最新刊期
卷 38 ， 期 4 ， 2010
- 摘要：Modulation index estimation has important significance in demodulation, FM/PM classification of angle modulation signals, etc. First, angle modulation signals using monotone, PSK, FSK and so on as message signals, are analyzed in time and frequency domain. Then, uniform mathematical representation is constructed for angle modulation signals. Finally, a blind estimation algorithm for modulation index without any prior knowledge is deduced. Simulation results indicate that the algorithm is effective for modulation index estimation with above message signals.关键词：information processing technology;blind estimation;modulation index;angle modulation signals2|1568|2更新时间：2025-07-16
- 摘要：To make accurate estimation of the channel parameters for the fluctuant burst channel, a novel channel estimation algorithm based on iteration is proposed. By compensating estimation error of the fast correlation estimation algorithm, accurate channel parameters estimation is realized, and theoretical conclusions of the relation between compensation times and estimation performance are proved. Simulations results and performance analysis show that the proposed algorithm has the advantages of small estimation error, low computational complexity and anti multipath distortion. It can estimate the channel parameters efficiently in low SNR (less than 10 dB) situations, and improve the performance of the fast correlation channel estimation algorithm efficiently in high SNR (more than 10dB) situations.关键词：burst communication;iterative compensation;channel estimate2|1019|0更新时间：2025-07-16
- 摘要：A high-efficient coded cooperative scheme based on bit-interleaved coded modulation is proposed. Encoded bits of the cooperative user are partitioned into two frames, bit interleaved, mapped and then transmitted on the allocated time slots respectively. Bit interleaver is utilized to satisfy the fading coefficients of the different bits of a same symbol cound be modeled as i.i.d variables. One hand, the pairwire error probability over various fading channels is derived, and an upper-bound on bit-error probability is presented. Both theory analysis and simulations show that the BICM CC with high-order constellations can also achieve the full diversity under quai-static Rayleigh fading channels, whereas no any cooperation diversity over fast fading channels. On the other hand, labeling maps and interleavers are studied. It can be concluded that GRAY labeling is still optimum for the cooperative users and different interleavers of two frames can improve the performance.
关键词：bit-interleaved coded modulation (BICM);coded cooperation (CC);pairwise error probability(PEP);diversity2|1321|2更新时间：2025-07-16 - 摘要：The Signal Noise Ratio(SNR)of CDMA2000 mobile station signal falls sharply in non-cooperative reception, considering the height of receiving antenna and power constrains of Near-Far effect. It is difficult to get the location parameters in the non-cooperative signal. Begin with theoretical model analysis, this paper presents a signal strength of arrival(SSOA)estimation algorithm based on data-aimed accumulation statistics. The algorithm principle has been deduced in detail, and the simulation has been carried out using real air signal. The results show that, the performance of proposed algorithm gets better with accumulation grows, and hardly changes with the frequency offset within the tolerance of CDMA2000 mobile station signal. It is better than cyclic spectrum amplitude algorithm, Data-Aimed Maximum Likelihood (DAML)algorithm and Decision-Directed Maximum Likelihood (DDML) algorithm when SNR remains below -10dB.
关键词：CDMA2000;cellular;signal strength of arrival(SSOA);estimation;location2|937|0更新时间：2025-07-16 - 摘要：A wideband blind linear equalizer based on non-uniform subband decomposition is proposed in this paper. The key feature is that it utilizes the idea of power spectrum amplitude segmentation to perform the non-uniform subband decomposition, and optimizes the choice of the non-uniform subband filter coefficients, thus obviously improves the convergence speed of the blind linear equalization algorithm. In addition, the updating strategy of subband equalizer’s coefficients is discussed, and an effective trade-off between the convergence speed and computational complexity is presented. Theoretical analysis and simulation results prove the efficiency of the proposed wideband blind linear equalizer.
关键词：wideband wireless communications;blind linear equalizer;non-uniform subband decomposition;updating strategy of coefficients2|1383|6更新时间：2025-07-16 - 摘要：A new union carrier parameter estimation algorithm based on FFT is proposed for data-aided burst mode carrier recovery. The basic idea is that firstly get a coarse estimation by using the peak of a period gram and then gain an accurate estimation by using a new interpolation formula about the two lines beside the peak. Its accuracy is close to MCRB even in very low SNR. As proved by simulation, it can accurately estimate the carrier parameter with 64 symbols even when SNR is as low as -4dB, its estimation range is about 50% of the symbol rate and it’s easy to be implemented by hardware as the analyses of complicity implied. Suitable areas of application include carrier recovery in bust mode digital transmission under low SNR circumstance.
