Table of Content

26 May 2011, Volume 29 Issue 3

Previous Issue    Next Issue

Communication Engineering

Novel Trusted Routing in Wireless Mesh Networks

YANG Kai, MA Jian-feng, YANG Chao

2011, 29(3):  221-227.  doi:10.3969/j.issn.0255-8297.2011.03.001

Asbtract ( 1827 )   PDF (626KB) ( 2190 )  

References | Related Articles | Metrics

Because of the inherent characteristics of wireless mesh networks (WMN), the existing trust models are not applicable. This paper proposes a novel subjective logic based reputation model to detect and isolate malicious nodes in WMN. The model can also differentiate between malicious packet drop and the packet drop due to poor link quality. The model is applied to radio-metric ad hoc on-demand distance vector routing (RMAODV)
to obtain a trusted routing T-AODV. Simulation results show that the proposed scheme can effectively evaluate trustworthiness of nodes, resist attacks to some extent and improve overall reliability, robustness and security of the network.

Cross-Layer Design in Multiuser MIMO-OFDM Systems Based on Space-Time Block Coding for IEEE 802.16

XIE Wei1;2, YU Jiang2

2011, 29(3):  228-232.  doi:10.3969/j.issn.0255-8297.2011.03.002

Asbtract ( 1745 )   PDF (593KB) ( 1334 )  

References | Related Articles | Metrics

Cross-layer design of packet scheduling and adaptive resource allocation in multiuser MIMO-OFDM systems are investigated based on space-time block coding (STBC). Different types of service are grouped into four types according to the 802.16 protocol. A two-layer scheduling architecture is then used to shape traffic at medium access (MAC) layer: the first layer schedule packets for different users of the same service type, and the second for different service types. A resource allocation algorithm is proposed to efficiently allocate wireless resource at physical layer according to the scheduling results of the MAC layer and the channel state information. Simulation results show that the proposed algorithm can achieve significant improvement in packet drop rate, packet delay, and system throughput as compared to an existing method.

Channel Allocation Scheme for Multiuser Cooperative Networks

HAN Ling-juan, ZHANG Si-hai, ZHOU Wu-yang

2011, 29(3):  233-237.  doi:10.3969/j.issn.0255-8297.2011.03.003

Asbtract ( 1757 )   PDF (654KB) ( 1883 )  

References | Related Articles | Metrics

 We study the channel allocation scheme for cooperation network with the aim of improving system throughput in addition to meeting QoS requirements. A suboptimal heuristic algorithm is proposed and implemented by using virtual nodes. The method simplifies joint channel allocation and cooperation by considering direct transmissions only. The proposed algorithm achieves adaptive allocation. Simulation results indicate
that the proposed algorithm significantly outperforms previous works in terms of system throughput and QoS.

Design of Multi-element Transmitting Antenna for Indoor Visible Light Communication

DING De-qiang, KE Xi-zheng, LI Jian-xun

2011, 29(3):  238-242.  doi:10.3969/j.issn.0255-8297.2011.03.004

Asbtract ( 1570 )   PDF (894KB) ( 1604 )  

References | Related Articles | Metrics

 A multi-element transmitting antenna composed of white LEDs based on a new white LED radiation model is designed. Effects of parameters used in the design on the distribution of received indoor power are studied, including element layout, LED optical axis polar angle, layer distance, and number of elements. Based on simulation, reasonable design parameters of the transmitting antenna are presented. By controlling
transmitted power of the LED, a design method for transmitting antenna with flat-top distribution of received power is obtained. Simulation and experiments verify the new white LED radiation model.

Achievable Secrecy Rate of Multiple-Level Relay-Eavesdropper Channel

CHEN Ying, WANG Bao-yun

2011, 29(3):  243-250.  doi:10.3969/j.issn.0255-8297.2011.03.005

Asbtract ( 1672 )   PDF (600KB) ( 1843 )  

Related Articles | Metrics

Security of a multiple-level relay-eavesdropper channel is studied, and the rate-equivocation region and achievable secrecy rate are derived in a discrete memoryless channel and a Gaussian channel, respectively. In particular, we analyze the achievable secrecy rate in two-level relay-eavesdropper and one relay-eavesdropper channels in the Gaussian channel under a limited power, and compare their achievable secrecy rate by simulation. The results show that a higher achievable secrecy rate is achieved in the multiple-level relay-eavesdropper channel when the relay node is far away from the source node. Therefore, security of the multiple-level relayeavesdropper channel is generally better.

