Table of Content

31 January 2007, Volume 25 Issue 1

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Articles

Adaptive Subcarrier Allocation for Multi-user OSTBC-OFDM Systems

LI Li, ZHU Guang-xi

2007, 25(1):  1-5. 

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An adaptive subcarrier allocation algorithm for multiuser OSTBC-OFDM system is discussed in this paper. Aimed at minimizing the overall transmit power subjected to meet the target BER, an adaptive subcarrier general allocation algorithm with efficiency-priority is proposed.To achieve a desirable tradeoff between efficiency and fairness, all users are given a guaranteed transmission rate.An amendatory four-step algorithm with fairness constraint is described.Simulation results show that the proposed algorithms can improve BER performance of the OSTBC-OFDM system.

Statistics of Non-zero Mean Random Polarized Waves

LI Yong-zhen, WANG Xue-song, WANG Lian-dong, XIAO Shun-ping, WANG Guo-yu

2007, 25(1):  6-10. 

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Statistical characteristics of non-zero mean random polarized waves are studied based on the instantaneous polarization theory.Under a Gaussian hypothesis, probability density functions (PDFs) and joint PDFs of the amplitude, power and phase of random polarized waves are presented.The PDFs of instantaneous polarization projection vector (IPPV) of non-zero mean random polarized waves are then analyzed, which can entirely describe polarization characteristics of electromagnetic waves.Finally, relationship between the PDFs and the covariance ratio between two polarization channels are analyzed, assuming that the two polarization channels are independent.Conclusions drawn in this paper are useful to some applications such as dim signal detection and polarization measurement.

Articles

A Power Control Method Based on Post-Detection SINR Balancing in Cellular V-BLAST Systems

WEI Chuan-ming, QIU Ling, ZHU Jin-kang

2007, 25(1):  11-15. 

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Power control is an effective technique to restrain the co-channel interference (CCI) in a cellular system.In this paper, an optimal power control method based on post-detection SINR balancing for a cellular V-BLAST system is proposed.Its simplified solution with reduced complexity is provided.The proposed method may balance the postdetection SINR of each substream at mobile stations (MS) by adjusting power levels of every transmit antenna at base stations (BS) in the system.Simulation results show that the proposed method outperforms existing power control methods both in the system outage probability and BER performance.The simplified solution significantly reduces computing complexity with slight performance degradation.

Low-Complexity Iterative Multiuser Detection Algorithm for Asynchronous CDMA Systems

MEI Zhong-hui, YIN Wei-wei, WU Le-nan

2007, 25(1):  16-20. 

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This paper presents two low-complexity iterative multiuser algorithms:parallel soft cancellation probabilistic data association (P-SC-PDA) and successive soft cancellation probabilistic data association (S-SC-PDA) for asynchronous CDMA systems.The computational complexity of the proposed algorithms is just o(K³) where K is the number of active users.Simulation results show that performance of the S-SC-PDA algorithm is significantly better than P-SC-PDA.With information delivered by the decoder, if the user signals to be detected is arranged such that signals of users with high detection reliabilities are detected first, and those with low detection reliabilities are detected later, even better performance can be obtained with S-SC-PDA.

Improved Rate-Maximization-Based Adaptive Resource Allocation for Multiuser OFDM Systems

WANG Yan-jun, CHEN Qian-bin, KUANG Yu-jun

2007, 25(1):  21-25. 

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Optimal adaptive resource allocation algorithms are computationally complex and time consuming, which is unfavorable for real-time application.To overcome this shortcoming, a rate-maximization-based low complexity adaptive resource allocation is proposed for multiuser OFDM systems, which maximizes the overall data rate under the constraint of total transmit power and BER performance.Simulation results show that the algorithm has better performance in terms of fairness and computational complexity comparing with original algorithm.

Optimal Capacity Method of Blast Architecture for SUC Detection

PAN Wen, JIANG Zhan-jun, WANG Yan, YOU Xiao-hu

2007, 25(1):  26-29. 

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When a blast system employs the successive interference cancellation (SUC) method to detect signal, the diversity orders of transmitter antennas are not equal to each other, resulting in the different statistical characteristic among the channels of different transmitter antennas.In this case, the antenna average energy allocation (AAEA) method is not optimal in achieving the largest channel capacity.In this paper, based on analysis of channel ergodic capacity of a blast system, an antenna optimization energy allocation (AOEA) method is proposed.It is proved by capacity upperbound analysis that, by employing this method, channel ergodic capacity can be maximized.Simulation results show that channel capacity is improved at low SNR with the AAOA method.

Security Analysis of MANET Routing Protocol

JI Xiao-jun, TIAN Chang, ZHANG Yu-sen

2007, 25(1):  30-34. 

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Secure routing protocol design and analysis is the core of the security problems in mobile ad hoc network.This paper uses strand space and BAN logic to prove plausible route property of secure mobile ad hoc network routing protocol. Our analysis indicates that security of mobile ad hoc network routing protocol is essentially based on agent authentication and message integrity between trusted nodes in the network, therefore traditional formal methods can also be used to analyze secure mobile ad hoc network routing protocols.

