Table of Content

31 July 2014, Volume 32 Issue 4

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Articles

Two-Dimensional Arimoto Gray Entropy Thresholding

WU Yi-quan1,2, CAO Peng-xiang1,3, WANG Kai1, YIN Jun1

2014, 32(4):  331-340.  doi:10.3969/j.issn.0255-8297.2014.04.001

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A recently proposed 2D Arimoto entropy thresholding method only depends on frequency information of gray scale in an image, without considering uniformity of within-class gray scales. To solve this problem, a 2D Arimoto gray entropy thresholding method based on gray scale-gradient histogram is proposed.Uniformity of within-class gray scale is considered based on Arimoto entropy and a formula for 1D Arimoto gray entropy threshold selection constructed. Using regional division of object and background in a gray scale-gradient 2D histogram, a formula for 2D Arimoto gray entropy threshold selection is derived. Recursion formulae of intermediate variables in the threshold selection criterion function are used to eliminate redundant computation. The local period of an artificial bee colony algorithm is improved using a chaotic sequence based on tent mapping. The improved bee colony optimization algorithm can accelerate search speed of the optimal threshold for image segmentation to significantly reduce execution time. Experimental results based on a large number of typical images show that the proposed method can segment image quickly and accurately, with the overall performance better than 2D Shannon entropy thresholding, Tsallis gray entropy thresholding, and Arimoto entropy thresholding.

Communication Engineering

Multi-task Compressed Spectrum Sensing Based on Belief Propagation Grouping

WANG Yong, LI Hong, QI Li-na

2014, 32(4):  341-348.  doi:10.3969/j.issn.0255-8297.2014.04.002

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As coverage of primary users overlaps in cognitive radio, a method grouping secondary users first and cooperative spectrum sensing within group afterwards is introduced. A grouping algorithm using similarity of secondary users based on simplified belief propagation (BP) is proposed to exploit the previous spectrum sensing information of all secondary users and extract relevant parameters from the exploited information.The current secondary users are then grouped with the BP algorithm according to the extracted relevant parameters. We use a multi-task compressed spectrum sensing method with better recovery ability in current cooperative spectrum sensing methods within each group. Simulation results show that, in a heterogeneous spectrum situation, the proposed method can improve probability of correct detection of the spectrum sensing under better probability of false alarm compared to other methods. The spectrum sensing results are improved with the increasing of the sensing users.

Inertial Indoor Navigation with 3D Complex Motion Mode of Pedestrian Dead Reckoning

CHEN Xing-xiu1, ZHANG Jin-yi1,2,3, YAN Li1, LIU Jiang2, ZHOU Wen-qiang2

2014, 32(4):  349-350.  doi:10.3969/j.issn.0255-8297.2014.04.003

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 In human indoor navigation research, pedestrian dead reckoning (PDR) involves less calculation with lower accuracy sensor, and therefore becomes popular in micro-electro-mechanical system-inertial measurement unit (MEMS-IMU). However, conventional PDR approaches only consider 2D forward motion mode,which is unrealistic. This paper uses an approach named 3D complex motion mode PDR to describe human’s indoor life. By collecting the original human motion information with a 10-axis MEMS sensor, this paper proposes a 3D complex motion mode PDR algorithm. 2-axis detection of 2-peak within double zero-crossing and pitch detection methods are used to detect 5 kinds of non-walking motion mode to reduce interference of step detection. Phase reversal and pressure mutation methods are used to distinguish 3 kinds of walking motion mode to record every effective step. The 3D coordinates of the human location are then calculated. Experimental results show that, for the actual human indoor 3D and complex motion mode, the proposed algorithm increases the horizontal positioning accuracy by 99% compared with conventional peak detection and zero-crossing detection PDR. Accuracy of height positioning reaches 92.4%.

A MIMO-UWB Communication System for Coal Mines

ZHANG Guo-peng, LIU Peng, DING En-jie

2014, 32(4):  357-364.  doi:10.3969/j.issn.0255-8297.2014.04.004

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 This paper applies the multi-input multi-output (MIMO) antenna technology to improve the bit error rate (BER) performance of ultra wideband (UWB) systems for underground coal mines. The multipath propagation environment in coal mines is studied. UWB transceivers using single-input single-output (SISO)antennas and their BER performance are analyzed. Feasibility of using MIMO for anti-multipath fading in coal mines is studied theoretically. With the transmission energy and the receiver structure unchanged, a MIMOUWB based space-time coding/decoding scheme is developed by just increasing the number of transmission antennas. Simulation results show that the MIMO-UWB space-time coding/decoding scheme can achieve 35 dB BER performance gain in various coal mine environments as compared with traditional SISO-UWB systems.