Downlink Pre-coding for Multi-user MIMO System with Successive Iterative Optimal SLNR

GAO Xian-kun, CUI Yan, FU Hong-liang

2011, 29(3):  251-255.  doi:10.3969/j.issn.0255-8297.2011.03.016

Asbtract ( 2262 )   PDF (666KB) ( 1428 )  

Related Articles | Metrics

In the downlink of a multi-user MIMO system, an appropriate pre-coding algorithm is needed to suppress co-channel interference. Based on the criterion of maximum signal-to-leakage-and-noise-ratio (SLNR), a successive iterative optimization pre-coding scheme is proposed. The method uses the unused subspace of known users to improve the space degree-of-freedom of the other users, and reduces the leakage. An iterative optimal method is applied to further suppress multi-user interference (MUI) and improve the signal-to-interference-and-noise-ratio (SINR) at the receiver. The proposed scheme only makes use of the channel information of the users at the transmitter to optimize the pre-coding matrix without collaboration between the base stations and the users. Any detection algorithm can be selected at the receiver without increasing the system overhead. Simulation results show that the proposed scheme has better performance and faster convergence than the original SLNR algorithm, and therefore is suitable for practical applications.

Signal and Information Processing

Classification of FSK/PSK Hybrid Modulation Radar Signals

CHI Wen-jing, CHEN Jian, KUO Yong-hong

2011, 29(3):  256-260.  doi:10.3969/j.issn.0255-8297.2011.03.007

Asbtract ( 2080 )   PDF (626KB) ( 1621 )  

Related Articles | Metrics

Classification of FSK/PSK signals is studied in accordance with the characteristics of hybrid modulation signals that have low interception probability. Attention is focused on the identification of FSK/PSK, PSK and FSK signals using binary trees. The amplitude and phase related characteristic statistics are sent to the classifier to achieve classification. Simulation results show that the method is effective. The correct classification rate of FSK/PSK hybrid modulation signal is no less than 99% at 5 dB SNR.

Direction Finding for Coherent Signals Based on Vector Reconstruction

DIAO Ming, AN Chun-lian

2011, 29(3):  261-266.  doi:10.3969/j.issn.0255-8297.2011.03.008

Asbtract ( 1854 )   PDF (749KB) ( 1332 )  

Related Articles | Metrics

The classical direction of arrival (DOA) estimation algorithms for coherent signals are mainly based on the spatial smoothing method and the subspace fitting algorithm. These methods suffer from small array aperture or heavy computation load. It is important to find a method for coherent signals with a large array aperture and small computation load. In this paper, a new method is proposed based on the vector reconstruction technique for coherent signals using the total least square-estimation of signal parameters via rotational invariance technique (TLS-ESPRIT) algorithm. The proposed method exploits all eigenvectors corresponding to the signal subspace and the forward-backward vector reconstruction technique to construct the receiving data matrix. The method is effective when both independent and coherent signals are incident on the array, and useful in practical signal environment. Theoretical analysis and simulation results show that the proposed method has low computation load, large array aperture and satisfactory estimation performance.

Low Complexity Joint Iterative Equalization and Decoding Scheme for Sparse Underwater Communication Channel

MENG Qing-wei, HUANG Jian-guo, HE Cheng-bing

2011, 29(3):  267-273.  doi:10.3969/j.issn.0255-8297.2011.03.009

Asbtract ( 1627 )   PDF (1498KB) ( 1846 )  

Related Articles | Metrics

Long-range communications in shallow water faces great challenges of severe multipath interference, fading, and low SNR. The traditional second-order digital phase lock loop (DPLL) embedded decision feedback equalizer can only work at high SNR, serious error propagation may occur at low and moderate SNR. In order to improve reliability of long-range shallow water communications, a low complexity joint iterative equalization and decoding (LC-JIED) scheme is proposed for sparse underwater communication channel. The method compensates for Doppler shifts using an embedded second-order DPLL, and updates the equalizer coefficients by taking into account sparsity of the channel. System performance is greatly improved by iteratively exchanging soft information between the equalizer and decoder. Simulations based on real lake channel profiles show that
the proposed method is effective for sparse underwater channel. It can significantly improve reliability of longrange shallow water acoustic communications by exchanging soft information between equalizer and decoder at low to moderate SNR.

