最新刊期
卷 31 ， 期 7 ， 2003
- 摘要：This paper analyses and modifies some problems in original definition and algorithm of Frequency Hopping Processing Gain,and some concepts are clarified.It is favourable to expanding the applicable field,defining the technical indexes and checking the designed equipments.Based on which,the relationship between Frequency Hopping Processing Gain and the anti-jamming ability of the system is further discussed.And a concept of the threshold for anti-obstruct-jamming in common frequency hopping system is put forward yet.关键词：frequency hopping;spread spectrum;anti-jamming communication2|1615|1更新时间：2025-07-16
- 摘要：In this paper,a new particle filter based on sequential importance sampling (SIS) is proposed for the on-line estimation problem of non-Gauss nonlinear systems.In the new algorithm,a bank of Gauss-Hermite filter (GHF) is used for generating the importance density function.The density function integrates the new observations into system state transition density,so it can match the statea posteriori density well.As a result,while the likelihood function is situated on the tail of state transition density or observation model has higher precise,the theoretical analysis and experimental results show that the new particle filter outperforms obviously the standard particle filter and the other filters such as the extended Kalman filter (EKF),the GHF.关键词：state estimation;particle filter;Gauss-Hermite filter;sequential importance sampling;importance density function2|2524|53更新时间：2025-07-16
- 摘要：Generally,some methods of blind signal processing ignore noise,however,noise affects the performance of algorithms,especially seriously in some areas.This paper provides solutions to the problem that mixing matrix is estimated blindly in Gaussian noise with unknown covariance.Based on Maximum Likelihood estimation,the equations are given for solving the mixing matrix and covariance matrix.Gaussian Mixture Model (GMM) is used to approximate the pdf of sources and results in a practical EM algorithm.Computer simulation shows that this algorithm is convergent and has good performance in low SNR.关键词：Gaussian noise;blind signal processing;EM algorithm;Gaussian mixture model2|1122|1更新时间：2025-07-16
- 摘要：Security policies are the key to the security of information systems.It is the precondition for the security of information systems to assure the completeness,correctness and consistency of security policies.The complexity of security policies is closely related to the degree of complexity of a system itself.Security policies must be enforced effectively.The following is studied in this paper:the enforcement of policies,the requirement for policies,and the consistency of policies.Especially a theorem is given for the consistency of access control policies and a method used to check the consistency is presented.关键词：security policy;policy enforcing mechanism;consistency;granularity2|925|3更新时间：2025-07-16
- 摘要：An algorithm STF-PDA has been presented based on the strong tracking filter with dynamically modifying structure of model.The performance of probability data association (PDA) can be improved by this algorithm.The theoretic analysis shows the algorithm is superior to the PDA with Kalman or extented Kalman filter.Compared with the latter one on simulations the simulations show that this new algorithm is more effective.关键词：target tracking;strong tracking filter;probability data association2|2447|3更新时间：2025-07-16
- 摘要：In order to detect the subpixel-,point- and a few pixel targets from low SNR image sequence,this paper presents a new approach which can greatly suppress UCN-sequence through adaptive threshold detection in single frame and high order cross-correlation with multiple frames.The number of candidate target trajectories and the quantity of data processing are greatly compressed by using the approach,and the approach is compatible with infrared- and television image sequences.The theoretical analyses of various kinds of operations are expounded in the paper.The experimental results have proved the correctness of theoretical analyses and the feasibility of the optimal algorithms.For the image sequences with SNR 1.5~0.5,after adaptive threshold detection in single frame and twice high order cross-correlation,the nonzero points left are only 0.03~14.59%,and the noise rejection rate is 99.97~85.41%.关键词：image sequence;adaptive threshold detecting;high order cross-correlation;target trajectories;data processing2|776|3更新时间：2025-07-16
