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• • 1999, Vol. 22 No. 3 Published date:10 July 1999 Last issue Next issue

  • System Analysis of SA/CDMA Employing Smart Antenna
  • Li Xiaoqiang, Hu Jiandong
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 1-6.
  • Abstract ( 246 )     HTML     　　
  • Analyze the system capacity improvement by employingsmart antenna at base and mobile station.A full direction searching algorithm is provided.It also constructs a two element arrays used at mobile station.A method to update weight value based downlink pilot signal is promoted also.Numericalresult of Monte-Carlo simulation proves the reverse link capacity increasementand system frequency reusing efficiency improvement from smart antenna method.
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  • ATM Cell Scheduling Based on NN and Input Buffers with Different Priorities
  • Li Lianyuan, Liu Zemin
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 7-11.
  • Abstract ( 219 )     HTML     　　
  • A novel neural network cell controller with a new structure of input buffers in ATM switch are proposed. For each input port of switch, there are two buffers. Cells sensitive to time delay are put in high priority buffers and cells insensitive to time delay in low priority buffers. Accordingto certain optimization rules, head cells of input buffers are selected to be switched by a hopfield neural network controller. The simulation results show that the proposal can ensure cells to meet their QoS and the cell lost rate and cell delay are lower than those of randomly selecting cells in a open window. Also,the effects of parameters in neural network are discussed.
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  • Generalized Synchronization in Two Coupled Logistic Maps
  • Zhu Hongbo, Xiao Jinghua,Li Xiangming
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 12-15.
  • Abstract ( 219 )     HTML     　　
  • Interest in synchronization of chaos has increased because of its possible relevance to secure communication. Recently, papers discussing a more general idea of synchronization have appeared in the literature. We investigate chaossynchronization of nonidentical coupled maps. It is shown that two coupled Logistic maps at different parameter values may not only satisfy stable linear relation but also nonlinear relation with proper coupled fashion. Thestrict analytical proof about it is proposed. This is a new method that don't rely on numerical method completely. We also give the range of the coefficient ofcoupling in generalized synchronization and the functions of the stable linear relation and the stable nonlinear relation.
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  • Research In Q3 Interface Adaptation Technology
  • Qin Yi, Yang Zhengqiu, Liu Tiegang, Meng Luoming
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 16-20.
  • Abstract ( 228 )     HTML     　　
  • Q3 interface adaptation technology is presented to implement the TMN-based network management on traditional telecommunication devices that can not be directly managed by TMN operation system for they have no Q3interface. Then the theory of Q3 interface adaptation technology is illustratedin details. On the basis of the theory and the analysis of the result of trials, an optimized architecture is designed for the implementation of adaptation technology. In the end, an ODP viewpoint is also applied to analyze the internal interface in the architecture to provide specific telecommunication devices with TMN-based network management interface.
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  • The Harmonic and Intermodulation Distortion in the Transmission of Optical Subcarrier Multiplexing
  • Yang Xuemin, Chen Shuqiang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 21-25.
  • Abstract ( 205 )     HTML     　　
  • When subcarrier multiplexing (SCM) technology is applied for optical transmission, intermodulation products originate from two different nonlinear effects. There are intrinsic nonlinearities cause by the mixing ofphotons and electrons in the laser cavity. The other is the nonliearity of thelaser P-I curve. As the frequency of subcarrier become more and more high ,theeffect of harmonic and intermodulation distortion on distortion originated fromthe intrinsic nonlinearities of semiconductor laser become more and more important. Using rate equation of laser, Analysis and calculates the harmonic and intermodulation distortion,and analysis the approach of decreasing the distortion.
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  • IN CS-2 Call Party Handling and Its Implementation
  • Cheng Dan, Wang Hongman, Yang Fangchun
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 26-30.
  • Abstract ( 173 )     HTML     　　
  • The Connection View State (CVS) approach is used to describe and implement CPH which is proposed in IN Capability Set 2 (CS-2 ) by ITU-T. A method is presented for designing and implementing general IN services. Some issues about the CPHrelated standards are discussed, and the CPH applications on current networks are illustrated. Related experiment and its results are described.