关键词：carrier recovery;burst mode communication;FFT;union estimation2|2166|11更新时间：2025-07-16 - 摘要：We consider an orthogonal relay channel, where the channel from the source to the relay and the channel from the source and the relay to the destination are orthogonal on time. Firstly, the upper bound and the lower bound of the capacity are proposed, and converge to the capacity, where the lower bound is based on partial decode-and-forward. Secondly, to maximize the capacity for Gaussian orthogonal relay channel, the resource allocation is studied. The simulations show that optimizing the time only brings very little loss about capacity compared to maximize all the possible parameters. The optimal time allocation is given analytically when optimizing the time only.
关键词：wireless communication;relay channel;channel capacity;resource allocation2|1305|1更新时间：2025-07-16 - 摘要：In Vertical Bell labs LAyered Space-Time (V-BLAST) Orthogonal Frequency Division Multiplexing (OFDM) systems with distributed transmit antennas, since the Carrier Frequency Offsets (CFO) between the receiver and each transmit antenna are possibly different, the simple CFO compensation method used in conventional systems becomes invalid. Rather than the existing linear frequency-domain equalization method that involves computationally complex matrix inversions, we proposed a CFO compensation method without need for matrix inversion by exploiting the underlying characteristics of the Zero-Forcing (ZF) detection and assuming low delay spread of the multipath channel. Simulation results show that the Symbol Error Rate (SER) performance of the system is significantly improved by using the proposed CFO compensation method in the low delay spread cases of the three test environments in the ITU-R M.1225 channel model.
关键词：vertical Bell Labs layered space-time (V-BLAST);orthogonal frequency division multiplexing (OFDM);distributed transmit antennas;carrier frequency offset (CFO);compensation;zero-forcing (ZF) detection2|1260|1更新时间：2025-07-16 - 摘要：This paper examines the security of an image cryptosystem based on 3D chaotic Baker map. With known image, based on the affinity of 3D chaotic Baker map, the equivalent key of Baker map can be found by three linearly independent plain-cipher image grey values. The other equivalent key can be found by exhaustive attack. We estimate the computational complexity of our attack and prove that this image cryptosystem is insecure under the known image attack.
关键词：cryptanalysis;equivalent key attack algorithm;affinity;3D chaotic Baker map;image encryption;chaotic cipher3|1452|6更新时间：2025-07-16 - 摘要：This paper presents an algebraic method for designing circulant-shift values of permutation matrices in an array sparse parity-chick matrix which defines the QC-LDPC codes. The basic ideal is that the problem of constructing an array H-matrix by the permutation matrix can be converted into the problem of constructing a subscript matrix, and then all elements (subscript values) in this subscript matrix, i.e., the circulant-shift values of all permutation matrices in the array H-matrix, can be computed by a well-desinged sequence expression which is a function of the row and column weight of H-matrix and the dimension of permutation matrix and can be formed by the necessary and sufficient condition of Fossorier. The H-matrix formed by this method can eliminate the cycle 4 and can form at least girth 6.关键词：low-density parity-check codes;sparse parity-check matrix;subscript matrix;girth.2|1811|5更新时间：2025-07-16
- 摘要：A transmission scheme based on channel coding was proposed for multiple-input multiple-output orthogonal frequency-division multiplexing system concatenating space-time block code with beamforming. Firstly, the constellation distance which guaranteed user’s QoS was derived utilizing the statistical channel state information from the perspective of coding gain. Secondly, it was proved that this optimization problem was convex programming problem and the closed form solution for optimal power and bit loading was deduced according to Karush-Kuhn-Tucher conditions. Finally, an adaptive non-iterative resource allocation algorithm was put forward. The simulation results demonstrate that the algorithm is close to the theoretical value of the system throughput and has very low computational complexity which can meet the requirement of real-time communication. The lower the code rate of LDPC is, the higher the system throughput becomes.
