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Table of Content

    20 October 2015 Volume 42 Issue 5
      
    Original Articles
    Low complexity lattice reduction aided precoding algorithm with orthogonality defect threshold for MIMO systems
    WANG Wei;LI Yongzhao;ZHANG Hailin
    J4. 2015, 42(5):  1-6+32.  doi:10.3969/j.issn.1001-2400.2015.05.001
    Abstract ( 506 )   PDF (552KB) ( 588 )   Save
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    To reduce the complexity of lattice reduction aided (LRA) precoding, a low complexity LRA precoding based on the orthogonality defect threshold is proposed. We introduce the orthogonality defect (od) threshold as an early-termination condition into the lattice reduction (LR) algorithm which can reduce computational complexity by adaptively early terminating the LR processing. And, sorted QR decomposition of the channel matrix is used to enhance the probability of the early termination which further reduces computational complexity. Moreover, to achieve a favorable tradeoff between performance and complexity, we define a power loss factor (PLF) to optimize the od threshold. Simulation results show that the proposed algorithm can achieve significant complexity savings with nearly the same bit-error-rate (BER) performance as the traditional LRA precoding algorithm.

    Design of the discriminator for tracking the loop under short-delay multipath interference
    TONG Zhao;LI Bingbing;HUI Yongtao;ZHONG Xingwang;LIU Hao
    J4. 2015, 42(5):  7-12+62.  doi:10.3969/j.issn.1001-2400.2015.05.002
    Abstract ( 460 )   PDF (628KB) ( 519 )   Save
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    The traditional multipath eliminating methods have poor performance under short-delay multipath interference and therefore a discriminator constructing method for tracking the loop is presented. Firstly, from the analysis of the output characteristics for in-phase/quadrature-phase early, late, and prompt channels under the short-delay multipath, an improved late channel is constructed. The output of the loop discriminator is defined as the normalized function of the power difference between early and late signals. It made the error between the code phase of the direct signal and that of the local estimated signal is less than the pre-determined threshold. Theoretical analysis and simulation results show that, compared to traditional methods, the multipath mitigation technique based on the improved loop discriminator can suppress the code tracking errors produced by the multipath when the relative delay is less than 0.5 chip and effectively inhibits short-delay multipath interference, thus improving the tracking and measurement accuracy in navigation and docking systems.

    Semi-blind SLM scheme for reducing the PAPR of MIMO-OFDM systems
    JI Jinwei;REN Guangliang;ZHANG Huining
    J4. 2015, 42(5):  13-19+146.  doi:10.3969/j.issn.1001-2400.2015.05.003
    Abstract ( 467 )   PDF (586KB) ( 463 )   Save
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    A semi-blind selected mapping(SLM) scheme is addressed to reduce the peak-average-power ratio(PAPR) of Alamouti coded multiple-input multiple-output orthogonal frequency division multiplexing(MIMO-OFDM) systems.To enable low computational complexity as well as embedding of the side information into the data symbols at the transmitter, the input OFDM symbol sequence is partitioned into several interleaved subblocks, each of which is transformed into time-domain candidate signals by using the conversion vectors, and then the candidate signals for each subblock are multiplied with different phase offset factors and added up to obtain the transmitted candidate signals. At the receiver, the side information can be obtained by jointly detecting the phase offset factors of each subblock and the transmitted data can be detected without transmitting the side information. Analysis and simulation show that the proposed scheme can achieve a better side information detection performance and almost the same PAPR reduction and bit error rate(BER) performance with a much lower complexity at both the transmitter and receiver, as compared to the available semi-blind SLM schemes.

    Public key encryption with multi-keywords search
    LI Haoxing;LI Fenghua;SONG Chenggen;SU Mang;LIU Xin
    J4. 2015, 42(5):  20-25.  doi:10.3969/j.issn.1001-2400.2015.05.004
    Abstract ( 624 )   PDF (469KB) ( 530 )   Save
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    In order to improve the server-side keywords-searching efficiency in public key encryption by keyword search schemes, we propose a method of constructing reciprocal maps based on lagrange polynomial and a public key encryption by multi-keywords search scheme. In the scheme, each couple of reciprocal maps corresponds to a set of keywords. The sender makes ciphertext transformation for the set of keywords, and sends the result to the server. The receiver sends a searching-keyword trapdoor to the server. The server can restore the ciphertext of the keyword corresponding to the trapdoor for matching, only if the keyword belongs to the set. Only one pair computing is required to finish multi-keywords searching. The scheme is semantically secure in the standard model, and has a high efficiency of keywords searching with no restriction.

