Table of Content

23 March 2011, Volume 29 Issue 2

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Communication Engineering

Analysis and Improvement of Opportunistic Routing over Wireless Mesh Networks

WU Hai-sheng, WANG Gui-jin, LIN Xing-gang

2011, 29(2):  111-117.  doi:10.3969/j.issn.0255-8297.2011.02.001

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Opportunistic routing (OR) has attracted increasing attentions, and several practical protocols over wireless mesh networks (WMNs) have been proposed. Opportunistic routing protocols usually use a fixed rate to send data packet and end-to-end acknowledgement to ensure reliability, which cause congestions and duplicated retransmissions in the networks. In this paper, we propose a built-in rate control mechanism in opportunistic routing to avoid performance degradation due to network congestion. It takes full consideration of the wireless link quality and the non-deterministic multi-path characteristics of opportunistic routing. We also introduce a round-Robin packet sending fashion to reduce unnecessary retransmissions and improve throughput. Simulations show that the modified protocol significantly outperforms the state-of-the-art opportunistic routing protocol, MORE, in both single and multiple flow scenarios.

Optimization of Online Measurement in Wireless Mesh Networks

HU Zhi-yuan, HU Song-hua, BO Song, HUANG Dong

2011, 29(2):  118-123.  doi:10.3969/j.issn.0255-8297.2011.02.002

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Accurate and real-time measurement of network characteristic is essential to optimize performance of wireless mesh networks. We present architecture for online measurement of wireless mesh networks, and address the problem of location selection of measurement nodes. In order to obtain the best location of measurement nodes, an ellipse secant algorithm is developed, which combine the signal detection capability
with the transmission capability. The optimized location of measurement nodes is selected inside a set of ellipses with the measured node and data centers respectively as the focus. Simulation results show that the online measurement architecture can achieve best tradeoff between signal detection capability and transmission capacity, and guarantee the quality of online measurement. The ellipse secant algorithm has computational
complexity lower than the random selection algorithm.

Traffic Prediction-Based Adaptive Congestion Control Routing Protocol for WSN

YANG Jun-gang1, SHI Hao-shan1, DUAN Ai-yuan2, ZHANG Long-mei1

2011, 29(2):  124-128.  doi:10.3969/j.issn.0255-8297.2011.02.003

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Based on Ad Hoc on-demand distance vector (AODV), a routing protocol of WSN is proposed, called adaptive congestion control routing protocol based on traffic prediction (AccRPbTP). Using a time series prediction algorithm, AccRPbTP obtains the prediction value of future networks traffic, and estimates congestion level. Thus, adaptive control to route is achieved by taking diverted route in advance. NS2 experiment results show that AccRPbTP effectively improve the networks performances, especially in network congestion and load balance.

Performance of Two-Hop Multi-point Cooperative Relay Communication Systems

PENG Yu-xu, TANG Zhou-jin

2011, 29(2):  129-132.  doi:10.3969/j.issn.0255-8297.2011.02.004

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The paper studies performance of multi-point relaying cooperative communication system using selection decode-and-forward relays over an independent and identically distributed Rayleigh fading channel. Closed-form expressions of average symbol error rate (SER) and outage probability (OP) in Rayleigh fading channels are derived using moment generating function (MGF) and hyper-geometric function. Compared with
the traditional cooperative communication system, performance of two-hop multi-point cooperative relayingcommunication systems is better.

Signal and Information Processing

Detection of Weak Signals Generated by Surface Plasmon Resonance Biomedical Sensors Using Photodiode-Array Device

WANG Cheng, ZHANG Wei, ZHAO Zi-chun, LIU Guo-hua

2011, 29(2):  133-139.  doi:10.3969/j.issn.0255-8297.2011.02.005

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This paper proposes an efficient de-noising method using a photodiode-array device to improve detection capability of surface plasmon resonance (SPR) sensors. Using reference noise signals output from the photodiode-array, we combine the coherence de-noising technique and the wavelet de-noising using soft threshold so as to raise the output SNR from 40 dB to over 52 dB. Experiments of human immunoglobulin G (IgG) molecules specific combinations show that the proposed de-noising method can remarkably enhance resolution of SPR sensors. Using this method, the SPR sensor can quantitatively detect tiny change of IgG molecule contents in solution samples with an order of 10?3 mg/mL, showing an improvement of more than one order of magnitude in detection accuracy and resolution.