关键词：multiple input multiple output;Orthogonal frequency division multiplexing;Statistical channel state information;Karush-Kuhn-Tucher conditions;channel coding3|1443|0更新时间：2025-07-16 - 摘要：By analyzing the limitation of the traditional two-dimensional LDA, a new SAR image recognition algorithm based on two-dimensional subclass discriminant analysis is proposed in this paper. First, image preprocessing of SAR image is performed, which includes image aligning and power transformation. Then image Euclidean distance NN-Clustering is proposed to divide the datasets per class into multi-subclasses, and feature matrix is extracted by two new methods, i.e. 2DSDA and Alternative-2DSDA. Finally, a nearest neighbor classifier is employed to classify the extracted features. Experimental results with MSTAR dataset verify the correctness and effectiveness of the proposed method.
2|1379|4更新时间：2025-07-16 - 摘要：Treatment of error correlation between local estimations is principal part of distributed estimation fusion and track fusion. In view of current situation, in which fusion of multi-sensor hybrid multiple model estimations is still not touched, at first, recursive computation methods for error cross-covariance matrix between local estimations obtained by interactive multiple model estimators whose model set are completely same or partly same is derived. Second, through simulation, the positive definite of cross-covariance matrix is discussed, and its relationship with process noise of maneuver motion model of IMM estimator is investigated. Further, above achievement makes applying Barshalom-Campo algorithm to fusion of IMM estimations as possible, its validity is verified through Monte-Carlo simulation. Compared with other fusion algorithms that ignore error correlation, performance of BC algorithm is more truly.
关键词：decentralized fusion;error cross-correlation;cross-covariance;hybrid estimation;interacting multiple model2|1909|3更新时间：2025-07-16 - 摘要：Applying nonlogarithmic additive model for SAR image, the distribution characteristic of SAR image isotropic regions are researched in Nonsubsampled Contourlet Transform (NSCT) domain, and then Gaussian Model is proposed to model the nonlogarithmic additive noise of the isotropic region in NSCT domain. Based on this model, we apply local sliding windows and adaptively estimate the variation of the nonlogarithmic additive noise, and then the solution of real NSCT coefficient is determined by using Maximum a Posteriori (MAP). Without applying logarithmic transform for original SAR image, the proposed method holds a good ability of radiometric preservation, the speckle is despeckled well while has less Pseudo-Gibbs phenomenon in uniform regions, edges and textures of despeckled image are also clear. Our algorithm possesses high performance over many traditional algorithms according to vision or objective evaluation.关键词：SAR image despeckling;nonsubsampled contourlet transform;Local Gaussian Model;maximum a posteriori2|2883|15更新时间：2025-07-16
- 摘要：A novel approach is presented to achieve high range and azimuth resolution wide swath with high Signal-Noise-Ratio based on the plane-array Multiple Input Multiple Output Synthetic Aperture Radar (MIMO-SAR) system by the combination of intrapulse scanning and two-dimensional spatial filter and bandwidth synthesis. This paper presents the plane-array MIMO-SAR model with the intrapulse scanning technique; We analyze the improvement of performance of the system by introducing intrapulse scanning in the MIMO-SAR model。With respect to the range ambiguities led to intrapulse scanning and Doppler ambiguities caused by low pulse repetition frequency, two-dimensional spatial filter is used to tackle range and Doppler ambiguities; at the same time bandwidth synthesis based on more the degrees of the freedom provided by the MIMO-SAR system is used to realize high range resolution. The plane-array MIMO-SAR system can be used to realize high SNR and two dimensional high resolutions, and overcomes the contradiction between the high resolution and wide swath, and breaks through the conflict between high SNR and wide swath.
2|1374|6更新时间：2025-07-16 - 摘要：This paper presents the design and experiment of the folded half mode substrate integrated waveguide (FHMSIW) slot bandpass filters. Top layer and middle layer slot super-wide-band FHMSIW filters are simulated and fabricated based on double layer standard printed circuit board (PCB) process. The size of the FHMSIW filter is reduced nearly by 50% compared with half-mode substrate integrated waveguide (HMSIW) filter. Performances of these super-wide bandpass filters with low insertion loss and sharp out-of-band characteristics are observed from both simulated and measured results.
