry is modeled firstly to get the Doppler centroid and the Doppler FM rate, which have the higher accuracy. Then the accurate range model can be got through the Doppler parameter reversion. The azimuth history phase errors can then be calculated by comparing with the numeric values of the slant range information. If the errors are under the threhold of ,/4 the disfocusing is impossible. Based on the theory above, the parameters of TerraSAR-X are utilized for simulation. The longest integration time and the best resolution got from the hyperbolic range model are analyzed. The conclusion of this paper offers an approach for analyzing the range model of the current low-earth orbital spaceborne SAR.
This paper aims at analyzing the applicability of the hyperbolic range model meeting resolution higher than one meter for low-earth orbital spaceborne SAR. How long the integration time can the range model be applied to, and the corresponding azimuth resolution are main issues of this paper. An accurate geometry is modeled firstly to get the Doppler centroid and the Doppler FM rate, which have the higher accuracy. Then the accurate range model can be got through the Doppler parameter reversion. The azimuth history phase errors can then be calculated by comparing with the numeric values of the slant range information. If the errors are under the threhold of ,/4 the disfocusing is impossible. Based on the theory above, the parameters of TerraSAR-X are utilized for simulation. The longest integration time and the best resolution got from the hyperbolic range model are analyzed. The conclusion of this paper offers an approach for analyzing the range model of the current low-earth orbital spaceborne SAR.
2013, 35(1): 63-67.
doi: 10.3724/SP.J.1146.2012.00012
Abstract:
This paper proposes a new carrier tracking loop based on Extended Kalman Filter (EKF) with no data aided in low Signal-to-Noise Ratio (SNR) and high dynamic environment. It utilizes the outputs of accumulator after symbol decision as the observation matrix of EKF. With this method, the restriction generated by using discriminators in low SNR can be avoided. The simulations show that the structure proposed has excellent characteristics compared with Phase Lock Loop (PLL) and linear Kalman Filter (KF) assisted with phase discriminator.
This paper proposes a new carrier tracking loop based on Extended Kalman Filter (EKF) with no data aided in low Signal-to-Noise Ratio (SNR) and high dynamic environment. It utilizes the outputs of accumulator after symbol decision as the observation matrix of EKF. With this method, the restriction generated by using discriminators in low SNR can be avoided. The simulations show that the structure proposed has excellent characteristics compared with Phase Lock Loop (PLL) and linear Kalman Filter (KF) assisted with phase discriminator.
2013, 35(1): 68-73.
doi: 10.3724/SP.J.1146.2012.00345
Abstract:
In order to solve the problem that it is difficult to acquire high precision angular velocity parameter in airborne passive location based on spatial-frequency domain information, this paper utilizes phase difference rate-of-changes augmentation to angular velocity, and constructs a new passive location measure model by two dimensions interferometer layout. The passive location of air target is realized. For the negative error covariance matrix possibly induces instability in the Unscented Kalman Filter (UKF), the square root UKF is introduced and improved. The Simplex Spherical distribution Unscented Transform (SSUT) is used to sigma sampling. The calculated amount of filtering is reduced by cutting down the number of sampling point. The simulation results show that the position and velocity tracking error of the new measure model decrease under the lower condition of parameters measurement. When the stable tracking effect can be reached, the algorithm efficiency can be enhanced by adopting improved square root UKF.
In order to solve the problem that it is difficult to acquire high precision angular velocity parameter in airborne passive location based on spatial-frequency domain information, this paper utilizes phase difference rate-of-changes augmentation to angular velocity, and constructs a new passive location measure model by two dimensions interferometer layout. The passive location of air target is realized. For the negative error covariance matrix possibly induces instability in the Unscented Kalman Filter (UKF), the square root UKF is introduced and improved. The Simplex Spherical distribution Unscented Transform (SSUT) is used to sigma sampling. The calculated amount of filtering is reduced by cutting down the number of sampling point. The simulation results show that the position and velocity tracking error of the new measure model decrease under the lower condition of parameters measurement. When the stable tracking effect can be reached, the algorithm efficiency can be enhanced by adopting improved square root UKF.
2013, 35(1): 74-79.
doi: 10.3724/SP.J.1146.2012.00631
Abstract:
The issue of poor error-tolerance and polynomial taps restriction of Walsh Hadamard Transform (WHT) estimation method is studied and a novel soft fast PN sequence estimation algorithm based on weighting Walsh Hadamard Transform is proposed in this paper. Firstly, the theory analysis about error-tolerance likelihood bound of sequence hard-decision and restrictive factor of estimation polynomial taps is performed. Based on this analysis, the sequence soft information are taken to sequence frequency-coefficient to improve estimation performance, and the Walsh Hadamard matrix is column-weighted to change its binary property, which can decrease the polynomial taps influence to estimation performance. Meanwhile, the sequence control state are chosen to decease the estimation polynomial taps in the essence. The simulation results show that the proposed method is irrelevant with the order and tapped number of generator polynomial, and its performance is improved 1.5 dB than WHT.
