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Table of Content

    20 April 2006 Volume 33 Issue 2
      
    Original Articles

    The method for improving the range resolution in a passive location system

    ZHAO Hong-li;WU Tie-ping;BAO Zheng
    J4. 2006, 33(2):  165-168. 
    Abstract ( 1555 )   PDF (175KB) ( 964 )   Save
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    In the passive location system based on the FM broadcast, signals are uncooperative and non-stationary. With the generation theory of the signals taken into account, it is pointed out that the range resolution of the modulated signals declines because of the intermission of modulating signals. The method for confirming intermission based on the derivative of the signals is presented. The method for setting the intermission to zeros is analyzed to improve the range resolution. The results of the procession of the field data validate the proposed method to improve the range resolution with low computation and easy real-time procession.

    A novel autofocus algorithm based on maximum total variation criteria for SAR image

    MA Lun;LIAO Gui-sheng
    J4. 2006, 33(2):  169-172. 
    Abstract ( 1770 )   PDF (172KB) ( 1103 )   Save
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    A novel autofocus algorithm for synthetic aperture radar (SAR) images is presented based on total variation. The method, which starts with a complex phase-degraded SAR image, after a phase errors model is introduced into the range-compressed phase-history domain, carries out phase errors correction by changing the focus until the total variation of the azimuth profile is maximized. Compared with the minimum entropy autofocus algorithm, this autofocus algorithm is of less computational complexity and easy to implement. The simulation and processing results of the measured data show the validity of the proposed method.

    A weighted feature reduction method for the power spectrum of radar HRRP

    DU Lan;LIU Hong-wei;BAO Zheng;ZHANG Jun-ying
    J4. 2006, 33(2):  173-177. 
    Abstract ( 1862 )   PDF (216KB) ( 958 )   Save
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    This paper proposes a weighted feature reduction method based on Fisher’ discriminant ratio(FDR) for a time-shift invariant feature, power spectrum, in radar automatic target recognition using the high-resolution range profile(HRRP). The proposed weighted feature reduction method uses the FDR vector of the target power spectrum to iteratively search for an optimal weight vector, and reduce feature dimensionality according to the optimal weight vector. Compared with using the raw power spectrum feature and some existing feature reduction methods based on Fisher’s linear discriminant, the proposed weighted feature reduction method can not only reduce the feature dimensionality, but also improve the recognition performance with low computation complexity. In the recognition experiments based on measured data, the proposed method is robust to different test data and achieves good recognition results.

    Multi-target sidelobe suppression of color TV signals

    SUN Xiao-wen;WU Shun-jun
    J4. 2006, 33(2):  178-181. 
    Abstract ( 1460 )   PDF (169KB) ( 905 )   Save
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    To eliminate the range sidelobe and improve the multi-target range resolution of passive radar using TVsignals, the mismatched filter is proposed. Based on minimizing the ISL (Integrated Sidelobe Level), the PSL (Peak Sidelobe Level) is approached by the iteration process. Simulation results indicate that not only the range resolution is improved but also the correlation sidelobes are suppressed after mismatched filtration. So the multi-target detectability of passive radar using TV signals is enhanced.

    Embedded coding of medical images with regions of interest based on the three-dimensional zerotree

    MA Jing;WU Cheng-ke;CHEN Dong;ZHOU You-xi
    J4. 2006, 33(2):  182-185. 
    Abstract ( 1860 )   PDF (211KB) ( 838 )   Save
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    In order to satisfy the need of diagnoses, based on the characteristic of medical images that a sequence of frames are formed in one body inspection, a new strategy for medical images compression is proposed. The three-dimension wavelet is adopted and the planar zerotree is extended to the three-dimensional zerotree. By making use of the three-dimensional zerotree structure, a simple method for ROI mask generation is put forward. Medical images are compressed by three-dimensional embedded coding with the compression of regions of interest. Simulation results have shown that it can efficiently improve the compression ratio without affecting the diagnoses.