- 摘要：To improve system capacity is always a hotspot in mobile communication systems.Therefore,space-time code techniques have been widely studied in wireless communications,for they provide better signal qualities in fading channel environments and increase system capacity.As an important space-time code,Vertical Bell lab Layered Space-Time (V-BLAST) code has been paid much attention in recent years.However,traditional detection algorithm of V-BLAST needs much time in performing linear nulling and successive symbol cancelling.The more the number of transmit antennas are,the more the process time delay is.Aiming in solving this problem,a new scheme based on linear nulling and parallel symbol cancellation is proposed in this paper.The new scheme is of less time delay and simpler detection structure.And the simulation results of new scheme are obtained by COSSAP simulation in flat Rayleigh channels.These simulation results are presented to verify the BER performance of new scheme based on parallel symbol cancellation.关键词：MIMO;space-time code;layered space-time code;BLAST2|879|3更新时间：2025-07-16
- 摘要：In this paper,a model based on the Markov's chain is given for the wide-interval frequency-hopped sequence of q-states (q-WDFHS).Based on the model,the probability distribution of the q-WDFHS can be written out through its 1-step and n-step transition probability matrices P and P(n).By deriving the analytical expression of p(n)ij and P(n),this paper provides the spectral characteristics of a q-WDFHS.Through the calculation of the spectrum distribution,this paper shows that the spectrum of a q-WDFHS with smaller interval is flatter and more concentrated on the domain of low frequencies,while those with larger intervals have more components of high frequency and sharper spectrum distribution.关键词：wide-interval frequency-hopped pattern;Markov's chain;stochastic test;spectral analysis2|744|0更新时间：2025-07-16
- 摘要：A new channel assignment (CA) model named optimum channel assignment (OCA) model is presented.First,the difference equations for the general CA problem is established from the features of channel assignment practice,then the OCA model is formulated and its solution is derived by using the Pontryagin minimum principle,these analytically derived results are then further validated by our computer simulations.The new model provides a fast,efficient CA algorithm,and remedies the current shortage of the overall performance evaluation for channel assignment schemes.关键词：cellular mobile communications;channel assignment;optimization2|927|2更新时间：2025-07-16
- 摘要：A new integrated routing algorithm for optical transport system has been designed.Based on the idea of segmentation in transport network,a multi-objective optimum model is established in each management domain and simplified to a double-objective model.By ameliorating and extending the double-direction scanning algorithm,we can get two solution sets,one of which consists of k shortest routes and the other comprises k routes with the least relay points.Then the results above are integrated by AHP or double-order method.关键词：optical transport system;network management;routing algorithm;multi-objective optimum model2|923|2更新时间：2025-07-16
- 摘要：Using a binary-mapped constant weight modulation code (BCWMC) for the recording channel of a digital holographic data storage system can facilitate the decision on the detected signal.The authors propose a new modulation coding scheme,6:8 Gray-mapped constant weight modulation code (GCWMC),in which each digital data having length 6 is viewed as a Gray codeword and the constant weight code is designed with a characteristic of binary 2-unit distance.Thus the 6:8 GCWMC scheme can possess the ability of its all the 8-bit codewords to bear some error when a two-digit swapping event occurres in an estimated codeword.Simulation results show that the 6:8 GCWMC scheme can outperform the 6:8 BCWMC one in the bit-error rate (BER) performance at low signal-noise ratio (SNR) for the system.关键词：holographic storage;Gray code;constant weight code;modulation code2|842|0更新时间：2025-07-16
- 摘要：Closed-form solutions for the correlated Rayleigh fading channel capacity under maximum ratio combining(MRC)or selection combining(SC)diversity reception are obtained in this paper.A comparison between the correlated Rayleigh fading channel capacity and independent Rayleigh fading channel capacity is presented.The performance of constant-power adaptive M-ary quadrature amplitude modulation (M-QAM) schemes over correlated Rayleigh channels under MRC or SC diversity reception is investigated.Closed-form expressions for spectral efficiency assuming perfect channel estimation and negligible time delay are derived.关键词：correlated rayleigh fading channel;channel capacity;diversity reception;maximal ratio combining (MRC);selection combing (SC)2|1129|2更新时间：2025-07-16
- 摘要：In this paper,we present a performance analysis based on an analytical model on CDMA reverse link with MRC(maximum ratio combining)-based macrodiversity and derive the exact outage probability expression.Both fast fading and log-normal shadowing fading are considered.The numerical results show that with MRC-based macrodiversity the reverse-link capacity can be increased greatly and the best performance can be achieved on the cell boundary.关键词：MRC;macrodiversity;reverse-link capacity;CDMA2|786|0更新时间：2025-07-16
