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    25 April 2007, Volume 28 Issue 4
    Academic paper
    Performance of multiple amplitudes differential space-time block coding scheme concatenated with channel coding
    Xiang-bin YU,Sheng-nan ZHANG,Guang-guo BI
    2007, 28(4):  1-8.  doi:1000-436X(2007)04-0001-08
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    By introducing multiple levels quadrature amplitude modulation and matrix transform method, a multiple am-plitudes differential space-time coding (DSTC) scheme was developed. The scheme can avoid the performance loss of conventional DSTC schemes based on PSK modulation in high spectrum efficiency, and it can be applied to non-square code matrix. Compared with conventional PSK based single amplitude DSTC schemes, the developed scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes. Moreover, it has linear decoding complexity, and higher code rate. Also, the performance of our DSTC scheme concatenated with channel codes was given. The simulations results show that our scheme has lower BER when compared with single amplitude DSTC schemes. And multiple amplitudes DSTC concatenated with channel coding also outperform corresponding single amplitude DSTC.

    Cryptanalysis of an efficient group signature schemen
    Rong-bo LU,Heng-nong XUAN,Da-ke HE
    2007, 28(4):  9-12.  doi:1000-436X(2007)04-0009-04
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    The security flaws of the group signature proposed by Zhang Jianhong and etc. was analyzed. It pointed out that the group signature was not untraceable for the revocation center could not open a valid group signature. A coalition attack that the manager and the revocation center could conspire to generate valid group signatures and impose them on an arbitrary member of the group was presented. The security analysis show that the scheme is insecure.

    Experimental and simulation study on convolutional interleaving with coding for optical wireless communication system
    Xiao-zheng SONG,Lu LIU,Jun-xiong TANG
    2007, 28(4):  13-17.  doi:1000-436X(2007)04-0013-05
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    Intensity fluctuations induced by atmospheric turbulence impair the performance of optical wireless commu-nication significantly. To mitigate these negative effects, channel coding scheme of convolutional interleaving with (1/2, 7) convolutional coding was studied for the optical wireless communication system. Moreover, optical terminals and com-munication circuits had been designed for outdoor optical wireless communication using OOK modulation on 785nm semiconductor laser. The experimental results correspond well with the simulation prediction that the error control coding can improve the quality of the optical wireless communication system under weak turbulence. In addition, by increasing the interleaving depth, the impact of long deep fade durations can be further reduced.

    Edge-based image fusion algorithm with wavelet transform
    Jing LIAN,Ke WANG,Guang-xin LI
    2007, 28(4):  18-23.  doi:1000-436X(2007)04-0018-06
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    An edge-based image fusion algorithm with wavelet transform was proposed, the principle of choosing high frequency and low frequency coefficients were designed respectively. The wavelet coefficient local model maximum method and the defined correlated signal intensity ration was used to fuse the high frequency component, when choosing the low frequency coefficient, the method which used is based on edges of image, selecting the pixels that might on the edges possibly from original image. The experimental results show that the fusion rule of our proposed method is effec-tive.

    ICI suppression and frequency-domain Turbo equalization for MIMO-OFDM systems over doubly-selective channels
    Wei-wei YANG,Yue-ming CAI
    2007, 28(4):  24-31.  doi:1000-436X(2007)04-0024-08
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    Based on the analysis of the ICI generation mechanism for MIMO-OFDM systems over doubly-selective chan-nels, a novel frequency-domain ICI suppression scheme and its reduced complexity scheme were proposed, aiming to maximum shortening the signal to inter-carrier interference plus noise ratio (MSSINR). Additionally, the Turbo equaliza-tion to MIMO-OFDM systems was applied over doubly-selective channels, and a new frequency-domain Turbo equaliza-tion (FTE) scheme was proposed based on frequency-domain ICI suppression. Numerical results were also presented to compare the performance among different schemes.

