Email alert
2007 Vol. 29, No. 4
Display Method:
Study of Mobile-Agent-Based Information-Driven Multiresolution Algorithm in Wireless Sensor Networks
2007, 29(4): 763-766.
doi: 10.3724/SP.J.1146.2006.00110
Abstract:
in this paper, Mobile-Agent-based Information-Driven Multiresolution Algorithm (MAIDM) is presented for Target Tracking in Wireless Sensor Networks(WSN), in order to provide better accuracy and degree of fault tolerance while meeting the energy requirement. In a clustered-based wireless sensor networks，mobile agent is used to process data of nodes with multiresolution algorithm according to information contribution of different nodes，and the size of mobile agent is determined by the maximum value of the information contribution along the path of mobile agent. A balance has to be struck between the energy efficiency object and fault tolerance/accuracy object. Simulation results show that MAIDM performs better than IDSQ from perspectives of fault tolerance and accuracy, MAIDM s energy-efficient performance is better than MA-CSIP.
in this paper, Mobile-Agent-based Information-Driven Multiresolution Algorithm (MAIDM) is presented for Target Tracking in Wireless Sensor Networks(WSN), in order to provide better accuracy and degree of fault tolerance while meeting the energy requirement. In a clustered-based wireless sensor networks，mobile agent is used to process data of nodes with multiresolution algorithm according to information contribution of different nodes，and the size of mobile agent is determined by the maximum value of the information contribution along the path of mobile agent. A balance has to be struck between the energy efficiency object and fault tolerance/accuracy object. Simulation results show that MAIDM performs better than IDSQ from perspectives of fault tolerance and accuracy, MAIDM s energy-efficient performance is better than MA-CSIP.
2007, 29(4): 767-770.
doi: 10.3724/SP.J.1146.2005.01106
Abstract:
An effective approach for extending wireless sensor network lifetime is scheduling sleep intervals for extraneous nodes. But most of the existing coverage protocols are based on the circular sensing module. So, how to combine consideration of coverage and connectivity maintenance in a single activity scheduling is discussed in this paper, when the sensing module is not circular. The Well-Proportioned Coverage Strategy (WPCS) is presented which extends the lifetime of sensor network by minimizing the overlap area. Simulations show that WPCS outperforms Coverage Configuration Protocol (CCP) and is suitable for various situations. It effectively reduces the number of activity nodes and extends the lifetime of sensor network.
An effective approach for extending wireless sensor network lifetime is scheduling sleep intervals for extraneous nodes. But most of the existing coverage protocols are based on the circular sensing module. So, how to combine consideration of coverage and connectivity maintenance in a single activity scheduling is discussed in this paper, when the sensing module is not circular. The Well-Proportioned Coverage Strategy (WPCS) is presented which extends the lifetime of sensor network by minimizing the overlap area. Simulations show that WPCS outperforms Coverage Configuration Protocol (CCP) and is suitable for various situations. It effectively reduces the number of activity nodes and extends the lifetime of sensor network.
2007, 29(4): 771-775.
doi: 10.3724/SP.J.1146.2005.01091
Abstract:
One mission of network management is to monitor the network effectively. The monitoring methods in Simple Networks Management Protocol (SNMP) are polling and trap. Both of them consume the system resources and network bandwidth. Based on the hierarchical network architecture, a dynamic monitoring algorithm is proposed so as to minimize the management overhead. By analyzing the probability of the alarm occurrence with the sampled network information, the proposed algorithm prolongs the interval between two consecutive polling when no alarm could occur. It also reduces the redundant alarm information resulted from the signal fluctuation. This method significantly reduces the amount of monitoring traffic and guarantees to detect the abnormal event. The simulation results show that the proposed monitoring scheme reduces both the number of polling and the cost of the network management, consequently improves the network performance.
One mission of network management is to monitor the network effectively. The monitoring methods in Simple Networks Management Protocol (SNMP) are polling and trap. Both of them consume the system resources and network bandwidth. Based on the hierarchical network architecture, a dynamic monitoring algorithm is proposed so as to minimize the management overhead. By analyzing the probability of the alarm occurrence with the sampled network information, the proposed algorithm prolongs the interval between two consecutive polling when no alarm could occur. It also reduces the redundant alarm information resulted from the signal fluctuation. This method significantly reduces the amount of monitoring traffic and guarantees to detect the abnormal event. The simulation results show that the proposed monitoring scheme reduces both the number of polling and the cost of the network management, consequently improves the network performance.
2007, 29(4): 776-780.
doi: 10.3724/SP.J.1146.2005.01684
Abstract:
When disaster happens, it is necessary use quantitive and accurate method to select the best set from many sub disaster recovery plans to control the disaster recovery activities. This paper presents a practicable mathematical model using optimization theory. The model contains some parameters that stand for different applications, facilities, resources, sub plans, budget, etc. The model classifies resources and solves the conflicts among various sub disaster recovery plans. With less subjective parameter, the model can evaluate DRP more impersonally. The model possesses less parameter and can be easily implemented to analyze DRP accurately and quantitatively. The implementation and the analysis of the model are presented. Test also verifies the correctness of this model.
When disaster happens, it is necessary use quantitive and accurate method to select the best set from many sub disaster recovery plans to control the disaster recovery activities. This paper presents a practicable mathematical model using optimization theory. The model contains some parameters that stand for different applications, facilities, resources, sub plans, budget, etc. The model classifies resources and solves the conflicts among various sub disaster recovery plans. With less subjective parameter, the model can evaluate DRP more impersonally. The model possesses less parameter and can be easily implemented to analyze DRP accurately and quantitatively. The implementation and the analysis of the model are presented. Test also verifies the correctness of this model.
2007, 29(4): 781-784.
doi: 10.3724/SP.J.1146.2005.01105
Abstract:
Many description languages can be used by the formal specification, but there is a uniform method which can perform the conformance test under the formal specification. Adopting a statistical method, this paper analyses the conformance test reliability based on the formal specification, then it will give the confidence interval for the reliability and especially point out the conditions which can affect the reliability under zero-error.
Many description languages can be used by the formal specification, but there is a uniform method which can perform the conformance test under the formal specification. Adopting a statistical method, this paper analyses the conformance test reliability based on the formal specification, then it will give the confidence interval for the reliability and especially point out the conditions which can affect the reliability under zero-error.
2007, 29(4): 785-788.
doi: 10.3724/SP.J.1146.2006.00152
Abstract:
A new round robin scheduling algorithm named LFRR(Large weight First Round Robin) is proposed in this paper. In order to achieve good delay property and low implementation complexity, several methods are taken in LFRR. Firstly, when slots are allocated for flows in the schedule table, LFRR refers to the ideal situation where the slots of each flow are uniformly distributed in the schedule table to prevent flows slots from appearing too early or too late. Secondly, in LFRR system flows which weights are the same and larger than 1 are aggregated into a virtual flow. LFRR deals with virtual flows instead of actual flows. This deceases the flow number that scheduling algorithm deals with. Thirdly, when a slot can be allocated to several virtual flows, flows with larger weight have high priority to posses this slot. Theoretical and simulation results show the delay property of LFRR is much better than that of WRR(Weighted Round Robin) and the fairness of LFRR can be guaranteed.
A new round robin scheduling algorithm named LFRR(Large weight First Round Robin) is proposed in this paper. In order to achieve good delay property and low implementation complexity, several methods are taken in LFRR. Firstly, when slots are allocated for flows in the schedule table, LFRR refers to the ideal situation where the slots of each flow are uniformly distributed in the schedule table to prevent flows slots from appearing too early or too late. Secondly, in LFRR system flows which weights are the same and larger than 1 are aggregated into a virtual flow. LFRR deals with virtual flows instead of actual flows. This deceases the flow number that scheduling algorithm deals with. Thirdly, when a slot can be allocated to several virtual flows, flows with larger weight have high priority to posses this slot. Theoretical and simulation results show the delay property of LFRR is much better than that of WRR(Weighted Round Robin) and the fairness of LFRR can be guaranteed.
2007, 29(4): 789-794.
doi: 10.3724/SP.J.1146.2005.01127
Abstract:
In the real domain, the finitely supported, orthogonal, symmetric nontrivial scalar wavelet bases do not exist, while the multiwavelet offers the finite support, symmetry, orthogonality simultaneously. As a result, the wavelet theory is extended to vector field. Considering vector characteristics provided by the coefficients of the multiwavelet transformed image, pixel-based and region-based scalar fusion schemes are extended to vector case and a novel fusion algorithm is also proposed in this paper. The new algorithm is based on vector fusion scheme in multiwavelet domain, which makes sufficient use of the correlation among the components of multiwavelet transform coefficient vectors to improve fusion quality. The original algorithm is carried out with emphases on the novelty of the fusion algorithm and the demonstration by using real multispectral image compared with algorithms employing wavelet scalar fusion scheme. The experimental results demonstrate that the proposed multiwavelet vector fusion algorithm can obtain both better subjective vision characteristics and better objective evaluation indices and outperform the wavelet scalar fusion scheme. Accordingly it is testified that when applied in image fusion, multiwavelet is more suitable than wavelet to human vision system and it is of great potential to wide applications.
