Table of Content

25 November 2009, Volume 27 Issue 6

Previous Issue    Next Issue

Communication Engineering

Selection of Sensing Node Set in Cognitive Radio Based on Degree of Confidence

ZHANG Xiao, WANG Jin-long, WU Qi-hui

2009, 27(6):  551-556. 

Asbtract ( 1675 )   PDF (569KB) ( 1837 )  

Related Articles | Metrics

Although collaborative spectrum sensing can greatly improve sensing performance, transmission efficiency
will decrease with the number of sensing nodes that consume more system resources. The sensing performance of
collaborative spectrum sensing is investigated, and relationship among the performance, node number and average
signal-to-noise ratio derived. Based on the study, a method for selecting a set of sensing nodes is proposed. A
method for determination of the confidence degree is presented to eliminate trustless nodes in the cognitive radio
(CR) network, which adds negative effect to the selection method. Using the above two methods, an algorithm for
selecting sensing node set based on confidence is proposed, which can effectively eliminate trustless nodes in the CR
network and guarantee the sensing performance of the set. Simulation results show validity and reliability of the
algorithm.

Performance of MIMO-MRC Systems in Special Non-Rayleigh Channels with Spatial Correlation

ZHANG Wei-jiong, GUAN Zhang-jun, ZHOU Xi-lang

2009, 27(6):  557-562. 

Asbtract ( 1798 )   PDF (952KB) ( 1828 )  

Related Articles | Metrics

A method to analyze performance of MIMO-MRC systems in correlated Rician channels with lower
Rician factor is presented based on the property of complex hypergeometric functions of matrix arguments. By
the upper bound for the joint density of ordered eigenvalues of a complex non-central Wishart matrix, approximate
density of its maximal eigenvalue can be derived. Closed-form expressions for the outage capacity, mean SNR and
error symbol rate of a MIMO-MRC system in such a Rician channel with correlation at the transmitter are obtained.
Furthermore, closed-form expressions for density and mean of SNR of a MIMO-MRC system in Nakagami lock hole
channel with correlation at the transmitter are also given. Compared with the previously reported results, the
derived formulas are easy to computer. Numerical results verify the accuracy of the derived expressions.

Analysis of S-MAC Protocol with Hidden Terminals

CHEN Hao, YAO Guo-liang, LIU Hao

2009, 27(6):  563-568. 

Asbtract ( 1761 )   PDF (621KB) ( 1487 )  

Related Articles | Metrics

 This paper proposes an analytical model that allows the influence of hidden terminals on the performance
of S-MAC protocol to be assessed. The model is used to analyze the impact of the number of hidden terminals on
the service delay and throughput of the MAC layer. Analysis results show that the more the hidden terminals, the
rapidly the service delay increases. Besides, increasing the number of hidden terminals lowers the load, leading to
early occurrence of the saturation regime and increase of the saturation delay value. Simulation results based on
ns-2 show good agreements with the analytical results, validating accuracy of the model.

Modified Stochastic Model of Aeronautical Channel

ZHU Qiu-ming1, XU Da-zhuan1, Lü Wei-hua2, CHEN Xiao-min1

2009, 27(6):  569-573. 

Asbtract ( 1706 )   PDF (612KB) ( 2328 )  

Related Articles | Metrics

The sum-of-sinusoids (SoS) method has been widely used for creating complex Gaussian processes.
Restriction of each echo’s Doppler frequency is proved, which confirms the generated processes are mutually uncorrelated
and have a part of U shaped Doppler power spectrum (DPS). An improved SoS method based on optimal
angle of arrival (AoA) is then proposed. The optimal AoA consists of a deterministic part and a random part.
This confirms that the uniform distribution of phase and the Doppler frequency meet the restrictions. With the
new method and the equivalent discrete-time model, a modified aeronautical channel model for small-scale fading
is presented. Analysis and simulation results show that the DPS and time delay power spectrum of the simulation
model as agree with the reference model.

Signal and Information Processing

Automatic Tracking of Soil Using Digital Image Correlation

WANG Wei1;2, HE Xiao-yuan2, MENG Yun-mei1

2009, 27(6):  574-579. 