The issue of poor error-tolerance and polynomial taps restriction of Walsh Hadamard Transform (WHT) estimation method is studied and a novel soft fast PN sequence estimation algorithm based on weighting Walsh Hadamard Transform is proposed in this paper. Firstly, the theory analysis about error-tolerance likelihood bound of sequence hard-decision and restrictive factor of estimation polynomial taps is performed. Based on this analysis, the sequence soft information are taken to sequence frequency-coefficient to improve estimation performance, and the Walsh Hadamard matrix is column-weighted to change its binary property, which can decrease the polynomial taps influence to estimation performance. Meanwhile, the sequence control state are chosen to decease the estimation polynomial taps in the essence. The simulation results show that the proposed method is irrelevant with the order and tapped number of generator polynomial, and its performance is improved 1.5 dB than WHT.
2013, 35(1): 80-84.
doi: 10.3724/SP.J.1146.2012.00742
Abstract:
A convex optimization based Khatri-Rao subspace wideband Direction-Of-Arrive (DOA) estimation algorithm is proposed in this paper. First of all, the steering vectors of the virtual array are formulated with the Khatri-Rao subspace. And then these steering vectors of the virtual array are used to compute the wideband focusing matrix with convex optimization. Thanks to the increased dimensions of the virtual array, the proposed focusing matrix can minimize the distortion of the noise caused by the focusing procedure and maintain the good focusing performance as well. Simulations show that the proposed method performs better than the conventional Khatri-Rao subspace wideband DOA estimation algorithm: Focusing Khatri-Rao subspace-Rotational Signal Subspace (FKR-RSS) and when the number of sources is more than the number of sensors, the proposed method has more obvious superiority especially.
A convex optimization based Khatri-Rao subspace wideband Direction-Of-Arrive (DOA) estimation algorithm is proposed in this paper. First of all, the steering vectors of the virtual array are formulated with the Khatri-Rao subspace. And then these steering vectors of the virtual array are used to compute the wideband focusing matrix with convex optimization. Thanks to the increased dimensions of the virtual array, the proposed focusing matrix can minimize the distortion of the noise caused by the focusing procedure and maintain the good focusing performance as well. Simulations show that the proposed method performs better than the conventional Khatri-Rao subspace wideband DOA estimation algorithm: Focusing Khatri-Rao subspace-Rotational Signal Subspace (FKR-RSS) and when the number of sources is more than the number of sensors, the proposed method has more obvious superiority especially.
2013, 35(1): 85-91.
doi: 10.3724/SP.J.1146.2012.00735
Abstract:
In an Alpha stable distribution noise environment, the traditional methods of digital modulation signals recognition have the problems of poor performance. A novel recognition method based on generalized fractional Fourier transform and fractional lower Wigner-Ville distribution is proposed to solve this problem. This method extracts the recognition characteristic parameters which are maximum of normalize and center instantaneous amplitude spectral density based on generalized fractional Fourier transform and maximum of fractional lower Wigner-Ville distribution amplitude. And then the method uses decision tree as a classifier to achieve digital modulation signals recognition. Simulation results show that the proposed method not only has better performance than the traditional recognition methods but also has higher recognition rate and good robustness in an Alpha stable distribution noise environment.
In an Alpha stable distribution noise environment, the traditional methods of digital modulation signals recognition have the problems of poor performance. A novel recognition method based on generalized fractional Fourier transform and fractional lower Wigner-Ville distribution is proposed to solve this problem. This method extracts the recognition characteristic parameters which are maximum of normalize and center instantaneous amplitude spectral density based on generalized fractional Fourier transform and maximum of fractional lower Wigner-Ville distribution amplitude. And then the method uses decision tree as a classifier to achieve digital modulation signals recognition. Simulation results show that the proposed method not only has better performance than the traditional recognition methods but also has higher recognition rate and good robustness in an Alpha stable distribution noise environment.
2013, 35(1): 92-98.
doi: 10.3724/SP.J.1146.2011.01224
Abstract:
The Craomr-Rao Bound (CRB) expression of near-field distance estimation for underwater source is first presented. Furthermore, the CRB of far-field Direction-Of-Arrival (DOA) estimation is deduced. The characteristics and factors of CRB results are shown as following: (1)Both of the distance estimation CRB and the DOA estimation CRB can be divided into two items, one of which is relative to the geometry of array, including array manifold and array aperture, while the other one depends on the signal characteristics, containing source direction, frequency, bandwidth and SNR etc; (2)Both of them are inversely proportional to an item which is composed of bandwidth and spectrum density function; (3)The distance estimation CRB is directly proportional to the forth power of distance; (4)The distance estimation CRB is relative to the position of reference point, while the DOA estimation CRB is not; (5)For Uniform Linear Array (ULA), the distance estimation CRB is close to be inversely proportional to the fifth power of array aperture, and the DOA estimation CRB is close to be inversely proportional to the cube of array aperture; for Uniform Circle Array (UCA), both of them is inversely proportional to the array aperture and independent of source direction. The Monte-Carlo simulation results validate the theoretical analysis and the conclusions. This paper not only presents the best performance of distance estimation and DOA estimation, but also provides the theoretical guidance of array and signal design to achieve the optimum estimation.