In the real domain, the finitely supported, orthogonal, symmetric nontrivial scalar wavelet bases do not exist, while the multiwavelet offers the finite support, symmetry, orthogonality simultaneously. As a result, the wavelet theory is extended to vector field. Considering vector characteristics provided by the coefficients of the multiwavelet transformed image, pixel-based and region-based scalar fusion schemes are extended to vector case and a novel fusion algorithm is also proposed in this paper. The new algorithm is based on vector fusion scheme in multiwavelet domain, which makes sufficient use of the correlation among the components of multiwavelet transform coefficient vectors to improve fusion quality. The original algorithm is carried out with emphases on the novelty of the fusion algorithm and the demonstration by using real multispectral image compared with algorithms employing wavelet scalar fusion scheme. The experimental results demonstrate that the proposed multiwavelet vector fusion algorithm can obtain both better subjective vision characteristics and better objective evaluation indices and outperform the wavelet scalar fusion scheme. Accordingly it is testified that when applied in image fusion, multiwavelet is more suitable than wavelet to human vision system and it is of great potential to wide applications.
2007, 29(4): 795-799.
doi: 10.3724/SP.J.1146.2006.00009
Abstract:
The content-based image retrieval on histogram is analyzed and a novel image retrieval algorithm is proposed based on bit-plane distribution entropy. Firstly, the image is divided into eight bit-planes by the image bit-plane-code. Then, an entropy vector is constructed by computing the entropy of the four significant planes which contain most of the structural information of the image. Meantime, the gray-code of bit-planes is used to avoid the effect of changes in the image intensity values on bit-planes. Finally the Mahalanobis distance is adopted to measure the similarity because of the correlation between the concerned vectors after designing the correlation-weighted matrix. Experimental results show that the proposed method has sound retrieval performance.
The content-based image retrieval on histogram is analyzed and a novel image retrieval algorithm is proposed based on bit-plane distribution entropy. Firstly, the image is divided into eight bit-planes by the image bit-plane-code. Then, an entropy vector is constructed by computing the entropy of the four significant planes which contain most of the structural information of the image. Meantime, the gray-code of bit-planes is used to avoid the effect of changes in the image intensity values on bit-planes. Finally the Mahalanobis distance is adopted to measure the similarity because of the correlation between the concerned vectors after designing the correlation-weighted matrix. Experimental results show that the proposed method has sound retrieval performance.
2007, 29(4): 800-803.
doi: 10.3724/SP.J.1146.2005.01674
Abstract:
Active Shape Models (ASM) is one of powerful tools for face alignment and face recognition. However, the performance of ASM is often influenced by some factors such as the initial location, illumination and so on, which will frequently lead to the local minima in optimization. This paper proposes a weighted Active Shape Models, in which the more robust local appearance model is constructed with the local information of each landmark fully. Through the improved method the local minima problem can be solved efficiently, extracted the detailed local information of face feature points and localized the points accurately. Experiments verify the above conclusions.
Active Shape Models (ASM) is one of powerful tools for face alignment and face recognition. However, the performance of ASM is often influenced by some factors such as the initial location, illumination and so on, which will frequently lead to the local minima in optimization. This paper proposes a weighted Active Shape Models, in which the more robust local appearance model is constructed with the local information of each landmark fully. Through the improved method the local minima problem can be solved efficiently, extracted the detailed local information of face feature points and localized the points accurately. Experiments verify the above conclusions.
2007, 29(4): 804-807.
doi: 10.3724/SP.J.1146.2006.00477
Abstract:
Wavelet transform is widely used in data compression. How to choice the best wavelet base is a key point for improving the compression ratio. In ths paper, a idea of using wavelet base functions matching to signal which need to be compressed is put forward. A waveform matching criteria for contructing matche wavelets, which it used to compress the one-dimension signal, is given. The wavelet filter is constructed with an structuring filter banks and the criteria,and an example of compressing a one-dimension signal is presented. Compared with other wavelet filters, the matched wavelet filter is able to improve the performance of signal compression.
Wavelet transform is widely used in data compression. How to choice the best wavelet base is a key point for improving the compression ratio. In ths paper, a idea of using wavelet base functions matching to signal which need to be compressed is put forward. A waveform matching criteria for contructing matche wavelets, which it used to compress the one-dimension signal, is given. The wavelet filter is constructed with an structuring filter banks and the criteria,and an example of compressing a one-dimension signal is presented. Compared with other wavelet filters, the matched wavelet filter is able to improve the performance of signal compression.
2007, 29(4): 808-810.
doi: 10.3724/SP.J.1146.2005.00998
Abstract:
The choice of test statistics can bring important influence to nonlinear of time series. This paper introduces a Non-parameter testKolmogorov-Smirnov (KS) test into nonlinearity test. After applying the Phase-randomized surrogate algorithm to create surrogate data, three test statistics methods, which include KS test, the third-order autocovariance and the asymmetry due to time reversal, are employed to determine nonlinear of five kinds signals. By comparing the test results, it indicates that KS test is an effective and stable nonlinear test statistics. The proposed method has high noise immunity and more sensitive to nonlinear signal.
The choice of test statistics can bring important influence to nonlinear of time series. This paper introduces a Non-parameter testKolmogorov-Smirnov (KS) test into nonlinearity test. After applying the Phase-randomized surrogate algorithm to create surrogate data, three test statistics methods, which include KS test, the third-order autocovariance and the asymmetry due to time reversal, are employed to determine nonlinear of five kinds signals. By comparing the test results, it indicates that KS test is an effective and stable nonlinear test statistics. The proposed method has high noise immunity and more sensitive to nonlinear signal.
2007, 29(4): 811-814.
doi: 10.3724/SP.J.1146.2005.00706
Abstract:
According to one-to-one relationship of the Binary-Phase-Shift-Keying (BPSK) fuse signals pulse-phase difference and the m-sequence, the m-sequence can be obtained by solving the phase-difference equations. First, the pulse phase is measured by FFT. Then, first-order phase difference method and second-order phase difference method separately are applied to identify the m-sequence. The computer simulation proves the method to be completely correct. Finally, the reliability of the method is analyzed to find that, even if any Pseudo Noise (PN) code is mistakenly identified because of large measuring error of the corresponding pulse phase, it has no influence on identification of the later codes. This indicates that the method has high reliability.
According to one-to-one relationship of the Binary-Phase-Shift-Keying (BPSK) fuse signals pulse-phase difference and the m-sequence, the m-sequence can be obtained by solving the phase-difference equations. First, the pulse phase is measured by FFT. Then, first-order phase difference method and second-order phase difference method separately are applied to identify the m-sequence. The computer simulation proves the method to be completely correct. Finally, the reliability of the method is analyzed to find that, even if any Pseudo Noise (PN) code is mistakenly identified because of large measuring error of the corresponding pulse phase, it has no influence on identification of the later codes. This indicates that the method has high reliability.
2007, 29(4): 815-818.
doi: 10.3724/SP.J.1146.2005.01139
Abstract:
In this paper, a new method is explored for synthesizing range profile of a moving target via stepped frequency signal. The principle of synthesizing range profile of an extended target is investigated for stepped frequency signal. The distortion of synthetic range profiles is discussed with the theory of Discrete Fourier Transform (DFT). Based on phase cancellation, a new technology is proposed to achieve range profile with out distortion for a moving target. The new technology does not need the estimation of the velocity. The result of emulation proves the effect of the method.
In this paper, a new method is explored for synthesizing range profile of a moving target via stepped frequency signal. The principle of synthesizing range profile of an extended target is investigated for stepped frequency signal. The distortion of synthetic range profiles is discussed with the theory of Discrete Fourier Transform (DFT). Based on phase cancellation, a new technology is proposed to achieve range profile with out distortion for a moving target. The new technology does not need the estimation of the velocity. The result of emulation proves the effect of the method.
2007, 29(4): 819-821.
doi: 10.3724/SP.J.1146.2005.00716
Abstract:
In this paper, a novel method of sparse coding shrinkage based on independent component analysis is proposed to reduce speckle in polarimetric SAR Images. With soft-thresholding operator on polarimetric SAR image, this method reduces speckle effectively and preserves polarimetric properties. The experiment shows that the image edges are retained with the method and the speckle is removed effectively.
In this paper, a novel method of sparse coding shrinkage based on independent component analysis is proposed to reduce speckle in polarimetric SAR Images. With soft-thresholding operator on polarimetric SAR image, this method reduces speckle effectively and preserves polarimetric properties. The experiment shows that the image edges are retained with the method and the speckle is removed effectively.
