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• • 1999, Vol. 22 No. 4 Published date:10 November 1999 Last issue Next issue

  • A New Dynamic Routing Algorithm in Communication Network
  • Zhang Liang, Liu Zemin
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 1-5.
  • Abstract ( 208 )     HTML     　　
  • A dynamic routing algorithm based on virtue token isproposed to solve the routing problem in communication network, and a Hopfieldneural net is used to realize the algorithm. In the algorithm, the interconnection matrix of the neural net is fixed, and the link costs and call requests of the communication network are mapped into the biases of the neurons. So the Hopfield neural net is easy to be implemented into hardware. Meanwhile, the algorithmcan adjust the balance between shortest path and least load requirements according to the link load status of the network. The simulation results show that thenetwork using this algorithm can accept more connections.
  • References | Supplementary Material | Related Articles

  • Cryptanalysis of Improved Rabin's Crypto-System
  • Li Zichen, Xu Guoai, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 6-8.
  • Abstract ( 168 )     HTML     　　
  • We will analysis the security of the fast digital signature scheme, which is proposed designed by He and Wu based on quadratic residue (called H-W digital signature scheme). And point out that the scheme is insecure. We also present an attack method, which is based on Morrison-Brillhart'sfactoring, on H-W digital signature scheme.
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  • Neural Network for Shortest Path Algorithm and Its Application
  • Ma Chuanshui, Ruan Chuangai
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 9-13.
  • Abstract ( 174 )     HTML     　　
  • A shortest path algorithm based on recurrent neural network (RSP) is proposed, which decreases complexity of connections among units, compared with Hopfield neural network. Simulations show that the algorithm converges to near optimal solutions steadily. While it can be applied to dynamic distributed routingalgorithm based on flow.
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  • Greedy Colouring and Grundy Number
  • Sun Huiquan
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 14-19.
  • Abstract ( 258 )     HTML     　　
  • We discuss the relationship between greedy colouringand Grundy number, and we prove that finding Grundy number of a graph is an NP-hard problem.We also introduce the concept of randomly colourable graphs, implore some properties of them and prove that recognizing a graph to be randomly colourable is an NP-hard problem.
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  • Dual Routing Algorithm based on Hopfield in ATM Networks
  • Yang Ming, Liu Zemin
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 20-24.
  • Abstract ( 168 )     HTML     　　
  • ATM routing with Hopfield networks is studied, By taking advantage of the concept of equivalent capacity, Hopfield networks is employed for optimal routing. Further more, we proposed dual routing mode which combines many features, such as a very good convergence, a relatively low programmingcomplexity and an ability to operate in real time. The simulation result shows that call block rate is greatly reduced under different network topologies and various traffic patterns.
  • References | Supplementary Material | Related Articles

