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    25 February 2008, Volume 29 Issue 2
    Academic paper
    High accuracy channel estimation algorithms for multi-cell joint detection
    Xiao-qin SONG,Ai-qun HU,Ke LI,Qiang XUE
    2008, 29(2):  1-7.  doi:1000-436X(2008)02-0001-07
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    The conventional channel estimation algorithm used in the current TD-SCDMA system can not be expanded to multi-cell joint detection for its low channel estimation accuracy for adjacent cells.Firstly the conventional channel estimator was introduced and the reasons for the performance degradation when extended to multi-cell channel estimation were analyzed.Then three high accuracy multi-cell channel estimation algorithms were proposed for multi-cell joint detection by changing the structure of the channel estimation matrix,based on matched filter (MF),minimum mean square error (MMSE),and a combination of both.Simulation results prove that all of the three newly proposed algorithms have higher accuracy than conventional Steiner channel estimation and thus can improve the performance of the multi-cell joint detection of TD-SCDMA system.

    Conditioned secure access control model based on multi-weighted roles and rules in workflow system
    Jian ZHANG,Ji-gui SUN,Ni-ya LI,Cheng-quan HU,Bin YANG
    2008, 29(2):  8-16.  doi:1000-436X(2008)02-0008-09
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    The traditional RBAC model cannot express complicated workflow secure access control constraint,so a new conditioned RBAC model suit for WfMS (workflow management system)—CMWRRBSAC (conditioned multi-weighted role and rule based secure access control model) was proposed on the basis of multi-weighted roles and rules.Based on the traditional RBAC model,a conditioned RBAC method was discussed on the basis of dynamic role assignment and a new concept of workflow access authorization was defined on the basis of multi-weighted roles.A sort algorithm based on token and a sort algorithm based on weighted roles synthesis were presented in allusion to the problem of multi-roles and multi-users sequence constraint in the process of executing tasks.A rule-based modeling method of separation of duties was discussed and its improved rule consistency check arithmetic was given.

    Real-time image matching for navigation system based on genetic algorithm
    Xue-fei LENG,Jian-ye LIU,Zhi XIONG
    2008, 29(2):  17-21.  doi:1000-436X(2008)02-0017-05
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    In order to meet requirement that scene matching aided navigation system must get aircraft position error real-timely,an image matching algorithm based on genetic algorithm and weighted Hausdorff distance was proposed.In general,the global search in conventional image matching is highly time consuming task.For the non-ergodic search characteristic of genetic algorithm was utilized,the global approximate optimum solution was approached rapidly.Therefore the rapidity of matching search can be improved by our algorithm.Moreover,the weighted Hausdorff distance algorithm based on bifurcations extraction and the corresponding weight formula was proposed.The calculation of matching search can be reduced and the accuracy of matching results can be improved by using the weighted Hausdorff distance as the fitness function of genetic algorithm.Simulation results show that,the proposed image matching algorithm combined with genetic algorithm and weighted Hausdorff distance can satisfy the real-time and accuracy demands of the scene aided navigation system.

    Novel distributed Hash table——BChord
    Yan ZHENG,Hong-wei CHEN,Ru-chuan WANG,Yang WANG
    2008, 29(2):  22-28.  doi:1000-436X(2008)02-0022-07
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    A novel distributed Hash table(DHT) BChord was presented.BChord adopts bi-directional search mechanism of Chord.Though query items of finger table in BChord almost double to Chord,compared with Chord,BChord evidently increases speed at searching of resource and spreading of messages via theoretic proof and simulation results.

    Autonomic grid architecture based on information pool protocol
    Zhi-gang CHEN,Deng LI,Zhi-wen ZENG,Jia-qi LIU
    2008, 29(2):  29-36.  doi:1000-436X(2008)02-0029-08
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    An information pool based grid architecture (IPBGA) was presented.Requests from resources for tasks and appeals from tasks for resources were upgraded as information services by using information pool protocol (IPP).Thus,grid resource management and task scheduling were regarded as information matching by IPP which was adaptive to heterogeneous,dynamic and distributed characteristic of grid system.Dividing virtual organization into information services layer and cooperation layer,it is helpful to build general view of information.Experiments and theory analysis show that information pool protocol of IPBGA is more efficient in searching and dealing with information while bandwidth cost and process cost are less.

