最新刊期
卷 33 ， 期 7 ， 2005
- 摘要：Mobile ad hoc networks are applied in a wider fields and its applying is becoming more and more complex.So,different application scenarios have different deployments of MANET in order to get the more optimal performance.Network connectivity and energy saving are the key factors to consider.In order to construct the mobile ad hoc networks more reasonably and efficiently,this paper defines a type of application model of MANET,and gives three kinds of MANET application scenarios according to such model,and proposes a MANET deploying method,especially researches the wireless transceiver deploying scheme.关键词：mobile ad hoc networks;random graph;mobility model;random waypoint2|910|3更新时间：2025-07-16
- 摘要：As more and more services with definite QoS requirements go into the Internet,ISP's face a severe challenge that how maximum number of users can be admitted into networks with QoS guarantees.In this paper,a mathematical model is built first for describing the problem of optimum network resource allocation.Secondly,it is proved that the problem above can be simplified into an easy optimization programming,the unique optimal solution to which is just that of the original problem,and whose optimal value is the upper bound of the number of admitted users.At last,a novel path level network resource allocation algorithm,ERA algorithm,is developed based on the characteristics of that optimal solution.The ERA algorithm possesses the good simplicity and efficiency,and the numerical results also show that it outperforms other algorithms dealing with the same problem.关键词：network resource allocation;QoS partition;optimization programming;equal ratio allocation (ERA)2|707|0更新时间：2025-07-16
- 摘要：An adaptive neural network model for VBR video traffic prediction is proposed in this paper.Firstly,adaptive training and pruning algorithm based on Extended Kalman Filtering(EKF) approach is used to train the Time Delay Neural Network(TDNN).By pruning the unimportant hidden weights,the corresponding redundant hidden neurons can be deleted,as a result a compact TDNN architecture can be obtained.The pruning process results in better generalization ability and lower computational complexity for the online stage.During on-line training stage,the TDNN's weights will be updated using Recursive Least Square(RLS) algorithm according to current prediction error.Since EKF and RLS are second order algorithms,they can estimate the learning step automatically,faster convergence speed and more precise prediction can be obtained.By simulation and comparison,the adaptive neural network model proposed in this paper is shown to be promising and practically feasible in obtaining the best adaptive prediction of real-time VBR video traffic.关键词：video communication;time delay neural network;extended Kalman filtering;recursive least square.2|1281|1更新时间：2025-07-16
- 摘要：To provide a more efficient wireless MAC protocol,Busy Queue Polled Only (BQPO) protocol,which is based on cyclic polling scheme,is presented.It can provide delay QoS and stability for the time-bounded services.The mathematical model of BQPO system and the mean value of message waiting time are explicitly obtained.The performance of BQPO is simulated and compared with PCF scheme.The results show that the simulation is in concordance with the theoretical analysis.The BQPO scheme can provide higher stability and better delay QoS than PCF scheme.关键词：wireless network;medium access control (MAC);QoS;cyclic polling2|805|2更新时间：2025-07-16
- 摘要：Traditional packet scheduling algorithms for high-speed downlink shared channel are investigated with the consideration of streaming services and wideband wireless channel in beyond 3rd generation mobile communication system.A Priority-Based Fairness Scheduling (PBFS) algorithm is proposed for streaming services transmission and system throughput enhancement.The PBFS algorithm makes packet scheduling scheme in downlink shared channel based on the users' priorities,which are dynamically adjusted according to the quality of wireless channel and the QoS requirement of streaming services.Simplified PBFS (S-PBFS) is also derived.Simulation results show that the new scheduling algorithm has the benefits of lower complexity,higher wireless channel utilization efficiency under the constraint of transfer delay,compared to the traditional scheduling algorithms.2|923|5更新时间：2025-07-16
- 摘要：Present researches of parallel frame synchronization schemes are mostly focused on one or another special application,and the conclusions lack general significance.Some new frame synchronization problems-such as 66B code synchronization in 10 gigabit ethernet-have their new characteristics.This paper proposes a new parallel frame synchronization scheme,namely MCSCI,which uses a method featured by continuity validation to perform searching of frame alignment word.When MCSCI is used in 66B code synchronization,optimal performance is acquired at the expense of smaller chip-area,compared with present schemes.Based on theoretical analysis and computer simulations,this paper studies the performances of proposed and present schemes under many suits of parameters,and the results show that MCSCI has broad usage.关键词：frame synchronization;parallel;continuity2|1023|3更新时间：2025-07-16
