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    20 April 2016 Volume 43 Issue 2
      
    Support driven recovery algorithm for non-convex compressed sensing
    WANG Feng;XIANG Xin;YI Kechu;XIONG Lei
    Journal of Xidian University. 2016, 43(2):  1-5+28.  doi:10.3969/j.issn.1001-2400.2016.02.001
    Abstract ( 295 )   PDF (915KB) ( 311 )   Save
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    A novel method is presented for the purpose of recovering sparse high dimensional signals from few linear measurements, especially in the noisy case. The proposed method works in the following two steps: ①The support of signal is approximately identified via Thresholded Basis Pursuit(TBP), the weighting matrix and parameters needed for the next step are also computed; ②The Iteratively Reweighted Lp Minimization(IRLp) procedure is used to solve the non-convex objective function. As theoretic interpretation and simulation results show, lower computational complexity is required for the proposed Support Driven IRLp(SD_IRLp) algorithm for high probability recovery, in comparison to 7 analogous methods(including an oracle estimator).

    Resource allocation scheme for video transmissions in cognitive radio networks
    LONG Yan;LI Hongyan
    Journal of Xidian University. 2016, 43(2):  6-12.  doi:10.3969/j.issn.1001-2400.2016.02.002
    Abstract ( 309 )   PDF (729KB) ( 223 )   Save
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    Considering SUs with multiple radios, this paper discusses the cross-layer resource allocation problem for video transmissions in cognitive radio networks. Because of the coupling relationship between radio and channel, this paper proposes a new conflict graph based on the link-radio-channel, and models the resource allocation problem into an optimization problem. The constraints ensure the conflict-free and interference-free video transmissions, and provide flow routing and rate allocation for video services based on the feature of scalable video coding streams. The objective function achieves the network-level throughput maximization with fairness consideration. Simulation results show that the multi-radio transmission could gain a higher throughput. Also, the proposed scheme could provide fairness resource allocation, and use resource efficiently based on the feature of video services.

    Distributed opportunistic channel access strategy in DF relay networks
    DONG Lei;WANG Yongchao
    Journal of Xidian University. 2016, 43(2):  13-16+131.  doi:10.3969/j.issn.1001-2400.2016.02.003
    Abstract ( 258 )   PDF (422KB) ( 195 )   Save
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    Considering the two limitations of scenario assumption and performance optimization in distributed opportunistic channel access under the continuous transmission rate, a distributed opportunistic channel access strategy is proposed in DF relay networks under the discrete transmission rate. The proposed strategy maximizes the system average throughput with the instruction of optimal stopping theory. By optimizing the second-hop transmission time in DF relay networks completely, the total transmission time is reduced, and the system performance is improved. Compared with the current strategy, simulation result demonstrates the validity of the proposed strategy in system average throughput.

    Resource reusing selection scheme for device-to-device communication underlaying LTE-A networks
    ZHANG Rui;LI Yongzhao;CUI Jianguo;LIANG Haitao;WANG Wenhuan
    Journal of Xidian University. 2016, 43(2):  17-22.  doi:10.3969/j.issn.1001-2400.2016.02.004
    Abstract ( 256 )   PDF (670KB) ( 292 )   Save
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    Device-to-Device (D2D) communication underlaying LTE-A cellular networks is effective to improving spectral efficiency and offload traffic of the base station by reusing cellular resources. However, the mutual interference between D2D and cellular communications can degrade the performance of both D2D and cellular users. In this paper, a resource reusing selection scheme based on minimizing power increase is proposed, which enables selective compensation for signal to interference plus noise ratio (SINR) diminution caused by interference. Simulation results demonstrate that the proposed scheme notably improves the access grant probability of D2D users and increases the link spectral efficiency of D2D and cellular networks, without sacrificing the quality of cellular and D2D communication.

    Radar HRRP target recognition by utilizing multitask sparse learning with a small training data size
    XU Danlei;DU Lan;WANG Penghui;LIU Hongwei
    Journal of Xidian University. 2016, 43(2):  23-28.  doi:10.3969/j.issn.1001-2400.2016.02.005
    Abstract ( 294 )   PDF (638KB) ( 350 )   Save
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    A statistical modeling method based on multitask sparse learning is proposed to realize the recognition of the high resolution range profile (HRRP) with a small training data size. The statistical modeling of each training aspect-frame is considered as a single task in our method. Since the training aspect-frames are not independent but inter-related, they can share a compact dictionary to make full use of the information. However, with the different targets and the aspect sensitivity of the same target, it is usually hard to assess the task relatedness, and joint learning with unrelated tasks may degrade the recognition performance. Therefore, we adopt the Bernoulli-Beta prior to learn the needed atoms of each aspect-frame automatically with the given training data. Then the relatedness between frames is determined by the number of shared atoms, and multitask learning can be realized adaptively. The recognition experiments of the measured HRRP data demonstrate the performance of the proposed method.

