Table of Content

31 March 2008, Volume 26 Issue 2

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Articles

Classification of Modulation Techniques Using Constellation Shape and Similarity Measure

2008, 26(2):  111-111 . 

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In this paper, we study the problem of modulation classification in the presence of phase error and improve modulation classification algorithm which uses constellation shape as classification signature. First, dynamic clustering algorithm is utilized to recover unknown constellation based on similarity between samples and kernels. Then recovery constellation is matched with constellations of different modulated signals and classified by a proposed max-likelihood rule, which is simple and equivalent to minimum distance classification rule. This rule avoids a training phase which is necessary for spatial statistics of recovery constellation vertices in previous algorithms. Considering the effect of additive noise on phase estimation, simulations show that the correct rate is above 90 percent when SNR is 10db and 15db respectively under the condition of known and unknown number of modulation states.

Design and Implementation of Embedded Radio Network Management Model Based on SNMP Protocol

XIAO Zhe;CHEN Bing

2008, 26(2):  117-117 . 

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he widespread application of embedded wireless network equipment requires better management of the network. This paper takes subway wireless communication system as an application scenario. An embedded radio network management model is constructed based on the Simple Network Management Protocol (SNMP). The private wireless-related MIB of embedded radio is defined on ASN.1, and function modules of agent are designed. After cross compiling and transplanting the agent, we have implemented the function of network management. Test results show that the agent has a good compatibility, and extra load of system to the network is tolerable.

Ultra-wideband Wireless Communication Based on Chirp-BOK-BPSK Modulation

FENG Jin-Zhen;ZHENG Guo-Xin

2008, 26(2):  123-123 . 

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Based on strong autocorrelation of up-chirp and down-chirp, and extra-low cross-correlation between them, and using Chirp-BOK, we propose the Chirp-BOK-BPSK modulation that can be used in UWB wireless communication system. In this scheme, input data are modulated onto both phases of the Chirp and slope of instantaneous frequency. The BER performance of Chirp-BOK-BPSK UWB scheme is analyzed in an AWGN environment. In the indoor setting, however, the system shows seviere ISI. Simulation has been done to obtain BER performance of the Chirp-BOK-BPSK and compared with the Chirp-BOK UWB. The results show that BER of Chirp-BOK-BPSK is less than 10-4 at a 12dB SNR.

Orthogonality and Power Spectra of EBPSK Modulated Waves

ZHANG Shi-kai;WU Le-nan

2008, 26(2):  127-127 . 

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Waveform orthogonality has a direct influence on signal bandwidth and demodulation. The paper obtains orthogonal EBPSK signals and power spectrum by deriving EBPSK correlative expression and power spectrum expression. The best power spectrum condition, duty cycle of one and phase shift of π/2, are given. This is helpful in parameter selection of EBPSK waveform control. As the symbol correlativity is increased, the power is more concentrated but with poorer demodulation performance. On the other side, with symbol correlativity decreased, performance of demodulation is improved, but power becomes more distributed. The best orthogonal power spectrum can reduce line spectrum components, make power concentrated and spectra compressed. Thus bandwidth efficiency is improved and, at the same time, performance of demodulation is also improved for symbol orthogonality. Therefore a good tradeoff between symbol correlativity and demodulation performance is obtained.


XOR Approximation of Modulo Addition for Cryptanalysis

ZHOU Yue;LI Rui-lin;LI Chao

2008, 26(2):  132-132 . 

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Modern cipher components ususlly combine mixed operations of different groups. In cryptanalysis,one alwalys uses the XOR operation to linearly approximate modular addition,which requires calculation of the distribution of noise.In this paper, we propose a reduced linear representation of such distribution based on the formal power series on free monoid which can be easily used to calculate the pobability diatribution.We also extend the result to the addition modulo p^n.This provides a solid basis for linear cryptanalysis.

Relaxational Smooth Processing for Detection of Weak Concentration Gas

ZHU Ming;WANG Shu;ZHU Zhen-yu;LIU Li-jing

2008, 26(2):  137-137 . 

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By analyzing the energy transfer models in molecular collision processes and the acoustic relaxation attenuation in gas, we find the reason of ruggedness in the dependence of molecular multi-relaxation attenuation coefficient on the mixture concentrations when the gas constituents have concentrations less than 0.01%. We use a typical smooth window to process acoustic relaxation attenuation data, and develop an algorithm to detect weak gas concentration of three-component gas mixtures. The measuring accuracy of this method achieves 0.001%. Three designed matrices with different weighted averages can all reduce errors resulting from weak gas concentration. The simulation results of consistent error-reduction using all the matrices show that the relaxation smooth processing algorithm is reasonable.


Influence of Alternated Magnetic Field on Ice Crystal Formation Process in Aqueous Solution

CHEN Zhao-zhang;WANG Heng-hai;HUANG Yong-hong;XU Xiao-bin

2008, 26(2):  145-145 . 

