Table of Content

31 July 2006, Volume 24 Issue 4

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Articles

A Power Control MAC Protocol Based on 802.11 and Computer Simulation

GU Yan, SHEN Lian-feng

2006, 24(4):  331-335. 

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A power controll MAC (medium access control) protocol based on IEEE 802.11 is presented.Transmission power and the permitted receiving power of messages are comprised in the control packets.Through exchange of control information between a pair of communication nodes transmission power of the data packet is determined, and the neighbor nodes' transmission power is restricted, which can effectively reduce interference between hidden terminals and exposed terminals.The protocol also allows neighbor nodes to transmit messages during data receiving.In simulation the protocol is compared with the IEEE 802.11 MAC protocol.The results indicate that, in mobile ad hoc networks, the powercontrol protocol can improve the network throughput performance, while significantly reduce power consumption of mobile nodes and improve energy utilization efficiency of mobile terminals.Moreover, it can reduce energy consumption of the system by more than 93%.

Performance Improvement of Turbo Code in Non-Gaussian Noise

JIANG Yu-zhong, HU Xiu-lin, ZHANG Shu-xia

2006, 24(4):  336-340. 

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This paper investigates the loss of Turbo decoding performance in non-Gaussian impulsive noise with computer simulation, and proposes a new decoding algorithm for Turbo code by using Middleton's Class A impulsive noise model based on the statistical nature of the amplitude.The algorithm improves performance by modified extrinsic and channel information of traditional MAP to suit additive white Class A noise.Simulation results show that the proposed algorithm has better performance than traditional MAP algorithm in Class A noise.

LSCM_SUB Algorithm Applied to Semi-blind Multi-user Detection

LIU Sheng-mei, ZHAO Chun-ming, LI Can-wei

2006, 24(4):  341-344. 

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The semi-blind LSCM-SUB (SB-LSCM-SUB) algorithm applied in the semi-blind MUD (Multi-user detection) of CDMA is studied.Compared to the blind CM algorithm and the decorrelation algorithm, the proposed semi-blind LSCM-SUB algorithm exhibits better SIR and BER performance, and is more robust when the system is heavily loaded.

Joint Source-Channel Decoding Based on Iterative Source Model Parameter Update

YIN Wei-wei, WU Le-nan

2006, 24(4):  345-348. 

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A joint source-channel decoding scheme implemented by simultaneously decoding and updating parameters based on HMM is proposed.First, the source parameter used in the joint source-channel decoding is updated by the a priori knowledge obtained through the training sequence and the received noisy information sequence.The joint source-channel decoding is then employed.These two steps are implemented iteratively.The iterative updating algorithm improves precision of the probability structure of the received sequence and performance of the joint source channel decoding.The degree of parameter improvement of the source model can be obtained from the perspective of the information theory.

An IEEE 802.16 Multi-hop Mutual SA Management Mechanism Associated with Hypo-optimal Routing

WANG Xing-jian, HU Ai-qun, HUANG Yu-hua

2006, 24(4):  349-353. 

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IEEE 802.16-2004 wireless-MAN standard supports two types of network architecture, i.e., PMP and mesh. In this paper, we first introduce a more robust and efficient PMP mutual authentication SA (security association) mechanism, which removes the certificate transmission after the first authentication to reduce system cost.A multi-hop mutual authentication SA mechanism associated with hypo-optimal routing strategy in mesh is then proposed.These two mechanisms guarantee a degree of protection comparable to those defined in the 802.16 protocol, while provide forward security and immunity against attacks on intermediate nodes.The routing strategy attached to mesh SA mechanism makes it possible to transmit management information before establishment of the on-demand data routing to shorten the service flow creation delay.

Bandwidth Schedule in IEEE 802.16 Systems Based on Mesh Mode

GUAN Yan-feng, HU Ai-qun, CHEN Li-quan

2006, 24(4):  354-358. 