关键词：folded half mode substrate integrated waveguide (FHMSIW);HMSIW;bandpass filters2|2259|0更新时间：2025-07-16 - 摘要：By analyzing the impact of the input factors on the output value in nonlinear function, it is suggested that when the input factors are independent, the Fourier Amplitudes which showing sensitivity values are relied mainly on the fundamental frequency. As a result, a fast pruning algorithm for the hidden neurons in the neural network is proposed based on the Fourier amplitude sensitivity test method. In essence, the Fourier amplitudes on the assigned frequencies of the hidden layer outputs are computed. Then the sensitivity of each hidden neuron to the neural network output is obtained. Finally, the redundant hidden neurons are pruned according to their sensitivity values to obtain a network with compact structure. The propose method is used in the soft measurement for Chemical Oxygen Demand(COD), which is a quality parameter of waste water. The experimental result shows that our proposed method is much faster than the Fourier amplitude sensitivity test method. The remaining neurons are the same after pruning for the two methods .
关键词：sensitivity;Fourier amplitude;Neural network pruning2|1418|4更新时间：2025-07-16 - 摘要：A new interacting multiple model(IMM) algorithm based on particle filter is proposed to track a randomly moving speaker. Based on the characteristic of speaker tracking problem, the proposed method represents the dynamic model with Markov jump system and filtering the system state with particle filter. The interacting process is accomplished by properly selecting the sampling region. Thus, not only the number of particles in each mode can be controlled so that the degeneracy problem around mode transition is avoided, but also the Gaussian assumption of posteriori probability density function of the state is cancelled. Simulation results show the validity of the proposed method.
关键词：speaker tracking;interacting multiple model;jump Markov system;particle filter;state estimation2|1307|5更新时间：2025-07-16 - 摘要：A semi-fragile, block-wise and content-based watermarking method for tamper detection and recovery is presented in this paper. The non-overlapping blocks are used and the watermark bits for authentication are embedded into the middle frequency region of each block in the ST domain. The embedding process is based on the discovery which the sign of the most ST coefficients maintain invariant. For the recovery mechanism, the recovery bits generated from the compressed original image are embedded into the least significant bits (LSB) of the watermarked image. The degree of the authenticity is measured by the false positive detection rate and false negative detection rate. Simulation results demonstrated that our method is able to accurately detect and localize the tampered region as well as approximately recover it. Furthermore, as compare with the DCT and PST based schemes, our proposed method obtains better performance when both malicious and non-malicious manipulations are applied together.
关键词：semi-fragile watermark;image authentication;recovery2|1480|11更新时间：2025-07-16 - 摘要：Skyline query processing in distributed environments has recently received a lot of attention in information retrieval community. However, most existing literatures do not consider how to efficiently reduce the transferring cost of skyline quereis on distributed networks. In this paper, we propose RTCSQDN(Reducing the Transferring Cost of Skyline Queries over Distributed Networks), the efficient sound and complete algorithm for balancing the cost of transferring data and skyline computation cost on the distributed networks. Specially, the PDSQDN algorithm makes use of the semantic rela-tionship between parent-space skylines and child-space skylines, and transfers the data through three phases. Moreover, we present a novel policy, i.e. PTGPV (Policy for Transferring Grouping Position Values), to transfer multi-dimensional objects. The PTGPV policy only transfers the position values of objects for most dimensional-spaces, and hence it can efficiently minimize the volume of data transferred. We also present detailed theoretical analyses and extensive experiments that dem-onstrate our algorithms are both efficient and effective.
关键词：information retrieval;skyline query;distributed networks;transferring cost2|1191|0更新时间：2025-07-16 - 摘要：Extracting shape feature is the key point of content-based 3d model retrieval. For this problem, a new approach is proposed for constructing 3d shape descriptor using spatial symmetry transformation. The main idea of this method is that symmetry is an important cue for all objects. At first, symmetry transformation of pair point is calculated, and the points come from spherical uniform sampled. Then symmetry space is built by pair symmetry relation. And using space clustering gets region symmetry description of 3d model. At last, range region symmetry descriptors in descend order to form shape descriptor of whole 3d model. This descriptor is robust to 3d model simplification, subdivision and other geometry operation. Retrieval response time is also satisfied. The effectiveness of the proposed approach is verified by three different sides that are feature similarity comparing, retrieval efficiency and results demonstration.
关键词：3D model matching and retrieval;Shape descriptor;Symmetry transformation;Spherical uniform sampling;Symmetry space clustering2|1971|4更新时间：2025-07-16 - 摘要：A new algorithm, Laplacian MinMax Discriminant Analysis (LMMDA), is proposed in this paper for supervised dimensionality reduction. LMMDA aims at learning a linear transformation which is an extension of Linear Discriminant Analysis (LDA). Specifically, we define the within-class scatter and the between-class scatter using similarities which are based on pairwise distances in sample space. After the transformation, the considered pairwise samples within the same class are as close as possible, while those between classes are as far as possible. The structural information of classes is contained in the within-class and the between-class Laplacian matrices. Thus the discriminant projection subspace can be derived by controlling the structural evolution of Laplacian matrices. The performance on several data sets demonstrates the competence of the proposed algorithm.