- 摘要：In this paper,the sensitivities of the non-zero bits in the codewords with low weights in Turbo codes to the interruptions are discussed and the result is that the lower weight the higher sensitivity.Theoretical analysis shows that through the protections on such key-bits that have high sensitivities,the minimal weight of the codes can be improved apparently.The simulations also give out the supported results:The BER has been highly improved for code rate both 1/3 and 1/2.关键词：Turbo codes;distribution of code weight;BER2|1012|0更新时间：2025-07-16
- 摘要：In this paper,a method for watermark detection based on error control codes and a method for determining threshold for watermark detection are proposed.The basic idea is that watermark be encode with ECC,and then the extracted watermark subtract the feedback one,finally compare the subtractive result with the threshold selected for watermark detection.Thus the existence or not of watermark can be detected.The Turbo code of error control codes is used in the experiment.The simulation results using an algorithm based on DWT show that the errors of watermark image presented during the transportation is reduced greatly and the robustness of it is enhanced with the method proposed.关键词：error control codes;watermark detection;Turbo code2|1010|2更新时间：2025-07-16
- 摘要：Utilizing the echoic intension and distribution of different organizations and local details,ultrasonic image catches the important medical pathological changes.However ultrasonic image may be contaminated by the speckle noise in its forming process,which degrades image quality specially concealing some details,and works disadvantages to image segmentation,character extraction and image recognition,disease diagnosis and quantitative analysis.Using local coordinate transform,the first and second order normal derivatives of edge and local detail and the hyperbolic tangent function,also combining the anisotropic diffusion equation,we have put forth an ultrasonic image denoising and edge enhancement scheme,which can preserve edges,local details and ultrasonic echoic bright strips on denoising.This has been indicated theoretically and experimentally.关键词：ultrasonic image;anisotropic diffusion;normal derivatives;hyperbolic tangent function;denoising;edge enhancement2|2960|14更新时间：2025-07-16
- 摘要：Fourier transform and sampling theorem are the two fundamental problems in signal processing fields.The traditional sampling theorem clarifies the sampling and reconstruction theories of the bandlimited signals with Fourier transform.The fractional Fourier transform (FRFT) is a generalization of the ordinary Fourier transform.And the sampling theories related to it have not been completed yet,so the sampling theorem needs to be restudied in the FRFT domain.In this paper,we first obtain the FRFT of the uniform impulse-train sampled signals,and based on it,we deduce sampling theorem and reconstruction formula for bandpass and lowpass signals with FRFT.Our work is a generalization of the classical results and will enrich the theoretical system of the fractional Fourier transform.关键词：fractional Fourier transform;bandpass signal;sampling theorem;reconstruction formula2|1651|14更新时间：2025-07-16
- 摘要：A two-layer support vector classifier model with rejection feature is proposed in this paper.Firstly the sphere support vectors of each class to describe the distribution of the sample were obtained by searching all the sphere boundaries containing the samples of each class.Then the input pattern of no-object classes could be rejected by the first support vector domain description (SVDD).If a pattern is accepted by the first SVDD,the second layer of support vector classifier (SVC) with maximum margin between two classes will be used for classification.In addition,Instead of the traditional quadratic programming,multiplicative iterative updates rule is used to solve the optimizing problems in SVDD of the first layer and the SVC in second layer.Compared to the tradition algorithm of the support vector machine,the new method improves greatly the computational speed of optimization.Experimental results demonstrate that the method of two-Layer support vector classifier with Rejection Feature is feasible and it could be applicable in many real pattern recognition fields.关键词：support vector classifier;kernel function;support vector data description;rejection performance2|928|2更新时间：2025-07-16
