Current Issue

• • 2004, Vol. 27 No. 5 Published date:28 May 2004 Last issue Next issue

  SUMMARIZATION

  • Study of Identification in Quantum Key Distribution
  • WEN Qiao-yan, GAO Fei, ZHU Fu-chen
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 1-6.
  • Abstract ( 360 )     HTML     　　
  • This paper gives a particular description of several main quantum identification protocols, comes up with the demands of quantum identification, and then points out the direction in its development.
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  PAPERS

  • MSE-OFDM: A Packet Based OFDM System for Broadband Communications
  • WU Yi-yan,　WAN G Xian-bin
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 7-14.
  • Abstract ( 296 )     HTML     　　
  • A system level comparison between a conventional OFDM(orthogonal frequency division multiplexing) and the Multi-Symbol Encapsulated (MSE)-OFDM system is presented in this study. An analysis onimpact of frequency offset on the system performance is presented. Comparisonsare made on two different assumptions, i.e., either keeping the symbol size of the MSE-OFDM (i.e., number of the subcarriers) unchanged to increase the bandwidth efficiency, or keeping the bandwidth efficiency unchanged (ratio between CP(cyclic prefix) and useful data transmission time) for system robustness to synchronization errors, i.e., frequency offset. In the first case for CP-reduced MSE-OFDM, bandwidthefficiency is improved due to a reduced number of CPs inserted between OFDM symbols. For the latter case of FFT size-reduced MSE-OFDM, robustness to synchronization errors is improved considerably due to the smaller number of subcarriers. The proposed system is of particular interest for fixed wireless systems and digital subscriber loops (DSL). Large frame size can be used in these applications, due to the static nature of the channel conditions. Implementation complexity ofthe MSE-OFDM system is also discussed.\=Key words:orthogonal frequency division multiplexing; peak to average power ratio; bandwidth efficiency; frequency domain equalization; intersymbol interference; interchannel interferenceCLC number: TN911 Document code: A   收稿日期: 2004-07-08   作者简介: Y. Wu Fellow, IEEE, and X. Wang Member, IEEE are with Communications Research Centre Canada, Carling Ave., Box 11490, Station H, Ottawa, ON K2H 8S2 Canada. E-mail: yiyan.wu, xianbin.wang@crc.caMSE-OFDM——一种基于分组的OFDM宽带通信系统吴奕彦, 王现斌(加拿大渥太华通信研究中心, 渥太华 11490, 加拿大)摘要: 本文对传统OFDM和多符号封装(MSE)-OFDM进行了系统比较。分析了频率偏移对系统性能的影响。比较在2种不同的假设下进行,即或者保持MSE-OFDM的符号长度(即子载波数)不变以提高频带利用率,或者保持频带利用率(CP与数据有效传输时间之比)不变以改善系统对抗同步误差,即频率偏差的能力。在第一种降CP的MSE-OFDM情形下,由于减少了OFDM符号之间插入的CP数,频带利用率得以提高;对于后一种降FFT长度的MSE-OFDM情形,更少的子载波数显著改善了对同步误差的抵抗能力。本文提出的系统尤其适合于固定无线系统和数字用户环路(DSL)。在这些应用中,由于信道环境的静止特性,可以使用很大的帧长度。文中还讨论了MSE-OFDM系统的复杂度。
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  • ACK Based Scheduling Algorithm for 1xEV-DV
  • YANG Hong-wen, HU Man-li, GUO Wen-bin, YANG Da-cheng
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 15-20.
