Journal of Applied Sciences

Joint Optimization Algorithm for Protograph LDPC Codes

FANG Yi1, WANG Lin1, CHEN Ping-ping2, XIAO Min1

2011, 29(6): 551-558. doi:10.3969/j.issn.0255-8297.2011.06.001

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According to the requirements and characteristic of space communication, protograph low-density parity-check (LDPC) codes have been proposed by Jet Propulsion Laboratory (JPL), which have better performance than conventional LDPC codes. In this paper, we propose a joint optimization algorithm for protograph LDPC codes, aiming at lowering the error floor of protograph LDPC codes, while maintaining good perfor ance at waterfall region without increasing encoding and decoding complexity. Theoretical analysis and simulation indicate that the repeat accumulate (RA) and accumulate repeat accumulate (ARA) codes designed by using the proposed algorithm have a remarkable coding-gain, and a lower error floor, as compared with the conventional RA and accumulated repeat by-4-jagged accumulate (AR4JA) codes at the high SNR region.

MAC Layer Cooperative Multicast Strategy Based on IEEE 802.11 Protocol

SONG Liu-bin1, XU You-yun1;2, XIE Wei2, YU Jiang1

2011, 29(6): 559-564. doi:10.3969/j.issn.0255-8297.2011.06.002

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In this paper, we propose a MAC layer cooperative multicast strategy based on the IEEE 802.11 protocol, in which correctly received data can serve as a temporary relay if the user locates a right position. We analyze the outage probability and throughput performance of the proposed strategy, and present a simulation method in NS2. Simulation results show that the new strategy has a better throughput and lower packet loss performance compared to the original MAC protocol.

Modulation Recognition Using Fractional Low-Order Cyclic Spectrum Coherence Coefficient

ZHAO Chun-hui, YANG Wei-chao, DU Yu

2011, 29(6): 565-570. doi:10.3969/j.issn.0255-8297.2011.06.003

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Noise with alpha stable distribution leads to loss of efficacy of the second-order cyclic spectrum coherence coefficient, and degrades related algorithms for communication signal modulation recognition. A recognition algorithm based on fractional low-order cyclic spectrum coherence coefficient is proposed to solve this problem. The related theory of fractional low-order cyclic spectrum coherence coefficient is first introduced.
Fractional low-order cyclic spectrum coherence coefficients of communication signals are analyzed. Based on the analysis, the algorithm extracts the cyclic frequency profile of spectrum coherence coefficient as the recognition characteristic parameter, and uses a BP neural network as a classifier to achieve communication signal modulation recognition. Simulation results show that, in an alpha stable distribution noise environment, the performance of the proposed algorithm is superior to that based on second-order cyclic spectrum coherence coefficient. These two algorithms have the same performance in Gaussian noise.

Least Square Error Synthesis with Nulls for MIMO Radar Beam Pattern

ZHANG Yu, WANG Jian-xin

2011, 29(6): 571-576. doi:10.3969/j.issn.0255-8297.2011.06.004

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For multi-input multi-output(MIMO) radars, grating lobes appear in the transmitting pattern when the spacing between transmitting antennas and that between receiving antennas are related with some particular values. In this case, high sidelobes occur in the synthetic pattern obtained by multiplying the transmitting pattern with the receiving pattern. This paper analyzes the cause of high sidelobes mathematically, and proposes a novel algorithm that can synthesize a least square error (LSE) receiving pattern with nulls to suppress high sidelobes for MIMO radar. The optimum weighting with nulls is obtained with the Lagrange multiplier method. The LSE receiving pattern is synthesized to solve the high sidelobe problem. Simulation results verify that high sidelobes in the synthesized pattern can effectively be suppressed using the obtained weightings.

Pose Estimation Based on Integrated Reconstruction and Orthogonal Iteration

GUO Jun1;2, DONG Xin-min1, WANG Long1

2011, 29(6): 577-584. doi:10.3969/j.issn.0255-8297.2011.06.005

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Abstract: Multiple camera systems (MCS) have attracted increasing attention in machine vision. Regarding pose estimation of MCS, a novel integrated reconstruction and orthogonal iteration algorithm is proposed. A general camera model is introduced to formulate MCS to derive the algorithm. To make full use of the redundant measurements of MCS, the observed reference points are classified, and a weighted objective function is constructed. Using the objective function, advantages of the optimal absolute orientation solution (OAOS) and the orthogonal iteration (OI) algorithm are combined. Introduction of 3D reconstructed information not only overcomes the pose ambiguity of OI but also improves convergence and robustness in pose estimation. The effects of reconstructed error on final estimation are reduced using an adaptive weighting method. Simulation results show effectiveness and superiority of the proposed algorithm.