关键词：dimensionality reduction;supervised learning;discriminant analysis;Laplacian EigenMap2|1385|1更新时间：2025-07-16 - 摘要：Proposes unequal clusters of routing algorithm based on divided virtual region for “thermal region” in the wireless sensor network。The routing algorithm gives the task of clusters divided to sink node with non-limited energy, therefore , the scale of inside cluster layer which near the sink node is smaller than outer layer cluster。To realized the distributional election work of cluster head and avoided energy consumption in each wheel, we take main and vice cluster head into the structure of clusters。 The ARMA forecast model has been intruduced into the switch process of main cluster head, therefor it has not only avoided main cluster head dies because of energy consumes completely, but also avoided the network divided as well as the short life of the network caused by the death of main cluster head。 Compared with the tradition routing algorithm， the simulation result in the NS2.26 indicated that this routing algorithm prolonged the life of WSN。
关键词：WSN;Route;ARMA2|1507|12更新时间：2025-07-16 - 摘要：Looking for usable gateway is a process, which brings the biggest overhead, in MANET accessing Internet. For controlling the routing overhead effectively, an accessing network overhead control algorithm, which based on gateway pheromone, is proposed in this paper according to the similar between ant searching path and mobile node searching gateway. By simulating the pheromone’s update process in ant colony algorithm, this algorithm uses information carried in RREP to update gateway pheromone. According to the pheromone density on the link, link bandwidth and delay, the node computes transmission probability and transmits the RREQ. This algorithm is simulated by NS2.29. The test result indicates that though it increases average delay appreciably, it reduces normalized routing overhead effectively and increases packet delivery radio. The validity of algorithm is validated.
关键词：overhead control;mobile ad hoc networks（MANET） accessing;gateway discovery;gateway pheromone2|978|3更新时间：2025-07-16 - 摘要：How to efficiently utilize the spectrum resource is one of the fundamental issues in wireless mesh networks. Recently some work began to explore the dynamic channel width adaptation. In this paper, we show the optimal channel width adaptation can be reduced into the “packing and compression” problem. And we propose distributed traffic-aware algorithms to jointly exploit channel width adaptation and the multi-interface technology for wireless mesh networks. Simulation shows our algorithms can significantly improve network performance.
关键词：wireless mesh networks;spectrum assignment;channel width adaptation;graph interval coloring2|1332|5更新时间：2025-07-16 - 摘要：The paper proposes a novel optimization approach of performance for WSN. The end-to-end data rate per the unit of energy is introduced such that the integrated effects of the routing algorithm, the access control protocol and the transmission technologies on the performance of WSN are discussed. The packet success ratio and delay per hop were derived, based on which the end-to-end packet success ratio, delay and energy cost were deduced. Finally, the expression of the average end-to-end data rate was derived and the performance of WSN was analyzed. The simulation results demonstrate that the performance of WSN can be enhanced greatly by optimizing the transmission probability of packet and error correcting capability.
关键词：Wireless sensor networks;optimization;energy efficiency;routing strategy;delay2|2969|5更新时间：2025-07-16 - 摘要：A modeling method of throughput in Concurrent Multipath Transfer (CMT) environment is proposed and a simplified algorithm is also given under the premise of accuracy. The increase mechanisms of congestion window are analyzed and interpreted based on the features of different transmission phases. The model estimates the throughput according to the changes of round trip time and congestion window. Simplified algorithm can decrease the complexity sharply when we implement our idea on Matlab platform. And the agreement of calculation results and simulation results is satisfactory.
关键词：concurrent multipath transfer;throughput model;congestion window;round trip time3|1505|6更新时间：2025-07-16 - 摘要：Complex network theory has provided the new train of thought and method to the research of malware's propagation. In this paper, against malicious software spread of the actual mechanism，we develop a new model, called the discrete probability susceptible-infectious (short for DP-SI)，which could be applied to any network topology. At the same time, the node information network model method have been proposed for investigating complex network simulations, provided an efficiency research flat for simulating of propagation dynamics in the cosmically complex network as well as building discrete propagation dynamics model. The results show that this model is closer to reality than the traditional model, and it has some significance in the control of malicious software.