    Push-broom spectral imaging method based upon multi-slit
    LIN Yaohai;SHI Guangming;WANG Lizhi;GAO Dahua
    Journal of Xidian University. 2016, 43(2):  29-34.  doi:10.3969/j.issn.1001-2400.2016.02.006
    Abstract ( 428 )   PDF (3156KB) ( 189 )   Save
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    The acquisition of high image quality and high resolution spectral data is limited by light flux. A push-broom spectral imaging should reduce the spatial resolution if it amplified its light flux to increase its signal noise ratio (SNR). According to this problem, the theory of compressive sensing (CS) is introduced for modeling the push-broom spectral imaging system from the signal processing analysis, so that the number of slits of the imaging system can be increased to amplify its light flux. Under the guidance of the theory of compressive sensing, the light flux can increase without reducing the spatial resolution. In the simulation, if its exposure frequency dropped to 1/4  the original, and its light flux increased to 128 times the original, the spectral image with the resolution of 512×512 could be well obtained. This method is suitable for remote sensing by using a smaller number of times for imaging and less memory for storage and transmission compared with the traditional one.

    Highly efficient VLSI architecture for DWT with low-storage implementation
    DONG Mingyan;LEI Jie;WANG Keyan;LI Yunsong
    Journal of Xidian University. 2016, 43(2):  35-40.  doi:10.3969/j.issn.1001-2400.2016.02.007
    Abstract ( 247 )   PDF (654KB) ( 275 )   Save
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    With the gradual increase in image resolution of the spacecraft camera, it is highly required to figure out the problem how to process a huge amount of image data on board at a high speed. As a solution, the CCSDS proposes a space-oriented image-coding standard. For the sake of high image-coding performance, it adopts wavelet transformation as a method of image data transformation. However, wavelet transformation contains multi-level data processing, which causes more computational time consumption and more memory utilization. In order to solve this problem, we propose a highly efficient VLSI architecture for DWT with low-storage. By revising the traditional lifting structure and employing time-multiplex data processing strategy to perform the second and third level of wavelet transformation by the same logic module, the usage of logic resource is reduced with no sacrifice on speed.Using a small amount of on-chip memory instead of off-chip memory to save certain parts of DWT coefficients and sending the coefficients in a specific sequence to entropy coder timely, the off-chip memory for storage of DWT coefficients is no longer required. The proposed VLSI architecture of DWT is already implemented on the Xilinx FPGA XC4VSX55, which can achieve a high performance, in terms of data throughput, reaching 95.91MPixels/s.

    Novel robust beamforming algorithm using sequential quadratic programming
    YU Hongbo;FENG Dazheng;XIE Hu
    Journal of Xidian University. 2016, 43(2):  41-45+204.  doi:10.3969/j.issn.1001-2400.2016.02.008
    Abstract ( 288 )   PDF (535KB) ( 315 )   Save
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    Aiming at the probably existing performance loss and high computational complexity of the robust beamforming based on steering vector estimation with as little prior information as possible which is solved by the semi-definite relaxation (SDR) approach, a novel robust beamforming algorithm using sequential quadratic programming (SQP) is proposed. The original non-convex problem is linearly approximated to a convex subproblem using the first order Taylor's series, and the optimal solution is found out by solving the convex subproblem iteratively. Moreover, considering the mismatch of the sample covariance matrix, the SQP-WC method based on worst-case performance optimization is presented to improve the performance of the proposed SQP method. Theoretical analysis and simulation results show that the proposed SQP algorithm can converge fast and its convergence point approximates the optimal solution to the original problem, which indicates that the SQP method can effectively reduce the computational complexity compared with the SDR method, and furthermore, the SQP-WC method can effectively improve the performance of the SQP method with a small parameter.

