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    20 April 2010 Volume 37 Issue 2
      
    Original Articles
    Joint transceiver design for multiuser MIMO systems in the case of correlated channels
    CHEN Rui;LI Jian-dong;LIU Wei;LI Chuan
    J4. 2010, 37(2):  181-185+203.  doi:10.3969/j.issn.1001-2400.2010.02.001
    Abstract ( 1424 )   PDF (696KB) ( 1582 )   Save
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    In a block diagonal (BD) algorithm based multi-user MIMO downlink transmission system, a dramatic capacity loss is introduced when there is a strong correlation among row vectors of the different users' channel matrix. Specifically, two parameters for measuring the correlation are investigated. For the purpose of recovering the capacity loss, a joint transceiver design is proposed, where based on the BD algorithm at the transmitter side, a decorrelation postprocessing (DP) algorithm is invoked on the receiver side. Then computer simulation results show that the proposed joint transceiver design can efficiently improve the system capacity in the case of correlated channels.

    Fast adaptive power control approach for cognitive radio networks
    LI Jian-dong;XUE Fu-guo;YANG Chun-gang;LI Wei-ying;SHI Hua
    J4. 2010, 37(2):  186-191.  doi:10.3969/j.issn.1001-2400.2010.02.002
    Abstract ( 2406 )   PDF (665KB) ( 1629 )   Save
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    An adaptive utility function based on the sigmoid function is proposed, which is related to the signal-to-interference plus noise (SINR) threshold and the obtained SINR, so that it will help to implement the opportunistic spectrum access by adaptively adjusting the SINR threshold, and it will satisfy the QoS requirement of multiple secondary users (SUs) fast. Meanwhile, considering the fairness among SUs, we rebuilt the pricing function to improve the Pareto optimality of the Nash equilibrium solution (NES). Based on all this, a power control model is investigated from the perspective of the non-cooperative game theory. The model is proved to be the super-modular game, and it can guarantee the existence and uniqueness of the NES. Simulation results show that the proposed power control algorithm can lead to converfence after 10 iterations, and that compared to the referenced algorithm it can save 10% power consumption and achieve mostly 15% improvement on the final utility.

    Multiuser MIMO downlink transmission strategy using independent component analysis
    LI Zhao;YANG Jia-wei;YAO Jun-liang;CHEN Ting
    J4. 2010, 37(2):  192-196.  doi:10.3969/j.issn.1001-2400.2010.02.003
    Abstract ( 1938 )   PDF (728KB) ( 1227 )   Save
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    We introduce a multiuser MIMO (MU-MIMO) downlink transmission strategy to solve the transmission problem for MIMO broadcast channels without available channel state information (CSI). By use of the scheme, base station (BS) selects a set of mobile stations (MS) and communicate simultaneously. Each transmit antenna at BS corresponds to an MS in the active user subset. The MS applies independent component analysis (ICA) algorithm to demix different components from the received mixing signals and identifies its own. Simulation results show that by applying the proposed strategy, MU-MIMO downlink transmission can be implemented successfully without CSI.

    Robust Capon beamforming algorithm under the steering vector uncertainty set
    LIU Cong-feng;LIAO Gui-sheng
    J4. 2010, 37(2):  197-203.  doi:10.3969/j.issn.1001-2400.2010.02.004
    Abstract ( 1954 )   PDF (665KB) ( 2450 )   Save
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    For the problem of solving the Capon beamforming algorithm under the steering vector uncertainty set, a novel method is proposed. By analyzing the characteristic of the robust optimization problem and its solving process deeply, the new solution is given, and the selection of the uncertainty constraint parameter becomes simpler, moreover, the improvement performance of the beamforming algorithm can reach the optimum. And the conclusion is drawn that the negative loading can obtain the optimal improvement performance, and the larger the selected constraint parameter, the closer to the optimum the performance of the beamforming algorithm will be. Furthermore, the zero solution can be effectively avoided by the rational selection of the constraint parameter. The final simulation attests its correctness and effectiveness.

