Table of Content

30 November 2007, Volume 25 Issue 6

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Articles

User Scheduling and Power Allocation for Downlink of MIMO Systems with Limited Feedback

ZHONG Chong-xian;YANG Lu-xi

2007, 25(6):  551-551 . 

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Abstract: User scheduling and power allocation are investigated for the downlink of MIMO systems with limited feedback. Corresponding algorithms are proposed based on the idea of opportunistic multiple beamforming. The proposed algorithm feeds the first and the second maximum SINRs of each user and indices of the corresponding beamforming back to the base station only. Simulations show that, compared with previous methods, it can better acquire tradeoff between feedback overhead and total throughput. The proposed power allocation algorithm makes full use of the partial channel state information. Numerical results show that this method can obtain higher throughput under the constraint of available transmit power compared to conventional methods. When the proposed user scheduling and power allocation algorithms are combined, better performance can be obtained without increasing feedback overhead.


Security LEACH Routing Protocol Based on Attack Detection

WANG Jiang-tao;YANG Geng SUN Yuan;CHEN Sheng-shou

2007, 25(6):  557-557 . 

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In this paper we propose a security LEACH (S-LAECH) protocol based on attack detection. According to the characteristics of LEACH routing protocol, this method keeps test parameters at the end of package in the periods of head node selection and data transmission. Thus, judgment of HELLO flood attack and Sybil attack of sensor network is jointly made according to the node power and received signal strength. At the same time, aiming at attacks of cluster head nodes and cluster member nodes, two detecting methods are used to improve accuracy. Jakes channel model in a WSN real network space is established with NS-2 software. Using this model, security of S-LAECH is verified.

Influence of Feedback Delay on The Performance of Multi-user System

SUN Huan;WANG Xin-yu;WANG Yan;YOU Xiao-hu

2007, 25(6):  564-564 . 

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The influence of feedback delay of user channel information on the multi-user system performance is investigated. Analytical results of average sum-rate capacity, outage probability and system bit error rate are derived. Both the theoretical results and the Monte Carlo simulations show that over the time-varying channel, the feedback delay of system does heavily affect the system performance.

ICI Cancellation in UWB-OFDM Systems Based on ICI Matrix Properties

QI Li-na;GAN Zong-liang;ZHU Hong-bo

2007, 25(6):  570-570 . 

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This paper studies the cancellation methods of ICI in UWB-OFDM systems. The mechanism of ICI is analyzed. A novel method of ICI cancellation based on ICI matrix properties is then proposed. Simulation results based on IEEE UWB channel models CM1 and CM4 show that, with the proposed ICI cancellation method, complexity of calculation can effectively be reduced with better performance over different UWB indoor channel environments and normalized different frequency shifts.

Capacity Based Selection of Transmitting Antenna in Multi-user MIMO Systems

MA Yue-huai;CAI Yue-ming;XU You-yun

2007, 25(6):  577-577 . 

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Based on the multiuser MIMO uplink capacity and optimal antenna selection schemes, a sub-optimal transmitting antenna selection algorithm is proposed, termed Multiuser Iterative Elimination Antenna Selection (MIEAS). Simulation results show that, when apply to the uplink of MIMO systems, MIEAS provides performance that is very close to the optimal algorithm in capacity, with considerably lowered computation complexity.

Power Spectrum Density Analysis on AM Broadcasting Using Hybrid Modulation

QI Chen-hao;WU Le-nan

2007, 25(6):  583-583 . 

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Power spectrum density (PSD) analysis for hybrid modulated signal is presented in the paper. The system, which combines extended binary phase shift keying (EBPSK) with double sideband amplitude modulation (DSB-AM), is introduced, and its waveform expression given. With regard to FCC’s(federal communications commission) AM spectral emission mask and China’s national standards on AM transmitter, comparisons are made on the effects of taking different band-pass filters into the hybrid system, and on the demodulation performances. Computer simulations demonstrate that good performance of both modulations can be obtained at certain SNR within the given PSD constraint.