- 摘要：For the problem of huge computing burden in the realization of space-time processing,the relationship of computing burden and system performance is analyzed.A new parallel method based on independent elements processing in the antenna array is proposed.Computer simulations show that,with a remarkable decrease of computing burden,the precision of the estimated vector channel impulse response is enough for the extract of the channel parameters,and the SINR of the array output can be increased observably.关键词：sace-time processing;parallel processing;CDMA2|833|0更新时间：2025-07-16
- 摘要：Fingerprint matching algorithm is studied in this paper.A fast point pattern matching algorithm based on core and delta information obtained from fingerprint classification is achieved.It successfully and rapidly solve the problem of image rotation,translation and transformation in fingerprint matching.Core points of inquery image and model image are used as a pair of reference points,and the parameter of rotation and translation are computed.The inquery image is rotated and translated against the model image,then these two images are matched based on point pattern.关键词：core;delta;point pattern matching;inquery image;model image2|1964|7更新时间：2025-07-16
- 摘要：In pattern recognition or classification,extracting effective classification features from original pattern signals is very important.But,for a great number of non-stationary or time-varying signals,such as speech,radar,earthquake signals,etc.,classification features are often localized both in time and frequency,so thus extracting effective features from them by general transformation methods is very difficult.Wavelet packet transform can provides an arbitrary time-frequency decomposition for the signals,because a wavelet packet library contains many wavelet packet bases,which can handle the different components of a signal.Therefore,by selecting a suitable basis,the effective features can be extracted.This paper is mainly concerned with extracting effective features from the recognized or classified signals by selecting wavelet packet basis via given training sample sets.Three separability criteria,i.e.,distance criterion,divergence criterion and entropy criterion,are used for selecting the best basis.The performance of features extraction by wavelet packet transform is compared with that by wavelet transform through experiments.关键词：wavelet packet;feature extraction;wavelet transform;pattern recognition;classification2|2934|22更新时间：2025-07-16
- 摘要：This paper applies chaos and fractal theories to the analysis of mulitpath fading in mobile radio communications for the first time,and investigates its nonlinear dynamical system characteristics based on the measured data from field trials.By reconstructing the status space and correlation dimension,we show that the dynamical system of the multipath fading channels has finite degree of freedom and a positive maximum Lyapunov exponent.The chaotic characteristic of the multipath fading is demonstrated and the nonlinear evolution mechanism is observed.Finally,we apply fractal model to the interpolation of multipath signals,yielding reasonably accurate replications.The results indicate that the nonlinear dynamical system could be a more suitable model than the conventional random process for describing multipath fading phenomenon.关键词：multipath fading;chaos;fractal;nonlinear dynamical systems;fractal interpolation2|1008|2更新时间：2025-07-16
- 摘要：The strong-password based authentication mechanism is an important development direction of authentication.In this paper we examine OSPA(Optimal Strong-Password Authentication),a recent solution to authentication,and attack it using composite attack which is put forward firstly.The results of attacks demonstrate OSPA is vulnerable to stolen-verifier, man-in-middle, replay and denial of service attacks.关键词：authentication;strong-password authentication;composite attack2|1052|6更新时间：2025-07-16
- 摘要：The efficiency of re-keying is a main factor that influences the performance of secure multicast.Grouping keys into logical tree and periodic batch re-keying for users join/leave are effective ways to improve the efficiency of re-keying and reduce the burden that re-keying puts on key management as well as users.In this paper,we present a re-key algorithm which reduces the burden that re-keying put on key management system and users.We then investigate the performance of batch re-keying using our algorithm.关键词：multicast;key distribution;key tree;Exponential distribution2|1028|8更新时间：2025-07-16
- 摘要：In this article,the definitions of grey degree and measurement for grey conception were presented.Furthermore,the calculation of grey conception was defined,some attributes of which were proven.关键词：grey conception;grey degree;grey measurement;grey calculation2|690|0更新时间：2025-07-16
