Table of Content

10 December 2008, Volume 26 Issue 6

Previous Issue    Next Issue

Articles

Multi-user Scheduling in MIMO System with Block Diagonalization

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

2008, 26(6):  551-555 . 

Asbtract ( 2324 )  

Related Articles | Metrics

Implementation of block diagonalization (BD) pre-coding scheme and related multi-user scheduling in multi-user multiple input multiple output (MU-MIMO) system are investigated. By exploiting the subspace decomposition technique, we design the transmit pre-coder matrix to realize simultaneous communications with zero multi-user interference and multiple data streams between transmitter and multi-user. Analysis of the BD scheme is carried out. Based on the maximum sum-capacity criteria, a multi-user scheduling algorithm is proposed with the BD scheme. Its low complexity is shown. Simulations show that, with the BD pre-coding scheme, the achievable throughput of the system adopting the proposed user scheduling is approximately the same as that of the system taking the brute searching user scheduling, and directly validate the proposed user scheduling.

Modeling for Simulation and Distributed Implementation of Mobile WiMAX at System Level


ZHANG Jian;RONG Lu HU Hong-lin

2008, 26(6):  556-561 . 

Asbtract ( 2049 )  

Related Articles | Metrics

Modeling and implementation of a system level evaluation platform based on mobile WiMAX are studied. In order to alleviate the heavy computational burden in simulating wireless channels, a distributed simulation scheme, which manages several computers in a local network, is proposed. This scheme groups channels of different mobile stations according to their cell identities, and then disassembles the channel simulator into multiple computers to achieve parallel computing and reduce simulation time. Moreover, this simulation platform provides interfaces for different algorithms, i.e., scheduling, handover, adaptive modulation and coding, and admission control, to enable scalability. Simulation results show that the proposed scheme achieves reasonable system performance in consistence with theoretical values. When 3 and 5 channel simulators are used, simulation time is reduced by 36.2% and 60.3%, respectively.

Performance of Spread Spectrum Ad Hoc Networks Based on Markov Chain Model

SUN Shi-dong;NIE Jing-nan;

2008, 26(6):  562-568 . 

Asbtract ( 2366 )  

Related Articles | Metrics

An analytical model for performance evaluation of unslotted spread spectrum ad hoc networks is presented by introducing a queuing system and a Markov chain. The model is used to derive packet success probability and expressions for calculating throughput and delay. Based on the derived expressions, the impacts of received SNR, packet length, and spreading gain are discussed in terms of throughput and delay. Numerical results show that a significant improvement in throughput and delay can be obtained by raising SNR at low SNR. However, raising SNR does not improve performance further when SNR>30 dB. Nonetheless, throughput and delay can be improved by reducing the packet length. In addition, improvement of delay performance is acquired when the spreading gain increases. There is an optimal value of spreading gain to maximize the normalized throughput due to the fact that spread spectrum transmission occupies an additional bandwidth.

Small Stopping Sets Counting Methods for Quasi-cyclic Low Density Parity Check Codes based on the Cycle Theory

KONG Ling-jun;XIAO Yang

2008, 26(6):  569-574 . 

Asbtract ( 2152 )  

Related Articles | Metrics

It is well known that performance of low-density parity check (LDPC) codes under iterative decoding is determined by the size of the smallest stopping sets in the Tanner graph. To solve this problem, we propose necessary and sufficient conditions of quasi-cyclic LDPC codes without small stopping sets. According to the proposed theorems and corollaries, we can design good QC-LDPC codes without small stopping sets which outperforms random LDPC codes by SNR=0.3 dB at BER of 1e-5 , and count the number of the small stopping sets. The method can be used effectively to evaluate performance of LDPC codes according to their stopping sets distributions. It can find the number of cycles of LDPC codes which is less complex than existing algorithms.

MCMA Blind Equalization with Affine Projection and Data-Reusing

Liu Shi-gang;Ge Lin-dong;Gong Ke-xian

2008, 26(6):  575-579 . 

Asbtract ( 2185 )  

Related Articles | Metrics

A novel blind equalization algorithm with rapid convergence rate is proposed to receive the burst-mode signal. The idea of affine projection and data-reusing in adaptive filtering field is applied to the modified constant modulus algorithm (MCMA). Compared with the basic MCMA, the proposed method converges faster due to affine projection and data-reusing. Derivation of the algorithm is given and its performance analyzed. In the numerical simulation, the proposed algorithm is compared with the basic MCMA in terms of convergence rate and stationary error.


Sub-band Loudness Compensation for Hearing Aid Based on Human
Auditory

WANG Qing-yun;ZHAO Li;QIAO Jie;ZOU Cai-rong

2008, 26(6):  580-585 . 

Asbtract ( 1751 )  

Related Articles | Metrics

Loudness compensation is a key function of hearing aids. Because the degree of hearing loss varies with frequency, the amount of loudness compensation should be adjusted to adapt the variation. In this paper a new method for sub-band loudness compensation is proposed based on human auditory. Design method for near perfect reconstruction oversampled filter bands is presented. Parameters of the filter bands for senile hearing loss are given. Results of simulation and experiments show that energy loss in different bands of hearing loss patients is well compensated and the recognition rate of sentences is significantly improved.