    Hybrid classifier based method for similar handwritten Chinese character recognition
    YAO Chao;LU Zhaoyang;LI Jing;JIANG Wei;FAN Zhihui
    J4. 2015, 42(5):  26-32.  doi:10.3969/j.issn.1001-2400.2015.05.005
    Abstract ( 466 )   PDF (1667KB) ( 678 )   Save
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    To solve the similar handwritten character recognition problem, a novel scheme is proposed to make better use of the feature's discriminative information. Different from the methods for extracting the extra feature for the similar characters, the Modified Quadratic Discriminant Function(MQDF) is first adopted to classify the feature, then the Support Vector Machine(SVM) is used to discriminate the similar characters without the extra feature. To collect the subset of similar characters, the confusion matrix is employed. A new structure for storing the dictionary of the SVM is also proposed for quickly searching. Experimental results on ETL9B show the superior performance of the proposed scheme to the methods for extracting the extra feature, which proves that the feature contains discriminative information for the similar characters and that the proposed scheme can utilize this information very effectively.

    Low complexity quantum private queries protocol
    HE Xiaoyun;PEI Changxing;YI Yunhui
    J4. 2015, 42(5):  33-37+74.  doi:10.3969/j.issn.1001-2400.2015.05.006
    Abstract ( 436 )   PDF (481KB) ( 395 )   Save
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    Private information retrieval(PIR) is an important privacy protection issue of secure multi-party computation, but the PIR protocols based on classical cryptography are vulnerable because of new technologies,such as quantum computing and cloud computing. The quantum private queries(QPQ) protocols available, however, has a high complexity and is inefficient in the face of large database. This paper, based on the QKD technology which is mature now, proposes a novel QPQ protocol utilizing the key dilution and auxiliary parameter. Only N quits are required to be sent in the quantum channel to generate the raw key, then the straight k bits in the raw key are added bitwise to dilute the raw key, and a final key is consequently obtained to encrypt the database. By flexible adjusting of auxiliary parameters θ and k, privacy is secured and the query success ratio is improved. Feasibility and performance analyses indicate that the protocol has a high success ratio in first-trial query and is easy to implement, and that the communication complexity of O(N) is achieved.

    ID-based trapdoor mercurial commitment under one-way functions assumptions
    ZHANG Wujun;LIU Yuding;GAO Yaqian;SUN Xi;WANG Yumin
    J4. 2015, 42(5):  38-42.  doi:10.3969/j.issn.1001-2400.2015.05.007
    Abstract ( 400 )   PDF (424KB) ( 426 )   Save
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    The notion of identity-based trapdoor mercurial commitment incorporates the advantages of both identity-based trapdoor commitment and trapdoor mercurial commitment. So far, the existing identity-based trapdoor mercurial commitment schemes are based on the strong Diffie-Hellman assumption or computational Diffie-Hellman assumption. One-way function existence is one of the fundamental assumptions in the cryptography. In this paper, we first propose a general construction for identity-based trapdoor mercurial commitment based on the one-way function. Meanwhile, we give a concrete instantiation based on the Boneh-Boyen signature scheme.

    New switch degree distribution for the LT code
    REN Peng;XIANG Zheng
    J4. 2015, 42(5):  43-47.  doi:10.3969/j.issn.1001-2400.2015.05.008
    Abstract ( 456 )   PDF (540KB) ( 389 )   Save
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    Truncated-binary exponential distribution is proposed for improving the occurrence of the decoding set, and Moved-robust soliton distribution is simultaneously put forward for increasing the occurrence of the decoding set. Combining the above two distributions, a new switch distribution is constructed in this paper. Simulation results show that the proposed method can reach 56% of initial decoding success, and that the total decoding success rate is higher than that by the original method by 9%~12%.

    SAR images segmentation algorithm using chain coding grid in G0 distribution
    ZHANG Zejun;SHUI Penglang
    J4. 2015, 42(5):  48-54.  doi:10.3969/j.issn.1001-2400.2015.05.009
    Abstract ( 764 )   PDF (10625KB) ( 320 )   Save
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    An adaptive weighted synthetic aperture radar(SAR) images segmentation model is proposed based on the minimum description length(MDL) principle to alleviate the influence of complexity of the SAR images' scene on segmentation results. In the model, G0 distribution is used for describing SAR image data, and the 4-neighborhood chain coding grid is utilized for coding boundaries of regions in the SAR image. An adaptive estimation method for the weight of the segmentation model is proposed using the SAR image data. The segmentation model is fast minimized by using region merging technology. Experimental results show that, compared with two methods of the same kind, the proposed method effectively alleviates the degree of over-segmentation in texture fields.