    Minimum module value cascaded canceller
    HUANG Qing-dong;ZHANG Lin-rang;LU Guang-yue
    J4. 2010, 37(2):  204-209.  doi:10.3969/j.issn.1001-2400.2010.02.005
    Abstract ( 1774 )   PDF (935KB) ( 1217 )   Save
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    Due to the defects of large operation and instability convergence performance in the array signal adaptive canceller under the interference, the paper proposes an enhanced array signal cascaded canceller, which has the advantages of fast convergence, smaller amount of operation and good performance with non-stationary samples. Simulation results indicate that the algorithm can reach the  same convergent performance by using half samples as the sample matrix inversion (SMI) algorithm.

    Adaptive radar channel equalization approach in the echo data domain
    LIU Xiang-yang;LIAO Gui-sheng;ZHU Sheng-qi;MAO Zhi-jie
    J4. 2010, 37(2):  210-217.  doi:10.3969/j.issn.1001-2400.2010.02.006
    Abstract ( 1542 )   PDF (1092KB) ( 1315 )   Save
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    In the actual airborne multi-channel GMTI system, the mismatch error exists in different channels and degrades the capability of repression for the ground clutter, thus affecting the detection of weak moving targets. To deal with this problem,  a novel channel equalization approach based on the ground clutter data is presented. In this method, according to the characteristic of the ground clutter for multi-channel radar, the wiener filter technique is applied to evaluate and compensate the mismatch errors, without refitting the radar equipments in use. Then the relationship between the performance and the correlation coefficient of the ground clutter signal is analyzed in the situation of limited samples. Finally, the effectiveness of the method proposed is validated by measured data.

    Multiple passive-radar based time-varying number targets tracking algorithm
    SHI Yin-shui;JI Hong-bing;YANG Bai-sheng
    J4. 2010, 37(2):  218-223.  doi:10.3969/j.issn.1001-2400.2010.02.007
    Abstract ( 1916 )   PDF (630KB) ( 1467 )   Save
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    A new recursive algorithm is proposed for jointly estimating the time-varying number of targets and their states through passive radar measurements. Firstly, multi-sensor central fusion scheme is adopted to improve the weak observability for passive systems. Secondly, the least square method is embedded to calculate pseudo-location measurements by which the nonlinearity is solved. Thirdly, for the scenario of the time-varying target number, the new approach involves modeling the collections of targets and measurements as random finite sets (RFSs), respectively, and applying the Gaussian mixture probability hypothesis density (GMPHD) recursion to propagate the posterior intensity, which is a first-order statistic of the random finite sets by which both the time-varying number and states of multiple targets could be estimated properly. Furthermore, data association is accomplished by all potential targets located by the least square algorithm, which could avoid the decrease of association reliability when lines of sight (LOS) from different targets are close to each other. Simulation results in a scenario of tracking targets through multiple passive sensors show the advantages of the proposed algorithm.

    Composite enhancing and denoising algorithm for SAR images based on scale space correlation
    YIN Kui-ying;HU Li-ping;LIU Hong-wei;JIN Lin
    J4. 2010, 37(2):  224-230.  doi:10.3969/j.issn.1001-2400.2010.02.008
    Abstract ( 2141 )   PDF (1911KB) ( 1681 )   Save
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    A composite adaptive enhancing and denoising algorithm for SAR images is presented. The SAR images are differentiated from speckle noise via scale space correlation. Because the SAR image can be described by approximate rayleigh's distribution, the complex diffusion coupled shock filter is used to enhance the signal differentiated from SAR image, and the anisotropic diffusion equation is used to denoise the speckle in the SAR image. Finally, the SAR image is reconstructed by stationary wavelet transform. Compared with traditional speckle removal algorithms, this new algorithm has better performance in terms of edge preserving and denoising.

    Method for geometric distortion correction of the bistatic SAR
    YI Yu-sheng;ZHANG Lin-rang;LIU Xin;LIU Nan;ZHANG Bo
    J4. 2010, 37(2):  231-234.  doi:10.3969/j.issn.1001-2400.2010.02.009
    Abstract ( 1862 )   PDF (739KB) ( 1329 )   Save
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    The existence of the differences in squint angle and velocity between transmitter and receiver in the bistatic synthetic aperture radar(SAR) makes the imaging results distorted. This paper concerns the issue of bistatic SAR image geometric correction. According to the geometry of the bistatic SAR, the slant range history is particularly analyzed. In addition, the equivalent phase center (EPC) method is used to transform the bistatic model to a monostatic equivalent. Then, the expression of the geometric distortion correction for the bistatic SAR image is derived based on the  RD imaging algorithm. Finally, the validity of the method is demonstrated by simulation.