    Design and analysis of a novel fair payment protocol in mobile environments
    Xia LIU,Tian-long GU,Rong-sheng DONG,Yun-chuan GUO
    2007, 28(4):  32-37.  doi:1000-436X(2007)04-0032-06
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    A novel fair payment protocol in mobile environments was presented, which combined the payment protocols in fixed networks and considered the characteristics of mobile devices and wireless networks. The protocol was analyzed by model checker and compared with other payment protocols.The results show that the novel protocol has fairness, con-fidentiality and high efficiency and it is suitable for mobile environments.

    Method for anomaly detection of user behaviors based on hidden Markov models
    Shu-yue WU,Xin-guang TIAN
    2007, 28(4):  38-43.  doi:1000-436X(2007)04-0038-06
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    A method for anomaly detection of user behaviors was presented for host-based intrusion detection systems with shell commands as audit data. The method constructs specific hidden Markov models(HMMs) to represent the be-havior profiles of users. The HMMs were trained by a sequence matching algorithm which was much simpler than the classical Baum-Welch algorithm. A decision rule based on the probabilities of short state sequences was adopted while the particularity of the states was taken into account. The results of computer simulation show the method presented can achieve high detection accuracy and practicability.

    Distributed scheduling for real-time convergecast in wireless sensor networks
    Xin KE,Li-min SUN,Zhi-mei WU
    2007, 28(4):  44-50.  doi:1000-436X(2007)04-0044-07
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    In some applications of wireless sensor networks, data packets generated by every node have to reach the sink node in short time. It resulted in a many-to-one communication paradigm referred to as convergecast. For the real-time of convergecast, a distributed scheduling algorithm was proposed. According to the algorithm, every node was scheduled by itself with information of one-hop range neighbor nodes. Some simulation and analysis prove that the algorithm can avoid data collisions, and the total number of timeslots needed to complete the convergecast once was around 1.6N to 1.8N, where N represents the number of nodes in the network.

    Model of fuzzy risk assessment of the information system
    Dong-mei ZHAO,Jian-feng MA,Yue-sheng WANG
    2007, 28(4):  51-56.  doi:1000-436X(2007)04-0051-06
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    A model of risk assessment was introduced to the estimation of the information system. The method, which combined AHP and fuzzy logical method, was applied to the risk assessment. AHP and fuzzy logical method were altered according to the actual condition of the risk assessment of information system. Applying fuzzy logical method, the im-portant degree of each factor was judged in the aspects of the probability, the impact severity and uncontrollability, not judged immediately. Finally, the risk value of each factor was calculated. By comparing the risk value of each factor, it is known that which risk can take measures to control. By introducing entropy, the proportion of each risk factor in the whole risk assessment system was calculated. Next the risk degree of the whole system was calculated. Then the risk level of the whole system can be determined. The study of the case shows that the model can be easily used to the risk assessment of the information system security. The results are in accord with the reality.

    HPPHM:new policy of store for multidimensional dataset of parallel I/O and research of retrieve performance
    Zhi-gang CHEN,Bi-qing ZENG
    2007, 28(4):  57-64.  doi:1000-436X(2007)04-0057-08
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    The policy of store and retrieve for large-scale multidimensional dataset was researched. The multidimensional dataset was allocated in the multi-disks among the distributed processing system by using the parallel I/O technology. A new multidimensional data cyclic declustering policy was proposed aiming to data retrieve based on scope by extending existing cyclic policy to multidimensional dataset from adapting to two-dimension, and by using theory analysis on the present method, a new heuristic multidimensional data retrieve policy named HPPHM was proposed. The experimental result has demonstrated the efficiency of new strategy not only in parallel degree but also in robust.

