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- 2001, Vol. 24 No. 1 Published date:10 January 2001 Last issue Next issue
- The Analysis on Asynchronous Frequency-Time Spreading OCDMA System with Modified Prime Code
- MA Wen-hua, ZUO Chao, LIN Jin-tong
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 1-5.
- Abstract ( 312 ) HTML 　　
- A novel frequency-time spreading code by designating the different frequencies to the different mark positions of the modified prime code is proposed.Theoretical analysis demonstrates that the number of the proposed codes can amount fo p³.Cross-correlation and the sidelobe of auto-correlation of the proposed code have relatively lower values.The numerical results show that the asynchronous OCDMA system assuming the proposed code reveal excellent performance in the presence of double hard limiters.
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- Modification of Decoding Algorithm of Turbo Code on Frequency-Selective Channels
- LIN Jia-ru, WU Wei-ling, FENG Zhi-yong
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 6-11.
- Abstract ( 326 ) HTML 　　
- The performance of DS/CDMA systems on multipath fading Rayleigh channels is analyzed. And proposes a modified decoding algorithm of Turbo code on multipath frequency-selective fading channels,i.e.the signal with maximum ratio combiner divides by the all square of amplitudes of the channel,calculate the probability function γ for Turbo code,and then decode the signal as Turbo decoding.Computer simulations indicate that the modified algorithm improves greatly the performance of DS／CDMA systems on multipath frequency-selective fading channels and is a promising algorithm.
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- Implementation of Turbo Decoder Implemented on a 32-Bit Fixed-Point DSP
- JIANG Jun, WANG Li-fang, ZHANG Ping, HU Jian-dong
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 12-16.
- Abstract ( 215 ) HTML 　　
- Based on the thorough analysis of the decoder algorithm of the Turbo code,a Turbo code decoder implemented on DSP (TMS320C6201) is presented. Test results show that the decoder has good performance, which can satisfy the requirement of WCDMA system.
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- Network Outage and Measurement in Telecommunications Network
- ZHANG Xue-yuan, ZHANG Jing, LIANG Xiong-jian, Villy B.Iversen
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 17-21.
- Abstract ( 301 ) HTML 　　
- Based on the definition of network outage, it analyses the causes, which result in network outage, and its propagation mechanism. Then, it provides the characteristics of network outage and its classification. Finally, it proposes a framework of outage measurement for telecommunications network. This new framework should be practical, which need verifying in the network operation.
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- A/B Plane Partition Problem in CCS7 Network and Its Heuristic Solutions
- XIN Zhan-hong, WU Qi-cheng, MO Wen-dong
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 22-27.
- Abstract ( 224 ) HTML 　　
- There is an issue of A/B plane partition of HSTPs in the topology optimization of CCS7 network. It can be formulated into a new kind of graph partition problem. The problem is proved to be NP-complete, so the neural network, the genetic algorithm and the simulated annealing are applied to solve it. In order to make the algorithms comparable, the testing schemes are carefully designed. The computing results for the three algorithms show that the genetic algorithm and the simulated annealing are quite robust for the problem, they can search out the optimum with a larger probability and a higher efficiency.
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- An Efficient Algorithm of Latin Squares Isotopy Classfication
- XU Guo-ai, HU Zheng-ming, YANG Yi-xian
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 28-31.
- Abstract ( 279 ) HTML 　　
- An efficient algorithm for finding the isotopy class of the latin squares is given. According the algorithm, the isotopy class of the latin squares of order n(n<9)are obtained.
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- The New Mechanism for MPLS Supporting IP Multicast
- ZHANG Zhong-shan, LONG Ke-ping, CHENG Shi-duan
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 32-36.
- Abstract ( 235 ) HTML 　　
- A new multicast label distribution mechanism triggered by traffic is provided, and this mechanism is analyzed. The outcome of the simulation verifies that this mechanism make the network's scalability and dynamic property better than the scheme whose label distribution is triggered by control messages.
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- Five Dimension Carving Learning System
- HUANG Ming-ji, WANG Hai-xin, DENG Zhong-liang
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 37-41.
- Abstract ( 215 ) HTML 　　
- A learning machine of five dimension by analyzing the art style characteristic of hand-carving and kinematics characteristic of industry robot is designed.At the same time,a equipment of signal collecting is designed.Comparing with traditional three dimension measurer,It has superiority both the work space and flexibility,and moreover,its cost isn't high.It can note down trustily carving process and provide the data for latter carving style abstracting and learning.
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- Automatic Text Categorization Based on K-Nearest Neighbor
- SUN Jian, WANG Wei, ZHONG Yi-xin
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 42-46.
- Abstract ( 265 ) HTML 　　
- A method that integrates language information and statistical information from the training corpus is put forward. The weight of these characters is computed from three parameters: word frequency, centralized degree, decentralized degree. After training, we get the vector space model of the text categorization. The classification of the input text is decided by K-nearest-neighbor.The result shows that the method improves the accuracy of the categorization.
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- Analysis of STTD Antenna Transmit Diversity for WCDMA
- DU Zhi-min, XUE Qiang, WU Wei-ling
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 47-51.
- Abstract ( 253 ) HTML 　　
- Simple close form expressions for STTD's theoretical performance with or without channel estimation error in flat Rayleigh channel are derived. Simulation comparison between STTD and the two closed loop transmit diversity modes shows that when the maximal Doppler frequency is small the closed loop modes have better performance, but when the Doppler frequency increases this doesn't hold. STTD tends to have a better performance in that case.
