Table of Content

31 May 2007, Volume 25 Issue 3

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Articles

A Handoff Model in Distributed Radio Mobile Communication System

JIANG Zhan-jun;PAN Wen;YOU Xiao-hu

2007, 25(3):  221-221 . 

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A model for RAU selection is presented, in which the active set (AS) is comprised of selected RAUs and serves for the mobile station. Based on this, we propose a handoff model in distributed radio mobile communication system. The received signal strength(RSS) threshold of handoff is controlled by average power of the AS adaptively. Performance analysis shows that numerical data obtained from the model are in good agreement with simulation results.

Hyperparameter Optimization of Fuzzy Hypersphere Support Vector Machine Based on Evidence Framework

JIN Tian;ZHOU Zhi-min;SONG Qian and CHANG Wen-ge

2007, 25(3):  227-227 . 

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Fuzzy hypersphere support vector machine (FHS-SVM) has stronger generalization capability than hyperplane support vector machine in the one-class classification problem, being successful in radar target detection. Some hyperparameters have to be predefined before the FHS-SVM training, with different hyperparameters leading to significant difference in the FHS-SVM performance. In this paper, equivalence between FHS-SVM training and the level 1 Bayesian inference of the evidence framework is proved. Then, an FHS-SVM hyperparameter optimization iteration method is proposed based on the evidence framework. Using landmine detection data obtained with ultra-wide band synthetic aperture radar, the proposed iteration method is verified by comparing it with an exhaustive search method.

A Blind Image Authentication Algorithm Based on Fourier Transform

FANG Yong;ZHANG Jin

2007, 25(3):  233-233 . 

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In this paper, a new blind image authentication method is proposed based on the strip-shaped characteristics in Fourier spectrum of motion pictures. The algorithm implements image authentication and tampering localization for both motion pictures with malicious manipulations and non-motion pictures with motion-picture blocks. Simulation results show effectiveness and robustness of the proposed method.

Non-Wave Approach to Analysis of Received Power Distribution in 2D Wireless Channels

WANG Zheng-bin;HU Luo-quan

2007, 25(3):  239-239 . 

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According to the stochastic ray theory and the percolation lattices theory, power distribution properties in 2D random lattice channels are analyzed based on the Manhattan metric. The approximate formulae under Manhattan metric are derived from rigorous mathematical derivation. Parameters in the formulae have clear physical meanings. Experimental data prove the efficiency of the model.

Speech Enhancement Based on Subspace Method for Narrowband Noise

CHEN Guo－ming;ZHAO Li;ZOU Cai－rong

2007, 25(3):  243-243 . 

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A single channel speech enhancement method for noisy speech signals is proposed based on the subspace method. Conditional subspace based enhancement methods require that the noise covariance matrix is full-ranked. Unfortunately this is not satisfied in case of narrowband noise or tonal noise. The proposed method directly deals with rank-deficient noise using a subspace whitening method. Experimental results demonstrate the effectiveness of the proposed algorithms.

Load Balancing Policy of Distributed CDN Model Based on Performance Measurement

ZHANG Guomin;CHEN Ming;DING Ke;WANG Na

2007, 25(3):  247-247 . 

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In order to make CDN implement real global load balancing based on network and server performance variance and avoid influence of single point failure in server, by borrowing the successful P2P techniques for distributed file sharing and locating, we design a pure distributed CDN model that has no central node. Thus all POP nodes are peers to each other. Key techniques such as load balancing and service locating are then studied in detail. A MBPP algorithm based on the network and service performance measurement is proposed. Scalability and robustness of CDN are improved, and the best service providing point can be located more precisely. Experiments show that, based on MBPP, global real-time dynamic load balance with small communication overhead and computing complexity can be achieved.

Optimization Design for Efficient Computation of Line Spectrum Pairs

LI Juan－juan;YU Yi－biao;RUI Xian－yi

2007, 25(3):  252-252 . 

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This paper proposes a new algorithm APF for calculating line spectrum pairs (LSP) of speech signal. LSP parameters can be obtained by solving an N-order non-linear equation relating to the linear predictive coding (LPC) coefficients. First, one root of the N-order nonlinear equation is derived with the Aitken iterative method. The order is then decreased with polynomial synthesis division. Finally the fourth-order equation is solved using the Ferrari’s solution. Theoretical analysis and experiments on TMS320C5510 DSP show that the proposed algorithm has high precision and low computation complexity, meeting the real-time processing requirement. The algorithm can be applied to low-bit real-time speech coding such as G.729A systems.

Super Resolution Reconstruction of Video Sequence Based on Inter-frame Homography Transform

HAN Yu-bing;SHU Feng;WU Le-nan

2007, 25(3):  257-257 . 