2007, 29(4): 822-826.
doi: 10.3724/SP.J.1146.2006.00416
Abstract:
Scatter targets of complex terrain surfaces with random orientation product random fluctuating echoes. This leads to a confused classification by directly using target decomposition on full polarimetric SAR (PolSAR) image. To solve this problem, a new unsupervised classification method is proposed in this paper. Firstly, the target vector is transformed to the state with minimization of cross-polarization (min-x-pol); then the parameters u/v/H are used to characterized scattering mechanism, and the fuzzy membership is adopted instead of hard division of parameter plan; finally, characterizing the coherency matrix as multivariable complex Wishart distribution, the polarimetric SAR image is classified based on Bayes maximum likelihood criteria. Experiment is performed on a L-band NASA/JPL SIR-C polarimetric SAR image over Danshui town, Guangdong, P.R. China. Furthermore, the movements of the clustering centers are discussed. Compared with the k-mean like method based on H/, the results show that the proposed method provides a significant performance improvement in classification result and the associated scattering mechanism of class is more accurate. The classification result is beneficial for automatic recognition of terrain type.
Scatter targets of complex terrain surfaces with random orientation product random fluctuating echoes. This leads to a confused classification by directly using target decomposition on full polarimetric SAR (PolSAR) image. To solve this problem, a new unsupervised classification method is proposed in this paper. Firstly, the target vector is transformed to the state with minimization of cross-polarization (min-x-pol); then the parameters u/v/H are used to characterized scattering mechanism, and the fuzzy membership is adopted instead of hard division of parameter plan; finally, characterizing the coherency matrix as multivariable complex Wishart distribution, the polarimetric SAR image is classified based on Bayes maximum likelihood criteria. Experiment is performed on a L-band NASA/JPL SIR-C polarimetric SAR image over Danshui town, Guangdong, P.R. China. Furthermore, the movements of the clustering centers are discussed. Compared with the k-mean like method based on H/, the results show that the proposed method provides a significant performance improvement in classification result and the associated scattering mechanism of class is more accurate. The classification result is beneficial for automatic recognition of terrain type.
2007, 29(4): 827-830.
doi: 10.3724/SP.J.1146.2005.01200
Abstract:
Estimation of position and shape of the object subsurface is one of the main problems in Ground Penetrating Radar(GPR) application. Migration method in domain of seismic techniques is effective to locate and reshape the object. The electromagnetic wave velocity parameter is the main factor influencing the precision of location. In this paper, the GPR images are handled with frequency-wavenumber migration on the base of applying minimum entropy method to estimate velocity parameter. Experimental results of simulation and GPR data prove its feasibility and validity.
Estimation of position and shape of the object subsurface is one of the main problems in Ground Penetrating Radar(GPR) application. Migration method in domain of seismic techniques is effective to locate and reshape the object. The electromagnetic wave velocity parameter is the main factor influencing the precision of location. In this paper, the GPR images are handled with frequency-wavenumber migration on the base of applying minimum entropy method to estimate velocity parameter. Experimental results of simulation and GPR data prove its feasibility and validity.
2007, 29(4): 831-835.
doi: 10.3724/SP.J.1146.2005.01197
Abstract:
Distributed SAR system adopts the flight model which receivers and transmitter are in different platform, that has many prominent merits, but the receiver and transmitters PRF can have error. The paper bases on the principle of bistatic SAR, establishes the influence model of the PRF error to imaging and interferometry, analyzes the influence of the PRF error to interferometric phase, and proposes the PRF precision request in this foundation. The simulation enunciates the validity of the model and the reasonableness of the PRF precision requirement.
Distributed SAR system adopts the flight model which receivers and transmitter are in different platform, that has many prominent merits, but the receiver and transmitters PRF can have error. The paper bases on the principle of bistatic SAR, establishes the influence model of the PRF error to imaging and interferometry, analyzes the influence of the PRF error to interferometric phase, and proposes the PRF precision request in this foundation. The simulation enunciates the validity of the model and the reasonableness of the PRF precision requirement.
2007, 29(4): 836-840.
doi: 10.3724/SP.J.1146.2005.01171
Abstract:
Based on the special geometrical configuration of bistatic radar and linear Frequency Modulation Continuous Ware (FMCW)principle, the ambiguity function of bistatic linear FMCW radar is derived in detail in this paper, and it is showed that the shape of ambiguity function is affected by the position of target. Furthermore, the expression of range resolution, velocity resolution and range-velocity coupling slope derived from the bistatic linear FMCW ambiguity function are the function with respect to the bistatic angle, so, the resolution characteristic has the relationship with the position of target. The conclusion of this paper can be used in the signal processing and waveform design of bistatic linear FMCW radar system.
Based on the special geometrical configuration of bistatic radar and linear Frequency Modulation Continuous Ware (FMCW)principle, the ambiguity function of bistatic linear FMCW radar is derived in detail in this paper, and it is showed that the shape of ambiguity function is affected by the position of target. Furthermore, the expression of range resolution, velocity resolution and range-velocity coupling slope derived from the bistatic linear FMCW ambiguity function are the function with respect to the bistatic angle, so, the resolution characteristic has the relationship with the position of target. The conclusion of this paper can be used in the signal processing and waveform design of bistatic linear FMCW radar system.
2007, 29(4): 841-845.
doi: 10.3724/SP.J.1146.2005.01141
Abstract:
Micromation，modularization and digitization are the trends of modern radar receivers. This paper presents a novel wideband low-IF receiver topologies suitable for fully integration. Its architecture is very simple, and can attain very good performance. Also a design example of wideband low-IF radar receiver application in L-band radar is put forth.
Micromation，modularization and digitization are the trends of modern radar receivers. This paper presents a novel wideband low-IF receiver topologies suitable for fully integration. Its architecture is very simple, and can attain very good performance. Also a design example of wideband low-IF radar receiver application in L-band radar is put forth.
2007, 29(4): 846-850.
doi: 10.3724/SP.J.1146.2005.01119
Abstract:
A two-dimensional phase unwrapping approach is proposed using the branch-cut method and finite element method. Different strategies are taken for different quality data regions: first, using the congruence characteristic of the branch-cut method, the unwrapped phases can be retrieved in the reliable region with the largest area; then with good boundary values provided, the remaining regions are unwrapped with the finite element method (FEM) in a least square sense. Experimental results, carried out on simulated and real data, show that the proposed approach overcomes the drawbacks of the branch-cut method and FEM, i.e., the half-baked solution and phase slope underestimation, respectively, and has an advantage over other approaches in accuracy.
A two-dimensional phase unwrapping approach is proposed using the branch-cut method and finite element method. Different strategies are taken for different quality data regions: first, using the congruence characteristic of the branch-cut method, the unwrapped phases can be retrieved in the reliable region with the largest area; then with good boundary values provided, the remaining regions are unwrapped with the finite element method (FEM) in a least square sense. Experimental results, carried out on simulated and real data, show that the proposed approach overcomes the drawbacks of the branch-cut method and FEM, i.e., the half-baked solution and phase slope underestimation, respectively, and has an advantage over other approaches in accuracy.
2007, 29(4): 851-854.
doi: 10.3724/SP.J.1146.2005.01158
Abstract:
sing on satellite trajectories, the formula of formation flying orbit elements is derived. The imaging geometric model of distributed satellites SAR is presented and the ambiguity function of distributed satellites SAR is analyzed. Moreover, a design example of the space circular formation flying is given. According to the design result, the ambiguity function simulations of distributed satellites SAR with different formation configurations and different satellites are developed. The relation between satellites formation configurations, number and ambiguity function is studied, and it is theory basis of following imaging algorithm research.
sing on satellite trajectories, the formula of formation flying orbit elements is derived. The imaging geometric model of distributed satellites SAR is presented and the ambiguity function of distributed satellites SAR is analyzed. Moreover, a design example of the space circular formation flying is given. According to the design result, the ambiguity function simulations of distributed satellites SAR with different formation configurations and different satellites are developed. The relation between satellites formation configurations, number and ambiguity function is studied, and it is theory basis of following imaging algorithm research.
2007, 29(4): 855-858.
doi: 10.3724/SP.J.1146.2005.01089
Abstract:
Using the local nature of wavelet transform and Teager energy operator (TEO), a novel scheme is proposed to detect ship targets in SAR images based on TEO wavelet enhancement. The algorithm applies wavelet transform to SAR image and computes the Teager energy of every wavelet coefficient of the high frequency components. According to the property of the Teager energy which enhances the ship signals of SAR image, two-parameter Constant False Alarm Rate(CFAR) detection algorithm is applied to the enhanced SAR image to detect ship targets. The simulating results show that the new detector improves detection performance comparing with the two-parameter CFAR detector and the cell average detection based on K-distribution.
Using the local nature of wavelet transform and Teager energy operator (TEO), a novel scheme is proposed to detect ship targets in SAR images based on TEO wavelet enhancement. The algorithm applies wavelet transform to SAR image and computes the Teager energy of every wavelet coefficient of the high frequency components. According to the property of the Teager energy which enhances the ship signals of SAR image, two-parameter Constant False Alarm Rate(CFAR) detection algorithm is applied to the enhanced SAR image to detect ship targets. The simulating results show that the new detector improves detection performance comparing with the two-parameter CFAR detector and the cell average detection based on K-distribution.