  • Study on Differential GPS Accuracy
  • Wang Xiaoxiang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 25-29.
  • Abstract ( 419 )     HTML     　　
  • To study the relationship of accuracy of DGPS(differential global positioning system) vs. differential distances betweenstations, and vs. the differential pseudorange correction ages by analysis andexperiment. The results show that when differential distance between stations is less than 200 km and the differential pseudorange correction age is less than5s, the influence of various space correlated error and SA(selective availability) on DGPS accuracy is very small so that it can be ignored in ordinary situation,thus the resulting positioning errors are mainly concluded by receiver noise and multipath effect. While the time differential method introduced using the data of one GPS receiver,can effectively correct various error elements and improve the positioning accuracy without the need of setting a differential base station.
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  • Existential Condition Guaranteeing the Solutionof the Two-Scale Difference Equations
  • Yuan Chaowei, Chen Jiafang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 30-33.
  • Abstract ( 197 )     HTML     　　
  • We establish a necessary codition to guarantee the solutions of Two-Scale difference equation 公式, Where K≥2 is an integer, and 公式, if nonzero solution f∈C^L, which is 公式 where 0≤r＜L.
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  • A New Optimization Algorithm Applied to the ChannelAssignment in the Cellular Plan
  • Wu Jing, Song Junde
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 34-38.
  • Abstract ( 192 )     HTML     　　
  • A new algorithm applied to the fixed channel assignment in the cellular pattern is proposed.It is based on the theory of evolutionaryalgorithm.It uses the concept of Multiple Reuse Plan(MRP) and solve the problemof large scale through blocking algorithm, and it is a fast、 efficient and parallel searching method.It has been used in frequency plan system of Beijing University of Posts and Telecommunications.It has been used in several plan projectfor some city, and been adopted because of its good performance.
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  • Objective Measurement of Picture Quality inMultimedia Communications
  • Zhang Yu, Yin Haohui, Zhang Jiamou
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 39-44.
  • Abstract ( 275 )     HTML     　　
  • Several objective methods have been investigated. Twomethods that give a distortion measure for blocking artifacts in images are presented. The first one uses an artificial test signal as the inputa horizontal square signal. The output PSNR is an indication of blocking artifacts. The secondone is based on edge extraction. A statistic is calculated to produce a scalarquantity Q, and then a comparison of Q between the input and the outputis usedto detect blocking artifacts. Methods for evaluation of performance of motion compensation and for measurement of frame rate are also discussed. Furthermore, the “old” analog measurement methods have been found to be useful in detecting some sorts of compression artifacts. Simple and reliable, the analog measurementshould be a complement to modern objective testing system.
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  • A Study on Self-Organizing Wide-Area Network Cache
  • Chen Jun, Liao Jianxin, Chen Junliang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 45-49.
  • Abstract ( 168 )     HTML     　　
  • Integrating cache techniques and active networks, this paper provide a novel distributed and self-organizing wide-area network caches with limited radius. Theconcept of neighbor cache tree and its algorithm is proposed. The max. and themin. storage cost is also analyzed, with the study on the relationship between the partition of memory and the round trip delay, it is proved that there is an optimal cache partitioning point, an average method to find it is discussed in detail.
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  • The Study on SNR-based Hierarchical Coding of Image in MPEG-2
  • Li Lisha, Yin Haohui, Zhang Jiamou
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 50-55.
  • Abstract ( 214 )     HTML     　　
  • In view of the compatibility with the standard and the prospect for application's extending, this paper introduced ways of hierarchical coding based on the International standard MPEG-2. We selected the SNR based hierarchical way as the main emulation mode from the four hierarchical ways which are mentioned by MPEG-2. The SNR based hierarchical way produces two videolayers from one source video. These two layers have different image quality butthe same resolving power in space and time. When decoding , the low layer will be decoded by itself to provide a video with basal quality while the enhanced layer will be used to improve the quality of the video that produced by the low layer. Through experiment, the enhanced effect on the quality of the base layer video is showed to be evident and promising.
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  • Solutions of the Horizontal Field Generated by Lightning with theSurface Impedance Method
  • He Wei, Gao Yougang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 56-59.
  • Abstract ( 189 )     HTML     　　
  • A new method by using the expression for the surfaceimpedance of the earth with finite conductivity presented, and the results of horizontal field calculated from wave tilt and surface impedance with exact expression is compared. The new method is suit for calculating horizontalfield generated by return strokes at distances as close as 200m, while these close ranges the use of the wave tilt expression can cause large errors.
  • References | Supplementary Material | Related Articles

  • The Effects of Asymmetric Links on TCP Performance and Its Solutions
  • Li Huiling, Zheng Wenxing, Hu Zhengming
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 60-64.
  • Abstract ( 211 )     HTML     　　
  • TCP is a transport layer protocol that regulate itsforward data sending through reverse ACKs.In asymmetric network where the bandwidth of reverse link is far less than forward link and the link rate of ACKs is slower than data, TCP data throughput is greatly limited by the reverse limk.Themain reason for this limitation arisen is the bottleneck of ACKs in the reverselink.Serving this as the starting point, this paper presents algorithms to decrease the number of ACKs and to reduce ACK frequency as solutions.These improvingalgorithms may be implemented in both sender and receiver.We also tested them through simulations.
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  • Design Internet Call Waiting Service by Using ComputerTelephony Integration Technology
  • Zhu Xiaomin, Liao Jianxin, Chen Junliang
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 65-69.
  • Abstract ( 180 )     HTML     　　
  • From the interworking between PSTN and Internet point of view, this paper takes incoming call notification service as an example todiscuss interworking schemes.Then a CTI-based scheme is given, comparing with IN-based one.Emphases are particularly put on several key points related to thescheme, which is verified by practice very well.
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  • A Study on the Performance of ABR Source with Source-Bottleneck
  • Zhang Lin, Zhao Peng, Zhang Huimin
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 70-74.
  • Abstract ( 200 )     HTML     　　
  • The effect of a special ABR source, Source-bottleneck source, on the performance of several ABR flow-control algorithms is studied.TM4.0 require ABR source changes its rate according to network'sdemand.But Source-bottleneck source for some reason cannot do this perfectly insome time.If flow-control algorithms cannot discover this, algorithms may distribute more bandwidths to a Source-bottleneck source than it can use.This distribution is unfair to non-Source-bottleneck sources.This article studies several algorithms through ATM simulator and analyses the experimental results.
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  • Some Properties of the S-Boxes of the DES System Concerning theFaithfulness of DES
  • Hu Xibao, Liu Jiyou
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 75-78.
  • Abstract ( 164 )     HTML     　　
  • In the study of the faithfulness of the DES, the properties of the S-boxes were carefully and extensively studied.In this paper, some properties of the S-boxes concerning the faithfulness of the DES within lowerrounds were presented.
  • References | Supplementary Material | Related Articles