Image Reconstruction from Limited Range Projections Using Discrete
Orthogonal Moments

DAI Xiu-bin;SHU Hua-zhong;LUO Li-min;Han Guo-niu;Jean Louis Coatrieux;

2008, 26(6):  586-593 . 

Asbtract ( 1842 )  

Related Articles | Metrics

Estimation of projection from unknown views is an efficient way to improve image reconstruction quality when parts of the projections are missing. This paper presents a new method to estimate unknown projections. To achieve better results, we make use of the discrete Radon transform and a set of discrete orthogonal Tchebichef polynomials to establish relationship between the projection moments and the image moments, and then estimate the unknown projections from the known projections using this relationship. Experimental results show that the proposed method provides good image reconstruction quality, and is robust against noise.

Robust Stereo Matching under Point Ambiguity

LIU Tian-liang;LUO Li-min

2008, 26(6):  594-601 . 

Asbtract ( 1893 )  

Related Articles | Metrics

We propose a local stereo mathing algorithm, which relies on combination initial matching via distinctive dissimilarity measure with post-processing by greedy disparity estimation. Based on a dissimilarity measure derived from the stereo itself, the matching costs are first constructed to obtain initial disparities for both views. Then, in order to address complex ambiguity in large occluded regions, a novel disparity estimation procedure including unreliable disparity detection, greedy disparity filling and multi-directional weighted least-square-error fitting is presented to improve matching performance. Experimental results indicate that the proposed method can reduce false matching in ambiguous regions to generate a dense disparity accurately and efficiently.

Application of Digital Watermarking Using Plugins to Prevent Leaking
of E-Documents from Internal Networks

CHEN Chao;SUN Guang-ling;JIAN Ling

2008, 26(6):  602-605 . 

Asbtract ( 2078 )  

Related Articles | Metrics

With the rapid development of information technology, a large number of confidential e-documents are stored in computers, which are prone to leakage due mainly to negligence. Surveys show that up to 90% of the companies face severe financial risks because of data loss. This paper proposes a scheme to prevent e-documents from accidental leaking. This is achieved by embedding watermarks into confidential e-documents. For Microsoft Word files, the watermarks are embedded using specially designed plugins. Confidential documents that carry watermarks are intercepted at the gateway by a watermark detector implemented either with software or hardware.

Co-mapping Algorithm for Network on Chip with Optimal Power Consumption

GE Fen;WU Ning

2008, 26(6):  606-612 . 

Asbtract ( 1950 )  

Related Articles | Metrics

Based on analysis of Network on Chip (NoC) power model and mapping flow, a co-mapping algorithm based on genetic algorithm is proposed to minimize total communication power consumption. The algorithm automatically maps IP cores onto the NoC architecture combining IP selection and task assignment. Experiments are performed on various random benchmarks and a complex video/audio application to conform efficiency of the algorithm. The results show that the proposed algorithm saves on average 30% and 60% of power consumption, respectively, compared to the existing two-step mapping and the IP core-only mapping algorithms.

Energy Source Wave Superposition for Computation of High-Frequency Sound Radiation

CHEN Jian;GAO Yu;XU Bin;CHENG Hao;BI Chuan-xing

2008, 26(6):  613-617 . 

Asbtract ( 1805 )  

Related Articles | Metrics

An energy source wave superposition method for calculating sound radiation from a vibrating structure at high frequency is proposed. Strength of virtual energy sources inside the acoustic source is obtained from acoustic intensity along the normal of the surface. With a matching energy transmission matrix, acoustic energy in the sound field can easily be calculated. The energy wave superposition method is a fast and accurate method which can avoid complicated meshing and integral evaluation involved in the energy boundary element method (EBEM). The validity and effectiveness is verified in the numerical simulation.


Axial Mode Helical Antenna with Variable Pitch Angle and Parasitic Helix Wire

YANG Fang;ZHANG Kai;CHEN Chen;GUO Chenjiang;XU Jia-dong

2008, 26(6):  618-621 . 

Asbtract ( 1924 )  

Related Articles | Metrics

A helical antenna with a variable pitch angle and a parasitic helix wire is designed to improve radiation performance of helical antennas. Its radiation properties including radiation patterns, power gain and axial ratio are simulated using the software FEKO. The results show that power gain can be improved. It is circularly polarized in a wide bandwidth. The method is simple and efficient for improving radiation performance of axial mode helical antennas.

AES S-box Circuit Implementation Based on the Composite Field Arithmetic

LIU Zheng-lin;ZENG Yong-hong;ZOU Xue-cheng;CHEN Li-ming;CHEN Yi-cheng;HAN Yu

2008, 26(6):  622-626 . 

