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    20 October 2005 Volume 32 Issue 5
      
    Original Articles

    An HRRP recognition method based on zero phase representation

    CHEN Bo;LIU Hong-wei;BAO Zheng
    J4. 2005, 32(5):  657-662. 
    Abstract ( 1762 )   PDF (234KB) ( 1091 )   Save
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    Since the target High-Range-Resolution-Profile contains very important target discrimination structure information, it is regarded as a promising radar automatic target recognition(RATR) signature. It is known that the HRRP range alignment is a crucial problem in HRRP based RATR, which generally includes two kines of approaches, namely, absolute range alignment method and relative range alignment method. Based on a radar range profile absolute alignment method, Zero Phase Representation, an HRRP recognition approach based on the subband signal is proposed, which is robust to the range alignment error. Experimental results show the proposed method can lead to a good recognition performance with the advantage of low computation complexity over the maximum correlation coefficient (MCC) classifier, and outperforms the classifier based power spectrum feature.

    A robust self-calibration algorithm based on iterative weight

    LIU Shi-gang;WU Cheng-ke;TANG Li;JIA Jing
    J4. 2005, 32(5):  663-666. 
    Abstract ( 1433 )   PDF (168KB) ( 827 )   Save
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    The paper presents a robust self-calibration algorithm based on iterative weight, which can efficiently discard the outliers. The weight of each point is determined based on the re-projective errors and the metric reconstruction is obtained based on the weight. After serveral iterations, the weights of the outliers approaches zero, with the projective reconstruction obtained with good accuracy. The camera intrinsic parameters are obtained after projective reconstruction. The algorithm can overcome the drawbacks of both the least-squares method and the RANSAC method. The theory and experiments with both simulation and real data demonstrate that the self-calibration algorithm is very efficient and robust.

    The use of the radial velocity to improve the performance of target tracking

    ZHANG Huai-gen;ZHANG Lin-rang;WU Shun-jun
    J4. 2005, 32(5):  667-670. 
    Abstract ( 2160 )   PDF (150KB) ( 1091 )   Save
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    Based on three-dimensional space, a new method for the nonlinear Kalman filter using the radial velocity is presented. The polar coordinates which where observed are converted to the rectilinear coordinates first. Then the nonlinear function of the radial velocity is expanded in a Taylor series around the predicted state estimate. So the standard Kalman filter can be used. Simulation results show that the evaluated error is decreased and the convergent velocity is accelerated when the radial velocity is introduced.

    Detection of side information for peak-to -average power ratio reduction of the OFDM signal using the suboptimal PTS method

    YANG Gang;JIANG Ri-miao;LI Yu-shan
    J4. 2005, 32(5):  671-674. 
    Abstract ( 1356 )   PDF (176KB) ( 866 )   Save
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    For every sub-carrier of the OFDM system modulated by QPSK or 4QAM symbols, two simple side information detection schemes for peak-to-average power ratio reduction of the OFDM signal using the suboptimal Partial Transmit Sequence method are proposed. By using the properties of QPSK data and marking the side information into the signal with phase rotation of QPSK data at the transmitter, the two schemes can detect the side information by simple operations (modulo arithmetic, subtract operation and compare operation) at the receiver. The proposed schemes can lead to significant reduction in computational complexity. Simulation results demonstrate the good performance of the proposed schemes, especially for the scheme 2 with error correction.

    A TCP enhanced scheme for broadband satellite networks

    WANG Kai-dong1;2;YI Ke-chu2;TIAN Bin2
    J4. 2005, 32(5):  675-680. 
    Abstract ( 1790 )   PDF (306KB) ( 1023 )   Save
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    When a TCP stream goes through a broadband satellite network with a large bandwidth-delay product, the congestion window of the TCP stream is usually big so that there are lots of strongly bursty traffic on the network, which makes the intermediate nodes in the network so easily into the congested state, thus having a negative impact on overall network efficiency. This paper analyses the case and proposes an improved scheme: TCP-regular, so that TCP packets are sent not in burst but in regular over an entire round-trip time. Simulation shows that TCP-regular effectively enhances the overall efficiency and robustness of the broadband satellite networks.