    A novel SET process with Indium quantum islands

    GUO Rong-hui(1);ZHAO Zheng-ping(1);HAO Yue(1);LIU Yu-gui(2); WU Yi-bin(2);Lü Miao(2)
    J4. 2006, 33(2):  186-189. 
    Abstract ( 1655 )   PDF (162KB) ( 944 )   Save
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    A new Single-electron Transistor with Indium Quantum Dots is presented. By virtue of the high resolution of the EBL and the accurately controllable growth of the MBE, Indium Quantum Dots are grown in the nanometer gap of the electrodes. With these Indium quantum dots as coulomb islands, a kind of SET with multi-islands is prepared, and the coulomb blockade effect is observed successfully.

    Projected natural gradient-based BSS algorithm with an unknown source number

    YE Ji-min(1);JIN Hai-hong(2);LOU Shun-tian(1);ZHANG Xian-da(1)
    J4. 2006, 33(2):  190-194. 
    Abstract ( 1701 )   PDF (233KB) ( 1112 )   Save
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    An analysis of the demixing matrixs dynamic changing in available blind source separation algorithms with an unknown number of sources is made and the conclusion that it is the redundant movement of demixing matrix in some equivalent class which cases the divergence is drawn. By canceling the redundant component of the natural gradient in an orthogonal projection approach, a new algorithm is developed, which overcomes the weak point of being unable to converge stably. Finally, simulation proves the capacity to perform the blind source separation with an unknown number of sources and the convergent stability of the new algorithm.

    Algorithm for automatic interpolation on the area of targets of interest

    SHI Ling-feng;GUO Bao-long
    J4. 2006, 33(2):  195-199. 
    Abstract ( 1647 )   PDF (208KB) ( 820 )   Save
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    It is necessary to amplify the area of the targets of interest in ground penetrating radar (GPR) while restraining background for artificial recognition. The paper presentes an algorithm for automatically interpolating in the area of targets of interest, which is based on twice statistics to automatically detect the transverse position of the targets of interest in GPR with the echoes of the target separated. The detected echoes of the target are preprocessed by the damond template. In turn, the method of statistics is used to determine the depth of the target. The area of targets of interest is enhanced by the correlation. Finally, the target is amplified by bilinear interpolation while the background is restrained. The different model is selected in a different application so that it not only realizes detection of targets of interest but also automatically enhances targets. Moreover, the algorithm is benefitial to locating and recognizing the buried targets. Te results of test by raw data show that the method is well adaptive and reliable.

    Data partitioning method based on picture content

    DU Jian-chao(1);WU Cheng-ke(1);YANG Ya-dong(1;2);XIAO Song(1)
    J4. 2006, 33(2):  200-204. 
    Abstract ( 1405 )   PDF (222KB) ( 956 )   Save
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    By analyzing the data partitioning tool in H.264, a novel data partitioning method based on the content of a picture is presented. It regroups video bitstreams into three separate sub-bitstreams according to importance: header information, data of Intra-macroblocks and part of Inter-macroblocks, data of the remainder of Inter-macroblocks. The two parts of Inter-macroblocks belonging to different sub-bitstreams are differentiated according to their impacts on the quality of the picture, and the number is decided by an optimal algorithm. Simulation results show that compared with the data partitioning tool in H. 264, the proposed method is more adaptive to the change of picture content and network conditions. Together with unequal error protection, it can improve the quality of video streaming to a great extent.
    Implementation of the total-field/scattered-field technique in the 2D ADI-FDTD
    ZHENG Kui-song;GE De-biao
    J4. 2006, 33(2):  205-210. 
    Abstract ( 1904 )   PDF (314KB) ( 993 )   Save
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    The total-field/scattered-field technique of the incident wave introduced into the total field region is dealt with for alternative direction implicit finite-difference time-domain method. By observing the grid points at the vicinity of connecting boundary for the two-dimensional TM wave, the incident wave field components should be added in each sub time step. Based on the computational formulations and the particular location of grid points at or near the connecting boundary, there are 14 cases to be considered, including 10 cases for electric field grid points. This technique inherits the characteristics for the introduction of the incident wave in the conventional FDTD method. The solution to linear system equations in this technique is also consistent with that in the ADI-FDTD method. It is demonstrated that the plane wave can be successfully introduced into the total field region by this technique, even when the time step size is 4 times longer than that of the Courant-Friedrich-Levy limit. Finally, the radar cross sections for a conducting column and an airfoil coated with a lossy medium is computed, showing the feasibility of the proposed technique.