    Adaptive waveform design for target detection in the wideband radar system
    WU Xuzi;LIU Zheng;XIE Rong
    Journal of Xidian University. 2016, 43(2):  46-51.  doi:10.3969/j.issn.1001-2400.2016.02.009
    Abstract ( 320 )   PDF (579KB) ( 226 )   Save
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    The target detection performance of radar can be improved by transmitting a waveform which matches the high-resolution range profile (HRRP) of the target. However, a serious degradation of the autocorrelation property always occurs in the matched waveform, which has a bad effect on radar parameter estimation. To solve this problem, a generalized model of HRRP which consists of the deterministic term and random term is introduced under the consideration of variations in the target impulse response. Based on the study of the generalized likelihood ratio test (GLRT) detector and the objective functions for waveform design, an iterative algorithm with the criteria of maximizing the signal to noise ratio (SNR) and minimizing the minimum mean square error (MMSE) is proposed. Simulation results indicate that the design method can make a tradeoff between the performances of estimation and detection, and sequentially improve the detection performance based on the on-line estimates of the HRRP.

    Blind extraction of the weak cyclostationary echo signal
    ZHU Yun;WANG Jun;ZHANG Gege;WANG Xiangru
    Journal of Xidian University. 2016, 43(2):  52-57.  doi:10.3969/j.issn.1001-2400.2016.02.010
    Abstract ( 276 )   PDF (727KB) ( 172 )   Save
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    To extract the weak echo signal buried in a strong direct signal, multipath signal, interfering signal and noise in passive radar systems, a new method is proposed based on cyclostationarity. The desired signal can be directly extracted from the echo channel without the reference channel based on the spectral line generating characteristics. Then, the component of the desired signal is maximized in an iterative way, while other signals and noise are minimized. Compared with the traditional methods, the proposed algorithm does not need the reference channel, which can simplify the structure of the receiver, and what's more, the computational burden is decreased. Simulation results verify the effectiveness of the proposed method.

    DOA estimation method based on the covariance matrix sparse representation
    ZHAO Yonghong;ZHANG Linrang;LIU Nan;XIE Hu
    Journal of Xidian University. 2016, 43(2):  58-63+101.  doi:10.3969/j.issn.1001-2400.2016.02.011
    Abstract ( 318 )   PDF (643KB) ( 272 )   Save
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    The performance of the L<sub>1</sub>-norm-based sparse representation of array covariance vectors(L<sub>1</sub>-SRACV) algorithm significantly degrades with the number of samples decreasing. This paper analyzes the essential cause of this performance degradation and proposes a new direction of arrival(DOA) estimation method based on the fast maximum likelihood(FML) algorithm. Firstly, the FML algorithm is employed to estimate the covariance matrix, which attenuates the instability of the small eigenvalues of the covariance matrix. Then the sparse representation model based on the FML is formulated for DOA estimation and finally, optimized by removing the diagonal elements of the covariance matrix to obtain better performance. Simulation results indicate that our method outperforms the L<sub>1</sub>-SRACV with a higher accuracy and detection possibility, particularly under small samples support.

    Local coordinate gradient descriptor based on cyclic division
    LI Jianbing;XIAO Xiao;LI Xiaoping;HOU Xiaoli
    Journal of Xidian University. 2016, 43(2):  64-69.  doi:10.3969/j.issn.1001-2400.2016.02.012
    Abstract ( 218 )   PDF (2562KB) ( 243 )   Save
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    A novel regional image feature description method is proposed to improve the affine invariant and matching performance of image feature descriptors. Firstly, the Hessian-affine detector is adopted to extract the image feature region,which is normalized to the unit circular feature region to meet the affine invariant requirement. Secondly, in order to avoid the error caused by calculating main gradient orientation on the histogram, the annular-based region division is proposed on the local coordinate system of the image sample point to calculate the local gradient orientation. Experimental results demonstrate that the new method not only has an excellent affine invariant,but also is significantly better than the SIFT descriptor in match performance.

    Fairness-guaranteed reputation propagation in Web service composition
    ZHANG Tao;MA Jianfeng;MO Ruo;LI Qi;XI Ning
    Journal of Xidian University. 2016, 43(2):  70-76.  doi:10.3969/j.issn.1001-2400.2016.02.013
    Abstract ( 256 )   PDF (508KB) ( 240 )   Save
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    In service-oriented environment, it is difficult to evaluate component services because of the opaque characteristic of composite services, the complex invocation structures and the subjective reputation rating of service consumers. To address these issues, this paper proposes a reputation propagation algorithm for service composition, in which the subjective ratings can be fairly propagated to each component service. The algorithm first models service composition as the Beta-mixture, and learns the reputation and responsibility of each component by the EM algorithm. Then, based on the characteristics of Shapley values in cooperative gaming theory, the algorithm computes the contribution of each component to its composition, ensuring that no component would obtain extra rewards or punishments. Finally, theoretical analysis and experimental results demonstrate the fairness of the algorithm to hieratically propagate the consumer's rating to each component service.