    Parameter estimation of the fast moving target based on tri-channel airborne SAR-GMTI
    QIAN Jiang;Lü Xiao-lei;XING Meng-dao;LI Liang-hai;ZHANG Zhen-hua
    J4. 2010, 37(2):  235-241.  doi:10.3969/j.issn.1001-2400.2010.02.010
    Abstract ( 1998 )   PDF (2265KB) ( 1335 )   Save
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    In a conventional SAR/GMTI system, it is hard to obtain the information on the fast moving target. An approach for fast moving target indication and motion parameter estimation is proposed based on PRF ambiguity resolving. In the range frequency and compressed azimuth time domain of Tri-channel SAR/GMTI data, the clutter is cancelled by the mutual channel, and the PRF ambiguity number can be estimated from the remaining signals. This approach utilizes the relation between the line slope and the ambiguity number of the fast moving target in the domain to get the ambiguity number and thus the slope of the line through Radon transform. Azimuth focusing under the criterion of entry-minimization is implemented following effectiveness azimuth migration compensation, and the fast moving target is imaged after range match filtering. The results of simulation and real data processing show the effectiveness of the approach.

    Novel method for DOA estimation of coherent signals by eigen-subspace iteration
    YANG Xue-ya;CHEN Bai-xiao;ZHU Gen-sheng
    J4. 2010, 37(2):  242-247.  doi:10.3969/j.issn.1001-2400.2010.02.011
    Abstract ( 1864 )   PDF (668KB) ( 1258 )   Save
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    A novel method for direction-of-arrival estimation of the correlated-signal is proposed to enhance the adaptability of the traditional high-resolution methods and to reduce the computational burden caused by eigen-decomposition and searching procedure. The noise subspace or signal subspace is iteratively obtained by the gradient algorithm for each snapshot, and then it is transformed from complex-valued space to real-valued space. Finally, Unitary ESPRIT or Root-MUSIC based on real-valued space is used to estimate the angles. Introduction of the eigen-subspace iteration and real-valued space processing eliminates eigen-decomposition, thus reducing the computational complexity significantly. The method can also be applied to the angle estimation and angle tracking problems for coherent signals. Simulations and real data processing results verify the effectiveness of the proposed method.

    Auto-adaptive filtering of the InSAR interferometic phase based on the modification Goldstein algorithm
    YAN Wei-dong;NI Wei-ping;ZHAO Yi-gong;LU Ying;WU Jun-zheng
    J4. 2010, 37(2):  248-253+259.  doi:10.3969/j.issn.1001-2400.2010.02.012
    Abstract ( 2157 )   PDF (2422KB) ( 1326 )   Save
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    Based on the Goldstein algorithm for InSAR interferometic phase filtering, an auto-adaptive spectrum weight function is constructed in place of the original fixed value ascertained artificially, and its exponential power parameter is calculated by the local coherence. Over filtering and under filtering problems are solved when processing the complex interferometric stripes caused by the uniform filtering. Experimental results from simulated data and ERS data indicate the validity of the modification algorithm, with good denoising effect and nice preserving of the phase resolution.

    A new robust watermark algorithm in the contourlet domain
    TONG Ming;FENG Wei;JI Hong-bing
    J4. 2010, 37(2):  254-259.  doi:10.3969/j.issn.1001-2400.2010.02.013
    Abstract ( 1541 )   PDF (655KB) ( 1300 )   Save
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    In order to improve the robustness and efficiency of the watermark algorithm, a new self-adaptive watermark algorithm based on the texture feature is proposed. This algorithm selects the energy, entropy and contrast of the gray co-occurrence matrix as texture features, rapidly and accurately extracts the strong texture region of host images by the Mean Shift fast clustering algorithm. This algorithm embeds the watermark into the big coefficients in the Contourlet domain of the image strong texture area, adaptively selects the watermark embedding locations and controls the watermark embedding strength through texture clustering outcome. The experiment shows that this algorithm has the strong robustness to the Gauss low pass filter, Wiener filter, median filtering, Salt and pepper noise, Gaussian noise, JPEG compression, shear attack, etc. This algorithm's convergence rate is better than that of both FCM clustering and K-means clustering algorithm. This algorithm has realized blind detection.