  • Abstract ( 299 )     HTML     　　
  • Based o n the st ro ng co rrela tion between the ARQ ( automatic repea t request) acknow ledg ement s ( ACK /N AK) a nd the fo rw ard cha nnel quali ty , a nov elscheduling scheme i s propo sed fo r 1xEV-DV forw ard packet data t raf fic. The proposed scheme schedules the forw ard packet da ta channel ( F-PDCH) o nly w ith the ACK /N AK feedbacks, the implicit channel quali ty info rmatio n feedback i s no mo rerequired. Compared to the conv entional desig n, the propo sed scheme replace the cha nnel quali ty informa tion feedback channel ( R-CQ ICH) with dense feedbacks on ARQ acknow ledge channel ( R-ACKCH) . The feedback is used for both Hy brid ARQ o peratio n and the multi-user packet scheduling. Simula tion resul ts indica te that , under the propo rtio nal fairness co nst raint s, the sy stem throughput wi th new alg orithm o utperforms the conv entiona l algo ri thm.
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  • Weight Hierarchies of Linear Codes Satisfying the Break-Chain Condition
  • WANG Yong-hui, CHEN Wen-de
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 21-25.
  • Abstract ( 244 )     HTML     　　
  • The weight hierarchy of a linear [n,k;q] codeC over GF(q) is the sequece (d₁, d₂, … d_k), where d_r isthe smallest support weight of an r-dimensional subcode of C. The weight hierarchies of linear codes satisfying the break-chain condition containing many abutal break points of general dimension over GF(q) are investigated. First,a simple necessary condition for a sequence to be the weight hierarchies of suchcodes are given. Further, by using the finite projective geometry method, explicit constructions of such codes are given, showing that in almost all cases, thenecessary conditions are also sufficient by properly choosing the subspaces inthe projective space. And so, almost all the weight hierarchies of such codes are determined.
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  • Hierarchical Queueing Based Optical Buffer
  • WAN G Zhen-kai,　CHEN Jian-ya,　GU Wan-yi
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 26-30.
  • Abstract ( 262 )     HTML     　　
  • A hierarchical queueing based optical buffer (HQOB) is presented for all opticalpacket switches. HQOB is in a layered structure. Each layer is a fiber loop buffer group, whose fiber length is multiple of the previous layer. As packets arenormally stored in queues, the middle part of a queue can be moved between adjacent layers when needed. Thus HQOB can simulate normal packet buffer with QoS support using much less FDL(fiber delay line) segments(proportional to the logarithm of the buffer depth). The amount of FDLs can be further reduced when WDM(wavelength division multiplexing) is employed.
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  • An Algorithm on Inverse Kinematics of 1P5R SurgicalRobot
  • YU Yan-qiu, LIAO Qi-zheng
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 31-35.
  • Abstract ( 321 )     HTML     　　
  • The inverse kinematics of a 1P5R robot used for surgery is studied. Anovel algorithm for the inverse kinematics is derived from six simple polynomial equations. After eliminate several unknowns the equation with only one unknownvariable is obtained, which is a 12^th degree polynomial equation in one unknown. This means that the robot has 12 different possible configurations. Finally, the result is verified by a numerical example.
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  • Performance Analysis of Space-Time Transmit Diversitywith Imperfect Channel Estimation over Correlated Nakagami Fading Channels
  • NI Zhi, LI Dao-ben
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 36-10.
  • Abstract ( 250 )     HTML     　　
  • In this paper, w e inv estigate the impact of imperfect cha nnel estimation and correlated Na kagami fading channels o n th e perfo rmance of STTD( space-time tr nasmi t div ersi ty) ca reful ly. Fi rst ly, o n the assumption o f channel estimatio n erro r wi th Gaussian dist ributio n, the sig nal to noi se ratio at the receiv ers i s analyzed.Previous w ork on performa nce analysis of ST TD has been rest ricted to unco rrelated Rayleig h fading. In this paper, w e deriv e a closed-fo rm bit erro r probability ( BER) ex pression fo r S TTD wi th tw o t ransmi t antennas and arbi trary number of receiv eantennas under co rrela ted Nakagami fading channels wi th arbi trary co rrela tion v ariance mat rix. Finally, numerical result s from simulations are given to suppo rt the mathematical dev elopment of the BER expression, and show n that there is af loor for BER at high SN Ras the cha nnel estimation erro r to channel gain ra tio ( EGR) increases. We found that the speed fo r BER performa nce deg rada tion decreases fai rly slow ly when EGR < - 15 dB, and the ef fect of the cha nnel correlatio n i s not sig ni ficant for co rrela tio n coef ficient around 0. 4. The ef fect of fading pa rameterm of Nakagami dist ributio n on the performa nce of STTD i s al so discussed.