    Experiment on reproducing the continuous blackout of the GPS system
    GAO Ping;LI Xiaoping;XIE Kai
    Journal of Xidian University. 2016, 43(2):  77-82.  doi:10.3969/j.issn.1001-2400.2016.02.014
    Abstract ( 277 )   PDF (1137KB) ( 367 )   Save
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    The plasma induced in the reentry can degrade the electromagnetic system, even producing the blackout when it is serious. Then the attenuation of the GPS signal by the plasma is calculated and the power threshold of the received signal is analyzed. An experiment on the continuous ‘acquisition-blackout-reacquisition’ process of GPS system is successfully reproduced by plasma in an ordinary lab. The plasma is excited by a low-pressure glow discharge and it is a long-lasting, large-scale, non-magnetic plasma. The plasma density can be easily controlled by RF power, achieving an arbitrary variation of plasma density. Comparing the critical attention with the standard power threshold of the receiver, results indicate that both the values are almost the same and that their differences are less than 0.5dB. The blackout occurs as the attenuation is greater than the threshold. The experiment is valuable for the research on other navigation systems' blackout and the design of reentry receivers.

    Multiple DAGs dynamic workflow reliability scheduling algorithm in a cloud computing system
    JING Weipeng;WU Zhibo;LIU Hongwei;SHU Yanjun
    Journal of Xidian University. 2016, 43(2):  83-88.  doi:10.3969/j.issn.1001-2400.2016.02.015
    Abstract ( 242 )   PDF (565KB) ( 266 )   Save
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    In order to solve the reliable scientific workflow scheduling problem for cloud computing, a dynamic of the RANK-Hierarchical algorithm is put forward which takes account of communication contention as well as supports task dependencies(CCRH). A communication contention model is first defined, as soon as the earliest completion of the primary and backup task is deduced. Besides, the executived processor is limited. We use the dynamic hierarchical method and calculate each DAG unfair degree factor for multiple DAGs scientific workflow. It can deal with the situation that multiple DAGs workflow comes at different times and there are various kinds of structure. Both the theory and experiments have proved that the algorithm can not only improve the scheduling fairness of multiple DAGs workflow but also shorten the average execution Makespan.

    Novel SAR target detection algorithm via multiple features
    ZENG Lina;ZHOU Deyun;XING Mengdao;ZHANG Kun
    Journal of Xidian University. 2016, 43(2):  89-94.  doi:10.3969/j.issn.1001-2400.2016.02.016
    Abstract ( 241 )   PDF (4112KB) ( 164 )   Save
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    A detection method for SAR targets based on combining multiple features is proposed. The targets of interest are detected according to the physical properties, which reflect the true characteristics including scattering intensity, size and differences from the clutter. By analyzing these characteristics, the size and boundary changes are determined as effective features. The image background, natural clutter, man-made clutter are eliminated in sequence using the developed detection algorithm, which contains two layers, namely, the initial target detection layer and the potential target identification layer. Effective features ensure that a smaller number of features are used to meet the precision of the target detection, and the discrimination detection method ensure that the probability of false alarm is reduced gradually with the increased complexity of the feature extraction. Comparison with traditional target detectors, such as CFAR, PCA, etc. is performed in detail. Experimental results show the superiorities of the proposal in both accuracy and efficiency.

    Design of and experiment on the polarization dehazing imaging system
    XIA Pu;LIU Xuebin;YAN Peng
    Journal of Xidian University. 2016, 43(2):  95-101.  doi:10.3969/j.issn.1001-2400.2016.02.017
    Abstract ( 640 )   PDF (2426KB) ( 280 )   Save
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    In view of the requirement of image quality, integration level and real-time application of the imaging systems under fog weather, this paper reports a polarization imaging system with a dehazing ability. The differential signal is converted by FPGA, and a highly integrated CMOS imaging circuit is built based on the internal PLL of the image sensor and the CamLink protocol. The obtained image is inversed by stokes equations, and the real-time dehazing algorithm is realized by the built-in DSP module. The total size of the polarization imaging system is 117mm×117mm×126mm, and the weight of the system is 1.2kg. An imaging experiment was made under fog weather, and the dehazing ability of the imaging system is proved by the contrast of the original image and the dehazed image's histogram and RGB distribution. Experimental results show that the imaging system can stably obtain a color dehazed image at 2048×2048@180Hz.

