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25 March 2006, Volume 27 Issue 3

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academic paper

Address space transformation based on method supporting group Undo

Jiang-ming YANG,Ning GU,Xiao-yuan WU

2006, 27(3):  1-60.  doi:1000-436X(2006)03-0048-09

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An address space transformation based method in replicated groupware systems was reported. It first retraces the document's address space to the state at the time of the operation's generation time and then the operation could be executed directly in this address space. This method could well support any Undo operation by mapping the operation to a certain object node. Finally, the execution process of some Undo puzzles and the intension-violation puzzle and its so-lution are described.

Robust self-tuning active queue management mechanism

HANGHe-ying Z,IAOLi-quan X

2006, 27(3):  7-14.  doi:1000-436X(2006)03-0007-08

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Most of the active queue management (AQM) mechanisms proposed previously were designed based on the simplified linear model of the controlled object. Moreover, their parameters were usually set according to some specific network conditions. So these algorithms had difficulty in obtaining desirable performance once the network conditions changed widely. To address these issues, a new self-tuning AQM algorithm called STR was proposed. STR had the ability of keeping minimum variance between the instantaneous queue length of the router and the desired value by estimating the parameters of the model of controlled object online and adjusting the packet drop probability accordingly. At last, the performance of STR was evaluated through extensive simulations. The results show that STR is robust against the great changes of the network parameters as well as the traffic load.

Analysis of quantization-based watermarking

Jun-yi XU,Chang-zhen XIONG,Dong-xu QI,Ji-wu HUANG

2006, 27(3):  15-27.  doi:1000-436X(2006)03-0015-13

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Necessary and sufficient conditions for robustness to the public watermarking algorithm and its upper limit of attack-resistance energy were given, which supplied a gap that there was no exact upper limit in the attack-resistance evaluation. Then it analysed change amplitude of the carrier's coefficients and range of the added pattern in fidelity-fixed optimization, which partly solved the problem of protecting watermarking during fidelity-fixed optimization, and pointed out the difference between quantization encoding and common variable information payload and the reasons of difference in information capacity calculation. After that, a vision optimized embedding algorithm and other ten equivalent ones were constructed. And then a quantization watermarking scheme with twice attack-resistance of mod-based embedding algorithms was proposed in the same carrier altered range, which overcomed the disadvantage of low attack-resistance to Mod-based watermarking schemes. Also, it constructed gray level embedding schemes which avoided the transformation from gray value to binary. Finally, the experimental results support the theoretic analysis and presented schemes.

Clone crossover scheme based on N-coding and application of quick optimizing of ADPCM's multi-parameters

HANGGang Z,IEKe-ming X,UOHong-bo G,HAOZhe-feng Z

2006, 27(3):  28-31.  doi:1000-436X(2006)03-0028-04

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Choice of ADPCM's step-size updating factors M had a sea capacity of computing which optimizes multi-variables with complex cost function. The MEA's similartaxis operator was come into by the clone mind evolution algorithm (CMEA), which introduced the clone operator to leave the strong component of the weak individuals to next iterativeness. A novel clone crossover scheme was provided based on N-coding which was used to optimize ADPCM's 8 step-size updating factors with complex cost function. The experiment result showed that the CMEA's SNR was aver-agely reformed about 1.03dB every generation in previous 5 iterativeness, which was exceed MEA's by 0.4dB and over-ran the MEA's from fifth generation. Furthermore, the MEA's quantity of computing is equal to CMEA's by 1.67 and the latter is of anti-prematurity.

Blind signals separation method based on fractional lower order moments

An-qing ZHANG,Tian-shuang QIU,Xin-hua ZHANG

2006, 27(3):  32-36.  doi:1000-436X(2006)03-0032-05

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The impulsive signals or noise with α-stable distribution are characterized by the nonexistence of the finite second or higher order statistics. The traditional blind signals separation (BSS) and ICA approaches were poor perform-ance based on second-order moment or higher-order statistics, even more invalidation. Blind signals separation technique in the presence of impulsive noise was investigated, and a new replace BSS algorithm based on fractional lower order moments was proposed. The algorithm was verified by computer simulation. Simulation results indicate that the new method has good performance to separate signals or noise with α-stable distribution, and very robust.