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  • Fast Frequency Offset Estimation in OFDM System
  • ZHANG Zhong-shan, LIU Xiao-ming, ZHAO Ming,
    LIU Yuan-an, GAO Jin-chun
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 41-44.
  • Abstract ( 287 )     HTML     　　
  • A new carrier frequency offset estimation scheme in orthogonal frequency division multiplexing(OFDM)system is proposed.The carrier frequency offset estimation includes acquisition and tracking,and acquisition as well as timing synchronization can be performed simultaneously with high accuracy.The maximum acquisition range can be up to one half of overall signal bandwidth.The proposed tracking estimator is a maximum-likelihood estimator,and in AWGN channel,about 7.27dB improvement is obtained compared to the Schmidl's algorithm when N=128; in multipath channel,the proposed algorithm works well at moderate SNR.
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  • A Dynamic Routing and Wavelength Assignment Algorithmin Waveband Switching Optical Network
  • SONG Hong-sheng, XU Yun-bin, JIN Wen-yan, GU Wan-yi
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 45-49.
  • Abstract ( 291 )     HTML     　　
  • The characteristics of connections in waveband switching (WBS) optical network are analyzed, and a new dynamic routing and wavelength assignment algorithm suitable for WBS network is proposed, which is called the longest waveband path (LBP) algorithm. In order to effectively save network cost and reduce network blocking probability, LBP algorithm tries to use three ways with different priorities to set up a new wavelength connection, which are using the longest established waveband path, establishing a new end-to-end waveband path and establishing a step-by-step wavelength path. In this paper, the blocking performances of WBS network are compared with different node switching ratios and different routing methods using LBP algorithm. Moreover the optimal switching ratios of multi-granularity optical cross connect (MG-OXC) are analyzed under different traffic loads. These results are instructive for the design of WBS network.
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  • A Distributable Traffic-Based MPLS Dynamic Traffic Distribution Scheme
  • YU AN Gang ,　PEN G Yong ,　CHEN G Shi-duan
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 50-55.
  • Abstract ( 294 )     HTML     　　
  • A new parameter, which is based on label switching path (LSP) queuing delay and packet loss rates and refered to as distributable traffic(DT), is defined to reflect the load of LSP comprehensively. Then based on DT, an adaptive multiple protoced label switching (MPLS) traffic distribution scheme is proposed to perform traffic distribution in MPLS networks, which is refered to as DTMD. Only label edge routers (LERs) are required to perform special function in DTMD scheme, so the scalability is maintained. Simulation results indicate that the new proposed scheme can perform stable even in dynamic network environment, and it can distribute the traffic onto parallel LSPs more evenly and fairly when compared to delay-based schemes.
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  • The Spectrum Structures of the Excited States for Be-Like Ne⁶⁺
  • HAN Li-hong
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 56-59.
  • Abstract ( 303 )     HTML     　　
  • The Rayleigh-Ritz variational method is used with a multi-configuration-interraction wave function on the bound state 1s²2s²¹S,and the excited states 1s²2s²p¹P^o,1s²2s2p ³P^o,1s²2p^{2 3}P for the berylliumlike Ne⁶⁺. A restricted varia-tional method is used to obtain an additional nonrelativistic energy for these states. The relativistic corrections and mass polarization are taken into consideration in the calculation of total energy. The wavelengths,oscillator strengths and radiation rates are also calculated.
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  • A New Algorithm for Reducing the PAPR of OFDM Signals
  • JIN Xiao-jia, CHEN Bo, LIU Xin, SONG Jun-de
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 60-64.
