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    25 September 2005, Volume 26 Issue 9
    academic paper
    Internet complex network separation degree analysis based on hops
    Wei-ji SU,Hai ZHAO,Ye XU,HANGWen-bo Z
    2005, 26(9):  1-8.  doi:1000-436X(2005)09-0001-08
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    At the first the infection of the same separation degree to different network's transmission was discussed, then the infection of different separation degree to same network's transmission was discussed by giving an example of small world network; Internet separation degree based on hops was defined. Based on the data that were supported by 30 monitors of global Internet from CAIDA, Internet hops was analyzed by statistic, Internet separation degree was computed. Small world character of Internet was illustrated more amply than the other international research result in this field; Aim at hops and RTT, 10 kinds regression analysis were done and a conclusion was draw that it more accords with power function between hops and RTT, the key parameters were found, which proved Internet complex network transmission is power function. Internet separation degree time sensitivity model (ISDTSM) was created; The model of time series stochastic process of Internet separation degree (MTSSPISD) was created, and then the time evolvement rule of Internet separation degree was discussed; At last, the Internet separation and average transmission time of IP level data during 2008 Beijing Olympic Game were forecast by using model ISDTSM and model MTSSPISD.

    Further research on public-key cryptosystems based on third-order recurrence sequence
    IANGZheng-tao J,Xi SUN,Lei TIAN,Yu-min WANG
    2005, 26(9):  9-12.  doi:1000-436X(2005)09-0009-04
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    Properties of third-order recurrence sequences were investtgated and a new variant of GH public-key cryptosystem was proposed. It is further improved to be a probabilistic public-key cryptosystem. Then security analysis of the proposed schemes were provided. The one-wayness of the proposed scheme was equivalent to partial discrete logarithm in ring extension and its semantic security was equivalent to decisional Diffie-Hellman problem in ring extension. At last efficiency analysis of the proposed schemes were provided, and these two encryption schemes need to transfer 2logN and 4logN- bit respectively.

    Delay constraint supported overlay multicast routing protocol
    Jia-gao WU,Yin-ying YANG,Yi-xin CHEN,Xiao-guo YE
    2005, 26(9):  13-20.  doi:1000-436X(2005)09-0013-08
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    The degree and delay constrained routing problem in overlay multicast was studied, and a new overlay multicast routing protocol called delay bounded tree protocol (DBTP) was proposed. Adopted distributed and tree-first strategies, the protocol enabled members of a multicast group to self-organize into a sourced-based overlay multicast tree. DBTP used a new heuristic local optimum algorithm, which could make trade-off between delay and cost of the multicast tree by adjusting a heuristic parameter. The simulation result shows that DBTP can both achieve the admission rate of members highly under whether static or dynamic node model through choosing a proper value of the heuristic parameter. K

    BGP robustness testing based on RFSM
    Le-chun WANG,Pei-dong ZHU,Zheng-hu GONG
    2005, 26(9):  21-29.  doi:1000-436X(2005)09-0021-09
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    A systematic robustness testing approach was proposed. The testing approach first inspected the disadvantages of the original concept of FSM that mixed the function procedure and the robustness procedure. Then by adding states, events, and transitions to resist various impacts, the RFSM (robustness finite state machines), which an FSM Model has robustness procedures, was constructed. Some important problems of generating negative test cases based on RFSM were also discussed: the characteristic sequence of robustness procedures and the test oracle. Compared with the conformance test suite, robustness testing of BGP-4 (Border Gateway Protocol 4) shows that the error handling coverage of the negative test suite generated by this approach is increased by 54 percent, and the error-detecting capability is enhanced by 2.8 times.

    Separation method of predistortion for Wiener PA
    Kai-ya CHEN,Min-xi WANG
    2005, 26(9):  30-34.  doi:1000-436X(2005)09-0030-05
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    Wiener PA model can be perfectly predistorted by Hammerstein model. According to the structural characteristics of these two models, A separation predistortion method was proposed. The method first separated memory subsystem and nonlinear subsystem from Wiener PA, and then got their corresponding predistortion subsystems by identification algorithm. At last, it combined the two subsystems to a Hammerstein system and then linearized Wiener PA. The method avoied interference between memory and nonlinear factors, This kind of interference can be found in the former methods which is not only complexity, but also leads to slow convergence speed and limited convergence precision. Simulation is made to signify that the method proposed is simple and can get more fast speed and more accurate convergence result.