High-Capacity Text Watermarking Resistive to Print-Scan Process

GUO Cheng-qing1;2, XU Guo-ai1;2, NIU Xin-xin1;2, LI Yang1;2

2011, 29(2):  140-146.  doi:10.3969/j.issn.0255-8297.2011.02.006

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 Based on an analysis of the existing text watermarking techniques, a high-capacity text watermarking scheme resistive to print-and-scan processes is proposed. The binary document image is first segmented into individual characters. A multi-bit watermark is then embedded by flipping the boundary pixels of each character based on a print-scan invariant quantity and complexity of the character. A quantitative model is established to achieve the character pixel quantization, which can minimize visual distortion. Experimental results show that the proposed scheme can increase embedding capacity. It can effectively resist print-scan attacks so as to watermark hardcopy documents.

Vehicle License Plate Location Based on Machine Learning

ZHANG Pin-zheng, WANG Jian-hong

2011, 29(2):  147-152.  doi:10.3969/j.issn.0255-8297.2011.02.007

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This paper proposes a vehicle license plate locating method based on the Adaboost algorithm and smallest univalue segment assimilating nucleus(SUSAN) corner validation. The Adaboost algorithm is applied for initial classification in order to select target license plate region and reduce the number of candidate areas. SUSAN corner validation is then used to calculate and sort probability of each area belonging to the vehicle
license. The area with the highest probability is taken as the detection result. Experimental results show that the proposed method is robust to different illumination conditions, and the preset parameters produce satisfactory results in different experiments.

Image Retrieval Based on Homology Continuity in Multi-dimensional Space

LIU Pei-zhong1;3, WANG Shou-jue1;2

2011, 29(2):  153-158.  doi:10.3969/j.issn.0255-8297.2011.02.008

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Continuity exists when an object identifiable by computer changes from one state to another.We propose a similarity metric by combining homology continuity and biomimetic distance based on multidimensional space biomimetic informatics (MDSBI) to achieve efficient image retrieval. Experiments on the COREL image database show that the proposed method can effectively improve the image retrieval efficiency.

Fusion Strategy of Multi-scale Image Decomposition Combined with Image Quality Evaluation

PAN Yu, WANG Jing, SUN Quan-sen, XIA De-shen

2011, 29(2):  159-168.  doi:10.3969/j.issn.0255-8297.2011.02.009

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The fusion strategy of multi-scale image decomposition is the key point to improve the image fusion. To make full use of the information in the progress of multi-scale image decomposition, an image fusion strategy combined with image quality evaluation is proposed. This strategy includes two parts: first, the salient feature in the last level instead of current level is used to construct the weight which is necessary for the fusion of current level’s approximation images; second, the parameters of the image quality measurement such as spatial frequency and contrast are introduced for the fusion of detail images. The experiment demonstrates that, compared with current common fusion rules, the proposed fusion strategy has improved the quality of the fused image in subjective aspect as well in objective aspect.

Blind Separation of Single Channel Permuted Image Based on Double Blur Correlation

WANG Wei1, FANG Yong1;2

2011, 29(2):  169-175.  doi:10.3969/j.issn.0255-8297.2011.02.010

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This paper proposes a single-channel blind separation scheme using double blur correlation for blurring permuted images. The permuted image is blurred again and the correlation coefficients of image blocks are estimated before and after double blurring. Using the estimated correlation coefficients, a mapping space is constructed. The permutation mixing matrixes can be accurately estimated by classifying the parameters in
the mapping space, thus the source images can be separated. Simulation results show high detection accuracy for permuted images with various blurring operations. The proposed method has good robustness against Gaussian noise and lossy JPEG compression.

Statistical Characteristics and Resolution Probability of Rank Reduction Spatial Spectrum in the Presence of Unexpectant Model Errors

WANG Ding, WU Ying

2011, 29(2):  176-186.  doi:10.3969/j.issn.0255-8297.2011.02.011

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 Rank reduction estimator (RARE) can provide direction-of-arrival (DOA) estimation without knowing the (expectant) array model errors, and avoid iterative computation and local convergence. However, RARE requires the array errors model, and its angle resolution performance is affected by unexpectant model errors in practice. We analyze the angle resolution performance of RARE. The second-order error representation and statistical properties of the perturbed RARE spatial spectrum are obtained based on the derivation of three types of angle resolution probability. The theoretical analysis is validated in the numerical experiment aimed at RARE for mutual coupling self-calibration of uniform array, and direction-dependent amplitude-phase errors self-calibration.