    Study of LRCS of a multi-material coated complex object

    LI Liang-chao;WU Zhen-sen;GUO Li-xin
    J4. 2006, 33(2):  211-214. 
    Abstract ( 1612 )   PDF (173KB) ( 991 )   Save
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    The visualizing calculation method of LRCS of multi-material coated complex object is presented. The model containing material information is made by the color flag. The LRCS of the monostatic of an object is calculated by color flag imaging and that of the bistatic is calculated by additional bidirectional shading imaging. Then, the results of LRCS of the object coated with various materials and the paint rubbed off of the surface simulated with the Monte Carlo method are discussed. It is shown that the calculation method is visualized quickly and is practical.

    Study of the medium access control protocol for the multiple channels mobile Ad Hoc network

    SUN Xian-pu;ZHAO Li;TIAN Tian
    J4. 2006, 33(2):  215-217. 
    Abstract ( 1762 )   PDF (116KB) ( 851 )   Save
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    A novel medium access control protocol is presented for the mobile Ad Hoc with multiple channels. In this protocol, all nodes are clustered into several subnets and it is possible for a node to belong to more than one subnet. Different subnets are in different channels. In each subnet, a token is used to control the nodes transmited in turn, which can solve the problem of transmitting collisions. The quality of service (QoS) for real-time traffic is guaranteed by limiting the maximum number of nodes in each subnet. Besides these, the token dynamic transfer algorithm is proposed which can adaptively choose a path to transfer the token, so it has the ability to adapt the dynamic network topology and simplifies the process of token maintenance.

    A novel geographic routing applied in Ad Hoc networks

    HE Peng;LI Jian-dong;CHEN Yan-hui
    J4. 2006, 33(2):  218-222. 
    Abstract ( 1764 )   PDF (222KB) ( 1067 )   Save
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    A new geographic routing(GLFCFR) is proposed and the topology of the networks is planarized by the RNG. Every node stores only the location information of its immediate neighbor nodes and the location information of nodes on a local finite close face for forwarding the packets. With the increasing number of nodes in the network and increasing mobility rate, simulations show that GLFCFR achieves significantly better routing performance in routing protocol message cost and application packet delivery success rate.

    Memory digital baseband predistorter based on a polynomial

    WANG Yong(1);XIANG Xin(1;2);YI Ke-chu(1)
    J4. 2006, 33(2):  223-226. 
    Abstract ( 1446 )   PDF (210KB) ( 1263 )   Save
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    This paper proposes a digital predistorter which can compensate nonlinearity and memory effects of power amplifier in a communication system, which consists of an adaptive equalizer and a memoryless predistorter based on polyaminals. The memoryless predistorter is used for compensating nonlinearity, whose parameters are estimated by using a narrowband training sequence, while the equalizer is used for compensating memory effects, whose parameters are iteratively updated by means of an adaptive algorithm. Because nonlinearity and memory effects are pocessed seperately, the structure of the predistorter and its adaptive algorithms are much simpler than those of the conventional one. Simulation results show that the predistorter can correct the signal distortion effectively caused by nonlinearity and memory effects of power amplifiers.

    High-order-statistics based nonuniformity correction for infrared focal plane arrays

    XU Tian-hua;ZHAO Ji-zheng;ZHAO Yi-gong
    J4. 2006, 33(2):  227-230. 
    Abstract ( 2111 )   PDF (149KB) ( 961 )   Save
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    According to the property that for Gaussian signals only, all cumulant spectra of order greater than two are identically zero, a High-Order-Statistics based Nonuniformity Correction(HOS-NUC) approach is taken for the adaptive estimation of the gain and bias nonuniformity in infrared focal-plane array sensors from scene data. The proposed algorithm consists of two main parts: the first part involves a periodic statistical estimation of the model parameters using the moment and cumulant; the second part involves the estimated parameters in restoring the true image by a winner filter. The proposed method has been tested with video sequences of simulated infrared data, reducing the fixed pattern noise and reaching high correction levels.