    Approach to blind synchronization parameters estimation for OFDM systems
    Li-ting GUO,Jin-kang ZHU
    2005, 26(9):  35-40.  doi:1000-436X(2005)09-0035-06
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    A method for increasing the cyclic period of a cyclostationary signal was first proposed. Then based on it, a cyclostationarity-based, blind algorithm for estimating synchronization parameters in the OFDM system was presented. Finally through analyzing this algorithm, a method was got, which can not only estimate a timing offset which is not an integer multiple of one OFDM sample duration, but also enlarge the frequency offset estimation range, thus, a frequency offset estimation over the entire bandwidth of the OFDM system is possible. Theory analysis and simulation results are provided to show that the proposed algorithm can get more accurate synchronization parameters estimation with few OFDM symbols, meanwhile it is immune to the noise and adapts to the fading channel.

    Novel algorithm of maintaining packet order in two-stage switch
    Xiao-ning ZHANG,Du XU,Le-min LI
    2005, 26(9):  41-45.  doi:1000-436X(2005)09-0041-05
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    To enhance the scalability of high performance packet switches, recently a two-stage load-balanced switch was introduced by Zhang, in which each stage used a deterministic sequence of configurations. The switch was simple to be scalable and had been proved to provide 100% throughput. However, in its basic fabric, the load-balanced switch may mis-sequence the packets. A new algorithm called FFS (full frame stuff) was proposed in this paper, which maintains packet order in the two-stage load-balanced switch and has excellent switching performance (in terms of mean delay and throughput).This algorithm is distributed and each port operates independently.

    Performance analysis of a MOE blind adaptive space-time multiuser detection algorithm
    Ling-yun LU,Yang XIAO
    2005, 26(9):  46-52.  doi:1000-436X(2005)09-0046-07
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    A novel space-time multi-user detection algorithm was proposed, which combined a power of covariance matrix R technique with MOE blind adaptive space-time multi-user detection. Moreover, the performance of the improved MOE blind space-time multi-user detector was analyzed, according to the effect of white noise, data sample number and positive integer u in cost function. The theoretic analysis and simulation results show that the performance of the novel multi-user detection method asymptotically converge to the MMSE blind space-time multi-user detector on condition that smaller noise variance, larger enough data sample number and u→∞.

    Performance of full-rate and partial-diversity multiple antennas space-time block code with low complexity
    Xiang-bin YU,Da-zhuan XU,Guang-guo BI
    2005, 26(9):  53-59.  doi:1000-436X(2005)09-0053-07
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    On the basis of existing full-diversity space-time block coding (STBC), two full-rate complex orthogonal STBC schemes for multiple antennas were proposed. One was based on time division duplex (TDD) mode; the other had general application without being limited in TDD mode. Meanwhile, Turbo coding was adopted to improve the performance of proposed schemes further by utilizing its good ability to combat the burst error of fading channel. Compared with full-diversity multiple antennas STBC schemes, the proposed schemes could implement full rate, lower complexity and partial diversity; and had more spatial redundant information. Thus the concatenation of Turbo coding could effectively compensate for the performance loss due to partial diversity. Simulation results show that on the condition of same system throughput and concatenation of Turbo code, the proposed code schemes have lower bit error rate (BER) than those low-rate and full-diversity codes.

    Dynamic router and wavelength algorithm based on a VMC-genetic algorithm and dynamic network load balance in optical network
    Wei LI,De-xiu HUANG,De-ming LIU,Jun HE
    2005, 26(9):  60-67.  doi:1000-436X(2005)09-0060-07
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    A novel dynamic router and wavelength assignment (RWA) algorithm for the dynamic wavelength router optical network (WRON) was presented here. By revising the weight of Dijistra algorithm connected with the network traffic under Poisson distribution, a dynamic weight Dijistra algorithm based on the optical network load balance used for the router searching sub-problem was proposed. In it, the router table was refreshed timely based on the network traffic. For wavelength assignment sub-problem, by revising the mutation and crossover rates of genetic algorithm, a novel quick genetic algorithm called VMCR-GA was used to improve the wavelength searching utility. The effectiveness of this RWA is verified through the simulation on the several networks: it can reduce the network block probability 10% and improve the wavelength utility probability 30%~50% comparing with the RWA with normal genetic (NGA) for router and normal Dijistra algorithm(NDA) for wavelength assignment, And the computing time can reduce dramatically.