- 摘要：In this paper,a rapid acquisition scheme of Doppler shift is proposed for a LEO satellite spread-spectrum communications system.Based on the use of digital matched filter(DMF)and automatic frequency control(AFC)loop,two characteristics of the DMF are exploited to reduce the mean acquisition time (MAT)of Doppler shift,namely,the rapid acquisition property of PN code and a high sensitivity of maximum correlation value to frequency offset.An expression of the MAT is derived,and a suboptimal decision of acquisition is given out from numerical results.Finally,the performance of the proposed acquisition scheme is compared with the traditional serial scheme,showing a significant improvement achieved.关键词：satellite communications;digital matched filter;automatic frequency control loop;Doppler shift acquisition2|2958|9更新时间：2025-07-16
- 摘要：As an effective method for multimedia authentication and tamper detection,fragile watermarking is drawing extensive attention recently.In this paper,we propose a novel fragile watermarking scheme based on HVS in DWT domain.By use of a specifical modulation,we embed the mark into the DWT coefficients of the original image.The features of proposed algorithm are as follows: i)The algorithm constructs a pyramid structure of the watermark for multi-resolution tamper detection; ii)According to the visual model,the algorithm modifies the coefficients to reduce the perceptible distortion; iii)The algorithm presents a new scheme for tamper detection by using image fusion.We propose several rules to distinguish the type of tamper between mild distortion and severe distortion.The experimental results demonstrate that the watermarks generated with the proposed algorithm can give the precise result of tamper detection when the image has been suffered from malicious tamper while tolerating JPEG lossy compression to a certain extent.关键词：fragile watermarking;information hiding;watermark pyramid;image fusion;tamper detection2|1114|1更新时间：2025-07-16
- 摘要：The FDTD method has found its wide applications in various microwave engineering problems.Limited by computation resources,however,the method can't be directly employed in analyzing complicated systems.A scheme combining the FDTD method with the generalized network connection theory is presented to overcome this drawback.First,the basic units of a complicated network are simulated with the FDTD method,then the characteristic of the complicated system is analyzed with the generalized network connection theory.The power division network of slot antenna array is a typical complicated microwave system.The property of a power division network with five ports is analyzed in the paper.Numerical results obtained show the effectiveness of the scheme.关键词：FDTD;generalized network connection theory;power division network2|759|0更新时间：2025-07-16
- 摘要：Sequences of degree distribution for low-density erasure codes are investigated.We propose a necessary and sufficient condition for sequences of degree distribution for low-density erasure codes to be capacity-achieving sequences.The properties of the Heavy-Tail/Poisson sequences and right-regular sequences are given for low-density erasure codes.The analytical property of capacity-achieving sequences is shown for low-density erasure codes.These analytical properties of the sequences of degree distribution will be helpful in designing capacity-achieving sequences of degree distribution for low-density erasure codes.关键词：low-density erasure code;erasure channel;capacity-achieving sequence;uniform convergence2|663|0更新时间：2025-07-16
- 摘要：Band-Limited channels have very bad effects on modulation classification of digital modulated signals.qLLR based modulation classifier is valid for classification of BPSK/QPSK signals in ISI Channel.GLRT based classifier makes use of Viterbi algorithm in maximum likelihood estimation of modulation symbol sequences,and PSP in estimating the effects of ISI on the sequence.Simulations show that they can achieve a very good classification performance in ISI channels.2|1102|2更新时间：2025-07-16
- 摘要：In this paper,a new DCT computation algorithm is presented,which is based on existing fast DCT algorithm and has fully utilized the parallelism of very long instruction word (VLIW) architecture to achieve high speed performance.Simulation results show that this method can reduce more than 73% and 24% computing cycles,compared with normal and fast DCT computation algorithm respectively.关键词：discrete cosine transform;very long instruction word;parallel algorithm2|1225|5更新时间：2025-07-16
- 摘要：Anonymous off-line e-cash protects the customer's privacy as physical cash does.But it is impossible for a judge to investigate crimes such as blackmailing and money laundering.Fair off-line e-cash extends it by assigning trustees the abilities for identities revoking and coin tracing.A fair off-line e-cash scheme is proposed,in which both electronic coin's unforgeability and legitimate users' anonymity are provable.关键词：e-cash;owner tracing;coin tracing2|992|0更新时间：2025-07-16
