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25 March 2005, Volume 26 Issue 3

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Academic paper

Optimal sensor node distribution algorithm based on tree in sensor network

Ying-you WEN,Yue-qiu JIANG,Lin-liang ZHAO,Guang-xing WANG

2005, 26(3):  1-6.  doi:1000-436X(2005)03-0001-06

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In sensor networks, a reasonable distribution of sensor nodes will do much good to the improvement of sensor ability, information aggregation ability and network survival. In sensor network constructed by randomly distribution, better sensor coverage could be achieved by topology adjustment utilizing mobility of sensor node. To solve this problem, we defined extending-tree of sink node in sensor network by utilizing Voronoi diagrams and delaunay network. Also a new optimal algorithm of sensor node distribution based on Genetic algorithm was designed. Simulation output shows that this algorithm can achieve an optimizing node distribution in object area, by which sensor ability of the whole sensor network can be improved at a low cost relatively.

Automatic video object extraction algorithm based on wavelet and watershed

Gao-bo YANG,Zhao-yang ZHANG,Sheng-fa3 YU

2005, 26(3):  7-13.  doi:1000-436X(2005)03-0007-07

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A spatio-temporal video object segmentation algorithm was proposed. Temporal segmentation was based on change detection. Its key was the selection of appropriate threshold, which was obtained by histogram analysis. For spatial segmentation, discrete wavelet transform was first conducted, and then watershed was performed on the low-resolution image. A region-based classification scheme was utilized to fuse the temporal and spatial segmentation. The proposed approach can get rid of the influence by noise and effectively overcome the “over-segmentation”. Experimental results demonstrate that it can achieve more desirable results than COST211 AM.

Fast adaptive beamforming receiver based on multiuser channel estimates from a CDMA base station

Long-guang ZHANG,Yuan-ping ZHOU,Ning XIE,Wen-kun WEN

2005, 26(3):  14-20.  doi:1000-436X(2005)03-0014-07

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In a CDMA system, channel estimates of all received user signals were available at base stations. Using these information, we proposed a novel fast adaptive beamforming receiver that combined a LMS algorithm and a novel pattern synthesis technique. Theoretical analysis and simulation results show that although the new algorithm adds a little more complexity, it provides a much faster convergence rate as well as a superior performance.

Hybrid synchronization of chaos and its application in secure communication

Tie-gang GAO,Zeng-qiang CHEN,Zhu-zhi1 YUAN

2005, 26(3):  21-24.  doi:000-436X(2005)03-0021-04

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A simple methodology for a class of chaos synchronization was studied. By constructing an observer of chaotic system, the method that colld be used for both chaos synchronization and secure communication was given, and furthermore its stability was analyzed. Numerical examples illustrated the accuracy and high performance of the proposed method for chaos synchronization and secure communication.

Research of CMVDR receiver for STBC MIMO CDMA system

Jian-feng SHEN,Zhao-wei LIU,Zong-xin WANG

2005, 26(3):  25-30.  doi:1000-436X(2005)03-0025-06

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A new constrained minimum variance distortionless response (CMVDR) receiver based on maximum likelihood (ML) estimation of multiuser for STBC MIMO CDMA system with high performance, which was used to suppress multiple access interference (MAI) and intersymbol interference (ISI) well, was proposed. The STBC MIMO CDMA system model and channel model were given. Using the channel parameters estimated by ML method, two CMVDR receivers, separately weighted and unitarily weighted, were proposed. These receivers could also be applied to SIMO CDMA system. The simulation results of STBC MIMO CDMA system and SIMO CDMA system using the proposed CMVDR receiver are presented. The comparison of performance between the separately weighted CMVDR receiver and unitarily weighted CMVDR receiver, and the comparison of systems using the proposed CMVDR receiver with adaptive CMMSE (constrained minimum mean square error) systems are given.

