最新刊期
卷 29 ， 期 1 ， 2001
-
Research on Explicit Window Indication Congestion Control Strategy in Satellite TCP/ATM Transmission
摘要：Satellite ATM is a hot topic on satellite communication field in recent years.TCP over satellite ATM is one of the most important research issues because the long propagation delay of satellite channel can reduce the efficiency of TCP congestion control.Since the congestion control of TCP is implemented by using window,we propose an explicit window indication strategy for TCP over UBR.The simulation results show that this method can enhance the link efficiency greatly and keep good fairness;at the same time it works well under VBR background traffic.It is easy to implement; the buffer size requirement of the gateway for zero cell loss is very small and independent of the numbers of TCP sources.关键词：satellite ATM;congestion control;explicit window indication2|895|0更新时间：2025-07-16 - 摘要：The key and crux to improve capacity of a cellular system is to abate the Co-Channel Interference (CCI) derived from frequency reuse.In this paper,a hybrid-excited power-delivery intelligent cell structure based on the idea of micro-cell zone is presented.With seven antennas,one at the center and six on the edge,a cell is divided into seven areas,each of which can locate and serve mobiles within its reach with signal as good as possible.All the seven areas share all the channels allocated to the cell.CCI is lessened conspicuously,and capacity increases.关键词：co-channel interference (CCI);micro-cell;power-delivery intelligent cell2|918|0更新时间：2025-07-16
-
Partially Coherent Multiuser Weight/Phase Optimal Joint Detection in Over-Saturated MA Communication
摘要：This paper explores the problem of partially coherent multi-user weight/phase optimal joint detection in over-saturated multiple access communication.Firstly,based on maximum a posteriori criterion,partially coherent multi-user weight/phase estimator is given via theoretical analysis.Then,we present the low complexity partially coherent multi-user weight/phase optimal joint detection algorithm which is applicable to linear modulation methods with two-dimensional constellation.Finally,we analyze the performance of the receiver and the phase estimated error via computer simulation and make comparison with coherent and non-coherent detection.Some useful conclusions are drawn.关键词：over-saturated multiple access communication(OSMA);partially coherent detection;phase offset.2|775|0更新时间：2025-07-16 - 摘要：This paper investigates bandwidth allocation algorithm suitable to the AAL2 packet voice multiplexer,which takes into consideration the features and quality of service of AAL2 packet voice.A conclusion is drawn that averge rate bandwidth allocation can meet the requirements of AAL2 packet voice multiplexer without bit dropping.If we reduce the ATM VC (Asynchronous transfer mode;Virtual Channel) bandwidth utilization (e.g.ρ=0.9),we can further improve voice quality.As far as AAL2 packet voice multiplexer with bit dropping is concerned,average rate bandwidth allocation can well meet the requirements of the quality of service of packet voice.Computer simulation results obtained are in good agreement with the conclusion.关键词：asynchronous transfer mode (ATM);ATM adaptation layer type 2;call admission control;packet voice;QoS2|867|0更新时间：2025-07-16
- 摘要：A multi-slot reservation multiple access protocol is proposed in this paper,which can integrate voice and data services efficiently.Under the condition of giving high priority to voice terminals,data terminals are allowed to reserve multiple information slots in consecutive time frames.The protocol is analyzed by embedded Markov process,from which some important performance measures such as voice packet loss rate,average channel access delay of data messages and system throughput are formulated.The research results indicate that,compared with IPRMA and NC-IPRMA,the protocol can support much higher equivalent data terminal rate,and within a large extent of traffic loads,the maximum system throughput can be reached.关键词：personal communications networks(PCN);multiple access protocol;performance analysis;time division multiple access(TDMA)2|738|0更新时间：2025-07-16
- 摘要：The paper considers a constant modulus cost function with non-canonical constraint,and presents a new blind multiuser detector.First,the capability of the detector to suppress multi-access interfrerence (MAI) is analyzed.The results show that the performance of the detector is not affected by the received power of the demodulated signal.Furthermore,we show that the constant modulus cost function with non-canonical constraint is strictly convex under some conditions.Using the stochastic method,a blind adaptive algorithm can be given,and its convergence is analyzed.The simulation examples demonstrate the results.关键词：CDMA(code division multiple access);MAI;constant modulus;blind multiuser detector2|804|1更新时间：2025-07-16
