Browsing by Author "Wang, CW"

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A near real-time signal to interference ratio measurement technique in a frequency-selective multipath fading channel for the WCDMA system
(2001)
Wang, LC
;
Wang, CW
;
電信工程研究所
;
Institute of Communications Engineering
This paper presents a new concept of realtime SIR estimation for CDMA systems. Unlike conventional symbol-based SIR estimator according to the successively received symbols, we propose a new chip-based SIR estimation method. The key contribution of this paper is to propose a mechnism to exploit the spreading codes of CDMA signals to estimate SIR. Under the COST 259 WCDMA channel model, the simulation results demonstrate that the proposed chip-based SIR estimation algorithm can accurately measure SIR in less than 10(-4) second in several chips, which is about over 1,000 times faster than the traditional symbol-based SIR estimation algorithms.
Adaptive contention window-based cluster head election mechanisms for wireless sensor networks
(2005)
Wang, LC
;
Wang, CW
;
Liu, CM
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交大名義發表
;
National Chiao Tung University
The clustering architecture is essential in achieving the goal of energy efficiency for a wireless sensor network. In general, a clustering algorithm consists of the cluster head election and the cluster member assignment mechanism. This paper proposes an adaptive contention window (ACW)-based cluster head election mechanism. Unlike other legacy cluster head election mechanisms such as LEACH (Low Energy Adaptive Clustering Hierarchy) protocol, the proposed ACW algorithm can achieve four major goals in cluster head election for wireless sensor networks: 1) high successful probability of cluster head election, 2) appropriate number of cluster heads, 3) uniform distribution of cluster heads, and, 4) equal times to be a cluster head for each sensor, simultaneously.
Creative thinking ability, cognitive type and R&D performance
(1999-07-01)
Wang, CW
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Wu, JJ
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Horng, RY
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工業工程與管理學系
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Department of Industrial Engineering and Management
The purpose of this study was to investigate the contributions of creative thinking ability and cognitive type to research and development (R&D) performance. One hundred and six researchers in an R&D institute of a petroleum company in Taiwan were given the Circle Test of the Torrance Test of Creative Thinking and Myers-Briggs Type Indicator. Their R&D performance was measured in terms of assigned technical reports, completed service projects, published papers, and a supervisor's performance rating. Results showed that there was a low but positive correlation between creativity and the first-authored paper and the technical report. The cognitive type was on the other hand associated with the performance rating and the first-authored service project assignment. Implications for R&D management are discussed.
Cross-layer design for determining the optimal number of clusters in a wireless sensor network
(2004)
Wang, LC
;
Wang, CW
;
Liu, CM
;
交大名義發表
;
National Chiao Tung University
The clustering concept can help a wireless sensor network establish hierarchy among numerous sensor nodes. Clustering architecture is essential in achieving the goal of saving power for wireless sensor networks because a cluster representative node can forward data to sink for the covered cluster area. One of key parameters in the clustering design is the number of clusters in a entire wireless sensor network. To this end, we suggest a cross-layer approach to determine an optimal number of clusters in an observation area from the perspectives of physical (PHY) layer, medium access control (MAC) sub-layer, scheduling (SCH) sublayer and network (NET) layer.
Effects of creativity training on manager's problem solving
(1996)
Wang, CW
;
Horng, RY
;
交大名義發表
;
National Chiao Tung University
Nano-carbon nitride synthesis from a bio-molecular target for ion beam sputtering at low temperature
(1999-03-01)
Wu, JJ
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Lu, TR
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Wu, CT
;
Wang, TY
;
Chen, LC
Nano-crystalline carbon nitride has been successfully synthesized at a temperature below 100 degrees C from an adenine(C5N5H5) target sputtered by an Ar ion beam. Because adenine possesses a ring structure similar to the hypothetical beta-C3N4 phase, the use of this bio-molecular compound as the target is believed to reduce the energy barrier of carbon-nitride growth. The effect of Ar ion-sputtering voltage on the film growth and the effect of extra-N-atom incorporation on the carbon-nitride film growth are examined in this study. Only a carbon film is formed with an ion energy of 500 V. For the ion-beam energy above 750 V, carbon nitride films are deposited, and there is some hydrogen incorporation in the films. The N/C composition ratio in the films could reach 1:1 and is independent on the ion beam voltage. The nitrogen is bonded with carbon within the films, as determined by the IR and XPS measurements. However, the films deposited at a higher ion voltage could possess some original functional groups of adenine. A strong and broad peak at a d-spacing of 0.32 nm, comparable to the calculated d-spacing of the beta-C3N4(110), is observed in the XRD spectra of the carbon nitride films. The TEM results indicated that the film contained nano-crystalline grains. Several d values are also in good agreement with those of adenine and the calculated values of beta-C3N4. The C/N ratios of the films are still kept at almost 1:1 with N atoms added during deposition. The XRD spectra and IR spectra of these films are all similar to the film deposited without nitrogen source. (C) 1999 Elsevier Science S.A. All rights reserved.
On the off stoichiometry of cerium oxide thin films deposited by RF sputtering
(1996-04-01)
Chin, CC
;
Lin, RJ
;
Yu, YC
;
Wang, CW
;
Lin, EK
We have studied the stoichiometry of cerium oxide films deposited by RF sputtering as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have an off-stoichiometry of CeOy with y greater than 2.0. Such an off-stoichiometry cannot be due to a mixture of the known phases of bulk cerium oxide samples. Those thin samples may have either cerium vacancies or interstitial oxygen atomic impurities. We have tried to determine the valence of the cerium ions by measuring the X-ray photoemission.
Resonant rutherford backscattering studies of cerium oxide thin films deposited by RF sputtering
(1997-06-01)
Chin, CC
;
Lin, RJ
;
Yu, YC
;
Wang, CW
;
Lin, EK
We have studied the stoichiometry of cerium oxide films deposited by RF sputtering on sapphire and MgO as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have the off-stoichiometry of CeOy with y greater than 2.0. Such an off-stoichiometry cannot be due to a mixture of the known phases of bulk cerium oxide samples. This may be due to either cerium vacancies or interstitial oxygen atomic impurities. The cerium ion x-ray photoemission spectra of those films cannot determine the vacancy of the cerium ions. The c-axis YBaCuo thin flims deposited by sputtering on the CeO3.3 buffer layer on saphhire was found to be epitaxial. The T-c was 86 K with Delta T-c less than 1 K.
Signal to interference ratio measurement techniques for CDMA cellular systems in a frequency-selective multipath fading channel
(2001)
Wang, CW
;
Wang, LC
;
電信工程研究所
;
Institute of Communications Engineering
The signal-to-interference ratio (SIR) is a predominant criterion for radio resource management techniques in wireless networks. Many algorithms such as power control, channel allocation, and handoff, etc. require a fast and accurate SIR measurement. In practice, however, the SIR estimation needs a lot of computations. The major challenge for the SIR estimation issue is to find an efficient way to separate the desired signal with interference. In this paper, we investigate the performance of the SIR estimation techniques for the DS-CDMA cellular system in a time-dispersive (or a frequency-selective) fading channel. The major contribution of this paper is to provide a framework of incorporating the effect of channel dispersions into the SIR estimator for the CDMA systems. We present new results on the quantitative performance of two easily implemented SIR estimation techniques, taking into account the impact of frequency-selective fading, mobility, different number of interferers, and different initial transmission power leverls.