The Craomr-Rao Bound (CRB) expression of near-field distance estimation for underwater source is first presented. Furthermore, the CRB of far-field Direction-Of-Arrival (DOA) estimation is deduced. The characteristics and factors of CRB results are shown as following: (1)Both of the distance estimation CRB and the DOA estimation CRB can be divided into two items, one of which is relative to the geometry of array, including array manifold and array aperture, while the other one depends on the signal characteristics, containing source direction, frequency, bandwidth and SNR etc; (2)Both of them are inversely proportional to an item which is composed of bandwidth and spectrum density function; (3)The distance estimation CRB is directly proportional to the forth power of distance; (4)The distance estimation CRB is relative to the position of reference point, while the DOA estimation CRB is not; (5)For Uniform Linear Array (ULA), the distance estimation CRB is close to be inversely proportional to the fifth power of array aperture, and the DOA estimation CRB is close to be inversely proportional to the cube of array aperture; for Uniform Circle Array (UCA), both of them is inversely proportional to the array aperture and independent of source direction. The Monte-Carlo simulation results validate the theoretical analysis and the conclusions. This paper not only presents the best performance of distance estimation and DOA estimation, but also provides the theoretical guidance of array and signal design to achieve the optimum estimation.
2013, 35(1): 99-105.
doi: 10.3724/SP.J.1146.2012.00819
Abstract:
A novel image denoising method is proposed by using non-local approximation of low-rank based on random projection. The cluster of similar patch for each pixel point is found by using methods of non-local searching, and then compute low-rank approximation of matrix corresponding to the cluster of similar patches using two-side random projection. Finally, the image noise is suppressed by using the Low rank structure. Results show that the proposed method have the low computation cost. Comparing with one-side random projection method, the proposed algorithm ensure lower reconstruction error, and comparing with the Block Method of 3-Dimension (BM3D) method, proposed method have appealing visual quality of images.
A novel image denoising method is proposed by using non-local approximation of low-rank based on random projection. The cluster of similar patch for each pixel point is found by using methods of non-local searching, and then compute low-rank approximation of matrix corresponding to the cluster of similar patches using two-side random projection. Finally, the image noise is suppressed by using the Low rank structure. Results show that the proposed method have the low computation cost. Comparing with one-side random projection method, the proposed algorithm ensure lower reconstruction error, and comparing with the Block Method of 3-Dimension (BM3D) method, proposed method have appealing visual quality of images.
2013, 35(1): 106-112.
doi: 10.3724/SP.J.1146.2012.00726
Abstract:
Combining with the new features of the H.264/AVC video coding standard, a new reversible fragile video watermarking algorithm is proposed. The hash value of quantized Discrete Cosine Transform (DCT) coefficients of predictive residue blocks is performed with the proposed algorithm in current macroblock, and the authentication code is created. Then, the authentication code, as watermark is embedded into the last nonzero quantized DCT coefficient in the most active44 block of the next adjacent macroblock. The integrality authentication is carried out in the decoding end by the comparison of the authentication code with the extracted watermark information. The experimental results show that the proposed algorithm has little impact on the video quality and bit-rate, moreover, the original video can be recovered if the authentication is successful and the tampered area of I frame can effectively be located if the authentication fail.
Combining with the new features of the H.264/AVC video coding standard, a new reversible fragile video watermarking algorithm is proposed. The hash value of quantized Discrete Cosine Transform (DCT) coefficients of predictive residue blocks is performed with the proposed algorithm in current macroblock, and the authentication code is created. Then, the authentication code, as watermark is embedded into the last nonzero quantized DCT coefficient in the most active44 block of the next adjacent macroblock. The integrality authentication is carried out in the decoding end by the comparison of the authentication code with the extracted watermark information. The experimental results show that the proposed algorithm has little impact on the video quality and bit-rate, moreover, the original video can be recovered if the authentication is successful and the tampered area of I frame can effectively be located if the authentication fail.
2013, 35(1): 113-118.
doi: 10.3724/SP.J.1146.2012.00799
Abstract:
Most pen-based user interfaces are incapable of recognizing both graphical symbols and text with a single recognizer. Thus, it is essential to distinguish between graphical strokes and textual ones before feeding them into the appropriate recognizer. An approach for classifying sketched strokes is presented using Support Vector Random Field (SVRF). Inputting strokes as well as the interactions among them are jointly modeled by the random field. Not only the unary features of strokes themselves are utilized for discriminative classification, but also their temporal and spatial context are exploited through neighborhood system and features of binary stroke pairs. After applying Loopy Belief Propagation (LBP) inferring, the joint labeling solution according to maximum posterior marginal criterion is estimated. Experimental results show that the classification accuracy of the approach outperforms the Support Vector Machine (SVM) classifier as well as the Markov Random Field (MRF)-based joint classification approach which utilizes spatial context. The speed of classification meets basically the requirement of real-time interaction. Thus the feasibility and effectiveness of the proposed approach are verified.