Asbtract ( 1532 )   PDF (2391KB) ( 1438 )  

Related Articles | Metrics

In order to explore the dynamic evolution law of soil microstructures in real time, image correlation,
matching template and search region adapted to the automatic tracking system are studied towards moving features
of soil particles under loadings. It is vital to satisfy the real-time requirement and accuracy performance of the
tracking system. By analyzing calculation time, kurtosis and statistical distribution of four types of correlation
coefficients, we propose to use the square relation instead of the traditional cubic formula. The rectangular template
and search region are used to replace the square template and search region to take advantage of the template’s gray
information and meet the real-time requirement. Experimental results show that the automatic tracking system is
reliable, which provides an experimental means for the research of continuous deformation in the soil microstructure.

Three Dimension Localization of Non-wearable Pointing Arm

GUAN Ye-peng1;2

2009, 27(6):  580-585. 

Asbtract ( 1560 )   PDF (10286KB) ( 1324 )  

Related Articles | Metrics

 As the wavelet transform has outstanding local characteristics both in temporal and spatial domains,
moving objects are extracted based on background subtraction using wavelet multi-scale transform. According to the
relative spatial position of pointing arm finger in a 2D image, a method for the extraction of pointing arm region is
developed based on fusion of threshold segmentation and color information. In processing the correspondence problem
of finger tip pointing, a stereo matching technique is used based on geometric constraints among the pointing arm
finger tip, central axis of the pointing arm, and the corresponding epipolar line. Reverse correspondence is adopted
to ensure validity of the processed correspondence. Experimental results show that the described algorithm is robust
and 3D information of the pointing arm can be determined efficiently.

Measurement and Comparison of Noise Characteristics of Subway Railcar Wheels with Different Structures

TANG Hua-ping, DU Lei, JIANG Yong-zheng, HAO Chang-qian

2009, 27(6):  586-591. 

Asbtract ( 1902 )   PDF (606KB) ( 1668 )  

Related Articles | Metrics

Strict requirements of low-noise produced by subway railcars call for quantitative evaluation of the
acoustic characteristics of the wheels. The evaluation method should be easy, practical and persuasive. Measurements
are made on noise characteristics of subway railcar wheels with three different structures and excited in different
directions. Coefficients of radiation and attenuation are studied. Based on the comparison and analysis, conclusions
are reached that wheels with straight radial plate and retarding disc is the best in terms of acoustics. This type of
wheels produces low radiation of noise and fast attenuation. This study provides an experimental foundation to the
development of low noise urban railcars.

Optimal Closed-Form Solution to Array Error Matrix Based on Eigenvector

WANG Ding1, LI Chang-sheng2, WU Ying1

2009, 27(6):  592-600. 

Asbtract ( 1633 )   PDF (653KB) ( 1825 )  

Related Articles | Metrics

The combined effects of mutual coupling and amplitude-phase errors have negative impact on the
direction-finding performance of the MUSIC algorithm. In this work, we calibrate array errors induced by the mutual
coupling effect and amplitude-phase errors. Three algorithms are presented, which have the same computational
mode and theoretical framework, and provide optimal closed-form solutions to the array error matrix based on the
eigenvector of the Hermite matrix corresponding to the smallest eigenvalue. The first algorithm does not make
use of any property of the array error matrix, the second uses sparseness of the array error matrix, and the third
makes fully use of the special structure of the array error matrix for some regular arrays. Performances of parameter
estimation of the three algorithms are compared by simulation. The results show that the calibration precision of
array error matrix can be improved if the algorithm uses more special properties of the array error matrix.

Prediction of Protein-Protein Interactions with Sequence Coding

QIN Dian-gang, GAO Song, FENG Tie-nan, MA Cheng-rong, WANG Yi-fei

2009, 27(6):  601-605. 

Asbtract ( 1827 )   PDF (564KB) ( 1971 )  

Related Articles | Metrics

Support vector machine is used to predict protein-protein interaction of Homo sapiens through the
protein’s primary sequence. A conjoint triad feature is used to describe amino acids. Experimental results show that
the method can predict PPIs with high accuracy. The predicted results of two classifications of Cys are compared.
The PPI network of human fetal liver is predicted, which supplies important information for experiments.