Joint 2D Angle and Frequency Estimation Based on Uniform Square Array

XU Ling-yun1;2, ZHANG Xiao-fei1, XU Zong-ze1

2011, 29(2):  187-194.  doi:10.3969/j.issn.0255-8297.2011.02.012

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A novel joint two-dimensional angle and frequency estimation method based on a uniform square array is presented. The output signal of the antenna array is analyzed, showing quadrilinear model characteristics. The source parameters can be estimated from the matrices via low-rank decomposition based on uniqueness of PARAFAC decomposition. The algorithm first uses the quadrilinear alternating least square (QALS) algorithm to estimate the direction and frequency matrices. It then estimates frequencies according to Vandermonde characteristics of frequency matrix and least square principle. DOAs are estimated from the characteristics of direction matrix and the least square principle. The method does not need to search spectral
peaks or parameter pairs. Compared with ESPRIT and the trilinear model, the proposed algorithm has high precision in parameter estimation, and works well with small sizes. Simulation results verify its effectiveness.

Single Channel Blind Source Separation of Digital Mixtures Using Particle Filtering and Support Vector Machine

LUAN Hai-yan1, JIANG Hua1, LIU Xiao-bao2

2011, 29(2):  195-202.  doi:10.3969/j.issn.0255-8297.2011.02.013

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 To reduce computation complexity in the particle-filtering based blind source separation, a novel eparation algorithm of co-frequency digital modulated mixture is proposed, which combines the particle filtering lgorithm with support vector machine. Formulae for assigning particle weights and expression for stimating a posterior distribution function are derived. Performance of the proposed algorithm is analyzed in wo aspects: statistic characteristics of the estimated posterior density function and its computation complexity. he estimated posterior density function is shown to be close to the true function. Both the theoretical nalysis and simulation results show that the proposed algorithm can reduce processing time without loss of
performance in terms of bit error probability as compared with the particle-filtering based blind source separation lgorithm.

The Accelerated ?-Leap Simulation Method for Biochemical Reaction Systems

YI Na, ZHUANG Gang, WANG Yi-fei

2011, 29(2):  203-208.  doi:10.3969/j.issn.0255-8297.2011.02.014

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This paper redefines critical reaction. It is more reasonable to demarcate reactions which may have negative reactants. Based on the definition, the accelerated ? -leap algorithm is proposed. Even if the number of some species in biochemical systems is small, the ? -leap algorithm is adaptive. This algorithm also increases the speed of simulation. The accurate stochastic simulation algorithm (SSA) algorithm, an improved ? -leap algorithm and the present accelerated algorithm are compared in two biochemical reaction models. Numerical results demonstrate that the proposed method is faster under the same simulation precision.

Control and System

Subspace Identification in Time-Domain for Fractional Order Systems Based on Short Memory Principle

LIAO Zeng, PENG Cheng, WANG Yong

2011, 29(2):  209-215.  doi:10.3969/j.issn.0255-8297.2011.02.015

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 A subspace identification algorithm in the time-domain based on short memory principle is given for multivariable fractional order systems. This algorithm can effectively identify the coefficient matrixes and the fractional differential order of multivariable fractional order systems. Utilizing the Poisson moment functionals (PMF), input and output signals are filtered, and the basic input and output data matrixes in subspace method constructed. The problem of identifying fractional differential order is transformed into a parameter optimization problem according to the cost function. Using the short memory principle of fractional differentiation, the fractional differential order is separated from input and output data matrixes, and differentiation calculation of input and output signals is avoided. A numerical example is given to validate the proposed algorithm.

Active Vibration Control Based on Online Real-Time Identification of Control Channel

HUANG Quan-zhen, ZHU Xiao-jin, GAO Shou-wei, GAO Zhi-yuan, SHAO Yong

2011, 29(2):  216-220.  doi:10.3969/j.issn.0255-8297.2011.02.016

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 In view of the limitation of practicality and applicability of generally used offline identification, we propose an active vibration control algorithm based on online control channel real-time identification by analyzing the basic control structure and identification strategy. We introduce random noise at the control output and achieve real-time online identification for the control channel using an FIR filter. A filtered-X algorithm is employed for the control. The controller architecture and algorithm process is illustrated. Experiments are performed on the active vibration control platform to assess the identification results. The results show that the proposed control algorithm is feasible and effective.