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A super resolution (SR) reconstruction algorithm of video sequence based on inter-frame homography transform is presented in this paper. The mathematical model of SR is introduced using the least square principle. Hierarchical model-based motion estimation is adopted to compute the adjacent homography matrix. For non-adjacent frames, the homography matrix is estimated with guided feature registration based on RANSAC algorithm, which gives sub-pixel accuracy. Finally, a conjugate gradient algorithm is used to reconstruct the SR frames, and computation of matrix-vector multiplication is studied in detail. Experimental results demonstrate effectiveness the proposed method.

Depth Distribution and Period Distribution of Linear Codes on Finite Field

GENG Pu;LI Chao

2007, 25(3):  263-263 . 

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This paper studies the inverse problem of depth distribution of linear codes. We find a linear code whose depth spectrum is just those given natural numbers. We discuss the relation between the depth distribution and the period distribution of linear codes, and the way to find the period distribution from depth distribution is presented

Improving Wireless TCP Performance Based on DSR Route Information Storage

YE Bin;HU Gu－yu;NI Gui-qiang

2007, 25(3):  266-266 . 

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Multipath routing can improve path availability in a mobile environment. Most previous research on multipath routing used UDP traffic for performance evaluation. We find that using multiple paths simultaneously may degrade TCP performance, due basically to frequent out-of-order packet delivery via different paths. This paper proposes a new way of improving wireless TCP performance based on DSR routing protocols through storage route, particularly when the nodes are fast-moving that cause route discontinuity. The sender enters a “frozen” state when packets are lost. Having found that packet drop is caused by route discontinuity, the route information that has been stored is used. This can reduce degradation of the TCP performance due to continual route request. Simulation shows that the proposed approach can significantly improve the TCP performance.

Design and Analysis of A Novel DMS Low-Pass Filter

XUE Yu-jie;YANG Xue-xia;LU Yi-min

2007, 25(3):  272-272 . 

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A novel low-pass filter using defected microstrip structure (DMS) is proposed in this paper. The frequency characteristics of the DMS are simulated with three-dimension electromagnetic field analysis software. Its equivalent circuit and equivalent parameters are extracted with microwave circuit analysis software. Then a novel low-pass filter using DMS is designed and fabricated. The measured 3dB cutoff frequency fc is 3.4GHz with 0.3dB ripple level. The rejection bandwidth of the insertion loss less then ?15dB is 13GHz. The experimental results show good agreement with simulation, validating effectiveness of the equivalent circuit and the realization of the DMS LPF.

A Non-linear Deformable Model for Simulation of Real-Time Soft Tissue Deformation

ZHANG Qiu-kui;LUO Li-min;YANG Wu

2007, 25(3):  276-276 . 

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Real-time simulation of the soft tissue behavior is a major obstacle in developing a virtual surgery system. In this research, simulation of viscoelasticity is related to a energy dissipation process in a conjugate gradient method. A new approach based on non-linear elasticity and finite element method is suggested, which is more robust and more efficient than the explicit method widely used in real-time surgery simulation. Experimental results show that the new method can be used in real-time simulation of soft tissue with large deformation.

A Scheduling Problem with Rejection of Goods Loading and Unloading

WANG Li;SUN Shi-jie

2007, 25(3):  283-283 . 

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We consider the following scheduling problem with rejection of goods loading and unloading: n ships reach the same harbor at the time 0, and all want to finish loading and unloading at the same time. If a ship cannot finish its work before or on its due date, the ship-owner will penalize the harbor, otherwise the ship-owner will pay prize to the harbor. At the same time, if the penalty is too heavy as a ship is delayed, the harbor may arrange this ship to be loaded or unloaded at other harbor after paying some penalty. The harbor needs to consider which ships are loaded or unloaded and what is the best sequence of loading and unloading so that the total cost is minimized. After giving some properties for this scheduling problem, we show that this problem is NP-hard, present a detailed analysis, and describe some pseudo-polynomial time solvable cases and polynomial time solvable cases.

Automated Reference Point Detection in Close Range Photogrammetry

ZHOU Ling;ZHANG Li-yan;ZHENG Jian-dong;ZHANG Wei-zhong

2007, 25(3):  288-288 . 

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Distributing reference points on the object to be measured is a reliable and common method for achieving optimum target location and accurate correspondence among multi-view images. In this paper circular uncoded targets and coded targets are used as reference points, and an algorithm of automatic reference point detection is proposed. Targets are extracted from the images according to their size, shape, intensity, etc. An improved method to identify every coded target is proposed. The gray scale centroid algorithm is applied to get subpixel locations of both uncoded and coded targets. Practical examples show that the algorithm can identify and locate reference points accurately. It is robust to the change of projection angles and noise.