2007, 29(4): 859-862.
doi: 10.3724/SP.J.1146.2005.01008
Abstract:
A new class-Weighted Dual v-SVM, termed as WD v-SVM, is proposed and Karush-Kuhn Tucker condition (KKT) is derived for it. The dual parameters v+ and v- are analyzed theoretically, and it is deduced that they represent the upper and the lower bound for the percentage of bounded support vectors and the support vectors in the weighted positive or negative class respectively, which is similar to their counterparts in v-SVM. Therefore, the classification performance of small sample class is improved through adjusting its class weight. Experimental results show that the WD v-SVM not only keeps the advantages of v-SVM, but also solves the problem of larger classification error rate of small sample class.
A new class-Weighted Dual v-SVM, termed as WD v-SVM, is proposed and Karush-Kuhn Tucker condition (KKT) is derived for it. The dual parameters v+ and v- are analyzed theoretically, and it is deduced that they represent the upper and the lower bound for the percentage of bounded support vectors and the support vectors in the weighted positive or negative class respectively, which is similar to their counterparts in v-SVM. Therefore, the classification performance of small sample class is improved through adjusting its class weight. Experimental results show that the WD v-SVM not only keeps the advantages of v-SVM, but also solves the problem of larger classification error rate of small sample class.
2007, 29(4): 863-866.
doi: 10.3724/SP.J.1146.2005.01338
Abstract:
In this paper a single channel speech enhancement method for noisy speech signals is proposed, which is based on masking properties of the human auditory system and power spectral density estimation. During the estimation of power spectrum of the speech, the estimator can be modified by the MMSE method and the estimator of short -time spectral amplitude filter is determined by masking properties. In this way, the best trade off among the reduction of noise, the speech distortion and the level of musical residual noise can be found. Experimental results demonstrate the improved performance of the proposed algorithms.
In this paper a single channel speech enhancement method for noisy speech signals is proposed, which is based on masking properties of the human auditory system and power spectral density estimation. During the estimation of power spectrum of the speech, the estimator can be modified by the MMSE method and the estimator of short -time spectral amplitude filter is determined by masking properties. In this way, the best trade off among the reduction of noise, the speech distortion and the level of musical residual noise can be found. Experimental results demonstrate the improved performance of the proposed algorithms.
2007, 29(4): 867-869.
doi: 10.3724/SP.J.1146.2005.01128
Abstract:
In order to use duration information in Language IDentification (LID) efficiently, the inhomogeneous Hidden Markov Model (HMM) with general topological structure is proposed, and is used to identify the language between Mandarin and English also. Because the inhomogeneous HMM with general topologic structure not only describes the duration of state more accurately than HMM, but also uses the structure information of specific language phonetics more effectively, the LID system based on the inhomogeneous HMM with general topological structure has better performance than the homogeneous HMM. For the LID system based on inhomogeneous HMM with different duration distribution, the norm distribution has better performance than the uniform distribution, it shows that the state duration is an important cue for language identification and the norm distribution can model the duration more accurately than the uniform distribution.
In order to use duration information in Language IDentification (LID) efficiently, the inhomogeneous Hidden Markov Model (HMM) with general topological structure is proposed, and is used to identify the language between Mandarin and English also. Because the inhomogeneous HMM with general topologic structure not only describes the duration of state more accurately than HMM, but also uses the structure information of specific language phonetics more effectively, the LID system based on the inhomogeneous HMM with general topological structure has better performance than the homogeneous HMM. For the LID system based on inhomogeneous HMM with different duration distribution, the norm distribution has better performance than the uniform distribution, it shows that the state duration is an important cue for language identification and the norm distribution can model the duration more accurately than the uniform distribution.
2007, 29(4): 870-874.
doi: 10.3724/SP.J.1146.2005.00858
Abstract:
A novel grouping method is proposed for LDSTBC(Layered Differential Space-Time Block Code) over frequency selective channels, relying on mutual orthogonality between subcarriers of different users in OFDMA(Orthogonal Frequency-Division Multiple Access) systems. At the transmitter, LDSTBC combined with OFDM is applied . At the receiver, the group suppression based on subcarrier selection matrices is used, then the traditional decoding method for DSTBC is used for each layer. Compared with SVD the improved approach only needs one receive antenna so the complexity of the receiver decreases remarkably. Simulation results show that the performance of the improved method is better than the one based on SVD.
A novel grouping method is proposed for LDSTBC(Layered Differential Space-Time Block Code) over frequency selective channels, relying on mutual orthogonality between subcarriers of different users in OFDMA(Orthogonal Frequency-Division Multiple Access) systems. At the transmitter, LDSTBC combined with OFDM is applied . At the receiver, the group suppression based on subcarrier selection matrices is used, then the traditional decoding method for DSTBC is used for each layer. Compared with SVD the improved approach only needs one receive antenna so the complexity of the receiver decreases remarkably. Simulation results show that the performance of the improved method is better than the one based on SVD.
2007, 29(4): 875-879.
doi: 10.3724/SP.J.1146.2005.01194
Abstract:
A Distributed Turbo Coding (DTC) structure based on Base Station (BS) cooperation is proposed in this paper. By transmitting the data after coding through several different BS, The spatial diversity gain can be obtained at the same bandwidth efficiency, thus the communication quality of the user can be enhanced in cell boundary. Because the resources are allocated among several cell range, distributed coding structure also can improve the resource alloc success probability of the users in heavy cell. Based on the DTC structure proposed in this paper, five different realizable schemes are given, and their BER performance and resource alloc success probability are analyzed in asymmetric AWGN channel. The coding structure and realizable schemes given in this paper can also be applied to multiple BS system and distributed BS system.
A Distributed Turbo Coding (DTC) structure based on Base Station (BS) cooperation is proposed in this paper. By transmitting the data after coding through several different BS, The spatial diversity gain can be obtained at the same bandwidth efficiency, thus the communication quality of the user can be enhanced in cell boundary. Because the resources are allocated among several cell range, distributed coding structure also can improve the resource alloc success probability of the users in heavy cell. Based on the DTC structure proposed in this paper, five different realizable schemes are given, and their BER performance and resource alloc success probability are analyzed in asymmetric AWGN channel. The coding structure and realizable schemes given in this paper can also be applied to multiple BS system and distributed BS system.
2007, 29(4): 880-883.
doi: 10.3724/SP.J.1146.2005.01190
Abstract:
Orthogonal Frequency Division Multiplexing (OFDM) systems is very sensitive to frequency errors. An easy pre-coding scheme with rate 1/2 can reduce this sensitivity to frequency offset and compress the inter-carrier interference. A new pre-coding scheme based on the maximum of carrier-to-interference is proposed in this article. It can efficiently find the pre-coding parameter with known frequency offset. The simulation results shown that the new pre-coding scheme can outperform the traditional one.
Orthogonal Frequency Division Multiplexing (OFDM) systems is very sensitive to frequency errors. An easy pre-coding scheme with rate 1/2 can reduce this sensitivity to frequency offset and compress the inter-carrier interference. A new pre-coding scheme based on the maximum of carrier-to-interference is proposed in this article. It can efficiently find the pre-coding parameter with known frequency offset. The simulation results shown that the new pre-coding scheme can outperform the traditional one.
2007, 29(4): 884-887.
doi: 10.3724/SP.J.1146.2005.01121
Abstract:
Optimization of binary LDPC (Low-Density Parity-Check) codes for application to binary PSK modulation has been demonstrated in the literature, on the basis of Monte-Carlo method proposed by Davey(1998). The lack of rotational symmetry in a generic q-ary signal constellation, however, limits the application of Daveys method. This paper proposes an efficient Davey-type Monte Carlo technique for code optimization within the category of quasi-regular codes, so that one can directly combine the optimized LDPC code over GF(q) with arbitrary q-ary modulation to achieve bandwidth efficiency in transmission. The validity of the proposed design procedure is illustrated through examples combining quasi-regular LDPC codes with MQAM and MPSK signaling schemes.
Optimization of binary LDPC (Low-Density Parity-Check) codes for application to binary PSK modulation has been demonstrated in the literature, on the basis of Monte-Carlo method proposed by Davey(1998). The lack of rotational symmetry in a generic q-ary signal constellation, however, limits the application of Daveys method. This paper proposes an efficient Davey-type Monte Carlo technique for code optimization within the category of quasi-regular codes, so that one can directly combine the optimized LDPC code over GF(q) with arbitrary q-ary modulation to achieve bandwidth efficiency in transmission. The validity of the proposed design procedure is illustrated through examples combining quasi-regular LDPC codes with MQAM and MPSK signaling schemes.
2007, 29(4): 888-891.
doi: 10.3724/SP.J.1146.2005.01134
Abstract:
In this paper, a new algorithm to construct the annihilators of Boolean function is introduced, and using the feature matrix of Boolean function, a method to judge whether a Boolean function has low degree annihilators is presented. Then, by studying the algebraic immunities of (5,1,3,12) rotation symmetric saturated best functions and a type of constructed functions, a class of functions are proved to be invariants of algebraic attacks, and this property is generalized in the end.
In this paper, a new algorithm to construct the annihilators of Boolean function is introduced, and using the feature matrix of Boolean function, a method to judge whether a Boolean function has low degree annihilators is presented. Then, by studying the algebraic immunities of (5,1,3,12) rotation symmetric saturated best functions and a type of constructed functions, a class of functions are proved to be invariants of algebraic attacks, and this property is generalized in the end.