Model and analysis of handoff delay for mobile IP in the case of cell overlap

Qing-lin ZHAO,Li FENG

2005, 26(3):  31-38.  doi:1000-436X(2005)03-0031-08

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The handoff delay and out-of-sequence packets in the handoff process of Mobile IP were numerically analyzed for the first time, and the general expressions of their probabilities were obtained respectively. And according to the results, the radius of overlap region was optimized. The illustrations show that the proposed method models precisely the handoff characteristic. The probabilities are very helpful to evaluate handoff performance.

PDAVQ: an adaptive virtual queue algorithm based on the proportional and differential control

Yan YANG,Lian-sheng TAN,Nai-xue XIONG

2005, 26(3):  39-44.  doi:1000-436X(2005)03-0039-06

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A novel adaptive virtual queue (AVQ) algorithm is proposed that was based on the Proportional and Differential Control mechanism, which is termed PDAVQ. This algorithm avoids congestion of network link and achieves the goal of utilizing the link capacity efficiently and relieving the network congestion. Furthermore, the system stability using control theory was studied, and the stability area of control gains is described for implementation of the proposed algorithm. Finally, we compare PDAVQ with the known AVQ algorithm by simulations. The simulation results demonstrate the performance excellence of the proposed algorithm in terms of the higher utilization, the lower link delay, the lower loss rate and fast system response.

Algorithm for the reliability indexes by calculation of mscps

HENGKang-kang S,HENYuan-long S

2005, 26(3):  45-50.  doi:1000-436X(2005)03-0045-06

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To deduce the difficulty of calculation of frequency, duration, and availability indexes in a capacity-limited complex network, this paper presented a new approach to obtain these indexes using a conditional probability formulation and topological enumeration of all the required states, considering the capacity limitation of the links in the given network. This approach can be used to obtain the expressions for frequency duration, and availability indexes and can also be used to obtain accurate estimates of the indexes for large network.

Exploration of code division multiple access (OCDMA) spectral encoder/decoder based on fiber grating

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2005, 26(3):  51-57.  doi:1000-436X(2005)03-0051-07

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According to the spectral encoding/decoding theory, This paper analyses and proves the spectral encoding/decoding theory of OCDMA based on fiber grating. A mapping code is introduced and designed phase shift is inserted to the corresponding subgrating of SCFBG according to the mapping code. At the same time the paper give a equivalent model of encoder/ decoder. A good correlation is offered by numerical simulation for encoder/decoder, proving the feasibility of this encoding/decoding method. In the end the paper analyses the factors which affect the performance of this system.

Algorithm on high resolution DOA estimation under condition of unknown number of signal sources

Chong-ying QI,Yong-shun ZHANG,Xi-hong CHEN,Ying HAN

2005, 26(3):  58-63.  doi:1000-436X(2005)03-0058-06

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An algorithm on the estimation of the direction of arrival with unknown number of signal sources is presented in this paper. Under condition of unknown number of signal sources, the new algorithm is combined LP or Pisarenko method with ASPECT to estimate the DOA with high resolution. The spurious peaks in DOAs with LP or Pisarenko method can be removed and the number of signal sources can be determined at the same time. The computational complexity is reduced and the DOA resolution is also improved in this algorithm. Computer simulation results approve the correctness and validity of this new algorithm.

MPLS adaptive traffic engineering algorithm based on hops and delay

Bing-feng CUI,Zhen YANG,Wei DING

2005, 26(3):  64-67.  doi:1000-436X(2005)03-0064-04

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The advent of multiprotocol label switching(MPLS) allowed packets to be sent along explicit paths,an explicit routing mechanism,which put a true basis for traffic engineering. A MPLS adaptive traffic engineering algorithm based on hops and delay was presented. The algorithm distributed traffic among LSP according to hops and delay of each LSP. Therefore,congestion resulted from destination-based forwarding in traditional IP routers could be avoided and optimize network resource utilization. Simulation indicates that the algorithm work well in MPLS networks.