- 摘要：WDM Network will play important role in future backbone networks.It is necessary that WDM networks have the capability against component failure and support multi-priority.Two priority-based wavelength assignment methods,Wavelength Number Method and Assignment Quota Method,are proposed in this paper.We study network performance when these wavelength assignment methods are used for survivable WDM network in dynamic traffic pattern.Contents include influences on blocking probability from traffic load,total number of available wavelength channels per link,and the number of fibers per link.Simulation results are also given in the paper.2|1155|1更新时间：2025-07-16
- 摘要：A non-Euclidean metric which is "capacity Rule" and "mapping Rule" for the design of optimal MLC scheme over mobile fading channels is proposed.For AWGN channels,it is "capacity rule" and "UP rule".For Rayleigh fading channels,it is "capacity rule" and "BP rule".Directed by this theory,the performance of three levels multilevel coding with multistage decoding (MLC/MSD) scheme in AWGN and Rayleigh fading channels is simulated.In which BCH codes with different code lengths are chosen as component codes,and three mapping strategies with 8ASK modulation are used.关键词：mobile fading channel;multilevel coding;capacity rule;non-Euclidean metric2|1025|2更新时间：2025-07-16
- 摘要：M-QAM(Quadrature Amplitude Modulation) has a high frequency efficiency,but its quality will degrade largely under the multi-path environments,thus limits its application in wireless communications.This paper proposes a way to improve the performance of M-QAM in Rician fading,using maximum ratio and selective combining.It is expected that the method will gain wider use in reality.关键词：QAM;maximum ratio combining;selective combining;rician fading2|969|1更新时间：2025-07-16
- 摘要：The wavelength conversion experiment based on four-wave mixing in the semiconductor optical amplifiers with two orthogonal-polarized pumps is reported.The conversion efficiency and SNR are high and relatively flat over a large tunable range.关键词：semiconductor optical amplifier;four-wave-mixing;wavelength conversion2|1400|1更新时间：2025-07-16
- 摘要：In this paper a genetic algorithm (GA) based method for optical flow estimation of nonrigid object is presented.The nonrigid body is divided into several infinitesimal patches in which the pixels move together.The motion parameters of the patches are optimally estimated using GA method.The application of this method in motion estimation of biological tissues is also analyzed.The experimental results show that this method has the advantages of robustness,global optimality and high convergent speed and it is feasible for optical flow estimation of nonrigid body.关键词：motion estimation;nonrigid body;optical flow;genetic algorithm2|956|5更新时间：2025-07-16
- 摘要：This paper proposes a novel algorithm for segmentation of texture image based on variogram function.Texture feature obtained by the function can characterize randomicity and structure of texture.The variogram value and the variable distance calculated by the variogram function are used for the segmentation of texture image.This method is proved to be feasible and effective by experiments.关键词：variogram function;segmentation of image;texture feature2|1290|8更新时间：2025-07-16
- 摘要：A new method for designing optimal Gabor filters is proposed,which aims at segmenting bi-textured image with a single Gabor filter.It is known that the energy distribution of texture is centralized relatively in the frequency domain,but not focused on a single frequency component.Therefore,the optimal Gabor filter is designed by comparing the Fourier power spectrum density between two types of textures.Compared with other existing algorithms,the proposed algorithm requires less computational load and acquires better segmentation result.Moreover,a strategy to search the optimal filter with the help of the bandwidth parameter of Gabor filters is provided,which is matched with the perceptual property of human vision system and has great maneuverability.关键词：image segmentation;texture segmentation;Gabor filters;visual perceptual property2|1214|17更新时间：2025-07-16
- 摘要：In this paper,from the natural characters of step edge of image,we proposed a feature vector that consists of 3 components based on the information measure accordingly.Firstly.a BP neural network is trained with some samples that have been classified by manual work,and then extract edge proints in a new image using the trained neural network.Our method does not need any threshold and has better anti-noise performance since the influence of noise is adequately considered when the feature vector is settled.The effectiveness of this algorithm has been testified by some experiments in this paper.关键词：edge detection;step edge;neural network;information measure2|1282|14更新时间：2025-07-16
- 摘要：Legendre moment has been widely used in pattern recognition and image processing.It has the merits of orthogonality and minimal information redundancy.This paper presents a new way of linear registration using the Legendre moment.It has important value in the registration and fusion in multi-modality medical image,and in the radiotherapy treatment program system.2|1969|6更新时间：2025-07-16