    Fast space-time adaptive processing method by using the sparse representation
    XIE Hu;FENG Dazheng;YU Hongbo;YUAN Mingdong;NIE Weike
    J4. 2015, 42(5):  55-62.  doi:10.3969/j.issn.1001-2400.2015.05.010
    Abstract ( 583 )   PDF (731KB) ( 378 )   Save
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    One of the key problems of space-time adaptive processing (STAP) is how to estimate the clutter covariance matrix (CCM) accurately with a small number of samples when the clutter environment is heterogeneous. The CCM estimation methods based on sparse representation (CCM-SR) can achieve a good estimation performance with only one or a few samples, which significantly improves the convergence rate of the STAP. By using the sparsity characteristic of the clutter spectrum, the CCM-SR method estimates the clutter spectrum and yields a good estimation of the CCM. However, there are often many pseudo-peaks in the clutter spectrum estimated by the sparse representation (SR), which will cause a CCM estimation error. By exploiting the special relationship of the clutter ridge curve between space domain and Doppler domain, we can eliminate the pseudo-peaks in the clutter spectrum effectively via fitting the curve of the clutter ridge and improve the estimation accuracy of the CCM. In addition, a byproduct of our method is the estimation of the flying parameters (the velocity of the radar platform, the crab angle and so on). Experimental results show that the proposed method can improve the performance of conventional STAP based on sparse representation (STAP-SR) and obtain a good estimation of the flight parameters.

    Parameter adaptive SAR image denoising method
    GAO Bo;WANG Jun;YUAN Hui
    J4. 2015, 42(5):  63-67.  doi:10.3969/j.issn.1001-2400.2015.05.011
    Abstract ( 500 )   PDF (2073KB) ( 396 )   Save
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    In the traditional SAR image nonlocal means denoising algorithms, the patch similarity is measured by the accumulation of the pixel similarities, and a good denoising performance can be obtained for the additive noise model. This paper extends this idea to the multiplicative noise model for the SAR image, and improves the PPB (Probabilistic Patch-Based) algorithm under the weighted maximum likelihood estimation framework. Since the parameters setting in the PPB algorithm is complicated and it cannot adaptively get the best performance, this paper proposes a particle swarm optimization based parameter adaptive nonlocal means algorithm for SAR image denoising. Finally, experiments compared with the canonical PPB method on the real SAR image are carried out. Experiments demonstrate that the proposed method has a good performance in speckle reduction and details preservation.

    Clutter pre-filtered method applied in bistatic airborne radar
    ZHOU Yan;FENG Dazheng;ZHU Guohui
    J4. 2015, 42(5):  68-74.  doi:10.3969/j.issn.1001-2400.2015.05.012
    Abstract ( 450 )   PDF (1319KB) ( 372 )   Save
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    In order to solving the problem of ineffective clutter suppression and target detection of space-time adaptive processing(STAP) in bistatic airborne radar, a clutter pre-filtering method applied in the bistatic airborne radar that takes advantage of radar operating parameters, platform velocity and so on is proposed. The velocity error of the airborne platform is also considered. Most of the clutter can be filtered so that the residual clutter can be completely suppressed by the well-developed STAP algorithm. Computer simulation results show that this method is effectively workable to several classical geometric configurations of bistatic airborne radar. The moving target detectability of the following STAP algorithm is also enhanced after this pre-filter.

    Analysis of the radiation of slotted waveguide antennas using the parallel MoM
    WANG Yong;LIN Zhongchao;ZHANG Yu;LIANG Changhong
    J4. 2015, 42(5):  75-79+132.  doi:10.3969/j.issn.1001-2400.2015.05.013
    Abstract ( 624 )   PDF (1127KB) ( 420 )   Save
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    This paper numerically analyzes the Ka band slotted waveguide antennas which are involved in engineering using parallel method of moments(MoM). For lack of the match terminator, it is difficult for the MoM to simulate the traveling wave antenna. To deal with this problem, the equivalent principle on the wave ports and the mode match methods are used to construct the model of wave ports. As an improvement, the waveguide and the wave ports are divided into different domains. The affections between the two domains are assumed as the external excitations of each domain. Then, the iteration method can be used to solve the equation. At the same time, the introduction of the parallel calculation technique can improve the ability of the MoM to analyze the electrically large targets. The agreement of the measurement result and numerical result proves that the model of wave ports proposed in this paper can help to solve the problem of the simulation of slotted waveguide antenna validly.

