Table of Content

31 March 2004, Volume 22 Issue 1

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Articles

A Study on Adaptive Maximal Doppler Frequency Estimation for WCDMA Systems

SHENG Bin, YOU Xiao-hu

2004, 22(1):  1-5. 

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In this paper, a scheme that adaptively estimates one of the most important channel parameters——maximum Doppler frequency f_D is proposed for WCDMA systems. The scheme uses phase variations of received pilot signals, strongly related with f_D in a fading environment. The simulation results show that the proposed scheme is very simple, showing good performance over wide Doppler frequency range supported by 3G standard.

A Novel Blind Modulation Classification Algorithm in Adaptive Modulation

FANG Xin, YOU Xiao-hu, GAO Xi-qi

2004, 22(1):  6-9. 

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In this paper, a novel blind modulation classification algorithm is proposed in adaptive modulation on a packet-by-packet basis. This algorithm makes use of the distribution probability of the surrounding region of each point in the constellation vector. Analysis and simulation results show that it can achieve optimal performance in adaptive modulation and its complexity is very low and is suitable for real time processing.

Serial Concatenation of Space-Time Block Codes with Turbo Coded Modulation Systems

AHMED J. Jameel, PAN Zhi-wen, GAO Xi-qi, YOU Xiao-hu

2004, 22(1):  10-15. 

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In this paper, the concatenation of Turbo codes with space time block codes (STBCs) to improve the reliability of wireless communication over fading channels is considered. We combined rate 1/2 Turbo code as outer code and a simple two-antenna space-time block code as inner code for transmitting diversity and one receiver antenna. The iterative decoding scheme is based on MAP algorithm. The decoding complexity is mainly determined by the trellis complexity of the outer code. Simulation results show that exploiting transmit-diversity by using space-time block codes provides remarkable performance at the expense of almost no extra processing.

Steganalysis Based on the Statistics Method for LSB Insertion

ZHANG Xin-peng, WANG Shuo-zhong, ZHANG Kai-wen

2004, 22(1):  16-19. 

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This paper proposes a novel steganalysis technique based on the statistics method for LSB insertion, in which the change of statistical characteristic caused by information hiding is used to judge the presence of secret message. Numerical results show the performance of this developed method with different thresholds and, especially, both kinds of judgment error probability can be effectively controlled with the increase of embedded information.

A New Detection Algorithm of VBLAST

LAN Yang, CHEN ming, WANG Hai-feng, CHENG Shi-xin

2004, 22(1):  20-24. 

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In this paper, a new detection algorithm for VBLAST——GPIC(group parallel interference cancellation)——is proposed. The detection algorithm of VBLAST, called OSIC (ordered successive interference cancellation), uses linear combination nulling and successive symbol cancellation based on inversing and ordering. The computation complexity is high. GPIC proposed in this paper uses GIS (group interference suppression) to divide a system into several small systems to simplify the receiver and uses PIC to improve performance. The simulation results show that the scheme has a good performance.

A Novel Beam Propagation Method for the Analysis of Multimode Fiber Grating

WANG Yun-ming, DAI Jing-cao, ZHANG Ming-de, SUN Xiao-han

2004, 22(1):  25-29. 

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In this paper, a novel quasi-three-dimensional finite-difference time-domain beam propagation method(Q-FDTD-BPM) is proposed. In the cylindrical coordinate, the azimuthal component of the vector field solution is separated and three-dimensional equation is decomposed into several two-dimensional equations, which simplify the 3D discrete equations. And the method presented is developed using an alternating-direction implicit method and generalized Douglas scheme,which achieves higher accuracy than the regular FD scheme. Next the transform scheme is used to obtain the 3D resolutions of the equation. Based on this method, the simulated results for the spectrum of MMFG is obtained with a good approximation to the results in the experiment.

The Multi-packet Probe Technique for Measuring the Network Link Bandwidth

ZHAO Jin, CHEN Min

2004, 22(1):  30-34. 