Most pen-based user interfaces are incapable of recognizing both graphical symbols and text with a single recognizer. Thus, it is essential to distinguish between graphical strokes and textual ones before feeding them into the appropriate recognizer. An approach for classifying sketched strokes is presented using Support Vector Random Field (SVRF). Inputting strokes as well as the interactions among them are jointly modeled by the random field. Not only the unary features of strokes themselves are utilized for discriminative classification, but also their temporal and spatial context are exploited through neighborhood system and features of binary stroke pairs. After applying Loopy Belief Propagation (LBP) inferring, the joint labeling solution according to maximum posterior marginal criterion is estimated. Experimental results show that the classification accuracy of the approach outperforms the Support Vector Machine (SVM) classifier as well as the Markov Random Field (MRF)-based joint classification approach which utilizes spatial context. The speed of classification meets basically the requirement of real-time interaction. Thus the feasibility and effectiveness of the proposed approach are verified.
2013, 35(1): 119-125.
doi: 10.3724/SP.J.1146.2012.00936
Abstract:
Energy efficiency is a primary challenge in wireless body sensor networks for the long-term physical movement monitoring. In order to reduce the energy consumption while maintaining the sufficient classification accuracy of the human activity, a compressed classification approach is explored combining classification with data compressing based on sparse representation and compressed sensing. The proposed approach firstly compresses the sensing data by random projection on the sensor nodes, and then recognizes activities on compressed samples after transmitting to the central node by sparse representation, which can reduce the energy transmission of original data. The performance of the method is evaluated on the opened Wearable Action Recognition Database (WARD). Experimental results are validated that the compressed classifier achieves comparable recognition accuracy on the compressed sensing data.
Energy efficiency is a primary challenge in wireless body sensor networks for the long-term physical movement monitoring. In order to reduce the energy consumption while maintaining the sufficient classification accuracy of the human activity, a compressed classification approach is explored combining classification with data compressing based on sparse representation and compressed sensing. The proposed approach firstly compresses the sensing data by random projection on the sensor nodes, and then recognizes activities on compressed samples after transmitting to the central node by sparse representation, which can reduce the energy transmission of original data. The performance of the method is evaluated on the opened Wearable Action Recognition Database (WARD). Experimental results are validated that the compressed classifier achieves comparable recognition accuracy on the compressed sensing data.
2013, 35(1): 126-132.
doi: 10.3724/SP.J.1146.2012.00602
Abstract:
The substrate link failures have made a great impact on the reliability of Reconfigurable Service Carrying Networks (RSCNs) over Reconfigurable Flexible Network (RFNet). In this paper, the reliability problem of delay-sensitive RSCNs is solved based on a path backup strategy, and a two-stage approach is presented to further reduce the backup resource cost. In the topology preprocessing stage, according to whether the path split is supported by RSCNs, the Splittable Minimum Backup Topology Generation (S-MBT-Gen) and Minimum Backup Spanning Tree Generation (MBST-Gen) algorithms are respectively proposed to reduce the total bandwidth constraints of backup topology. In the topology mapping stage, a Reconfigurable service carrying Network Mapping algorithm with coordinated Primary and Backup Topology (RNM-PBT) is proposed to make the best of the substrate network resource. The simulation experiments show that our proposed algorithms can reduce the average resource cost and execution time cost, while improving the request accepted ratio of RSCNs.
The substrate link failures have made a great impact on the reliability of Reconfigurable Service Carrying Networks (RSCNs) over Reconfigurable Flexible Network (RFNet). In this paper, the reliability problem of delay-sensitive RSCNs is solved based on a path backup strategy, and a two-stage approach is presented to further reduce the backup resource cost. In the topology preprocessing stage, according to whether the path split is supported by RSCNs, the Splittable Minimum Backup Topology Generation (S-MBT-Gen) and Minimum Backup Spanning Tree Generation (MBST-Gen) algorithms are respectively proposed to reduce the total bandwidth constraints of backup topology. In the topology mapping stage, a Reconfigurable service carrying Network Mapping algorithm with coordinated Primary and Backup Topology (RNM-PBT) is proposed to make the best of the substrate network resource. The simulation experiments show that our proposed algorithms can reduce the average resource cost and execution time cost, while improving the request accepted ratio of RSCNs.
A Cross-layer Energy-efficient Bidirectional Gradient Routing Algorithm for Wireless Sensor Networks
2013, 35(1): 133-140.
doi: 10.3724/SP.J.1146.2012.00368
Abstract:
To reduce the redundant control overhead in the process of creating downstream routes and the mechanism of updating energy information, a Cross-layer Energy-efficient Bidirectional Routing(CEBR) algorithm is proposed. CEBR establishes downstream routes from the sink node to sensor nodes by the means of source routing and obtains the information of nodes residual energy through cross-layer information sharing. An integrated routing criterion which includes hop counts and nodes residual energy is designed to balance nodes energy consumption. In addition, a power control mechanism is presented to save nodes energy based on Received Signal Strength Indication (RSSI). Theoretical analysis verifies the effectiveness of CEBR. Also, simulation results show that CEBR reduces at least 34.5% of the normalized control overhead and 27.12% of the average energy consumption of a data packet, and extends the network lifetime by at least 18.98%, as compared to the existing classic algorithms.