    Fast analysis of wide-band scattering properties of inhomogeneous dielectric bodies
    ZHAO Bo;GONG Shuxi;WANG Xing;DONG Hailin
    J4. 2015, 42(5):  80-85.  doi:10.3969/j.issn.1001-2400.2015.05.014
    Abstract ( 464 )   PDF (1129KB) ( 340 )   Save
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    The asymptotic waveform evaluation (AWE) based on the volume integral equation (VIE) is applied to accelerate wide-band electromagnetic scattering properties of arbitrarily shaped inhomogeneous dielectric bodies. For the analysis over a single frequency, the discontinuity of the normal component of the volume current on both sides of the medium interface should be considered. Nevertheless, the problem can be solved well by adoption of VIE and expansion of the electric flux density with SWG basis functions. However, the wide-band analysis requires repeated radar cross section (RCS) calculations over different frequencies, which takes excessively much time. To acquire the prediction of wide-band RCS rapidly, in this paper, AWE greatly reduces the computation time by deducing and computing the high derivatives of the impedance matrix and excitation vector, expanding the electric flux density with the Taylor series and further broadening the bandwidth using padé approximation. Finally, numerical examples are displayed to demonstrate the accuracy and efficiency of this method.

    Parallel FDTD computation of hundred thousand cores on a home-made supercomputer
    JIANG Shugang;LIN Zhongchao;ZHANG Yu;WEI Bing;ZHAO Xunwang
    J4. 2015, 42(5):  86-91.  doi:10.3969/j.issn.1001-2400.2015.05.015
    Abstract ( 569 )   PDF (2550KB) ( 478 )   Save
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    The massively parallel Finite-Difference Time-Domain(FDTD) computation using 100000 CPU cores is firstly implemented. Test results show that the parallel efficiency can reach up to 65% on 10240 CPU cores with 128 CPU cores as the benchmark. The research results in this paper indicate that the complicated electromagnetic problems can be solved accurately and efficiently using the method on the home-made supercomputer platform.

    Improved quasi-static effective medium model of the electromagnetic band gap (EBG) high-impedance surface
    SU Zijian;LIANG Changhong;LI Long;ZHAI Huiqing
    J4. 2015, 42(5):  92-97.  doi:10.3969/j.issn.1001-2400.2015.05.016
    Abstract ( 549 )   PDF (1534KB) ( 378 )   Save
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    For the complex electromagnetic property of the electromagnetic band gap (EBG) high-impedance surface, an improved quasi-static effective medium model is proposed, which makes a quantitative relationship among the geometry, medium properties and the electromagnetic properties of the EBG high-impedance surface. The macroscopic interaction of the wave with the EBG high-impedance surface is equivalent to that of the wave with an effective medium when the wavelength is large compared with the dimension of each cell of the high-impedance surface. With the effective medium model proposed by quasi-static electromagnetic theory, designs of the high-impedance surface and its application system such as antenna system can be implemented separately. Some numerical simulations and experiments of practical high-impedance surfaces are given to illustrate the applications and validity of the proposed model.

    Gaussian mixture PHD smoothing filter in unknown clutter
    LI Cuiyun;JIANG Zhou;LI Bin;ZHOU Xuan
    J4. 2015, 42(5):  98-104.  doi:10.3969/j.issn.1001-2400.2015.05.017
    Abstract ( 436 )   PDF (562KB) ( 390 )   Save
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    Aiming at the Multi-target tracking in the unknown clutter environment, this paper proposes a Gaussian Mixture Probability Hypothesis Density (GM-PHD) forward-backward smoothing algorithm, which improves the poor performance of the PHD filter when the clutter model and the prior knowledge are mismatching by estimating the clutter intensity with the finite mixture model. The forward-backward smoothing recursions are applied to improve the state estimation accuracy. Simulation results show that the proposed algorithm performs well in the unknown clutter environment and better than the conventional Gaussian Mixture PHD Filter without smoothing processing in the unknown clutter environment.