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  • Application of Wavelet Denoising in Speech Recognition
  • Hu Huiying, Wu Shanpei
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 31-34.
  • Abstract ( 244 )     HTML     　　
  • The performance of most current speech recognition systems degrades markedly innoisy environment. So, how to improve the robustness of system is the focus ofthe current speech recognition. The wavelet to the pre-process of the noisy speech recognition is applied, distinguishes the voiced from unvoiced speech in thewavelet domain, and deals with the voiced and unvoiced speech with threshold differently, and then performs the recognition after the inverse-transformation of denoising wavelet coefficients. The result demonstrates that the wavelet process is promising to the performance of noisy speech recognition.
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  • A Recursive Real-Time CAC Algorithm and Performance Analysis
  • Wu Muqing, Xu Chunxiu, Ding Wei
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 35-39.
  • Abstract ( 251 )     HTML     　　
  • The CAC algorithm presented aims at reducing the complexity of the computation, raising its call processing capability in real time, andmeanwhile raising the utilization of the network resources. By dividing equallythe link capacity into a flight of stairs, through a recursive computation, wecan estimate the quality of service on the link and make the decision to acceptor reject the calls. The performance of the algorithm is analysed according to the circumstances of our applications. The algorithm uses only two traffic parameters easily declared and policed, the peak bit rate and the average bit rate. The CAC scheme is simple and can be realized in real time.
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  • A Formula to Calculate Network Mix Reliability
  • Su Sixi, Wu Xiaofei
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 40-43.
  • Abstract ( 248 )     HTML     　　
  • Network reliability describes network connectivity ability when network is in outage. A general formula to calculate network reliability is found. The formula can be used in all failure conditions. The complexityof the formula roughly equals complexity of formulas which are used only in node failures or only in edge failures. The formula successfully extends usage areafrom node failures or edge failures only to all failure conditions.
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  • Correlation Functions of GMW-Geometric Sequences(2)
  • Sun Wei, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 44-49.
  • Abstract ( 228 )     HTML     　　
  • Based on GMW sequences, a family of GMW-geometric sequences are constructed, and their correlation functions in two cases are given.When f,g are balanced functions, GMW-geometric sequences are not only generated easily but also have good correlation property. As a result, GMW-geometric sequences can be applied in direct spectrum code-division multiple access communication systems. At last correlation functions of GMW sequences in four casesare given out as corollaries.
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  • Analysis of Pinning Controlling Spatiotemporal Chaos of Unsymmetrical Coupled Map Lattice
  • Li Xiangming，Xiao Jinghua Zhu Hongbo
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 50-54.
  • Abstract ( 189 )     HTML     　　
  • Controlling spatiotemporal chaos in unsymmetrical coupled map lattice is investigated. The stability of the CML with pinning controlling is analyzed with linear analysis, and thecoupled gradient effect on controlling efficiency is analyzed also. The smallestpinning density for controlling a CML to some desired states is given. And the numerical simulations are given. Pinning controlling for unsymmetrical system in more effective then symmetrical system. With same pinning density, the controllingregion is increase with the coupled grade increase.
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  • Testing and Design-for-Testability about Communication Software
  • Luo Hong
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 55-59.
  • Abstract ( 258 )     HTML     　　
  • Software DFT (design-for-testability) is introduced as a new concept for solving problems in protocol developing course and testing course. Some DFT methods about communication software are discussed then. Setcontrol points on SAP (service access point) and add independent test-sequenceintroducer for controlling the system's movement. Set observation points on SAP and use simple output statements as observation apparatus for observing the system'smovement. Use test switches for testing any parts of software that you care about. These methods are very simple. Additional software caused by DFT is very little and doesn't affect the system's normal movement, but they can improve the software testability greatly.
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  • A Security Analysis of an Authenticated Encryption Scheme
  • Li Zichen, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 60-62.