    Research on accurate ranging of UWB under indoor environments
    Shao-hua WU,Nai-tong ZHANG
    2007, 28(4):  65-71.  doi:1000-436X(2007)04-0065-07
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    The accurate ranging ability of ultra wideband (UWB) signal under IEEE 802.15.4a indoor channel model was studied. An improved time-of-arrival (TOA) estimation algorithm which utilizes region search and threshold comparison was proposed. By statistical analysis on certain characteristicals of the CM1 and CM2 channel profiles, the probability model of TOA estimation error was deduced. The thresholds of the proposed TOA estimation algorithm were then set by limiting the error probability to the lowest level. The mean absolute ranging errors under different SNR were simulated. Results show that high enough SNR should be guaranteed in order to obtain centimeter-level ranging precision under in-door environments, while extremely high SNRs would not help to improve the ranging precision any more but lead to a performance floor. The results have instructional significance on designing localization algorithms and transmission power control in practical ranging.

    Spatio-temporal error concealment scheme based on H.264/AVC
    Bin FENG,Guang-xi ZHU,Wen-yu LIU
    2007, 28(4):  72-79.  doi:1000-436X(2007)04-0072-08
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    In order to reduce the influence of transmission errors on the reconstructed image quality in decoder, a novel spatio-temporal error concealment scheme is proposed. A hypothesis was made that the corrupted macro blocks (MB) distributed randomly in the frame which is sufficiently realistic and extensively used in literature. Firstly a directional in-terpolation based spatial error concealment algorithm is used which introduces a method similar with the intra prediction in the encoder. Then an 8×8 block based enhanced temporal error concealment algorithm is proposed, which improves the ability to deal with the high motions areas. Finally, a switch strategy between spatial and temporal error concealment algo-rithm is addressed. It chooses an appropriate algorithm based on the adjacent MB coding modes. Experimental results dem-onstrated that the proposed scheme is prior to the algorithms in H.264/AVC both in objective and subjective quality.

    Minimum energy broadcasting algorithm in wireless sensor networks
    Yong TANG,Ming-tian ZHOU
    2007, 28(4):  80-86.  doi:1000-436X(2007)04-0080-07
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    In order to adjust the transmission power of nodes for minimizing total energy consumption in wireless sensor networks, a new distributed algorithm called ERBOP (enhanced relative neighborhood graph broadcast oriented protocol) was proposed which was an improvement upon RBOP (relative neighborhood graph broadcast oriented protocol) pre-sented by Cartigny et al. In ERBOP, a sub-graph of relative neighborhood graph, which was a sparse connected graph and contains minimum spanning tree, was locally constructed by eliminating long edges. Moreover, 1-dominating connected dominating set was constructed basing on the sub-graph, and only the dominating nodes participated in the broadcasting. The simulation results show that ERBOP conserves energy efficiently.

    Multiple symbol differential sphere decoding for unitary space-time modulation in continuous fading
    Ying LI,Xin WANG,Ji-bo WEI
    2007, 28(4):  87-94.  doi:1000-436X(2007)04-0087-08
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    Based on the assumption of continuous fading, a multiple symbol differential approximate automatic sphere decoding (MSDAASD) algorithm was developed by incorporating a recursive form of an approximate maxi-mum-likelihood (ML) metric into automatic sphere decoding. The proposed algorithm is suitable for arbitrary unitary constellations and eliminates the error floor caused by in multiple symbol differential sphere decoding (MSDSD) with quasi-static channel assumption. Compared with decision-feedback detection under the same assumption, MSDAASD achieves similar performance of ML detection with much lower complexity at moderate to high signal-to-noise ratios.

    Hurst weighted random early detection algorithm based on self-similar traffic input
    Li-ya HUANG,Suo-ping WANG
    2007, 28(4):  95-100.  doi:1000-436X(2007)04-0095-06
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    RED as proposed by Floyd was based on the traditional Poisson input model, could not satisfy self-similar na-ture of network traffic. With this in view, an attempt has been made by proposing a modified RED algorithm, the HWRED algorithm with self-similar input. Modified RED algorithm can tune RED parameters according to the Hurst parameter of input traffic. Simulated results show modified algorithm increases evidently stability of queue size, and de-creases packet loss ratio, queue delay and queue delay variability, finally improves link use percentage of network.