  • Spatiotemporal Behavior of One-Dimensional ComplexGinzburg-Landau Equation
  • Wang Shihong, Xiao Jinghua
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 79-83.
  • Abstract ( 236 )     HTML     　　
  • Spatiotemporal behavior of complicated systems in small system size are different from that in big system size. Spatiotemporal behavior in one-dimensional complex Ginzburg-Landau equation is investigation whenthe system size is small. When the system size is increasing, CGLE undergoes vibration solution, standing waves, quasi-periodic states, intermittency. The system size at transition point which the first Hopf bifurcation takes place is analyzed by linear stability analysis. Quasi-periodic states are studied, confirmed to be double frequency spatiotemporal quasi-periodic states.
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  • Disk I/O Scheduling Algorithm of Video Server
  • Fu Xitian, Sun Jing'ao Cai Anni
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 84-89.
  • Abstract ( 201 )     HTML     　　
  • I/O scheduling of video server is discussed.Throughthe optimization of the motion of disk arm and the rotation latency,we get the Bi-SCAN scheduling algorithm.For heterogeneous system,which is required to support multi-rate videos, we put forward CDL and CTL scheduling schemes based on Bi-SCAN.And conditions of admission control of theses schemes are offered.Simulations are performed to test the performance of them.At last an improved CDL scheduling scheme is proposed which is based on bucket control.
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  • A Statistical Method for the Probability of Repeated Callsand the Average Repeated Calls
  • Lin Qining
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 90-94.
  • Abstract ( 212 )     HTML     　　
  • The probability of repeated calls describes the probability of repeated call attempt and the mean number of repeated call describesthe mean number of repeated call attempt made by a telephone user when his callis not successful.They are all very important teletraffic parameters in teletraffic statistics and network management.The definitions and a statistical method for the probability of repeated call and the mean number of repeated calls are given.
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  • On Calculating the Generalized Hamming Weights ofHamming Codes with Simulated Annealing
  • Luo Shoushan, Zhong Yuwei,Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 95-99.
  • Abstract ( 143 )     HTML     　　
  • The cryptographical characteristics of the data transmited in wire-tap channel of type two are described by Generalized Hamming weights of linear codes.The expression of the second and the third orders of support set have been given, and then, by using the simulated annealingneural network, the generalized Hamming weights of Hamming codes have been calculated.The results are the same to their theory values.Finally, some suggestionshave been given to the realization of simulated annealing algorithm.
  • References | Supplementary Material | Related Articles

  • A New Method for Building Partial Key Escrow
  • Song Ronggong, Hu Zhengming, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 100-104.
  • Abstract ( 253 )     HTML     　　
  • On the basis of analyzing the partial key escrow system, a new partial key escrow scheme has been presented, which prevents againstthat the computational complexity in old systems is too height, but also preventsagainst that LED(Law Enforcement Decryptor) is too much power.
  • References | Supplementary Material | Related Articles

  • A Routing Algorithm with QoS Guarantees
  • Deng Zhicheng, Zhao Jianying, Zhouqi, Xu Huimin
  • Journal of Beijing University of Posts and Telecommunications. 1999, 22(4): 105-110.
  • Abstract ( 202 )     HTML     　　
  • Two optimal functions for QoS routing policy have been given, one is connection consumption function, and the other ispath bandwidth fragmentation function. Then we integrate the connection's characteristic and the optimizing utilizing of the network resources into the path selection to achieve an integrated QoS routing algorithm. In the end some simulation result are given.
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