Multi-weight path routing algorithm of SDH transport network based on principle of the least jumper wire operations

Hui-yong LIU,Luo-ming MENG

2006, 27(3):  37-43.  doi:1000-436X(2006)03-0037-07

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To improve the efficiency of establishing channels, and provide multiple path sets of diverse routing principles, path routing algorithm of SDH networks was discussed. A novel algorithm based on principle of the least jumper wire operations was proposed. Because a connection passed more than one system need jumper wire operations by DXC(digital cross connect) or manually, the less systems mean the greater efficiency. For representing jumper times, a concept of “jumper distance” was defined, and rules of calculating distance sets were given. Through them, network nodes were clarified as several jumper distance sets, and the network topology was simplified. By applying DFS(depth-first search) to distance sets, path routing results could be obtained. An application in an example network was introduced, which shows the algorism is of great value.

New time delay algorithm of time domain equalizer for DSL systems

ANGGuo-liang W,IANGDe-qun L

2006, 27(3):  44-47.  doi:1000-436X(2006)03-0044-04

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In DSL systems, a cyclic prefix (CP) was inserted before every symbol being transmitted, to alleviate the interference between consecutive symbols. In theory, the length of the CP was equal to the memory length of the impulse response of the channel. Using a long CP reduced the data transmission rate of the system largely. To avoid using a long CP, a time domain equalizer was used to shorten the length of the channel impulse response. However, the optimal shortening algorithm of channel impulse response leaded to very high computational complexity. Therefor, a new time delay algorithm is presented, which estimates time delay with channel impulse response convolutes with rectangle sequence, which reduces the computational complexities greatly, real-time implement and shortening SNR is reduced slightly.

Transmission beam-tracking algorithm for FDD wireless systems under close-loop power control

Wen-kun WEN,Yuan-ping ZHOU,Ming-hua XIA,Ning XIE,Huan-hui LIANG

2006, 27(3):  57-63.  doi:1000-436X(2006)03-0057-07

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A downlink transmit beam tracking algorithm with variable step-size was proposed for FDD wireless communication systems. With the closed-loop power control, the transmit beam adaptively tracked the direction of a mobile terminal. The algorithm required neither a dedicated message feedback nor a complex computation, providing a low complexity solution. The tracking error effect due to the power control step-size was analyzed. In comparison to other methods, the proposed algorithm gives a smaller tracking error and a faster tracking speed. Simulation results illustrate the effectiveness and improvements of the proposed algorithm.

Task decomposition and scheduling in large-scale network management

Bo LIU,Jun-zhou LUO,Wei LI

2006, 27(3):  64-72.  doi:1000-436X(2006)03-0064-09

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With large-scale network management becoming more complicated, neither centralized network management nor generic agent-based network management could satisfy the increasing demands. A three-tier network management framework based on multi-agent was provided, which gave multi-agent the collaboration environment. In this framework, a task decomposition algorithm based on task dependence relationship was proposed, according which scheduling method was produced for multi-agent considering the characteristic of network management function. The theoretic analysis and experimental results reveal that using task decomposition method can decrease tasks execution time and save network bandwidth in large-scale network management.

Formal analysis of e-commerce protocols based on game

Jing-hua WEN,Mei ZHANG,Xiang LI

2006, 27(3):  73-78.  doi:1000-436X(2006)03-0073-06

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A new logical method based on game to analyze e-commerce protocols was proposed, the shortcoming of tra-ditional temporal logic that regards protocols as close system to analyze had been overcame. The adversarial and col-laboration in electronic commerce could be described correctly by the new method, and the privacy, security, non-repudiation, fairness could be analyzed. In the end, strict formal analysis for Zhou-Gollmann protocol was made by the new method. These works indicate that the alternating-time temporal logic (ATL) logic based on game is more suit-able to describe and analyze complex e-commerce protocols than traditional CTL.