Improved Method of Adaptive Distance Preserving Level Set Evolution

ZHOU Lin, PING Xi-jian, TONG Li

2011, 29(3):  274-280.  doi:10.3969/j.issn.0255-8297.2011.03.010

Asbtract ( 1708 )   PDF (946KB) ( 1708 )  

Related Articles | Metrics

In this paper, an improved method of adaptive distance preserving level set evolution is proposed. A weighting coefficient depending on information in the image and a stop function are defined. The evolution curve is no longer sensitive to the position of the initial curve, which can be anywhere in the image. The curve of zero level set can detect object boundaries when it is in a region with pixels having the same gray value. The method enhances capability of detecting boundary concavities. Experiments on images with different object boundaries show that the proposed method can detect the object contour effectively and has strong anti-noise ability.

Print-Scan Resilient Watermarking Based on Digital Hologram and Distortion Correction

HUANG Su-juan1;2, WANG Du-yao1;2, REN Yan-li2

2011, 29(3):  281-288.  doi:10.3969/j.issn.0255-8297.2011.03.011

Asbtract ( 2021 )   PDF (22674KB) ( 2098 )  

Related Articles | Metrics

This paper presents a novel print-scan resilient watermarking algorithm based on digital hologram and correction of distortion. A hologram of the watermark is obtained and embedded into the spectral magnitude of the host image. A PSNR threshold adapted to the texture of the host image is set to adjust the watermark strength. The rotation distortion due to the print-scan process is corrected based on discrete Fourier transform (DFT) and edge detection. The method makes use of the digital hologram characteristics, and is capable of extracting the embedded watermark from a print-scan version reliably. Compared with previous similar schemes, the proposed approach shows advantages in invisibility, robustness and embedding capacity.

Detecting Onset and Offset of QRS Complex Based on Measurement of a Triangle

HU Xiao, WANG Jia-qing, ZHANG Ni

2011, 29(3):  289-293.  doi:10.3969/j.issn.0255-8297.2011.03.012

Asbtract ( 1650 )   PDF (4712KB) ( 1840 )  

Related Articles | Metrics

 An algorithm is proposed to detect onset and offset of QRS complex. Given a sequence of ECG signal samples, a triangle is formed by the current sample together with the sample before the previous one, and that after the following one. The interior angle corresponding to the vertex (the current sample), and the distance from the current sample to the opposite side of the triangle are calculated. If both the interior angle and the distance satisfy the pre-determined values, the current sample is judged as a Q, R or S peak. The onset and offset of QRS complex are thus found among the samples preceding and following QRS complex according to their interior angles. A total of 24 multichannel ECG records obtained from the Internet are used to test the proposed method. The experimental results show that the proposed method can accurately detect onset and offset of QRS complex, and the morphological feature of ST segment is effectively kept after its baseline wander is extracted from the ECG signal with the method.

Evaluation of Camouflage Effectiveness Using Human Visual Attention Mechanism

JIA Qi, Lü Xu-liang, WU Chao, TANG Hou-chao

2011, 29(3):  294-298.  doi:10.3969/j.issn.0255-8297.2011.03.013

Asbtract ( 1778 )   PDF (1351KB) ( 2009 )  

Related Articles | Metrics

 In order to evaluate target camouflage effectiveness objectively, precisely and conveniently, we establish a model based on the human visual attention mechanism. A conspicuity map is obtained based on intensity of the input image, orientation characteristics and chromatic aberration. Shift of the focus of attention (FOA) is selected and measured with the mechanisms of winner-take-all (WTA) and inhibition of return. The relation between the FOA shift and target detection probability is obtained using a BP neural network. Target camouflage effectiveness can be measured precisely. Experiments are performed on 44 images of southern forest for training the BP neural network and validating the model. The results show that this
model has advantages in precision, determinability and operability.