  • Abstract ( 226 )     HTML     　　
  • By the character of homorphism function, the authorsanalyze the security of the authenticated encryption scheme, depended on the character of one-way function and proposed by Horster, Michels and Petresen, withlow communication costs, and present a known plaint-cryphertext attack method.At the end we get the conclusion that if the one-way function is homomorphism,the scheme is insecure.
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  • The Investigation of Constructs Preventing Active Attack in Key Distribution Protocols
  • Song Ronggong, Hu Zhengming, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 63-67.
  • Abstract ( 204 )     HTML     　　
  • Based on the investigation of the factors preventingactive attack in key distribution protocols, we propose the basic constructs preventing active attack, and analyze their rationality.It provides a simple andeffective method for the design and analysis of key distribution protocols.
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  • Dynamic Heuristic Minimal Spanning Tree Multicast Routing Algorithm
  • Long Yuanxiang, Liao Jianxin, Chen Junliang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 68-72.
  • Abstract ( 216 )     HTML     　　
  • Video conference is a welcome multimedia service.Howto choose appropriate conference routes and optimize the configuration of conference for reducing cost of conference is key to popularize the video conferenceservice.Aims at characteristics of video conference, introduces a multicast algorithm based on Steiner tree and dynamic greedy algorithm, points out their lack.Then, the paper presents a dynamic heuristic minimal spanning tree multicast routing algorithm, gives its implementation steps, analyzes its performances, and proves that the algorithm is appropriate and feasible.The experimental results show that the cost of spanning tree by the algorithm is a close approximation to optimization.
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  • Effects of the Electric Contact Failure of DDF in Optical Communication System
  • Sun Baisheng, Zhang Jigao
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 73-81.
  • Abstract ( 332 )     HTML     　　
  • Based on the contact theory and the analysis of the failed connectors collectedon spots, The factors which can result in contacts failure and proposes a new physical model of contacts in high frequency is discussed. The theoretical studiesof the relationship between the contact failure of DDF and the error codes in optical communication systems are given.
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  CORRESPONDENCES

  • A Simplified Method for Decoding RS Code
  • Tian Baoyu, Wu Weiling, Wang Daqing, Song Jichang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 78-81.
  • Abstract ( 218 )     HTML     　　
  • A simplified method for decoding RScode capable of correcting two symbol errors is presented, based on solution toquadratic equation over finite field.Compared with conventional RS decoder, this method increases decoding speed and simplifies decoder structure.
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  • The Multimedia Mail System Using the H.323 Set of Standards
  • Sun Bin, Yu Bin, Zhu Xianghua
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 82-85.
  • Abstract ( 201 )     HTML     　　
  • A system to provide multimedia mail service for H.323 terminal is introduced. The system gain/send the multimedia information through the channel established by H.323 call procedure with the terminal, the multimedia information isstored and managed as multimedia mail in the system multimedia mail box. Using this method, this system gives a better solution of providing mail service for real time multimedia terminal. This paper will introduce the function structure ofthis system, mainly the implementation of the server side software. We will discuss some main questions in the implementation.
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  • An implementation of the LAN Emulation Protocol Using Object-Oriented Method
  • Zhang Lingyun, Yu Hao, Ding Wei
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 86-90.
  • Abstract ( 179 )     HTML     　　
  • With the development of the ATM technology, ATM networks will be inevitably to interwork with existing LAN networks.Aimed at using Object-Oriented language to implement LAN emulation protocol, which is defined by the ATM Forum.A way was proposed in our paper using the Object-Oriented method to design and implement the access to ATM networks.The inheritance and efficiency of the program is much higher than other's.
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  • The Processing of Sampling Datas from A/D Converters
  • Tang Yang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(3): 91-98.
  • Abstract ( 220 )     HTML     　　
  • For repressing effectively the influence of random disturbance on the stability of the A/D sampling data, a method is proposed to process those datas before the succedent applications.The algorithm is proved exactly and the details are investigated.The numeral fluctuation can be restrained satisfactorily on the processed output datas.In the above datas the sampling datas are subjoined iteratively and dynamically, and the relationship is logarithm between the convergence precision and the operation number.
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