2007, 29(4): 892-894.
doi: 10.3724/SP.J.1146.2005.01076
Abstract:
Recently, Yi et al..(2002) proposed an ID-based key agreement protocol for multimedia encryption. The protocol was built on both the Diffie-Hellman key exchange protocol and the RSA public key cryptosystem. Yi et al. analyzed the security of the protocol, and understood that the protocol is robust to the malicious attacks. However, this paper shows that the protocol is vulnerable to certain malicious attacks such as forging secret information and tampering exchanging messages and analyzes the reasons that the protocol suffers these attacks. This paper points out that it may be hard to improve the protocol due to the inherent flaw of the protocol.
Recently, Yi et al..(2002) proposed an ID-based key agreement protocol for multimedia encryption. The protocol was built on both the Diffie-Hellman key exchange protocol and the RSA public key cryptosystem. Yi et al. analyzed the security of the protocol, and understood that the protocol is robust to the malicious attacks. However, this paper shows that the protocol is vulnerable to certain malicious attacks such as forging secret information and tampering exchanging messages and analyzes the reasons that the protocol suffers these attacks. This paper points out that it may be hard to improve the protocol due to the inherent flaw of the protocol.
2007, 29(4): 895-897.
doi: 10.3724/SP.J.1146.2005.01086
Abstract:
Based on the security mechanism of the discrete logarithm, an ElGamal-like (t, n) threshold digital signature scheme with ability to identify cheaters is proposed in this paper. In the key generation phase, each participants public and private keys, and the group public key are negotiated among all the participants with no trusted party required. In the signature generation phase, no secure communication is needed between any two participants. This scheme provides the capability of detecting cheating and identifying the cheater that may be from the internal legal participants or the external attackers. The security of this scheme is based on the difficulty of solving the discrete logarithm problem. Analyses show that this scheme is a computationally secure and efficient scheme.
Based on the security mechanism of the discrete logarithm, an ElGamal-like (t, n) threshold digital signature scheme with ability to identify cheaters is proposed in this paper. In the key generation phase, each participants public and private keys, and the group public key are negotiated among all the participants with no trusted party required. In the signature generation phase, no secure communication is needed between any two participants. This scheme provides the capability of detecting cheating and identifying the cheater that may be from the internal legal participants or the external attackers. The security of this scheme is based on the difficulty of solving the discrete logarithm problem. Analyses show that this scheme is a computationally secure and efficient scheme.
2007, 29(4): 898-900.
doi: 10.3724/SP.J.1146.2005.01054
Abstract:
Study a new formula for amplitude discrete chaotic sequence to encrypt images under hardware devices conveniently from Logistic mapping formula for continuous amplitude, and generate a longer period sequences by exclusive OR algorithm with three amplitude discrete digital chaotic sequence in different periods. The image is encrypted by exclusive OR algorithm with the longer period image encrypting sequence and original image. The method is sensitive to initial values through simulation of encrypting and decrypting image. The result shows that the manner to generate amplitude discrete chaotic sequence is simple and more secure for information security, more convenient for hardware to encrypt images.
Study a new formula for amplitude discrete chaotic sequence to encrypt images under hardware devices conveniently from Logistic mapping formula for continuous amplitude, and generate a longer period sequences by exclusive OR algorithm with three amplitude discrete digital chaotic sequence in different periods. The image is encrypted by exclusive OR algorithm with the longer period image encrypting sequence and original image. The method is sensitive to initial values through simulation of encrypting and decrypting image. The result shows that the manner to generate amplitude discrete chaotic sequence is simple and more secure for information security, more convenient for hardware to encrypt images.
2007, 29(4): 901-905.
doi: 10.3724/SP.J.1146.2005.01088
Abstract:
Aiming at the shortcoming that traditional temporal logic such as LTL,CTL and CTL* regards protocols as close system to analyze, Dr Kremer(2003) proposes an ATL(Alternating-time Temporal Logic) logical method based on game to analyze fair E-commerce protocols, and analyses formally several typical protocols on their fairness and other properties. In this paper, ATL logical and its applications in formal analysis of E-commerce protocols are discussed, and Dr Kremer approach is ulteriorly extended to analyze security of protocols besides fairness. Finally, the strict formal analysis is made for ZDB protocol(1999) proposed by Zhou et al. With this new method, as a result there exists 2 possible attacks in the ZDB protocol under non-secrecy channels: leakiness of secret information and reply attacks.
Aiming at the shortcoming that traditional temporal logic such as LTL,CTL and CTL* regards protocols as close system to analyze, Dr Kremer(2003) proposes an ATL(Alternating-time Temporal Logic) logical method based on game to analyze fair E-commerce protocols, and analyses formally several typical protocols on their fairness and other properties. In this paper, ATL logical and its applications in formal analysis of E-commerce protocols are discussed, and Dr Kremer approach is ulteriorly extended to analyze security of protocols besides fairness. Finally, the strict formal analysis is made for ZDB protocol(1999) proposed by Zhou et al. With this new method, as a result there exists 2 possible attacks in the ZDB protocol under non-secrecy channels: leakiness of secret information and reply attacks.
2007, 29(4): 906-910.
doi: 10.3724/SP.J.1146.2005.00703
Abstract:
In this paper, a proxy-based mobile streaming media system in WCDMA network is introduced. Two metrics, mean network transferring cost and mean playback startup latency of mobile terminals, to evaluate performance of a cache allocation algorithm in proxy are presented. Expressions for corresponding saving and integrated saving of the metrics under Mobile Batcing (MBatching) stream transmission scheme are developed. A cache allocation algorithm that applies to the mobile streaming media system is put forward to make the total integrated saving of all the streaming media program maximal. Simulation results demonstrate that the algorithm can make the total integrated saving larger, save more network transferring cost and achieve higher byte-hit rate than another allocation algorithm.
In this paper, a proxy-based mobile streaming media system in WCDMA network is introduced. Two metrics, mean network transferring cost and mean playback startup latency of mobile terminals, to evaluate performance of a cache allocation algorithm in proxy are presented. Expressions for corresponding saving and integrated saving of the metrics under Mobile Batcing (MBatching) stream transmission scheme are developed. A cache allocation algorithm that applies to the mobile streaming media system is put forward to make the total integrated saving of all the streaming media program maximal. Simulation results demonstrate that the algorithm can make the total integrated saving larger, save more network transferring cost and achieve higher byte-hit rate than another allocation algorithm.
2007, 29(4): 911-914.
doi: 10.3724/SP.J.1146.2005.01100
Abstract:
A genetic algorithm of optimizing the order of arranging multicast services in optical network is proposed. Then the multicast trees are constructed and wavelengths are chosen by the optimized order to minimize the required number of wavelengths and multicast links in optical network. Three routing algorithms and the ameliorative effect of wavelength converters on resource optimization are compared. Simulations in NSFNet show that in sparse splitting network, when the number of multicast capable nodes is half of the number of total nodes, the resource optimization has been acceptable.
A genetic algorithm of optimizing the order of arranging multicast services in optical network is proposed. Then the multicast trees are constructed and wavelengths are chosen by the optimized order to minimize the required number of wavelengths and multicast links in optical network. Three routing algorithms and the ameliorative effect of wavelength converters on resource optimization are compared. Simulations in NSFNet show that in sparse splitting network, when the number of multicast capable nodes is half of the number of total nodes, the resource optimization has been acceptable.
2007, 29(4): 915-919.
doi: 10.3724/SP.J.1146.2005.01085
Abstract:
In 3G mobile networks, when the location information of a roaming user in a Gateway Location Register (GLR) is incorrect or obsolete, the location tracking before recovery will fail which severely degrades system performance. Traditional location recovery algorithms needed to occupy a great many long-distance signaling circuit resources. In order to reduce occupation on long-distance signaling circuit and GLR failure recovery interval, a new algorithm, referred to as reversal GLR failure recovery algorithm, is proposed in this paper. The proposed algorithm fully uses corresponding information in Visited Location Register(VLR) to avoid long-distance signaling cost between GLR and Home Location Register(HLR). Through performance analysis, the algorithm is proved to be feasible.
In 3G mobile networks, when the location information of a roaming user in a Gateway Location Register (GLR) is incorrect or obsolete, the location tracking before recovery will fail which severely degrades system performance. Traditional location recovery algorithms needed to occupy a great many long-distance signaling circuit resources. In order to reduce occupation on long-distance signaling circuit and GLR failure recovery interval, a new algorithm, referred to as reversal GLR failure recovery algorithm, is proposed in this paper. The proposed algorithm fully uses corresponding information in Visited Location Register(VLR) to avoid long-distance signaling cost between GLR and Home Location Register(HLR). Through performance analysis, the algorithm is proved to be feasible.
