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Table of Content

    26 March 2012, Volume 30 Issue 2
    Communication Engineering
    Complex-Network Effects of Multi-radio Wireless Ad Hoc Networks
    LU Yang, TIAN Yi-ming, WEI Zhen, WEI Zhen-chun
    2012, 30(2):  111-116.  doi:10.3969/j.issn.0255-8297.2012.02.001
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    Analysis of the mechanism of complex networks and wireless ad hoc networks shows that wireless ad hoc networks under certain conditions have complex network effects. A control strategy for multi-radio nodes is proposed based on the feasibility of small-world wireless ad hoc networks with multiple radio nodes. Taking into consideration the node design, the deployment of multi-radio nodes is controlled according to the network
    environment and clustering coefficient of the nodes. The results show that the proposed method optimizes the network topology, and increases the network’s robustness. It has theoretical and practical significance to further network optimization.

    Modeling and Analysis of Communication Region of Primary Receiver in Cognitive Networks
    LIAO Yong, TAN Xiao-heng, CHENG Jin-bo, ZHANG Yu-xiang, YANG Hong.etc
    2012, 30(2):  116-119.  doi:10.3969/j.issn.0255-8297.2012.02.002
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    By analyzing the existing cognitive network models, this paper proposes a cognitive network model in which the primary receiver is treated as a center. This solves the irrationality problem when modeling the interference region where the primary transmitter is treated as a center. Using the proposed model and the information theory, we obtain mutual quantitative restriction correlation of the primary user communication radius, cognitive user density and throughput of primary user under the condition of lowest throughput and communication interruption probability of primary users. Numerical simulation results show that the model is reasonable and effective when a primary receiver is interfered by cognitive users.

    Localization of Collaboration Ripples in Wireless Sensor Network
    ZHANG Jin-yi1;3, DUAN Su-yang1, WU Yu-jian1, WANG Chun-hua1, DING Meng-ling2
    2012, 30(2):  120-127.  doi:10.3969/j.issn.0255-8297.2012.02.003
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    This paper proposes a collaboration ripple algorithm for high accuracy, large range and low cost localization of large scale nodes in a wireless sensor network (WSN). A splicing network topology is designed based on a rational network topology research. Location error is reduced with collaboration among the nodes. The ripple algorithm is applied to locate unknown nodes in a unit cell to realize accurate localization of
    neighboring notes. Verification of the algorithm shows that the collaboration ripple location algorithm can reduce anchor nodes by 3.20%, and improve precision by 20.00%, indicating effectiveness of the proposed algorithm.

    Cyclostationarity Analysis of ZPOFDM Signals and Its Application to Classification of Multicarrier Modulation Signals
    CUI Wei-liang, JIANG Hua, LI Jian-qiang
    2012, 30(2):  128-134.  doi:10.3969/j.issn.0255-8297.2012.02.004
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     An improved OFDM signal recognition algorithm is proposed to distinguish the zero-padding OFDM (ZPOFDM) signal from multicarrier signals. Based on the second-order cyclic cumulant of ZPOFDM and other signals and combined with a cyclostationary test, the algorithm can classify signals such as ZPOFDM, cyclic-prefix OFDM (CPOFDM), and single carrier signals in fading channel. The theoretical analysis and simulations confirm the effectiveness of discriminating multicarrier signals in frequency selective channels without synchronization and parameters estimation.

    Blind Modulation Recognition for MIMO Signals
    ZHANG Lu-ping, WANG Jian-xin
    2012, 30(2):  135-140.  doi:10.3969/j.issn.0255-8297.2012.02.005
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    To recognize modulation in MIMO signals, a modulation classification method based on blind source separation is proposed. Singular value decomposition of the received signal’s correlation matrix is used to estimate the number of transmitting antennas and whiten the received signal. The source signal is recovered with joint approximate diagonalisation of eigen-matrices (JADE). Based on analyses of four new spectral features and the fourth-order cumulant, a modulation recognition algorithm is proposed for six kinds of MIMO signals. The method does not need to estimate the carrier frequency and the symbol rate, thus is highly practical. Simulation results show that the proposed method has good performance.

    EBPSK Signal Detector Based on IM-SAPSO and SVM
    JIN Yi, WANG Ji-wu, WU Le-nan
    2012, 30(2):  141-145.  doi:10.3969/j.issn.0255-8297.2012.02.006
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    Parameter selection is important to the classification performance of support vector machine (SVM),which is essentially a search of optimum. This paper proposes a parameter selection method for SVM with the algorithm of improved simulated annealing particle swarm optimization (IM-SAPSO) to search the best parameters. The minimized K-fold cross-validation error is used as the object of IM-SAPSO. The optimized SVM is then used to classify the symbols 0 and 1 passing the impacting filter of an extended binary phase shift keying (EBPSK) communication system. Comparison is made for the detection performance of EBPSK detector between the proposed IM-SAPSO and other methods including those based on SVM, PSO-SVM and amplitude integral decision. Simulation results show that IM-SAPSO and SVM are significantly better than the other three methods.