- 摘要：Frequency estimator which based on two-order adaptive notch filter is the one frequently used for sinusoid on engineering,with a precondition that there is a small frequency bias of reference signal to input signal.With frequency bias increasing,estimated bias and variance of adaptive frequency estimator (AFE) enlarge.In this paper properties of AFE and influences of frequency bias are analyzed,and formula on estimated variance lower bound is derived,and condition which is required by the bound is got.Frequency auto-tracking adaptive frequency estimator (FATAFE) is brought forward.Simulation and theoretical results show that under the same conditions FATAFE decreases obviously estimated bias and variance relative to AFE,and under medium signal-to-noise ratio condition estimated variance of FATAFE can be declined to one percent of that of AFE.FATAFE realizes unbiased estimation and its estimated variance approaches to theoretical lower bound if only signal-to-noise ratio is not very low.关键词：frequency auto-tracking;adaptive frequency estimator;frequency bias;variance;lower bound2|1110|3更新时间：2025-07-16
- 摘要：Frequency-selective quantification can not only apply to many applications of magnetic resonance spectroscopy (MRS) but also improve the speed and accuracy of parameters estimation of selected spectral components.Thus,we presented a new frequency-selective method for MRS quantification,which estimated the nonlinear and linear parameters of the selected components based on total least squares and forward-backward APES respectively.From the experiments on both simulate data and MRS data in vivo,we can see that the computing speed and estimation stabilization of our method are obviously superior to those of the classical quantitative methods HSVD and HTLS;furthermore,its performance of parameters estimation is better than that of the frequency-selective method SELF-SVD proposed by Stoica et al.关键词：total least squares;magnetic resonance spectroscopy;frequency-selective method;quantification2|809|0更新时间：2025-07-16
- 摘要：The concept of "the Wavelet Spectral correlation function(WSCF)" is proposed.The property of WSCF and the relation between Spectral correlation function(SCF) and WSCF are analyzed briefly.The WSCF of the fractal stochastic noise is deduced based on the analysis of WSCF of white gauss noise(WGN) and the SCF of WGN.And the property of fractal stochastic noise in the WSC domain is analyzed.Considering the actual sea clutter,a fractal noise AM-FM model is proposed.The WSCF of the sea clutter is analyzed,which presents the advantage of the WSCF in processing the sea clutter.The signal recognition of pseudo random code pulse trains under the environment of fractal noise with WSCF is simulated.It is found that the method can effectively eliminate fractal noise and accurately extract the signal parameters.关键词：wavelet spectral correlation;fractal noise;sea clutter2|885|2更新时间：2025-07-16
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New and Low Complexity Companding Technique for Reducing Peak-to-Average Power Ratio of OFDM Signals
摘要：A new companding scheme is proposed to reduce the Peak-to-Average Power Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals.The characteristics and performance of system with conventional and new companding scheme are compared.The proposed scheme is illustrated in detail and analyzed in terms of reducing PAPR,computational complexity and improvement in BER performance in OFDM system.Our simulation results confirm that the suggested scheme exhibits a good ability to reduce PAPR and can outperform with lower computational complexity than conventional companding scheme substantially.关键词：lower complexity;companding transform;OFDM;PAPR2|960|6更新时间：2025-07-16 - 摘要：Data Replication technologies have been widely applied in data grid systems to improve the performance of grid applications,and replica creation strategy is one of the key technologies of Data Replication.A new concept Data Grid of Humble Birth (DGHB) is proposed for enterprise-oriented data grid applications.And a replica creation strategy - Storage Alliance based Double-layer Dynamic Replica crEation Strategy (SADDRES) is also proposed.The simulation results on OptorSim prove that the SADDRES is more efficient than other replica creation strategies for enterprise-oriented data grid applications.关键词：enterprise-oriented data grid;storage alliance;replication;replica creation strategy2|1060|8更新时间：2025-07-16
- 摘要：A type of grating lobe filter is designed based on the azimuth shift character of grating lobe as the change of frequency and statistical character of peak in time-frequency domain.Filtering to traditional wide-band beam output can suppress the effects of grating lobe on arrays validly using this filter.The better experimental results are obtained in the bandwidth corresponding to d/λ=0.8~1.3 on a equally sparse line array.关键词：frequency retrieval;grating lobe suppression;estimation of DOA2|852|0更新时间：2025-07-16