  • Abstract ( 262 )     HTML     　　
  • On the basis of studying the SLM(selected mapping) and PTS(partial transmit sequences) algorithms,a new algorithm named as subsection mapping is proposed and deduced to reduce the PAPR(peak to average power ratio) of OFDM(orthogonal frequency division multiplexing) signals. The main idea of subsection mapping is to divide the signal sequence intoseveral parts which are called subsequences. By controlling the power varianceof the subsequences the PAPR of the signal sequence can be restricted. The disadvantage of the subsection mapping is that the mapping table has to be stored inthe memory. After the theoretic deduction and numerical simulation, this new algorithm is proved to have better performance for reducing the PAPR of OFDM signals comparing to the SLM and PTS.
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  • A TH-BPSK Ultra-Wide Bandwidth System Based on Different User Using Mutual Orthogonal UWB Waveform
  • LI Yao-min, ZHU Xue-tian, ZHOU Zheng
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 65-69.
  • Abstract ( 216 )     HTML     　　
  • An UWB(ultra wide band) system usually transmits the same UWB impulse for all users. When many users are active in the system simultaneously, the effects of multi-userinterference are great and the system BER(bit error rate) is high. A TH-BPSK UWB system is proposed to decrease the effects of multi-user interference. Each user is assignedadifferent orthogonal UWB impulse of the modified Hermite polynomial function. Due to the orthogonality of UWB impulses, the multi-user interference can be eliminated completely if chip synchronism is assumed and the system BER performanceis enhanced. Simulation results and theoretical analysis indicate that the proposed system has much lower BER compared with the TH-BPSK UWB system using the same UWB impulse.
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  • A Distributed QoS Unicast Routing Algorithmfor PCPO Problem
  • HAN Ling, KONG Ling-shan, ZENG Zhi-min, DING Wei
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 70-74.
  • Abstract ( 281 )     HTML     　　
  • TSQR (two-way selective probing QoS routing), a distributed algorithm for NPCPCPO (path-constrained path-optimization) problem is proposed. Taking example for DCLC (delay-constrained least-cost) problem that belongs to PCPO problem, according to TSQR algorithm, source node sends two kinds of probing messages(MinCProbe1/MinDProbe1, MinCProbe2/MinDProbe2) to destination node based onthe minimum-cost path and the least-delay path between them, and these two kinds of probing messages correspond to two kinds of path-selection operations; themid nodes collect the path information that a message has traversed, and mutatethe message to probe in another direction while sending the message in originaldirection; destination node selects one or more paths from feasible paths set. TSQR can remove loop paths naturally, and has low storage and computation complexity. Simulation results show that TSQR has best path-optimization performance compared with some other referenced algorithms.
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  • Investigation of Uplink Admission Control Schemes in Time Division Duplex-Code Division Multiple Access (TDD-CDMA) System
  • PENG Mu-gen, WANG Wen-bo
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 75-79.
  • Abstract ( 226 )     HTML     　　
  • An advanced uplink admission control mechanism is proposed for TDD-CDMA system, in which the multi-user detection (MUD) technique is adopted. By estimating the increasing interference and system load for new or modified users, the proposed admission control scheme rejects or accepts the user to access the system. With an OPNET-based dynamic system simulator, the performance of TDD-CDMA system is evaluated. The simulation results show that the proposed scheme can improve the system performance and the proper admission control threshold is changed with MUD factor.
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  • Joint Space Diversity with Doppler Diversity in MIMO Wireless Communications
  • WANG Jian-kang, LIU Jiang-hua, LUO Tao, YUE Guang-xin
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 80-84.
  • Abstract ( 235 )     HTML     　　
  • Jointing space diversity with Doppler diversity in MIMO(multiple input multiple output) wireless communicationsis researched in this paper. The MIMO channel model that joints space diversitywith Doppler diversity is set up. Based on it, we show that the maximum diversity order is ML(Q+1). Then, the coding scheme in this situation is proposed. Following this, outage capacity is researched, and simulations are provided to corroborate our theoretical findings.