    Congestion control algorithm for unreliable unicast traffic
    Li-hua SONG,Ming CHEN,Hai-tao WANG,Huan XIONG
    2008, 29(2):  37-44.  doi:1000-436X(2008)02-0037-08
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    To improve performance in high bandwidth networks when trying to retain fairness,a rate-based congestion control algorithm was proposed for unreliable unicast traffic.Named rate adaptation for unreliable unicast traffic (RAUU),this algorithm aims to preserve appropriate amount of extra packets in networks and to that end it regulates the sending rate in proportion to the difference between actual and expected extra packet quantities.It combines loss and delay signals,and made several special design choices to avoid rate control’s inherent weakness.Theoretical analysis shows that in ideal network conditions,RAUU has and will converge to its one and only equilibrium point.Simulation experiments indicate that RAUU can achieve similar performance as FAST and smooth throughput as TFRC while holding reasonable fairness to TCP.

    Capacity effectiveness of multihop cellular based aggregation network model
    Lai TU,Fu-rong WANG,Jian ZHANG,Fan ZHANG
    2008, 29(2):  45-51.  doi:1000-436X(2008)02-0045-07
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    A multihop cellular based aggregation network model was proposed,and based on network capacity region model,the capacity effectiveness of this model was analyzed.Comparison was made by both analysis and numeric simulation among the capacity regions and unified capacities of three network models:traditional single-hop cellular network,multihop cellular network and aggregation supported multihop cellular.Results show that the aggregation network can improve the capacity of a network even without the help of multicast and multiradio,which proves the rationality of the structure of aggregation network model.

    Establishing scheme and algorithm for dynamic key-path of pair wise key for sensor networks
    Yu-zhou HU,Lei WANG,Zhi-ping CHEN,Xue-dao GU
    2008, 29(2):  52-58.  doi:1000-436X(2008)02-0052-07
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    Security schemes of pair wise key establishment ensure communication security in wireless sensor networks.Dynamic key-path in pair wise key establishment farther increases communication security in the networks.Establishing scheme and algorithm for dynamic key-path in pair wise key for wireless sensor networks were presented based on the encoding peculiarity and high fault-tolerant ability of named H(k,u,m,v,n) (hierarchical hypercube) of cluster distributed sensor networks.Theoretic studies and figures of computer simulation show that the algorithm has good reliability performance and high efficiency,which is suitable for cluster distributed sensor networks.

    Multi-feature based authentication watermarking scheme for MPEG videos
    Deng-pan YE,Yue-yun SHANG
    2008, 29(2):  59-65.  doi:1000-436X(2008)02-0059-07
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    In order to more exactly reflect the MPEG video content,a multi-feature based digital signature by fusing the video temporal feature and motion feature and DCT coefficient feature was constructed,which was embedded into videos as watermarking without increasing the complexity of MPEG coding,and a new multi-feature based MPEG video authentication scheme was proposed.Experimental results show that the scheme is more robust than the single-feature one to the common processing such as code-switching and recompression,while sensitive to the malicious attacks such as erasure and insertion and replacement.It can further locate the corrupt areas.

    Effect of wireless gateway on incoming self-similar traffic
    Jie ZHANG,Yuan-ming WU
    2008, 29(2):  66-70.  doi:1000-436X(2008)02-0066-05
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    In the analysis of the changes as the self-similar cable network data enters the wireless network through wireless gateway,the simulation results show that,the self-similarity does not change when the gateway works on real-time forward or power control mode,and its buffer equals wireless channel capacity; the self-similarity and state duration of EAFRP model will increase when the gateway works on power control mode and its buffer is much greater than wireless channel capacity.