    Signal and Information Processing
    DOA Estimation of Wideband Signals Based on Cyclostationarity
    LIU Fu-gang1;2, DIAO Ming1
    2012, 30(2):  146-150.  doi:10.3969/j.issn.0255-8297.2012.02.007
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    For direction of arrival (DOA) estimation of cyclostationarity wideband signals, by analyzing the signal’s cyclostationarity and conjugate cyclostationarity properties, a new method of DOA estimation from wideband signal is proposed based on the subspace decomposition method. The new method applies signals’ cyclostationarity and conjugate cyclostationarity information to form an extended cyclic correlation matrix.The spatial spectrum of wideband signal is obtained. The method has good performance of the cyclic MUSIC algorithm, and does not require optimal lag time to process the wideband signals. Computer simulations are conducted to show good performance in signal selective direction finding, with high resolution and interference suppression capability.

    Real-Time Mosaicing for Aerial Videos Combined with Geographical Parameters
    HE Bei1, WANG Gui-jin1, SHEN Yong-ling2, LIAO Chao1, LIU Chun-hua2, LINXing-gan1
    2012, 30(2):  151-157.  doi:10.3969/j.issn.0255-8297.2012.02.008
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    Against high computational cost and severe accumulative error problems existing in the current video mosaicing methods, we propose a real-time mosaicing algorithm for aerial videos based on geographical parameters. First, we decompose the camera motion model for image registration in real time. We then estimate the principal orientation of each frame, and extend the uni-orientation manifold mosaicing algorithm to a multi-orientation algorithm. Finally, with geographical parameters, we rectify mosaicing strips locally to make sure that the mosaics are mapped precisely on the real geographical positions. Experimental results for synthetic and real videos demonstrate accuracy and the near real-time property of our algorithm, with the mosaicing speed up to 25 frames per second for videos of 640£480 resolution.

    Sonar Image Mosaicing Based on Bionic Mechanical Pan-Tilt
    CHEN Jin-bo1;2, LI Heng-yu1, GONG Zhen-bang1, LUO Jun1, XIE Shao-rong1;2
    2012, 30(2):  158-164.  doi:10.3969/j.issn.0255-8297.2012.02.009
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    This paper proposes a mosaicing method of sonar images based on a bionic mechanical pantilt system. From the principle of vestibule-ocular reflex, an active compensation control system of bionic mechanical pan-tilt is established. The system can compensate the sonar image instability due to attitude variation of the sweeping survey boat or submarines during operation. To obtain sonar image mosaics, the sonar images are matched with information of the attitude sensors and GPS. Simulation experiments are performed in different environments. The results show that the model is robust and has the ability of dynamic compensation. The results show effectiveness of the system.

    Hypergraph-Based Image Steganography
    HU Chen, WANG Jian-jun
    2012, 30(2):  165-172.  doi:10.3969/j.issn.0255-8297.2012.02.010
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    This paper proposes a hypergraph-based steganographic method. In this method, pixels are divided into groups. Hyperedges are constructed by exchangeable relationship between pixels. A hypergraph that is the set of hyperedges is used to represent the cover image. By looking for hypergraph matching using a local optimal greedy algorithm, the secret message is embedded. To show effectiveness of the algorithm, it is compared with the stegangraphic approach based on graph theory for modifying cover images. It is also compared with other traditional spatial domain methods in steganalysis resistance. Experiments show that the proposed method requires less modification of pixels to result in better visual quality of the stego images. It can better resist steganalysis than other spatial domain methods.

    Remote Sensing Image Segmentation Based on Heuristic Edge Growing
    LI Gang1, WAN You-chuan1, LI Meng2
    2012, 30(2):  173-180.  doi:10.3969/j.issn.0255-8297.2012.02.011
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    In view of difficulties of edge point detection and edge line linking in edge-based segmentation,this paper proposes a new segmentation method for remote sensing images based on heuristic edge growing.First, improvements are made to the Canny operator for edge point detection including adaptive wavelet de-noising, optimal double-threshold calculation and edge point decision based on total variation. A new heterogeneity index of edge linking is defined, which includes spatial heterogeneity and spectral heterogeneity.Heuristic decision of global mutual best fitting is then proposed to link broken edges of the same target as far as possible. Experiments are carried out using Quickbird image and aerial image to evaluate the proposed method. Segmentation results are compared to those obtained with eCognition, showing that the proposed method can link most edges correctly and produce accurate segmentation results.

    Track Association Method Using Modified Fuzzy Membership
    JING Pei-liang, LIU Fang
    2012, 30(2):  181-186.  doi:10.3969/j.issn.0255-8297.2012.02.012
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    Track association is a prerequisite to track fusion in distributed multi-sensor/multi-target tracking.With the traditional method, the correct association rate seriously declines in a dense target environment.To solve this problem, this paper presents a new track association method. Traditional fuzzy membership is smoothed, and similarity among tracks is considered from a whole view. Thus a modified fuzzy membership is proposed. In addition, a training method is designed to obtain the parameters based on a priori sequential association couples. Simulation shows that the method can easily set parameters and has better performance as compared to the classical fuzzy double-threshold method, therefore more suitable to practical applications.

