最新刊期
卷 29 ， 期 4 ， 2001
- 摘要：The time-frequency analysis can transform the time domain signal into time-frequency domain,and reveal the law of frequency varying with time.In the time-frequency representation,there are many curves,Present methods can only detect line and only be applied on Wigner time-frequency distribution.In this paper we extend in two directions:firstly we extend to apply on arbitrary time-frequency distribution,secondly we extend to detect any kind of curves in time-frequency distribution.Numeric experimentation show that this method can detect curves more robustly for low SNR signals especially applied on adaptive time-frequency distribution.2|1153|2更新时间：2025-07-16
- 摘要：In accordance with the problem that the past fuzzy identifying method can not optimize the input-output space of fuzzy model,this paper proposes a fuzzy clustering method based on a new objective function.This method enables the input-output mapping space to approach the real output,thus optimizing the model structure.Simulation example demonstrates that this method can identify non-linear systems and significantly improve modeling accuracy.关键词：objective function;fuzzy clustering;fuzzy identification;non-linear systems2|850|6更新时间：2025-07-16
- 摘要：A fast algorithm is proposed for tracking low observable small targets in a digital image sequences.Wavelet transforms are used for image filterting to improve SNR.Tentative tracks are formed based on genetic algorithms which avoid target tracks missing.Coding and genetic operation are designed for this problem.Target trajectories are confirmed by truncated sequential probability ratio test.The simulation results show that it can efficiently detect and track small targets with size as small as 2×2 and SNR＜2.关键词：wavelet transforms;genetic algorithms;multistage hypothesis;sequential images;detecting and tracking dim small target2|2140|16更新时间：2025-07-16
- 摘要：This paper discusses feature fusion technique in underwater target recognition and proposes the method dealing with the problem encountered.Then,fuzzy fusion classifier (FFC) was designed based on this concept.FFC does not make any assumption about samples' distribution in pattern space,but emphasizes mutual restraints among classes and the independent role of each pattern and synthesizes those role by operation like combination in fuzzy logic.In practice,FFC can efficiently improve classification performance of recognition system by synthesizing features from multisensors.关键词：feature fusion;target recognition;underwater target;classifier2|1413|4更新时间：2025-07-16
- 摘要：Invisible image watermarking is an effective method to provide protection for copyright ownership of digital media.Most image watermarking algorithms use pseudo random sequences as watermarks and so they can only give the answer of "Yes" or "No".Embedding meaningful watermark is important in some applications but results in more difficulties.There are two problems in embedding meaningful watermark as follows:(1) the embedded watermark must have a certain bit rate.And (2) the embedded watermark must be detected correctly from possibly distorted watermarked image.In this paper,we apply the theory and methods in digital communication to watermark embedding and propose an invisible image watermarking algorithm in DCT domain for embedding meaningful watermarks.The algorithm reduces error probabilities of detection by exploiting BCH code and matched filtering.With the proposed algorithm,we embed a meaningful watermark composed of 32 characters into an image of 256×256 and the watermark thus generated is robust.The watermark can be detected with zero error probability even if the quality of watermarked image is as poor as 26 dB in PSNR after corrupted by additive Gaussian noise.关键词：invisible image watermarking;meaningful watermark;information hiding;matched filtering;BCH2|1450|10更新时间：2025-07-16
- 摘要：In this paper,we propose an efficient algorithm for compressing gray-level finger-print image.This algorithm is implemented by combining signal-noise characteristic of finger-print image with context-based prediction coding,the baseline algorithm for next generation of international standard on lossless image compression.There are mainly three distinguishing features in our proposed algorithm:local direction-based prediction,extended context for micro texture and histogram initialization based on imaging apparatus.Experiments with real finger print images and ISO standard images show that the compression ratio of our method is among the best in the literature.关键词：lossless image coding;signal-noise characteristic;finger-print image2|1335|0更新时间：2025-07-16