    Method to compute the reachability set of S3PR
    ZHANG Xiuyan;ZHONG Chunfu;JIA Jianyuan
    J4. 2015, 42(5):  105-109.  doi:10.3969/j.issn.1001-2400.2015.05.018
    Abstract ( 463 )   PDF (482KB) ( 403 )   Save
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    This paper proposes a novel approach to computing the reachability set by using place invariants and strict minimal siphons for S3PR with specific resource places. First, the set of invariant markings is enumerated. Then a necessary and sufficient condition is developed to decide whether a marking is spurious by analyzing the relationship between the number of tokens in the corresponding places of any strict minimal siphon and their bounds. In addition, the spurious markings are calculated. Finally, the reachability set of the net is generated by removing all the spurious markings from the set of invariant markings. Experimental results show the efficiency of the proposed method.

    Control of chaos of the linear-mode switched-capacitor converter
    LI Xianrui;ZHU Yanli;SHEN Rui;LIU Qian
    J4. 2015, 42(5):  110-114.  doi:10.3969/j.issn.1001-2400.2015.05.019
    Abstract ( 422 )   PDF (823KB) ( 387 )   Save
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    This paper studies the bifurcation and non-linear dynamic behaviors of the linear-mode switched-capacitor DC-DC converter with the parameter K and the fact that the system appears chaotic when the feedback coefficient is relatively large. In this paper we propose converter topology by increasing a reference voltage regulator module in the reference voltage input, which improves the system stability. The reference voltage regulator module consists of the two stage amplifier. In this study, the feedback coefficients of the converter with and without the reference voltage regulator module are analyzed, respectively. The output voltage of the time-domain waveform and phase diagram are obtained through the simulation Simulation shows that the reference voltage regulator module added can effectively suppress the chaos and improve the system stability.

    Robust adaptive threshold speech endpoint detection method
    ZHANG Junchang;ZHANG Dan;CUI Li
    J4. 2015, 42(5):  115-119.  doi:10.3969/j.issn.1001-2400.2015.05.020
    Abstract ( 430 )   PDF (740KB) ( 406 )   Save
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    Due to the fact that traditional Speech Endpoint Detection methods' performance degrads greatly in a low signal-to-noise ratio and nonstationary noise, a novel robust adatpive threshold endpoint detection method is proposed. First of all, the LSFM parameter is employed as the distinctive feature and the Burg spectrum estimation is applied to figure out the power spectrum, which can enhance the discriminative ability in classifying speech signals and noise, compared with the traditional speech features. Furthermore, an adaptive threshold based on the Bayes estimation criterion is involved in the final judgment, which overcomes the defect of the fixed threshold in adaptability and improves the detection performance to a greater degree. Simulation results show that compared with the traditional feature-based Speech Endpoint Detection methods, the accuracy of the proposed method has a high accuracy rate, which proves that the new method has a better robust performance in a low SNR and nonstationary noise.

    New fuzzy SVM model used in imbalanced datasets
    CAI Yanyan;SONG Xiaodong
    J4. 2015, 42(5):  120-124+160.  doi:10.3969/j.issn.1001-2400.2015.05.021
    Abstract ( 423 )   PDF (461KB) ( 615 )   Save
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    The paper proposes a new fuzzy SVM, called CI-FSVM(Class Imbalance Fuzzy Support Vector Machine) short for which is based on imbalanced datasets classification. By improving penalty functions, we reduce the sensitivity of the model for imbalanced datasets with “overlap”. In addition, the parameters in SVM models are optimized by the grid-parameter-search algorithm. The results show that the CI-FSVM has a better effect in imbalanced datasets classification compared with other models. It not only has a higher overall accuracy, but also improves are judgment accuracy when dealing with the minority classifications.

    Novel per-flow traffic measurement algorithm
    REN Gaoming;XIA Jingbo;BAI Jun;CHEN Zhen
    J4. 2015, 42(5):  125-132.  doi:10.3969/j.issn.1001-2400.2015.05.022
    Abstract ( 432 )   PDF (792KB) ( 328 )   Save
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    It is extremely difficult to measure traffic information with a growing network link speed. In recent years, increasing focus has been put on probabilistic algorithms which are fast enough to examine all packets and can provide estimates of the sizes of all flows. However, the previously proposed flow estimating algorithm of PMC has the drawbacks of poor space efficiency and large estimation error. To address the problem, a double bit field (D-BF) algorithm is proposed. The method is divided into two steps: the newly arrived packet is mapped to two bit fields using different hash functions in the data capturing stage; two virtual matrixes recovered from the bit fields have been intersected to eliminate errors caused by the hash collision in the data recovering stage. Experimental results show that the proposed D-BF is more accurate than PMC in flow estimate, while a reduction of 75% in memory space can be achieved.