To reduce the redundant control overhead in the process of creating downstream routes and the mechanism of updating energy information, a Cross-layer Energy-efficient Bidirectional Routing(CEBR) algorithm is proposed. CEBR establishes downstream routes from the sink node to sensor nodes by the means of source routing and obtains the information of nodes residual energy through cross-layer information sharing. An integrated routing criterion which includes hop counts and nodes residual energy is designed to balance nodes energy consumption. In addition, a power control mechanism is presented to save nodes energy based on Received Signal Strength Indication (RSSI). Theoretical analysis verifies the effectiveness of CEBR. Also, simulation results show that CEBR reduces at least 34.5% of the normalized control overhead and 27.12% of the average energy consumption of a data packet, and extends the network lifetime by at least 18.98%, as compared to the existing classic algorithms.
2013, 35(1): 141-146.
doi: 10.3724/SP.J.1146.2011.01178
Abstract:
With the store-carry-forward transmitting manner in social intermittently connected mobile network, the nodes always behave in community movement model. A community structure detecting method is proposed based on similarity and community label propagation. According to the statistics of roaming epochs in community movement, the centrality of nodes can be evaluated accurately; moreover, the network update correlative situation after controlling the label propagation with certain constraint condition. Finally the whole network is divided into several communities logically, and centrality nodes are also probed. Simulation results show that the method is effective.
With the store-carry-forward transmitting manner in social intermittently connected mobile network, the nodes always behave in community movement model. A community structure detecting method is proposed based on similarity and community label propagation. According to the statistics of roaming epochs in community movement, the centrality of nodes can be evaluated accurately; moreover, the network update correlative situation after controlling the label propagation with certain constraint condition. Finally the whole network is divided into several communities logically, and centrality nodes are also probed. Simulation results show that the method is effective.
2013, 35(1): 147-150.
doi: 10.3724/SP.J.1146.2012.00468
Abstract:
A cooperative handover mechanism based on a Hierarchical Network Coding (HNC) is proposed for multi-hop, multi-path handover scenario in wireless internet of things in this paper. Based on traditional practical network coding, HNC makes use of the different hop between mobile terminal and network access point, and adopts multi intermediate circle to divide levels in the network. With the cooperation of intermediate nodes in different levels, mobile terminal can establish handover connection with remote access point. HNC keeps reliable handover connections during the terminal is moving.
A cooperative handover mechanism based on a Hierarchical Network Coding (HNC) is proposed for multi-hop, multi-path handover scenario in wireless internet of things in this paper. Based on traditional practical network coding, HNC makes use of the different hop between mobile terminal and network access point, and adopts multi intermediate circle to divide levels in the network. With the cooperation of intermediate nodes in different levels, mobile terminal can establish handover connection with remote access point. HNC keeps reliable handover connections during the terminal is moving.
2013, 35(1): 151-158.
doi: 10.3724/SP.J.1146.2012.00782
Abstract:
For the mobility issue in Locator/Identifier Separation Protocol (LISP) networks, a network-based Secure Mobility Control Protocol (LISP-SMCP) is proposed. Taking access networks as different mobile domains, LISP SMCP supports mobile nodes intra-domain handoff and inter-domain handoff efficiently, and achieves local authentication and mutual authentication. The security and performance analysis results show that, LISP-SMCP can resist man-in-the-middle attacks, replay attacks and modified attacks. And it outperforms existing schemes in terms of authentication latency, handoff latency and handoff blocking probability.
For the mobility issue in Locator/Identifier Separation Protocol (LISP) networks, a network-based Secure Mobility Control Protocol (LISP-SMCP) is proposed. Taking access networks as different mobile domains, LISP SMCP supports mobile nodes intra-domain handoff and inter-domain handoff efficiently, and achieves local authentication and mutual authentication. The security and performance analysis results show that, LISP-SMCP can resist man-in-the-middle attacks, replay attacks and modified attacks. And it outperforms existing schemes in terms of authentication latency, handoff latency and handoff blocking probability.
2013, 35(1): 159-165.
doi: 10.3724/SP.J.1146.2012.00316
Abstract:
In order to plan wireless mesh network rationally and ensure that the network could work reliably in the long-term under the condition of saving wireless resource, a calculation formula is defined for normalized relative reliability constraint among different nodes. Meanwhile, the optimization model of network topology control is established and the calculating method is proposed for topology control with reliability constraint. The method integrates Prim's algorithm for minimum spanning tree into max-flow min-cut algorithm. After calculating the disjoint paths in which each-hop-link is the shortest distance, the topology optimization is obtained by considering the correlation between the number of disjoint paths and the reliability of network topology. Not only the correction is proved, but also time and space complexities of the proposed method are analyzed. By simulation and comparative analysis, the average performance of throughput and delay ascend respectively 15.3% and 20.1% under the reliability constraint in which four disjoint paths need to be met among 2 sqrt (N) pairs of nodes and two disjoint paths among other nodes. It demonstrates that the proposed method is both more reasonable and flexible. Furthermore, it meets the requirement well for the topology control of actual wireless network.