    Novel detection method for HRRP data
    XIA Yu-yin;FENG Da-zheng;LI Tao
    J4. 2010, 37(2):  260-266+284.  doi:10.3969/j.issn.1001-2400.2010.02.014
    Abstract ( 1899 )   PDF (878KB) ( 1265 )   Save
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    A novel detection method dealing with range walking for the broadband radar target using high resolution range profiles (HRRP) is proposed. The proposed detector, the iterative generalized likelihood rate test (iGLRT), is derived by estimating the signal steering vector through a bi-iterative algorithm (BIA) after constraint range alignment and estimation of the length and position of the target. Furthermore, global convergence is analyzed and the constant false alarm rate (CFAR) property is proved. Finally, experimental results for measured data of two planes illustrate that the proposed algorithm leads to at least 1.4dB improvement for 80% detection possibility compared with the conventional scatter density dependent generalized likelihood rate test (SDD-GLRT).

    Non-coherent integration algorithm based on HRRP data
    LI Tao;FENG Da-zheng;XIA Yu-yin
    J4. 2010, 37(2):  267-272.  doi:10.3969/j.issn.1001-2400.2010.02.015
    Abstract ( 1611 )   PDF (755KB) ( 1499 )   Save
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    A new algorithm for detecting the maneuvering target with an unknown velocity based on high resolution range profiles (HRRP) of the wideband high resolution radar is proposed. In order to improve the estimation precision in the low signal-to-noise ratio (SNR), the proposed algorithm estimates the velocity of the target and the location of the strongest scattering cells relevant to the target's scattering geometry by the improved two-way viterb algorithm, and then together with the non-coherent integration of the primary range cells chosen around the location of the strongest scattering cells, it improves the detection performance. Experimental results through measured data of two planes illustrate that the proposed algorithm leads to a visible performance improvement compared with conventional non-coherent integration in the presence of range walking.

    Sinusoidal weighted frequency modulation jamming technique against moving target detection radar
    ZHU Yan;CUI Yan-peng;ZHAO Guo-qing
    J4. 2010, 37(2):  273-278.  doi:10.3969/j.issn.1001-2400.2010.02.016
    Abstract ( 2024 )   PDF (1393KB) ( 1422 )   Save
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    A novel model to produce sinusoidal weighted frequency modulated jamming is put forward. And it is used to jam moving target detection and imaging. In the model, the radar transmitting signal frequency is modulated by the sinusoidal frequency. It is then convoluted with the false moving model signal and retransmitted. The jamming signal frequency is modulated by the sinusoidal frequency, so the signal difference between dual channels increases and there is less correlation. When the power ratio of the moving target echo to the jamming signal is between -16dB and -12dB, big errors occur in velocity and cross-range coordinate. Deception jamming can be obtained. When the power ratio between moving target echo and jamming signal is less than -16dB the detection threshold grows under the influence of the jamming signals of great power. And detection probability falls rapidly. By simulation the method has a good effect on jamming moving target detection and is realized easily.

    Mobility supporting adaptive MAC protocol in WSN
    CHEN Chen;GAO Xin-bo
    J4. 2010, 37(2):  279-284.  doi:10.3969/j.issn.1001-2400.2010.02.017
    Abstract ( 1948 )   PDF (722KB) ( 1495 )   Save
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    A mobility supporting adaptive MAC protocol RM-MAC (RSSI based Mobility support MAC) in the wireless sensor network is proposed. First, we quantize the nodes' receiving range and get the neighboring nodes list based on quantized RSSI values.Then, using the Kalman filter model, we predict the mobile nodes' position vector after an investigated period. Finally, employing the quantized RSSI values and forecasted position vectors, we build the dynamic synchronization adjustment model within the virtual clusters in order that the clusters can maintain a high connectivity with mobile nodes. Simulation results show that compared with S-MAC, RM-MAC can obtain a higher network connectivity and delivery ratio by dynamically adjusting the synchronization frequency at a price of sacrificing certain energy. Furthermore, we find that the delivery ration has a close relationship with the quantification level and cluster switch threshold.