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This paper studies strategy of bandwidth schedule in the IEEE 802.16 based on the mesh mode and proposes a stratified scheduling model.According to the principle of schedule load minimization, we conclude that an optimum division in the schedule exists in chain topology and prove that any mesh network, which can be decomposed into an aggregate of chain topology, also has the optimum stratification.A solution to the optimum stratification is provided, and the effects of BS's cover area on the stratification analyzed.Numerical results show that the bandwidth schedule with stratification remarkably decreases the loads and hops needed by scheduling.

Mental Task Classification Based on Approximate Entropy of EEG

JIANG Zhao-hui, GAO Cui-yun, FENG Huan-qing

2006, 24(4):  359-362. 

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Mental activity is closely related to the complexity of electroencephalogram (EEG) in different areas of brain. In order to classify five different kinds of mental tasks, approximate entropy (ApEn), an index of complexity, is calculated from six channels EEG and serve as input feature vector to a neural network.Testing results show that the average classification accuracy is 73% obtained from the average of 5 trials, indicating feasibility of classifying different mental tasks based on complexity of multi-channel EEG.The introduced technique is useful in the research of human machine interface.

Active Contour Model for Edge Detection Based on Simplified Mumford-Shah Functional

XU Dan-hua, BAO Xu-dong, SHU Hua-zhong, LUO Li-min

2006, 24(4):  363-367. 

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An improved active contour model for edge detection based on Chan and Vese active contour model is proposed.The basic idea is to evolve a curve under constraints from a given image, which is defined as a union of two homogeneous regions representing the object and background respectively.The edge can be detected by seeking a global minimum of an energy function based on the Mumford-Shah functional.The constant term in this model is modified by combining the image gradient information in piecewise constant optimal approximations.This different constant term can be obtained by adjusting the weighting factor that acts on the image gradient term in constant function, and different edge map based on different intensity of image can be obtained.This method is capable of handling changes in the topology of the evolving contour, and can avoid the problem arise in the C-V model that cannot detect the edges whose values are far from the mean intensity value of image.Effectiveness of this method is demonstrated in numerical experiments.

Lithium-Ion Battery Lifespan Prediction Model

XU Shen, LI Jie, WANG Chao

2006, 24(4):  368-371. 

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Battery modeling is important in power consumption optimization for which battery specifications are a critical consideration.The analytical battery model proposed by Daler Rakhmatov is quite successful in terms of prediction accuracy and popularity.Based on this model, this paper proposes a simple battery model for accurately predicting lifespan of lithium-ion batteries.Applicability of the proposed model is analyzed.The model covers cases of both constant lo ad and variable load.Accuracy of the battery lifespan predicted by the proposed model is validated by simulation results.

Noise in Deep Submicron CMOS Gilbert Mixers

TANG Shou-long, WU Jian-hui, LUO Lan

2006, 24(4):  372-376. 

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The noise behavior of deep sub micron CMOS Gilbert mixers is investigated.An analytical noise figure model of the mixers is derived.Prediction based on the analysis is compared with simulation results based on 0.25 μm CMOS technology.The maximum absolute prediction error is less than 1.5 dB and the relative prediction error is less than 12.5%.The technique is useful in providing a guide to the design of CMOS mixer.

Automatic Generation and Evaluation of Test Case Based on Z Specifications

ZHU Bing, MIAO Huai-kou, WANG Na

2006, 24(4):  377-381. 

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Software testing is important in software quality assurance, in which test case is crucial.In this paper, a test frame is produced through category-partition, a linear programming model is constructed using the test frame, and linear programming model is solved to give an example of the test frame.A solution is also given to judge whether a test frame is feasible or not.Finally an example is presented based on invoice computation to illustrate the generation process of the test case from Z specifications, with a detailed discussion on the method used.

Data Mining Algorithm Based on Negative Association Rules

ZHU Yu-quan, YANG He-biao

2006, 24(4):  382-386. 