- 摘要：In this paper,a new speaker adaptation method—codebook-based speaker adaptation,which could combine the advantages of transform method with Bayes adaptive learning method appropriately,is presented.Not only can the speaker adaptation system improve its performance for small amount of adaptation data,but it can also approach asymptotically matched-condition performance with increasing number of adaptation data.The adaptation process can be divided into two stages.In the first stage,for approximating the acoustic parameters of a target speaker,the linear combination of lots of reference speaker's codebooks is proposed.An effective algorithm based on Rosen gradient projection method is developed to count the weight of each codebook in the linear combination.In the second stage,the combination of codebooks is used as the prior probability,then Bayes adaptive learning method is used to learn the exact value of the target speaker's codebook as more adaptation data are gathered.Thus incremental speaker adaptation can be achieved.As an illustration,this method is applied to a speaker independent continuous speech recognition system for the Chinese language.A series of comparative experiments were conducted to evaluate the performance of the proposed method.The results have shown it is quite promising.关键词：speech recognition;codebook-based speaker adaptation;Rosen gradient projection method2|1001|0更新时间：2025-07-16
- 摘要：Currently,Asymmetric Digital Subscriber Line (ADSL) is the most noticed technology in xDSL family.Using twisted-pair copper line as access medium is one advantage of ADSL because this medium has been widely distributed.Also,ADSL adopts point-to-point architecture,which brings more flexibility to set up networks.This paper is based on the development of ADSL system.It includes the architecture of ATM(Asynchronous transfer mode) over ADSL broadband access network.We concentrate our attention on hardware and software function designs of ATM over ADSL ATU-C and ATU-R cards.关键词：access network;ATM over ADSL;broadband network2|1080|1更新时间：2025-07-16
- 摘要：The paper mainly aims at the simulation methods for the performance of the future mobile communication system.The fundamental methods for structuring the wideband mobile communication system,as well as the key points of simulation——basic principles and methods of mathematical modeling,primary models of the simulation system are presented.Furthermore,the implementation of system level simulation in a particular environment is discussed,and some simulation results and the analyses are presented.关键词：mobile communication;system simulation;system modeling;simulation model2|1148|2更新时间：2025-07-16
- 摘要：Information transmission and detection with different rates are one of the main characteristics in the current and future digital communication systems.In IS-95 A CDMA system,the speech encoder has four different rates depending on the speech activities of the speaker.At the receiver,in order to reduce the complexity of the decoder and save the energy,it needs to detect which rate is used,so that it can select one matched decoder to deal with the transmitted signals.In [3],an effective multi-rate detection algorithm was presented recently.In this paper,a new multi-rate detection algorithm is proposed.Compared with that in [3],the proposed algorithm in this paper has comparable computation complexity and a considerable improvement on the total performance of the error rate detection probability under relatively low signal to noise ratios.关键词：multi-rate detection;IS-95;CDMA;signal to noise ratio2|759|0更新时间：2025-07-16
- 摘要：The constrained optimization models for integrated space-time interference suppression in CDMA systems are proposed in this paper.The models combine smart antenna and RAKE receiver together,and mitigate multiuser access interference (MAI) and interchip interference (ICI).The conditions of zero-forcing equalization are derived.Neural network implementation of the models is also studied.Finally,the performance of the suppressors is investigated.关键词：CDMA;interference suppression;smart antenna;RAKE reception;neural network2|1058|0更新时间：2025-07-16
- 摘要：It is well-known that the multi-value CDMA spreading codes can be designed by means of a pair of mirror multi-rate filter banks based on some optimizing criterion.This paper indicates that there exists a theoretical bound in the performance of its periodic correlation property,and gives the condition on which the bound is achieved.Based on this analysis,a criterion of maximizing entropy is proposed to design such codes.Computer simulation results show the performance superiority of the resulted codes.关键词：multirate unitary filter banks;periodic correlation property;CDMA spreading code;maximum entropy criteria2|821|0更新时间：2025-07-16
- 摘要：This paper proposes a congestion control algorithm FACC (Forward Active Networks Congestion Control) based on Active Networks.The comparison with traditional TCP(Transport control protocol) shows that by providing congestion detection and congestion control mechanism in network nodes,FACC greatly reduces the congestion reaction delay of source endpoint and consequently increases the average throughput of each endpoint.Computer simulations are given to analyze the performance of FACC algorithm under various circumstances and compare FACC with Tahoe,Reno,NewReno and SACK TCP protocols.The result of simulation shows that FACC can obviously increase the average throughput of each endpoint with or without the cross traffic in network,resulting in little additional computation delay of the network node.关键词：active networks;congestion control algorithm2|1094|4更新时间：2025-07-16