    Specific emitter recognition based on feature optimization of ambiguity function zero-slice
    WANG Lei;JI Hong-bing;LI Lin
    J4. 2010, 37(2):  285-289+304.  doi:10.3969/j.issn.1001-2400.2010.02.018
    Abstract ( 1517 )   PDF (1067KB) ( 1273 )   Save
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    A novel specific emitter recognition algorithm is proposed to mitigate the computation problem and instability of kernel points ranking in the ambiguity function optimization method. It extracts the zero-slice of the ambiguity function as an intermediate feature set and employs the Direct Discriminant Ratio (DDR) criterion to rank the kernel points along the obtained slice. The resulting scheme not only improves the recognition accuracy greatly, but also preserves the most discriminant features of the individual emitter efficiently and avoids the “out of memory” problem in large whole-plane optimization. Experiments on both synthetic radar data from the U.S. Naval Research Laboratory and real radar emitter data demonstrate the feasibility and effectiveness of the proposed method.

    Printed dipole antenna array with wideband and low RCS characteristics
    YUAN Hong-wei;GONG Shu-xi;WANG Wen-tao;ZHANG Peng-fei
    J4. 2010, 37(2):  290-294.  doi:10.3969/j.issn.1001-2400.2010.02.019
    Abstract ( 1833 )   PDF (1539KB) ( 1573 )   Save
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    A new printed dipole antenna array is given. In order to further increase bandwidth capabilities of this antenna, a novel low-cost smaller unit-cell planar photonic bandgap (PBG) structure is etched onto the antenna surface. By optimizing the sizes of the PBG structure, a bandwidth is of 56.7% is obtained where the voltage standing wave ratio (VSWR) is less than 1.5 while a bandwidth of 36% is obtained from the traditional structure. Moreover, a new Frequency Selective Surface (FSS) is used for the ground of the array antenna, which can reduce the radar cross section(RCS) of the antenna array.

    Method for RCS reduction of the mircostrip patch antenna
    LING Jin;GONG Shu-xi;ZHANG Peng-fei;YUAN Hong-wei;LU Bao;WANG Wen-tao
    J4. 2010, 37(2):  295-299.  doi:10.3969/j.issn.1001-2400.2010.02.020
    Abstract ( 2836 )   PDF (1333KB) ( 1330 )   Save
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    To reduce the RCS (Radar Cross Section) of a microstrip patch antenna, the UC-EBG structure is used as the ground plane of a microstrip patch antenna because of the stop-band property of the UC-EBG. In the pass-band, the UC-EBG can let many more incident waves pass. Therefore, it can effectively reduce the RCS of the microstrip patch antenna outside operating band. The simulated and measured results are in good agreement with each other and show that this method is effective.

    Image denoising based on wave atoms and cycle spinning
    SONG Yi-mei;SONG Guo-xiang
    J4. 2010, 37(2):  300-304.  doi:10.3969/j.issn.1001-2400.2010.02.021
    Abstract ( 1693 )   PDF (955KB) ( 1340 )   Save
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    A new method for image denoising is presented, which colligates the strongpoint of the wave atoms transform and Cycle Spinning.Due to lack of translation invariance of the wave atoms transform,image denoising by coefficient thresholding would lead to Pseudo-Gibbs phenomena. Cycle Spinning is employed to avoid the artifacts.Experimental results show that the method can remove noisy and remaining edges, while Pseudo-Gibbs phenomena are controled efficiently, and can get a better visual effect and PSNR gains compared with the methods like simplex wave atoms or wavelet denoising using Cycle Spinning.And in heavy background noise, this advantage is significant.