    A large capacity packet switching fabric based on ring with scalability

    YANG Jun-gang(1;2);QIU Zhi-liang(1);LIU Zeng-ji(1);LI Dong-lu(1)
    J4. 2006, 33(2):  231-235. 
    Abstract ( 1346 )   PDF (233KB) ( 836 )   Save
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    A new type of switching fabric architecture—MR (Magic Ring) is proposed. The fabric inherits good performance of the traditional three stage indirect interconnection network, and possesses good scalability due to the adoption of the ring network at its second stage, which solves the problem that the present switching fabrics cannot obtain both of the two characters simultaneously. The good performance and good scalability of this fabric are shown by theoretical and simulative analyse.

    A novel multiple access protocol for a wireless local area network to effectively support a smart antenna

    LI Chang-le;LI Jian-dong;LI Bo;ZHANG Guang-hui; ZHOU Lei;HE Peng
    J4. 2006, 33(2):  236-240. 
    Abstract ( 2031 )   PDF (204KB) ( 981 )   Save
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    The use of a smart antenna in extending the coverage range and capacity of a wireless local area network(WLAN) dictates the employment of novel multiple access protocols, with which the access point(AP) provides access to remote users. In this paper, a novel and efficient multiple access protocol for the WLAN with a smart antenna has been proposed. Employing the hybrid superframe structure of the contention-free period and contention period, the protocol distinguishes between the users residing in or out of the broadcasting coverage range of the AP. The performance of the protocol is compared with other different three protocols and the effectiveness and robustness of the novel protocol have been proved by simulation. Results show that the protocol can extend the coverage range of the WLAN effectively and support the data exchange between the AP and the stations residing out of its broadcast range.

    A study of the performance of the enhanced RIEMS in mobile Ad Hoc Networks

    WANG Xuan;LI Jian-dong;LI Feng
    J4. 2006, 33(2):  241-246. 
    Abstract ( 1971 )   PDF (229KB) ( 980 )   Save
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    An Enhanced RIEMS rate-adaptive MAC protocol(RIEMS+) is proposed, which improves the NAV undate mechanism of the original RIEMS protocol. In the new mechanism, neighbors of transmission nodes update their NAV values depending not only on the information in the MAC header but also on the information in the PHY header. RIEMS+ can decrease the transmission failure probability and increase the channel utility factor, because it overcomes the drawback that nodes may have different cognitions on channel status, which arises from the differences in propagation ranges of frames with varying transmission rates. Simulation results prove that the proposed method can improve the ETE throughput and the average packet transmission delay obviously.

    Maximum likelihood classification for MPSK signals in the wavelet domain

    HU Jian-wei;YANG Shao-quan
    J4. 2006, 33(2):  247-250. 
    Abstract ( 1849 )   PDF (159KB) ( 965 )   Save
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    With the problem of identifying modulation types in electronic warfare in mind, a novel maximum likelihood (ML) modulation classification algorithm is presented in the wavelet transform domain. The relationship between the Haar wavelet transform coefficients of the MPSK signals and its phase parameters is discussed, with the ML classification function obtained by modeling the wavelet coefficients as a generalized Gaussian distribution. Less priori parameters knowledge is needed in the new algorithm. Numerical experiments are also used to illustrate the effectiveness and robustness of the proposed method.

    Fast data association algorithm based on maximum entropy fuzzy clustering

    LI Liang-qun;JI Hong-bing
    J4. 2006, 33(2):  251-256. 
    Abstract ( 1661 )   PDF (263KB) ( 929 )   Save
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    A novel fast data association method is proposed, which reduces the computational load of the association probability in filtering. Firstly, the candidate measurements of each target are clustered with the aid of the modified maximum entropy fuzzy clustering. Then the joint association probability is reconstructed by utilizing the fuzzy membership degree of the target and measurement. At the same time, in order to avoid the track coalescence, the scaling factor is introduced to modify the joint association probability. Moreover, the characteristic of the discrimination factor is analyzed and the influence of the clutter density on it is also considered, which enables the algorithm to eliminate those invalidate measurements and reduce the computational load. Finally, simulation results show that the fast data association algorithm is effective, and that the performance of tracking is better than that of the existing ones.