    Blind steganalysis algorithm based new calibration for JPEG images
    ZHANG Minqing;ZHANG Yan;LI Delong;LUO Peng
    J4. 2015, 42(5):  133-138.  doi:10.3969/j.issn.1001-2400.2015.05.023
    Abstract ( 501 )   PDF (810KB) ( 386 )   Save
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    To improve the embedding sensibility of calibrated feature in steganalysis, by studying the relationship between calibration technique and feature, a mathematical model for calibration based on the calibration classification is established, and a blind JPEG steganalysis algorithm based on the new calibration is presented. First we crop 4 pixels in the image and put forward a modified form of calibration, then the histogram characteristic is obtained according to the spatial distribution of the image features before and after calibration, and the Markov transfer probability matrix of the new calibration is calculated on the basis of redundancy. Finally, we fuse these features with the blocks feature and obtain the feature vector.Through the detection experiment of nsF5, Jsteg and MB1 algorithms with low embedding rates and among the feature vector, it is shown that this method has a better detection performance compared with those existing calibration methods. Its correctrate is more than 90%. The feature sets also show some complementary characteristics. It can be more stable and reliable in the different quality factors experiment.

    Iterative equalization combining algorithm in intersymbol interference channel
    QIAO Liang;ZHENG Hui
    J4. 2015, 42(5):  139-146.  doi:10.3969/j.issn.1001-2400.2015.05.024
    Abstract ( 381 )   PDF (668KB) ( 381 )   Save
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    To realize joint optimization of spatial diversity and equalization combining in the intersymbol interference (ISI) channel, an iterative equalization combining algorithm is proposed. The proposed algorithm uses the coefficients of Turbo equalization to calculate the combination weights without estimating the signal to noise ratio in each diversity branch. The equalized symbols from different diversity branches are combined, and the extrinsic information output from the decoder is fed back to the equalizers, so as to exchange soft information between the equalizers and the decoder. The performance of the proposed algorithm is analyzed using the extrinsic information transfer (EXIT) chart and verified by simulations. Results show that our approach fully exploits time domain information from the multipath channel and spatial domain information from multi receiving antennas, which efficiently improve the performance of the receiver in the severe ISI channel.

    On the short-term regional prediction of foF2 based on the support vector machine
    LI Meiling;HU Yaogai;ZHOU Chen;ZHAO Zhengyu;ZHANG Yuannong;LIU Jing;DENG Z X
    J4. 2015, 42(5):  147-153+206.  doi:10.3969/j.issn.1001-2400.2015.05.025
    Abstract ( 589 )   PDF (1441KB) ( 457 )   Save
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    Ionospheric short-term forecasting is very important to radio communication, navigation and radar systems. In this paper, in order to improve the regional prediction accuracy of ionosphere, a model of regional prediction of the ionospheric F2 layer critical frequency in China area 1 hour in advance is set up based on the support vector machine (Support Vector Machine, referred to as SVM for short) method. In this model, the influence of solar activity, geomagnetic activity, the upper atmosphere, geographical location and other factors on the ionosphere is taken into consideration. Results of this model is compared to Back-Propagation referred to as BP for short the neural network of the same input parameters and the IRI model (International Reference Ionosphere, referred to as IRI for short). The results show that the average relative error of annual prediction of SVM in high solar activity years decreases by 2.5% and 9.6%, respectively, compared with the neural network and the IRI models and in low solar activity  decreases by 1.8% and 7.5%, respectively. In the low latitude area, the prediction of SVM has more significant advantages over the BP neural network. In the high and low solar activity years it decreases by 3.2% and 2.7%, respectively. During the storm time SVM also shows a relatively good prediction ability. This proves that the developed model based on SVM in the paper has more advantages over the BP neural network and IRI model.