    Practical broadcast authentication protocol for sensor networks
    DU Zhi-qiang;SHEN Yu-long;MA Jian-feng;ZHOU Li-hua
    J4. 2010, 37(2):  305-310+325.  doi:10.3969/j.issn.1001-2400.2010.02.022
    Abstract ( 2801 )   PDF (610KB) ( 1290 )   Save
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    Broadcast authentication is one of the most important security primitive services in Sensor Networks. With more and more senders in a network, costs of Tree-based μTESLA are rising rapidly, which limits strictly the scale of networks employing it. Aiming at eliminating such a limit, this paper presents a μTPCT-based broadcasting authentication protocol which mainly rests on constructions of μTPC(μTESLA Parameters Hash Chain) and μTPCT(μTPC Merkle Hash Tree). Analysis and experiments have shown that our proposed protocol not only possesses both excellent resistance to DoS attacks against the distribution of μTESLA parameters and the ability to revoke authenticating capabilities of compromised nodes instantly, but also greatly outperforms the Tree-based μTESLA by largely reducing the cost of computation, communication, and storage needed, making it more applicable to large-scale sensor networks.

    Novel method for counting short cycles of Tanner graphs
    JIAO Xiao-peng;MU Jian-jun;ZHOU Li-hua
    J4. 2010, 37(2):  311-314.  doi:10.3969/j.issn.1001-2400.2010.02.023
    Abstract ( 1875 )   PDF (554KB) ( 1307 )   Save
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    Short cycles have an important influence on iterative decoding for low-density parity-check (LDPC) codes. By using tree expanding of Tanner graphs and the analysis of the influence of invalid cycles and duplicate cycles, a formula for counting short cycles of LDPC codes is derived. With the derived formula, an algorithm for counting short cycles of Tanner graphs based on tree expanding is proposed. The proposed algorithm can count short cycles with arbitrary lengths, and thus overcomes the disadvantage of existing algorithms that count short cycles with given lengths. Numerical results of counting short cycles of some typical LDPC codes show the correctness of the proposed algorithm.

    Decimation filter design for 14-bit 1.28MS/s sigma-delta ADC
    YANG Yin-tang,LI Di,SHI Li-chun
    J4. 2010, 37(2):  315-319.  doi:10.3969/j.issn.1001-2400.2010.02.024
    Abstract ( 1655 )   PDF (738KB) ( 1408 )   Save
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    A decimation filter for a 4th-order single-bit single-loop oversampling sigma-delta modulator is designed. Consisting of multi stages, the decimation filter is used to filter the noise in the output signal of the modulator and has a decimation factor of 64. It has a small circuit area and low power dissipation. The filter has been fabricated by the TSMC 0.18μm CMOS process and operates at a voltage of 1.8V. Experimental results show that the output signal of the decimation filter has an SNDR (Signal-to-Noise-and-Distortion-Ratio) of 93.9dB which meets the requirement of the system design. The presented filter has a -6dB pass-band of 640kHz, a power dissipation of 33mW and occupies a die area of about 0.4mm×1.7mm.

    Structure of the low-power interpolation filter and  its VLSI implementation for all-digital receiver
    DENG Jun
    J4. 2010, 37(2):  320-325.  doi:10.3969/j.issn.1001-2400.2010.02.025
    Abstract ( 1634 )   PDF (982KB) ( 1744 )   Save
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    The interpolation filter is the key technology for realizing bit synchronization in all-digital receiver. This paper introduces the structure of the interpolation filter, which is suitable for VLSI. A new structure based on the Farrow structure of Lagrange is proposed, which can be used to improve the operational rate of the filter by pipelining and Parallel processing technology. A comparison in operational rate, hardware complexity and the energy consumption between improved structure and original structure is made. It has been realized by using FPGA.Simulation and experiment show that the structure has a faster operational rate and lower power.

    Low complexity PTS scheme for PAPR reduction of OFDM signals
    WANG Jin-xiang;WU Xin-chun;MAO Zhi-gang;ZHOU Bin
    J4. 2010, 37(2):  326-333.  doi:10.3969/j.issn.1001-2400.2010.02.026
    Abstract ( 2165 )   PDF (952KB) ( 1267 )   Save
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    A low complexity partial transmit sequence (PTS) scheme is proposed to improve the performance of the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. By analyzing the characteristic of candidate signals, the number of phase factor vectors is reduced from 64 to 16 without the loss of PAPR performance and the search time of the phase factor is reduced. The hardware cost of the IFFT unit can be reduced by adopting the group concept, rescheduling the time of the multiplication with twiddle factors, and using path-based constant multipliers instead of complex multipliers. In the IFFT unit, the hardware costs of complex multipliers, complex adders, and registers are respectively reduced by 58.8%, 28.6%, and 75.6% compared with four independent IFFT processors with radix 23 and single-path delay feedback. In addition, there is no need for ROM to store the twiddle factor. Moreover, because of the characteristic of the needed phase factor vectors, the hardware overhead of the optimization unit can be lessened.