    Technical Report
    Study of the communication protocols of the intelligent network disk
    Yun-xia ZHOU,Yue-long ZHAO,Xi YANG
    2007, 28(4):  101-107.  doi:1000-436X(2007)04-0101-07
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    In order to resolve some problems, such as node malfunction, neck of the server in the network storage which run as server/disk mode. This paper put forward a storage concept called Intelligent Network Disk (IND). This paper in-troduced the logical architecture of the IND simply, more importantly, introduced the communication protocols of the IND based on blocks mode. Finally, Experiment proves the correctness of these protocols and the feasibility of IND.

    Watermarking text document based on statistic property of part of speech string
    Zu-xu DAI,Fan HONG,Guo-hua CUI,Min FU
    2007, 28(4):  108-113.  doi:1000-436X(2007)04-0108-08
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    An algorithm resolving nonlinear entropy equation with multivariable was described and proved firstly, then a new scheme where a text document is marked by accommodating probability distribution of certain Part of Speech strings to entropy constitutes the watermark was designed. Watermark function in the scheme values in a real number set domi-nated by computing precision, it is helpful to advances watermark capacity significantly.

    Overview
    Research on multi-dimension features of application layer multicast protocols
    Hai-ning LIAO,Xi-cheng LU
    2007, 28(4):  114-122.  doi:1000-436X(2007)04-0114-09
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    A set of application layer multicast protocols were described and classified based on some properties such as data forwarding policy, service model, optimization objectives, optimization techniques, and fault mechanism. Then some recommendations were provided about the design of ALM protocols. Finally some important directions for future re-search are discussed.

    Academic communication
    From prime codes to concatenated prime codes
    Qing-ge LIU,Ding-rong SHAO,Shu-jian LI
    2007, 28(4):  123-127.  doi:1000-436X(2007)04-0123-05
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    The relationship between prime codes and concatenated prime codes was analyzed. A new construct idea was concluded that concatenated prime codes were constructed by concatenation of the time-shift and frequency-shift versions of prime code sequences, and the concrete rules were presented. This thought will lead to further extension versions of prime codes over GF(Pn) with n>2. Furthermore, according to the time-shift and frequency-shift equivalence property of prime codes, a rule was found for concatenated prime codes, classification to get FH(frequency hopping) sequences groups with ideal Hamming correlation property, i.e. all the sequences in the same group have same time-shift step pair . This result was helpful to select FH sequences with ideal Hamming correlation characteristics. Finally, a simulation mod-ule was presented based on above conclusions.

    Joint channel estimation and ICI cancellation algorithm for pilot-assisted OFDM systems
    Qi JIANG,Chun-ming ZHAO,Peng JIA
    2007, 28(4):  128-135.  doi:1000-436X(2007)04-0128-08
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    The inter-carrier interference caused by double-selective channels in OFDM systems was analyzed. An OFDM channel estimation method with new pilot structure was also proposed, based on which the channel estimation in time domain and the ICI cancellation could be done within one OFDM symbol. The simulation results show that the proposed joint channel estimation and ICI cancellation algorithm can provide more accurate channel information, and improve system performance apparently.

    Diversity and multiplexing based on GMD algorithm
    Zhong-tang HE,Ju-mei AI,Luo-quan HU,Li-jun ZHANG
    2007, 28(4):  136-140.  doi:1000-436X(2007)04-0136-05
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    The GMD-VBLAST algorithm to treat with the MIMO systems was analyzed, where the channel information at both transmitter and receiver were known. It decomposed a MIMO channel into multiple identical parallel subchannels and provided more convenient for coding/decoding schemes, which was different from conventional SVD method. The diversity and multiplexing tradeoff curve was achieved in the case of high SNR and compared with the optimal tradeoff curve and others VBLAST schemes'. The results showed that this scheme is suboptimal to the optimal but superior to the other VBLAST schemes'.

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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