Table of Content

25 March 2014, Volume 32 Issue 2

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Communication Engineering

Opportunistic Interference Alignment with Optimal Capacity in Cognitive Networks

AN Yong-li1,2, XIAO Yang1, QU Guang-zhi3

2014, 32(2):  111-118.  doi:10.3969/j.issn.0255-8297.2014.02.001

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 Cognitive users can only access idle bandwidth in traditional cognitive networks, but they cannot share the same bandwidth with the primary user simultaneously. In order to make full use of the spectrum, we propose a capacity optimal opportunistic interference alignment algorithm. By ensuring the channel capacity of primary users, cognitive users and primary users can share the same bandwidth, and the cognitive users cause no interference to the primary user. In the proposed algorithm, the hybrid network base station estimates channel state information and calculates channel capacity. It then determines the pre-coding vectors and decoding vectors according to the capacity optimal rule. Cognitive users access the networks by capacity optimal opportunistic interference alignment when the primary user’s channel capacity almost does not decline and the whole network can still obtain good channel capacity. Simulation results show that the proposed algorithm can obtain greater channel capacity and increase the utilization ratio of spectrum than other existing algorithms under the same condition of channel state information.

Optimal Relay Function and Achievable Secrecy Rate in Orthogonal Relay-Eavesdropper Channel

CHEN Chi-yang1,2, DENG Zhi-xiang1, WANG Bao-yun2,3

2014, 32(2):  119-124.  doi:10.3969/j.issn.0255-8297.2014.02.002

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In this paper, secret communication in an orthogonal relay-eavesdropper channel is studied in view of information-theoretical security. For an orthogonal relay-eavesdropper channel with instantaneous relay in which the present output depends only on the currently received signal, the achievable secrecy rate is
formulated. The achievable secrecy rate with piecewise linear(PL) relaying function is derived and computed numerically. A sub-optimal solution to this secrecy rate is obtained by optimizing the parameters of the piecewise linear function with an iterative grid search algorithm. The achievable secrecy rate with PL relaying is compared to that with amplify-and-forward (AF) relaying and decode-and-forward (DF) relaying by simulation. The results show that PL always outperforms AF, and outperforms DF when the source-relay link is poor. Meanwhile, compared with DF, PL relaying has lower complexity and lower time-delay.

Pipelined RFID Indoor Positioning Based on Locally-Weighted Regression

ZHANG Jin-yi1,2,3, ZHANG Jing-jing1, LI Ruo-han1, XU De-zheng2, XU Qin-le2

2014, 32(2):  125-132.  doi:10.3969/j.issn.0255-8297.2014.02.003

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Radio frequency identification (RFID) is a hot research topic for indoor positioning because it is non-contact and non-line-of-sight with low-cost and high-precision. This paper proposes to use the pipelined packet reception rate as the positioning parameters to enhance stability and improve real-time performance.To deal with the indoor environmental impact on the signal propagation, the pipelined positioning algorithm uses locally weighted regression, which takes full advantage of the indoor environment information to achieve precise positioning. Experimental results show that, for indoor applications, the proposed algorithm increases the positioning accuracy by 56.56% compared with LANDMARK and by 36.73% compared with VIRE. The method can also obtain precise real-time tracking results for multiple targets, showing its practical value and wide range of applications.

Signal and Information Processing

Radar Super-Resolution Imaging Based on Compressive Sensing

DENG Zhen-miao, YE Lin-mei, FU Mao-zhong, ZHANG Yi-xiong

2014, 32(2):  133-140.  doi:10.3969/j.issn.0255-8297.2014.02.004

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Application of compressed sensing (CS) in inverse synthetic aperture radar is investigated in this paper. The radar transmits sparse probing pulses and dechirped radar echo samples that satisfy the Nyquist sampling theorem are resampled sparsely. Reconstruction is performed to these sparse samples both in range and cross-range directions to recover the whole radar echo signals containing the target characteristics. To obtain high resolution ISAR images, super-resolution processing on both range and cross-range directions is conducted on the reconstructed data. Results of processing on real radar data and simulated data show that the resolution of ISAR image can be enhanced significantly. The proposed algorithm can reduce data size and
time consumption, and is valuable for super-resolution radar image applications.

Passive Multistatic Radar Imaging Based on Compressed Sensing Joint Sparse Aperture Autofocusing

WU Hao, SU Wei-min, GU Hong

2014, 32(2):  141-148.  doi:10.3969/j.issn.0255-8297.2014.02.005

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In this paper, passive multistatic radar imaging based on compressed sensing joint sparse aperture autofocus is presented. The method uses a point spread function of the different opportunistic illuminator to construct a reasonable sparse basis matrix, and turns the point-enhanced problem into an optimization problem by using the lp norm method. Meanwhile an optimization problem in terms of phase error is established. The quasi-Newton method with a phase error update scheme is used to obtain the increment of phase error. The simulation shows good performance of this method at small rotating angle and in the presence of phase error.