- 摘要：The methods of calculating the DCT coefficients of the matching blocks from the derived DCT coefficients of the blocks in the reference frames under three different prediction modes of MPEG-2 is discussed,based on which a drift-free MPEG-2 transcoder that achieves motion compensation in the frequency domain is proposed.The rate-distortion optimization is applied to the rate control strategy to get the optimal quantization parameter of each frame,with its fast algorithm further simplified on the basis of G-BFOS method.Our approach can lead to the solutions of satisfactory accuracy but only with a fraction of the complexity of the existing algorithms.关键词：MPEG-2;transcoding;rate-distortion optimization2|875|1更新时间：2025-07-16
- 摘要：Magnetic source parameter estimation by MEG data is a basic question on MEG research.Optimization methods are available to the estimation.Gradient,Gauss-Newton and simulated annealing algorithms are used separately.Computer simulation demonstrates that these algorithms are all available under certain conditions.In comparison,gradient,Gauss-Newton algorithms are of fast computation speed while simulated annealing costs more time.On the other hand,simulated annealing almost has no special need for the selection of initial iterative values while gradient and Gauss-Newton algorithms have such need to some extent.Furthermore,on estimation of multiple source parameters,gradient,Gauss-Newton algorithms sometimes fail due to incorrect selection of initial iterative values,while simulated annealing algorithm is still effective.关键词：MEG;inverse problem;optimization;gradient algorithm;Gauss-Newton algorithm;simulated annealing algorithm2|850|2更新时间：2025-07-16
- 摘要：A new approach of adaptive Kalman filtering deconvolution (AKFD) is developed based on dyadic wavelet transforms.The technique discards the assumption of signals stationarity in predictive deconvolution,and overcomes the problem of improving resolution at the price of substantially decreasing signal-to-noise rate (SNR).The technique can well compress the reflection waveforms,but the noises are not lifted in substance.So it has a better ability of noise tolerance.Suppressing false reflections in dyadic wavelet transform domain is better than by applying AKFD in the time domain.In addition,since the technique also has the characteristic of adaptive Kalman filtering in every band for a signal respectively,it enhances the adaptation of Kalman filtering,and the resolution being obvious higher than that in the time domain.At the same time,the technique also overcomes the drawback of increasing the low-frequency component of AKFD in the time domain.A great deal of numerical models and real seismic data indicate that the technique has obvious effects.关键词：dyadic wavelet transform;adaptive Kalman filtering;deconvolution;nonstationary signal;signal-to-noise ratio;multiresolution analysis (MRA)3|1174|2更新时间：2025-07-16
- 摘要：Multiscale edges of a signal can be detected by using extrema or zero-crosings of dyadic wavelet transform.A reconstruction algorithm by cubic spline function interpolation,which is used to recover a signal from its dyadic wavelet transform extrema is proposed in this paper.Numerous experiments demonstrate its satisfying properties.Compared with previous algorithms it is simpler,more straightforward and faster.关键词：signal reconstruction;dyadic wavelet transform;extrema representation;spline function interpolation2|1068|3更新时间：2025-07-16
- 摘要：Based on the decomposition of the space-time eigenstructure of signals,a novel time-frequency signal subspace fitting (TF-SSF) method is proposed in this paper to estimate the DOA of signals.Through the bi-linear Cohen class time-frequency distribution,the time-frequency correlation matrix C x is constructed to replace the traditional correlation matrix R x. Accordingly the signal subspace and noise subspace are separated with the eigen-decomposition of C x. Because the observed data are processed in spatial domain and 2-D time-frequency domain simultaneously,the method can separate the signals that have different time-frequency signatures and is suitable for both stationary and nonstationary signals,while the traditional subspace methods have to assume that the signal is stationary.It is also proven herein that the traditional subspace methods is the special case of the TF-SSF method.Furthermore,with the time-varying filtering available,the method has the signal-selectivity and is capable of suppressing interference and noise that are difficult to handle in time or frequency domain only.The simulation results show the effectiveness of the method.关键词：array processing;joint time-frequency analysis;DOA(Direction-of-Arrival);nonstationary signals2|1073|4更新时间：2025-07-16
- 摘要：For the nonstationary property of the mixed process,Fourier series polyspectra and scaled polyperiodograms are introduced.We propose a new method to estimate frequencies of quadratic coupled harmonics in multilicative noise with zero mean and ones of cubic coupled harmonics in multiplicative noise with non-zero mean.Cupled frequencies can be obtained only by single record data and additive stationary noise is restrained without assumption of noise color and distribution.Finally, the simulation results are given.关键词：multiplicative noise;frequency estimation of coupled harmomics;fourier series ployspectra;scaled ployperiodograms2|1005|1更新时间：2025-07-16