    NGI IP service management system architecture and application supporting workflow management and policy management
    Ruo-ying ZHANG,Luo-ming MENG,Xue-song QIU
    2005, 26(9):  68-74.  doi:1000-436X(2005)09-0067-07
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    In order to realize the service process automation, and scalable and dynamic service management of NGI service, and adapt to the new service and efficient service management, on the basis of WfMC workflow reference model and IETF policy framework, the architecture of NGI IP service management system supporting workflow management and policy management was proposed. The components and their functions were analyzed in detail. And based on this architecture an application scenario instance of the fulfillment process flow of NGI IP service was given.

    Technical Report
    Algorithm to design UWB pulse based on the peak frequency
    Wei-xia ZOU,Chun-qing ZHANG,Zheng ZHOU
    2005, 26(9):  74-78.  doi:1000-436X(2005)09-0074-05
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    A new pulse design algorithm was proposed to generate UWB pulse based on the relation among the peak frequency of Rayleigh monopulse, the pulse shape parameter α and the order of differentiation n. Not like other algorithms that only work out one pulse, the proposed algorithm can lead to the design of a myriad of pulses that are compliant, namely, it can figure out all α which satisfy the regulation and give out the range of α.

    Application of microwave six-port in software radio
    LAN ZHANG,BING WANG,KEJIN FENG
    2005, 26(9):  79-84.  doi:1000-436X(2005)09-0079-06
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    Common formulas of six-port demodulation orthogonal modulation signals was educed. The results of simulation in demodulation QPSK, 16QAM, π/4QPSK modulation signals are well agreement with the theory analysis. Moreover, the influence of the character of 90°hybrid bridge in six-port was studied. For QPSK signal , the result imply demodulation characteristic degrade less 0.5dB when amplitude unbalance is less than 0.3dB and phase unbalance is less than 3°.

    Overview
    Video coding techniques for networks
    Wei LIU,Zheng-ming MA
    2005, 26(9):  85-92.  doi:1000-436X(2005)09-0085-08
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    Due to the increasing demands on video services over Internet, video-coding techniques suitable for network has drawn tremendous attention in both academia and industry. The purpose of our study was summarizing the developing of video coding techniques for networks. We gave a particular description of the primary video coding schemes over Internet. We put emphasis on scalable coding techniques and MD coding techniques. After description, we made comparison, and further discussed the possibility of the combination of these techniques.

    Short essay
    Using all-phase Fourier method to reconstruct discontinuous signal
    Xiang-dong HUANG,Zhao-hua WANG,Wen-yuan LI
    2005, 26(9):  93-96.  doi:1000-436X(2005)09-0093-04
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    In order to reconstruct discontinuous signal with the least error by using finite information, the concept of all-phase data processing and the conventional Fourier approximation were combined. By utilizing the coefficients acquired by discrete Fourier transforming the samples of signal and the high harmonic information, all-phase Fourier reconstruction was formed. Theoretical deduction and experimental research show that the waveform reconstructed by all-phase Fourier method has less error than those constructed by conventional continuous Fourier integral approximation and the discrete Fourier reconstruction.

    Performance analysis of Bluetooth packet transmission and adaptive packet selection strategy
    Fan YANG,Ke WANG,Zhi-hong QIAN
    2005, 26(9):  97-102.  doi:1000-436X(2005)09-0097-06
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    Relations between bit error rate and average received signal-to-noise ratio (SNR) in AWGN channel were derived for three modulation modes defined by Bluetooth 2.0+EDR new specification. The function expressions of packet retransmission probability and average received SNR of ACL packets were put forward. The transmission performances of ACL packets, including average throughput, average retransmission times and average transmission delay, were investigated through the retransmission probabilities and characteristics of packets. The Adaptive packet selection strategy in AWGN channel was presented. The maximum throughput was obtained by selecting the appropriate packet types to transmit in different SNRs. The SNR threshold values for packet type switching were also presented. The analysis results and strategy presented adapt to optimizing Bluetooth data transmission performances.

    On the capacity loss of closed-loop MIMO
    Duo ZHANG,Guo WEI,Jin-kang ZHU
    2005, 26(9):  103-110.  doi:1000-436X(2005)09-0103-08
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    In the closed-loop MIMO system model, the mathematic formulae between the closed-loop MIMO capacity loss and the feedback channel rate were deduced. Through simulation results, five important conclusions on the relations between the average SNR, antenna number, outage probability, capacity loss and feedback rate were proposed. The conclusions, which are important to system design, provided the instructions to design and tradeoff the overhead of feedback channel and the closed-loop capacity.