SBlue: stabilized Blue

Chun-ming WU,Ming JIANG

2005, 26(3):  68-74.  doi:1000-436X(2005)03-0068-07

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In order to address the problems of TCP end-to-end congestion control, the IETF advocates to deploy active queue management mechanisms in the network. Blue is a popular AQM algorithm. It uses packet loss and link idle events to manage congestion. Compared with RED, Blue has many advantages. But because of lacking incipient congestion detecting mechanism, it suffers from queue size oscillations. Moreover many active TCP connections in the router or the variety of the number of active TCP connections will lead to queue overflow and underflow. A new AQM algorithm named “SBlue”(stabilized Blue) is proposed. Simulation results indicate that SBlue can effectively stabilize the queue occupation at a level independent of the number of active TCP connections and mitigate the queue overflow and underflow.

Digital pulse interval modulation for atmospheric optical wireless communications

Zong-min HU,Jun-xiong TANG

2005, 26(3):  75-79.  doi:1000-436X(2005)03-0075-05

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The error probability performance of digital pulse interval modulation (DPIM) for atmospheric optical wireless communications (OWC) was analyzed and an optical wireless communications system model with atmospheric optical radiance scintillation channel and an avalanche photodiode detector (APD) receiver was established. the transmission power and bandwidth requirement of DPIM were discussed and shown that for a given number of bits per symbol, DPIM has high transmission efficiency and low bandwidth requirement. Both the theory and the simulation results show that compared with pulse position modulation (PPM), DPIM only has a marginally inferior error probability, but less complicated to implement. Hence,DPIM is superior in wireless optical communications system.

Technical Report

Study of mobile-agent based network management accounting system model

Zhi CHEN,Ru-chuan WANG,Jie LI

2005, 26(3):  80-85.  doi:1000-436X(2005)03-0080-06

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A model of network management accounting system based on mobile agents was proposed and particularly studied on its structure, accounting management process and security mechanism. The system makes use of mobility and intelligence of mobile agents and can have a persistent, efficient, flexible, real-time and accurate accounting management on network based on different accounting modes. Experiment shows that it can ease the burden of the managed network and has good adaptability to the changes of the managed network and the capability of real-time processing.

Secure monitoring framework based on multi-policies

Hong-zi WEN,Si-han QING,Wei-ping WEN,Xiao-dong LI

2005, 26(3):  86-91.  doi:1000-436X(2005)03-0086-06

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The current secure monitoring facility using generic logging data has the problems of the redundancy of logging data and the delay of auditing. This essay proposes a formal secure monitor framework for multi-policies (MP-SMF), which can solve the above problems and is easy to be configurated. Additionally, the application of Bell-LaPadula secure policy in MP-SMF is introduced.

Maximum running revenue based parlay gateway overload control

Yun-yong ZHANG,Zhi-jiang ZHANG,Guo-jie LI,Yun-jie LIU,Zhong-cheng LI

2005, 26(3):  92-98.  doi:1000-436X(2005)03-0092-07

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Node based overload control algorithm is not flexible and has long responding time. And some new requirements of Parlay gateway overload control are needed in next generation network(NGN). Maximum revenue based network-based overload control model of Parlay gateway is proposed. Furthermore, agent linear programming theory is imported into network-based overload control algorithm. And overload control architecture based on agent linear programming is given out. Simulation results show that it is quick to find out maximum revenue based overload control algorithm and is scalable in large softswitch network. Also, it can reduce the responding time, improve control sensitivity and divide subnets flexibly according to the different areas.

Study on queue scheme of gated polling multi-access communication system

Yan LI,Dong-feng ZHAO,Hong-wei DING,Fei GAO

2005, 26(3):  105.  doi:1000-436X(2005)03-0099-07

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The gated polling multi-access communication system was analyzed in discrete time. By improving the queue scheme, the analytical expression of average queue length on the polling point and average message delay were obtained. The imbedded Markov chain theory and the generating function method were used. The simulation shows the analytical is reasonable and the performance is enhanced compared with ordinary polling gated system; With an simple and approximate arithmetic, the analytical expression of average queue length during the polling cycle time is presented and is in accordance with the result of computer simulation.