    A new motion estimation algorithm based on hardware implementation and its VLSI design

    SONG Rui;ZHAO Bo;XIAO Song
    J4. 2006, 33(2):  257-261. 
    Abstract ( 1635 )   PDF (218KB) ( 848 )   Save
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    A new pyramid motion estimation algorithm and its VLSI architecture are proposed based on the demand for hardware implementation of a video encoder. The computational load is reduced by the method of a pyramidal sample in searching positions. Redundant computation of 8×8 or 4×4 blocks is removed after macro blocks for the Sum of Absolute Difference(SAD) of sub-block are calculated directly in the last layer of integral search. During hardware implementation processing, data stream access mode is revised, and parallel process efficiency is impoved as well. After positions sampling, each layer has a similar architecture, and hareware resource is saved significantly by use of the common module. Simulation results on MPEG-4 SP show that although the new pyramid algorithm is 0.02dB lower than full search in PSNR, the process load and hardware resource occupancy are 7% and 25%, respectively, that of full search, which will meet the requirements for real time applications.

    A deadlock prevention policy for FMS using elementary siphons

    LI Zhi-wu;MA Xiong
    J4. 2006, 33(2):  262-267. 
    Abstract ( 1721 )   PDF (310KB) ( 885 )   Save
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    We develop an effective control policy to prevent deadlocks from occurring in a class of Petri nets, ES<sup>3</sup>PR, where deadlocks are related to unmarked siphons. Strict minimal siphons are divided into elementary and dependent ones. For each elementary siphon, a monitor is added to ensure that it is sufficiently marked without gnerating emptiable control-induced siphons. The controllability of a dependent siphon is guaranteed by changing the control depth variables of its related elementary siphons, which leads to a liveness-enforcing supervisor for a plant model. Furthermore, by checking the redundancy of the additional monitors, some control-redundant monitors can be removed, which leads to a more permissive and structurally simple net supervisor.

    The research on MOCVD temperature control based on the fuzzy predictive mechanism

    GUO Run-qiu;ZHAO Heng;DU Kai
    J4. 2006, 33(2):  268-272. 
    Abstract ( 1332 )   PDF (185KB) ( 913 )   Save
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    This paper presents a new fuzzy predictive control method for the MOCVD device control system set to handle the non-linearity, time variability and large delay of plant controls. The designed controller consists of a fuzzy part and a predictor. The dynamics of the prediction term is adaptive to the systems time delay. Simulation results illustrate that this method is well adaptive to the alteration and improves the static precise and dynamic performance of the system, compared with its conventional counterpart. In addition, the basic error can reach 1℃‰ referred to input range.

    Optimal recursiveness for generalized discrete stochastic linear systems

    ZHANG Zhuo-kui;CHEN Hui-chan
    J4. 2006, 33(2):  273-277. 
    Abstract ( 1635 )   PDF (213KB) ( 832 )   Save
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    The optimal recursive equation for the generalized discrete linear system is discussed. A singular values standard form for generalized discrete stochastic linear systems is given by singular value decomposition of a matrix. In two cases, the generalized discrete stochastic linear system is decomposed into two subsystems based on the standard form. The optimal recursive equations for this system are obtained by state estimation of subsystems.

    A new blind pixels correction algorithm for IRFPA based on moving scenes

    WANG Bing-jian;LIU Shang-qian;LI Qing;LAI Rui
    J4. 2006, 33(2):  278-280. 
    Abstract ( 1526 )   PDF (132KB) ( 808 )   Save
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    This paper presents a new blind pixels approximation algorithm based on the scene moving analysis for the infrared focal plane array(IRFPA). It is known that there exists strong relativity between neighboring images in image sequences. By moving scence analysis, moving parameters can be calculated from image sequences. Then the pixels in the previous frame image can be found which correspond to blind pixels in the current frame image. And these pixels are used to approximate blind pixels in the current frame. This algorithm can make objects in the aproximated image maintain its edge completely. Theoretical analysis and experimental results show its effectiveness.