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  • A Passive RTT Estimate Algorithm for TCP
  • ZHANG Yi-bo, LEI Zhen-ming
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 85-89.
  • Abstract ( 310 )     HTML     　　
  • A pa ssive ro und t rip time ( RT T) estimate alg ori thm called PRE ( passiv eRTT estima te) is proposed for the t raffic mo ni to r devices to estimate RT T of TCP connectio ns in the broadband netwo rk. PRE alg orithm can find o ut sending ro unds of the mo nitored TC P f low acco rding to the estimator of packag e ar riving interv al ( PAI) a nd estima tes RTT by measuring the leng th o f the sending round, which approximately equals to RTT. Ba se on PRE, pa ssive TC P measurement can be deployed in the t raf fic mo nito rs. Both simulation and practical ex periments validate that the a lg o ri thm can estimate RT T properly.
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  • Multi-Services Bandwidth Assignment Algorithm in EPON
  • ZHAN G Yang1 ,　CHEN Xue1 ,　HU AN G Xiang1 ,　DEN G Yu2
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 90-93.
  • Abstract ( 303 )     HTML     　　
  • A nov el bandw idth dy namic assig nment algo ri thm for EPON ( etherent passiv e optical netwo rk) upst ream link is proposed, named integ ra ted periodic and quasi-periodic g ranting DBA ( IPAQG DBA) . The algo ri thm adopts quasi-periodic synchro ni zatio n polling DBA ( dynamic bandw idth assig nment ) and periodic static config ura tion mechani sm respectively fo r ethernet a nd TDM ( time divi sion mul tiplex ) serv ice. The simula tio n result s show that no t o nly the rigid Qo S( quali ty o f service) o f TDM service and the performa nce requirements o f ethernet service can be sa tisfied, but also very high ba ndw idth utilization and go od fai rness can be realized by IPAQG DBA at the same time.
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  • Capacity for Orthogonal Space-Time Block Encoding Channel over Rician Fading Environment
  • LUO Tao, LIU Dan-pu, YUE Guang-xin
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 94-98.
  • Abstract ( 310 )     HTML     　　
  • On the basis of analyzing the received signal-to-noise ratio of orthogonal space-time block codes over Rician fading channel, the average capacity over Rician fading environment for orthogonal space-time block codes is obtained in thispaper. Then the simple but accurate formula for average capacity is further deduced by Porteous's lemma. In comparison to the Monte Carlo and numerical integral, the simulation results show that the approximate value obtained by the formulain this paper is very accurate while it shows much lower complexity.
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  • Analysis of EMI in a Multi-Pins Connector Based on Method of Moments
  • SONG Zhan-hai,　LIU Yuan-an,　LIU Teng-jiao ,　LI Shu-lan
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 99-103.
  • Abstract ( 284 )     HTML     　　
  • A simplified electromagnetic interference (EMI) model is given for a multi-pinsconnector based on the assumption of nearest interaction between pins. Method of moments (MOM) is used in the calculation of per unit length capacitances. Theaccuracy of the model for high frequency signals is discussed. Crosstalk betwenpins are simulated in frequency domain and time domain. Simulating results maybe helpful in the decreasing of EMI in connectors.
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  • Research on Virtual Backbone-Based Distributed Ad hoc Routing Protocol in MANET
  • CHEN G Sheng ,　FEN G Mei-y u,　ZHAN G Xu,　DING Wei
  • Journal of Beijing University of Posts and Telecommunications. 2004, 27(5): 104-108.
  • Abstract ( 315 )     HTML     　　
  • A Virtual Backbone-based Distributed Ad hoc Routing(VBDAR)protocol, which issuitable for large scale Ad hoc networks, is proposed in this paper. This protocol will construct Ad hoc virtual backbone at first, and then running classic Adhoc routing protocols on it. Redundancy messages can be significantly reduced asonly virtual backbone nodes perform routing algorithm. The results of simulation show that it can reduce the number of hops of routes, and will effectively improve the performance of services.
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