- 摘要：Recognition correct rate and noise robust property are indeed important for speaker recognition research,but the response rate of recognition is also a key factor for a speaker recognition system when applied in the real world.Owing to this,we propose a novel speaker identification approach based on speaker clustering,namely Hierarchical Speaker Identification (HSI).It can increase the running speed greatly for speaker identification systems,and the more the number of registered speakers is,the faster the HSI system runs than the Conventional Speaker Identification (CSI) system.Simultaneously,its counterpart for speaker verification based on speaker clustering,can reduce the rates of false rejection and false acceptance efficiently to improve the capability of verification.A new method is also presented here called reliability scoring.The experiments show that speaker clustering based algorithms can run faster 3.5 times than original approach for the speaker identification and is 53.75% deduction of equal or minimal error rates for the speaker verification on average.关键词：speaker identification;speaker verification;speaker clustering;cohort set;reliability scoring2|1072|3更新时间：2025-07-16
- 摘要：Brain-computer interfaces provide a direct communication and control channel for sending messages and instructions from brain to external computers or other electronic devices.Using the non-muscular channel,subjects with severe neuromuscular dysfunction can directly express their thought and manipulate the external devices without using human language and actions.This will greatly enhance the ability of these subjects to manage external event and will improve their living quality.Brain-computer interface technology is an interdisciplinary technology integrating neurology,signal collection,signal processing,pattern recognition and more other relevant techniques.In the present paper,we review the development,the rationale and the methodology of BCI's technology and the major limitations in the BCI's implementation and applications,and then discuss some vital aspects that may be conducted in the future investigations.关键词：brain-computer interface;electroencephalogram;event-related potentials;feature extraction;communication83|8971|26更新时间：2025-07-16
- 摘要：We made a general model to analyze switching throughput of traffic manager in core routers.By designing a real traffic manager which uses the OC-48c interface,we analyze the whole system and point out that at least four HSSLs should be employed per CSIX interface when using Vitesse's GigaStream switch chip set.Meanwhile,at the CSIX interface,the CFrame should be constructed according to the actual size of the last cell of each IP packet.Above principles can guarantee forwarding IP packets at line rate.We give a general relationship between throughput and buffering scheme of IP packets in the external memory,which is useful in the design of switch fabric in core routers.关键词：throughput;GigaStream;CSIX interface;traffic manager2|710|0更新时间：2025-07-16
- 摘要：For downlink transmission,known pilot symbols are usually used to evaluate the channel characters through the common pilot channel.Comparing to traditional CDMA,LS spreading codes in LAS-CDMA (Large Area Code Division Multiple Access)have IFW (Interference Free Window).Thus when pilot symbols are used,AWGN (Additive White Gaussian Noise)is the main obstacle to the accuracy.To suppress the noise degradation,in this paper,a new channel estimation method for LAS-CDMA system is introduced.In the proposed method,the channel coefficients obtained through common pilot channel are first fed to a regression process and these updated coefficients are then for the corresponding data symbol recovery.Linear and nonlinear regression schemes are both considered according to vehicle speeds and regression process lengths over the ITU-VA channel.Simulation results prove that this method can improve the channel estimation accuracy and system BER (Bit Error Rate)performance greatly.关键词：LAS-CDMA(large area code division multiple access);channel estimation;linear regression;nonlinear regression2|697|0更新时间：2025-07-16
- 摘要：The characteristics of mobile agents make them ideal for electronic commerce applications in open networks.Security is a fundamental precondition for the acceptance of mobile agent systems.In this paper,we analyze the effective route protection based on mobile agents given by Domingo J.and point that the protocol has security threat:it is not against collusion of malicious hosts.After that,using hash function,a secure itinerary protection of mobile agents based on Merkle trees is presented.Its and computational cost are discussed in detail.The results show that our method not only satisfies all security properties but also keeps the characters of the protocol existed.Finally,Our idea is extended to protect flexible itineraries too.关键词：mobile agents;Merkle trees;computational cost;flexible itineraries2|835|2更新时间：2025-07-16