关键词：malware propagation;SI model;immunization;node information network model3|1434|2更新时间：2025-07-16 - 摘要：Maximum a posteriori (MAP) methods have been widely applied to the ill-posed problem of image reconstruction, such as positron emission tomography (PET) imaging. In this paper, a family of new generalized Gibbs priors based on MAP method, which exploits the basic affinity structure information in an image, is proposed. The generalized Gibbs priors can suppress noise effectively while capturing sharp edges without oscillations. A binary optimal reconstruction strategy is established using a locally linearized scheme in the framework of a standard paraboloidal surrogate coordinate ascent (PSCA) algorithm. The proposed generalized Gibbs priors based MAP reconstruction algorithm has been tested on simulated and real phantom PET data. Comparisons of the new priors model with other classical methods clearly demonstrate that the proposed generalized Gibbs priors perform better in lowering the noise, and preserving the edge and detail in the image.
关键词：positron emission tomography (PET);maximum a posteriori (MAP) reconstruction;traditional Gibbs prior;generalized Gibbs priors2|1206|2更新时间：2025-07-16 - 摘要：PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) MRI offers an effective means for compensating rigid motion during data collection. So far, this method has been evaluated clinically and found to be able to improve image quality through quantification and correction for head motion, where hypothetically only rotation and translation is present. During imaging of other parts of body, especially in abdomen, soft tissue such as liver, deformation occurs frequently. Traditional PROPELLER reconstruction can’t model this kind of non-rigid body motion and can only attain limited compensation through correlation weighting. In this paper, a new method was proposed for affine motion correction, which extracted affine motion information from image space and compensated it in k-space. The experimental results show that the proposed method could correct artifacts due to not only the rigid motion but also the affine motion.
关键词：MRI (magnetic resonance imaging);PROPELLER;motion correction;affine transformation2|1463|0更新时间：2025-07-16 - 摘要：Based on the analyses of the recent routing research productions of the cognitive radio networks (CRN), this paper identifies five critical challenges on the routing research of CRN: neighbor discovery, deafness problem, neighbor disappearance, routing problem and cross-layer design, then some topics about common control channel, path delay and the technical metrics are discussed from the view of research method, which must be considered on the routing research of CRN. After that, we summarize and analyze the scenario design patterns of routing research from four aspects: medium, channel, node and network; study and discuss the main research productions from the views of optimization scheme and routing topology algorithm / protocol in detail at the end of this paper.
关键词：cognitive radio;network;routing;survey2|2129|10更新时间：2025-07-16 - 摘要：The operating frequency and precision of traditional range-gate control circuits designed with discrete components are hard to satisfy the demand of high-repetition-rate measurement. By analyzing the timing sequences of high-repetition-rate range gate, a method based on FPGA is proposed and implemented. This method makes full use of FPGA advantages at calculating, storage and clock managing, 200MHz Clock generated by DCM (Digital Clock Manager) results in the circuit with 5ns resolution and transferring range-gate data via EPP (Enhanced Parallel Port) insure operating frequency up to several kilohertz. Using the prototype circuit makes success of the experiment of high-repetition-rate Satellite Laser Ranging in Shanghai Astronomical Observatory, and makes it become one of stations with high-repetition-rate SLR technology in the world.
关键词：satellite laser ranging;FPGA;range-gate control circuit;high-repetition-rate3|1435|7更新时间：2025-07-16 - 摘要：Three modifications are proposed for the Non-Local Means (NLM) de-noising algorithm. The symmetric property existing in many images is exploited first, symmetric transformations are introduced in neighborhood comparison so that image self-similarity property can be made better use of; Then an adaptive filtering parameter selection method is proposed based on image intensity statistics; Besides, a two-stage Non-Local Means filtering method is proposed adopting the structure preserving property of NLM algorithm. De-noising results for test images demonstrate that compared with the original algorithm, the modified one can remove noise more efficiently with image structures well preserved, the PSNR can be improved by 5.9dB at most, and the de-noising performance outperforms that of the BM-3D algorithm.