A Rate-Two Full Diversity Space-Time-Frequency Block Code (STFBC) for 4-Tx MIMO-OFDM Systems

MA Qing-hua;YANG Lu-xi;HE Zhen-ya

2007, 25(6):  589-589 . 

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To get full diversity available in the MIMO-OFDM systems with frequency selective quasi-static block fading, the algebraic space-time coding and Hadamard transform are utilized to get a new space-time-frequency block coding (STFBC) to get full diversity. The full diversity is a product of the number of the transmit antenna Mt, receiver antenna Mr and channel taps L in a quasi-static block fading channel. When there are 4 transmitting antennas, the proposed STFBC can reach symbol transmission rate of two. Compared with other STFCs, it makes a good tradeoff between rate-one STFC and rate-four STFC in 4-transmitter MIMO-OFDM systems. Simulation results show validity of our technique.

Passive and Impulsive Synchronization of Complex Networks with Coupling Delays

FAN Chun-xia;JIANG Guo-ping;CHENG Yan-yun

2007, 25(6):  594-594 . 

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An impulsive synchronization controller is presented for complex networks with coupling delays using impulsive control for time-delayed systems. The impulsive controller, which is capable of quickly synchronizing complex networks, is addressed with a passive method. Numerical simulation is carried out in which the complex network having 10 nodes is used as an example. The results show that the presented synchronization controller can synchronize complex networks with coupling delays asymptotically.

Joint Iterative Decoding and Noise Variance Estimation

PAN Xiao-fei;LIU Ai-jun;ZHANG Bang-ning;WANG Hang-xian

2007, 25(6):  598-598 . 

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Effects of noise variance estimation on the LDPC decoding performance are investigated. Based on the algorithm of expectation-maximization (EM), a noise variance estimation method is obtained.The method is applied to the BP decoding algorithm . Simulations show that, with the proposed method, the observed performance degradation is less than 0.1dB when the noise variance is unknown.

Estimation of Non-Gaussian Noise Parameters Using Markov Chain Monte Carlo Method

ZHANG Shu-Xia;JIANG Yu-Zhong;XU Da-yong

2007, 25(6):  603-603 . 

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A fast convergence Bayesian estimator of the class A model parameters is derived and calculated using the Markov Chain Monte Carlo (MCMC) procedure. This estimator can estimate the impulsive index, Gauss-to-impulsive power ratio, noise power, and hidden states of class A noise model for the channel simultaneously. The considered estimator is different from traditional estimator, which provides a novel method with low-complexity, global optimization capability and potential for parallel processing. Simulation with small sample sizes shows effectiveness of the technique.

Multi-resolution Elastic Registration Using Edge Contour Featrues

RONG Cheng-cheng;ZHOU Jian;CAO Guo-gang;LUO Li-min

2007, 25(6):  608-608 . 

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A multi-resolution elastic registration method based on edge contour is presented. The C-V（Chan-Vese） model is applied to extract source and target contours from two human brain MR images. A multi-resolution simulated annealing procedure is proposed to match the two contour point sets with low computation cost. This way, a fast elastic registration method using B-spline interpolation function is obtained. Experimental results show that the proposed method provides fast image registration without loss of precision.

Segmentation of Serial Images Based on Active Contour Model

TAO Ling;QIAN Zhi-yu;CHEN Chun-xiao

2007, 25(6):  615-615 . 

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An improved active contour model is presented for segmentation of medical image sequences. A restriction is applied to an internal energy function to make the length of contour as short as possible so as to prevent contour from converging at sharper points of other tissue on perpendicular bisector. An external energy function is constructed from the information pertinence of local region between the serial images to eliminate the interference of texture and capture corner points completely. Experimental results show that the improved algorithm can give better segmentation, which can detect any corner points and concave points, and avoid object edge converging at pseudo edge points.

Test of Software Component Using Data Flow Testing

ZENG Hong-wei;ZHOU Jian-yun

2007, 25(6):  621-621 . 