Keyword Detection Based on Dynamic Match Lattice Spotting

ZHENG Yong-jun, ZHANG Lian-hai

2014, 32(2):  149-155.  doi:10.3969/j.issn.0255-8297.2014.02.006

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The large amount of speech data requires techniques for rapid and accurate search. This paper proposes a keyword spotting method based on dynamic match Lattice spotting (DMLS). It generates more accurate phone Lattice with TRAP features and multilayer perceptron, and performs a modified Viterbi traversal to compile a database of fixed-length phone sequences in speech indexing. In the searching stage, a minimum edit distance is used as the confidence score to implement the keyword spotting. Tests show that the proposed method is superior to baseline systems with MFCC and PLP features with the recall rate improved by about 5%.

Impact of Random Delays in Control and Measurement Signals on Iterative Learning Control Systems

HUANG Li-xun, FANG Yong

2014, 32(2):  156-162.  doi:10.3969/j.issn.0255-8297.2014.02.007

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 Random delays of control and measurement signals during transmission over wireless network seriously affect the convergence performance of iterative learning control (ILC) systems. Based on a one-step random delay model, the transition matrix of system is derived, which contains the impact factors of random delays. For different situations of random delays, variation of eigenvalues and other elements in the lower triangular of transition matrix is analyzed, which determine the convergence speed and robust convergence respectively. Analysis shows that the convergence rate is reduced, and the robust convergence is also affected. Especially, the impact of control signal delays on robust convergence is greater than that of measurement signal
delays. Simulation results are provided to demonstrate correctness of the conclusion.  

Atom Set Calibration and Step Control for Unknown-Sparsity Reconstruction from Compressive Sensing

ZENG Chun-yan1,2, MA Li-hong1, DU Ming-hui1

2014, 32(2):  163-169.  doi:10.3969/j.issn.0255-8297.2014.02.008

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This paper models residual signals with Gaussian-like distributions, based on which consistency between the Backtracking-based adaptive orthogonal matching pursuit (BAOMP) threshold and signal sparselevel is analyzed. An improved BAOMP (IBAOMP) method is thenproposed. Themethod estimates the
preliminary matching state usingthe 80-20 rule, and introduces a threshold with variable step size to subtly adjust atom set to raise the correct rate of selected atoms and avoid quasi-periodic mismatches of residual signals. Simulation results of 500 tests show that the exact recovery probability of IBAOMP is 17%-26% higher than BAOMP for Gaussian sparse signals, and more than70% higher than BAOMP for natural images.

Micro-Doppler Modeling and Signature Extraction of Trucks

LI Kai-ming1, ZHANG Qun1,2, LIANG Bi-shuai1, LUO Ying1

2014, 32(2):  170-177.  doi:10.3969/j.issn.0255-8297.2014.02.009

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 Based on a three-dimensional scatterer model, the echo from a truck is modeled under narrowband chirp signal system. Mathematical representations of the Doppler generated by bulk scatterers and micro-Doppler due to the rotating scatterers on the hub are analyzed and derived. A dictionary is designed
in terms of their differences. Meanwhile, a threshold of energy in slow time-range plane is set, which is useful in the extraction of echoes in energy-centralized range cells. Matching pursuit can be implemented by decomposing the echoes into corresponding atoms. Fast extraction of micro-Doppler signature of wheel rotation is accomplished. These provide references for truck recognition. Effectiveness and robustness of the method are shown by the simulation results.

Self-Embedding Based on Saliency Distribution

ZHAO Li-li, QIAN Zhen-xing, HAN Xi-yu

2014, 32(2):  178-184.  doi:10.3969/j.issn.0255-8297.2014.02.010

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 The purpose of image self-embedding is to achieve content authentication and self-recovery by imperceptibly embedding relevant information into the host image. This paper proposes a novel self-embedding method based on significance classification. After classifying the image into three kinds of regions dynamically, the code length and embedding capacity of each block are determined. Using fountain coding, the reference information is embedded into the entire image. The proposed method is superior to the traditional methods in two aspects. First, the method assigns different code length to different regions so that the recovery quality for the whole image is good and significant regions can be protected effectively. Second, the method embeds different amounts of data into different regions thus avoiding false contour and ensuring good quality of the stego-image.