关键词：non-local means;symmetric transform;adaptive weighting;de-noising2|2221|19更新时间：2025-07-16 - 摘要：This paper investigates the direction-of-arrival (DOA) estimation of coherent sources with conjugate cyclostationary properties. A virtual array-based forward backward spatial smoothing method is proposed. By properly applying multiple lag conjugate cyclic correlation functions of specified sensor outputs, a virtual array is constructed first. Based on which, the spatial smoothing technique is then introduced to estimate the DOAs of all the signals of interest. Theoretical analysis and experimental results demonstrate that, compared with the FBSS-based Conjugate Cyclic MUSIC and Conjugate Cyclic Hankel Approximation method, the proposed algorithm not only avoids the optimal lag choosing problem, but also achieves better performance in estimation accuracy. Besides, this method is robust against the difference in signal DOAs. In addition, the proposed method can also be applied to the signals with cyclostationary properties.
关键词：array signal processing;direction-of-arrival;cyclostationarity;coherent;spatial smoothing3|2050|9更新时间：2025-07-16 - 摘要：In the downlink of TD-SCDMA, the training sequences for all the downlink users are received by the receiver of a specific user. Based on this characteristics, a multi-user aided downlink channel estimation method is proposed. In this method, the information in the channel estimation windows of all the downlink users at the same time slot is first preprocessed to suppress the channel responses contributed by interference (noise); and the preprocessed channel responses in all the channel estimation windows are then combined with appropriate weights to enhance the SNR of the channel response in the channel estimation window of the specific user. Computer simulation results show that the proposed method can significantly improve the performance of channel estimation for the downlink of TD-SCDMA.
关键词：TD-SCDMA;Steiner Estimator;channel estimation;Channel Estimation Window3|1095|1更新时间：2025-07-16 - 摘要：Based on the research on S-box constitution algorithm of Advanced Encryption Standard, we use the periodical characteristic of affine transformation in S-box to improve the circuit architecture and propose an area optimized combinational logic S-box implementation of AES. We multiply the circuit frequency and reuse the circuit with the pipeline technology. The synthesis result shows that the new S-box functional unit not only decreases the area of byte substitution compared with traditional S-box combinational logic by 47.53% and 41.49% and with truth table S-box combinational logic by 21.43%, but also maintains the critical delay of the circuit. Using the unit-gate model approximations, the hardware gate count of S-box is 880 gates. And the S-box scheme is applied to the application specific instruction processor for cryptography which is tested on Altera’s FPGA Cyclone II EP2C20.
关键词：S-box subbytes;affine transformation;combinational logic;area optimization2|2074|4更新时间：2025-07-16 - 摘要：In this paper, a spectrally efficient communications system is introduced, i.e., the OFDM-FH communications system with PSK modulation scheme. In order to improve the system performance in fading channel, the maximum ratio-combining (MRC) diversity receiver is applied. Based on characteristic function method, the symbol error rate (SER) performance of the system is derived in additive white Gaussian noise and Rayleigh fading channels. The numerical results first indicate the relationship between SER and the parameters such as the size of frequency slots set, the number of OFDM subcarriers and the number of users. By the numerical and simulation results, the frequency resource of the proposed system is saved and the SER is decreased, in compared with other similar OFDM-FH communications systems.
关键词：multi-user OFDM-FH system;symbol error rate (SER);AWGN channel;Rayleigh fading channel2|1445|1更新时间：2025-07-16 - 摘要：A ground moving target indication (GMTI) method for distributed space-based monopulse radar is proposed. This method takes advantage of the space-time distribution of the mainlobe and gratelobe echoes of distributed space-based monopulse radar, and can detect targets buried in gratelobe clutters during one coherent processing interval (CPI), thus more area coverage rate (ACR) and higher wide area surveillance ability can be achieved. It’s shown that this method is also computation-saving and is very suitable for on-board processing.
关键词：Distributed Space-Based Radar;GMTI;Monopulse Angle Measurement;ACR2|1189|1更新时间：2025-07-16 - 摘要：Using the idea of micro motion modulation for reference, a novel active jamming method is proposed for Synthetic Aperture Radar (SAR). Several key jamming parameters are determined, the jamming image result is analyzed, an implementation procedure based on Digital Radio Frequency Memory, well as the influence of reconnaissance errors on jamming performance, is put forward. Furthermore, simulation experiments have been done based on the raw data. The result shows that, this jamming signal is processed coherently in the range direction and partially coherently in the azimuth direction, which can produce multiple false targets in the azimuth direction. As an effective and sound jamming, this method, along with multiple equipped or developing jamming equipments, can enhance the defense and survivability for important targets.