- 摘要：Class one and class two super-Gaussian spectrum functions are defined firstly in frequency domain,and then their explicit analytic expressions in time domain are deduced.Time operator and frequency operator are introduced to analyse the time,frequency and time-frequency localization characteristics of the aforementioned two new class of functions.Theoretical analysis and results of numerical simulations show that:i)Time operator and frequency operator are very useful mathematical tool for time-frequency analysis;ii)The basic properties of super-Gaussian spectrum functions are useful in constructing orthonormal and almost orthonormal scaling functions and wavelets;iii)The bandwidth of super-Gaussian spectrum functions is decided mainly by their shape factor;the time width of super-Gaussian spectrum functions is controlled chiefly their order;time-frequency localization characteristics of super-Gaussian spectrum functions depend only on their order.关键词：super-Gaussian spectrum function;construction of wavelet;time operator and frequency operator;time-frequency localization;Gamma function2|1278|6更新时间：2025-07-16
- 摘要：A method for designing M-band cosine-modulated filter banks with near perfect reconstruction is proposed.The prototype filter is formulated as the form A(zL)B(z) and indirectly designed by varying the passband edge of A(z) with low order.In the course of the optimization procedure,the popular Parks-McClellan algorithm is used to design A(z).A design example is presented to show that cosine-modulated filter banks with high stop attenuation can be achieved using the proposed method.关键词：cosine-modulated filter banks;near perfect reconstruction;high stopband attenuation;multirate2|1206|3更新时间：2025-07-16
- 摘要：A new block design(differences set pairs) is defined.The properties of differences set pairs are studied. The relationship between differences set pairs and perfect binary array pairs is given.Theoretical basis for using differences set pairs to research perfect binary array pairs is provided.关键词：Signal design;block design;differences set pairs;perfect binary arrays pairs2|1074|28更新时间：2025-07-16
- 摘要：SERPENT and SAFER are AES candidates,which are analyzed by power attack in this paper.It is shown that power attack needs 2159、2119 and 279 trials for 256、192 and 128 bits key- SERPENT respectively.Although the number of trials is too big to realize,it reduces greatly the size of key.SERPENT have many weak keys for power attack.By analyzing and computing,it is received that SAFER is broken to power attack.Finally,some suggestions and two improving key scheduling of SERPENT are given.3|1053|1更新时间：2025-07-16
- 摘要：The robust spatio-temporal signal parameter estimation is studied in this paper in the case of general array errors.First a general array error model is given.Then a spatio-temporal weighted subspace fitting (ST-WSF) method is proposed on the basis of the given model.And the Cramér-Rao lower bounds on signal parameters,i.e.directions of arrival and carrier frequencies are derived.Numerical experiments further verifies the effectiveness of the algorithm.关键词：array signal processing;spatio-temporal spectral analysis;parameter estimation4|1001|1更新时间：2025-07-16
- 摘要：Knowledge has been very important wealth to the mankind but there has not a Knowledge Theory existed yet till the present time.An attempt is thus made in the paper to present a foundation of Knowledge Theory that includes a series of basic issues such as the related concepts and definitions,the methods of representation,the measurements,the reasoning and decision rules.It is believed that the establishment of the Knowledge Theory will lay a solid foundation to the unified theory of information,knowledge,and intelligence and that will greatly facilitate the effective utilization of information and knowledge leading to the growth of the research in the field of intelligent machines.2|1675|4更新时间：2025-07-16
- 摘要：Starting from the universal approximation theorem of multilayered feed forward neural networks,this paper proves that the finite time trajectory of nonlinear continuous-time system with input can be approximated by the state vector of the output units of a class of recurrent neural networks.关键词：nonlinear continuous-time system;recurrent neural networks;approximation2|1195|2更新时间：2025-07-16
- 摘要：Pareto multiobjective genetic algorithm is one kind of vector optimization methods derived from concept of Pareto optimal,and the whole Pareto optimal set can be got using this method.Because conventional Pareto GA runs with two chromosomes crossover,it consumes much time on Niche which makes the efficency of this algorithm somewhat low.In this paper,a new Pareto multiobjective GA with multiple-chromosomes crossover is presented,and the individual is expressed with real-valued representations which makes it much faster than conventional algorithms.Based on the proof of corresponding schema theorem,variance and entropy are proposed as measurements of diversity of population in genetic algorithms.The influence that the Pareto MOGA with multiple-chromosomes crossover acts upon variance and entropy is analyzed.At last,one example is presented to compare between method in this paper and traditional methods so as to prove the superiority of this method.关键词：genetic algorithm;multiple-chromosomes crossover;schema theorem;multiobjective optimization2|1922|19更新时间：2025-07-16