    Full rate STBC cooperation scheme for the multi-antenna relay
    ZHANG Tian-kui;CHENG Jie;FENG Chun-yan
    J4. 2010, 37(2):  334-339.  doi:10.3969/j.issn.1001-2400.2010.02.027
    Abstract ( 2181 )   PDF (674KB) ( 1225 )   Save
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    In order to obtain the full rate and increase the diversity gain for multi-antenna relay space time block coded (STBC) cooperation, we combine relay STBC cooperation with the single relay's multi-antenna beam forming (BF) and propose a multi-antenna relay STBC cooperation (MARSC) scheme. The relay adopts orthogonal frequency division multiplexing (OFDM) for transmission, symbols in the same carriers are forwarded by the relay STBC cooperation, and BF is executed between antennas of the relay. Furthermore, we design a suitable finite rate feedback scheme to reduce the channel feedback overhead. Simulation results show that the proposed MARSC scheme can obtain the full rate and the high diversity gain which is brought by STBC cooperation and the relay's multi-antenna at the same time, when the user just employs the STBC decode algorithm, and that the proposed finite rate scheme can significantly reduce the channel feedback overhead with a smaller system performance loss.

    Active noise control system requiring no secondary path identification
    ZHANG Rui-hua;XIE Zhi-bo
    J4. 2010, 37(2):  340-345+358.  doi:10.3969/j.issn.1001-2400.2010.02.028
    Abstract ( 1716 )   PDF (931KB) ( 1383 )   Save
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    The effects of most active noise control algorithms rely on the identification of the secondary path, which usually leads to increased complexity as well as stability problems. Based on the strict positive real (SPR) property of the filtered-x LMS algorithm, a new ANC algorithm requiring no secondary path identification is proposed by introducing a phase compensating mechanism. Simulation results show that this algorithm can automatically find the right compensating phase of the secondary path and will always converge regardless of the noise frequency, compared with the existing method.

    Research on image enhancement for the heavy noised image based on structural similarity via gray relational analysis
    MA Miao;JIAO Li-li
    J4. 2010, 37(2):  346-352+365.  doi:10.3969/j.issn.1001-2400.2010.02.029
    Abstract ( 2039 )   PDF (1793KB) ( 1471 )   Save
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    To improve the heavy noised image quality, this paper proposes a new image enhancement algorithm. Firstly, the noised image is transformed into the wavelet domain via multiscale decomposition, and the information in different resolutions and different directions in the frequency domain are obtained. Then the regularities of coefficient distribution and attenuation characteristics of noise and edges in different subbands are employed to distinguish noise from edges and textures, and thus the image quality is improved by noise suppression and edge enhancement. Experimental results show that our algorithm is superior to most traditional spatial filters and new-developed methods based on the wavelet or contourlet transform both in visual effect and Peak-Signal-to-Noise Ratio (PSNR). It can be applied to image enhancement preprocessing in heavy noise environment.

    Optimal design of the dual-frequency Wilkinson power divider with the genetic algorithm
    WANG Wei;LI Wen-cheng;LAN Zhong-wen;CHEN Dan;ZHANG Kai
    J4. 2010, 37(2):  353-358.  doi:10.3969/j.issn.1001-2400.2010.02.030
    Abstract ( 3155 )   PDF (629KB) ( 1704 )   Save
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    The optimal design of the dual-frequency equal-split Wilkinson power divider with the genetic algorithm is proposed. The dual-frequency equal-split Wilkinson power divider is composed of a two-section transmission line transformer and two isolation resistors. Based on the ideal transmission line model, the even-odd mode technique is used to derive the design equations of parameters. Based on the above analysis, the parameters optimized with the Genetic Algorithm are discussed. In the Genetic Algorithm, elitist strategy、crossover and mutation of changing probability are preserved to prevent premature convergence. The performance of the Power Divider is analyzed by simulation with radio frequency software ADS. The result shows that impedances match well at all ports and that isolation between the two output ports is more than 40dB.Good performances of the optimized power divider at both frequencies are obtained.