Depth Map Coding Oriented to Virtual View Synthesis in FTV System

ZHANG Qiu-wen1, AN Ping1;2, ZHANG Yan1;3, ZHANG Zhao-yang1;2

2011, 29(3):  299-307.  doi:10.3969/j.issn.0255-8297.2011.03.014

Asbtract ( 3517 )   PDF (5978KB) ( 2641 )  

Related Articles | Metrics

A depth map compression method oriented to virtual view rendering is proposed to reduce distortion of virtual view synthesis in a free-viewpoint television (FTV) system. The distortion is caused by quantization of depth data and inaccuracy of depth estimation algorithm. According to the statistics of depth data, a depth down/up sampling techniques based on the non-uniform B-spline curve is proposed. The depth map is down-sampled and coded with MVC. In the de-coding side, the depth map is up-sampled. To deal with the serration phenomenon in edges of the decoded depth image, a bilateral filtering is used to align the object boundaries. The experimental results evaluated by objective and subjective methods indicate that the proposed method can reduce bit-rate of depth coding and achieve better rendering quality. It can improve high-accurate reconstruction of synthesized images at the receiver of FTV systems.

Opposition-Based Differential Evolution Using the Current Optimum for Function Optimization

XU Qing-zheng1;2, WANG Lei1, HE Bao-min1, WANG Na2

2011, 29(3):  308-315. 

Asbtract ( 1729 )   PDF (664KB) ( 2070 )  

Related Articles | Metrics

When the global optimum is not located at the geometric center of the domain, the opposite numbers may lapse from the global optimum, leading to poor performance of opposition-based differential evolution. A novel opposition-based learning strategy using the current optimum is introduced, and it is combined with differential evolution for function optimization. The optimum in the current generation is served as a symmetry point between an estimate and the corresponding opposite estimate, resulting in a high rate of opposite population usage. Experiments results clearly show that the proposed algorithm can significantly improve the performance due to the opposite numbers. Additionally, an enhanced version of opposition-based
differential evolution is proposed to reveal ideal and perfect results using opposition-based learning.

Control and System

Robust Quadratic Stabilization H1 Control for a Class of Linear Switched Systems with Multiple Time-Varying Delays in State
and Input

2011, 29(3):  316-324.  doi:10.3969/j.issn.0255-8297.2011.03.016

Asbtract ( 2071 )   PDF (637KB) ( 1297 )  

Related Articles | Metrics

This paper addresses the problem of robust quadratic stabilization H∞control for a class of linear switched systems with uncertain multiple time-varying delays in state and input based on LMI and H∞theory. Based on multiple Lyapunov function techniques and by constructing linear matrix inequalities, several sufficient conditions for the problem to be solvable are derived by using a state-based switching law. Meanwhile,
robust H∞controllers for each subsystem and switching law are designed. A numerical example shows effectiveness of the method.

Minimum Entropy Generation Analysis of Aircraft Environmental Control System

LI Hong-bo1, DONG Xin-min1, LI Ting-ting2, GUO Jun1

2011, 29(3):  325-330.  doi:10.3969/j.issn.0255-8297.2011.03.017

Asbtract ( 2489 )   PDF (2704KB) ( 1375 )  

Related Articles | Metrics

 Based on the second law of thermodynamics, minimum entropy generation analysis of aircraft environmental control is conducted using the multi-objective optimization method. To design takeoff, climb and supersonic cruise, and take entropy generation minimum as the objective function, an optimization model is established. In the optimization computation, influences of flow ratio of heat exchanger, mass flow of bleed air, pressure ratio of compressor and turbine on system entropy generation during different flight phases are analyzed. To overcome the conflict between design variables during different phases, a multi-objective optimization model is established with minimum entropy generations as different objective functions at the
design points. The Pareto optimal set is obtained using the NSGA-II algorithm, leading to an optimal scheme. Simulation shows validity of the proposed method.