关键词：Synthetic Aperture Radar(SAR);micro motion;active jamming;multiple false targets;digital radio frequency memory (DRFM);error analysis2|2302|18更新时间：2025-07-16 - 摘要：Based on clonal selection principle and the immunodominance theory, a new immune clustering algorithm, Immunodomaince based Clonal Selection Clustering Algorithm (IDCSCA) is proposed in this paper. An immunodomaince operator is introduced to the clonal selection algorithm, which can realize on-line gaining priori knowledge and sharing information among different individuals. Firstly, the gene of elites in antibody population can be extracted and generalized to ordinary antibodies, by the interaction, the whole antibody population evolves. The proposed method has been extensively compared with Fuzzy C-means (FCM), Genetic Algorithm based FCM (GAFCM) and Clonal Selection Algorithm based FCM (CSAFCM) over a test suit of several real life data sets and synthetic data sets. The result of experiment indicates the superiority of the IDCSCA over FCM, GAFCM and CSAFCM on stability and reliability for its ability to avoid trapping in local optimum.
关键词：clone selection;genetic algorithm;immunodominance;fuzzy clustering2|1720|8更新时间：2025-07-16 - 摘要：In immune clonal selection algorithms, global convergence ability is worse if clonal selection is only adopted. However, immune algorithm with (μ+λ) selection is easy to fall into premature convergence. In order to ensure the exploitation and exploration, an adaptive immune clonal selection cultural algorithm is proposed. Dual structure of cultural algorithm is adopted in the algorithm. And a hybrid selection strategy integrating (μ+λ) selection and clonal selection is put forward. The proportion of population influenced by each selection method is adaptively adjusted according to implicit knowledge extracted from the evolution process. Aiming at benchmark functions, simulation results indicate that the algorithms can effectively improve the speed of convergence and have better computation stability.
关键词：adaptive;clonal selection;（μ+λ）selection;cultural algorithms;immune algorithm2|1775|14更新时间：2025-07-16 - 摘要：Proportionate adaptive algorithms exploit structure characteristic of sparse impulse response to considerably improve the convergence speed. However, the requirements of fast convergence and low steady-state misalignment are conflict for constant step-size adaptive algorithms, whose step size parameter has to be selected by compromising these two conflict requirements. In this article, a novel variable step-size method is proposed for proportionate adaptive algorithm to solve this problem. By using principle of minimal disturbance to proportionate adaptive algorithm, we first provide a derivation of proportionate NLMS. Then by taking into account the disturbance signal, forcing the a posterior error to cancel negative effect of disturbance signal, we obtain a new optimization criterion. At last, using this criterion, we propose a step size control approach for proportionate NLMS algorithm. Simulation results verify the effectiveness of the proposed algorithm.
关键词：adaptive filter;network echo cancellation;sparse impulse response;variable step-size2|1657|21更新时间：2025-07-16 - 摘要：Orthogonal discriminant locality preserving projections is an effective feature extraction, but it may encounter the small size samples problem when it is applied in face recognition task. In addition, it is only a linear feature extraction technique. A kernel orthogonal discriminant locality preserving projections is proposed. The key is to how to compute the nonzero space of the total scatter matrix in the higher dimensional feature space. As to this problem, the kernel function technique and the eigenfaces method that transforms the computation of the high order matrix into the computation of the low order matrix are used, and then the actual computation of the nonzero space of the total scatter matrix in the higher dimensional feature space is reduced to a standard eignenvalue problem. In addition, the proposed algorithm can effectively overcome small size samples problem. The numerical experiments on facial databases show that the proposed method is effective and feasible.
关键词：orthogonal discriminant locality preserving projections;feature extraction;face recognition;total scatter matrix;kernel function2|1211|3更新时间：2025-07-16 - 摘要：To decrease overhead of on-demand vector routing protocol and overcome shortcomings of location-aided routings about getting location information, a novel location-aided ad hoc on-demand vector routing protocol (LAODV) is proposed. In LAODV, location information is got on demand. During route discovery, flooding, location correct-based greedy forward strategy(LCGF) and limited flooding in expected zone are combined to improve the performance. In addition, a novel method for routing maintenance and a strategy of local multi-path backup routing are illustrated. Simulation results show that, LAODV can achieve fine performance in packet delivery ratio, delay, and routing overhead.
关键词：Ad Hoc networks;routing;greedy forward;multi-path2|1132|4更新时间：2025-07-16
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