Browsing by Author "Chen, Wei-Han"

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Abnormal C-V Hump Effect Induced by Hot Carriers in Gate Length-Dependent p-Type LTPS TFTs
(2019-11-01)
Huang, Shin-Ping
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Chen, Po-Hsun
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Tsao, Yu-Ching
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Chen, Hong-Chih
;
Zheng, Yu-Zhe
We investigate the abnormal current-voltage (C-V) hump effect of p-type low-temperature polysilicon (LTPS) thin-film transistors (TFTs) which have undergone high current operations. Experimental results indicate localized electron trapping in the gate insulator (GI), which is carried out near the drain. The ON-current ( ${I}_{ \mathrm{\scriptscriptstyle ON}}$ ) enhancement is due to the reduction of effective length, and the OFF-current ( ${I}_{ \mathrm{\scriptscriptstyle OFF}}$ ) decrease as the electron tunneling path distance increases. These can be observed after hot carrier stress in current characteristics. The C-V measurements demonstrate that the threshold voltage ( ${V}_{\text {th}}$ ) shift is associated with the gate length. In addition, capacitance-voltage measurements also show that this localized trapping region remains the same in length, regardless of channel length. Hence, a model is proposed to explain how the electric field, which is gate length-dependent, affects the source side of the device, and then lowers the source barrier height. This leads to bulk leakage, which causes the subthreshold swing degradation at device scale down.
Design and Analysis of a Threshold Offloading (TO) Algorithm for LTE Femtocell/Macrocell Networks
(2016)
Chen, Wei-Han
;
Ren, Yi
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Chen, Jyh-Cheng
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資訊工程學系
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Department of Computer Science
LTE femtocells have been commonly deployed by network operators to increase network capacity and offload mobile data traffic from macrocells. A User Equipment (UE) camped on femtocells has the benefits of higher transmission rate and longer battery life due to its proximity to the base stations. However, various user mobility behaviors may incur frequent signaling overhead and degrade femtocell offloading capability. To efficiently offload mobile data traffic, we propose a Threshold Offloading (TO) algorithm considering the trade-off between network signaling overhead and femtocell offloading capability. In this paper, we develop an analytical model to quantify the trade-off and validate the analysis through extensive simulations. The results show that the TO algorithm can significantly reduce signaling overhead at minor cost of femtocell offloading capability. Moreover, this work offers network operators guidelines to set offloading threshold in accordance with their management policies in a systematical way.
Determining motions with an IMU during level walking and slope and stair walking
(1970-01-01)
Chen, Wei-Han
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Lee, Yin-Shin
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Yang, Ching-Jui
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Chang, Su-Yu
;
Shih, Yo
This study investigated whether using an inertial measurement unit (IMU) can identify different walking conditions, including level walking (LW), descent (DC) and ascent (AC) slope walking as well as downstairs (DS) and upstairs (US) walking. Thirty healthy participants performed walking under five conditions. The IMU was stabilised on the exterior of the left shoe. The data from IMU were used to establish a customised prediction model by cut point and a prediction model by using deep learning method. The accuracy of both prediction models was evaluated. The customised prediction model combining the angular velocity of dorsi?plantar flexion in the heel-strike (HS) and toe-off (TO) phases can distinctly determine real conditions during DC and AC slope, DS, and LW (accuracy: 86.7?96.7%) except for US walking (accuracy: 60.0%). The prediction model established by deep learning using the data of three-axis acceleration and three-axis gyroscopes can also distinctly identify DS, US, and LW with 90.2?90.7% accuracy and 84.8% and 82.4% accuracy for DC and AC slope walking, respectively. In conclusion, inertial measurement units can be used to identify walking patterns under different conditions such as slopes and stairs with customised prediction model and deep learning prediction model.
Enabling Seamless WiGig/WiFi Handovers in Tri-band Wireless Systems
(2017-01-01)
Li, Yao-Yu
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Li, Chi-Yu
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Chen, Wei-Han
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Yeh, Chia-Jui
;
Wang, Kuochen
WiGig enables wireless multi-gigabit communication over 60GHz band. However, its usage scenarios may be constrained by two major limitations: line-of-sight propagation and very short transmission range. We seek to boost the WiGig's usability by using WiFi to complement its limitations in triband (2.4/5/60GHz) wireless systems. Our goal is to let a triband client have multimedia services at the WiGig's very high speed without any hassle. When the WiGig link is down or performs bad, not only can the client temporarily handover to WiFi without service interruption, but its ongoing multimedia services can also adapt to the WiFi's slower link. Though the IEEE 802.11ad standard has proposed an FST (Fast Session Transfer) mechanism to support handover operations at the link layer, it does not satisfy our goal due to two reasons. First, it does not specify when to performWiGig/WiFi handovers. Second, it is not application-aware to achieve the service adaptation. To this end, we design and implement an application-aware, seamless WiGig/WiFi handover solution above the network layer. It ensures timely handover trigger for the WiGig's abrupt link interruption, keeps service continuity during handovers, and adapts multimedia service qualities to differentWiGig/WiFi links. Our demo confirms its viability. We show that a video streaming service at the client is not interrupted during WiGig/WiFi handovers, which are triggered by mobility or the WiGig's signal blockage, but smoothly switches between different resolutions according to different links.
Enhancement of Mechanical Bending Stress Endurance Using an Organic Trench Structure in Foldable Polycrystalline Silicon TFTs
(2020-05-01)
Zheng, Yu-Zhe
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Huang, Shin-Ping
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Chen, Po-Hsun
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Chang, Ting-Chang
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Tsai, Tsung-Ming
This letter proposes a new organic trench structure which can enhance the endurance of polycrystalline silicon thin film transistors (TFTs) under mechanical bending stress. It compares conventional structure TFTs to devices with an organic trench to examine reliability after undergoing 100,000 iterations of channel width-axis (100,000'WC) compression at R = 2mm. Due to the low Young's modulus of organic materials, stress while undergoing bending strain is desorbed to the buffer layer, which can lower the overall stress in TFTs. Furthermore, an optimal location and ideal length for such an organic trench is evaluated by mechanical bending simulation.
Over-The-Air Provisioning for IoT Wearable Devices via BLE and oneM2M
(2019-01-01)
Chen, Wei-Han
;
Lin, Fuchun Joseph
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資訊工程學系
;
Department of Computer Science
Over-The-Air (OTA) provisioning is an important technology describing the ability to change or update the applications in the devices over the wireless network. To enable the OTA provisioning for wearable devices, the wireless technologies need to take into consideration the limited capabilities of these devices. In recent years, Bluetooth Low Energy (BLE) has emerged as the protocol choice for many wearable devices including mobile handsets. In this research, we develop technologies that enable the OTA provisioning for the wearable devices via BLE and oneM2M. We focus on two BLE communication methods: (1) Interworking Proxy Application Entity (IPE) and (2) 6LoWPAN over BLE, and evaluating and comparing these'two BLE communication methods for the OTA provisioning by investigating the performance metrics of each. Our research objective is to determine the best suitable design for the OTA provisioning.