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Nondestructive cryogenic preservation has been an important research topic in cryobiology. Organisms are mostly composed of aqueous solution. Common methods involve the use of an ultra-rapid cooling rate or a very high concentration of cryoprotectants. Unfortunately, adding cryoprotectants introduces impurities for biomaterials themselves and ultrarapid freezing is very difficult to obtain the same cooling rate for the surface and interior of big samples. The influence of ice crystal formation process in KMnO4 solution by alternated magnetic field was studied under the condition of low cooling rate. Alternated magnetic field was produced based on series resonance. This study shows that 50 kHz alternated magnetic field can suppress ice crystal growth in the solution, and salty ice formed. The result of low freezing rate cryopreservation easy achieved is of great significance, and useful in practical applications.


Prediction of Protein Secondary Structure with an Improved Measure of Information Discrepancy

LI Zhe－qian;LIU Shu-peng;YAN Zhuang-zhi;XIN Yan-fei

2008, 26(2):  150-150 . 

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The secondary structure prediction is important in protein structure prediction since protein secondary structure is the basis of the tertiary structure. A method of information discrepancy-FDOD (Function of Degree of Disagreement) was used to predict protein secondary structure in this work. Data were selected from the CB396 database and prediction accuracy was 72.1%. Besides, multiple alignment of PSI-BLAST was used to combine with FDOD, with the prediction accuracy increased to 75.6%. Furthermore, in order to reduce computation complexity, hydrophobic values were introduced to improve the algorithm and the impact factors of hydrophobic values. Long-range interaction is discussed in the prediction of protein secondary structure.


RF Front-End Topology Design of Wideband Receivers

Zhou Jian-zheng;Wang Zhi-gong;Li Li;Wang Ke-ping

2008, 26(2):  155-155 . 

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A high-side injection, fixed intermediate frequency (IF), double-quadrature-downconversion and low-IF structure is proposed for wideband receivers. Four image rejection ratios (IRR), and relationship between IRRs and the amplitude errors ΔA or phase errors Δθ of two kinds of double quadrature receiver structures (single-double and double-double quadrature structures) are derived. Comparison of these two structures shows that single-double quadrature conversion is more suitable for wideband receivers. To improve IRRs of the system, two modules, RF filter and polyphase filter before the second downconersion, are added to the single-double quadrature structure. The quantitative IRRs performance of the total RF-end and a design example, DRM receiver RF-end, are given. Simulation results show that this RF-end structure has good IRR performance (when -10°≤Δθ≤10°，-0.1≤ΔA≤0.1, IRRs≥61.16dB). This is an ideal structure for wideband radio receivers, combining the inherent characteristics of a low-IF structure such as suitability for high integrality, ability of supporting multi-standard communication, and immunity to parasitical low frequency noise.


Uplink Multi-user Alamouti MIMO Detection with Antenna Selection

ZHANG Xiao-ge;XU Cheng-qi

2008, 26(2):  162-162 . 

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To improve the diversity benefit of the uplink multi-user MIMO detection, the ordered successive user cancellation (OSUC) detection and the antenna selection technique are applied. Two antenna selection criteria for OSUC detection called max-min user SINR and max-first user SINR are proposed. The selection criterion for non-OSUC detection called max-min user SINR is also proposed. The Sherman-Morrison formula is used to reduce computation complexity. Simulation results show that OSUC detection obtains only a little more diversity benefit, and antenna selection obtains almost all the diversity benefit of the full complexity system when no less than 2(P-1)+1 antennas are selected.


Circularly Polarized Microstrip Antenna Easily Integrated with Active IC

SUN Jiang-Tao;YANG Xue-Xia;SHENG Jie

2008, 26(2):  167-167 . 

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This paper presents a novel unequal cross-slot coupled circularly polarized microstrip antenna excited by coplanar waveguide (CPW), which is convenient to be integrated with active circuits. Influence of the antenna’s size on the characteristics is analyzed using an electromagnetic simulator. A prototype is designed and fabricated. The measured results are in good agreement with simulation. The measured bandwidth of VSWR below 2 reaches 600MHz and axial ratio is 1.7dB in the main direction, with 3dB bandwidth of 140MHz at the central frequency of 10.28GH. Good circular polarization performance has been shown in experiments.


Design of Slot Antenna for RFID Tag Using ANN


ZHOU Yong-ming;LAI Xiao-zheng;LAI Sheng-li

2008, 26(2):  171-171 . 

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To study the optimized design of slot antenna for RFID tags, attention is paid to optimize design of the slot antenna using artificial neural networks (ANN). Shortcomings of traditional design method with one dimension geometrical parameter for tag antenna have been avoided. The design is consistent with that of IE3D simulation which is based on the method of moment (MOM). A slot antenna for tag is fabricated, and the reading distance is measured with the compatible reader, showing that the slot antenna can meet the requirement of UHF tag.



Detection of Anomalous User Behavior Based on Shell Commands and Hidden Markov Models


TIAN Xing－uang;DUAN Mi-yi;SUN Chun-lai;LI Wen-fa

2008, 26(2):  175-175 . 

