Browsing by Author "Wang, Hung-Hsiang"

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A carbon nanotube field effect transistor with tunable conduction-type by electrostatic effects
(2006-07-01)
Chen, Bae-Horng
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Wei, Jeng-Hua
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Lo, Po-Yuan
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Wang, Hung-Hsiang
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Lai, Ming-Jinn
In this paper, we report a conduction-type-tunable carbon nanotube field effect transistor (CNT-FET) with double-gate structure (DG CNT-FET). In this study, a specially designed narrow top-gate is created to modulate the energy band in the middle region of a single CNT. In the proposed DG device structure, the top-gate and bottom-gate biases exhibit independent modulation behaviors. Depending on whether a positive or negative bias is applied to the top-gate, the CNT-FET can be operated in either n- or p-type conduction. Energy band diagram conducive to the physical mechanisms of the proposed DG CNT-FET device structure is proposed. Based on the proposed hypothesis, ambipolar CNT-FETs can indeed be converted to n- or p-type-like behaviors. (c) 2006 Elsevier Ltd. All rights reserved.
An Antenna Control Mechanism for Distributed Antenna Systems Over High-Speed Railway Communications
(2013)
Wang, Hung-Hsiang
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Hou, Hsin-An
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Chen, Jyh-Cheng
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傳播研究所
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Institute of Communication Studies
Providing broadband wireless services over highspeed railways with Distributed Antenna Systems (DAS) has attracted much attention in recent years. In this paper, we analyze the issues of Time Division Duplex (TDD) DAS, including coverage of Remote Antenna Units (RAUs) and echo channel effect. Also, the timing drift problem while solving the effects of echo on the channel with moving cell in TDD-DAS is investigated. To overcome these problems, we propose techniques for antenna selection with timing compensation. Simulation results show that both the echo channel issue and dilemma between coverage and cost can be solved effectively. Finally, further research studies on enhancing DAS with more intelligence functions such as power saving and resource management are discussed.
Design and Analysis of an Antenna Control Mechanism for Time Division Duplexing Distributed Antenna Systems Over High-Speed Rail Communications
(2016-10-12)
Wang, Hung-Hsiang
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Hou, Hsin-An
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Chen, Jyh-Cheng
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資訊工程學系
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電信工程研究所
Distributed antenna system (DAS) has been introduced to overcome high mobility issues and to extend signals into coverage-hole areas in high-speed rail communications system. In this paper, we discuss echo channel effect and define the corresponding criteria in a time division duplexing (TDD) DAS railway communications system. Furthermore, timing drift problem while applying moving antenna selection technique to solve the echo channel effect is illustrated. Compensation algorithms then are proposed. Simulation results show that the proposed techniques can not only solve the interference problem in TDD-DAS but also provide better scalability in system deployment.
Resource Allocation in Central-Controlled Device-to-Device Communications Networks
(2013-01-01)
Wang, Hung-Hsiang
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Chen, Jyh-Cheng
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Liu, Zi-Ning
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傳播研究所
;
資訊工程學系
Device-to-Device (D2D) communications potentially can improve spectrum efficiency because of resource spatial reuse. In this paper, we consider a central-controlled D2D architecture, in which a cellular operator can decide whether mobile devices can connect to each other directly. We aim to maximize system throughput while also achieve fairness in resource allocation. A resource scheduling algorithm that dynamically adjusts the boundary of resource-assignment area and resource-contention area is proposed. Also, criteria to extract spatial reuse gain and meet proportional fair (PF) metric are determined. Simulation results show that the proposed algorithm can increase system throughput by exploring spatial reuse gain and maintain good proportional fairness among D2D communication pairs.