Object-Scene Fusion by Combining SFIM with Region Filling

2014, 32(2):  185-190.  doi:10.3969/j.issn.0255-8297.2014.02.011

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Considering the drawbacks of the Poisson fusion technique and an existing object-scene fusion method based on IHS transform, this paper proposes an improved scheme by combining smoothing filterbased intensity modulation (SFIM) with region filling making use of the advantages of IHS transform. The
scheme reduces color distortion in fusion of object and scene by introducing the SFIM technique. With the hue and saturation filling, it can also fix the problems that the detail recovery cannot be increased effectively to let object get enough fusion illumination so that the object may appear inconsistent in illumination. Both subjective and objective quality assessments show that the proposed scheme can solve the above-mentioned problems. It is fast and more robust.

Fast Inpainting of Railway Freights Images Based on Multiple Direction Interpolation

金星1， 俞大海1,2， 韩建枫3， 李晖晖1， 韩军伟1

2014, 32(2):  191-198.  doi:10.3969/j.issn.0255-8297.2014.02.012

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High resolution line-scan cameras produce images with missing information due to occlusion caused by foreign objects. In this paper, we propose a framework based on multiple direction interpolation for single image digital restoration to remove high tension wire (HTW) from images for railway loaded condition inspection (LCI) applications. The known region to be reconstructed is automatically segmented into smooth and edge sub-regions. The smooth regions are filled-in with bilinear interpolation based on the information in the neighborhood, which is the minimum among the gradient values in three directions. For the edge regions,the fill-in result is optimized using a data fusion method based on the information in three directions with bi-cubic interpolation. Inpainting is performed for each channel independently based on the HSI color space instead of RGB. Experimental results indicate that better restoration results can be obtained as compared with traditional Bertalmio-Sapiro-Caselles-Bellester (BSCB) and fast marching method (FMM) algorithms. The proposed algorithm can also effectively deal with inpainting of complex color images with high computational efficiency.  

Electronic Engineering

Application of Optimized Circuit Simulation—Identification of Isomorphic Hybrid Switching

SHANG Hui-liang1, LIU Yang1, LIU Zhi-dong1, DONG Wen-jie2, LI Feng1

2014, 32(2):  199-208.  doi:10.3969/j.issn.0255-8297.2014.02.013

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This paper presents a new method for graph isomorphism identification and applies it to the identification of isomorphic hybrid switching topology. A mathematical model of hybrid switching topology is first introduced. The adjacency matrix and undirected-weighted graph description of the hybrid switching
topology are presented according to the mathematical model. In this case, the problem of identifying isomorphic hybrid switching topology is transformed into isomorphism determination of the corresponding undirectedweighted graphs. An optimized version of the circuit simulation method previously presented by the authors is proposed to solve the graph isomorphism determination problem. With a small modification, the optimized circuit simulation method can solve the problem of graph isomorphism determination more efficiently. Tests of the proposed method and another method called the eigenvalue algorithm are applied in the identification of isomorphic hybrid switching topology. The results show that the optimized circuit simulation method is valid and has advantages in both identification efficiency and ability of matching corresponding vertices of the isomorphic hybrid switching topology.

Breakdown Model of RESURF Lateral Power Devices Based on Charge-Sharing Effect

ZHANG Jun, GUO Yu-feng, HUANG Shi, YAO Jia-fei, LIN Hong, XIAO Jian

2014, 32(2):  209-214.  doi:10.3969/j.issn.0255-8297.2014.02.014

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A breakdown model for RESURF lateral power device is developed. Based on the analysis of the breakdown mechanism in RESURF lateral power device, charges in the drift region are allocated to lateral and vertical junctions along the diagonal of the sharing area. This model can be used to investigate breakdown characteristics of the device when the drift region is fully or partially depleted. Besides, the model provides simple expressions with clear physical concepts. A new RESURF criterion is also derived to quantitate the upper and lower limits, which is useful to the design of the structure parameters. General agreements exist between the modeling results and the reported experimental results.

SIR Cross-Coupling Dual-Band Cavity Filter

KOU Xin, XIAO Zhong-yin, HUANG Chun-yan, LI Hao, CHU Jun-jun

2014, 32(2):  215-220.  doi:10.3969/j.issn.0255-8297.2014.02.015

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Using stepped impedance resonators (SIR) as a basic resonator unit of cavity filter, a cross-coupling dual-band cavity filter is designed based on frequency transformation. According to the filter specifications,the design parameters of dual-band filter are calculated using frequency transformation. A model of SIR
cross-coupling dual-band cavity filter is then established and simulated by the 3D simulation software HFSS.Simulation results show good agreement with the result of schematic circuit in ADS, indicating that the method is valid and feasible. The simulation shows that the filter size is significantly reduced, while the restrain ability of stop-band is enhanced due to cross coupling. Thus the requirements of small size and good stop-band performance of the filter are met.