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- An Efficient Identification Scheme Based on Discrete Logarithm Assumption
- ZHONG Ming, YANG Yi-xian
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 52-55.
- Abstract ( 258 ) HTML 　　
- A new practical identification scheme based on bit commitment and Schnorr's one-time knowledge proof scheme　is presented. Here the use of Cut-and-Choose method and many random exam candidates in the identification protocol is replaced by a single challenge number. Therefore our identification scheme is more efficient and practical than the previous schemes. In addition, we prove the security of the proposed scheme under discrete logarithm assumption, thus clarify the cryptographic basis of the proposed scheme.
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- QoS Routing Algorithm Based on Weighted Fair Queuing Service Discipline
- LU Guo-ying, LIU Ze-min
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 56-60.
- Abstract ( 255 ) HTML 　　
- With weighted fair queuing service discipline, the complexity of the QoS routing problem could be reduced to that of shortest path (SP)routing without any QoS constraints, and thus the multiple QoS constrained route could be searched in polynomial time. Based the discussion of the complexity reductions and a modified version of Bellman-Ford shortest path, we present a QoS routing algorithm,We give the simulation results and compared to the existing QoS routing algorithms, and thus show the validity of QRBF routing algorithm.
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- New Signature Schemes Based on Discrete Logarithms and Factoring
- WU Qiu-xin, YANG Yi-xian, HU Zheng-ming
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 61-65.
- Abstract ( 245 ) HTML 　　
- Two new digital signature schemes whose security are based on both discrete logarithms and factorization are proposed.The paper also considers some possible attacks to the schemes,shows that the two schemes are more secure than the ElGamal's signature scheme and the Rabin's signature scheme.
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- Performance of Multicarrier DS-CDMA Systems in Correlated Rayleigh Fading Channel
- LI Zong-hao, LOU Zhong-yue, ZHANG Yan, PANG Qin-hua
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 66-70.
- Abstract ( 264 ) HTML 　　
- The performance of a multicarrier DS CDMA system is studied in the correlated fading channel.The formula of the diversity system BER is revised, and through system simulation and numerical calculation, a comparison is made between the performance of MC-DS-CDMA system and that of the single-carrier Rake system in the channel with an exponential power delay profile.
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- Study of V5 Interface Conformance Test
- ZHONG Yu-wei, GUO Zhi-gang
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 71-75.
- Abstract ( 223 ) HTML 　　
- We first introduce the concept of V5 interface and V5 protocol, development of V5 interface and merit of V5 interface;then we describe the basic concept of the conformance test and correlation technology;At last integrating the this two technology, we discuss some problem of V5 interface conformance test,as same time bring forward my options.
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- The Effect of PSP Bandwidth on PMD Compensation in WDM System
- MAO Bing-cheng, ZHAO Rong-hua
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 76-79.
- Abstract ( 239 ) HTML 　　
- The effect of the fiber's PSP bandwidth on the first order PMD compensation and propoing two methods to compensate the first order PMD in WDM system based on the first order PMD compensation methods are analyzed.The advantages and disadvantages of the two methods are also compared.
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- A Method of Variable-Rate Modulation on Rayleigh Fading Channels
- WANG Hai, SONG Jun-de
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 80-83.
- Abstract ( 210 ) HTML 　　
- Proposes a variable-rate modulation scheme for wideband data transmission on the Rayleigh fading channel to improve the spectral efficiency. It puts emphasis on the fading rate and the block size. Based on the simulation, a feasible method of the variable-rate modulation for wideband mobile is presented.
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- Antenna Diversity for an Improved OFDM System
- TONG Xue-jian, JI Hong, YUE Guang-xin
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 84-87.
- Abstract ( 225 ) HTML 　　
- An improved OFDM system is proposed: N-points-FFT is divided into n groups. The symbol is arranged according to orthogonal design theory at transmitter, and the multi-antenna can achieve the maximum signal power by appropriate combination method at receiver. The performance is improved greatly by analysis and numerical simulation.
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- An Adaptive Four Dimensional Kalman Filter for Doppler Frequency Tracking
- WANG Xiao-xiang
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 88-91.
- Abstract ( 269 ) HTML 　　
- With the carrer phase of received high dynamic signal calculated by a Tyler series, a weighed four dimensional extended Klman filter is given to track the carrier phase and varies steps of Doppler frequency.To practise the filter,its state transfer matrix and the dynamic noise covariance matrix is derived in detail.Finally the computer simulated tracking result and analysis is given.
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- A NetMeeting-Based Integration of Call Center and Web Scheme
- JIANG Xian-xin, ZOU Hua, WANG Bai
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 92-95.
- Abstract ( 238 ) HTML 　　
- The issues related to the integration of call center and web technologies is discused and a brief introduction to NetMeeting 3.0 SDK is given. A NetMeeting-Based solution is provided and analyzed.
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- Implementation and Application of Fuzzy Case-Based Reasoning
- DU Jian-feng, LI Lin, SONG Jun-de
- Journal of Beijing University of Posts and Telecommunications. 2001, 24(1): 96-98.
- Abstract ( 312 ) HTML 　　
- Inferring mechanism is one critical technique to simulate the thought of human being. This paper researches on the realization and application of case-based reasoning and provides an example. Introducing a fuzzy inference algorithm based on the fuzzy relationship metric, one model of case representation and fuzzy matching algorithm to realize the case-based reasoning is put forward. The application of fuzzy case-based reasoning in a GSM optimization expert system is analyzed.
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