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Measuring the link bandwidth is an open issue. Many scholars in the world are committing themselves to this work. Unfortunately, it is difficult to measure the link bandwidth accurately and fast. Up to now, we are still not able to get a method to measure the link bandwidth quite accurately and fast. In this paper, we first analyze the performance and the disadvantages of the existing one packet probe technique. To remedy its default, we put forward a new measurement technique called multi-packet probe technique. Finally we make a simulation to validate the new measurement technique. We find that, compared with the one packet probe technique, the multi-packet probe technique has higher accuracy, higher measuring speed and lower resource cost.

The Design and Development of Bluetooth LAN Gateway

XU Ping-ping, SHEN Lian-feng, QIAN Xiao-yong, BI Guang-guo

2004, 22(1):  35-40. 

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Based on the Bluetooth specification and LAN access profile, this paper presents the design and implementation of two versions of Bluetooth LAN access point (LAP). Firstly, the paper illustrates the LAN access profile in Bluetooth specifications in brief. Then, the design and development of LAP based on PC are discussed. Afterward, the implementation of embedded LAP is presented together with its key techniques,for example double module, VOS, multi-course, virtual serial port technique etc. The experimentation results show that LAPs developed satisfy the Bluetooth technology standard and the connection is very good with other Bluetooth equipment manufactured by other companies. The LAP both based on PC and embeded has had our intellectual asset and patent(IP) and is applied many fields so the industrialization foreground is very bright.

A Novel Channel Parameter Estimation Method for OFDM Systems

HAN Bing, GAO Xi-qi, YOU Xiao-hu

2004, 22(1):  41-45. 

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Based on the sparse-leakage channel, a novel channel parameter estimation method is proposed. This method exploits the correlation of the paths of the discrete-time correlated multipath channel to estimate the delay and amplitude of the original channel. Since the number of paths of the original channel is much smaller than that of the discrete-time correlated multipath channel, proposed channel parameter estimation method can suppress the AWGN and improve the accuracy of the channel estimation.

The Application of Electromagnetic Similarity in the Calculation of RCS of the Basic Scatterer

HU Yan, SHI Zhen-dong, TANG Pu, LIU Hong-wei

2004, 22(1):  46-49. 

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With the general expression for an arbitrarily simple-shaped scatterer's scattering characteristics as a starting point, the RCS varieties during the respective change of each parameter are analyzed. By these we can get the RCS of the prototype scatterer not only after the scaling of the RCS values in model measurement by means of the similarities, but also when the ideal scaling relation are not satisfied because of the limitation of experimental conditions. The latter result has established an academic basis for the extrapolation of the scattering frequency characteristic curves, and provided a new approach to the frequency range expansion of the RCS scaling measurement equipments.

Application of Adaptive Antenna Array Techniques Used for the OFDM System

YAN Yong-qing, JIANG Zhu-cheng, ZHAO Chun-ming, YOU Xiao-hu

2004, 22(1):  50-54. 

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Orthogonal frequency division multiplexing (OFDM), which has been widely used in the wire and wireless communication systems, is a promising technique in future wireless communications for its good performance in combating multipath fading. Based on the analysis of the basic OFDM system, an adaptive antenna array with Kalman algorithm of updating weights of antenna arrays in the frequency domain is presented in the paper. Theoretical analysis and computer simulation results show that the adaptive antenna array with the proposed algorithm has good performance in suppressing co-channel interference and can improve the receiving performance of the system.

Support Vector Machine Technique Applied to Computerized Prediction of Intermediate Phases of Some Phase Diagrams of Molten Salt Systems

LIU Xu, LU Wen-cong, LIU Liang, CHEN Nian-yi, YE Chen-zhou, YANG Jie

2004, 22(1):  55-59. 

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The newly developed support vector machine technique is suitable for data processing based on a finite number of training samples, with a special technique to restrict overfitting. In the present case the support vector classification technique is used for the computerized prediction of the formation of intermediate compounds in some molten salt systems. The prediction of the intermediate compound formation of KNO₃-KBr, KNO₃-KI and Cs,Li,Er|Cl systems has been made and the results confirmed by experiments. Besides, the leaving-one method has been used to compare the rate of correctness of the prediction of the formation of the intermediate compounds in AX-BX, AX₂-BX₂ systems,with that of the formation of A₃B₂C₁₉ and A₂BCl₅ type compounds in some rare earth-chloride containing systems by SVM, Fisher and KNN methods. The results indicate that the rate of correctness of prediction by SVM method is usually higher than the other two methods.