    Seamless handover scheme for real time traffic
    ZHANG Zai-long;SUN Jian;ZHANG Shun-yi;SUN Yan-fei;LI Jun
    J4. 2010, 37(2):  359-365.  doi:10.3969/j.issn.1001-2400.2010.02.031
    Abstract ( 2393 )   PDF (825KB) ( 1260 )   Save
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    To improve the handover performance of real time traffic, Mobile IPv6 (MIPv6) and its enhancement mechanisms are studied. A new hybrid seamless handover scheme called IMIPv6 (Integrated MIPv6) is proposed, which integrates MIPv6, Fast Handovers for MIPv6 (FMIPv6), Hierarchical Mobile IPv6 (HMIPv6), buffer management, Link-layer Trigger (L2T) and bi-casting mechanisms. The IMIPv6 prototype and its test results are described. The handover delay, packet loss and handover signaling load of MIPv6, FMIPv6, HMIPv6 and IMIPv6 are simulated and analyzed with NS-2. The results show that IMIPv6 and FMIPv6 have the least packet loss and that IMIPv6 has the lowest handover delay and the biggest signaling load. IMIPv6 has advantages over MIPv6, FMIPv6 and HMIPv6 in handover speediness and smoothness, and thus is suitable for seamless handover of real time traffic.

    Special target detection of the SAR image via exponential wavelet fractal
    LIU Dong;ZHANG Gong
    J4. 2010, 37(2):  366-373+384.  doi:10.3969/j.issn.1001-2400.2010.02.032
    Abstract ( 1554 )   PDF (2318KB) ( 1350 )   Save
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    This paper proposes a new approach for the SAR image detection of the target with a certain size and direction. We filter the SAR image with exponential wavelet directionally, based on its selective enhancement of SAR target edges. Then a novel term Exponential Wavelet Fractal (EWF) feature is defined considering the filtered target's characteristics. EWF can detect the SAR target using the priori information on the target size and direction. Different from most traditional SAR detections, EWF not only distinguishes target pixels from the background only based on the contrast, but also is sensitive to the object direction and size. The validity of the EWF method for the detection of targets with a known size and direction is evaluated based on the MSTAR data.

    Modified modularity and the corresponding community structure detecting algorithm
    CHEN Ying-hui;DU Hai-feng;LI Shu-zhuo
    J4. 2010, 37(2):  374-379.  doi:10.3969/j.issn.1001-2400.2010.02.033
    Abstract ( 1652 )   PDF (738KB) ( 1301 )   Save
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    The community structure detecting strategies are one of the important research hot spots in the field of the community structure. Firstly, the basic characteristics of the network's community structure and the modularity are discussed, and then a basic algorithm framework based on the modularity for detecting the network's community structure is summarized. Secondly, based on the definition of Newman's modularity Q, a predigested modularity and the corresponding algorithm are explored. Lastly, compared with Newman's corresponding algorithms, the results of community detection for some networks, including Ucinet networks and Pajek networks, indicate that the algorithm based on the predigested modularity is effective to get the higher modularity and that the definition of the modularity can effect the results of detecting the community structure.

    Link Load Based Multicast Packet Diffusion Algorithm in the LEO Satellite Constellation System
    TUO Yan-jun;LIU Yun;LIU Yong-jian
    J4. 2010, 37(2):  380-384.  doi:10.3969/j.issn.1001-2400.2010.02.034
    Abstract ( 1874 )   PDF (633KB) ( 1282 )   Save
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    To solve the diffusion of multicast packets in the Inter-satellite Link(ISL) subnet with a heavy load, a multicast packet diffusion algorithm in the LEO satellite constellation system is presented. Based on the traffic distribution of each satellite node, the link load based breadth first tree algorithm is used to form the breadth first tree and the diffusion forwarding tables with the shortest paths to the target nodes. With these tables, the multicast packets can avoid the congested links and nodes, and can be diffused to each satellite node rapidly along the optimal loop-free route. The simulation results show that, with this algorithm, the diffusion time of multicast packets in the network under a heavy load is almost the same as that under a light load, and the packets are never lost. It can meet the shortest diffusion time of multicast packets and loop-free multicast routes requirements.

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