    Cholesky Factorization for Covariance Matrix Recovery
    DU Hang-yuan, HAO Yan-ling, ZHAO Yu-xin, CHEN Li-juan
    2012, 30(2):  187-193.  doi:10.3969/j.issn.0255-8297.2012.02.013
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     For simultaneous localization and mapping based on sparse extended information filter, we compare
    the principles of nearest neighbor data association, maximum likelihood data association and joint compatibility
    test data association, and discuss the requirements of marginal covariance matrix recovering in data
    association. A computationally efficient approach based on Cholesky factorization is proposed to exactly recover
    the marginal covariance from information matrix. In the simulation, we compare the proposed algorithm
    with covariance bound approximation, and analyze three common data association approaches using the proposed
    algorithm in SLAM based on a sparse extended information filter. The results show that the proposed
    recovery algorithm is suitable for various data association approaches, leading to high localization accuracy
    and reduced computational complexity. Performance of different data association approaches in SEIF-SLAM
    are discussed.

    Control and System
    UAV Attitude Measurement Using Adaptive Compensation Technique
    GAO Ming1, XU Qing-he1, ZHAO Wen-cai2
    2012, 30(2):  194-202.  doi:10.3969/j.issn.0255-8297.2012.02.014
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    A method of ascertaining UAV attitude by compensation and positioning of the laser spot center is proposed. The method uses the principle of cooperative target attitude measurement combined with wander and spreading effects of the laser beam under actual atmospheric turbulence. A polygon is formed by calculating the center of the single frame laser spot and extracting feature point of outline constituted by center of the laser spot within unit interval. The gravity center of the polygon is taken as a reference. An adaptive attitude measurement compensation model is thus established. Numerical results show that, when the target distance is 3 km, the maximum error of the attitude angle is 0.221± by using the simulated annealing algorithm in the iterative solver and adaptive compensation. This indicates that the attitude measurement algorithm with adaptive compensation has high accuracy and good convergence.

    Dynamic Positioning of Dredgers Using Nonlinear Dynamic Surface Control and Feed-Forward Compensation
    ZHANG Yu-hua 1;2, JIANG Jian-guo1, GAO Deng-ke1
    2012, 30(2):  203-208.  doi:10.3969/j.issn.0255-8297.2012.02.015
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    To deal with difficulties in the control of dynamic positioning of dredgers under large dredging forces reaction, a method of combining dynamic surface control and feed-forward compensation is proposed to be used in dynamic positioning of dredgers. Dredging forces can be feed-forward compensated by sensors, and the dynamic surface controller guarantees global asymptotic stability of the closed-loop system. A
    first-order low-pass filter in the back-stepping design process allows the dynamic surface control technique to be implemented without differentiating any model nonlinearities, which can significantly simplify the design. Simulation results show that the proposed method has satisfactory performance.

    Machine Vision-Aided Relative Navigation for UAV Aerial Refueling
    WANG Long1, DONG Xin-min1, JIA Hai-yan2
    2012, 30(2):  209-214.  doi:10.3969/j.issn.0255-8297.2012.02.016
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    To precisely obtain the relative pose of UAV during aerial refueling docking, a machine vision-aided INS/GPS/MV integrated navigation scheme is proposed. Feature extraction and match algorithm of machine vision image are studied. By introducing relative inertial errors, an extended state model of global filter is designed. GPS and machine vision measurement models are established using level-arm vectors. A global multirate extended Kalman filter based on federal framework is designed to realize multirate mutisensor data fusion. Comparison is made between the proposed algorithm and the standard EKF algorithm. Simulation shows that the proposed algorithm can effectively fuse INS/GPS/MV data. The navigation parameter precision and output bandwidth satisfy the requirements of UAV aerial refueling. It can improve UAV qualities and loosen requirements of flight control systems.

    UAV Route Planning Based on Ant Colony Optimization and Artificial Potential
    LI Meng, WANG Dao-bo, BAI Ting-ting, SHENG Shou-zhao
    2012, 30(2):  215-220.  doi:10.3969/j.issn.0255-8297.2012.02.017
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    To deal with dynamic routes planning of unmanned aerial vehicles in a complicated environment, a new method that combines ant colony optimization with artificial potential is proposed. The mission region is described as a grid model. In the route search process, ants are influenced not only by pheromone and heuristic information, but also by the potential field force. According to the node location’s potential field, the state transition rules consist of deterministic choice and probabilistic choice. The environmental perception factor is designed for dynamically adjusting the proportion of deterministic choice. In order to make full use of the known environmental information and guide the ant’s search, the potential field direction and the distance between the candidate node and the goal are used to construct comprehensive heuristic information. Simulation results show that the proposed method can effectively obtain optimal feasible routes. The optimization result is better than that of the simplex ant colony and artificial field, and has better convergence speed and optimization precision.