    Anisotropic diffusion denoising method based on image feature enhancement
    MA Hongjin;NIE Yufeng
    J4. 2015, 42(5):  154-160.  doi:10.3969/j.issn.1001-2400.2015.05.026
    Abstract ( 825 )   PDF (5113KB) ( 489 )   Save
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    This paper presents an image feature enhancement diffusion model. Since the coherence-enhancing anisotropic diffusion model, proposed by J.Weickert, often induces false edges in slippy regions and can not preserve the detail features effectively, the new model poses two characteristic indexes and one gradient variance index to finely describe much more image information than the previous work, such as corners and isolated noises except with slippy regions and edges, and defines eigenvalues based on the classification results such that the new diffusion tensor has large eigenvalues along both the gradient direction and edge direction in the slippy regions and at isolated noises, but has small eigenvalues along the two directions at corners, and has small eigenvalue along the gradient direction and large eigenvalue along the edge direction at edges. So it can remove noises efficiently and at the same time enhance edges and detail features. Theoretical analysis and numerical experiments show the effectiveness of the proposed model.

    Power allocation under GSVD linear precoding in the MIMO two-way relay network
    LIU Sheng'en;XIAO Lin;YANG Dingcheng;TAN Anping
    J4. 2015, 42(5):  161-167.  doi:10.3969/j.issn.1001-2400.2015.05.027
    Abstract ( 560 )   PDF (560KB) ( 508 )   Save
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    In order to optimize the power allocation of the MIMO two-way relay system, we diagonalize the channels between users and relay using the generalized singular value decomposition(GSVD) method, and divide them into two transmission models: one-way relay model and two-way relay model. For the subchannels, a scheme of permutation is proposed to align the data streams at the relay node. Moreover, we propose the method for the power constraint of three nodes under each data stream to maximize the average sum-rate of the system instead of the constraint of each node's total power and get the close-form optimal solution which can reduce the complexity of the algorithm. Finally, simulation results demonstrate that the performance of the scheme we use is very close to that by the global optimization algorithm, and that with the antennas specification from 3-5-3 to 4-6-4 and to 5-7-5, the scheme can bring about approximate 2bit/(s·Hz<sup>-1</sup>) increased gain when the SNR is 30dB.

    Real-time visual object tracking based on binary descriptors
    QIN Bing;TIAN Jun;ZHA Yufei;ZHANG Lichao;HUANG Hongtu
    J4. 2015, 42(5):  168-174.  doi:10.3969/j.issn.1001-2400.2015.05.028
    Abstract ( 471 )   PDF (3407KB) ( 360 )   Save
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    Object tracking often has the problems of low rate and high storage. Therefore, a tracking algorithm based on binary descriptors is proposed. The algorithm retains the original construction information on the samples and projects the samples from Euclidean space to Hamming space in order to generate binary descriptors by searching the optimal orthogonal matrix for rotating cluster. Then under the frame of particle filtering, it is necessary to determine the tracking position by computing the hamming distance.Analysis and experiment show that the proposed tracking algorithm performs rapidly and favorably when the target objects undergo large illumination,pose changes and fast movement.

    Visual object tracking with the adaptive scale based on AGMM point sets matching
    ZHANG Lichao;BI Duyan;YANG Yuan;YU Wangsheng;QIN Bing
    J4. 2015, 42(5):  175-182.  doi:10.3969/j.issn.1001-2400.2015.05.029
    Abstract ( 562 )   PDF (4823KB) ( 323 )   Save
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    A visual object tracking method with the adaptive scale based on AGMM(Asymmetrical Gauss Mixture Models) point sets matching is proposed aimed at adaptively following the object's scale changes, which often cause tracking failure. As the feature point set in the last frame is considered as the GMM centroids and the feature point set in the current frame represents the data respectively, AGMM fuses the feature information and spatial information; by comparing the similarity between data and GMM centroids, we match the point sets between two adjacent frames and obtain the reliable feature points in the current frame; the degree of dispersion between points in the point set accurately reflects the size of the object scale and by using affine transformation, the proportion of the two point sets is computed to estimate the position and scale of the bounding box in the current frame accurately and effectively. Experimental results demonstrate that the method is adaptive to scale change and has advantage in illumination variation and color similar target tracking.

    Optimal linear constraint transformation method for α-nets
    ZHANG Li;ZHAO Liangxu;WANG Shouguang;WANG Chengying
    J4. 2015, 42(5):  183-187+212.  doi:10.3969/j.issn.1001-2400.2015.05.030
    Abstract ( 417 )   PDF (421KB) ( 319 )   Save
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    For a class of Petri nets whose uncontrollable subnets are α-nets, this paper proposes a method to transform a given generalized mutual exclusion constraint into an optimal admissible one. Firstly, the uncontrollable subnets are obtained. Secondly, an algorithm for synthesizing the transformed sets of forbidden places is proposed. Lastly, according to the sets of forbidden places, the disjunction of admissible linear constraints which is maximally permissive is constructed. An example is provided to illustrate the efficiency of the proposed method.