    Regularized discriminative segmental feature transform method
    CHEN Bin;ZHANG Lianhai;QU Dan;LI Bicheng
    Journal of Xidian University. 2016, 43(2):  102-107.  doi:10.3969/j.issn.1001-2400.2016.02.018
    Abstract ( 255 )   PDF (486KB) ( 406 )   Save
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    In order to improve the stability of the frame based feature transform method, a segment based discriminative feature transform method is proposed, and the feature transform matrix of each speech segment is determined using the regularization technique. In the novel method, the feature transform is viewed as a parameter selection problem with limited data. In the training stage, an over-complete dictionary is constructed by the feature transform matrices of tied-state based region dependent linear transform. During testing, after the speech signal is segmented through force alignment, an appropriate regularization term is added to the likelihood objective function. An optimal subset of the transform matrices is selected from the dictionary and their corresponding coefficients are estimated following the fast iterative shrinkage thresholding optimization algorithm. Experimental results show that compared with the tied-state RDLT method, after combining L<sub>1</sub> and L<sub>2</sub> regularization, the recognition rate is increased by 1.30% using the maximum likelihood training criterion. The performance gain is increased to 1.66% after discriminative training.

    Method for detecting optimal distribution of RFID multiple tags based on Fisher matrix
    YU Yinshan;YU Xiaolei;LIU Jialing;ZHAO Zhimin;WANG Donghua
    Journal of Xidian University. 2016, 43(2):  108-113.  doi:10.3969/j.issn.1001-2400.2016.02.019
    Abstract ( 271 )   PDF (2476KB) ( 184 )   Save
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    Dynamic performance parameters of multiple tags in the RFID system includes reading efficiency, reading distance and so on. The improvement of existing algorithms for the reading performance of multiple tags is limited in the RFID system, so the geometric distribution of tags is arranged reasonably to improve the performance in this paper. In the Fisher matrix of evaluation, we calculate the extremum of the azimuth matrix and obtain the optimal geometric distribution of tags. Then the geometric distribution of multiple tags and the reading performance of the RFID system are evaluated in numerical simulation. Taking the reading distance as the dynamic performance parameter, we design the tray-level RFID application system and test the optimal geometric distribution of multiple tags in simulative dynamic environment. The results show that the optimal geometric distribution of tags, which is obtained by calculating the Fisher matrix, could improve the dynamic performance and reduce the reading error of multiple tags in the RFID system effectively.

    Improved steering based on the virtual extend method for the microphone array
    YANG Jie;LIU Congfeng;CAI Xiao
    Journal of Xidian University. 2016, 43(2):  114-119.  doi:10.3969/j.issn.1001-2400.2016.02.020
    Abstract ( 274 )   PDF (820KB) ( 299 )   Save
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    For the broadband microphone array, how to maintain the consistency of optimal array processing in the whole frequency band is the key problem, so an efficient virtual array extending method is put forward. This method is not only suitable for the single source scenarios, but also suitable for the multi signal source scene. Therein, from the signal model and the theoretical derivation, the problem which is caused by array virtual extending is analyzed deeply, such as array error and difficulty of its realization, then a robust method based on diagonal loading is proposed, and the method of how to select the load level is also given. Finally, the processing performance of the proposed virtual array extension method is tested and verified by theoretical analysis and detailed simulation results, and the conclusion is obtained that virtual array extension can improve the adaptive beamformer performance effectively. The proposed method is not only used for the uniform linear array, but also can be applied to the adaptive array with an arbitrary configuration.

    Non-convex hybrid total variation method for image blind restoration
    LIU Qiaohong;LI Bin;LIN Min
    Journal of Xidian University. 2016, 43(2):  120-125.  doi:10.3969/j.issn.1001-2400.2016.02.021
    Abstract ( 261 )   PDF (3677KB) ( 384 )   Save
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    A multi-regularization constraint method for imageblind restoration is proposed to recover the blurry-noisy images.First, the non-convex total variation is adoptedas the regularization constraint by taking the sparse edges in the natural image into consideration. Next, the high-order total variation is used to overcome the staircase effects in the smooth regions of the image. Then a non-convex minimization model is proposed. Finally, the augmented Lagrangian method and a new generalized p shrinkage operator are applied to solve the model. The results of numerical experiments show that the proposed method can preserve the image edges while removing the staircase effects effectively. The high quality restored image can be obtained.