Ultra-wideband system based on multi-band OFDM

Shi-bing ZHANG,Li-jun ZHANG,Chen XU

2006, 27(3):  79-85.  doi:1000-436X(2006)03-0079-07

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According to the running spectrum of china and the hardware at present, an ultra-wideband system based on multi-band OFDM was proposed. The operating frequency range, transmitted signals, packet format, block diagram of the system were described and modeled. The key technologies, such as multiple access, anti-interference, restraining peak-to-average power ratio, channel estimation and equalization, were studied. The schemes, which include orthogonal frequency division multiple access based on two-stage frequency hopping and orthogonal spreading-interleaving, were put forward. Simulation results show that the system has the advantages in capacity, bit error rate, robustness to interfer-ence and peak-to-average power ratio.

Technical Report

Research on supervised intrusion detection method

Sheng-yi JIANG,Qing-hua LI

2006, 27(3):  86-93.  doi:1000-436X(2006)03-0086-08

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A clustering-based and supervised intrusion detection method was proposed with new distance definition for mixed-attribute data and improved nearest neighbor classification method. The method first clusters training data by one-pass clustering algorithm, then the cluster was labeled with normal or attack by the labels of data belongs to the clus-ter and voting rule. The labeled clusters are used to classifying data. Time complexity of the method is linear with the size of dataset and nearly linear with the number of attributes. It is different from existing supervised intrusion detection methods that the improvement for NN method ensures that the proposed intrusion detection approach can detect unknown intrusions in theory. The experiment results on dataset KDDCUP99 demonstrate that the method has promising perform-ance with high detection rate and low false alarm rate.

Rate control scheme for wireless video transmission

Yun-peng CHEN,Pei-ren ZHANG,Xiu-feng GAO

2006, 27(3):  94-98.  doi:1000-436X(2006)03-0094-05

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When video stream transmitted on wireless channel, packet loss greatly degraded the picture quality. Forward error correction (FEC) and automatic repeat request (ARQ) methods showed good performance in resisting channel dis-turbance and improving picture quality. By analyzing the effectiveness, a formula was given to select appropriate method between FEC and ARQ according to channel status. Then an adaptive hybrid FEC/ARQ rate control scheme was pro-posed. The new scheme can select appropriate error resilience mode and allocate sufficient bits for channel coding by predicting channel status and estimating channel delay. Experiments show this scheme highly improves video quality.

Diversity of MIMO STBC and adaptive OFDMA under correlated fading channel

De-sheng WANG,Guang-xi ZHU,Ying-zhuang LIU,Jun-lin CHEN

2006, 27(3):  99-104.  doi:1000-436X(2006)03-0099-06

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A spatial-temporal diversity theory based on the MIMO STBC system under the correlated fading channel was presented. It was pointed out that the performance of the system was deteriorated because of the channel correlation. The traditional method of analyzing diversity gain and coding gain was very complicated, thus an equivalent SISO model for MIMO STBC system was introduced, which depicted the relationship between the SNR and the eigenvalues of the correla-tion channel matrix. Furthermore, an adaptive OFDM access algorithm for multi-users in MIMO-OFDM system was pro-posed. The simulations show the adaptive algorithm has optimal performance and higher spectrum efficiency than FDMA.

Study of high-temperature superconductivity filters for satellite communication

Juan-xiu LIU,Kai YANG,Zheng-xiang LUO,Shi-rong BU,Jun-song NING,Tian-liang ZHANG

2006, 27(3):  105-109.  doi:1000-436X(2006)03-0105-05

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A microwave bandpass filter on the double-sided HTS YBCO film was designed and fabricated and tested us-ing a new coupling double-resonator. The miniaturization and high performance of electron device was realized using the advantage that the quality factor of HTS film was 1〓3 orders higher than the normal metals. The relations between physical parameters and coupling coefficient of coupling double-resonator were analyzed. The HTS filter fabricated was tested and the anticipated effect was obtained. All of the study results are important to the realization of the miniaturiza-tion of electron device in satellite communication, the reduction of cost, and the development of miniature satellite com-munication system.