Electronic Engineering

Far Field Measurement for Spatial Polarization Characteristics of Antenna

DAI Huan-yao, LIU Yong, LI Yong-zhen, WANG Xue-song, XIAO Shun-ping

2009, 27(6):  606-611. 

Asbtract ( 1471 )   PDF (687KB) ( 1346 )  

Related Articles | Metrics

 Measurement of far-field of antenna is studied in this paper. The proposed method introduces a metallic
ball and a dihedral calibrator as radar target for observation. A model is built for the signal received from the
antenna that scans the target. A measurement equation for the antenna polarization characteristic is derived. By
processing and solving the echo-voltage samples, the polarization characteristics of the antenna are obtained. The
analytical expression and practical procedure are presented. Validity of the method is shown by processing of the
observation data and simulation. The method can greatly reduce the development complexity and production cost
of the field test, and increase fidelity of the predicted far field.

 Realization of Miniaturization and Band Broadening of Lowpass Filter Using SIR Open-Stub

WANG Hua-hong, YANG Xue-xia, GAO Yan-yan, SUN Xiao-meng

2009, 27(6):  612-615. 

Asbtract ( 2044 )   PDF (627KB) ( 2108 )  

Related Articles | Metrics

A novel two-order lowpass filter with a stepped impedance resonator (SIR) open-stub is proposed. The
filter improves performance of out-band rejection and cutoff frequency response by using an SIR open-stub, having
advantages of low loss, wide stop band and compact structure. The measured insertion loss in pass band is below
?0.3 dB and the rejection bandwidth at insertion loss greater than 15 dB is 9 GHz. The measured 3 dB cutoff
frequency of the two-order lowpass filter is 7.2 GHz in the pass band. It can be widely used in various microwave
systems. Circuit simulation results, EM simulation, and experimental results of the two-order lowpass filter are in
good agreement, showing feasibility of the lumped-element equivalent circuit. In order to broaden stop band and
suppress high order spurious signals, a three-order lowpass filter loaded with open SIR-stub and reverse T-stub is
also proposed.

Fitting of Non-linear Relation of Temperature Sensor and Reference Temperature Compensation Based on LS-SVM

SUN Lin1, YANG Shi-yuan2

2009, 27(6):  616-622. 

Asbtract ( 1736 )   PDF (620KB) ( 2200 )  

Related Articles | Metrics

 This paper proposes a model to fit the non-linear relation of temperature sensor based on least square
support vector machine (LS-SVM), and presents two design schemes to compensate temperature of reference point
according to the sensor’s input/output characteristics. An LS-SVM regression model is set up, which takes advantage
of the super learning capacity of LS-SVM to precisely fit the non-linear relation between temperature and voltage.
Both schemes can effectively compensate reference point temperature. The second scheme can directly fit the actual
temperature in accordance with the reference temperature and the actual measuring voltage of the sensor, simplifying
the compensation and enhancing recognition precision. Experiments show that the LS-SVM regressing method and
the proposed compensation method can fit the actual temperature and enhance measuring precision.

Computer Science and Applications

Implementation of Software-Controllable Cache for Embedded Systems

LIU Bo, WANG Xue-xiang, SHI Long-xing

2009, 27(6):  623-629. 

Asbtract ( 1694 )   PDF (590KB) ( 1968 )  

Related Articles | Metrics

Recent researches show that traditional hardware-only cache replacement strategies seriously hamper the
improvement of cache performance. This paper proposes a novel scheme of software-controllable cache for embedded
systems. In this scheme, a software-controller module is added to the traditional architecture to implement the
following three operations controlled by software: For data that incur heavy access cost and have a wide activity
space, a copy is retained in the cache. Data that cause a drop in the cache pre-fetching temporal locality are directly
exchanged between the processor and the external memory. Data with less access cost and a narrow activity space
preferentially remain in the cache during activities. Simulation results show that the proposed approach can improve
the system performance by 11% and reduce bus occupancy by 28%.

Improved Model for Concept Similarity Evaluation with High
Precision for Single Ontology

PAN Yue-jian, WANG Li-song

2009, 27(6):  630-636. 