- 摘要：A least-square parametric channel estimator (LSPCE) for broadband multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is proposed.The MSE bound on LSPCE is derived and the optimal pilot sequences are also given.In order to reduce the complexity,we present an iterative algorithm to extract the channel information from its noisy version accurately by utilizing the correlation of the taps of finite impulse response (FIR) filter channel model.Simulation results show that the proposed channel estimation gives much better performance than conventional LS algorithm and the detection performance is nearly optimal.关键词：multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM);channel estimation;sparse channel;delay estimation2|1964|9更新时间：2025-07-16
- 摘要：The generalized eigen-decomposition plays important roles in modern adaptive signal processing applications.In this paper,a novel unconstrained cost function for the generalized eigen-decomposition is presented and the properties of the cost function are analyzed.By applying recursive least-squares technique to minimize the cost function,an adaptive algorithm is proposed for finding the most dominant generalized eigenvector.The algorithm is also applied for the beamforming of the smart antenna in CDMA systems.The simulation results show the proposed algorithm has fast convergence and dynamic tracking capability.关键词：generalized eigenvector;adaptive algorithm;generalized eigen-decomposition;recursive least-squares;adaptive beamforming2|1020|0更新时间：2025-07-16
- 摘要：This paper proposes a bootstrap equalizer for MIMO channel time-variation suppression.The decorrelating equalization algorithm for MIMO communication system is proposed firstly,which realizes the decorrelation of the distinct source signals based on the statistics of source signals and therefore suppresses co-channel interference in MIMO system.Then this algorithm is introduced to the time-varying MIMO system and derives the bootstrap equalizer for MIMO channel time-variation suppression,which equalizes the time-varying MIMO channel only by its inputs,and greatly suppresses the time-variation-induced co-channel interferences in ordinary equalizer's output and improves the system BER performance at the cost of only a little additional computational complexity.Simulation results demonstrate that the proposed decorrelating MIMO bootstrap equalizer curbs the influence of the channel time-variation and effectively improves the BER performance of the receiver.关键词：bootstrap equalizer;decorrelating equalization algorithm;time-varying MIMO channel2|912|0更新时间：2025-07-16
- 摘要：By borrowing ideas from the plane transformation technique,the dense radar pulse stream is mapped into a 2-D plane matrix.And a new algorithm for fast searching the periodic and symmetric patterns is proposed and applied to deinterleave the complex radar pulses with pulse repetition interval (PRI) modulated by a periodic and symmetrical function in dense pulse environments.Extensive experimental results show that the averaged accurate rate of this algorithm for deinterleaving the complex radar pulses with a periodic and symmetrical PRI in dense environments is about 92% and averaged missing rate is merely 5%.At last,conclusions that the pattern searching time,the averaged accurate rate and missing rate of this algorithm vary as the density of radar pulse stream,are given in details and presented in figures.2|955|8更新时间：2025-07-16
- 摘要：Due to the presence of the "hidden terminal" and the "exposed terminal" problems,the applications for radio Ad hoc networks have greatly been restricted.Furthermore,with the characteristics of the underwater acoustic channel,such as low available bandwidth,highly varying multipath,and large propagation delays,the designing of underwater acoustic Ad hoc networks is a more challenging task.In this paper,we propose a new multiple access control (MAC) protocol for underwater acoustic Ad hoc networks,namely,the parallel transmission multiple access (PTMA) protocol.This protocol is based on the following ideas:to resolve collision,the reservation for multiple channels is made,thus data packets may parallelly be transimitted on multiple channels;to reduce the time for waiting for the clear-to-send (CTS) packets,we begin to transmit data packets as soon as the request-to-send (RTS) packets have been sent without the receipt of the CTS packets.Simulation results,which were obtained by using the OPNET Modeler/Radio,show that the proposed PTMA protocol can provide higher throughput performance and lower end-to-end propagation delay than those that are suitable for radio Ad hoc networks within the underwater acoustic environment.关键词：Ad Hoc networks;underwater acoustic channel;multiple access control;parallel transmission5|894|0更新时间：2025-07-16