Optimization of Spacer Distribution in a Field Emission Display Device

GU Wei, LEI Wei, ZHANG Xiao-bing

2007, 25(1):  35-39. 

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In a field emission display (FED) panel, spacers are used to support the anode and cathode substrate. Different distortions of the panel are generated with different spacer distributions.Because distortions of the panels change the distance between the anode and cathode substrates, the internal electric field and the uniformity of emission characteristics is influenced by the spacer distribution.This paper studies the panel distortions with polar spacers and thin wall spacers.It is shown that the equal-lateral triangle patterned spacers are optimal for spacer distribution.Compared with the traditional arrayed pattern, fluctuation of brightness uniformity is reduced by one third.

A Class of Preconditioners for MLFMA Based on CFIE

LI Wei-dong, HONG Wei, ZHOU Hou-xing

2007, 25(1):  40-45. 

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In this paper, preconditioners for multi-level fast multipole algorithm (MLFMA) are investigated.Based on its structure, the near-part of MLFMA matrix is split into a block-diagonal matrix, and incomplete lower matrix, and an incomplete upper block matrix.The block-diagonal matrices are LU decomposition.A series of preconditioners (DILU) are constructed.These preconditioners can save CPU time by greatly reducing the number of iterations.Some preconditioners require slightly increased memory size, while others even do not need any additional memory.Numerical examples compare efficiency of the preconditioners, and show validity of the accelerated algorithms.

Application of Ant Colony Algorithm in SRAM Hierarchical Partition

GU Ming, YANG Jun, ZHANG Qi-chen, GAO Gu-gang

2007, 25(1):  46-50. 

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On-chip SRAM is a basic and important macro block of SoC.SRAM hierarchical partition affects the power consumption, delay and area of SoC.In this paper a new kind of random optimization algorithm, ant colony algorithm, is proposed to solve the SRAM hierarchical partition problem.Experimental results show improved performance of the proposed method.

Application Layer Multicast-Like Search Engine Model Based on Mobile Agent

LIAO Xiao-fei, LI Jin-sheng, HONG Pei-lin, XUE Kai-ping

2007, 25(1):  51-56. 

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Search engine is the key in searching network resource.This paper proposes a search engine model based on the mobile agent technique and application layer multicast.Network simulations show that this model has better performance in terms of total search time and network load.It is suitable for designing and implementating search engine.

Bandwidth Measurement in Satellite Network

ZENG Bin, LI Zhi-tang, WANG Wei

2007, 25(1):  57-62. 

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Existing algorithms for bandwidth measurement are unable to achieve balance between real time performance and reliability for satellite communication networks.To solve the problem, an intervening model is proposed to analyze the relationship between packet pair dispersion and cross traffic.Using this model, packet pair spacing with higher accuracy can be achieved.An algorithm of fast probe packet group is also developed.Results of simulation under the GEO/LEO satellite network model show that the algorithm can measure the bandwidth with high speed and low network resource cost.

Load Shedding for Continuous Query Based on Sub-path Analysis

WANG Jin-dong, ZHOU Liang, ZHANG Lei, DING Qiu-lin

2007, 25(1):  63-68. 

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Load shedding caused by burst of input data stream is studied in this paper.The deficiency of current load shedding methods is discussed and characteristics of data stream and continuous query networks analyzed.Definition and restrictions of the problem are given.A load-shedding algorithm based on sub-path analysis is proposed to solve the problem.Analysis and experiments show efficiency of the algorithm.

A New Density Control Algorithm for Surveillance Sensor Networks

SHEN Yang, QI Wang-dong, DAI Hao, YIN Xiang-lan, CHEN Hua

2007, 25(1):  69-73. 

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Density control is a key technique in surveillance sensor networks.In this paper, a new density control algorithm called Enhanced Sponsored Sector Coverage (ESSC) is presented based on the Sponsored Sector Coverage (SSC).The proposed method takes account of some drawbacks in the SSC algorithm and modifies it to minimize the active node number.Analysis and experiments show that ESSC can reduce the number of active nodes by up to 15%~25% in comparison with SSC while maintaining the network surveillance performance.

Ontology Clustering Based on Semantics

ZHANG Lei, XIE Qiang, LI Ling-zhi, DING Qiu-lin

2007, 25(1):  74-80. 

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Ontology clustering is an effective assistant means to integrate ontologies.However, studies on ontology clustering are rare.An ontology similarity computing method based on semantics is proposed.The method considers not only the concept, but also the attribute set and related concept set.Basic similarity threshold of concept is used to control probability to compute similarity of attribute sets.Semantic radius is used to control the scope of related concepts. Similarity matrix of ontology clustering is calculated using an ontology similarity method.An agglomerative hierarchical clustering algorithm is used for ontology clustering.Experiments show that semantic based ontology clustering can give satisfied results, and its performance is better than ontology clustering using the oMAP similarity method.The method has been applied in an aeronautical institute and played a special role in ontology integration.