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Anomaly detection is an active research topic in network intrusion detection. This paper presents a novel method for detecting anomalous user behavior based on shell commands and hidden Markov models (HMM). The method constructs a specific HMM to represent the normal behavior profile of a network user, and associates classes of user behavior patterns with states of the HMM. The HMM parameters are calculated with a sequence matching algorithm which is much simpler than the classical Baum-Welch algorithm. This reduces computational complexity to a great extent. At the detection stage, a decision rule based on probabilities of short state sequences is adopted, and more than one threshold are used to classify the user behavior. Performance of the method is tested in computer simulation, showing high detection accuracy and efficiency.


OLAP Security Strategy Based on Dimension and Hierarchy of Data Cube



YANG Ke-hua

2008, 26(2):  182-182 . 

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By analyzing the hierarchical structure of information in a data cube, security strategy of an online analysis process (OLAP) based on dimension and hierarchy of data cube is proposed. By combining the visit rules with the information of dimension and hierarchy of data cube, the security strategy is easily implemented, and can support OLAP operations more efficiently. Theoretical analyses and experiments show that this security strategy has powerful description ability, simple management and high execution efficiency.


Distributed Reservation Architecture of Simultaneous Multithreading Processor



YANG Hong-bin;WU Yue;LIU Quan-sheng

2008, 26(2):  188-188 . 

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To improve the high-efficiency parallel processing performance of data flow instruction of a simultaneous multithreading processor, a 7-part distributed reservation architecture is presented. The simultaneous multithreading processor uses committing mechanism for each thread with single reorder buffer and register with smart speed and low complexity of hardware. The parallel degree of data flow instruction is improved for two threads. The function of reservation, committing mechanism and register is validated and simulated. These units are synthesized.


Growing Sparse Neural Networks


FENG Chao;LI Ning;LI Shao-yuan

2008, 26(2):  194-194 . 

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When using sparse neural networks in practice, it is hard to choose a proper connection rate. In this work, based on new discoveries in the brain science, two new learning algorithms are developed which change the network’s connection structure at the time of learning, thus an accurate connection rate is not needed. Sparse neural networks reduce coupling among inputs so that fewer connections are needed to meet the fitting requirement. Simulation results show that the new algorithms are effective.


Measurement and Control of Bimodal Ultrasonic Motor Based on Wavelet Actuation



XU Congyu;YU Xiaofen

2008, 26(2):  199-199 . 

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At present, bimodal ultrasonic motor (USM) applied to large displacement actuation and nanometer positioning control uses combination control of the actuation’s modes, namely AC actuation mode, pulse actuation mode and the DC actuation mode. This paper proposes a novel single wavelet actuation pattern of bimodal USM, which can realize step control with the stepping distance adjusted. A wavelet actuation wave is composed of 8 sinusoidal voltage waves of 39.6 kHz, whose maximum triggering frequency is up to 5 kHz. In a positioning control application, the grating with 20?m pitch was selected as the displacement measurement sensor. The fast subdivision formula of mutual compensation functions developed by the author was used as the grating nanometer measurement tool. With the control algorithm of measurement and actuation sequence, the maximum stepping distance of bimodal USM was 2?m and the maximum actuation speed of the stage reached 10mm/s. The experimental results indicate that when the wavelet actuation parameters are properly chosen, nanometer actuation resolution and nanometer positioning accuracy can be reached.



Reliable Robust Control for a Class of Uncertain Switched Systems


DONG Xue-ping;WANG Zhi-quan

2008, 26(2):  204-204 . 

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Based on the method of Lyapunov function, design of reliable robust controllers is given such that the corresponding closed-loop system is globally asymptotically stable for all admissible uncertainties and actuator failures for a class of uncertain switched systems. Next, with the linear matrix inequalities (LMI) approach, design of robust reliable controllers can be converted into a feasible problem of certain LMI system. The solution of controllers can be efficiently obtained with the Matlab LMI toolbox. A numerical example shows validity of the proposed design method.


Tracking Control for a Class of Uncertain Nonlinear Systems with Time-Varying Delay Using Multi-model Switching



HU Cheng-zhong;QIAN Cheng-shan;YANG Zhao-hua;WANG Yan-qing

2008, 26(2):  209-209 . 

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This paper studies the design of a tracking control for a class of uncertain nonlinear systems with time-varying delay using multi-model switching in the presence of uncertainty. First, T-S models with time-delay are employed to model the uncertain nonlinear system with time-delay. When uncertainty is gain bounded, a sufficient condition, which satisfies the closed-loop stability and the performance of H∞ tracking, is presented for the existence of the controller. Finally, a region controller, chosen according to the selected variables by the multiple-model switching control, is switched to the whole controller, and other controllers do not operate. Thus the control of the entire nonlinear system is established. Effectiveness of the proposed method is demonstrated with simulation results.


Inverse Kinematics for Robot Based on BP Network and Orthogonal Design Experimentation


XUE Yan-min;LIU Hong-zhao

2008, 26(2):  216-216 . 

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This paper deals with the inverse kinematics problem of the PUMA560 robot. Based on six similar BP neural networks, the inverse kinematics solution of the manipulator is obtained. The training parameters are obtained by optimized organization using orthogonal design experimentation (ODE). Simulation results indicate that this method has the advantage of fast learning rate, high precision of identification and better real-time capability.