Weighted Neighborhood Reconstruction Algorithm and Its Application to Acoustic Target Recognition

WANG Yi1;2, ZOU Ji-wei1, YANG Jun-an1;2, LIU Hui1;2, BAI Jing-lu3

2011, 29(6): 585-591. doi:10.3969/j.issn.0255-8297.2011.06.006

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Abstract: Manifold learning methods are sensitive to noise especially in acoustic targets recognition. To deal with this problem, we present a novel manifold learning algorithm for noisy manifold, termed weighted neighborhood reconstruction (WNR). The algorithm builds a curve that can best reflect the trend of the noisy manifold sub-surface. The curve is extended to reconstruct the manifold sub-surface and calculate low dimensional embedding on the new surface. The proposed algorithm can minimize noise effects on manifold while keep the original surface trend. The algorithm is tested on public database and low attitude flying targets acoustic signal. Experiment results show that the proposed algorithm is robust against noise, and outperforms the other three methods cited in this paper.

Human Tracking Algorithm Robust against Sudden Changes of Illumination

YUAN Xue, SONG Yong-duan

2011, 29(6): 592-597. doi:10.3969/j.issn.0255-8297.2011.06.007

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Abstract: This paper presents a robust human tracking algorithm. As human detection and tracking are important to intelligent surveillance, it is essential to ensure that the system can adapt to any environmental changes and track the objects without interruption. This paper proposes a human tracking algorithm robust against sudden changes of illumination. Sudden illumination changes are automatically detected. The camera’s
exposure time is adjusted to compensate the changes. A mean shift algorithm is developed to continuously track the same object before and after the sudden change so as to achieve reliable tracking. Experiments verify effectiveness of the proposed algorithm.

Hyperspectral Remote Sensing Image Classification with Extremely Randomized Clustering Forests

XU Hai-wei1, YANG Min-hua1, HAN Rui-mei2, WANG Zhen-xing3;4

2011, 29(6): 598-604. doi:10.3969/j.issn.0255-8297.2011.06.008

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Hyperspectral images contain rich spectral information and have better performance in ground target recognition than panchromatic and multispectral images. An extremely randomized clustering forests (ERC-Forests) algorithm is introduced after analysis of the decision tree algorithm. Hyperion hyperspectral images and IRS-p6 image data of Qilian County, Qinghai Province, are used in the experiment. After dimension reduction with subspace methods and based on the spectral range, support vector machine (SVM), neural network (NN) and maximum likelihood (MLC) are used for classification. The results are compared with that of random decision trees algorithm, showing that the extremely randomized clustering forests algorithm is better, without dimension reduction. The method is widely applicable to hyperspectral remote sensing.

Steganography Based on Pixel Exchange and Diamond Encoding

ZHU Dong-jiu, WANG Jian-jun

2011, 29(6): 605-612. doi:10.3969/j.issn.0255-8297.2011.06.009

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Abstract: Inspired by Steghide and diamond encoding, we develop a new steganographic method which preserves the first-order statistics of the cover data and has high embedding efficiency. Pixels are allowed to change only by 1 or ?1 so that distortion of the cover image is small. As with Steghide, the proposed method embeds a 13-ary digit in two sections of pixels to increase the exchange rate. For some sections, two exchanges are necessary since the diamond encoding requires that data be changed by 2, and this cannot be done in +-1 embedding. An embedding is constructed by finding a maximum matching of hypergraph. Experiments demonstrate that the proposed method outperforms Steghide and the diamond encoding in terms of embedding efficiency, visual quality and anti-detection ability.

Edge Detection for Side-Scan Sonar Images Based on Improved Canny Operator

HUO Guan-ying1;2, WANG Min1;2, CHENG Xiao-xuan1;2, LI Qing-wu1;2

2011, 29(6): 613-618. doi:10.3969/j.issn.0255-8297.2011.06.010

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To deal with strong speckle noise of side-scan sonar images, an edge detection method based on improved Canny operator is proposed. According to a multiplicative model and the Rayleigh distribution of speckle noise, sonar image de-speckling is performed locally and adaptively in the contourlet transform domain without sub-sampling. This effectively suppresses speckles and better protects edges without blurring due to Gaussian smoothing. Gradients of the de-speckled sonar image are computed. The maximal magnitudes of the gradients are obtained by non-maximum suppression. The maximal points are classified into three types: strong edge points, weak edge points and non-edge points. Two thresholds are automatically determined based on the maxima of inter-class variance. A binary edge map is obtained with the two thresholds followed by weak edge linking. Experiments on both synthetic and real sonar images show that the proposed method has the advantages over other methods such as Canny operator and wavelet modulus maxima in terms of edge integrity, positioning accuracy and false edge points.

Specific Person Detection in Video Stream Based on Robust Hash Signature

GAO Hao-lin, LI Bi-cheng, PENG Tian-qiang

2011, 29(6): 619-625. doi:10.3969/j.issn.0255-8297.2011.06.011

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Detecting a specific person in video sequence is a challenging problem. We propose a real-time video detection method based on robust Hash signature. The approach consists of three steps. First, it devises the robust Hash function and computes the signature of the target image. Then, the signature of every representative key frame is acquired from the video sequence. Finally, the distance of two signatures is calculated to decide whether the target image is present. The proposed approach can capture key frames that may include a specific person in real-time, and locate the shot containing the detected key frames. Experimental results demonstrate that the approach can achieve high accuracy for retrieving repetitive specific information from video sequences, and can be used in applications such as detecting image copies and duplicate contents.

