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Table of Content

    28 September 2011, Volume 29 Issue 5
    Communication Engineering
    Low Complexity Resource Allocation in OFDMA-Based Decode-and-Forward Relaying Networks
    TANG Lun, JIANG Guang-jian, CHEN Qian-bin
    2011, 29(5):  441-446.  doi:10.3969/j.issn.0255-8297.2011.05.001
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    This paper addresses joint subcarrier pairing, dynamic subcarrier allocation and power allocation which satisfies user expected rate in OFDMA-based decode-and-forward relaying networks for which users have different expected rate. A mathematical model for minimizing difference between the achievable and expected rates is established. Three algorithms are proposed. First, a joint subcarrier pairing and dynamic subcarrier allocation algorithm (ERDSA) with average power allocation is used. Second, if the system resource is insufficient, a joint subcarrier pairing and dynamic subcarrier allocation algorithm (EERDSA) with proportionate reduction of user expected rate can be used. When the system power is evenly allocated, the data rates of the first and the second hops are mismatched. In this case, a joint subcarrier pairing, dynamic subcarrier allocation and power allocation algorithm (DJSPA) is used. Analyses show that ERDSA, EERDSA and DJSPA have low complexity, linearly proportional to the number of subcarriers. Simulation shows that the proposed schemes can satisfy user expected rate and reduce power consumption.

    Cross-Layer Fuzzy Logic Broadcasting Algorithm for Ad Hoc Networks
    WANG Qing-wen1, SHI Hao-shan1, QI Qian2
    2011, 29(5):  447-452.  doi:10.3969/j.issn.0255-8297.2011.05.002
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     To solve the broadcast storm problem caused by blind flooding, a cross-layer fuzzy logic broadcasting algorithm for mobile ad hoc networks (CLFBA) is proposed. CLFBA allow the routing layer to share the received signal power of the MAC layer by the cross-layer design while still maintaining separation between the two layers. The rebroadcast probability is calculated with fuzzy logic, by which the nodes with more additional
    transmission range and residual energy have higher probability to rebroadcast the packets. CLFBA reduces redundant retransmission and the chance of contention and collision among neighboring nodes in the networks.It also balances energy consumption of the network. Simulation results demonstrate that CLFBA improves the saved rebroadcast and prolongs the network lifetime, reduces the average packet drop fraction per node
    and the average end-to-end delay, as compared with the blind flooding and fixed probabilistic flooding at the routing layer while IEEE 802.11 at the MAC layer.

    Reliable Mobile Multicast Scheme with Hierarchical Architecture and Fast Handover Capability
    LIU Hong-yue, MA Jian-feng, YANG Kai
    2011, 29(5):  453-458.  doi:10.3969/j.issn.0255-8297.2011.05.003
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    Although mobile IP multicast can adapt to scarce resource in wireless networks, it faces many technical challenges. A reliable mobile multicast scheme with a hierarchical architecture and fast handover capability (MMHFH) is proposed in this paper. MMHFH integrates micro-mobility and link-layer trigger methods, and emphasize on the mobile characteristics such as multicast maintenance overhead, handover latency, handover packet loss, out-of-synchronization, scalability and route stability. Results of simulation in an OPNET modeler show that MMHFH is an effective and reliable scheme with a more stable multicast distribution tree, less multicast maintenance overhead, shorter handover latency, lower packet loss rate, higher reliability, better scalability and higher multicast packet delivery efficiency.

    Composite Multicast Congestion Control by Multi-objective Particle Swarm Optimization
    2011, 29(5):  459-466.  doi:10.3969/j.issn.0255-8297.2011.05.004
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     To enhance throughput and smoothen the sending rate of large scale multicast in a heterogeneous environment, a composite multicast congestion control (CMCC) scheme is proposed. The rate in basic layer is controlled by the lowest receiver in a single-rate way, while the rates in enhanced layers are allocated by an optimizer. Aimed at maximizing global satisfaction and minimizing jitter of sending rates, rate allocation
    of layers is formulated as a multi-objective optimization problem. The multi-objective particle swarm optimization (PSO) algorithm is used to solve the multi-objective problem. The algorithm has advantages of fast convergence, small number of parameters and low computation complexity. Simulation results show that CMCC can enhance throughput as compared with traditional hybrid multicast congestion control scheme. It also has a smooth sending rate in streaming applications.

    Signal and Information Processing
    Denoising of Optical Coherence Tomography Image Using Dual-Tree Complex Wavelet Transform and Mixed Probability Model
    SHU Peng1, SUN Yan-kui1, TIAN Xiao-lin2
    2011, 29(5):  467-472.  doi:10.3969/j.issn.0255-8297.2011.05.005
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     To remove speckle noise in optical coherence tomography (OCT) images, the ProbShrink algorithm based on the dual-tree complex wavelet transform and a mixed probability model is employed. After studying the signal and noise distribution in OCT images, a mixed probability model in microscopic-level is introduced.
    Logarithm of the OCT image is first decomposed using dual-tree complex wavelet transform. The coefficients consistent with edges obey the generalized Gaussian distribution, while others obey the Gaussian distribution. An improved ProbShrink algorithm is used to shrink the wavelet coefficients. Experiments show that this
    method can significantly improve signal-to-noise ratio while hold edge preservation index relatively steady. The performance is better than that of traditional wavelet based OCT image denoising methods.