    An improvement of the ant colony algorithm for solving TSP problems

    ZHANG Jun-ying1;2;AO Lei1;JIA Jiang-tao1;GAO Lin1
    J4. 2005, 32(5):  681-685. 
    Abstract ( 1597 )   PDF (179KB) ( 1151 )   Save
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    As a novel bionic evolutionary algorithm, the ant colony algorithm has been widely applicable to many complicated combinatorial optimization problems. However, the standard any colony algorithm often gets stock into premature stagnation after the iteration process. In this paper, through an analysis of the main reason of the premature stagnation phenomenon in the standard ant colony algorithm, we present a modified version of the algorithm by introducing the local pheromone, modifying the pheromones of the best route and the worst route, as well as making the parameter of the algorithm to be variant during its iteration and searching with a local optimization strategy. Experimental results for solving TSP problems with both the standard ant colony algorithm and the proposed one show that averagely speaking, the proposed method is much better in both the quality of the solution and the speed of convergence compared with the standard any colony algorithm.

    Control scheme for multimedia synchronization over IP

    XU Yan1;2;CHANG Yi-lin1;JIA Jie1;LUO Zhong3
    J4. 2005, 32(5):  686-690. 
    Abstract ( 1936 )   PDF (175KB) ( 822 )   Save
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    Based on the analysis of the Resource Reservation Protocol(RSVP), Real time Transport Protocol(RTP), Real time Control Protocol(RTCP) and Real Time Streaming Protocol(RTSP), a multimedia synchronization control scheme over IP is proposed. It combines RTSP with RSVP to set up and manage reserved-bandwidth streaming sessions that are carried by RTP. After mapping users’ synchronization requirements into the network QoS(FLOWSPEC in RSVP), RSVP can reserve resource to guarantee intra-stream synchronization. RTCP control packets can be used to determine the network congestion state and to control the quality of session., Inter-stream synchronization can be achieved by adjusting the process of playout. With this scheme, intra-stream and inter-stream synchronization can be guaranteed in real-time multimedia applications over IP.

    A logical topology design in the optical burst switching network

    ZHANG Shi;QIN Hao;LIU Zeng-ji
    J4. 2005, 32(5):  691-696. 
    Abstract ( 1732 )   PDF (252KB) ( 888 )   Save
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    The one-way reservation protocol used in Optical Burst Switching(OBS) makes current routing and wavelength assignment(RWA) algorithms suffer from high burst blocking probability. In this paper, the logical topology of the OBS network is introduced to guide the lightpath establishment of the bursts, and an RWA algorithm based on virtual topology is given. The logical topology design problem is formulated as an integer linear programming(ILP), whose optimization objective is to maximize the carried load of the logical topology. Numerical results obtained for NSFNET show that our algorithm can not only balance the carried load on fiber links, but also reduce burst blocking probability. Moreover, it can reduce the number of used wavelength conversions greatly when the traffic load is not very high.

    A method for making ISAR echoes coherent in a non-coherent dechirp system

    CAI Wei-gang;BAO Zheng;XING Meng-dao
    J4. 2005, 32(5):  697-701. 
    Abstract ( 1860 )   PDF (232KB) ( 1025 )   Save
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    For the sampling bandwidth to be reduced, ISAR echoes are often dechirped at the receiver with the reference ranges varying according to the target position each pulse. Thus, the echoes are non-coherent after dechirping. A remedial method is presented by the following two steps: Firstly we control the dechirp reference ranges approximately by hardware; secondly we compensate the Doppler phase error caused by the reference signals delay error precisely through the comparison between reference signals and benchmark signal. As a result, a group of sampled target echoes can be made coherent without phase autofocusing operation. This method will improve the ISAR imaging speed greatly and be of special value in ISAR imaging when the signal to noise ratio becomes low.

    An approach of automatically generating hierarchical statecharts

    CHU Hua;CHEN Ping
    J4. 2005, 32(5):  702-705. 
    Abstract ( 1610 )   PDF (193KB) ( 1204 )   Save
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    Now many reverse engineering tools have represented dynamic behaviors of systems using statecharts. But it is very difficult to show them in a flat statechart. An approach of automatically generating hierarchical statecharts based on syntax analysis is proposed in this paper. The main idea of this approach is to cluster XOR states of a flat statechart. Using hierarchical statechats, we can improve the abstract level of statecharts and reduce the amount of states and transitions. Finally, systematic experiment is conducted in the paper in order to verify the correctness and validity of this approach.