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Typical association rules consider only items enumerated in transactions, referred to as positive association rules.Negative association rules also consider the same items, but in addition, also consider negated items, i.e., those absent in transactions.Negative association rules are useful in market-basket analysis to identify products that conflict with each other or products that complement each other.They are also convenient for associative classifiers, classifiers that build their classification model based on association rules.Indeed, data mining using such rules necessitates examination of an exponentially large search space.Despite their usefulness, very few algorithms for mine this information have been proposed to date.In this paper, a fast and efficient algorithm MNAR is presented to discover negative association rules.Meanwhile, a method for calculating the support of itemsets is proposed.Experiments show that the MNAR algorithm is effective and feasible.

A Two-Tier Overlay Network Model for Distributed Data Stream Processing

WANG Jin-dong, ZHANG Lei, DING Qiu-lin, HUANG Tian-qiang

2006, 24(4):  387-390. 

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Requirements for processing data stream in distributed networks and characteristics of the overlay network are discussed.Based on the Chord model, a two-tier overlay network model is proposed to support distributed data stream processing.An algorithm is presented, which is used to establish the two-tier overlay network.Applications of the model show the validity of the model.

A Locality-Aware Protocol in Multicast Tree for Stream Media

PANG Li-ping, YUAN Quan, DENG Da-fu, GUO Xiang-zhou, ZHANG Chao, JIN Hai

2006, 24(4):  391-395. 

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This paper proposes a multicast protocol at the application level for efficiently broadcasting live media streams to a large number of users.The main idea of this protocol is to self-organize the end hosts into a locality-aware overlay multicast tree based on their network position coordinates.The result is that the overlay multicast tree has a good match to the underlying physical network such that the link stress and the end-to-end delay can be effectively reduced.In the mean time, real-life network constraints can be handled.

An Efficient Clustering Algorithm of Large Scale and High Dimensional Data Set

ZHOU Xiao-yun, SUN Zhi-hui, ZHANG Bai-li

2006, 24(4):  396-400. 

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Clustering large data set of high dimensionality has always been a serious challenge for clustering algorithms. Traditional clustering algorithms often fail to detect meaningful clusters because of the high dimensionality and inherently sparse feature space of most real-world data sets.Nevertheless, the data sets often contain clusters hidden in various subspaces of the original feature space.In addition, high-dimensional data often contain a significant amount of noise which causes additional effectiveness problems.To overcome these problems, a new algorithm based on CLIQUE, named OpCluster, is proposed.A set of experiments on a synthetic dataset demonstrate the effectiveness and efficiency of the new approach.

Enterprise Application Supporting Environment Based on SOA and the Implementation

LI Ya-bai, HAO Wen-yu, WANG Ning-sheng, CAI Zong-yan

2006, 24(4):  401-405. 

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Service-oriented architecture (SOA) has been enjoying popularity in recent years as an emerging norm of application integration.However, key issues of development, organization and management of services in enterprises are not well addressed.This paper proposes a multitier framework of SOA-based enterprise application, analyzes problems of service development and deployment within enterprise, introduces services execution processes and service cooperation, and discusses correlative implement technologies.

Two-Layer Two-Level Decision-Making for Aircraft Fault Location

GUO Ya-zhong, ZUO Hong-fu, WANG Hua-wei

2006, 24(4):  406-409. 

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Traditional fault location methods for civil aircrafts rely only on the usage and experiments, which are time consuming and require manual operations.According to the reliability indexes and the framework of the civil aircraft, a two-layer two-level decision-making method is proposed.It takes the design attributes as a main consideration and uses a fitting method for data standardization and weight determination to locate faults.Practical examples show effectiveness of the method, which is an improvement to the traditional methods.

Accuracy Optimization Design of Flexible Three-Coordinate Measuring Arm

WANG Ping-ping, FEI Ye-tai, LIN Shen-wang

2006, 24(4):  410-414. 

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A flexible three-coordinate measuring arm (CMA) with 6-DOF is studied.The measurement equation and the equation of position errors of its stylus are derived.Optimization analysis of the CMA parameters is carried out in order to minimize position errors of the stylus.The results are useful to the optimization design of CMA mechanical structures.

Operation Angle Variation of Drills During Cutting

ZHANG Ping-kuan, WANG Gui-cheng, WANG Hui-lin

2006, 24(4):  415-418. 