- 摘要：Due to the network prolonging or fault,inconsistency or synchronous problem of the initial state of cooperative sites occurs when they join a real-time cooperative editing system at different time.Furthermore,the fault of cooperative sites or network,or long time no operations in cooperative sites,and the fault-tolerant of session manager can affect reliability of the system.A multiple late-join server algorithm is presented.The algorithm can effectively solve the consistency of the initial state of the late-join client.A query algorithm and distributed backup model based on session manager are proposed to guarantee the reliability of cooperative editing systems.The effectiveness of relative algorithms is verified by a concrete example.关键词：CSCW;cooperation editing system;late-join;session manager;distributed backup model2|770|0更新时间：2025-07-16
- 摘要：In order to remedy some of the disadvantages of trainable sequential maximum a posterior (TSMAP),we introduce an adaptive trainable sequential maximum a posterior (ATSMAP) approach for image segmentation based on multiscale Markov model.This method obtains the ground truth segmentations at all scales by wavelet decomposition of the accurate segmentation of the original image,and then estimates the parameters of multiscale quadtree models.Also,the parameters of the context model are estimated by a simple way that estimates the parameters with the low dimension feature instead of the context itself.Compared with TSMAP,the advantages of ATSMAP are as follows:1).The parameters of quadtree can be retrained for the specific image being segmented.2) The estimation of parameters for context models is very computationally efficient.The experimental results of the segmentation for bothsynthetic images and SAR images indicate that the approach fairly improves the segmentation accuracy over TSMAP and some other multiscale Markov based methods.2|1087|2更新时间：2025-07-16
- 摘要：Multiresolution signal and image models aim to capture the statistical structure of smooth and singular regions.Unfortunately,models based on orthogonal wavelet transform suffer from shift-variance,which makes them be less accurate and real-time.In this paper,we extend the local contextual hidden markov model(LCHMM)modeling framework to the complex wavelet transform and proposed a new model,called local contextual markov model based on complex wavelet(C-LCHMM),which features near shift-invariance and improved angular resolution and can exploit the local statistics of wavelet coefficients at a low computational complexity.关键词：complex wavelet;LCHMM;image denoising2|1185|10更新时间：2025-07-16
- 摘要：When Point Spread Function (PSF) is not known or only partially determined,restoration of the degraded images is called blind image restoration.MSE is used as criterion in the traditional blind image restoration methods,which considers little the influence of human vision psychology.But all images are eventually perceived and interpreted by the human visual system.So this paper proposes a new blind image restoration algorithm based on models of visual characteristic.An iterative scheme using alternating minimization is devised to recover the image and simultaneously identify the PSF.In the process of identification,total variation (TV) regularization method is used.Then in the process of restoration,Weberized TV restoration approaches is applied.The result of experiment shows that this restoration model produces better effect without known PSF.关键词：blind image restoration;visual characteristic;weber's law;TV regularization;alternating minimization(AM)2|1160|9更新时间：2025-07-16
- 摘要：Signal-to-Noise Ratio (SNR) requirement of Space Solar Telescope is 104.At the limits of CCD full well electron numbers,in order to improve SNR,the images collected by CCD must be accumulated in pre-processing unit;CCD image correcting technique was adopted to decrease CCD self-noise;In order to solve image drift,images correlative interpolation accumulation method was brought forward to further improve SNR and to meet design requirement.Pre-processing unit also undertakes tasks as following:Stokes parameter calculation during polarization measurement,CCD control,focusing control and image formatting.The requirements of pre-processing unit were analyzed,and system design solution was established.A ground functional prototype was completed according to above scheme with DSP and FPGA as the main chips,and system software was developed.The system function was simulated and testing under ground support equipment.关键词：Pre-processing;image integral;CCD image correcting;correlative interpolation accumulation;FPGA2|1132|3更新时间：2025-07-16
- 摘要：Zernike moments are widely used in the fields of pattern recognition and image analysis due to their good properties such as orthogonality and rotation invariance.Pseudo-Zernike moments have similar properties as those of Zernike moments;moreover,they are less sensitive to image noise than the conventional Zernike moments.However,the problem of fast computation of pseudo-Zernike moments has not been well solved due to the complexity of the pseudo-Zernile polynomials.In this paper,we present a novel method for fast computing the pseudo-Zernike moments.关键词：Zernike moments;pseudo-zernike moments;fast algorithm2|1292|9更新时间：2025-07-16