Strategy Selection for Network Survivability Based on Three-Players’ Dynamic Game

WU Wen, MENG Xiang-ru, MA Zhi-qiang, LIANG Xiao

2014, 32(4):  365-371.  doi:10.3969/j.issn.0255-8297.2014.04.005

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 A strategy selection model for network survivability based on three players’ dynamic game is proposed to efficiently improve the active defensive ability of a network in the face of attack, defender, and failure accidents. The non-cooperative complete information dynamic game theory is used to construct the
three players’ survivability game model which takes attacker, defender and accidents as the game’s participators.The formal expression of sub-game perfectness Nash equilibrium by backward induction is given.The strategy selection algorithm for three players’ dynamic game is then proposed. Simulations show that each optimal strategy acquired by the given strategy selection model and the algorithm can meet the actual requirement.

Improved Localization in Dynamic Non-line-of-Sight Environments Using a Modified Log Path-Loss Model

WANG Ri-ming1,2, FENG Jiu-chao1

2014, 32(4):  372-378.  doi:10.3969/j.issn.0255-8297.2014.04.006

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To reduce estimation error caused by static path loss factor in a log path-loss model, a modified log path-loss model is proposed in this paper based on statistical analysis on the Zigbee localization experimental data. In this model, a negative exponent function is used to describe the distance relation of the path loss factor with target nodes and fixed nodes to improve performance of the traditional log path-loss model. A maximum likelihood (ML) estimator and the corresponding Cramer-Rao lower bounds is then proposed and derived. Results of Zigbee localization experiments in laboratory and bus station demonstrate good performance with accurate localization and flexibility for varying environments.

Experimental Investigation on Non-optical Heterodyne Detection Technology of 1 km Atmospheric Laser Communication System

KE Xi-zheng, CHEN Jin-ni

2014, 32(4):  379-384.  doi:10.3969/j.issn.0255-8297.2014.04.007

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Coherent optical communication attracts research interest due to its high detecting sensitivity.However, its application is limited by factors such as practical implementation. This paper presents a new heterodyne detection method that realizes frequency mixing of the sender subcarrier and the receiver subcarrier
to improve detection sensitivity of the wireless laser communication system. The experimental results show that the subcarrier modulation/non-optical heterodyne detection system has nearly 20 dB heterodyne gain and better error rate than direct detection.

Design of Block Diagonalization Precoding in Multi-cell Multi-user MIMO Network Using Channel Projection

YANG Ding-cheng1, HE Hao2

2014, 32(4):  385-393.  doi:10.3969/j.issn.0255-8297.2014.04.008

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In this paper, an optimal precoding is designed for multi-cell multi-user MIMO networks. It is proposed to expand a block diagonalization method of single cell to the multi-cell situation. Considering interference leakage to out-of-cell users, a channel projection based block diagonalization (BD) method is used in designing the precoding. Using the extra-space freedom degree offered on the transmitting side, the transmit signal is preprocessed with a cell-based signal-to-leakage-plus-noise ratio (SLNR) maximization criterion, which can compromise the target user signal and leakage interference to suppressed interference. Moreover, a traditional subspace zero forcing procedure is proceeded to mitigate the interference among intra-cell users. Thus,
negative factors of the inter-cell interference for the multi-user MIMO system can be suppressed. Compared to the classical interference leakage zero forcing algorithm, it can flexibly adjust the freedom for inter-cell interference suppression, balance relationship between interference suppression and system capacity enhancement. Moreover, under the same interference, the capacity can be doubled. Both theoretical analysis and simulation
indicate that the proposed methods can efficiently suppress interference while keeping low complexity without changing topology of the current systems.

Signal and Information Processing

Chlorophyll Content Retrieval of Rice Canopy with Hyperspectral Inversion Based on Rough Set Reduction

BI Jing-zhi1, LIU Xiang-nan1, ZHAO Dong2

2014, 32(4):  394-400.  doi:10.3969/j.issn.0255-8297.2014.04.009

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The rice canopy chlorophyll content can be estimated by using the hyperspectral technique for rice growth monitoring and agronomic decision-making. This paper presents a chlorophyll estimation method based on rough set attribute reduction and support vector regression (SVR) using ground spectral data to solve the problem of data redundancy and low retrieve rate caused by high correlation between vegetation indices. Eighteen hyperspectral indices are selected as variables to estimate the chlorophyll content of rice canopy.The data space is reduced using the rough set algorithm. The SVR algorithm is then introduced to estimate the chlorophyll content. There are six indices reserved in the reduced kernel after attribute reduction. R2 of retrieval results based on all indices and reduced kernel are 0.858 6 and 0.850 6 respectively. The proposed method can achieve an accurate forecasting rate based on all feature attributes, and reduce processing steps and estimation time. It provides a new method for big data processing.

Locating Steganographic Payload by Combining WS Residuals and MAP Cover Estimator

YAN Xiao-meng, ZHANG Tao, LI Wen-xiang, PING Xi-jian

2014, 32(4):  401-408.  doi:10.3969/j.issn.0255-8297.2014.04.010

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 This paper proposes a modified method of payload location aimed at least significant bit replacement (LSB-R) by combining weighed-stego (WS) residuals with maximum a posteriori (MAP) cover estimator.We use the WS residuals to locate payloads, and take the results as a priori information to apply the modified MAP cover estimator to get more accurate cover estimates. The residuals are then computed to locate payloads. Experimental results demonstrate effectiveness of the approach in locating payloads both on JPEGdecompressed images and originally lossless stored images. Furthermore, the proposed approach is suitable for payload location with different embedding rates.