Enhanced layered video multicast algorithm based on active agent——AELM

Zhao-ling ZHAO,Jiang-xing WU,Ming-duo LI,Yu-hua GUO

2005, 26(3):  106-110.  doi:1000-436X(2005)03-0106-05

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As a promising multi-rate video broadcasting algorithm to heterogeneous receivers, RLM uses periodically conducting a combination of “join-experiments” and “branch pruning” events to manage network congestion. However, there are some problem in RLM, such as requirements of the users to cooperate with each other, slow reactions, and much more usage of routing entries. Based on the mechanism of RLM, this paper improved it through introducing into active agent and correlatively dropping with priority method and developed an enhanced layered video multicast algorithm based on active agent-AELM. Simulations show that the new algorithm proposed in this paper has solved the problems existed in the RLM algorithm.

Overview

Survey on network-based QoS for IP videoconference

Lian DUAN,Hai-na TANG,Jun LI

2005, 26(3):  111-116.  doi:1000-436X(2005)03-0111-06

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The most popular QoS mechanisms for videoconference were surveyed in this paper, and described from data plane and control plane in detail. The advantages and application range of these mechanisms were discussed respectively, as well as the existing shortcomings and problems . Additionally, especially to the features of the videoconference, the proper QoS solutions based on these mechanisms to improve the performance of videoconference were presented. It is known that admission control plays a important role in Qos for videoconference. Therefore a strong emphasis on it was laid. Finally some problems which should be paid attention to when deploying QoS for videoconference, as well as limitations of current technologies and future research issues of QoS for videoconference were discussed..

Short essay

Study on optimum objective of topology control in multi-hop wireless networks

Lu-lin ZHANG,HANGNing Z,Ya-nan ZHAO,Wei-ling WU

2005, 26(3):  117-123.  doi:1000-436X(2005)03-0117-07

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The relationship between the topology structure and its performance in the multi-hop wireless networks was studied. The number result showed that the topology constructed by nodes and their most neighborhood nodes has the best throughput, and at the same time this topology can meet the requirements for low power consumption, low probability of intercept and high reliability. The conclusion was validated by our simulation results. Thus the objective of topology control is turn to the problem of selecting the most neighborhood nodes for the node from all the nodes around it and establishing logical connections with them.

Academic communication

Description and browsing of video story structure

Dong-hui WANG,Hui QIAN,Miao-liang ZHU

2005, 26(3):  124-129.  doi:1000-436X(2005)03-0124-06

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This paper presented a method for the description and browsing of video story structure. An innovatory algorithm of video segmentation was introduced to find the shot edge. And another refined match algorithm based on content comparability was proposed to implement the map of video structure from one dimension to two dimensions. By describing video story structure as a storyboard and sequence structure graph, video content can be browsed summarily.

Timing error recovery for LDPC-coded systems

UEYing-jian X,Xiao-fu WU,Hai-ge XIANG

2005, 26(3):  130-135.  doi:1000-436X(2005)03-0130-06

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Based on the statistical properties of LDPC decoding algorithm, the effect of the symbol synchronization error on the decoding performance was investigated in detail. A new timing error recovery algorithm was developed based on the algorithm in [3]. The new algorithm estimated the timing error with four times of over-sampling rate, and the estimated value of the signal with precise timing was given by interpolation of the over-sampled data. With the proposed algorithm, little performance degradation has been observed for LDPC coded system with severe symbol timing error when working at very low SNR.

Study of predicting network traffic using fuzzy neural networks

Zhao-xia WANG,Yu-gen SUN,Zeng-qiang CHEN,Zhu-zhi YUAN

2005, 26(3):  136-140.  doi:1000-436X(2005)03-0136-05

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A five-layer fuzzy neural network (FNN), which utilized both the linguistic, was addressed human-like reasoning of fuzzy systems and the powerful computing ability of neural networks (NN), for predicting the nonlinear self-similar network traffic. The FNN was trained by the Back-propagation algorithms, which was used to train the NN. The simulation demonstrates that the FNN could well predict this traffic. Compared with the sole NN, FNN was superior to NN. FNN not only could converge quickly, but also the error was lower. It supplies a feasible method for predicting the complex network traffic research.