Gray Dynamic Model of Verification Cycle in Measuring Instruments and Its Application

SU Hai-tao, YANG Shi-yuan, DONG Hua, SHEN Mao-hu

2007, 25(1):  81-84. 

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We establish two gray dynamic models GDM(1, 1) of measuring instrument's verification cycle based on time and frequency sequences by using the statistical feature of examined data and a weighting method.For a specific case, vernier caliper for example, the model has high precision in fitting and prediction.The lifecycles can vary under different working conditions.Prediction results of the frequency sequence model are better than that of the time sequence model. Based on information integration, multi-sensor control and management control, a control and information subsystem for verification cycle and lifecycle is set up for a case of gray dynamic model and auto-manufacturing.The models can be used to produce process to help enterprise reduce error, flaw and cost.

Time Delay Kinetics in Gene Regulatory Networks

ZHANG Jia-jun, CAI Chuan-zheng, WANG Yi-fei

2007, 25(1):  85-90. 

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Time delay kinetics are ubiquitous in gene regulation, because of the vast separation of time scales between the fast reactions like DNA-binding and dimerizations, and slow reactions like translation, transcription and degradation.We develop a stochastic model of the delay gene regulatory network, and study both deterministic monments evolution equations and modified Gillespie algorithm simulation numerically.For example, single gene delay autoregulatory network and double gene delay regulatory network are studied.We find that time delays tend to create oscillations in gene regulatory network, in agreement with experiment data.

Equivalent Dielectric Constant Theory for Optical Bistability in Nonlinear Thin Coated Composites

GU Li-ping, GAO Lei

2007, 25(1):  91-95. 

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With the dielectric constant method, the dielectric response for three-phase composite media, in which coated inclusions are randomly embedded in a dielectric host, can be regarded as that of two-phase composites.As a result, we are able to obtain the dependence of the local field on the applied field based on the spectral representation theory.Then, we adopt the Maxwell-Garnett approximation to investigate optical bistability (OB) of three-component composites in which non-spherical coated inclusions are randomly embedded in a dielectric host in the dilute limit.Numerical results show that the OB behavior is strongly dependent on the depolarization factor (L) of the particles.The field-dependent effective dielectric constant of the composites is also studied.

Weighted Summation of Wavelet Coefficients Model for Annual Runoff Prediction

LI Ya-jiao, SHEN Bing, LI Jia-ke

2007, 25(1):  96-99. 

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The method that analyzes the period characteristics of annual runoff with continuous wavelet transformation and wavelet variance has been widely used.However it only gives qualitative prediction results, but not quantitative results. Based on the primary qualitative method, we propose an annual runoff prediction model using weighted sum of wavelet coefficients of major periods to predict the periodic components.The method effectively takes advantage of the multiresolution characteristic of wavelet analysis, and can reduce prediction errors caused by trend components.The annual runoff data of Qianhe basin are used to build and check the model.The proposed method can provide better results useful in predicting annual runoff time series.

Gray Analysis for Correlation between Yarn Strength and of Cotton Fiber Quality

LI Xiao-feng, WANG Jian-jun, MA Jie, ZHOU Yi

2007, 25(1):  100-102. 

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We have found that the relationship between the cotton fiber quality and the yarn strength can be modeled as a gray system.This paper describes a detailed analysis of the system.The study shows that the yarn strength is strongly affected by the length of the cotton fiber.The index is also influenced by maturity of the fiber, but is insensitive to the diameter and strength of the fiber.The findings are consistent with practical observations, indicating that the gray system analysis is an effective method for parametrical analysis of yarn strength.

Design of Adaptive Interleaving in Wireless OFDM Systems

XU Xiao-dong, JING Ya, YOU Xiao-hu, CHEN Ming

2007, 25(1):  103-107. 

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In modern communication systems, only combined with interleaving techniques can error correction codes effectively improve the system performance.In wireless OFDM systems, adaptive interleaving techniques based on instantaneous subcarrier channel state information can break burst errors more effectively into random errors, achieving a better system performance than traditional block interleaving.This paper proposes an improved adaptive interleaving scheme that not only achieves a better system performance, especially the frame error rate (FER), but also reduces the algorithm complexity.

Adaptive Determination of Micro-satellite Attitude Using Pseudo Gyro, Magnetometer and Earth Sensor

YU Feng, LIU Jian-ye, XIONG Zhi, DUAN Fang

2007, 25(1):  108-110. 

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Attitude determination is a key that affects the performance of a micro satellite platform.An adaptive extended Kalman filtering algorithm is presented in this paper for attitude determination consisting of a pseudo gyro, a magnetometer and an earth sensor.Attitude determination performance of a satellite on two orbits with different inclination is studied by simulation.The results indicate that roll and pitch accuracy is about 0.05ånd heading accuracy is better than 0.4°.The accuracy is improved as inclination decreases.When the earth sensor fails, roll and pitch accuracy of the satellite on the orbit with large inclination is better than 0.5°, and heading accuracy is about 1°.The adaptive Kalman filter can evidently enhance attitude determination performance.