Workspace Analysis of NC Machine Tool Composed with Serial-Parallel Mechanism

ZHAN Yong, ZHOU Yun-fei, SHI Han-min, FANG Li-jin, XU Zhi-gang, ZHAO Ming-yang

2004, 22(1):  60-65. 

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As a novel and promising machining equipment, parallel NC machine tool has received great attention in recent years. Considering the usual disadvantages to parallel machine tools, such as small efficient workspace, complex manipulability and low applied rigidity, the serial-parallel mechanism is adopted in this project. Because workspace is an important design index of a machine tool, the 4-4 serial-parallel machine tool is studied in this paper. The geometry constraint conditions, which limit t... More

The Auxiliary System Method of Controlling Chaotic and Hyperchaotic Systems

CHEN Mao-yin, HAN Zheng-zhi, SHANG Yun

2004, 22(1):  66-70. 

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This paper proposes an auxiliary system method for controlling chaotic and hyperchaotic systems. We can thus design auxiliary systems for arbitrary chaotic and hyperchaotic systems. An iteration control law is designed to stabilize unstable periodic orbits in the chaotic attractor. Numerical simulation of the Lorenz system and a hyperchaotic system verifies the effectiveness of this method.

Stochastic Output Feedback Control of Networked Control Systems

ZHU Qi-xin, HU Shou-song

2004, 22(1):  71-75. 

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The optimal estimator of system state for networked control systems without full state information is presented. The design of stochastic optimal controllers of networked control systems with output feedback is also presented. The paper proves that optimal controllers can stabilize the exponentially mean square of networked control systems. Lastly, the simulation based on the networked controlled batch reactor is studied. The simulation results show that the proposed methods are correct and effective.

Adaptive Sliding Mode Control for a Class of Nonlinear System Based on Neural Networks

CHEN Mou, JIANG Chang-sheng

2004, 22(1):  76-80. 

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This paper is devoted to discussing a new control method which combine the approximation method of neural network with sliding mode control for a class of nonlinear systems. The controller is made up of an equivalent controller and an adaptive sliding mode controller. The sliding mode controller is a robust controller and it is used to diminish the track error of the control system. The neural networks are used to approximate the nonlinear functions and the approximation errors of the neural networks are introduced to the adaptive law in order to improve the quality of this system. Finally, an example is given to demonstrate the availability of this method.

A RBF Designing Method Based on Immune Clustering and Genetic Algorithm

GONG Xin-bao, ZHOU Xi-lang

2004, 22(1):  81-84. 

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Based on artificial immunology and genetic algorithm, a hybrid algorithm to design the RBF network is proposed. An artificial immune mechanism for data clustering is used to adaptively specify the amount and initial positions of the RBF centers according to input data set; then RBF network is then trained with genetic algorithm that makes the training process tend to global optima. The application of the algorithm in multiuser detection problems demonstrates that the RBF network trained with the algorithm is concise in structure and has good anti-MAI performance.

A Novel FDTD Simulation of Conductive Plane Covered with Parabolic Profile Inhomogeneous Plasma

LIU Shao-bin, MO Jin-jun, YUN Nai-chang

2004, 22(1):  85-90. 

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In this paper a novel FDTD formulation for dispersive media called piecewise linear JE recursive convolution (PLJERC) finite-different time-domain (FDTD) method is used to study the stealth technology of inhomogeneous plasma. The high accuracy and efficiency of this method is confirmed by computing the reflection and transmission coefficients of electromagnetic wave through a collisional plasma slab in one dimension. The stealth effect of radar targets covered with parabolic profile inhomogeneous plasma is studied both in time-domain and frequency-domain.

On the Conditions Necessary and Sufficient for Establishing Quasistationary Temperature Distribution

HU Han-ping

2004, 22(1):  91-93. 