    Two-dimensional ADI multi-domain pseudospectral time domain algorithm

    SHI Yan;LI Long;LIANG Chang-hong
    J4. 2006, 33(2):  281-286. 
    Abstract ( 1320 )   PDF (245KB) ( 847 )   Save
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    A new algorithm which combines the ADI technique and the multi-domain pseudospectral time domain algorithm is presented to solve the stability problem restricted by the finite-difference time-domain (FDTD) and traditional multi-domain pseudospectral time domain (PSTD). The compact matrix is used to clearly describe the 2-D ADI multi-domain pseudospectral time domain (ADI-MPSTD). This algorithm not only maintains accuracy and flexibility of PSTD for an accurate treatment of arbitrarily curved objects, but also improves stability and efficiency. Compared with numerical results calculated by some conventional algorithm, the results of ADI-MPSTD fully demonstrate higher accuracy and good stability.

    An application of random simulations in multiple attribute decision making with incomplete information

    SUN De-hua(1);SHI Jia-rong(2);LIU San-yang(1)
    J4. 2006, 33(2):  287-291. 
    Abstract ( 1586 )   PDF (201KB) ( 869 )   Save
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    This paper presents a type of multiple attribute decision making problem on the condition of the incomplete information and the random simulations method for solving the problem. Numerical experiment shows that this method possesses stability and reliability and has the advantages of low complexity of computation and easy realization over the method available.
    Novel method for priorities in the interval numbers complementary judgment matrix
    ZHOU Hong-an(1;2);LIU San-yang(1)
    J4. 2006, 33(2):  292-294. 
    Abstract ( 1667 )   PDF (132KB) ( 815 )   Save
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    We focus on studying the multi-objective decision making problems, in which the preference information provided by the decision maker takes the form of an interval numbers complementary judgment matrix. Firstly, the concept of interval numbers consistency complementary judgment matrix and its judgment theorem are given. Secondly, a goal programming model is established and the weight vector of interval numbers complementary judgment matrix is obtained by solving the model. Finally, the alternatives are ranked by using an existing priority formula of possibility. A goal programming method for interval numbers complementary judgment matrix is presented and characterized by simple operation and it is easy to implement on computer.

    The medialness based on wavelet scale space

    FENG Xiang-chu;YANG Yong-dong;WANG Yi-long
    J4. 2006, 33(2):  295-298. 
    Abstract ( 1442 )   PDF (166KB) ( 884 )   Save
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    A new medialness is derived, based on the traditional medialness and wavelet scale space. Compared with the available algorithms, this new method can not only reduce computation but also enhance the edges of the images, which is beneficial to image further processing.

    Nonlinear programming method for time optimal switching control

    LI Bing-jie(1;2);LIU San-yang(1);YIN Zhong-hai(1;2)
    J4. 2006, 33(2):  299-303. 
    Abstract ( 1520 )   PDF (199KB) ( 844 )   Save
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    A nonlinear programming method for time optimal switching control with a single control input is proposed. The unknown arc time is partitioned off the unknown durations of the segmental times in different switching control problems, and the nonlinear programming model equivalent to the optimal control is constituted with the time segments serving as variables. The Runge-Kutta numerical formulations based on average partitioning of each time segment are formed, which do not increase the number of the unknown variables but constitute a nonlinear programming without the derivative of all the functions. The convergence of the method is derived from the convergence of the Runge-Kutta formulations and the first-order necessary optimality condition. Finally, the proposed method is applied to some examples to demonstrate the effectiveness of the method.

    AMS based reconstruction algorithm with the two-dimentional threshold for IP traceback

    YANG Xue-qin;PEI Chang-xing;ZHU Chang-hua;CHEN Nan;YI Yun-hui
    J4. 2006, 33(2):  304-306. 
    Abstract ( 1486 )   PDF (122KB) ( 811 )   Save
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    We present a new reconstruction algorithm based on the Advanced Marking Scheme(AMS). It works with a two-dimentional threshold mf,d, decides if a node is on the attack path by judging the situation of the edge of the packet and the Hash value match, then consequently reduces the time of reconstruction and overhead and improves accuracy and stability. Compared with the conventional methods, two-dimentional threshold reconstruction algorithm impves the performance of the IP traceback technique obviously.