    Intrusion detection design of the impoved immune algorithm
    WEI Mingjun;WANG Yueyue;JIN Jianguo
    Journal of Xidian University. 2016, 43(2):  126-131.  doi:10.3969/j.issn.1001-2400.2016.02.022
    Abstract ( 321 )   PDF (512KB) ( 319 )   Save
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    In order to improve the detection efficiency of intrusion detection and reduce the rate of misstatement, on the basis of the multi-colony immune algorithm and clonal selection algorithm, the multi-colony clonal selection algorithm is put forward, the matching rule is improved and the 10% sampling data of KDDCUP99 data set is adopted as the test data of the simulation test. Each record has 41 fixed properties. Nine attributes based on the basic features of a single TCP connection are selected for study. According to the characteristics of the data set, in combination with the multi-colony clonal selection algorithm, four types of attack data which are encoded and de-weighed are regarded as the initial populations of multi-colony clonal selection algorithm for immune operation. Then, the optimal group is output. Based on the principle that normal data is greater than abnormal data, the test data set need to be filtered by the self-data set. The filtered data match the optimal group. Experimental results show that abnormal data can be effectively identified. Through comparison and analysis, the multi-colony clonal selection algorithm and the improved matching rule can improve the detection rate of intrusion detection.

    MIMO radar waveform design method via low sidelobe beampattern modification
    LI Yirong;HU Hanying
    Journal of Xidian University. 2016, 43(2):  132-138.  doi:10.3969/j.issn.1001-2400.2016.02.023
    Abstract ( 309 )   PDF (649KB) ( 250 )   Save
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    In the design of the multiple-input multiple-output(MIMO) radar waveform, decreasing transmit beampattern sidelobes could reduce the energy of clutters and false targets from sidelobes and increase the received signal to noise ratio (SNR) so as to improve the angle estimation property. Motivated by this idea, a transmit waveform design method based on low sidelobe beampattern modification is proposed for MIMO radar. First, the transmit waveform cross-correlation matrix can be obtained by the semidefinite relaxation (SDR) technique. Then the essence of our method is to establish an optimization modification model to reduce the beampattern sidelobe by changing the non-diagonal elements of the waveform cross-correlation matrix. Finally, the corresponding transmit beamforming weight matrix is obtained by this modified matrix, and the ESPRIT algorithm is used for the direction of arrival (DOA) estimation. Meanwhile, the feasibility of our method is demonstrated. Simulation results show the superiorities of our method in sidelobe suppression, DOA estimation accuracy and angle resolution.

    Traffic violation detection based on the implicit curves family
    MA Liwen;GUO Yukun;LI Jinping
    Journal of Xidian University. 2016, 43(2):  139-144.  doi:10.3969/j.issn.1001-2400.2016.02.024
    Abstract ( 230 )   PDF (2824KB) ( 172 )   Save
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    We propose an effective algorithm for the detection of the traffic violation vehicle by employing a set of implicit function curves which can be used to describe the different regions on the roads. When the vehicles are detected to run across different road regions, we can determine in which region that vehicle lies easily and immediately by using the set of implicit functions. According to the vehicle trajectory and the relationship among different regions described by the implicit functions, we can quickly and accurately determine whether the vehicle violates the traffic rules. In order to improve the detection efficiency and accuracy greatly, we use the piecewise linear functions to approximate the set of implicit functions in actual detection. Experimental results show that our algorithm can detect the traffic violation and display the specific violated traffic rules in real time.

    Indoor positioning algorithm based on Markov Monte Carlo
    WANG Yue;BA Bin;CUI Weijia;LU Zhiyu
    Journal of Xidian University. 2016, 43(2):  145-149.  doi:10.3969/j.issn.1001-2400.2016.02.025
    Abstract ( 294 )   PDF (665KB) ( 361 )   Save
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    The interference in the received power leads to the problem of the low estimation accuracy of WLAN indoor positioning, so a new method is proposed which constructs the maximum likelihood model and uses the Markov Chain Monte-Carlo sampling method to estimate position coordinates. The method considers taking the interference factor into the model, and uses the random sampling method to solve the estimation problem, which has the advantage of fast convergence and high estimate precision. Furthermore, the Cramer-Rao lower bound (CRLB) of the model is derived. In simulation experiment, the distribution of Cramer-Rao Bound in locating space is given. Finally, simulations show that the MCMC method can estimate the target location accurately. Under the same simulation conditions, the MCMC method achieves greater estimated precision and has a lower computational complexity than the Fletcher-Reeves Method (FR).