- 摘要：It is important for mobile assisted handoff(MAHO)to accurately measure channel quality and report it to the serving base station.The Euclidean distance(ED)metric,associated with the decoded information sequence,is used as a channel quality measure,Simulations show that the averaged ED metric is a reliable channel quality measure which remains consistent across different coded modulation schemes and at different mobile speeds;ED metric works well for MAHO,reducing unnecessary handoffs and handoff delay.关键词：handoff;channel quality estimation;euclidean distance2|866|0更新时间：2025-07-16
- 摘要：With the rapid growth and development of Internet,it will become the ultimate platform which provides all kinds of network services.Among these network services based on the Internet platform,there are not only best-effort services,but also quality-guaranteed services[1].In this article,we discuss the issues on how to support quality services of multicast communications on the network layer by way of QoS(Quality of Service) routing strategy.Currently,there have been many multicast QoS routing algorithms proposed in literature.All these algorithms achieved lots of exciting results in network resource utilization and throughput,but still have some problems to be improved.Based on these problems,we proposed our QoS routing algorithm,and the experiment shows that compared to the other proposed algorithms,our algorithm has many improvements on adaption to network topology,network size,symmetric and asymmetric link load.关键词：quality of service;multi-constraints metric;path selection;multicast routing2|982|3更新时间：2025-07-16
- 摘要：The unequal error protection of multilevel coded modulation based on capacity rule in Rayleigh fading channels is investigated.After the unequal error protection of multilevel coded modulation is discussed in detail,a non-uniform signal constellation applied to 8ASK modulation is designed.Both theoretical analysis and computer simulation show that non-uniform signal constellation can improve unequal error protection ability of multilevel coded modulation system.It improves transmission quality in Rayleigh fading environment and saves bandwidth at the same time.关键词：unequal error protection;multilevel coded modulation;capacity rule;Rayleigh fading channels2|824|0更新时间：2025-07-16
- 摘要：The effects of hidden terminals on the network's performance can be greatly reduced by using code division multiple access (CDMA) in multihop wireless networks.Code assignments are basic problems for using CDMA in the multihop wireless networks.The purposes of the code assignments are to improve the ratio of spatial reuse of spreading codes,to reduce the possibility of packet collisions and to response to the change of topology.In this paper,a new distributed algorithm is proposed to assign codes for dynamic,multihop wireless networks,and its correctness is proved.Its complexities are compared with those of other algorithms.Being different from the previous algorithms,which minimize the number of codes used,this algorithm is supposed that the number of spreading codes is enough.We seek for an algorithm,which is implemented easily, runs quickly,and reduces the cost of communication.关键词：multihop wireless network;assignment codes;algorithm2|749|0更新时间：2025-07-16
- 摘要：A new queueing model ∑ N i Gi/ ∑ N i Gi/1( ∑ N i Gi)/ ∑ N i Si(FCFS) is set up for the support of an asymmetric polling model with limited (k=1) service in discrete time,and with limited buffers in LAN(Local area network).According to the embedded Markov chain theory and the generating function,a mathematical analysis has been developed in this paper.The mean polling cycle,the mean values of queue length,the mean delay,and the packet loss rate of the polling system are explicitly obtained.The results of computer simulation are in concordance with the theoretical analysis.关键词：asymmetric cyclic polling;probability generating function;queue length;delay time;loss rate2|941|6更新时间：2025-07-16
- 摘要：Delay constrained multicast problem is an important part of multipoint routing optimization problem and has been proved to be a NP-Complete problem.The paper provides a heuristic genetic algorithm based on penalty function method to solve the problem,and discusses how to select the penalty function for infeasible solutions which violate the constraint.Dynamic cross probability and mute probability suiting for this kind of problems have been adopted to accelerate the convergence speed.And algorithm complexity is analyzed.Simulations show that the algorithm is effective and stable.关键词：delay constraint;multicast;genetic algorithm;accuracy penalty function;computation complexity2|1246|5更新时间：2025-07-16