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Operation angles of a drill are influenced by variation of parameters of the axial vibration drilling.As the tool is cutting intermittently, the start and end points are first determined.The working rank angle and back angle of the tool during cutting are calculated.Using the metal cutting theory, cutting parameters are analyzed, and parameters of vibrating drill given.This opens a new way for studying the mechanism of vibrating drill and selecting parameters.

Quantum Heat Engine Cycle Working with Spin System

HE Ji-zhou, WU Xin, OUYANG Wei-ping

2006, 24(4):  419-423. 

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A new model of a quantum heat engine cycle is established in which the working substance consists of many non-interacting spin-1/2 systems.Performance characteristics of the cycle and time evolution of the spin angular momentum are investigated, based on the quantum master equation and a semi-group approach.The general expressions of efficiency and power output are derived.Further, at high temperatures the optimal relations of efficiency and power output are studied in detail.Optimal performance of heat engine cycles is analyzed from a microscopic model.

Annual Runoff Prediction Based on GA and Simulated Annealing

QIAO Xi-xian, JIANG Xiao-hui, HUANG Qiang, HE Hong-mou, CHEN Li

2006, 24(4):  424-428. 

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To effectively utilize information of the section interdependence in the time series of annual runoff, a threshold auto-regressive (TAR) model is proposed to predict annual runoff.A simple and general scheme is presented to establish a TAR model.With an improved genetic algorithm, both the threshold values and auto-regressive coefficients can be optimized, and the problem of TAR modeling resolved, giving a powerful tool for wide application of the TAR model.A case study shows that the scheme is practical and efficient, and the TAR model can successfully reduce model errors and, by controlling the threshold values, ensure good stability and accuracy of the model forecast.As a general method, the scheme has theoretical value and wide range of applications in nonlinear time series prediction.

Surface States of Sol-gel Derived BaTiO₃ Thin Films

CHEN Hai-tao, HU Jie-bo, LOU Hui, CAI Hong-tao, DING Ling-hong, ZHANG Wei-feng

2006, 24(4):  429-432. 

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Perovskite BaTiO₃ thin films were grown on SiO₂/Si (111) substrates by a sol-gel process and rapid thermal annealing (RTA).Surface states and the topmost surface atoms of the BaTiO₃ thin films were analyzed by X-ray photoelectron spectroscopy (XPS) and angle-resolved X-ray photo electron spectroscopy (ARXPS).The results show that the as-fired BaTiO₃ thin films have an enriched-BaO nonstoichiometric surface layer that can be removed by A_r⁺ ion sputtering, and the atomic ratio of Ba to Ti decreases with a decreasing depth from the film surface.

Research Notes

Effect of Antenna Correlation on ST-FSK System Performance

JIANG Hui-juan, TAN Xiao, SHEN Yue-hong

2006, 24(4):  433-436. 

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Space-time frequency keying (ST-FSK) can be merged naturally into frequency-hopping communication systems.Based on a previous study, this paper presents an incoherent ML decision metric in the receiver with knowledge of transmitter antenna correlation, and discusses the relationship between correlation factor, SNR, and reliability index for binary ST-FSK and quaternary ST-FSK in the presence of antenna correlation.The theoretical analysis employs random variable decomposition.Simulation results show that the presence of transmitting antenna correlation, which is equivalent to destruction of unitary characteristics, imposes extra power cost on the performance of ST-FSK systems.The corresponding power cost increases nonlinearly with correlation factor, but makes little difference for binary ST-FSK and quaternary ST-FSK.

Optimization Model for Radar Deployment

GAO Shang

2006, 24(4):  437-440. 

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Joint probability of target detection in a system of multiple radar sets is studied.Several models of optimum deployment in circle, line, sector and multi-line, respectively, have been built.Optimum models of circle, line and sector deployment can be obtained using methods of exhaustive enumeration, golden section, or coordinate alternation. For multi-line arrays, if the number of radars is not too large, the problem can be solved using a combination of exhaustive enumeration and coordinate alternation.When the number of radars is large, a combination of genetic algorithm and the coordinate alternation method should be used.