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The general conditions necessary and sufficient for establishing quasistationary temperature distribution in any case are presented and proved.

The Influence of Heat Resistance, Heat Leak and Internal Irreversibility on the Performance of a Four-Heat-Reservoir Absorption Refrigeration Cycle

ZHENG Tong, CHEN Lin-gen, SUN Feng-rui

2004, 22(1):  94-101. 

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On the basis of an endoreversible absorption refrigeration cycle, an irreversible four-heat-reservoir cycle model is built by taking account of the heat resistance, heat leak and irreversibilities due to the internal dissipation of the working fluid. The fundamental optimal relation between the coefficient of performance and the cooling load, the maximum coefficient of performance with its corresponding cooling load, and the maximum cooling load with its corresponding coefficient of performance of the cycle coupled to constant-temperature heat reservoirs are derived by using finite-time thermodynamics. The optimal distribution of the heat-transfer surface areas is also obtained. Moreover, the effects of the cycle parameters on the coefficient of performance and the cooling load of the cycle are studied through detailed numerical examples. The results can provide the theoretical bases for the optimal design and operation of a real absorption refrigerator operating at four temperature levels.

Dynamic Property and Anti-forecast Requirements of Hopping Sequences

ZHANG Shen-ru

2004, 22(1):  102-106. 

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Hopping sequences used in anti-jamming hopping communication ought to have a longer period, therefore the partial and dynamic properties of balance and Hamming correlation are more essential in practical hopping sequences application. For the sake of anti-forecast two new design desires of sensitivity of hopping sequences to time of date(TOD) and address code are put forward. To check carefully partial and dynamic properties of balance and Hamming correlation is necessary for traditionary hopping sequences. The traditionary method of simple exclusive OR output sequences by address code is not available for requirement of anti-forecast. It is necessary to mix address code in transform process of input TOD as block cryptogram. To base on aforementioned understand we propose that partial and dynamic property of balance and Hamming correlation and two requirements of anti-forecast ought to be important targets of technical performance in hopping sequences application.

The Model of Generalized Weighted Functional Mean Combining Forecasting and Its Application

WAN Yu-cheng, SHENG Zhao-han

2004, 22(1):  107-112. 

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For the actual cases of various forecasting problems, combining forecasting models may take different forms. But their forecasting efficiencies may be different for the different models. In this paper, we present a new kind of combining forecasting model based on the generalized weighted functional mean and the parameter estimation methods of its weighting coefficients. In final, we use this model to forecast air materiel consumption. And its efficiency is demonstrated by an example.

Study of Strong Consistency of Nearest Neighbor Estimation in Nonparametric Regression Function

SUN Dao-de

2004, 22(1):  113-117. 

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In this paper, the strong consistency of nearest neighbor estimation m_n(x)) of regression function m(x) with stationary and H-mixed sample sequence {(x_n,y_n),n ≥ 1} is studied and applied it in nonparametric test.

The Pre-processing of De-noising in fMRI Data Based on Wavelet Analysis

ZENG Wei-ming, LUO Li-min, LIAN GXiao-yun, WANG Shi-jie, GUO Sheng-wen

2004, 22(1):  118-123. 

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Image denoising in fMRI based on a wavelet analysis is discussed. A more suitable Hard-Soft function, which is derived from the Hard function and the Soft function (both developed by Donoho and Johnstone) is presented. According to the analysis of the results, the Hard-Soft function is superior to the Soft function in preserving image details and superior to the Hard function in removing image noise. Thus, better balance can be achieved between the image details preserved and the noise removed and the two extreme states held by the Hard function and the Soft function can be overcome.

Robust Fault Detection Based on Neural Network Adaptive Observers

ZHOU Chuan, HU Wei-li, CHEN Qing-wei

2004, 22(1):  124-126. 

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A fault detection method based on dynamic recurrent neural networks for uncertain nonlinear system is presented in this paper. A residual information is obtained by using adaptive neural networks observers, so the system faults can be detected rapidly. The uniformly ultimately bounded stability of closed-loop error system is guaranteed by Lyapunov stability theory. Finally simulation results of a fighter's control surface failure reveal the effectiveness of this method.