Iterative Nonlinear Sliding Mode Control for Single Inverted Pendulum’s Position Tracking

BU Ren-xiang;LIU Zheng-jiang;LI Tie-shan

2007, 25(3):  295-295 . 

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A nonlinear sliding mode control method is presented for single inverted pendulum position tracking control. The nonlinear sliding mode is designed in the augmented states space using a decentralized and iterative procedure based on system output feedback. An increment feedback control law is then developed and proved to balance the pendulum-angle and drive the cart to track an arbitrary position without estimating the parameter uncertainties. Due to its simple structure and clear parametric functions, the controller is easy to be designed and adjusted for different control objectives. Numerical simulation results verify that the controller is robust to the systematic variations and both of the pendulum-angle and the cart velocity can be easily adjusted by parameters tuning in cart-position tracking.

Robust Adaptive Fuzzy Trajectory Linearization Control for Nonlinear Systems

ZHANG Chun-yu;JIANG Chang-sheng

2007, 25(3):  300-300 . 

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This paper presents a robust adaptive fuzzy trajectory linearization control (RAFTLC) based on the small gain theorem for a class of nonlinear multi-input multi-output(MIMO) uncertain systems. The unknown disturbances and uncertainties are approximated by a T-S fuzzy system, and the boundedness of all signals of the composite closed-loop system is guaranteed by Lyapunov method and the small gain theorem. This algorithm has only one adaptive parameter adjusting on line and is convenient to realize in engineering. Finally, a flight control system of an ASV is designed based on the proposed method. Simulation results demonstrate the effectiveness and robustness of the control scheme.

Mechanical Model of Super-thin Elastic Rod and Boundary Conditions

XUE Yun;ZHANG Yi

2007, 25(3):  306-306 . 

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A static model for super-thin elastic rod is described. The rod is treated as a process of a cross section moving along its axial line at a constant velocity, assuming a plane cross-section. The geometry of deformation of the rod section is discussed and differences between the Kirchhoff model and the Cosserat model are analyzed based on the definitions of strain vector at the center and curvature-twisting vector of the section. According to the equilibrium condition of a differential segment of the rod, a differential equilibrium equation of Cosserat model is derived. Closed form constitutive equations on principal vector and principal moment of forces acted on the section are given. The constraints subjected to the ends of rod are discussed and boundary conditions for the rod are given. It is concluded that equilibrium of the rod is a statically indeterminate problem.

Improved Multi-object Genetic Algorithm for Shock Response Spectrum Match

CAO Yuan;WANG Feng-quan;Tong Li-ping

2007, 25(3):  311-311 . 

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Improved multi-object genetic algorithm (IMGA) is used to study the matching technique of shock response spectrum (SRS). The improvements include using priority objective-active mechanism, building control group, selecting individual by the priority and distributing, unitizing parameters, and searching in chaos. Considering the practical need, a wavelet synthesis method is used to compute and optimized result is obtained. Simulation shows that IMGA is highly applicable and practical in the matching technique of SRS.

Computational Fluid Dynamics Simulation of Flow Distribution in a Gas Cooler with Micro-channel Parallel Flow

LU Ping;CHEN Jiang-ping;CHEN Zhi-jiu

2007, 25(3):  317-317 . 

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Using computational fluid dynamics (CFD) simulation, flow distribution in a gas cooler with micro-channel parallel flow is studied. It is found that the penetration depth between inlet header and tube, the length of tube, and the penetration depth between outlet header and tube have influence on the flow maldistribution among tubes, which is significant to the design of microchannel parallel flow gas cooler.

A Transmission Power Level Exchange Mechanism for Wireless Ad Hoc Networks

ZHU Yun;XU You-yun;CAI Yue-ming;QIU Song;CHENG Jie

2007, 25(3):  323-323 . 

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To reduce the packet collisions among nodes using different transmission power, a transmission power level exchange(TPLE) mechanism is proposed for wireless ad hoc networks to find an appropriate common transmit power level across the network. Simulation results show that this mechanism can improve network throughput and result in lower energy consumption in static network.

Delay Analysis of IR-UWB-based Distance Measuring in Multipath Channel

JIANG Ting-ting;ZHENG Guo-xin;ZHENG Rui-jie

2007, 25(3):  327-327 . 

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Time of arrival (TOA) estimation used with UWB transmission is currently considered as the most popular technique for accurate wireless distance measurement system. Because of the severe indoor multipath components, this estimation may be inaccurate. In this paper, characteristics of delay based on IR-UWB in line-of-sight (LOS) channel are investigated. The results show that the pulse period and SNR of the channels have a considerable influence on precision, which provides useful references to the distance measurement based on IR-UWB.