    Location based reliability differentiation service for WSN
    Yong ZENG,Jian-feng MA
    2008, 29(2):  71-78.  doi:1000-436X(2008)02-0071-08
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    How to design reliability differentiated service for missions with different reliability requirements becomes one of hot topics in wireless sensor networks.Combined with location-based routing mechanism,a quantified model without full network topology was proposed to evaluated reliability.By introducing a virtual reference point,the data transfer was limited in a specified area.The reliability function of the area was given.A detailed analysis shows that the function increases quadratically with the distance between the source node and the reference node.Based on the above conclusion,a reliability differentiated service mechanism was proposed.Simulation results show the efficiency of proposed mechanism.

    Research on run-time overhead of RM and improvement
    Ding-ding LUO,Hai ZHAO,Pei-gang SUN,Xi-yuan ZHANG,Zhen-yu YIN
    2008, 29(2):  79-86.  doi:1000-436X(2008)02-0079-08
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    RM algorithm is a classic fixed priority real-time scheduling algorithm,but in most embedded real-time systems,where the workload is composed of many tasks of high frequency and short execution time,the overheads from context-switches of real-time operating system will lead to a low resource utilization rate if RM algorithm is directly used.By studying the preemption relationship of the tasks scheduled by RM algorithm,a model of context-switches overheads is established with task attributes,based on which the run-time context-switches overheads of RM algorithm are reduced by optimizing the release time of the tasks in embedded real-time systems.Finally,the experimental results show the validity of the proposed strategy.

    Efficient ID-based certificateless signature scheme
    Jing-wei LIU,Rong SUN,Wen-ping MA
    2008, 29(2):  87-94.  doi:1000-436X(2008)02-0087-08
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    Using gap diffie-hellman (GDH) groups,an efficient ID-based certificateless signature scheme was proposed,which could solve the key escrow problem through binding two partially public keys with a same identity.In this scheme,PKG was prevented from forging a legal user’s signature because he only generated the partially private key.The security relied on the hardness of the computation diffie-hellman problem (CDHP).Under the random oracle model,the new scheme was proved to be secure against existential forgery on adaptively chosen message and ID attack.This scheme not only eliminated the inherent key escrow problem but also had a higher efficiency than the existing schemes did.

    engineering report
    HVS-based imperceptibility measure of watermark in watermarked color image
    Hong-mei YANG,Yong-quan LIANG,Lian-shan LIU,Shu-juan JI
    2008, 29(2):  95-100.  doi:1000-436X(2008)02-0095-06
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    Imperceptibility of embedded digital watermark reflects the fidelity of watermarked image.The masking of frequency,luminance,texture and color on human vision were analyzed.Based on the color masking and Watson’s JND(just noticeable differences) model,a calculation method of JNCD(just noticeable color differences) for color image was proposed.Then the masking weight for each element of color image was calculated using the JNCD.A new imperceptibility measure of watermark in watermarked color image was proposed based on these masking weights,i.e.CPSNR (color image peak signal to noise ratio).Experimental results show that the quality of watermarked color image calculated by CPSNR is the same as the result judged by human vision,and CPSNR can be used to evaluate the imperceptibility of watermarking methods.

    Improved rule-based backward fuzzy reasoning algorithm
    Wen ZHANG,Gui-xu ZHANG
    2008, 29(2):  101-105.  doi:1000-436X(2008)02-0101-05
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    An improved rule-based backward fuzzy reasoning algorithm was pointed.The algorithm is based on the fuzzy Petri net (FPN) which represents fuzzy production rules.The algorithm is also suit for a class of rule-based systems,i.e.it can deal with the fuzzy Petri net model which results from the real system.Via using the algorithm,one can calculate the tokens of any appointed places which correspond to the true fuzzy values of the relevant propositions.Through practical applications,the advantages of the proposed algorithm compared with those present results obtained by the existed algorithm.