    The study of an efficient sub-region iterative current-based method

    WANG Li-na;ZHAI Hui-qing;LIANG Chang-hong
    J4. 2005, 32(5):  706-710. 
    Abstract ( 1804 )   PDF (212KB) ( 937 )   Save
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    It has been shown that the MoM-PO hybrid method is not effective to dealing with the complex coupling effects in a large PO region. In view of this, the multi-regions are divided on the whole object firstly in the paper. Then, the electric-field integral equation(EFIE) and the magnetic-field integral equation (MFIE) are used to different sub-regions. Furthermore, an efficient sub-region iterative current-based method is introduced to solve the different region's current. Therefore, the complex couplings in larger regions are effectively analyzed according to the simple coupling effects among many smaller regions. Finally, two typical numerical examples are given to illustrate the efficiency of the paper's method.

    The convergence analysis of serially concatenated space-time codes

    LI Ying;GUO Xu-dong;WANG Xin-mei
    J4. 2005, 32(5):  711-715. 
    Abstract ( 1446 )   PDF (243KB) ( 835 )   Save
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    The EXIT Chart analysis for the binary concatenations is generalized to the serially concatenated space-time code(SCSTC) with multiple antennas. The convergence characteristic of the iterative decoding for SCSTC is determined via the analysis of the transfer characteristic of the bitwise mutual information of each constituent code. By analyzing the effect of different constituent codes on the convergence of SCSTC, we design a class of space-time code to improve the convergence of SCSTC. Compared with the traditional SCSTC, the new designed SCSTC can converge earlier and has an approximate coding gain of 0.8 dB.

    Subspace-based techniques for certain blind equalization

    MA Chun-hua;FENG Da-zheng
    J4. 2005, 32(5):  716-719. 
    Abstract ( 1472 )   PDF (192KB) ( 907 )   Save
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    Based on the subspace method, this paper presents a new technique for the blind equalization of multiple-input multiple-output linear systems whose channel impulse has finite support of the same length. By utilizing the theory about the rational subspaces and the minimal polynomial basis and then estimating the instantaneous correlation matrix, this technique can identify the channel coefficients and accomplish the blind equalization. Computer simulations can prove its effectiveness.

    Novel HARQ system based on sub-packet transmission

    ZHOU Qin-ying1;GE Hui2;WANG Xin-mei1;XU Wei-dong1
    J4. 2005, 32(5):  720-723. 
    Abstract ( 1764 )   PDF (187KB) ( 884 )   Save
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    A new hybrid automatic repeat request(HARQ) system is constructed by combining the sub-packet scheme with the averaged diversity combining technique. The optimal number of sub-packets of the new HARQ system is evaluated according to the characteristics that the signal to noise ratio is increased by a factor equal to the retransmission times in the Code Division Multiple Access(CDMA) system. In the new HARQ system the diversity combination of data packet and its copies in the retransmissions is converted to the diversity combination of the same sub-packets in the one data packet and no retransmission is needed, which brings the advantages of real time communication, omitting the complicated retransmission control and a mass of memory. Also the method of making combination before being despread avoids the inefficient combination due to the spread and restriction of memory in type -Ⅰ HARQ. In addition, the method of adding tail bits to each sub-packet improves the performance of the new HARQ. Numerical and simulation results show the new HARQ system has a much higher throughput than the type-Ⅰ HARQ and the evaluated optimal number of sub-packets is in agreement with the simulated results.

    Research on short sequence power spectrum estimates based on the Burg algorithm

    LUO Feng;DUAN Pei-pei;WU Shun-jun
    J4. 2005, 32(5):  724-728. 
    Abstract ( 1661 )   PDF (185KB) ( 1163 )   Save
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    In practice, only finite data can be obtained so it is very necessary to use an efficient estimation algorithm to get exact characters of the short data sequence. This paper presnts an improved Burg algorithm and analyses the experimental data. The algorithm improves the order estimation by using a convergent factor. Otherwise, the first reflecting coefficient is not directly obtained by the Burg algorithm but by solving the coefficients of the second order PEF coefficients according to making the total output power minimum. After obtaining the coefficients of the second order PEF, the first order and the other higher order coefficients of PEF can be calculated. Results indicate that the peak shift of spectrum is reduced and the resolution is improved.