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Component state machine (CSM) is used to model the behavior of component under test. We design an algorithm transforming CSM into a component flow graph that describes control and data flows among states, transitions, and guards of transitions in the CSM. We then propose a data flow graph-based approach to test component. The du-path set of a component flow graph can be generated automatically according to all-use criterion for data flow testing.

Error Correction in 3D Reconstruction System Using Single Image

JIN Shi-qun;ZHANG Li;FAN Li-qin

2007, 25(6):  627-627 . 

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A novel calibration and lens distortion correction of 3D reconstruction systems is introduced in this paper. Assuming zero distortion at the center of image, the parameter calibration and lens distortion correction of the CCD camera and the DLP projector is separated with the center points and all the rest points in the field. Furthermore, identification and correspondence of the interested points are automatically done because of the design target with standard circles and multicolor code of pseudo-random array during calibration. Experiments show that the proposed method is fast and convenient in the calibration of lens distortion.

Robust Adaptive Control of Neural Dynamic Surface for Supermaneuverable Flight

Zhou Li;Jiang Chang-sheng

2007, 25(6):  632-632 . 

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An approach to neural network-based robust and adaptive dynamic surface control is proposed for supermaneuverable flight with violent changes of aero-dynamics parameters. To achieve high precision, a radical basis function neural network (RBFNN) is used to compensate for parameter uncertainties and unknown disturbance. Control laws are obtained from dynamic surface control which reduces the complexity of backstepping controller. In addition, adaptive tuning rules of neural network weights are improved to achieve good performance of transient processes. Stability analysis using the Lyapunov stability theorem shows that all closed-loop signals are bounded. Output tracking error and approximate error of neural network weights exponentially converge to small compacts. Finally, results of the Herbst maneuver simulation show that the designed control systems have good performance under stall conditions.

Flow Fields and Thermal Comfort in Training-Plane’s Air-Conditioned Cockpit

XIONG Xian -peng;LIU Wei-hua;ANG Hai-song;Gao Xiu-feng;Wei Jin-jia

2007, 25(6):  639-639 . 

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Numerical simulation is carried out to study the flow field and thermal fields inside a training-plane’s air-conditioned cockpit under different air inlet conditions. Effects of air humidity, thermal dissipation of the pilots, and thermal resistance of cloths are investigated. With the obtained flow and temperature fields, we have improved the calculation method for convective heat transfer on human surface based on Fanger’s thermal comfort model. The human thermal comfort indexes are obtained. The numerical results provide a guide to the design and optimization of air-flow in cockpit to control human thermal comfort for different thermal environments.

Application of Rough Sets in Water Science

LIU zhao;HUANG Qiang;YAN Ai-ling;GONG Wen-lin

2007, 25(6):  645-645 . 

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With a hydropower plant optimum output problem as an example, the output decision-making rules of a power station are obtained through knowledge discovery by introducing variable precision rough set. Compared with general optimized results determined only by water level and inflow of reservoir in current time, the proposed rule based on rough set contains both the current inflow information of reservoir and information of other period, with great flexibility and rationality.

Improved Algorithm for Stochastic Simulation of Reaction-Diffusive Master Equation in Inhomogeneous Space

LIU Xiang;ZHOU Wen;YAN Zheng-lou;WANG Yi-fei

2007, 25(6):  651-651 . 

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We proposed an improved next subvolume method in this paper. Numerical results show that the proposed method can be applied to biochemical reactions systems with complex spatial structure, indicating significant improvement in efficiency compared to existing approaches under some conditions.

Existence of Periodic Solution of Predator-Prey System with Impulsive Effects

YAO Zhi-jian

2007, 25(6):  657-657 . 

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As impulsive phenomena extensively exist in the nature, introduction of impulsive effect into an ecology model can lead to more accurate and reasonable description of the species and the ecological systems. This paper studies a predator-prey system with impulsive effects and Beddington-DeAngelis functional response. We investigate the existence of a periodic solution by using the theory of coincidence degree. Sufficient conditions for the existence of periodic solution are obtained.