2007, 29(4): 920-923.
doi: 10.3724/SP.J.1146.2005.01063
Abstract:
The algorithm in this paper is based on the combination of quantum computation and genetic algorithm .The core is that using a qubit representation instead of binary, numeric, or symbolic representations and the dynamic adjusting quantum rotation gate strategy are applied to accelerate convergence. So it has better diversity and global search capacity than the conventional genetic algorithm. The results of solving the optimal problems of communication nets show that the efficiency of the new method is obviously higher than that of the conventional genetic algorithm.
The algorithm in this paper is based on the combination of quantum computation and genetic algorithm .The core is that using a qubit representation instead of binary, numeric, or symbolic representations and the dynamic adjusting quantum rotation gate strategy are applied to accelerate convergence. So it has better diversity and global search capacity than the conventional genetic algorithm. The results of solving the optimal problems of communication nets show that the efficiency of the new method is obviously higher than that of the conventional genetic algorithm.
2007, 29(4): 924-928.
doi: 10.3724/SP.J.1146.2006.00443
Abstract:
In mobile satellite networks, for the aim of shortening handover delay while using network resource efficiently, a proper handover scheme should be given. In this paper, by introducing the interrupting probability and the cost model of service, triggering schemes for path optimization in handover is given. Here, a novel mobile Satellite networks Minimum Cost Handover (SMCH) algorithm is proposed. This algorithm can assure the Quality of Service (QoS) parameters (such as delay) during the handover, as well as can minimize the handover cost. So it can use the network resource efficiently after the handover. Correlative simulation indicates that this novel algorithm is superior to other current algorithm in respect of guaranteeing the QoS and decreasing handover cost. Besides, it also has more adaptability and more practicability.
In mobile satellite networks, for the aim of shortening handover delay while using network resource efficiently, a proper handover scheme should be given. In this paper, by introducing the interrupting probability and the cost model of service, triggering schemes for path optimization in handover is given. Here, a novel mobile Satellite networks Minimum Cost Handover (SMCH) algorithm is proposed. This algorithm can assure the Quality of Service (QoS) parameters (such as delay) during the handover, as well as can minimize the handover cost. So it can use the network resource efficiently after the handover. Correlative simulation indicates that this novel algorithm is superior to other current algorithm in respect of guaranteeing the QoS and decreasing handover cost. Besides, it also has more adaptability and more practicability.
2007, 29(4): 929-932.
doi: 10.3724/SP.J.1146.2005.01135
Abstract:
This paper investigates the power control used in 3G. Then, presents a closed-loop distribution power control method based on estimator. Firstly the performance of this method is analyzed in theory, and a set of systematic scheme is given. Secondly a system model is established. Finally simulation results show that the convergence speed of this method is fast. The result is a strong ability of tracing wireless channel. So this method possesses a good perspective.
This paper investigates the power control used in 3G. Then, presents a closed-loop distribution power control method based on estimator. Firstly the performance of this method is analyzed in theory, and a set of systematic scheme is given. Secondly a system model is established. Finally simulation results show that the convergence speed of this method is fast. The result is a strong ability of tracing wireless channel. So this method possesses a good perspective.
2007, 29(4): 933-937.
doi: 10.3724/SP.J.1146.2005.01080
Abstract:
In this paper, mathematical expression of channel capacity as well as channel capacity loss due to feedback threshold setting are proposed, which is based on research on resource management in downlink multiuser OFDM systems and limited feedback theory. Three threshold setting schemes are proposed, which are from the aspects of feedback outage probability, capacity loss and feedback utility. Numerical results demonstrate that through setting threshold properly, the feedback can be decreased greatly at the cost of little capacity loss, leading to effective application of resource allocation algorithms in downlink multiuser OFDM systems.
In this paper, mathematical expression of channel capacity as well as channel capacity loss due to feedback threshold setting are proposed, which is based on research on resource management in downlink multiuser OFDM systems and limited feedback theory. Three threshold setting schemes are proposed, which are from the aspects of feedback outage probability, capacity loss and feedback utility. Numerical results demonstrate that through setting threshold properly, the feedback can be decreased greatly at the cost of little capacity loss, leading to effective application of resource allocation algorithms in downlink multiuser OFDM systems.
The Proof of the Trace Criterion for Space-Time Trellis Codes in Frequency-Selective Fading Channels
2007, 29(4): 938-941.
doi: 10.3724/SP.J.1146.2005.01059
Abstract:
When the product of the numbers of transmit and receive antennas is large, the design criterion for space-time trellis codes is the trace criterion. This criterion is originally designed for flat fading channels only. In this paper, it is proved that the trace criterion also can be used in frequency-selective fading channels. The simulation results show that the good codes according to the trace criterion have better performance than other codes, when the channel fading is frequency-selective.
When the product of the numbers of transmit and receive antennas is large, the design criterion for space-time trellis codes is the trace criterion. This criterion is originally designed for flat fading channels only. In this paper, it is proved that the trace criterion also can be used in frequency-selective fading channels. The simulation results show that the good codes according to the trace criterion have better performance than other codes, when the channel fading is frequency-selective.
2007, 29(4): 942-945.
doi: 10.3724/SP.J.1146.2005.00980
Abstract:
In an effort to utilize the advantage of using multiple antennas, transmit antenna selection for linear dispersion codes (LDC-TAS) is proposed in this paper. Three criteria are presented: maximum channel gain, maximum capacity and max-min post-SNR, for selecting the optimal transmit antennas when linear, coherent receiver is used over a slowly varying channel. Simulation results suggest that the max-min post-SNR criterion outperforms the other selection methods in a variety of modulation modes, such as QPSK, 8PSK and 16QAM. Compared with BLAST-TAS, under the same spectral efficiency, the proposed scheme shows significant diversity advantage. In low SNR environment, LDC-TAS is still better than STBC-TAS.
In an effort to utilize the advantage of using multiple antennas, transmit antenna selection for linear dispersion codes (LDC-TAS) is proposed in this paper. Three criteria are presented: maximum channel gain, maximum capacity and max-min post-SNR, for selecting the optimal transmit antennas when linear, coherent receiver is used over a slowly varying channel. Simulation results suggest that the max-min post-SNR criterion outperforms the other selection methods in a variety of modulation modes, such as QPSK, 8PSK and 16QAM. Compared with BLAST-TAS, under the same spectral efficiency, the proposed scheme shows significant diversity advantage. In low SNR environment, LDC-TAS is still better than STBC-TAS.
2007, 29(4): 946-949.
doi: 10.3724/SP.J.1146.2005.00712
Abstract:
A blind channel estimation method is presented for the Multiple-Input-Multiple-Output (MIMO) CDMA system employing long spreading codes. To estimate channel parameters, a decorrelating matched filter is applied as front-end at the receiver. The matched filter outputs consist of the signal space spanned by the users channel vector and the centers of the sets are extracted by clustering procedure. Then the channel parameters are estimated via the first-order statistics of the filter outputs. The K-mean clustering algorithm is improved in class centers initialization for fast convergence. The proposed method has low computational complexity. Simulation results illustrate the effectiveness of the proposed method and the robustness to channel order overestimation.
A blind channel estimation method is presented for the Multiple-Input-Multiple-Output (MIMO) CDMA system employing long spreading codes. To estimate channel parameters, a decorrelating matched filter is applied as front-end at the receiver. The matched filter outputs consist of the signal space spanned by the users channel vector and the centers of the sets are extracted by clustering procedure. Then the channel parameters are estimated via the first-order statistics of the filter outputs. The K-mean clustering algorithm is improved in class centers initialization for fast convergence. The proposed method has low computational complexity. Simulation results illustrate the effectiveness of the proposed method and the robustness to channel order overestimation.
2007, 29(4): 950-953.
doi: 10.3724/SP.J.1146.2005.00713
Abstract:
In this paper, a novel optimization criterion is presented for Adaptive Modulation (AM) Multi-Input and Multi-Output (MIMO) system, which aims at finding out proper modulation and power allocation parameters to reach the required Quality of Services (QoS), while the overall transmission power is minimized. The closed-form solution under perfect Channel State Information (CSI) and the practical algorithm under imperfect CSI are given. The simulation results show that the proposed criterion is very helpful to make cross-layer optimization by taking the QoS requirements into account much easier.
In this paper, a novel optimization criterion is presented for Adaptive Modulation (AM) Multi-Input and Multi-Output (MIMO) system, which aims at finding out proper modulation and power allocation parameters to reach the required Quality of Services (QoS), while the overall transmission power is minimized. The closed-form solution under perfect Channel State Information (CSI) and the practical algorithm under imperfect CSI are given. The simulation results show that the proposed criterion is very helpful to make cross-layer optimization by taking the QoS requirements into account much easier.
2007, 29(4): 954-958.
doi: 10.3724/SP.J.1146.2005.01077
Abstract:
In this paper, the requirements of training sequence for channel estimation in SC-FDE systems are discussed, and the customarily used training sequence for channel estimation in OFDM systems can not be used in SC-FDE systems directly is pointed out. By analyzing, it is concluded that Newmann sequence is very suitable for SC-FDE systems. Without considering the energy lost of CP, the LS estimation performance bound is given. Theoretical analysis and simulation results show that this bound can be achieved by using Newmann sequence.