    The molecular dynamics simulation of an atomic-scale memory based on the double steady-states

    JIA Jian-yuan;FAN Kang-qi;WANG Hong-xi;ZHU Ying-min
    J4. 2005, 32(5):  729-732. 
    Abstract ( 1370 )   PDF (195KB) ( 854 )   Save
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    Molecular dynamics simulations were performed to study the atomic behaves in the surface and deeper layers of body-centered cubic(bcc) crystal, with the Morse potential denoting the interactions among the atoms. Results indicate that the bcc crystal remains stable before and after the central atom is manipulated. That is, the bcc cyrstal possesses the property of double steady states, which is capable of representing ‘0’ and ‘1’. At the same time, many-atomed combination of double steady states was investigated by the molecular dynamics simulations method. In the case of the many-atomed combination of double steady states, the bcc crystal still remains stable when manipulating other central atoms. Based on the facts given above, a novel way to achieve atomic-scale memory is put forward, which has the advantages of higher availability, better repetitiousness and stability.

    Adaptive interference rejection technique based on wavelet packet transform in DSSS systems

    WANG Xi-xi1;ZENG Xing-wen2
    J4. 2005, 32(5):  733-736. 
    Abstract ( 1720 )   PDF (162KB) ( 979 )   Save
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    The decomposition of the received signal realized by discrete wavelet packet transformation in DSSS systems is studied. The performance evaluation of the excision techniques via DWT is presented. The optimal adaptive NBI rejection arithmetic is also proposed. Using the adaptive filter instead of sub-band excision, which suppresses NBI efficiently and impoves loss of the avail signal. Analyzed and simulated results show that the interference suppression method of adaptive wavelet packet decomposition based on the TSA algorithm will obtain better performance than that of conventional sub-band elimination. Additionally, the orientation speed of the adaptive algorithm can be increased.

    Variable-rate-supported adaptive synchronization in Ad-hoc network

    LI Wei-ying;Lü Zhuo;LI Jian-dong;TANG Wei-liang
    J4. 2005, 32(5):  737-741. 
    Abstract ( 1642 )   PDF (186KB) ( 947 )   Save
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    Based on the principle of the M-ary orthogonal spread spectrum, we propose a fast variable-rate-supported synchronization method by an assistant logic channel. Data and synchronization information are transmitted in data and assistant channel respectively. Different combinations of Barker codes make up the synchronization codes to represent different rates. By the principle of the matched filter and the characteristic of mobile channels, an adaptive threshold algorithm is also proposed for Ad-hoc networks.
    On the forbidden state avoidance of resource allocation systems
    WANG An-rong;DUAN Jiang-tao;LI Zhi-wu;JIA Jian-yuan
    J4. 2005, 32(5):  742-747. 
    Abstract ( 1945 )   PDF (250KB) ( 924 )   Save
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    Developed in this paper is a new strategy for avoiding forbidden states of resource allocation systems. The strategy is based on Petri nets and their structural analysis, with the Petri nets bounded and covered by initial marked P-invariants. This approach is first to orderly conduct off-line computations of some special states or markings, such as dead(lock) markings, bad markings, and dangerous markings, of the system's Petri net model, and then make on-line the system never reach a forbidden state such as dead(lock) markings and bad markings. The major advantage of the technique lies in the fact taht it is suitable for much larger resource allocation systems than the most existing ones and the supervisory control is maximally permissive. Meanwhile, the computation is successfully avoided for the whole reachability graph of the Petri net of the system.

    Stability analysis of networked switching systems with output transfer delay

    YU Shui-qing;LI Jun-min
    J4. 2005, 32(5):  748-752. 
    Abstract ( 1468 )   PDF (194KB) ( 839 )   Save
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    In order to improve the dynamic performance of the networked switching systems due to time-delay, a switching observer and a switching controller are designed by means of the Lyapunov stability theory. A sufficient condition for the stability of the closed-loop networked switching systems is obtained for the arbitrary switching rule and arbitrary time-delay. Finally, a cone complementarity linearization method is also given to solve the gains of the switching obsrver and of the switching controller, with an example showing the efficiency of the proposed approach.

