Table of Content

31 January 2013, Volume 31 Issue 1

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Communication Engineering

Demodulation and Mapping Scheme for 2FSK Two-Way Relay Communication Systems with Physical-Layer Network Coding

LI Bo, WANG Gang, YANG Hong-juan, ZHENG Da-guo, ZHANG Xiao-dong

2013, 31(1):  1-6.  doi:10.3969/j.issn.0255-8297.2013.01.001

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A correlative demodulation and mapping scheme is proposed for the relay nodes in 2FSK two-way relay communication systems. The scheme ses superimposed signals with two branches, and samples the discrepancy to make a decision, which may be mapped to a binary bit. The decision thresholds are calculated according to the maximum posterior probability criterion. The relay nodes’ decision error probability and the bit error rate of the entire system are analyzed. Theoretical analysis and simulation results show that the relay nodes’ decision error probability and the system BER of the physical-layer network coding scheme using the proposed demodulation and mapping method are close to those of the traditional scheme and the network coding scheme, but the throughput is higher than the two.

Diversity Performance of Multi-source Multi-relay Cooperative System with Linear Network Coding

ZHANG Hai-chao, LI Hui, DAI Xu-chu,

2013, 31(1):  7-14.  doi:10.3969/j.issn.0255-8297.2013.01.002

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To design a linear network code and increase diversity gain of multi-source multi-relay system, this paper investigates relationship between diversity gain and minimum hamming distance of network code, and proposes a method that using minimum hamming distance as the design criterion of linear network code. By using related theories and methods of classic linear block code, an important proposition that system diversity gain is equal to minimum hamming distance is derived. Based on this proposition, the original problem of designing network code is converted to designing classic linear block codes under minimum hamming distance criterion. In addition, based on the singleton bound in the classic coding theory, quantitative relationship between maximum diversity and relay number is obtained. Simulation results show that the diversity gain is improved by increasing the minimum hamming distance and the maximum diversity gain is equal to the total number of relays plus 1.

Electronic Engineering

TPSN Time Synchronization Protocol Based on Pulse Coupling

SHI Chao1, QIU Hong-bing1,2

2013, 31(1):  15-20.  doi:10.3969/j.issn.0255-8297.2013.01.003

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In view of the disadvantage of the traditional timing sync protocol for sensor networks (TPSN), a pulse-coupled time synchronization protocol for sensor networks (P_TPSN) is proposed. P_TPSN is a noninteractive time synchronization scheme based on pulse-coupled synchronization for distributed networks. A network topology is built to ensure that the time information of net nodes of previous hierarchy can be received by the net nodes of posterior hierarchy. After receiving these time information, the net nodes of posterior hierarchy will adjust their time clocks respectively by weighted average of the received time information. This scheme can enhance robustness of distributed wireless networks and has good scalability and quick convergence.
Theoretical analysis and simulation results show that the proposed scheme is effective and feasible. 

Signal and Information Processing

Improvement of Admission Selection for Heterogeneous Wireless Networks

SHI Wen-xiao, LI Na, WANG Ji-hong

2013, 31(1):  21-26.  doi:10.3969/j.issn.0255-8297.2013.01.004

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Abstract: For all IP services, we propose an improved alterable transmission units-based admission selection algorithm in LTE/WiMAX integrated heterogeneous wireless networks. The algorithm uses two-dimensional resource units to calculate system capacity. By introducing load transfer and alterable transmission units,system resources are distributed more reasonably, making the system more effective in serving all IP business.
The algorithm uses the queuing theory to establish a four-dimensional Markov queuing model, and analyze and evaluate the system performance. Simulation results show that, compared with the original admission selection algorithm, the proposed algorithm suits actual networks better, and can significantly reduce blocking rate of non-realtime services and increase the overall resource utilization of the system without affecting the realtime service performance.