    Research on end hopping for active network confrontation
    Le-yi SHI,Chun-fu JIA,Shu-wang LV
    2008, 29(2):  106-110.  doi:1000-436X(2008)02-0106-05
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    Motivated by frequency hopping for military communication,end hopping tactic was proposed which can mitigate those threats such as DoS and eavesdrop greatly by changing the end information of port,address,timeslot,cryptographic algorithm or even protocol pseudo-randomly during end to end transmission.An active defense model has been established upon end hopping.Then a test-bed has been implemented through mobile agent with a successful solution of synchronization and handoff.The model shows better performance in both theoretical analysis and empirical studies.The work demonstrates that end information hopping tactic is feasible and effective for active network confrontation.

    essay
    Simplified MD-LSD demapping algorithm for BICM-ID systems with multi-dimensional mappings
    Feng-kui GONG,Jian-hua GE,Yong WANG
    2008, 29(2):  111-115.  doi:1000-436X(2008)02-0111-05
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    The soft in soft out MAX-LOG-MAP algorithm of conventional mappings was expanded to the BICM-ID system with multi-dimensional mappings.A multi-dimensional list sphere decoding (MD-LSD) algorithm was also proposed by using the list sphere decoding algorithm of multi-antenna systems.Compared with the MD-MAX-LOG-MAP algorithm,the computational complexity of MD-LSD was decreased significantly.Simulation results show that the performance degradation of the simplified MD-LSD algorithm can be ignored when the list length is in a certain range.

    Relativity analysis on wireless value-added services market and SP regulation
    Da-chuan LI,Hong-bin SUN,Zhan-hong XIN
    2008, 29(2):  116-122.  doi:1000-436X(2008)02-0116-07
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    Number,CI (corporation image) and creativity of SP (services provider),set up a theory model on WVAS(wireless value-added services) market and SP regulation,to research regulation’s impact on SP market were analyed.The model shows that the impact can be classified to four areas:free area,loose area,rational area and restrict area.Through analyzing financial impact of regulation via SP,finds the importance of reinforcing regulation.The last part gives some suggestions by model analysis and experience analysis.

    Academic communication
    Channel estimation method for multi-node amplify-and-forward cooperative communication over frequency-selective fading channels
    Kai YAN,Sheng DING,Ming-hua ZHU,Hai-tao LIU
    2008, 29(2):  123-128.  doi:1000-436X(2008)02-0123-06
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    A training sequence aided least squares channel estimation method was proposed for orthogonal frequency division multiplexing (OFDM) based multi-node amplify-and-forward (AF) cooperative communication over frequency-selective fading channels.The mean square error bound on the proposed method is derived and the optimal training sequence scheme with respect to this bound is also given.In addition,Chu sequence with the optimal power allocation is chosen as training sequence to achieve the minimum mean square error estimation performance.Simulation results confirm the performance of the proposed channel estimation method in multi-node AF cooperative communication scenarios and the superiority of the derived optimal training sequence scheme.

    Research on single carrier signal transmission technology based on channel-detecting in troposcatter communication
    Jian-cun QIN,Chang-jia CHEN
    2008, 29(2):  129-133.  doi:1000-436X(2008)02-0129-05
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    The single carrier signal transmission scheme based on channel-detecting in troposcatter communication was introduced according to the characters of the troposcatter channel.Theory analysis and performance evaluation of the troposcatter modem employing this technique were also presented.Finally,comparison between this modem and systems which adopts the best diversity combination was given,which shows highly accordance with theoretical analyzing.Besides,complexity of troposcatter communication systems can be greatly reduced by adopting this technique,and it has important reference for development of troposcatter communication.

    Blind multiuser detection based on instantaneous mixtures
    Chen ZHAO,Bin GOU,Ke WANG
    2008, 29(2):  134-140.  doi:1000-436X(2008)02-0134-07
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    A blind multiuser detection technique used in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems was proposed.The basic thought is to apply the existing blind source separation (BSS) algorithm to the signal detection in MIMO-OFDM systems.From the viewpoint of frequency bin (FB),the proposed method resolves the application problem of BSS algorithm in the systems with delay.In the meanwhile,the problem of permutation indeterminacy which is brought by the recomposition from separated signals and the problem of the complex scaling indeterminacy caused by the complex signal nature in communication systems are also settled by it.Theoretical analysis and computer simulation confirm that the proposed method is valid.

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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