    The scheme for the identification of the channel impulse response in channel estimation of OFDM systems

    XIAO Ye-ping;GE Jian-hua;WANG Yong
    J4. 2005, 32(5):  753-757. 
    Abstract ( 1778 )   PDF (206KB) ( 1356 )   Save
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    This paper investigates the channel estimation and interpolation technique in the COFDM demodulation scheme. To combat the OFDM symbol timing synchronization offset error and the delay spread of the channel impulse response, it presents a new channel estimation technique suitable for the comb-type pilot scheme. The identification of the channel impulse response is applied in this scheme and a low complexity identification is presented.

    Timing and frequency synchronization method for wireless OFDM systems

    REN Guang-liang;CHANG Yi-lin;ZHANG Hui;ZHANG Hui-ning
    J4. 2005, 32(5):  758-761. 
    Abstract ( 1789 )   PDF (164KB) ( 933 )   Save
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    Based on the analysis of the synchronization training symbols in orthogonal frequency division multiplexing (OFDM) systems, a new training symbol weighted by the pseudo-noise(PN) sequence is designed, and the corresponding synchronization method is proposed. In the proposed method, the correlation properties of the PN weighted factor and the training symbol are utilized in the timing offset estimation. Based on the timing synchronization, the PN weighted factor in the training symbol is removed, and the renewed training symbol is used to estimate the frequency offset. Simulation results show that the accuracy of timing synchronization and the estimate range of the frequency offset outperform those of the other available methods.

    A cluster maintenance method for self-organized network management

    SHEN Zhong;CHANG Yi-lin;ZHANG Xin
    J4. 2005, 32(5):  762-767. 
    Abstract ( 1678 )   PDF (273KB) ( 928 )   Save
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    To alleviate the influence of the node mobility on the self-organized network management based on clustering, a method for cluster maintenance is proposed. By periodically calculating the link availability between a cluster head and its agents, the stability of the cluster head is quantitatively measured, and the network management service is migrated from an unstable cluster head whose stability is below a specific threshold value to a stable node in the cluster. The simulation results show that, our method makes the network management more efficient by increasing the cluster lifetime and decreasing the number of the disappeared clusters.

    The design of the stable fractional model reference adaptive control system

    ZHANG Long-ge;LI Jun-min;CHEN Guo-pei
    J4. 2005, 32(5):  768-771. 
    Abstract ( 1571 )   PDF (179KB) ( 909 )   Save
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    This paper studies a novel adaptive control strategy for a linear system with unknown parameters. To design a control law with perfective dynamic performance, a new model reference adaptive control system has been designed by constructing a fractional-order Lyapunov function, with the stability of the closed-loop system proved. An example’s simulation shows that the closed-loop system has the better dynamic performance such as less regulating time and less overshoot than by the traditional method.

    A new low-cost channel estimation method for MIMO-OFDM system

    LIU Gang;GUO Yi;GE Jian-hua
    J4. 2005, 32(5):  772-776. 
    Abstract ( 2132 )   PDF (213KB) ( 955 )   Save
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    An accurate channel estimation is crucial for the performance of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. In this paper, a novel pilot pattern with higher frequency efficiency is proposed, and a linear minimum mean squared error (LMMSE) channel estimator is derived for MIMO-OFDM systems. In order to track the time-varying channel, an improved direct decision (DD) method is further adopted. Theoretical analysis and numerical results show that the new channel estimation scheme can offer a good performance and a high ability to track the time-varying channel, meanwhile it requires a low complexity especially for systems with a large number of transmit antennas.

    Forgery attack on a proxy-blind signature scheme

    FU Xiao-tong;LU Ming-xin;XIAO Guo-zhen
    J4. 2005, 32(5):  777-780. 
    Abstract ( 2952 )   PDF (151KB) ( 1052 )   Save
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    We propose a forgery attack on a proxy blind signature scheme proposed by Tan et al. By using the forgery attack, a dishonest original signer can forge the proxy signing key and produce valid proxy blind signatures. By successfully identifying the forgery attack, we show that their scheme is insecure. Furthermore, to improve Tan et al's scheme, we propose an improved proxy blind signature scheme.