In order to plan wireless mesh network rationally and ensure that the network could work reliably in the long-term under the condition of saving wireless resource, a calculation formula is defined for normalized relative reliability constraint among different nodes. Meanwhile, the optimization model of network topology control is established and the calculating method is proposed for topology control with reliability constraint. The method integrates Prim's algorithm for minimum spanning tree into max-flow min-cut algorithm. After calculating the disjoint paths in which each-hop-link is the shortest distance, the topology optimization is obtained by considering the correlation between the number of disjoint paths and the reliability of network topology. Not only the correction is proved, but also time and space complexities of the proposed method are analyzed. By simulation and comparative analysis, the average performance of throughput and delay ascend respectively 15.3% and 20.1% under the reliability constraint in which four disjoint paths need to be met among 2 sqrt (N) pairs of nodes and two disjoint paths among other nodes. It demonstrates that the proposed method is both more reasonable and flexible. Furthermore, it meets the requirement well for the topology control of actual wireless network.
2013, 35(1): 166-171.
doi: 10.3724/SP.J.1146.2012.00716
Abstract:
A joint estimation method of Doppler frequency shift and Doppler frequency rate based on interpolation is proposed for achieving fast carrier synchronization of burst in mobile satellite communication system under the circumstance of low Signal-to-Noise Ratio (SNR). In the proposed method, a coarse estimation of Doppler frequency shift and Doppler frequency rate is achieved first by a Doppler frequency rate searching combined with a traditional low-complexity frequency-estimating algorithm. The log-likelihood function of three Doppler frequency rate testing values, with the coarse estimation result as the center, is calculated and then an interpolation is taken to decide the final estimation of Doppler frequency rate. Finally, the frequency-estimating algorithm is used again to get the final estimation of Doppler frequency shift. Simulation results show that the proposed method has a low SNR threshold and an estimation performance close to Cramer-Rao Low Bound (CRLB). And it has a complexity by far the less than the max-likelihood algorithm and so is very applicable.
A joint estimation method of Doppler frequency shift and Doppler frequency rate based on interpolation is proposed for achieving fast carrier synchronization of burst in mobile satellite communication system under the circumstance of low Signal-to-Noise Ratio (SNR). In the proposed method, a coarse estimation of Doppler frequency shift and Doppler frequency rate is achieved first by a Doppler frequency rate searching combined with a traditional low-complexity frequency-estimating algorithm. The log-likelihood function of three Doppler frequency rate testing values, with the coarse estimation result as the center, is calculated and then an interpolation is taken to decide the final estimation of Doppler frequency rate. Finally, the frequency-estimating algorithm is used again to get the final estimation of Doppler frequency shift. Simulation results show that the proposed method has a low SNR threshold and an estimation performance close to Cramer-Rao Low Bound (CRLB). And it has a complexity by far the less than the max-likelihood algorithm and so is very applicable.
2013, 35(1): 172-177.
doi: 10.3724/SP.J.1146.2012.00762
Abstract:
A Carrier Frequency Offset (CFO) estimation method is proposed based on signal detection in Superposition Coded Modulation (SCM)-OFDM systems. This method reconstructs first the received signal by decision symbols from the SCM iterative detector, and then estimates the CFO by employing the Minimum Mean Squared Error (MMSE) criterion. It is an efficient blind CFO estimation method without the aid of extra training sequences or pilot symbols. Furthermore, an improved method is proposed to estimate CFO in this paper. In the improved method, a joint CFO estimation and signal detection receiver is realized by an iterative process. Thus data detection and CFO estimation need to be implemented in each iteration process. And the receiver can compensate the CFO by the last estimated value during signal detection. Simulation results show that the proposed CFO estimation methods can significantly and accurately estimate the CFO for SCM-OFDM systems.
A Carrier Frequency Offset (CFO) estimation method is proposed based on signal detection in Superposition Coded Modulation (SCM)-OFDM systems. This method reconstructs first the received signal by decision symbols from the SCM iterative detector, and then estimates the CFO by employing the Minimum Mean Squared Error (MMSE) criterion. It is an efficient blind CFO estimation method without the aid of extra training sequences or pilot symbols. Furthermore, an improved method is proposed to estimate CFO in this paper. In the improved method, a joint CFO estimation and signal detection receiver is realized by an iterative process. Thus data detection and CFO estimation need to be implemented in each iteration process. And the receiver can compensate the CFO by the last estimated value during signal detection. Simulation results show that the proposed CFO estimation methods can significantly and accurately estimate the CFO for SCM-OFDM systems.
2013, 35(1): 178-184.
doi: 10.3724/SP.J.1146.2012.00821
Abstract:
Because of the usage of practical windowed pulse shaping filter and limitation of real field orthogonality of OFDM with Offset QAM (OFDM/OQAM) systems, the zero-forcing equalization as signal detector can not completely remove the Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) introduced by multipath fading channels. The ISI and ICI lead to severe degradation of BER performance of OFDM/OQAM system. Moreover, the imperfect channel estimation by using preamble also results in the further BER performance degradation. In this paper, one Parallel-Interference-Cancellation (PIC) signal detection method based on zero-forcing equalization for OFDM/OQAM systems is proposed by reconstruction of ISI and ICI with aid of initial data detection. And analytical results on residual interference by Zero-Forcing (ZF) and imperfect channel estimator are given. Finally, simulation results demonstrate that OFDM/OQAM system with PIC signal detector can achieve better BER performance by 1 dB to 2 dB while BER equal to 1% than conventional signal detector.