In this paper, the requirements of training sequence for channel estimation in SC-FDE systems are discussed, and the customarily used training sequence for channel estimation in OFDM systems can not be used in SC-FDE systems directly is pointed out. By analyzing, it is concluded that Newmann sequence is very suitable for SC-FDE systems. Without considering the energy lost of CP, the LS estimation performance bound is given. Theoretical analysis and simulation results show that this bound can be achieved by using Newmann sequence.
2007, 29(4): 959-962.
doi: 10.3724/SP.J.1146.2005.01182
Abstract:
A new approach for interference suppression in DSSS communication is introduced aim at the shortcomings of the method in transform domain. It combines interference detection in transform domain with interference suppression using open-loop adaptive FIR excision filtering in time domain. The expression of receiver signal-to-noise ratio is derived and it is maximized by adjusting filter coefficients depend on the interference power and its frequency information. The numerical simulation demonstrates that the proposed method is better than FFT method in transform domain in both single-tone and multi-tone interference environment and is effective and efficient to narrowband interferences.
A new approach for interference suppression in DSSS communication is introduced aim at the shortcomings of the method in transform domain. It combines interference detection in transform domain with interference suppression using open-loop adaptive FIR excision filtering in time domain. The expression of receiver signal-to-noise ratio is derived and it is maximized by adjusting filter coefficients depend on the interference power and its frequency information. The numerical simulation demonstrates that the proposed method is better than FFT method in transform domain in both single-tone and multi-tone interference environment and is effective and efficient to narrowband interferences.
2007, 29(4): 963-966.
doi: 10.3724/SP.J.1146.2005.01042
Abstract:
The Bit Error Rate (BER) performance of a noncoherent Fast Frequency-Hopped Binary orthogonal Frequency-Shift-Keying (FFH/BFSK) Spread Spectrum (SS) receiver with Adaptive Gain Control (AGC) is investigated in the presence of Partial-Band Jamming (PBJ) and Additive White Gaussian Noise (AWGN) over frequency non-selective slow Nakagami-fading channels. Exact BER expressions in a one fold integral is derived. The effects of arbitrarily values of fading parameter and diversity level on system performance are considered. Numerical results compare the worst case BER performance of the AGC receiver with that of the Product Combining (PC) receiver. Compared with the former BER analysis method，the advantage of this paper lies in the uniform analysis mode so that the analysis of the performance of the system under different fading channels is simply a analysis step。
The Bit Error Rate (BER) performance of a noncoherent Fast Frequency-Hopped Binary orthogonal Frequency-Shift-Keying (FFH/BFSK) Spread Spectrum (SS) receiver with Adaptive Gain Control (AGC) is investigated in the presence of Partial-Band Jamming (PBJ) and Additive White Gaussian Noise (AWGN) over frequency non-selective slow Nakagami-fading channels. Exact BER expressions in a one fold integral is derived. The effects of arbitrarily values of fading parameter and diversity level on system performance are considered. Numerical results compare the worst case BER performance of the AGC receiver with that of the Product Combining (PC) receiver. Compared with the former BER analysis method，the advantage of this paper lies in the uniform analysis mode so that the analysis of the performance of the system under different fading channels is simply a analysis step。
2007, 29(4): 967-970.
doi: 10.3724/SP.J.1146.2005.01056
Abstract:
Packet loss led to great degradation of picture quality, when video stream transmitted in error-prone channel. RPS (Reference picture selection) could improve picture quality by selecting suitable reference picture, but RPS greatly increased computation complexity. In this paper one low complex RPS optimal method was proposed. First error concealment steps in decoder was tracked in encoder to reconstruct error picture; second only error reconstructed picture and the preceding picture were taken as optional reference pictures; third picture difference variance was computed by linear prediction when processing R-D optimization. Through above means time of motion estimation was reduced, and then computation complexity was greatly decreased. Experiment result shows the method greatly lower encoders complexity, while only loss small picture quality.
Packet loss led to great degradation of picture quality, when video stream transmitted in error-prone channel. RPS (Reference picture selection) could improve picture quality by selecting suitable reference picture, but RPS greatly increased computation complexity. In this paper one low complex RPS optimal method was proposed. First error concealment steps in decoder was tracked in encoder to reconstruct error picture; second only error reconstructed picture and the preceding picture were taken as optional reference pictures; third picture difference variance was computed by linear prediction when processing R-D optimization. Through above means time of motion estimation was reduced, and then computation complexity was greatly decreased. Experiment result shows the method greatly lower encoders complexity, while only loss small picture quality.
2007, 29(4): 971-974.
doi: 10.3724/SP.J.1146.2005.00720
Abstract:
This paper firstly discusses the problem when using Partial Transmit Sequence (PTS) in the Peak-to-Average Power Ratio (PAPR) reduction of real-valued OFDM systems.Secondly, the Adjacent-partition PTS (APTS) and Interleaved-partition PTS (IPTS) are proposed for real-valued OFDM systems. The simulation results confirm the effectiveness of APTS and IPTS in PAPR reduction for real value OFDM systems.
This paper firstly discusses the problem when using Partial Transmit Sequence (PTS) in the Peak-to-Average Power Ratio (PAPR) reduction of real-valued OFDM systems.Secondly, the Adjacent-partition PTS (APTS) and Interleaved-partition PTS (IPTS) are proposed for real-valued OFDM systems. The simulation results confirm the effectiveness of APTS and IPTS in PAPR reduction for real value OFDM systems.
2007, 29(4): 975-978.
doi: 10.3724/SP.J.1146.2005.01093
Abstract:
This paper proposes a new approach to reduce the Peak-to-Average power Ratio(PAR) value of multi-carrier/OFDM with a new kind of adaptive soft feedback Stochastic Hopfield Neural Network (S-HNN). By adopting new neural output function and random state disturbance, the system performance is improved greatly. Furthermore, it can be implemented easily compared to the traditional HNN method. By parameter adjustment, the lowest PAR can be found. So it is an effective and practical algorithm for OFDM system.
This paper proposes a new approach to reduce the Peak-to-Average power Ratio(PAR) value of multi-carrier/OFDM with a new kind of adaptive soft feedback Stochastic Hopfield Neural Network (S-HNN). By adopting new neural output function and random state disturbance, the system performance is improved greatly. Furthermore, it can be implemented easily compared to the traditional HNN method. By parameter adjustment, the lowest PAR can be found. So it is an effective and practical algorithm for OFDM system.
2007, 29(4): 979-982.
doi: 10.3724/SP.J.1146.2005.01104
Abstract:
A novel scheme for unitary space-time block coding with variable transmit diversity gain is proposed for TFSK (Time-Frequency-Shift Keying) systems. Each modulated TFSK symbol is divided into two orthogonal sub-symbols, and the new scheme is constructed by differently combining the sub-symbols with the different transmit diversity gain able to be achieved by noncoherent processing at the receivers. The results of computer simulation show that the new scheme has advantage of anti-flat-fading over Alamouti space-time block coding and space-time frequency-shift keying, and ST-TFSK systems with two diversity gain enjoy the superior coding rate and the inferior anti-fading performance to the ones with four diversity gain, which approve the theoretical analysis
A novel scheme for unitary space-time block coding with variable transmit diversity gain is proposed for TFSK (Time-Frequency-Shift Keying) systems. Each modulated TFSK symbol is divided into two orthogonal sub-symbols, and the new scheme is constructed by differently combining the sub-symbols with the different transmit diversity gain able to be achieved by noncoherent processing at the receivers. The results of computer simulation show that the new scheme has advantage of anti-flat-fading over Alamouti space-time block coding and space-time frequency-shift keying, and ST-TFSK systems with two diversity gain enjoy the superior coding rate and the inferior anti-fading performance to the ones with four diversity gain, which approve the theoretical analysis
2007, 29(4): 983-986.
doi: 10.3724/SP.J.1146.2005.00715
Abstract:
This paper investigates a new method for synthesis of the hexagonal antenna array. The local convergence of the nonlinear least-square method is restricted by selecting several initial values, such can achieve the global optimization of the antenna array. According to the elements symmetry distributed in axis, the scattering coeffecient of whole antenna array can be achieved by calculating part of elements, and abase the influence by mutual coupling . Simulation results show the pattern of antenna array approaches the objective pattern in the least square sense.
This paper investigates a new method for synthesis of the hexagonal antenna array. The local convergence of the nonlinear least-square method is restricted by selecting several initial values, such can achieve the global optimization of the antenna array. According to the elements symmetry distributed in axis, the scattering coeffecient of whole antenna array can be achieved by calculating part of elements, and abase the influence by mutual coupling . Simulation results show the pattern of antenna array approaches the objective pattern in the least square sense.
2007, 29(4): 987-990.
doi: 10.3724/SP.J.1146.2005.00723
Abstract:
This paper presents how to synthesize asymmetric linear arrays using genetic algorithms. The asymmetric configuration is an available degree of freedom to control the characters of thinned arrays. In this paper, the Genetic Algorithms (GA) determines which elements are turned off in a periodic array to yield the lowest maximum Relative SideLobe Level (RSLL). Fitness function of GA for asymmetric linear arrays synthesis is designed. Simulation results show that the optimized asymmetric linear arrays which lack the design constraint of bilateral symmetry can not only obtain lower sidelobes, but also weaken the deterioration of scanning beam if the thinned arrays are made up of the directional elements.
