Table of Content

26 January 2011, Volume 29 Issue 1

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Communication Engineering

Limited Quantization Feedback Design Based on Error Correction in Base Station Coordination System

HAN Dong-sheng1;3, YANG Wei1;2, XU Chang-long2

2011, 29(1):  9-14.  doi:10.3969/j.issn.0255-8297.2011.01.002

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 This paper proposes a limited quantization feedback mechanism based on error revising according to the characteristics of base-station coordination system. In this mechanism, the channel quantization process is divided into many steps. The number of the steps equals the number of coordinating base stations. Each quantization step corrects the errors in the previous step. From the complexity analysis and system simulations, it is concluded that the new mechanism reduces quantization complexity with very small degradation in the performance as compared to the existing global feedback mechanisms. It improves the system performance with very little increase in complexity as compared to the existing individual feedback mechanisms. The proposed mechanism provides a good tradeoff between complexity and system performance.

Research and Optimization of Indoor Relay Network Deployment

PEI Yu-shan1;2, TIAN Hui1;2, WANG Ying1;2, SONG Lei1;2

2011, 29(1):  15-21.  doi:10.3969/j.issn.0255-8297.2011.01.003

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To deal with complex indoor wireless environments and high throughput requirements, deployment of indoor relay networks is investigated. A mathematical model is established for large office buildings, with adaptively changed parameters are adaptive to meet the practical conditions. As an example, relay network deployment in an indoor scenario with a large local environment is considered. With the proposed model, the number of access points, the locations of deployment, and the selection of relay work modes are derived based on the system performance requirements. The simulation results show that deploying relay stations in the studied environment can effectively improve the system throughput and coverage. Taking both systemperformance and network-cost into account, one base station and four amplify-forward relay stations can form an ideal deployment.

Effect of Atmospheric Turbulence on Maximal Zenith Angle of Satellite-to-Ground Laser Communication Links

LI Yong-liang1, WANG Jian-yu1;2, XU Rui1, LIN Ri-zhao1, FU Zhong-qian1

2011, 29(1):  22-26.  doi:10.3969/j.issn.0255-8297.2011.01.004

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Abstract: A concept of "maximal zenith angle" is proposed for satellite-to-ground laser communication links. A method for building the maximal zenith angle model is presented. We consider links using on-off-keying (OOK) modulation and avalanche photodiode detector (APD). Relationship among the maximal zenith angel, the nominal value of atmosphere turbulent intensity, and the bit error rate (BER) is obtained. This is done based on gamma-gamma (GG) probability density function (PDF), Web-Gaussian approximation of APD, and the Hufnagel-Valley model of the atmosphere turbulent intensity. With the laser signal power set at 2W, the simulation results show that the maximal zenith angel is clearly decreased with the nominal value
of atmosphere turbulent intensity, and increased with BER. A empirical model of maximal zenith angel is obtained using nonlinear curve fitting.

Scaling Factor Quantization for LDPC Codes

ZHANG Xiao-jun1, TIAN Ying-hong1, YU lei1, RAN feng2, LAI Zong-sheng1

2011, 29(1):  33-38.  doi:10.3969/j.issn.0255-8297.2011.01.006

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This paper proposes a quantization scheme for low density parity check(LDPC) codes based on scaling factor by analyzing message distribution and the effect of quantization saturation. Messages are scald for the check nodes and variable nodes, and for the initial channel value. Using the scaling, the scheme allows the integer part of message to include more information, and can lower the effect of quantization saturation. Messages of nodes are quantized with (q; 0). Due to the application of integer part instead of floating point operation, the hardware complexity is significantly reduced. Simulation of (7 493, 3 048) using normalized Min-Sum displays an implementation loss of about 0.1 dB compared with floating performance.

Computer Science and Applications

Language Properties for Rationality of Workflow Net System

YAN Chun-gang1;2, JIANG Chang-jun1;2, DING Zhi-jun1;2, SUN Ping1;2

2011, 29(1):  61-65.  doi:10.3969/j.issn.0255-8297.2011.01.011

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Soundness of workflow system is a fundamental requirement in formalizing transaction processing flow. Most current researches convert soundness of workflow net (WF-net) system to liveness and boundedness of its extended workflow net system. The soundness property is studied in this paper from the language viewpoint of the workflow net system. Net language depiction for soundness is presented to reveal the behavior
characteristic of this basic property. Furthermore, synchronous composition and combined composition of the workflow net system is studied. Necessary and sufficient conditions are given for soundness preservation of the two composition systems. This study provides a novel approach to the modeling and analysis for composition in complex WF-net systems.

Control and System

Feedback Stabilization for a Class of Distributed Parameter Switched Systems with Time Delay

DONG Xue-ping, WEN Rui, LIU Hong-liang

2011, 29(1):  92-96.  doi:10.3969/j.issn.0255-8297.2011.01.016

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 Feedback stabilization for a class of distributed parameter switched systems (DPSS) with time-delay is studied. By constructing Lyapunov functions and employing the Green formula, several sufficient conditions of state feedback stabilization for a class of DPSS with constant time delay are derived. These conditions are described using a group of linear matrix inequalities (LMI). Thus design of state feedback controllers of DPSS is converted to a group of LMI. The controllers can be solved efficiently with the Matlab LMI toolbox. In addition, the proposed method has the advantage that the criteria can easily be checked and applied. A numerical example is given to illustrate validity of the design method.