    Sensor selection algorithm based on modified binary particle swarm optimization
    WEI Shengyun;ZHANG Jing;GUO Hong;LI Ou
    Journal of Xidian University. 2016, 43(2):  150-156.  doi:10.3969/j.issn.1001-2400.2016.02.026
    Abstract ( 275 )   PDF (655KB) ( 287 )   Save
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    Considering the problem of sensor selection for multi-target tracking in wireless sensor networks(WSN),a sensor selection algorithm based on binary particle swarm optimization(PSO) is proposed to maximize the tracking accuracy. The predicted coordinate of the target and the determinant of the Fisher information matrix (FIM) is used for sensor selection. A modified form of binary particle swarm optimization(MBPSO) is proposed to solve the model, which is designed by employing the binary vector coding manner, constraint satisfaction cyclic shift population initialization method, particle position updating rules with the V-shaped transfer function and guidance factor. Simulation results show that the proposed sensor selection algorithm can be efficiently applied in the multi-target tracking problem. Compared to the basic particle swarm optimization algorithm and genetic algorithm (GA), the modified algorithm achieves a balance between global optimization and local exploration, and can effectively avoid the local optimum. Moreover, the proposed algorithm is suitable for large-scale networks.

    Enhanced NNIA for multi-objective examination timetabling problems
    LEI Yu;JIAO Licheng;GONG Maoguo;LI Lingling
    Journal of Xidian University. 2016, 43(2):  157-161+192.  doi:10.3969/j.issn.1001-2400.2016.02.027
    Abstract ( 380 )   PDF (636KB) ( 273 )   Save
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    Based on the nondominated neighbor immune algorithm(NNIA), an enhanced NNIA is introduced for multi-objective examination timetabling problems. With the framework of NNIA, the hyper-heuristic approach is utilized to generate the initial population. In addition, the resource allocation model is designed to dynamically adjust the clone percentage of potential individuals. Experimental results on ten benchmark datasets prove that the proposed algorithm can solve examination timetabling problems effectively and obtaine competitive results.

    Energy-aware resource allocation for underlaid D2D multicast
    WANG Yuan;ZHAO Jihong;TANG Rui;QU Hua;DONG Jiaojiao
    Journal of Xidian University. 2016, 43(2):  162-167.  doi:10.3969/j.issn.1001-2400.2016.02.028
    Abstract ( 201 )   PDF (779KB) ( 266 )   Save
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    The Device-to-Device (D2D) communication underlaying cellular network is a promising component to improve the spectral efficiency for the system and lower down energy consumption for mobile terminals. Besides, in the D2D-aided content delivery scenario, it is potential to enhance the system capacity and individual quality-of-service (QoS) experience when D2D multicast is further enabled, but due to the battery-driven feature of mobile relays and the co-channel interference between cellular and D2D links, the optimization of energy conservation should be addressed. So, we propose a bipartite graph based resource allocation to minimize the total power consumption at the mobile relays under the individual QoS requirement by incorporating channel assignment and power control, and we also leverage the optimization of energy saving for system capacity.

    Parametric-planning model combining the transmission characteristics of network video service
    SONG Jiarun;XU Ziqiang;YANG Fuzheng
    Journal of Xidian University. 2016, 43(2):  168-173.  doi:10.3969/j.issn.1001-2400.2016.02.029
    Abstract ( 237 )   PDF (780KB) ( 262 )   Save
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    To evaluate the network video quality, a parametric-planning model is presented. Combining the characteristics of the channel and video sequence, the proposed model evaluates the video distortion caused by packet loss. It can be applied to effective network design and optimization on the premise of the quality of the video services. Firstly, by a detailed analysis of the packet loss behaviors and the characteristics of the video coding, a sequence distortion factor and a frame distortion factor are derived by combining the probability distributions of the packet loss event, which can reflect the video distortion from the perspective of the sequence impairment and frame impairment. Utilizing these factors, the video distortion caused by packet loss is evaluated and finally the parametric planning model is established. Experimental results show that compared with G.1070 and T-V models, the proposed model gets an increment of about 0.042 and 0.064 in Pearson Correlation Coefficient (PCC) and a decrement of about 0.043 and 0.055 in Root Mean Squared Error (RMSE).

    Component-based failure mode and effect analysis for flight control systems
    MA Yong;MA Jianfeng;SUN Cong;ZHANG Shuang;CUI Xining;LI Yahui
    Journal of Xidian University. 2016, 43(2):  174-179.  doi:10.3969/j.issn.1001-2400.2016.02.030
    Abstract ( 267 )   PDF (654KB) ( 158 )   Save
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    The conventional approaches of failure mode and effect analysis (FMEA) have not considered the mutual-influence between failure modes as well as the component-based design of systems. In this paper, we propose a new compositional approach of FMEA. We use fuzzy numbers instead of accurate numbers to describe the risk factors such as occurrence, severity, and detection in FMEA. To improve the accuracy of conventional FMEA, we construct the hierarchical FMEA graph and the respective influence matrix for each component. Then we derive the influence vector for the failure modes and leverage this vector to amend the risk priority numbers of conventional FMEA. The analysis of a practical flight control system shows the usability of our approach. Simulation results show that our compositional approach is more efficient than the non-compositional approach.