- 摘要：The growing demand for wireless services has created the need for improving the spectral efficiency of wireless communications over fading channels.M-ary multilevel quadrature amplitude modulation(MQAM) in conjunction with transmit antenna selection combined with receive maximum-ratio combining is investigated in this paper.Based on alternative representations of Q(x),the average symbol error rate of this combined spatial diversity scheme over flat Rayleigh fading channels is derived,and the effects of the time-varying nature of the wireless channels on its performance are analyzed.Numerical results show that the scheme can achieve significant diversity gain over traditional receive diversity schemes by distributing the antennas over transmit and receive side.关键词：quadrature amplitude modulation;Rayleigh-fading channel;maximum-ratio combing;selection combing;antenna diversity2|988|3更新时间：2025-07-16
- 摘要：Image reconstruction in electrical impedance tomography (EIT) is a highly ill-posed,non-linear inverse problem.Especially in static EIT,the modified Newton-Raphson (MNR) reconstruction algorithm with regularization technique based on minimizing the object function is usually not stable,even divergent,due to the serious image reconstruction model error and measurement noise.A new static image reconstruction method for EIT based on genetic algorithm (GA-EIT) is proposed in this paper,in which the global optimized solution for EIT problem will be converged by evolution without need of regularization.The experimental results also indicate that the performance (including the precision and space resolution in reconstructing the static EIT image) of the GA-EIT algorithm is better than that of the MNR algorithm.关键词：image reconstruction;electrical impedance tomography;genetic algorithm2|898|3更新时间：2025-07-16
- 摘要：In this paper,first,a signature encryption scheme with specified receiver verification is proposed.The scheme perfectly integrates digital signature scheme with public key cryptography system.Compared with common digital signature scheme,it has authentication,secrecy,data integrity and privacy of the receiver.Then,we use threshold scheme to construct a (t,n) threshold shared verification signature encryption scheme.Compared with proposed threshold shared verification signature encryption scheme,it has more secrecy of data transmission,requires smaller communication cost,performs efficiently and decides exactly which verifier tampers secret shadow etc.关键词：digital signature;shared verification;signature encryption2|915|7更新时间：2025-07-16
- 摘要：In this paper three systems using a concatenation of two short convolutional codes in place of a single long convolutional code are proposed and evaluated.Specifically,the systems use a R=2/3 with K=3,R=3/4 with K=2 and R=1/2 with K=7 code.The first two systems employ a soft decision followed by a hard decision Viterbi decoder.The most attractive feature of these systems is the reduction in the complexity of the decoders,and hence the entire system,that varies from 25% to 50% of that of the baseline system.关键词：convolutinal code;concatenation;complexity2|1082|0更新时间：2025-07-16
- 摘要：A joint source/channel coding modulation algorithm based on TTCM (Turbo Trellis-Coded Modulation) is presented,which achieve bandwidth-efficient and high reconstructive quality.The source decoder is optimized by minimizing the end-to-end system distortion.The soft output values of TTCM decoder are applied directly to the designed optimal source decoder.Simulation results show that compared with the system with hard decoding,the proposed algorithm can objectively gain 2 dB improvement of decoded source in terms of SNR.关键词：Turbo trellis-coded modulation;end-to-end distortion;soft-decision decoding2|928|2更新时间：2025-07-16
- 摘要：In this paper,a new blind equalization method based on the modified principle of Autocorrelation Matching for Multiple-Input Multiple-Output (MIMO) Channel is presented.Theoretically,it can consistently enforce the zero-forcing condition in AWGN channel when SNR varies.Simulation results shows that compared with AM and LMS method,it is multiple access interference (MAI) resistant,and intersymbol interference (ISI) resistant.关键词：autocorrelation matching;blind equalization;MIMO channel2|865|0更新时间：2025-07-16
- 摘要：This article focuses on analyzing the security mechanism of IEEE Standard 802.11.Itis proved in this article that there are many security holes existing in the security mechanism,which is not immunized from the malicious attack.And in view of authentication,privacy,integrity and nonrepudiation,the security mechanism is unable to ensure the security of the WLAN telecommunication.Proper solutions are proposed to overcoming the weakness of the security mechanism.关键词：WEP;authentication;shared key;key stream;RC42|1569|7更新时间：2025-07-16