- 摘要：The chaotic circuit design is a prerequisite to chaotic communication,the chaotic encryption etc.Therefore the fundamental research and design of chaotic circuits are extremely significant.In this paper,a new method to design chaotic circuits is proposed,through which it becomes very simple and flexible to design chaotic dynamic systems in the 2D state space.The remarkable character of this design method is:we can choose complexity of the chaotic attractor as we need by combining the three kinds of modules,and the chaotic attractor can be easily implemented with a circuit or a integrate circuit.关键词：chaos;chaotic signals;symbolic dynamics;topological horseshoes;random signals4|1076|7更新时间：2025-07-16
- 摘要：When a monocomponent signal with slowly changing instantaneous frequency is burred by noise,its instantaneous frequency is usually added by many high crest and low trough.But real instantaneous frequency is a trend in estimated instantaneous frequency if signal to noise ratio is not very high.Though Maximum likelihood method can smooth some higher crest and lower trough,real instantaneous frequency is still not very obvious.A new non-parameter instantaneous frequency estimation method is established based on a new method:Local-wave method.Firstly,smoothed versions of the Phase Difference Estimator——Maximum likelihood method is adopted to estimate the instantaneous frequency.Then more accurate instantaneous frequency can be shifted as a trend by the local-wave method.A simulation is used to test this new method.The result shows the method described in the paper is proved to be more accurate and less computation.关键词：instantaneous frequency;maximum likelihood estimation;local-wave method2|774|2更新时间：2025-07-16
- 摘要：FOX are a family of block ciphers presented recently,which are based upon some results on proven security and have high performances on various platforms.In this paper,we construct some distinguishers between 3-round FOX and a random permutation of the blocks space.By using collision-searching techniques and integral attack,the distinguishers are used to attack on 4,5,6 and 7 rounds of FOX64.The four subkeys of 4-round FOX64 can be recovered with 29 chosen plaintexts and 245.4 encryptions.The five subkeys of 5-round FOX64 can be recovered with 29 chosen plaintexts and 2109.4 encryptions.The six subkeys of 6-round FOX64 can be recovered with 29 chosen plaintexts and 2173.4 encryptions.The seven subkeys of 7-round FOX64 can be recovered with 29 chosen plaintexts and 2237.4 encryptions.Therefore,4-round FOX64/64,5-round FOX64/128,6-round FOX64/192 and 7-round FOX64/256 are not immune to Collision-Integral attack.关键词：block cipher;attack;key;data complexity;time complexity2|1079|11更新时间：2025-07-16
- 摘要：A novel algorithm has been proposed for the European DVB-T 2K system so as to achieve frame synchronization before the timing synchronization and frequency synchronization and improve the performance of the system in the high-speed mobile multi-path fading channels. In the algorithm the combined correlation detection method has been employed,where the autocorrelation of the superimposed training sequence with the power of 1.41% of the total transmitter power and the cycle characteristic of the guard interval are employed to produce the synchronization signal. Computer simulation shows that the performance of frame synchronization is better than that of the conventional scheme in DVB-T systems with mobile speed from 150km/h to 450km/h. In additional,the superimposed PN sequence exerts little influence on the performance of the system.关键词：DVB-T systems;frame synchronization;training sequence;the combined correlation detection method2|676|2更新时间：2025-07-16
- 摘要：A new algorithm is proposed for direction of arrival (DOA) estimation of coherent sources in the presence of colored noise fields,which is called "Spatial Difference Smoothing (SDS)" method.By exploiting the property of Teoplitz decomposition of the autocovariance matrix,the SDS method resolves the correlated sources and incoherent sources separately.In this way the output data of the array are used repeatedly,and more sources can be estimated.The SDS method can fully eliminate spatially colored noise,and fit for more general unknown noise fields and low SNR environments.Compared with the conventional methods,the SDS can resolve more sources using the same number of sensors.In addition,the SDS method performs spatial smoothing iteratively utilizing smaller sensor arrays and has smaller computational complexity.Computer simulation results verify the correctness and effectiveness of the proposed SDS method.关键词：direction of arrival estimation;colored noise;coherent sources2|1194|12更新时间：2025-07-16