Asbtract ( 1756 )   PDF (615KB) ( 1871 )  

Related Articles | Metrics

Concept similarity evaluation is widely used in concept classification, concept gathering and concept
merging. Previous single-ontology-oriented models were centered on matched concept characteristics and semantic
analysis. Since they did not take enough factors into consideration, the obtained results were inaccurate, therefore
of less value for exploring relations among concepts. This paper makes the matched concept characteristics more
complete, takes characteristics which are not processed among concepts as similarity, assigns different weights according
to the semantic hierarchy of the concepts, and proposes an improved concept similarity calculation model
with high precision. Experimental results show that the improved model is more accurate.

Virtual Prototyping Platform for Flight Control of UAV

HE Huo-jun1, CAO Yun-feng1;2, LIU Xing-hua1

2009, 27(6):  637-643. 

Asbtract ( 2198 )   PDF (989KB) ( 2517 )  

Related Articles | Metrics

In order to shorten the research and design period and reduce cost of UAV flight control system (FCS)
incurred by physical prototyping so as to enhance efficiency of UAV FCS, a virtual prototype platform (VPP) of
UAV FCS is studied. Guided by the idea of model-driven and using an iterative and incremental approach, we
propose a scheme for designing UAV flight control system on the VPP. The VPP is established using Rhapsody,
Simulink and VC++, on which some type of UAV FCS is designed and tested. It is shown that VPP can be used
to design the virtual prototype in the UAV flight control system quickly and efficiently, better than that of physical
prototyping in some way.

Control and System

Data Mining for Airport Emergency Rescue Decision-Making Rule Controlled by Satisfaction Degree

JIANG Jing-yi1, HAN Song-chen1, TANG Xin-min1, NI Jin-xia1, CUI Guo-shan2

2009, 27(6):  644-650. 

Asbtract ( 1523 )   PDF (587KB) ( 1419 )  

Related Articles | Metrics

The scale of decision-making in airport emergency rescue operations is extremely important to save
people and properties. In view of the current absence of reasonable rules for the rescue scale decision-making, a data
mining method based on the satisfaction control is proposed. The selection and rejection functions of the satisfaction
theory are planted into the association rule algorithm in the data mining. It tries to identify abnormal data while
keeps integrity of the samples, and controls the mining process. An effective rule base of the airport emergency
rescue is established to assist decision-making, which can help the decision maker make a more reasonable decision.
Experiment result shows that the proposed method provides reasonable rules for the emergency rescue scale decisionmaking,
and improves accuracy and efficiency of the data mining.

Neural Network-Based Sliding Mode Control for Satellite Formation Flying

GAO You-tao1, LU Yu-ping1;2, XU Bo2

2009, 27(6):  651-656. 

Asbtract ( 2112 )   PDF (661KB) ( 1547 )  

Related Articles | Metrics

The general dynamical model of satellite formation flying is derived. A sliding mode control method
based on neural networks is proposed to improve control accuracy and robustness of satellite formation flying. A
neural network based on radial basis function is designed to modify the parameters of exponent reaching law in
order to get an optimal balance between convergence speed of the sliding quantity and fuel consumption. Exponent
reaching law with saturation function is used to weaken chattering actuated by un-modeled dynamics and high
frequency switching control. The second order sliding quantity of the relative position error is used to improve the
control accuracy. Simulation results show effectiveness of the neural network-based sliding mode control method.

Parameter Design and Characteristic Analysis for Three-Phase AC Active Magnetic Bearing

ZHU De-hong, CHENG Xin, ZHU Huang-qiu

2009, 27(6):  657-660. 

Asbtract ( 1640 )   PDF (650KB) ( 1579 )  

Related Articles | Metrics

 A mathematical model of the suspension forces is established for three-phase inverter-fed AC radial
magnetic bearings. According to the requirement the suspension forces, parameters of an experimental prototype
are calculated. The magnetic field and suspension forces of the rotor are verified using Ansoft. Nonlinearity of
the suspension forces and the coupling characteristics of the movement between two degrees of freedom around the
balance position are calculated and analyzed. The results show that the mechanical configuration and magnetic
circuits of the magnetic bearing are correct, and the suspension magnetic forces satisfy the design requirement.
Suspension forces have good linearity and symmetry around the balance position, and the movement of two degrees
of freedom around balance position has no coupling.