    Cross-power spectrum method for registration in a log-polar coordinate system

    LIU Han-zhou;FENG Zong-zhe;GUO Bao-long
    J4. 2006, 33(2):  307-310. 
    Abstract ( 1760 )   PDF (181KB) ( 1447 )   Save
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    The traditional FFT-based algorithm is found to be less stable numerically to register images with translations, scalings and rotations. This paper proposes a new FFT-based approach to estimate these affine transforms. We have proved that the cross-power spectrum method is poor in registering basically monotone-smooth signals with translations. These signals often exist in Fourier-magnitude representation data of an image in a log-polar coordinate system for each polar angle. By truncating the data at low coefficients in the logarithm coordinate system, the local maximum effect of undersirable signals can be reduced. Experimental results show that the proposed method outperforms the traditional FFT-Based image registration algorithm.

    An efficient ID-based threshold signature

    LIU Ying;HU Yu-pu;WANG Fei;LU Xiao-jun
    J4. 2006, 33(2):  311-315. 
    Abstract ( 1695 )   PDF (196KB) ( 990 )   Save
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    A new ID-based threshold signature scheme is proposed from bilinear pairings, based on our improved ID-based signautre scheme. In our ID-based threshold signature scheme, the dishonest Private Key Generator (PKG) can not impersonate any user at any time. We show that it is secure against existential forgeable on adaptively chosen message and ID attack under the random oracle. Compared with the previous scheme, it is shorter and more efficient with the same security.

    A new timing synchronization method for OFDM systems under the multi-path channels

    WANG Yuan-li;GE Jian-hua;WANG Yong;NIE Yuan-fei
    J4. 2006, 33(2):  316-321. 
    Abstract ( 2402 )   PDF (254KB) ( 1064 )   Save
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    In wireless environment, the accuracy of timing synchronization in an OFDM system would be affected by multi-path. For the sake of solving this problem, a new method and its improved one based on the cyclic prefix are proposed in this paper, which uses the separate block of the correlation between the cyclic prefix and its duplicated part which is different from the continuous correlation or point correlation in the existing methods. The proposed methods could obtain the time delay and the length of the cyclic prefix, with their deviation and simulation given. It is shown that the proposed methods have higher precision and lower complexity compared with the existing methods. Also, they could obtain the time delay of the channel and the length of the cyclic prefix.

    The linear complexity of new Ding-generalized cyclotomic sequences of order 2<sup>k</sup> of length pq

    LI Sheng-qiang;WANG Xiao-fen;XIAO Guo-zhen
    J4. 2006, 33(2):  322-326. 
    Abstract ( 1545 )   PDF (223KB) ( 797 )   Save
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    Linear complexity is the most important index for measuring the randomness properties of sequences. Based on the Ding-generalized cyclotomy, new generalized cyclotomic sequences of order 2<sup>k</sup> of length pq are constructed by finding out a special characteristic set. The linear complexity of the sequences is determined. The minimum of the linear complexity is (n-1)/2 and the maximum of the linear complexity is n. And the sequences are balanced.

    Study of cell images lossless compression based on the EZW algorithm

    SUN Wan-rong(1;2);ZHONG Zheng-hui(2);YU Bian-zhang(1);ZHANG Xiao-jing(2)
    J4. 2006, 33(2):  327-332. 
    Abstract ( 1892 )   PDF (219KB) ( 958 )   Save
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    Several integer wavelet transforms are compared on marrow cell image energy distribution and their percentage of zero coefficients in every subband for higher performance of marrow cell image lossless compression. CDF(4,2) are found to be particularly good. A new method for threshold quantization is applied to EZW coding. Experimental results show that this approach can increase the number of zerotrees and improve the performance of compression.

    A bandwidth allocation scheme and QoS analysis for broadband wireless networks

    GUO Juan(1);LI Ming-yuan(2)
    J4. 2006, 33(2):  333-336. 
    Abstract ( 1742 )   PDF (172KB) ( 924 )   Save
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    A bandwidth allocation scheme for the broadband wireless network is presented. For the realtime services such as audio and video services, the required channels are allocated in every frame; for the handoff realtime calls, guard channels are reserved in every frame. Nonrealtime services, such as data services, use the remaining channels in each frame. In a multimedia wireless network based on TDMA/TDD, the performance of this scheme is analyzed and evaluated. Results show that the scheme can satisfy constrains on the blocking probability of the realtime new calls, the forced termination probability of realtime handoff calls, and the packet delay of data services.