Optimization Estimation for Spaceborne InSAR Baseline Using Quadratic Polynomial

ZHANG Guo1,2, ZHENG Yu-zhi1

2014, 32(4):  409-415.  doi:10.3969/j.issn.0255-8297.2014.04.011

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 Baseline is an important parameter in synthetic aperture radar interferometry (InSAR). Tiny errors in length and inclination of the baseline can cause a great error of the interferometric phase, and eventually affect accuracy of the spatial information. This paper proposes a method to optimize estimation of baseline by using quadratic multi-polynomial aimed at unwrapped phase to eliminate the interferometric phase influence caused by the baseline error. TerraSAR-X, COSMO-SkyMed, RadarSat-2 and ASAR images are used to verify effectiveness of the proposed method.

Pornographic-Image Filtering Based on Body Parts

HUANG Jie, NI Peng-yu

2014, 32(4):  416-422.  doi:10.3969/j.issn.0255-8297.2014.04.012

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Non-pornographic images containing large naked skin or skin-like areas may be detected as pornographic using ordinary pornographic image-filtering method that heavily depend on skin detection. We design a different pornographic image-filtering system based on body parts. The system extracts Haar-like features describing local grayscale distribution of the body parts, and uses these features to train and obtain a classifier for body parts using the Adaboost learning algorithm. The candidate body part areas can be obtained with the classifier. To further improve the system performance, we extract histogram of oriented gradient features,textual features based on gray level co-occurrence matrix, and color moment features of the candidates. These
features are then used to train an support vector machine (SVM) classifier. Experiments show that the system can precisely detect key body parts in images, and therefore can effectively reduce false detection rate against non-pornographic images.

Detection and Recognition of Triangular Traffic Signs in Natural Scenes

JIA Yong-hong1,2, HU Zhi-xiong1, ZHOU Ming-ting1, JI Wei-jun1

2014, 32(4):  423-426.  doi:10.3969/j.issn.0255-8297.2014.04.013

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 An approach is proposed to detect and recognize triangular traffic signs in natural scenes according to color and geometric features of the signs. The sign is first roughly extracted based on color segmentation.A straight line fitting method is used to detect the three sides of the triangular signs to obtain the complete triangular sign. A partitioning feature method is used to obtain feature vectors from all reference triangular traffic signs as well as the detected ones, then the detected triangular traffic sign is recognized by feature vector matching. Experimental results show that the proposed method is effective for recognizing triangular traffic signs in natural scenes.

Dual Thresholding Method Using Fuzzy Entropy and Genetic Algorithm

ZHENG Yi1,2, ZHENG Ping3,4

2014, 32(4):  427-433.  doi:10.3969/j.issn.0255-8297.2014.04.014

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 A dual thresholding method is proposed to extract a calibration pattern and a laser spot from a target image simultaneously in a gun barrel camber measurement system. Based on the fuzzy mathematics theoryand a maximum fuzzy entropy criterion, the proposed method can classify the target image into three fuzzysubsets, namely, dark, gray and bright fuzzy subset by their gray levels. Gray levels of the calibration pattern used for distortion correction belong to the dark fuzzy subset, and the ones of the laser spot for measurement belong to the bright fuzzy subset. An improved fuzzy exponential entropy is used as the classification criterion,which can increase classification accuracy. A genetic algorithm is implemented to search for an optimal combination of fuzzy entropy parameters, which has a low computational complexity. There are only four fuzzy entropy parameters in the proposed method, and the search space is small. The proposed method is tested and compared with an Otsu’s dual thresholding method, a dual thresholding method using fuzzy entropy and simulated annealing algorithm, and a dual thresholding method using unimproved fuzzy exponential entropy and genetic algorithm. Experimental results show that the proposed method can determine dual thresholds automatically and efficiently, and has the best segmentation among the tested methods.

Audio Watermarking against Synchronization Attacks Using Statistical Features

XIANG Shi-jun, HUO Yong-jin, LIU Shang-yi, LUO Xin-rong

2014, 32(4):  434-440.  doi:10.3969/j.issn.0255-8297.2014.04.015

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This paper proposes a robust audio watermarking approach against random cropping and timescale modifications (TSM) by using two local statistical features. In the embedding, audio signals are divided into segments, and histogram and the absolute mean value of each segment computed. The histogram shapes of the segments are modified to insert messages by referring to the corresponding mean values. Theoretical analysis and experimental results show that the proposed audio watermarking algorithm can provide better performance for random cropping while keeping satisfactory robustness to the TSM attacks in comparison with earlier methods.