- 摘要：A method of reducing the computation complexity of a base-stations channelizer is presented in this paper.Through using a interpolated second-order polynomials(ISOP)filter to shape the Inverse Discrete Fourier Transform(IDFT) filter bank,the IDFT filter bank can be used as a base stations channelizer directly.The complexity of implementing this channelizer is lower,so it is suitable to be used in base stations implemented with software radio technique.Theoretical analysis and simulation result show that with the system performance remains almost fixed this method is 17% more efficient than the Open-Filter-Bank(OFB) channelizer proposed by K.C.Zangi[1] in implementing the channel filter.关键词：software radio;sample rate conversion;IDFT filter banks;interpolated second-order polynomials(ISOP)2|800|0更新时间：2025-07-16
- 摘要：Three-dimension finite element modeling has been used to simulate and compare the current density,temperature and the gradients of distribution in Copper-filled via hole structure.To the same barrier material,the via hole with different slope has been simulated.The result of the simulation shows that optimizing the slope of the via hole and selecting the barrier material will improved the interconnect reliabiling.All these provide valuable reference to the design of the via hole.关键词：Cu interconnect;via;finite element;barrier material2|1244|2更新时间：2025-07-16
- 摘要：This paper studies the application of multi-channel fusion in the SAR image classification.In order to make full use of the membership information of pixel to the object classes,we use Bayesian fusion to fuse the information on measurement level.As prior probability of every object class is used in fusion,two methods are used to estimate the probability.The estimation causes a kind of mosaic effect,so modulated Gaussian distribution is introduced to deal with the problem but setting higher threshold to end the iteration proves to be a better method.In order to get an overall prior probability for every object class,three fusion methods of prior probabilities are proposed.Finally,a relative optimal method of multi-channel SAR image classification is achieved with experiments and studies.关键词：SAR image;multi-channel fusion;prior probably estimation;prior probability fusion2|1101|8更新时间：2025-07-16
- 摘要：In over-the-horizon radar (OTHR),the selection of transmitted bandwidth is limited by lots of crowded and powerful interference.It is difficult to find a broad and uncontaminated frequency band which results in low range resolution and signal-to-interference and noise ratio(SINR).A desired method is suppressing interference within a definite bandwidth.Considering the poor sidelobe of notch filtering method,in which target signal is masked in the sidelobes of interference,the projection algorithm(PA) and adaptive cancellation algorithm(ACA)are introduced.It follows that PA has the advantage of low complexity of computation and low sidelobe by designing sub band filter group though the temporal response will be introduced.By adjusting the weights,ACA can eliminate sidelobe interference effectively at the cost of heavy burden of computation.The sidelobe level of pulse compression was reduced greatly which will increase target detection probability effectively.关键词：range resolution;notch filter;projection algorithm;adaptive cancellation2|990|2更新时间：2025-07-16
- 摘要：Radio frequency (RF) beamforming algorithms are impractical to achieve digital beamforming (DBF) directly by digital signal processing (DSP) techniques in real time.For phase shift keying (PSK) modulation techniques,this paper considers that RF beamforming algorithms can be implemented equivalently in baseband.For quadrature phase shift keying (QPSK) modulation technique,a baseband DBF algorithm of smart antenna fixed beams is presented.Compared with RF beamforming algorithms,the presented algorithm can achieve the same radiated patterns,but it requires quite low computational cost.The baseband DBF algorithm can make smart antennas be realized easily,and flexibly,perform better,and play an important role in practical applications.关键词：smart antennas;baseband digital beamforming;PSK;QPSK2|1163|2更新时间：2025-07-16
- 摘要：The ambiguity function of intra-pulse chirp and inter-pulse stepped frequency signal is analyzed and obtained according to new type radar.Firstly,the expression of the signal is given.Then the concrete expression of ambiguity function of the signal is derived in accordance with the negative-type definition of ambiguity function.Last the brief analyzing of the ambiguity function is completed and the conclusion that the signal can achieve the high resolutions of range and speed is proved.Making use of the signal,a test system is developed and the ability of high range resolution is verified.关键词：intra-pulse chirp;stepped frequency;ambiguity function;high resolution2|1339|3更新时间：2025-07-16
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