    Low complexity method for PAPR reduction of OFDM signals
    WEN Honghang;GE Jianhua;XU Tangwen
    J4. 2015, 42(5):  188-193.  doi:10.3969/j.issn.1001-2400.2015.05.031
    Abstract ( 457 )   PDF (612KB) ( 445 )   Save
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    Partial transmit sequences (PTS) search complexity increases exponentially with the number of subblocks. To solve this problem, a novel immune quantum evolutionary PTS scheme is proposed to reduce computational complexity and improve PAPR performance. In this scheme, a Q-gate is introduced to drive the individuals toward better solutions, the evolutionary mechanism restrains degeneracy and increases the fitness of population, and a specially hexagonal constellation is used to eliminate side information. Simulation results indicate that the conventional PTS is more complicated than the proposed strategy, and that the proposal shows better performance without additional transmit sideband information than similar other solutions.

    Connectivity compression of triangle meshes based on geometric parameter predict
    WEI Xiaoran;GENG Guohua;ZHANG Yuhe
    J4. 2015, 42(5):  194-199.  doi:10.3969/j.issn.1001-2400.2015.05.032
    Abstract ( 464 )   PDF (1390KB) ( 436 )   Save
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    An efficient encoding algorithm for lossless compression of triangle mesh connectivity is presented to further optimize the compression ratio. The algorithm firstly cuts a given mesh into a cutaway graph, then uses a triangle nodes tree to present the graph, containing the triangle strips topology information on the graph in the adjacency relationships between the leaf nodes and the branch nodes, reducing the mesh topology information needed to be encoded. Finally, we use the minimum interior angle maximum principle to predict the internal topology of the triangle strips, only encoding the prediction error elements, thus further reducing the information needed to be encoded. Compared with the current compression algorithms, this algorithm does not traverse the triangular mesh, only encoding and storing a small amount of mesh topology information and prediction information. Experimental results show that the algorithm can greatly reduce the compression ratios and process various triangle meshes.

    Micro-motion feature analysis and parameter estimation methods for moving ship
    YANG Qiu;ZHANG Qun;WU Yong;LUO Ying;WANG Min
    J4. 2015, 42(5):  200-206.  doi:10.3969/j.issn.1001-2400.2015.05.033
    Abstract ( 434 )   PDF (1183KB) ( 363 )   Save
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    Micro-motion parameter estimation is an important way to improve ability of radar to detect the ship target. Focusing on the difficulty and speed problems existing in the current parameter estimation method of a complex moving ship, based on the analytical result of the echo's time-frequency features, a novel method to estimate the micro-motion period by calculating the backward shift cross-correlation coefficients of the echo's sparse time-frequency matrix is proposed in this paper. Firstly, the backward shift cross-correlation coefficients of the echo's sparse time-frequency matrix are calculated using the FFT (fast Fourier transform) algorithm. The peaks positions of the cross-correlation coefficients matrix are then detected. Finally, the period can be figured out quickly. Compared with the general method, the proposed method can estimate the micro-motion period accurately and quickly. A computer simulation is given to illustrate the effectiveness of the proposed method.

    Disturbance rejection SDRE attitude control
    ZHANG Yinhui;YANG Huabo;JIANG Zhenyu;ZHANG Weihua
    J4. 2015, 42(5):  207-212.  doi:10.3969/j.issn.1001-2400.2015.05.034
    Abstract ( 476 )   PDF (654KB) ( 373 )   Save
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    The nonlinear disturbance observer based disturbance rejection SDRE attitude control is investigated for a general nonlinear missile with parameter uncertainties and external disturbances. Firstly, the total effects of the parameter uncertainties and external disturbances are regarded as the lumped disturbances. And then, a disturbance compensation gain is carefully designed, so that the disturbance rejection SDRE attitude control method is able to address the mismatched disturbances. Finally, the nonlinear disturbance observer is introduced to estimate the lumped disturbances. Simulation results have demonstrated the precise tracking performance and the disturbance rejection capability of the proposed method with respect to the parameter uncertainties and external disturbances.