Asbtract ( 2123 )  

Related Articles | Metrics

A full-custom AES S-box architecture based on composite field is proposed. In this S-box, pass transmission gate (PTG) logic style is used to obtain a compact and low-power data-path circuit. Latches controlled by an asynchronous handshake circuit are inserted in the data-path to prevent the propagation of the signal glitch, resulting in reduction of the total S-box circuit power. The property of resisting differential power analysis (DPA) attack of the S-box is improved by inserting random delay chains. The layout-simulations for the S-box circuit using 0.25 um CMOS technology show that it has low power consumption and high-security, and remains small-area overhead as in the corresponding composite field S-box.


Kernel-Based Nonlinear Discriminant Method in Text Classification

LIU Hai-feng;YAO Ze-qing;LIU Shou-sheng;WANG Qian

2008, 26(6):  627-631 . 

Asbtract ( 1793 )  

Related Articles | Metrics

To achieve feature reduction in text categorization, the scatter difference criterion is improved to satisfy a broad range of text categorization problems using kernel commutation in the pre-treatment. A kernel-based nonlinear method is proposed to extract features. By kernel commutation, the stylebook categorization problem is solved with less linear separability. Dimension of the feature space is significantly reduced without incurring excessive information loss. Experiments show that performance of the proposed method is better than maximal scatter difference with an efficiency improvement of 4.7% for the value of F1.


Parallel Analysis and Partitioning of SoC System

WU Yue;XU Bao-yu;TANG Li-san;YANG Hong-bin

2008, 26(6):  632-637 . 

Asbtract ( 2095 )  

Related Articles | Metrics

Based on the recent trend of SoC development and the effect of parallel partitioning, a method of SoC parallel design at the system-level is presented. Parallelism of SoC model is analyzed. A new algorithm is proposed to partition the SoC model. The algorithm is based on the greedy rule, which deals with the load balancing problem. Experimental results show that partitioning at the system level of SoC is desirable for improving time consumption and overcoming the low-efficiency problems in SoC system.

Spiking Neural Networks with Neurons Firing Multiple Spikes

FANG Hui-juan;WANG Yong-ji

2008, 26(6):  638-644 . 

Asbtract ( 1989 )  

Related Articles | Metrics

A more biologically plausible spiking response model (SRM) is presented to cope with the learning problem of spiking neural networks (SNN) in which neurons can spike multiple times. In constructing this model, the dependence of the postsynaptic potential upon the firing times of the postsynaptic neuron is not neglected. We derive an additional error back-propagation learning rule for the coefficient of the refractoriness function. The algorithm has been tested on classification tasks or XOR problem, IRIS dataset and Poisson spike trains. The results show that the SRM based SNN with neurons that fire multiple spikes can transfer information more efficiently and speed up training compared to SNN with neurons that fire only once.


Application of Improved Attitude Algorithm of Strapdown Inertial
Based on FOG

SONG Gui-hua;ZHAO Wei;LIU Jian-ye;ZHU Yan-hua

2008, 26(6):  645-649 . 

Asbtract ( 2267 )  

Related Articles | Metrics

The strap-down inertial navigation system (SINS) usually uses rotation vector attitude algorithms to eliminate the influence of coning error and increase precision of attitude calculation. This paper presents simulation results of several low order rotation vector attitude algorithms with angle rate suitable for engineering applications. An optimum algorithm is proposed to minimize drift error due to both coning motion and noise in the fiber optic gyro output signal at each level. Rotation vector attitude algorithms are tested on a high performance DSP micro navigation computer, and satisfactory results are obtained.


Robust Adaptive Backstepping Control of Nonlinear Systems with Uncertainty

HE Nai-bao;JIANG Chang-sheng;GAO Qian

2008, 26(6):  650-654 . 

Asbtract ( 2762 )  

Related Articles | Metrics

For a class of nonlinear systems with bounded disturbance uncertainties, the robust adaptive ε-output-tracking control problem is dealt with. Combining the backstepping method with robust control, a new robust output feedback controller is developed for unknown parameters and dynamic uncertainties. It is shown that the derived controller based on the Lyapunov stability theory can ensure global uniform boundedness for all states of a closed-loop system, and convergence of tracking error within an arbitrarily small neighborhood of the origin. Simulation results are provided to show effectiveness of the proposed approach.


Stability Test for Time-Delay Partial Differential Equation Systems

XIAO Yang;KIM Kiseon

2008, 26(6):  655-660 . 

Asbtract ( 2064 )  

Related Articles | Metrics

Stability of time-delay partial differential equations (TDPDE) systems involves 2D quasi-polynomials, while zeros of the characteristic polynomials (2D quasi-polynomials) of TDPDE systems are some continuous and hyper curved surfaces. Zeros are not isolated and separated, leading to difficulty in the stability test of TDPDE systems. To solve the problem, this paper proposes an approach to test asymptotic stability of TDPDE systems by a Hurwitz stability test of 2D characteristic polynomials of the systems. The proposed theorems establish the relationship between the asymptotic stability of TDPDE systems and the Hurwitz stability test of 2D characteristic polynomials, and provide a test approach of the Hurwitz stability test of 2D characteristic polynomials (2D quasi-polynomials). Base on the results, a numerical algorithm with a simpler test procedure for Hurwitz-Schur stability test of 2D quasi-polynomials is developed. An example illustrates the application of the proposed approach.