    Spatial Pooling Strategies for Image Quality Assessment Based on Local Structural Information
    WANG Bao-yun, ZHANG Rong, YIN Dong
    2011, 29(5):  473-482.  doi:10.3969/j.issn.0255-8297.2011.05.006
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    A spatial pooling strategies (SPS) for image quality assessment (IQA) is proposed, which obtain a weight map from local structural information (LSI) of the reference image. The reference image is first smoothed with a Gaussian kernel, and the LSI is extracted from the smoothed image. A weight map is derived from the LSI using a non-zero procedure. PSNR and SSIM obtained in the experiments show effectiveness of the proposed method for a wide range of image distortion types.

    Application of Descriptor in Evaluation of Target Camouflage Effectiveness
    JIA Qi|Lü Xu-liang|ZENG Zhao-yang|XU Wei-dong
    2011, 29(5):  483-486.  doi:10.3969/j.issn.0255-8297.2011.05.007
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     In order to evaluate effectiveness of target camouflage objectively and quantitatively, a model of similarity degree is established based on a descriptor of attention focus derived from the human visual attention mechanism (HVAM). Locations and shifts of the attention focus are searched and measured using the HVAM model. The descriptors of attention focus are extracted based on their characteristic scale levels. The model of characteristic similarity degree is constructed on the descriptor, which can quantitatively evaluate the degree of amalgamation of target and surrounding background in brightness, color and space distribution. The relation between characteristic similarity degree and target detection probability is given. Applications show that this model has advantages such as high determinability and operability.

    Fast Iterative Thresholding Algorithm Based on Improved Two-Dimensional Minimum Cross Entropy
    WU Yi-quan1;2, FAN Jun1, ZHOU Huai-chun2
    2011, 29(5):  487-494.  doi:10.3969/j.issn.0255-8297.2011.05.008
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    The existing two-dimensional cross entropy thresholding method based on gray level-average gray level histogram does not produce accurate enough results. In addition, it needs to search the entire solution space to obtain the best threshold. In this paper, a fast iterative algorithm based on gray level-gradient cooccurrence matrix is proposed for selecting two-dimensional minimum cross-entropy threshold. The algorithmic formulas are derived. Experiments are carried out on typical test images. Comparisons of segmentation results and execution speed are made between the proposed method and the method based on gray level-average gray level 2D histogram. The results show that the proposed algorithm provides better segmentation. Only a small part of the solution space needs to be searched to find the best threshold. The running time reduces to about 5% of the method based on gray level-average gray level 2D histogram.

    Compressed Sensing Reconstruction for Satellite Cloud Images Using Residual Estimation
    JIN Wei, FU Ran-di, YE Ming, CEN Xiong-ying, YIN Cao-qian
    2011, 29(5):  495-499.  doi:10.3969/j.issn.0255-8297.2011.05.009
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    Since the amount of data in satellite cloud images is huge, acquisition, transmission, and storage of satellite cloud images are costly. To reduce the amount of data, compressed sensing (CS) reconstruction for satellite cloud images is presented based on residual estimation. An aliasing-free directional multi-scale transform (AFDMT) is proposed and applied to the sparse representation of CS. With a random projection technique, the projected Landweber algorithm with a smoothing operation is introduced into reconstruction of the block-based CS recovery. High quality cloud images can be obtained by estimating the residual between the current cloud image and the previous cloud image. Experimental results show that AFDMT is applicable to the sparse representation of CS. The residual estimation scheme can improve quality of the reconstructed cloud images in terms of visual observation and objective evaluation. For example, at a measurement rate of 0.5, peak signal to noise ratio of the reconstructed image is increased by more than 0.5 dB in average compared with direct reconstruction methods.

    Algorithms of Third-Order Hidden Markov Model and Its Relationship with First-Order Hidden Markov Model
    YE Fei1;2, YI Na1, WANG Yi-fei1
    2011, 29(5):  500-507.  doi:10.3969/j.issn.0255-8297.2011.05.010
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    In order to consider more statistical characteristics, a class of third-order hidden Markov model is proposed. In this model, both state transition and output observation depend on the current state and on the two preceding states as well. Three algorithms of the third-order hidden Markov model are studied and derived, including the forward-backward algorithm for observation sequence evaluation, the Viterbi algorithm for determining the optimal state sequence, and the Baum-Welch algorithm for training the third-order hidden Markov model. A first-order hidden Markov model equivalent to the third-order hidden Markov model is constructed. A theorem of their equivalence is proposed and proved. This study contributes to the algorithmic
    theory of the hidden Markov model, and provides a better method to practical applications.