    A new delegation of the decryption scheme for P2P data sharing

    ZHAO Heng;QUAN Yi-ning;HU Yu-pu
    J4. 2005, 32(5):  781-785. 
    Abstract ( 1501 )   PDF (216KB) ( 862 )   Save
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    By applying the secret sharing system and the zero knowledge proof protocol, this paper presents a new time constraint delegation of the decryption scheme based on trust agent platforms, which solves the problem that the accessed peer cannot offer instant data when it is offline. This scheme carries out encryption and decryption by using ElGamal cryptography. It defines the delegating-agents protocol, the produce of the delegation-key protocol and the decryption protocol, thus implementing the cheat-resisted and quorum controlled time constraint delegation of decryption. And the new scheme is supplemented to settle the problems of the key being renewed dynamically, the agent being added or deleted and the agent’s information being maintained. Compared with the previous time constraint delegation of the decryption scheme, it improves security, flexibility and efficiency.

    An improved dynamic traitor tracing scheme

    SU Jia-jun;LIU Jing-mei;WANG Xin-mei
    J4. 2005, 32(5):  786-789. 
    Abstract ( 1436 )   PDF (164KB) ( 840 )   Save
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    A layered concept of user sets based on the matrix theory is presented and users are marked by the robust watermarking. A new dynamic traitor tracking scheme is constructed, which identifies the traitors level by level. The scheme in this paper can efficiently combat the immediate and delay rebroadcast attack, and possesses much lower tracing complexity and computation complexity.

    A new fast algorithm for constructing depressed functions

    CHEN Jie;HU Yu-pu;WEI Yong-zhuang
    J4. 2005, 32(5):  790-793. 
    Abstract ( 1590 )   PDF (174KB) ( 927 )   Save
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    This paper presents a new fast algorithm for constructing depressed functions g based on cryptographic functions splitting idea. By splitting different selected variables using the algorithm, we can construct a system of equations after [k/2」 times of function decomposition and solving the system of equations will result in the depressed functions g. The degree of the functions g solved by this algorithm is at most [k/2」 such that the degree of fg is at most 「k/2]. Its computational complexity is given as O(2k/2)w+2, which is lower than the computational complexity O((2k-1)w) available when k is large. The result turns out that depressed functions g can be constructed in lower complexity.

    An efficient anonymous fingerprinting scheme based on the bilinear Diffie-Hellman intractability assumption

    WEI Ling-bo;YANG Bo
    J4. 2005, 32(5):  794-797. 
    Abstract ( 1260 )   PDF (156KB) ( 804 )   Save
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    In the gap Diffie-Hellman group, based on the bilinear Diffie-Hellman intractable assumption and the security two-party computation protocol, a new efficient anonymous fingerprint scheme is proposed. This scheme is not only short in key size due to the use of the elliptic cryptosystem, but also efficient in computation because of bilinear mapping.

    Fuzzy congruence pairs of the completely regular semigroup

    ZHANG Peng-ge;LIU San-yang
    J4. 2005, 32(5):  798-801. 
    Abstract ( 1186 )   PDF (173KB) ( 825 )   Save
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    The method of kernel-trace is successful in the study of congruence of the semigroup. The fuzzy set is the generalization of the classical set, while the fuzzy relation is a special function. In this paper we study the fuzzy kernel-trace of the fuzzy congruence relation on some class semigroup, that is, the notions of fuzzy kernel and fuzzy trace of a fuzzy congruence relation on a completely regular semigroup; we establish these notions by introducing fuzzy congruence pairs. Finally, we put emphasis on a one-to-one corre-spondence between fuzzy congruence pairs and fuzzy congruence on a completely regular semigroup.

    On the methods of seismic data instantaneous attributes estimate in time-frequency domain

    WANG Jin-guo1;TIAN Feng1;LIAO Zu-wen2;WANG Ming-xiang1
    J4. 2005, 32(5):  802-806. 
    Abstract ( 1649 )   PDF (227KB) ( 1169 )   Save
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    In order to impvoe the estimate precision of the seismic data instantaneous attributes (IA) in time-frequency domain and so much the better show the strata characteristics, the new method for the reassigned short-time Fourier transform of seismic data is applied. After applying this method to the seismic model and practical seismic data, a conclusion is made that the calculation precision is much higher than that of the method based on the short-time Fourier transform; and the method is very valid for studing the seismic data instantaneous attributes. Extending and the contacting of the strata can be clearly shown too.