Semi-supervised Feature Weighting Using Graph Laplacian for Hyperspectral Band Selection

HUANG Rui, CHEN Ling

2011, 29(6): 626-630. doi:10.3969/j.issn.0255-8297.2011.06.012

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A semi-supervised feature weighting using graph Laplacian is proposed for hyperspectral band selection. The method first constructs the graph Laplacian modified by the label information. The projection matrix is obtained by solving a generalized eigen-problem. The corresponding matrix coefficients are analyzed using the loading factors to assign weights to the original bands. Experiments with hyperspectral data sets are carried out to make comparison among several band selection algorithms. The results show that the proposed method can achieve the best performance as it makes good use of class information from the labeled samples and local structure clues hidden in numerous unlabeled ones.

Automatic Test for Chip Function Verification Using Adaptive Genetic Algorithm

SU Lin-lin, ZHANG Xiao-lin

2011, 29(6): 631-636. doi:10.3969/j.issn.0255-8297.2011.06.013

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Abstract: This paper addresses two problems occurring in chip function verification: long verification time and high interdependency between verification and design under test. An automated test method using an adaptive genetic algorithm is presented for chip function verification. Event function coverage and event toggle coverage are defined, and the relationship between the two kinds of coverage is given. A fitness function is
generated to improve reliability using the function coverage and toggle coverage. Achieving the same coverage, the test time is reduced by about 25%-30% with the proposed method as compared to the simple genetic algorithm.

Design of UWB Antenna Using Improved Quantum Genetic Algorithm and Optimum Uniform Approximation

HU Wei, ZHANG Jian-hua, QI Lin, HU Feng-ge

2011, 29(6): 637-643. doi:10.3969/j.issn.0255-8297.2011.06.014

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Abstract: To design ultra-wideband antennas, an efficient method is used. The method combines an improved quantum genetic algorithm (IQGA) and the volume surface integral equation based on the method of moment. Computation time is saved by using optimum uniform approximation that accelerates the analysis of the ultrawideband antenna’s characteristics in calculating fitness. A novel microstrip-fed UWB antenna with dual notch
bands in 3?4 GHz and 5?6 GHz is designed and fabricated. Comparison between the optimized and measured voltage standing wave ratios shows that the method is correct and effective.

Optimal Homing Guidance Law with Autopilot Dynamics

HUA Wen-hua, CHEN Xing-lin, SONG Shen-min

2011, 29(6): 644-649. doi:10.3969/j.issn.0255-8297.2011.06.015

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Abstract: For maneuvering target interception, a new method for guidance law design is presented, which takes into account the autopilot dynamics, and is more realistic and effective. Instead of being determined in a single optimization problem, the interceptor strategy and target strategy are determined separately in two separate optimization problems. First, the target strategy is derived in a two-sided optimization problem that
does not consider the interceptor’s lag. The interceptor homing guidance law is then derived in a one-sided optimization problem that considers the interceptor’s lag subject to the target strategy derived in the first optimization problem. Simulation results show that the proposed optimal guidance law can improve performance and requires low maneuverability by properly considering the autopilot lag.

Optimization of Performance Weighted Function for Missile Robust Controller Using PSO Algorithm

ZHANG Min, CHEN Xin, LU Yu-ping

2011, 29(6): 650-654. doi:10.3969/j.issn.0255-8297.2011.06.016

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Abstract: In the missile 1 robust controller design, the design of performance weighted function is difficult and time-consuming. Traditionally, one can only use trial-and-error or simulation methods, and therefore the controller’s overall performance cannot be guaranteed. In this paper, a particle swarm optimization (PSO) algorithm is used to optimize the performance weighted function automatically. By analyzing each parameter of the weighted function, parameters of the algorithm are selected. So the PSO algorithm and the 1 controller design process can be combined. Simulations show that the 1 controller can meet the requirements of control performances using the optimized performance weighted function. The objective function is convergent, and effectiveness of the method is confirmed.

Fault Detection Filter Design for Network Control Systems with Random Delays

WEN Li-yan, PENG Chen, PEI Ling-xi, XUAN Hui-ming

2011, 29(6): 655-660. doi:10.3969/j.issn.0255-8297.2011.06.017

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Abstract: This paper discusses fault diagnosis for network control system with random delays. Two general fault detection filters are designed: Kalman filter and H1 filter. The former is obtained using an iteration method, and the latter is realized with linear matrix inequalities (LMI) and augmented matrices to ensure the smallest possible error between the residual and the fault. A numerical example is provided to show
effectiveness of the present methods.

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