Because of the usage of practical windowed pulse shaping filter and limitation of real field orthogonality of OFDM with Offset QAM (OFDM/OQAM) systems, the zero-forcing equalization as signal detector can not completely remove the Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) introduced by multipath fading channels. The ISI and ICI lead to severe degradation of BER performance of OFDM/OQAM system. Moreover, the imperfect channel estimation by using preamble also results in the further BER performance degradation. In this paper, one Parallel-Interference-Cancellation (PIC) signal detection method based on zero-forcing equalization for OFDM/OQAM systems is proposed by reconstruction of ISI and ICI with aid of initial data detection. And analytical results on residual interference by Zero-Forcing (ZF) and imperfect channel estimator are given. Finally, simulation results demonstrate that OFDM/OQAM system with PIC signal detector can achieve better BER performance by 1 dB to 2 dB while BER equal to 1% than conventional signal detector.
2013, 35(1): 185-190.
doi: 10.3724/SP.J.1146.2012.00772
Abstract:
This paper focuses on the semi-blind equalization for Multiple-Input Multiple-Output (MIMO) systems with Quadrature Amplitude Modulation (QAM) signal. Combining the advantages of simplicity of Square Contour Algorithm (SCA) and accuracy of Soft Decision-Directed (SDD) scheme together, the SCA added SDD (SCA+ SDD) method is proposed, which has the good performances of both simplicity and accuracy. In the optimization procedure, a minimum number (equal to the number of receiving antennas) of training symbols are firstly utilized to derive the rough estimate of the spatial equalizers weight vectors, and then the conjugate gradient algorithm is proposed to optimize the cost function. The new scheme possesses the performance of approximate quadratic convergent. Compared with traditional gradient-type algorithms, conjugate gradient algorithm has a faster convergent speed and less computational quantity complexity. Finally, the methods reliability and validity are evaluated by Bite Error Rate (BER) and convergent speed respectively. Computer simulation confirms the good performances of the algorithm.
This paper focuses on the semi-blind equalization for Multiple-Input Multiple-Output (MIMO) systems with Quadrature Amplitude Modulation (QAM) signal. Combining the advantages of simplicity of Square Contour Algorithm (SCA) and accuracy of Soft Decision-Directed (SDD) scheme together, the SCA added SDD (SCA+ SDD) method is proposed, which has the good performances of both simplicity and accuracy. In the optimization procedure, a minimum number (equal to the number of receiving antennas) of training symbols are firstly utilized to derive the rough estimate of the spatial equalizers weight vectors, and then the conjugate gradient algorithm is proposed to optimize the cost function. The new scheme possesses the performance of approximate quadratic convergent. Compared with traditional gradient-type algorithms, conjugate gradient algorithm has a faster convergent speed and less computational quantity complexity. Finally, the methods reliability and validity are evaluated by Bite Error Rate (BER) and convergent speed respectively. Computer simulation confirms the good performances of the algorithm.
2013, 35(1): 191-195.
doi: 10.3724/SP.J.1146.2012.00837
Abstract:
The generalized cyclotomic sequences with length pm has high linear complexity. In this paper, a class of error generalized cyclotomic sequences is constructed by changing the characteristic sets of the above sequences. The results show that the (p1)/2-error linear complexity of generalized cyclotomic sequences do not exceed pm1, which are much less than its (zero-error) linear complexity. Thus, it is not secure enough to be used in the stream cipher system.
The generalized cyclotomic sequences with length pm has high linear complexity. In this paper, a class of error generalized cyclotomic sequences is constructed by changing the characteristic sets of the above sequences. The results show that the (p1)/2-error linear complexity of generalized cyclotomic sequences do not exceed pm1, which are much less than its (zero-error) linear complexity. Thus, it is not secure enough to be used in the stream cipher system.
2013, 35(1): 196-202.
doi: 10.3724/SP.J.1146.2012.00746
Abstract:
Considering the anisotropic characteristics of screen content, satisfactory coding efficiency cannot be achieved when screen content is coded only by traditional image/video coding tools. A new Dual-coder Mixed Chroma-sampling-rate (DMC) technique is proposed for full-chroma (YUV4:4:4) screen content coding by adding a dictionary-entropy based coder which extracted from Lempel-Ziv-Markov chain Algorithm (LZMA) to existing High Efficiency Video Coding (HEVC) SDK tools for better coding efficiency of discontinues-tone portion of screen content. Two coders are seamlessly unified and the optimal coder is selected adaptively macroblock-by-macroblock to fit the characteristics of the macroblock content. A mixed chroma-sample-rate method is also proposed for reducing distortions to convert YUV4:4:4 to YUV4:2:0. Coding experimental results show that DMC coding can achieve much higher PSNR than the current HEVC. There are also obvious improvements on the subjective visual quality differences between them.