SER Analysis for High-Order Modulated Physical Layer Network Coding over AWGN Channels

LI Dan-dan1, XIONG Ke1,2, DU Guan-yao1, ZHANG Yu1, QIU Zheng-ding1

2013, 31(1):  27-33.  doi:10.3969/j.issn.0255-8297.2013.01.005

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We extend the nearest neighbor approximation method and investigate the symbol error rate (SER) over AWGN channels for physical layer network coding with high order modulation. We derive a closed-form expression of PNC’s SER with 8PSK modulation over AWGN channels. We find that, when the power of one source node is fixed, SER of PNC does not monotonously decrease with the increase of the power of the other source node. Simulation results show that the derived SER expression can characterize the SER performance of PNC’s SER with 8PSK modulation over AWGN channels.

Adaptive Feedback Bit Allocation in Distributed Multi-cell Joint Transmission

ZHAI Xu-ming, QIU Ling

2013, 31(1):  34-40.  doi:10.3969/j.issn.0255-8297.2013.01.006

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In this paper, we propose an adaptive feedback bit allocation strategy for distributed multi-cell pre-coding systems with limited feedback. By analyzing the rate loss of multi-cell joint transmission caused by limited feedback, we provide an approximate upper bound as a function of allocated feedback bit for each
channel. Based on this rate loss, an adaptive feedback bit allocation strategy is proposed. The strategy effectively reduces the rate loss due to limited feedback, and thus significantly increases the system rate. Without additional periodical feedback and heavy computation overhead, the proposed strategy is feasible in real systems. Good performance has been shown in simulation.

Performance Analysis Model for IEEE 802.11 Distributed Coordination Function Protocol

ZHONG Ping, SHI Hai-bin, ZHUANG Yu-xiang, SHI Jiang-hong, CHEN Hui-huang

2013, 31(1):  41-47.  doi:10.3969/j.issn.0255-8297.2013.01.007

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This paper proposes an improved two-dimensional Markov chain model for the performance analysis of the IEEE 802.11 DCF protocol. The model is applicable to both saturated and unsaturated traffic conditions. Moreover, it extends the existing models to take into account previously-ignored MAC layer factors such as backoff freezing and limited times of retry. In addition, by deriving the stationary state of the Markov model and considering an M/M/1/K queuing model, we further derive a theoretical model for evaluating performance of the general IEEE 802.11 DCF protocols. Accuracy of the proposed theoretical model is validated with simulation results.

RS Coded EBPSK-MODEM Based on SVM Discrimination

JIN Yi, WU Le-nan, YING Peng-kui, YU Jing

2013, 31(1):  48-52.  doi:10.3969/j.issn.0255-8297.2013.01.008

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Impacting filter can change phase jump of the extended binary phase shift keying (EBPSK) signal into magnitude impact so as to enlarge the difference between waveforms of 0 and 1. To take full advantage of the special filtering mechanism, we design an RS coded EBPSK-MODEM based on the support vector machine (SVM) discrimination. After briefly describing the principle of EBPSK modem, an EBPSK detector model based on SVM is proposed, which uses the classification ability of SVM. Performances of binary phase shift keying (BPSK) and EBPSK are compared, and an RS coded EBPSK modem based on SVM is designed. Simulation results show that, taking bit·s−1/Hz/SNR as an aggregate indicator, EBPSK system outperforms BPSK, and, compared with the RS coded EBPSK modem based on adaptive threshold decision, the proposed SVM-based method can obtain about 1 dB coding gain in AWGN channel at BER of 10−4.