    Electronic Engineering
    Miniature Rectification Circuit for Microwave Power Transmission
    Lv Yan-qing, YANG Xue-xia, ZHOU Jun
    2011, 29(5):  508-511.  doi:10.3969/j.issn.0255-8297.2011.05.011
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    A miniaturized rectifying circuit using microstrip lines and chip elements is proposed. The circuit is analyzed and designed using ADS2006A software. RF-DC conversion efficiency of 72\% is obtained at 5.8\;GHz with 100\;mW input power. However, the measured efficiency is much lower, which is caused by frequency shift and impedance mismatch of the ideal ADS model. By co-simulation of theory model and practical printed image, we propose inductance compensation to improve conversion efficiency. The measured value reaches 64\% at 5.7\;GHz, near the simulated result. The rectifying circuit is compact in structure and easy to be integrated. It can be used for wireless power transmission in wireless sensor networks and RFID applications.

    Simultaneous Measurement of Conductance and Differential Conductance with Operational Amplifier and Fourier Spectrum Analyzer
    XIAO Wen-bo1;2, HE Xing-dao1;2, LIU Jiang-tao3
    2011, 29(5):  512-515.  doi:10.3969/j.issn.0255-8297.2011.05.012
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    We propose a method to measure conductance and differential conductance simultaneously using an operational amplifier and Fourier spectrum analyzer. Theoretical analysis is conducted to study the output voltage characteristics of a nonlinear diode under AC and DC bias. Assuming that high-frequency contents are much smaller than low-frequency components in that output voltage, a measurement equation for conductance and differential conductance of the diode is derived. And, an analytical expression of the physical relationship is presented. Simulation and experiments show validity of the method. We also find that the differential conductance signal is an order of magnitude stronger than the conductance signal when the diode is under the same DC bias.

    Computer Science and Applications
    Framework for Collaborative Computing Task Distribution,Deployment and Execution over Multiple Virtual Machines
    CHEN Xiao-jun1, ZHANG Jing1;2, LI Jun-huai1
    2011, 29(5):  516-528.  doi:10.3969/j.issn.0255-8297.2011.05.013
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    A framework based on a three-layer structure for collaborative computing task distribution, deployment and execution over multiple virtual machines has been designed to implement transparent design and placement of tasks. The framework simplifies the interaction among processes with implicit communication,and provides a high reliable and fault-tolerant computing environment. Based on the supporting technologies including virtual appliance technology and application virtualization, six key techniques are proposed for the framework design. They are description of executable files packages and their submission methods, automatic distribution and deployment of executable files, the way of starting and loading tasks, status transition of feature units, message communication language, and system fault tolerance approaches. Based on these key techniques, a prototype system has been developed, and its performance tested. The experimental results show that the framework and key techniques can improve the speed of tasks distribution, deployment and execution, and the system throughput. The task speedup rate is therefore increased.

    Generate Safety Property Tests Using Model Checking
    ZENG Hong-wei1, MIAO Huai-kou1;2
    2011, 29(5):  529-536.  doi:10.3969/j.issn.0255-8297.2011.05.014
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    Abstract: Safety-critical systems must satisfy given safety properties. Generally, the method of "verificationthen-testing" does not guarantee that the given safety properties are tested because test generation is independent of given properties. In this paper, we propose to test safety properties based on the input-output labeled transition system. Output mutations are applied to construct the output-complete model of an implementation under test. Test cases are generated by finding out dangerous traces. We give safety property test criteria based on the structural graph coverage, and propose a method to formalize the test criteria. NuSMV is used to
    model check the output-complete model to generate the test cases that are relevant to the given safety property and satisfy the structural coverage.

    Control and System
    Adaptive Reconfigurable Control Allocation for Over-Actuated Actuator Failures
    CHEN Yong, DONG Xin-min, XUE Jian-ping, WANG Fa-wei
    2011, 29(5):  537-544.  doi:10.3969/j.issn.0255-8297.2011.05.015
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     With regard to the coordinated control commands allocation with over-actuated actuator failures,a reconfigurable control allocation scheme is proposed by adaptively modifying fault actuator control weights.A modular flight control system is constructed by introducing a virtual control command. Taking into account the mechanical constraints, the fault actuator model of a multi-effectors aircraft is established. Integrated with multi-objective optimal allocation, the command weight matrix of fault control surfaces is adjusted in the descending direction relative to control objective gradients to ensure adaptive modification of the fault actuators. Simulation results show that the proposed scheme can combine control efficiency of fault control
    surfaces, coordinate the control commands effectively without chattering, and realize control reconfiguration.

    Time-Varying Kalman Filter Estimation for Vision Based Unmanned Aerial Vehicle Formation Flight
    LI Xue-song1, LI Ying-hui1, LI Xia1, WANG Zhi-ke2
    2011, 29(5):  545-550.  doi:10.3969/j.issn.0255-8297.2011.05.016
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     A robust time-varying Kalman filter for a class of multi-input multi-output uncetain system is proposed. This method combines a time-varying Kalman filter with an adaptive neural network. It can overcome nonlinear uncertainty with the adaptive neural network trained by two error signals. The method can improve approaching precision, and the boundedness of the estimation error is proven by the Lyapunov theory. The proposed method is used to design state estimation of leader in the unmanned aerial vehicle(UAV) formation flight. Simulation results show that the method can estimate acceleration of leader flying with uncertain maneuvers. The follower can effectively track the leader. Thus effectiveness of the method is validated.