Considering the anisotropic characteristics of screen content, satisfactory coding efficiency cannot be achieved when screen content is coded only by traditional image/video coding tools. A new Dual-coder Mixed Chroma-sampling-rate (DMC) technique is proposed for full-chroma (YUV4:4:4) screen content coding by adding a dictionary-entropy based coder which extracted from Lempel-Ziv-Markov chain Algorithm (LZMA) to existing High Efficiency Video Coding (HEVC) SDK tools for better coding efficiency of discontinues-tone portion of screen content. Two coders are seamlessly unified and the optimal coder is selected adaptively macroblock-by-macroblock to fit the characteristics of the macroblock content. A mixed chroma-sample-rate method is also proposed for reducing distortions to convert YUV4:4:4 to YUV4:2:0. Coding experimental results show that DMC coding can achieve much higher PSNR than the current HEVC. There are also obvious improvements on the subjective visual quality differences between them.
2013, 35(1): 203-208.
doi: 10.3724/SP.J.1146.2012.00590
Abstract:
For most of those existing block-based compressed sensing of video, the same measurement matrix is usually utilized for all blocks, which underestimates the fact that the structural complexity and the movement varies from different regions. To address this issue, a novel block-based adaptive compressde sensing algorithm with variable sampling rate is proposed according to the distribution characteristics of the correlations between neighboring frames. It classifies blocks into different types depending on their inter-frame correlation, and adjusts the sampling rate accordingly. Multihypothesis predicting algorithm is used to reconstruct the videos to make full use of the inter-frame correlation. The experiment showes that the proposed algorithm reduces the number of sampled measurements while still improving the quality of the reconstructed frames. Also, with the variable sampling rate method, a higher reconstruction quality can be achieved for the regions containing relatively fast movement.
For most of those existing block-based compressed sensing of video, the same measurement matrix is usually utilized for all blocks, which underestimates the fact that the structural complexity and the movement varies from different regions. To address this issue, a novel block-based adaptive compressde sensing algorithm with variable sampling rate is proposed according to the distribution characteristics of the correlations between neighboring frames. It classifies blocks into different types depending on their inter-frame correlation, and adjusts the sampling rate accordingly. Multihypothesis predicting algorithm is used to reconstruct the videos to make full use of the inter-frame correlation. The experiment showes that the proposed algorithm reduces the number of sampled measurements while still improving the quality of the reconstructed frames. Also, with the variable sampling rate method, a higher reconstruction quality can be achieved for the regions containing relatively fast movement.
2013, 35(1): 209-214.
doi: 10.3724/SP.J.1146.2012.00658
Abstract:
A novel Crank-Nicolson (CN)-FDTD method based on the split-step scheme is proposed in this paper, so as to calculate the electromagnetic transients in transmission line with complex circuit terminals accurately and efficiently. An analytical proof of unconditional stability of the method is provided. Combined with the hybrid one-port equivalent model, the transmission system is decomposed into lumped and distributed portions independently. It can solve the time response of the complex circuit networks by utilizing the Modified Nodal Analysis (MNA) method. Unlike the former methods, the maximum time step size is not limited by the restriction of Courant-Friedrichs-Lewy (CFL) stability constraint. In addition, the dispersion errors can be reduced by the precision sub-time-step scheme. The method is utilized to the transient analysis of the single transmission line. The results show that the proposed method provides higher efficiency and good stability under the same precision level.
A novel Crank-Nicolson (CN)-FDTD method based on the split-step scheme is proposed in this paper, so as to calculate the electromagnetic transients in transmission line with complex circuit terminals accurately and efficiently. An analytical proof of unconditional stability of the method is provided. Combined with the hybrid one-port equivalent model, the transmission system is decomposed into lumped and distributed portions independently. It can solve the time response of the complex circuit networks by utilizing the Modified Nodal Analysis (MNA) method. Unlike the former methods, the maximum time step size is not limited by the restriction of Courant-Friedrichs-Lewy (CFL) stability constraint. In addition, the dispersion errors can be reduced by the precision sub-time-step scheme. The method is utilized to the transient analysis of the single transmission line. The results show that the proposed method provides higher efficiency and good stability under the same precision level.
2013, 35(1): 215-227.
doi: 10.3724/SP.J.1146.2012.00876
Abstract:
Based on analyzing overseas and domestic research status and technology readiness levels of wireless sensor networks (WSNs), the correlation between WSNs and Internet of Things (IoT) is described from a technical point. Key technologies required for WSNs implement, which include information acquisition system design, network services support and network communication protocol, are discussed in this paper. Development conceptions of future WSNs are presented based on summarizing challenges that WSNs must be solved.
Based on analyzing overseas and domestic research status and technology readiness levels of wireless sensor networks (WSNs), the correlation between WSNs and Internet of Things (IoT) is described from a technical point. Key technologies required for WSNs implement, which include information acquisition system design, network services support and network communication protocol, are discussed in this paper. Development conceptions of future WSNs are presented based on summarizing challenges that WSNs must be solved.