This paper presents how to synthesize asymmetric linear arrays using genetic algorithms. The asymmetric configuration is an available degree of freedom to control the characters of thinned arrays. In this paper, the Genetic Algorithms (GA) determines which elements are turned off in a periodic array to yield the lowest maximum Relative SideLobe Level (RSLL). Fitness function of GA for asymmetric linear arrays synthesis is designed. Simulation results show that the optimized asymmetric linear arrays which lack the design constraint of bilateral symmetry can not only obtain lower sidelobes, but also weaken the deterioration of scanning beam if the thinned arrays are made up of the directional elements.
2007, 29(4): 991-993.
doi: 10.3724/SP.J.1146.2005.00710
Abstract:
Design of broadband circularly polarized microstrip patch antenna which is coupled by two H-shaped apertures is presented in this paper. Based upon the proximity coupling feed by the Wilkinson power divider, the proposed antenna can have a standing wave bandwidth of about 47.5% and the axial-ratio value within 3dB is about 50%. The front-to-back ratio of the antenna radiation pattern is better than #61485;21dB, which indicate the realization of the good circularly polarized and low backward radiation level characteristics.
Design of broadband circularly polarized microstrip patch antenna which is coupled by two H-shaped apertures is presented in this paper. Based upon the proximity coupling feed by the Wilkinson power divider, the proposed antenna can have a standing wave bandwidth of about 47.5% and the axial-ratio value within 3dB is about 50%. The front-to-back ratio of the antenna radiation pattern is better than #61485;21dB, which indicate the realization of the good circularly polarized and low backward radiation level characteristics.
2007, 29(4): 994-997.
doi: 10.3724/SP.J.1146.2005.01045
Abstract:
A new method of improving the gain of circular waveguide array antenna is presented in this paper. The electromagnetic characteristics of metamaterial and high-gain circular waveguide antenna with the metamaterial structure are studied by using the numerical simulation method, which are also compared with those of the conventional antenna. The simulation results show that this method is effective and the metamaterial structure can realize congregating the radiation energy, so the gain of the array antenna is increased and the side lobe level is decreased.
A new method of improving the gain of circular waveguide array antenna is presented in this paper. The electromagnetic characteristics of metamaterial and high-gain circular waveguide antenna with the metamaterial structure are studied by using the numerical simulation method, which are also compared with those of the conventional antenna. The simulation results show that this method is effective and the metamaterial structure can realize congregating the radiation energy, so the gain of the array antenna is increased and the side lobe level is decreased.
2007, 29(4): 998-1001.
doi: 10.3724/SP.J.1146.2005.01710
Abstract:
According to receivers dynamic environment, high dynamic GPS signal simulator can precisely generate GPS signal that the receiver get. GPS signal simulator has many technology request, the intensity of the signal is a key technology in the high dynamic GPS receivers research and development. After the GPS signal is demodulated, the Signal Noise Ratio(SNR) of the receiver is analyzed in this paper. On the basis of above, the paper also derives how the signal generated by GPS Signal Simulator reflects truly the GPS signal and outside noise. Experimentation result proves the effectiveness of the method mentioned above.
According to receivers dynamic environment, high dynamic GPS signal simulator can precisely generate GPS signal that the receiver get. GPS signal simulator has many technology request, the intensity of the signal is a key technology in the high dynamic GPS receivers research and development. After the GPS signal is demodulated, the Signal Noise Ratio(SNR) of the receiver is analyzed in this paper. On the basis of above, the paper also derives how the signal generated by GPS Signal Simulator reflects truly the GPS signal and outside noise. Experimentation result proves the effectiveness of the method mentioned above.
2007, 29(4): 1002-1004.
doi: 10.3724/SP.J.1146.2005.01145
Abstract:
Electric field sensors used at present are only capable of measuring one or two dimensional values of electric field intensity. A miniaturized electric field sensor used for measuring three dimensional electric field is introduced, which is composed of axial(Z) and radial(X, Y) electric field measuring units, driving unit and circuit unit. The practicability of the three dimensional electric field sensor is demonstrated, and it is shown that the theoretical prediction and experimental result are in good agreement.
Electric field sensors used at present are only capable of measuring one or two dimensional values of electric field intensity. A miniaturized electric field sensor used for measuring three dimensional electric field is introduced, which is composed of axial(Z) and radial(X, Y) electric field measuring units, driving unit and circuit unit. The practicability of the three dimensional electric field sensor is demonstrated, and it is shown that the theoretical prediction and experimental result are in good agreement.
2007, 29(4): 1005-1008.
doi: 10.3724/SP.J.1146.2005.01126
Abstract:
In this paper an improved solution to the design of Cascaded-Integrator-Comb (CIC) filter is proposed, in which the overall transfer function is factorized to recursive and non-recursive parts. The cascade factors of two parts can be adjusted independently. The sharpening is applied to recursive part to correct the passband droop, and decimation factor is moved prior to the sharpening of recursive part by the use of equivalent transform to operate at a low rate. Polyphase decomposition is applied to non-recursive part to realize high-speed filtering. Computer simulation shows that the modified CIC filter has a frequency response comparable to that of sharpening CIC filters while design flexibility is increased. The effect of the cascade factor of recursive and non-recursive parts on the modified CIC frequency response is discussed in terms of passband droop and alias rejection.
In this paper an improved solution to the design of Cascaded-Integrator-Comb (CIC) filter is proposed, in which the overall transfer function is factorized to recursive and non-recursive parts. The cascade factors of two parts can be adjusted independently. The sharpening is applied to recursive part to correct the passband droop, and decimation factor is moved prior to the sharpening of recursive part by the use of equivalent transform to operate at a low rate. Polyphase decomposition is applied to non-recursive part to realize high-speed filtering. Computer simulation shows that the modified CIC filter has a frequency response comparable to that of sharpening CIC filters while design flexibility is increased. The effect of the cascade factor of recursive and non-recursive parts on the modified CIC frequency response is discussed in terms of passband droop and alias rejection.
2007, 29(4): 1009-1012.
doi: 10.3724/SP.J.1146.2005.01061
Abstract:
Parallel simulation techniques are often employed to meet the computational requirements of large hardware simulations in order to reduce simulation time. In addition, partitioning for parallel simulations has been shown to be vital for achieving higher simulation throughput. This paper presents the design and implementation of a new partitioning algorithm based on a multilevel heuristic, also presents the speed up of applying this to a real hardware parallel simulation system Discovery. This algorithm attempts to balance load and reduce the whole simulation network communication to improve performance. The experimental results obtained from the benchmarks indicate that this algorithm yields better partitions than other partitioning algorithms for better simulation performance.
Parallel simulation techniques are often employed to meet the computational requirements of large hardware simulations in order to reduce simulation time. In addition, partitioning for parallel simulations has been shown to be vital for achieving higher simulation throughput. This paper presents the design and implementation of a new partitioning algorithm based on a multilevel heuristic, also presents the speed up of applying this to a real hardware parallel simulation system Discovery. This algorithm attempts to balance load and reduce the whole simulation network communication to improve performance. The experimental results obtained from the benchmarks indicate that this algorithm yields better partitions than other partitioning algorithms for better simulation performance.
2007, 29(4): 1013-1016.
doi: 10.3724/SP.J.1146.2005.01049
Abstract:
Vias are one of the most common interconnection structures used in modern high speed Printed Circuit Board (PCB), which would induce a series of problems such as loss of signal integrity when transmitting signal especially high speed signal. So it is very important that vias are modeled and simulated accurately, speedily, efficiently. The network cascade theory combined with a semi-analytical full wave approach based on Foldy-Lax equation is used to model vias in this paper. In single-layer vertical vias, the Fold-Lax equations of multiple scattering among the cylindrical vias are given. The exciting field coefficients of cylindrical vias are solved. The scattering matrix of coupling among single-layer vias is calculated. By multi-port network cascade theory, the scattering matrix of coupling among multi-layer vertical vias is obtained. The results of scattering matrix are given for 4-layer vertical vias, which show that the method presented in this paper is correct and valid.
Vias are one of the most common interconnection structures used in modern high speed Printed Circuit Board (PCB), which would induce a series of problems such as loss of signal integrity when transmitting signal especially high speed signal. So it is very important that vias are modeled and simulated accurately, speedily, efficiently. The network cascade theory combined with a semi-analytical full wave approach based on Foldy-Lax equation is used to model vias in this paper. In single-layer vertical vias, the Fold-Lax equations of multiple scattering among the cylindrical vias are given. The exciting field coefficients of cylindrical vias are solved. The scattering matrix of coupling among single-layer vias is calculated. By multi-port network cascade theory, the scattering matrix of coupling among multi-layer vertical vias is obtained. The results of scattering matrix are given for 4-layer vertical vias, which show that the method presented in this paper is correct and valid.