    New fractional cosine transform and its application
    Yong-liang ZHANG,Yi-cheng ZENG
    2005, 26(9):  111-115.  doi:1000-436X(2005)09-0111-05
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    A new Fractional Cosine Transform was proposed. It was a weighted combination of the first two integer-order cosine transforms of the original signal, and it has the same eigenvectors as the cosine transform's, but the different eigenvalues which have a periodicity of two. When the periodicity from two to K was extended, K period fractional cosine transform was obtained. Two algorithms were deduced and the advantages of the new fractional cosine transform were analyzed. At last, the application in digital watermark of aural signals was discussed.

    Academic communication
    Universal active network architecture and prototype application based on mobile agent technology
    Xiao-fei IAO,Jin-sheng LI,Pei-lin HONG,Meng-juan LIU,Zhi-hua XIU
    2005, 26(9):  116-122.  doi:1000-436X(2005)09-0116-07
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    A universal active network architecture based on mobile agent technology was proposed, also a prototype application—active search engine founded on this architecture was put forward. Network simulations of this prototype application prove that this architecture has more merits and better performance on total time for task and network load.

    Performance analysis and simulation of FMT system in the presence of frequency offset
    Wei-hong HU,Zhen-ming GAO,You-jun GAO,Feng XU
    2005, 26(9):  123-128.  doi:1000-436X(2005)09-0123-06
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    Filtered multitone modulation is one of the filter bank modulation techniques. It exhibits significantly lower spectral overlapping between adjacent subchannels. Therefor it can overcome the sensitivities to carrier frequency offset of the traditional multicarrier modulation, such as OFDM. But per-subchannel equalization should be used to compensate the ISI. The results of theory analysis and computer simulation prove that FMT has a better performance than OFDM in the presence of the carrier frequency offset.

    Model of preemptive embedded systems for optimizing real-time performance
    Tao WEN,Ji-yong WANG,Xiao-xia WANG,Xiang ZOU
    2005, 26(9):  129-134.  doi:1000-436X(2005)09-0129-06
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    By analyzing preemptions in embedded real-time systems adopting RM scheduling policy, created a preemption model of periodic real-time tasks. This model described the relationship between overheads incurred by preemptions and the properties of real-time tasks, such as priorities, periods, execution times, deadlines, release times etc. It also showed the relation between the schedulability of the task set and properties of its real-time tasks. Based on the model and taking the idea of parasitism in biology, this paper presented a method of optimizing real-time performance of the embedded systems under the RM scheduling mechanism. This method can reduce preemptions or change the relations of preemptions, decrease overheads to improve real-time performance by adjusting release times of tasks. And then the optimization method underlying the model is evaluated by experiments.

    Vector quantization codebook design algorithm based on hybrid ant colony algorithm
    Xue-hui LUO,Xia LI,Ji-hong ZHANG
    2005, 26(9):  135-139.  doi:1000-436X(2005)09-0135-05
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    An appropriately adapted ant colony system embedded with a simple improved LBG algorithm was proposed for vector quantization codebook design. This algorithm first enhances the optimal solution search capability of ant colony algorithm through the adaptive adjustment of the intercept parameter of the transition probability, and then makes use of the searched results of ant colony algorithm as initial solutions, and use improved LBG algorithm for further search, thus accelerate the convergence of the algorithm. Experimental results show that the new algorithm not only further improve the coding performance, but also decrease the running time.

Copyright Information
Authorized by: China Association for Science and Technology
Sponsored by: China Institute of Communications
Editor-in-Chief: Zhang Ping
Associate Editor-in-Chief:
Zhang Yanchuan, Ma Jianfeng, Yang Zhen, Shen Lianfeng, Tao Xiaofeng, Liu Hualu
Editorial Director: Wu Nada, Zhao Li
Address: F2, Beiyang Chenguang Building, Shunbatiao No.1 Courtyard, Fengtai District, Beijing, China
Post: 100079
Tel: 010-53933889、53878169、
53859522、010-53878236
Email: xuebao@ptpress.com.cn
Email: txxb@bjxintong.com.cn
ISSN 1000-436X
CN 11-2102/TN
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