    Partition model into 3D-printable and no supporting parts
    WEI Xiaoran;GENG Guohua;ZHANG Yuhe
    Journal of Xidian University. 2016, 43(2):  180-185.  doi:10.3969/j.issn.1001-2400.2016.02.031
    Abstract ( 342 )   PDF (1713KB) ( 322 )   Save
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    The printing object must fit into the printing working volume and overhangs require a disposable support structure to be added, which are two main problems in the 3D printing process. Existing algorithms cannot solve these two problems at the same time. To solve these problems, we present a model partition algorithm, dividing the model into the pyramidal fitting printing working volume, with the pyramidal having the shape which can be printed without a supporting structure. Firstly, we partition the model surface using the region growing method and analyze the region's normal vector to determine the candidate dividing directions. Secondly, we use the candidate dividing directions to generate candidate dividing planes in order to segment the model. If the divided sub-model is not a pyramidal,continue segmenting the sub-model by using the same method until all of the sub-models are pyramidal. The candidate dividing planes may generate multi-group division modes. Each division mode constructs a tree, the evaluation function is employed to appraise the dividing values and the beam search method is utilized to search the largest value tree in the solution space which is the optimal partition. Experimental results show that the proposed algorithm can divide the model into sub-models which needn't support structures and fit into the printing working volume.

    High-performance programmable charge pump for low voltage PLLs
    LIANG Liang;ZHU Zhangming;YANG Yintang
    Journal of Xidian University. 2016, 43(2):  186-192.  doi:10.3969/j.issn.1001-2400.2016.02.032
    Abstract ( 263 )   PDF (2351KB) ( 191 )   Save
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    This paper proposes a charge pump with a programmable output current for low voltage phase-locked loops (PLLs). It consists of two sub-units both of which leverage replica bias and feedback control techniques to achieve perfect match between charging and discharging currents. With the help of the current summing structure, the output current variation in each sub charge pump can be compensated by the other. Thus, their sum current remains relatively constant in a wide output voltage range. The charge pump can be programmed to output a 50μA~1.55mA current, with a 50μA minimum step. It is designed in a 0.13μm CMOS process and the post-layout simulation demonstrates the total current mismatch and variation rates are limited in 0.15% and 5%, over the output voltage range of 0.1~1.05V. Such precise matching greatly suppresses the reference spur and static phase error, and the good current constancy is favorable for dynamic design. Both features render our design suitable for low voltage PLLs.

    Remote sensing image fusion based on sparse non-negative matrix factorization
    LI Hong;LIU Fang;ZHANG Kai
    Journal of Xidian University. 2016, 43(2):  193-198.  doi:10.3969/j.issn.1001-2400.2016.02.033
    Abstract ( 269 )   PDF (7413KB) ( 186 )   Save
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    In order to reduce the spectral and spatial distortions, a novel method based on sparse non-negative matrix factorization (SNMF) is proposed for multispectral and panchromatic images fusion. Firstly, the high spatial resolution and low spatial resolution dictionaries are learned from panchromatic. Then we construct a sparse non-negative matrix factorization model of the multispectral image. Thus, the coefficients matrix with spectral information can be obtained. The high spatial resolution multispectral image is produced by the multiplication high spatial resolution dictionary and the coefficients matrix. By introducing the sparse regularization, the instability of the standard non-negative matrix factorization is conquered and the fused image can preserve the high spectral and spatial information. Some experiments are made on QuickBird and Geoeye satellite datasets, and experimental results show that our proposed method can reduce distortions in both the spectral and spatial domains, and outperform some related pan-sharpening approaches in visual results and numerical guidelines.

    SybilGrid: Sybil detection method based on directed social networks
    WANG Yongcheng;MENG Yanhong
    Journal of Xidian University. 2016, 43(2):  199-204.  doi:10.3969/j.issn.1001-2400.2016.02.034
    Abstract ( 350 )   PDF (810KB) ( 413 )   Save
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    A Sybil detection method based on the random walk strategy is proposed to detect the Sybil nodes in the directed social network. The performance of the algorithm is evaluated by collecting the real social network topological data on Sina Weibo, and the effectiveness of the algorithm is proved. In addition, compared with the existing SybilDefender method, it is found that the false alarm rate of SybilDefender is about 1.6 times as great as SybilGrid. Meanwhile, to achive the same false alarm probability, the random walk length required by SybilGrid is much shorter, meaning that the detection efficiency of SybilGrid is higher.