- 摘要：In this paper,we study the NP-hard delay-constrained least-cost routing problem.We propose a new framework to solve the problem and provide simple and efficient source routing heuristics from the model,through which one can always find a delay-constrained path if such a path exists.Computation complexity of our heuristics is O(|V|2) and on-line complexity is O(|V|).Simulation results show that our heuristics achieve good cost performance.Finally,we extend the model to routing problem under multiple QoS constraints.关键词：delay-constrained;QoS-based routing;source routing2|939|2更新时间：2025-07-16
- 摘要：The adaptive chirplet decomposition,representation of Chirps by a class of chirplet,is an efficient approach in the time frequency structure analysis of chirp signals.Its key problem lies on the chirplet estimation,which greatly affects the decomposition results and hence is a major difficulty at present.In this paper,a simple numerical algorithm for estimating the chirplet with high accuracy is proposed,with which signal structure can be represented more clearly.Simulation results confirm the algorithm.关键词：signal decomposition;time-frequency;chirp;chirplet2|2232|17更新时间：2025-07-16
- 摘要：Considering the sparseness of Gabor coefficients of the underlying signals in joint time-frequency plane,this paper describes an adaptive signal recovery approach,obtained by shrinking the Gabor coefficients based on Bayes rule.Via the assumption of prior distributions of Gabor coefficients for the unknown signals and noises,we present a closed form expression for the posterior estimation of Gabor coefficients of the unknown signals,implementing time-variable filtering in time-frequency domain.The validity and effectiveness of the proposed scheme are demonstrated with numerical experiments.关键词：Gabor transform;Bayes estimation;signal recovery;nonparametric regression2|869|0更新时间：2025-07-16
- 摘要：The reported studies on EEG inverse by multiple signal classification (MUSIC) show the classical MUSIC algorithm suffers from two shortcomings:be sensitive to a color noise and fail in identifying synchronously active sources.Recent studies reveal that the MUSIC-based algorithm may be improved in depressing spatial coherent noise if the classical zero delay correlation matrix is replaced by a non-zero delay-correlation matrix,or by a high-order cumulant matrix,or by incorporating known noise covariance matrix in the zero-delay correlation matrix.And the MUSIC algorithm can be extended to identify synchronous actives through a recursive strategy.In this work,an iterative,multi-dimensional and delay-correlation MUSIC is proposed,where the color noise is depressed by the non-zero delay correlation and the synchronous active sources are identified by the iterative multi-dimensional MUSIC search.Simulation and VEP data tests show a good reconstruction is obtained.关键词：electroencephalography (EEG) inverse problem;MUSIC;color noise;coherent sources2|962|5更新时间：2025-07-16
- 摘要：Knowledge is ,no doubt,an important wealth to the mankind but there has not a knowledge theory existed yet till the present time.An attempt was made in[1]to establish 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.Here in the paper the nucleus of knowledge theory,the mechanism of knowledge creation and that of intelligence production,will be presented.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 faciliate the effective utilization of information and knowledge leading to better advancement of the research in the field of intelligent machines.关键词：information;knowledge;knowledge creation;intelligence production;a unified theory of information-knowledge-intelligence2|1502|6更新时间：2025-07-16
- 摘要：High frequency ground wave radar generally adopts linear frequency modulated continuous wave (LFMCW) signals as the transmitting signal and acquire demodulation by getting rid of the slope.Here a new receiver system compensation scheme is proposed according to the working principle of this kind of radar.The system compensation is divided into wide-band compensation and narrow-band compensation,which are accomplished in time domain and frequency domain respectively.Rigorous theoretical demonstration and computer simulation results are brought forth in this article for the new method of wide-band compensation in time domain.关键词：system compensation;wide-band compensation;narrow-band compensation2|1080|4更新时间：2025-07-16
- 摘要：The high frequency(HF) characteristics of the split cavity oscillator with three cavities are studied.Starting from homogeneous scalar Helmholtz's equations associated with Borgnis potential function in a cylindrical coordinate system,and based on the standing wave concept of slow-wave introduced in the paper,the analytic expressions of the dispersion relation and field distribution for azimuthally symmetric transverse magnetic modes in the split cavity oscillator with three cavities are derived,by using boundary conditions for Borgnis potential function in conjunction with field matching conditions at the common interface between the adjacent subregions.The resonance frequency of the split cavity oscillator with three cavities calculated by this analytic method is compared with that measured in experiments and it is found that they are in agreement quite well.关键词：split cavity oscillator;dispersion relation;field distribution;high frequency characteristics2|920|5更新时间：2025-07-16