Short essay

Low-complexity iterative receiver based on hybrid interference cancellation in MIMO system

Yong-ming HUANG,Lv-xi YANG

2006, 27(3):  110-114.  doi:1000-436X(2006)03-0110-05

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In MIMO communication system the conventional iterative receiver based on soft interference cancellation and MMSE filtering is sensitive to the channel correlation. For this reason a new soft input soft output detector is pre-sented in this paper, which is based on hybrid interference cancellation. Simulation results demonstrate that under the correlated channels this new algorithm has a moderate gain over the conventional one, and the analysis shows that com-pared with the conventional one, the new algorithm has even lower computational complexity under appropriate system configuration.

T-ESPRIT algorithm based on one step EVD

Fu-lai LIU,Jin-kuan WANG,Ge YU

2006, 27(3):  115-118.  doi:1000-436X(2006)03-0115-04

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For estimating the delays of narrowband signals in wireless multipath environments, a T-ESPRIT algorithm based on one step eigenvalue decomposition (EVD) was proposed after discussing the features and performances of delay estimation algorithms. Making use of the algorithm, only one-step EVD was needed to estimate delays. Compared with the previous work, the new approach calls for low computational complexity, but exhibited superior performance, such as smaller estimation error and better robustness to signal-to-noise ratio (SNR) change etc. It was applicable to a lower SNR scenario. The simulation resulted show the effectiveness of the method.

Assessing algorithm for network security performance under PKI system

Guo-dong ZHU,Hong-zhou NING,Yun LIU,De-quan HE

2006, 27(3):  119-123.  doi:1000-436X(2006)03-0119-05

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After analyzing the defense and attack problem of network based on public key infrastructure, an algorithm representing network security performance was presented. This algorithm included four important security parameters:the number of network users(n), the coefficient of key compromised(p), the coefficient of network security(λ) and the degree of network security(s). By analyzing theses parameters of network security performance assessing algorithm, the upper limit value of the coefficient of network security and the number of network users was concluded. These results can be used not only to the construction of network security, but also to the measurement and assessing of network security performance.

Academic communication

New public-key system replaced the LUC system

Xiao-song CHEN,Yong-min TANG

2006, 27(3):  124-128.  doi:1000-436X(2006)03-0124-05

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A new algorithm and a new public-key cryptosystem based on Dickson polynomials was given, which can re-place LUC public-key cryptosystem. This new public-key cryptosystem has the same level of security as the LUC and has less calculation than LUC's.

Study of multi-layer mobile support mechanism in IP network

Bin LU

2006, 27(3):  129-135.  doi:1000-436X(2006)03-0129-07

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Firstly analyzes and divides the existing mobility supporting mechanisms into three types, which are network layer mobility supporting mechanism, transport layer mobility supporting mechanism and application layer mobility supporting mechanism, and then describe the typical mechanism of different layer mobility supporting mechanism. Ac-cording to the above descriptions, a new multi layer mobility support model and mechanism(MLSA-MPT: multiplayer self-adapted mobile policy table) are proposed. By dynamically choosing the different layer mobility support mechanism, the new mechanism can support different mobility requests for multi-service and multi-application.

Secure DSR routing protocol analysis and design

Xiao-jun JI,Chang TIAN,Yu-sen ZHANG

2006, 27(3):  136-140.  doi:1000-436X(2006)03-0136-05

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For designing secure MANET routing protocol, acquiring correct routing information was an important goal. Firstly, security flaws of SRP and Ariadne were analyzed. Then a sufficient condition of secure DSR never returning non-existent route in the presence of active-1-y (y≥1) adversary was presented. Based on this sufficient condition, a new protocol-SDSR was designed. Using strand space as a tool, the security of SDSR was studied, which demonstrated that SDSR satisfied the sufficient condition and would never return non-existence route.