- 摘要：Two representatives are discussed primarily of decoding algorithms of algebraic-geometric codes.Two different approaches to decoding algorithms of algebraic-geometric codes are presented here evolving from decoding algorithms of Reed-Solomon codes and Goppa codes.关键词：algebraic-geometric code;decoding;algorithm;majority voting4|2156|1更新时间：2025-07-16
- 摘要：In FC'98,Frankin and Tsudik Proposed two protocols for n-party multi-unit fair exchange.In this paper,an attack on its protocol SUCCX-1 is presented,and in the meanwhile,an improved protocol is given.关键词：electronic commerce;fair exchange;protocol;attack2|838|1更新时间：2025-07-16
- 摘要：This article discusses the software radio structure of direct sequence spread spectrum system and its performance.At first,we prove the feasibility and necessity of software radio realization in DS system.Secondly our work includes the realized shape of software radio structure both in sending and receiving end,acquisition and tracking of direct spread spectrum sequence and software radio implement of CDMA in DS spectrum system.The result of computer simulation proves the feasibility of our method.关键词：software radio;direct sequence spread spectrum system;CDMA2|1487|6更新时间：2025-07-16
- 摘要：The stability property of LMS algorithm (least mean square algorithm) and the design of robust LMS algorithm are discussed in this paper.The standard LMS algorithm is transferred into a standard state equation form of discrete-time system.Then its quadratic stability property is analyzed by linear matrix inequality technique.Owning to the noise often emerging in input and measure of filter,a robust LMS algorithm,in which convergence,robust stability and robust property are all considered,is developed.In the end,simulation results are presented to support the analysis and to compare the performance of the robust algorithm with the usual LMS algorithm.They show that the algorithm is feasible.关键词：LMS algorithm;quadratic stability;robust filtering2|1328|1更新时间：2025-07-16
- 摘要：Based on Simulated Annealing Algorithm,a Simulated Annealing Linked Split Vector Quantizer (SA-LSVQ) optimized globally is proposed in this paper.Experimental results show that the performance of LSVQ is improved effectively in comparison with LBG method.关键词：speech coding;vector quantization;line spectrum frequency;simulated annealing2|1164|0更新时间：2025-07-16
- 摘要：This paper constructs a class of 9-7-tap wavelets filters,in which the famous 9-7-tap wavelet (CDF97) of Cohen and Daubechies is contained.New wavelets filters obtained from the class not only have excellent compression performances but also easy computation and are very suitable for design of ASIC.The test results for compression performances have shown that new filters are good almost as CDF97 under PSNR and can save more details.Therefore,the filters constructed in this paper are ideal replacement of CDF97 in standardized image compression systems based on wavelets.关键词：hyper wavelets;filters;circular matrix;image compression4|1129|8更新时间：2025-07-16
- 摘要：In this paper,we mainly discuss error problem which was brought about by fast speed realization of recursively computing DFTs.For example,we discuss the effect of coefficient error on the error of recursively computing and frequency output of the whole system.And we prove that the error of fast speed recursively computing of N length DFTs has order of O( N δ).关键词：recursively computing DFTs;fast speed realization;error analysis;high-precision realization2|1036|0更新时间：2025-07-16
- 摘要：In this paper we propose a novel kind of phase spreading sequence (PSS) for direct sequence spread spectrum multiple access (DS/SSMA) with continuous phase modulation (CPM),and the optimal design criterion of PSS is obtained.Several sets with PSSs of various periodic lengths under the condition of continuous phase frequency shift keying (CPFSK) of modulation index h=0.5 are constructed by exhaustive search based on this optimal criterion.The performances of PSS DS/SSMA system in Rayleigh fading channel are in-vestigated by theoretical analysis and numerical simulations.Finally,the comparisons between the performances of the systems with PSSs and the traditional PN sequence under the same conditions are also made.关键词：phase spreading sequence;DS/SSMA;CPM;rayleigh fading channel4|862|0更新时间：2025-07-16
- 摘要：In this paper,we present a multi-surfaces rendering method based on volume rendering for 3D data sets.First,we extract the boundaries between two different materials by weighting with gray-level gradient,and only voxels on these boundaries participate in the generation of each image,so it drastically reduces the rendering time.Second.We think the voxels on boundaries as the mixture of different materials,so in every voxel there is a surface.We use the oriented cube-interpolation technique to get the intersection point of viewing orientation and the surface in the voxel,then compute the surface normal of the intersection point.We use the normal to shade the voxel in order to improve the image quality.and make some experiments with medical CT images.关键词：volume rendering;3D data sets;surface rendering;normal;projection2|935|3更新时间：2025-07-16
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0