Multi-target Localization for Bistatic MIMO Radar

CHENG Yuan-bing, GU Hong, SU Wei-min

2013, 31(1):  53-58.  doi:10.3969/j.issn.0255-8297.2013.01.009

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To solve the target localization problem in a bistatic multiple-input multiple-output (MIMO) radar, a method based on upper-triangularization of the joint matrix is proposed to estimate the direction of departure (DOD) and direction of arrival (DOA). The angle estimation is first transformed to a joint-matrix
upper-triangularization problem. The extended QZ iteration algorithm is then used to solve the problem. The steering matrices of transmission and receiving are estimated. Thus, the DOD and DOA are recovered by spectrum analysis. The proposed method uses the full information in the matched filter output without the need of two-dimensional search for the spectral peaks. It produces an accurate closed form solution in each iteration. Compared with the existent approaches, the proposed method provides better angle estimation accuracy with the DOD and DOA automatically paired. Effectiveness of the method is shown in simulation.

Performance Analysis of Equal Gain Diversity over Correlated Nakagami Fading Channels

ZHU Qiu-ming, XU Da-zhuan, Lü Wei-hua, CHEN Xiao-min, MENG Tian-zhen, REN Jia-min

2013, 31(1):  59-64.  doi:10.3969/j.issn.0255-8297.2013.01.010

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Since performance of equal gain combination (EGC) over correlated Nakagami fading channels does not have exact closed-form expressions, efficient approximation based on moment matching is proposed in this paper. We approximate the superposed fading distribution of EGC output by a new −μ distribution. Thus the system performances can easily be obtained with the aid of stochastic properties of the −μ random variable. The performances include signal-to-noise ratio (SNR) distribution, outage probability and average error ratio (SER). The method is easy to implement, and the simulation results match the theoretical ones very well. It can be applied to parameter design and performance evaluation of EGC system over various fading channels.

Source Number Estimation by Delay Correlation Preprocessing

SI Wei-jian1, LIN Qing-qing1, PENG Jie2

2013, 31(1):  65-71.  doi:10.3969/j.issn.0255-8297.2013.01.011

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Source number estimation based on information theoretic criteria is ineffective in colored noise field, and the performance of the Gerschgorin radii algorithm may decline under low signal-to-noise ratio conditions. To solve these problems, a method of source number estimation using delay correlation preprocessing is proposed. The delay correlation matrix of all received data is calculated to reduce the influence of noise on the estimation performance. The eigenvectors are then grouped according to the grouping rules so that different kinds of characteristic spaces can be obtained, one containing noise eigenvectors and the other containing both noise and signal eigenvectors. Finally, the delay correlation matrix is projected onto the characteristic spaces,
and thus the source number can be estimated from the projected data. Simulation and measured data show correctness and effectiveness of the algorithm.

Distance-Preserving Color Visualization Model for Hyperspectral Imagery

WANG Li-guo, LIU Dan-feng, ZHAO Liang

2013, 31(1):  72-78.  doi:10.3969/j.issn.0255-8297.2013.01.012

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 A color display model of hyperspectral imagery is proposed, which optimizes high dimensional hyperspectral images nonlinearly into a three-dimensional color space. The property of spectral distance preserving in the model is considered as a main design criterion, and good separability is guaranteed in the
final visualized color images so that the range difference between pixels and the range difference between the spectra are highly correlated. The method consists of four parts: 1) End-members are reduced to a two dimensional space as chromaticity coordinates. 2) Optimization of brightness values in the third dimension maximizes the relevance, thus color labels of each end-member are determined. 3) Linear mixing of colors are implemented in accordance with the various abundance value of each pixel. 4) A local optimization method is used to optimize and correct the color image to achieve color display of the image. Experiments show that the proposed model is feasible as the final color images have good visual quality with spectral distance well preserved and separable. It is suitable for HSI visual display.