- 摘要：A novel design method of ac-coupled burst mode optical receiver (BMOR) is investigated for optical burst switching (OBS).The receiver has a simplest configuration of a PIN-TIA preamplifier,an ac-coupling capacitor,and a limiting amplifier.Both theoretical analysis and experimental results prove it to be a feasible method to reduce power penalty caused by the ac-coupling capacitor.Under the data rate of 1.25Gb/s,the BMOR can restore the burst within 300ns with high sensitivity.The design method breaks the limitation of ac-coupled BMOR in high speed applications.关键词：optical burst switching(OBS);AC-coupled;burst mode2|1136|0更新时间：2025-07-16
- 摘要：This paper is committed to compare the performances of three kinds of mobile code-based network management system.The quantitive models are presented to analyze the major factors that affect the response time and traffic,such as the number of managed elements,the bandwidth of network management station.These factors are evaluated with a variety of experiments.The simulation results shows that the mobile agent based network management approach can response more quickly and produce less traffic in large scale network and thus can be more scalable than other two mobile code based methods.关键词：distributed computation;network management;performance2|676|0更新时间：2025-07-16
- 摘要：This paper presents an analysis of the influence of pointing error on antenna array manifold and performance of interference localization based on a satellite multiple-beam antenna.A modified approach is also presented which can modify the results of interference localization by using MUSIC algrithm and come out with more robust results.Simulation results support the theoretical analysis.关键词：satellite multiple-beam antenna;interference localization;array manifold;antenna pointing error;DOA estimation12|968|1更新时间：2025-07-16
- 摘要：In multidimensional signal detection,there is often too much data to process.By using the concept of projection,the dimensionlity of data may be reduced,thereby simplifying the detection process.In this paper,a projection technique wherein the probabilistic weighted sum of a set of samples is chosen as the projected sample is presented in the case of only one sample in the set of samples projected onto a single sample may contain the signal.And the probability assignment formula of each sample being signal is derived.As verification,it is used in the fields of detection of dim moving point targets in IR image sequences,the performance analysis and experimental results are also given in this paper.Meanwhile,its performance is compared to the popular technique of maximum value projection wherein the maximum value of a set of samples is chosen as the projected sample.From the comparison,it is concluded that our algorithm is superior to the latter which is belong to the special case of ours and it has a higher detection performance even at low signal-to-noise ratios than the latter.关键词：probabilistic weighted summation projection;maximum value projection;dim point target;image sequences;Detect and estimation2|866|1更新时间：2025-07-16
- 摘要：In this paper,sea echo detection using the system of ionospheric backscatter sounding is described in detail.Sounding system-structure and the methods of signal processing to sea echo are proposed.The acquisitive results are analyzed in full.Comparison with the Barrick expression of Doppler shift shows that the proposed experiment results are proper and sea echo detection using the sounding system is feasible.关键词：the system of backscatter sounding;pulse compression;sea echo;spectrum analysis3|1238|19更新时间：2025-07-16
- 摘要：The particle swarm is an algorithm for finding optimal region of complex search spaces through the interaction of individuals in a population of particles.A new method based on particle swarm optimization(PSO) is proposed to design FIR digital filters.The design of FIR digital filters is converted into the optimization of the parameters of FIR digital filters.PSO is used to search the whole parameters space effectively and globally in order to optimize parameters.The effectiveness and superiority of the introduced method are demonstrated by experimental results on the low pass and band pass FIR digital filters.And compared with other optimization algorithms PSO has advances in computational power.关键词：particle swarm optimization;FIR digital filters;filter design2|2167|11更新时间：2025-07-16
- 摘要：Pulse-Coupled Neural Networks (PCNN) is very suitable for image segmentation.In condition of certain parameters,the result of segmentation will periodically change with the iteration times.Therefore,how to decided the best iteration times is the key of applying PCNN in image auto-segmentation.In this paper,an edge statistic algorithm based on calculation of connected region is provided.This algorithm calculates the valid edge of the segmentation result,and it means that the max is accordant with the best segmentation.It has been proved by experiments that the algorithm has much better sensitivity than those methods based on entropy of image or on edge operator,and also has stronger robustness of noise.2|1312|14更新时间：2025-07-16
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