- 摘要：This paper discusses the correlation immunity of multi-output Boolean functions,shows a property of multi-output correlation immune functions and presents a method for constructing multi-output correlation immune functions.关键词：multi-output Boolean function;correlation immune function;unbiased function2|867|1更新时间：2025-07-16
- 摘要：This paper reviewed the research progress of objective measures of speech quality.First,a survey of present major objective measures of speech quality was described.Secondly,the classification and performance of these objective measures were introduced.At the end,some viewpoints for development direction of objective measures of speech quality were discussed.关键词：speech quality;objective measures2|1857|19更新时间：2025-07-16
- 摘要：In this paper,we mainly discuss quesue scheduling algorithms in packet switching network.We firstly classify the recent scheduling algorithm,then analyze their performance objectives and technology attributes thoroughly.At last,we give out our related research works and discuss their future trends and present several topics remained to be studied.关键词：queue scheduling algorithm;switching node;generalized processor sharing;packet fair queuing;service curve;dynamic packet state2|3089|20更新时间：2025-07-16
- 摘要：Trapezoidal wave is a familiar wave in electronics.This paper considers its main properties,and by using biorthogonal function,a signal under certain conditions can be easily expanded as a trapezoidal wave series.It is used for the theory of signal analysis to research nonorthogonal function.2|1611|0更新时间：2025-07-16
- 摘要：Based on the calculations of capacities of equivalent channels[1],the perfomance of MLC(Multilevel coding)system with two decoding methods which are MSD(Multistage decoding)and PDL(Parallel decoding on levels)is compared in AWGN and Rayleigh fading channels.In which BCH codes are chosen as component codes,and three set partitioning strategies with 8ASK modulation are used.关键词：mobile fading channel;multilevel coding;multistage decoding;parallel decoding on levels2|826|0更新时间：2025-07-16
- 摘要：A forecasting method of time series called wavelet-domain predictor is proposed.Some non-stationary time series can be decomposed into several approximate stationary time series with wavelet decomposition.Decomposed time series are forecasted with auto-regression model,to obtain forecasting results of the original time series.Experiments with sunspot activity data show that the method is better than traditional forecasting approaches and neural network approaches,and can be applied to forecasting of some non-stationary time series effectively.关键词：wavelet analysis;time series;forecasting2|3467|33更新时间：2025-07-16
- 摘要：Proxy signature schemes allow a proxy signer to generate a proxy signature on behalf of an original signer.However,since in previous proxy signature schemes a proxy signature is created on behalf of only one original signer,we call these schemes proxy mono-signature schemes.This paper presents a new type of proxy signature schemes called proxy multi-signature schemes in which a proxy signer can generate a proxy signature on behalf of two of more original signers.关键词：digital signature;proxy signature;multi-signature2|1384|33更新时间：2025-07-16
- 摘要：Because the sample values often have an interval feature.So,in this paper,we improve the ART Neural Network to an Interval-valued ART Neural Network whose inputs of the first layer and weights between the first layer and output layer belong to the interval-valued fuzzy sets I .We proposed the Normative Method,Similar Degree Computing Method,Threshold Examining Method and Learning Rule of the Interval-Valued ART.At last,an example of transmission form choice in the mechanical design is given.This example proves that our Interval-valued ART is effective.关键词：an interval-valued ART neural network;normative method;similar degree computing method;threshold examining;learning rule2|907|0更新时间：2025-07-16
- 摘要：In order to effectively suppress the fast follower jammer from up-link in frequency-hopping satellite communication systems,a novel jamming suppression technique (AJDBFFH) of combining digital beamforming(DBF) with frequency-hopping(FH) is presented.The jamming suppression problem of signal correlation between the fast follower jammer and the desired signal is solved by using AJDBFFH technique.Computer simulation results show this technique against the fast follower jammer is very effective and the error bit rate performance is improved.关键词：satellite communications;digital beamforming;adaptive nulling antenna;jamming suppression2|1486|0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