GIS-Constrained Multi-scale Coastal SAR Image Segmentation

ZHU Jun-jie1,2, DU Xiao-ping1,2, FAN Xiang-tao1,2, GUO Hua-dong1,2

2013, 31(1):  79-83.  doi:10.3969/j.issn.0255-8297.2013.01.013

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Both geographic information system (GIS) data and remote sensing imagery are spatial data with multi-scale features although they are concerned with different types of information. This paper discusses the multi-scale segmentation of high-resolution synthetic aperture radar (SAR) images near coastal zones constrained by GIS vector data. To obtain the first level segmentation results at the county-level scale, the high-resolution SAR image is segmented using the fractal network evolution method with the constraint of GIS data. Then, at the province-level scale, the first level results are aggregated to obtain the second level segmentation results. This segmentation results satisfy both the constraint of GIS vector data and the scattering characteristics of SAR images. False coastlines in the SAR images are eliminated. Experimental results show that the proposed method is effective, and the segmentation results can be used for further image statistics and analyses.

Shape Prior Extraction Based on 2DPCA Training

CHEN Bo, CAI Jin-lin, CHEN Wen-sheng, LIU Zhen-he, LI Yan

2013, 31(1):  84-90.  doi:10.3969/j.issn.0255-8297.2013.01.014

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 A shape prior extraction method based on two-dimensional principal component analysis (2DPCA)training is proposed for noisy image segmentation. Some ideal shapes are trained to obtain a group orthonormal projection vectors, and are then spanned to the 2DPCA space. The noisy image is projected onto this space, and least squares method is employed to find a dot nearest the projected dot in this space. The pre-image of this dot may not be one of the training shapes, but a linear combination of them. A pre-image strategy is then exploited to extract the shape prior. Experimental results show that the proposed segmentation method with shape prior is valid not only for noisy images, but also for images with occlusion and massing parts.

Robust Detection of Artificial Circular Target Center

NIE Jian-hui, MA Zi, HU Ying

2013, 31(1):  91-96.  doi:10.3969/j.issn.0255-8297.2013.01.015

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 Detection of artificial circular target center is a key in 3D measurements. In order to get accurate calibration and measurement in industrial fields, a robust algorithm for circular target center detection is proposed. Images with circular target are first preprocessed, and Canny edges extracted. The canny edges
are then refined with an improved Snake algorithm, and sub-pixel edges are found using a Zernike operator. Accurate centers are obtained through robust ellipse fitting. Compared with traditional methods, the proposed algorithm can give accurate center detect results even if the target is damaged or soiled. Simulation results and real data show that the center detection error is less than 0.02 pixel in ideal cases, and less than 0.03 pixel when the target is damaged.

Blind Steganalysis Based on Image Content and Feature Fusion

LI Kan1,2, PING Xi-jian1

2013, 31(1):  97-103.  doi:10.3969/j.issn.0255-8297.2013.01.016

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With increasing research on image feature vector extraction and classification, blind steganalysis is becoming more efficient and accurate. However, many existing methods use similar processing for all images without taking account the diverse image contents. This paper proposes a new approach based on
image contents and feature fusion. The input images are divided into several classes according to the content complexity before feature extraction. Bhattacharyya distance is used to evaluate the usefulness of individual features and determine their weights. Steganalysis is subsequently conducted using a fusing approach and a support vector machine (SVM) classifier in a decision making process. Experimental results on several sets of  images demonstrate that the proposed steganalyzer outperforms some previous methods. It provides reliable results with reduced computational complexity.

Visual Tracking in Crowded Scenes with Multi-part Sparse Representation

SHAO Jie 1, DONG Nan2

2013, 31(1):  104-110.  doi:10.3969/j.issn.0255-8297.2013.01.017

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 This paper presents a target tracking framework applicable to complex crowded scenes with random movements. A robust tracking algorithm using a local sparse appearance model associated with a multi-part color representation is proposed. Sparsity is achieved by solving an l1 regularized least squares problem.Candidates with the smallest projection error is taken as the tracking result. All candidates are drawn based on a density distribution in a Bayesian state inference framework. The target templates are dynamically updated to adapt appearance variation at the end of a tracking iteration. We test the approach on numerous videos including different type of very crowded scenes with serious occlusion and illumination variation. The proposed approach demonstrates excellent performance in comparison with previous methods.