    Carrier frequency offset estimation for OFDM systems

    REN Ai-feng1;2;YIN Qin-ye1
    J4. 2005, 32(5):  807-812. 
    Abstract ( 1843 )   PDF (266KB) ( 986 )   Save
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    The Orthogonal Frequency Division Multiplexing(OFDM) is broadly considered as an effective approach to future high-speed wireless multimedia communications. But it is very sensitive to carrier frequency offset between the transmitter and the receiver local oscillators, which causes intercarrier interference (ICI). Thus, in OFDM communication sytems, carrier frequency offset must be estimated and compensated at the receiver to minimize the effects of intercarrier interference and maintain orthogonality. In this paper, the mathematical model of OFDM systems with cyclic prefix (CP) and virtual subcarrier is derived first. We propose a new carrier frequency offset estimation algorithm using the DOA-MATRIX method. After the rough estimation, it can acquire the frequency offset with low computing complexity, and matrix including channel information simultaneously, which are favorable for offset compensation and demodulation of received signals. Numerical simulations can illustrate the performance of this algorithm.

    A structure based windowless image filter and its applications

    SONG Huan-sheng1;WANG Yang-li2;WU Cheng-ke2
    J4. 2005, 32(5):  813-817. 
    Abstract ( 1878 )   PDF (172KB) ( 1030 )   Save
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    The realization and application of a windowless nonlinear image filter are studied. In the windowless nonlinear image filter, an input gray-scale image is transformed into a group of binary parts by threshold decomposition, and then nonlinear windowless filter operation is performed on these binary images. As it is usually very easy to segment image structures in a binary image, so we can handle the image based on meaningful image structures instead of distinct image pixels. But the original windowless filter algorithm needs very heavy computation, so it is unpractical. To overcome this drawback, two solutions are given: 1)by reducing the amount of the binary images of threshold decomposition, one can cut down a lot of computation of threshold decomposition and reconstruction; 2)in image structure analysis, instead of the binary images, the contour lines are used, so the complex threshold decomposition and reconstruction process are bypassed. As a real application, the results of car license plate location by the new filter are reported.

    Construction of ω-IPP codes based on a class of error-correcting code

    PU Li-qun1;2;YIN Wei-yi2
    J4. 2005, 32(5):  818-819. 
    Abstract ( 1429 )   PDF (101KB) ( 945 )   Save
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    The identifiable parent property code can be used as the data fingerprint for copyright protection. The sufficient conditions are presented for the construction of IPP codes based on error-correcting codes(ECC). An upper bound of ECC is also given. The sufficient conditions are not only useful in the construction of IPP codes from error-correcting codes(ECC), but also avaliable in practice for copyright protection.

    Sequential importance sampling method for tracking a maneuvering target with a single passive observer

    XIN Yun-hong1;WANG Bao-ping2;YANG Wan-hai3
    J4. 2005, 32(5):  820-824. 
    Abstract ( 2164 )   PDF (224KB) ( 1054 )   Save
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    An IMM-SIS(Interacting Multiple Model-Sequential Importance Sampling) algorithm is presented for tracking a maneuvering target by a proper combination of two approaches: IMM and SIS, and it is used in the single passive tracking system. The advantage of the presented algorithm over the IMM-GSPF(Gaussian Sum Particle filter) is that it does not need the resampling step and avoids the particle degeneracy and impoverishment phenomenon. The performance of the IMM-SIS algorithm is verified by simulating a highly maneuvering target tracking. Results show that the tracking speed and accuracy of the IMM-SIS algorithm are better than those of the IMM-GSPF, the tracking robustness and accuracy of the SIS and GSPF algorithms are better than those of the classical EKF.

    Interval-valued fuzzy subgroupoid and ideals in right involution groupoid

    ZHOU Ya-lan1;GAO Shu-ping2;PU Yi-shu1
    J4. 2005, 32(5):  825-828. 
    Abstract ( 1459 )   PDF (179KB) ( 828 )   Save
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    In cryptology, the symmetry encryption and kinds of the public-key crypto systems are summarized for the operations of group. For the development of cryptology, it is necessary to study deeply the group theory. Therefore, we have studied the nature of right involution groupoid and its Fuzzy ideal. Suppose A to be the i-v Fuzzy set of right involution groupoid X, then a necessary and sufficient condition for the i-v Fuzzy subgroupoid (ideal) is presented.
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