Browsing by Author "Chen, Jyh-Cheng"

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A Local Mobility Management Entity (MME) for Stationary Devices in virtual Evolved Packet Core (vEPC)
(2018-01-01)
Qiu, Bo-Jun
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Li, Jia-Ru
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Hsueh, Yu-Sen
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Lin, You-Min
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Chen, Jyh-Cheng
In the future, there will be many devices in 5G networks, and these devices will cause a great number of control messages. The core network should handle these control messages locally to maintain the quality of other services. Furthermore, the local MME should turn off the location update flows in the initial attach procedure to reduce the number of control messages. We implement an MME, which can turn off the location update flows, and then compare the performance.
A New SDN-Based Architecture and Authentication Method for Taiwan High-Speed Rail
(2017-01-01)
Lin, Yi-Hao
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Ho, Ping-Fan
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Chen, Jyh-Cheng
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Yang, Jen-Shun
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Chang, Hsien-Wen
The urgency of improving user experience has reached a critical point in the high-speed rail environment. However, there is little literature considering authentication failure problems in the high-speed rail environment. In this paper, we present a new authentication architecture for Taiwan High-Speed Rail (THSR). This new authentication architecture applies Software-Defined Network (SDN)-based principles to an outbound LTE gateway platform. We propose a post-authentication method suitable for the high-speed mobile environment, such as THSR. The proposed architecture and method can improve user experience regarding successful authentication ratio, authentication latency, and network access latency compared to the existing system.
A New SDN-Based Authentication Architecture and Method for Taiwan High Speed Rail
(2016)
Lin, Yi-Hao
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Ho, Ping-Fan
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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
In this paper, we present a new authentication architecture for Taiwan High Speed Rail (THSR). The new authentication architecture applies multiple outbound LTE gateways. We also propose an SDN-based authentication method using post-authentication that is suitable for high-speed environment, including THSR. The proposed architecture and method can reduce network congestion and shorten the authentication latency compared to the existing system.
Adjustable Extended Discontinuous Reception Cycle for Idle-State Users in LTE-A
(2016-11)
Chang, Chia-Wei
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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
In the long term evolution advanced, a user in idle state can activate the discontinuous reception (DRX) to save its energy, and the 3GPP extends the length of a DRX cycle. Therefore, how to configure the extended DRX (eDRX) cycle is a tradeoff between the tracking area update (TAU) cost (the cost of updating a user\'s location) and the paging cost (the cost of waking up a user). In this letter, we analyze the tradeoff and determine the optimal length for the eDRX cycle under the latency constraint. The objective function is to minimize the total signaling cost considering the tradeoff between TAU cost and paging cost. The analytical and simulation results demonstrate that the proposed mathematical model can mitigate the signaling cost for the networks.
An adaptive low-overhead resource discovery protocol for mobile ad-hoc networks
(2011-02-01)
Liang, Jui-Chi
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Chen, Jyh-Cheng
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Zhang, Tao
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資訊工程學系
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Department of Computer Science
In this paper we propose a Distributed Hash Table (DHT)-based peer-to-peer resource discovery protocol designed for large-scale Mobile Ad-hoc NETwork (MANET). The proposed Mobile Resource Discovery Protocol (MRDP) uses a distributed dynamic clustering algorithm to adaptively and rapidly group nodes in a MANET for resource discovery purpose, and utilizes DHTs to efficiently cache resource information in a peer-to-peer manner. We provide a probabilistic lower bound on the performance of the MRDP. We also present simulation results under different scenarios to show that MRDP has low message overheads and its performance is highly insensitive to the size of the MANET. These characteristics make MRDP suitable for large-scale MANETs.
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.
ASA: Adaptive VNF Scaling Algorithm for 5G Mobile Networks
(2018-01-01)
Ren, Yi
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Tuan Phung-Duc
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Liu, Yi-Kuan
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Chen, Jyh-Cheng
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Lin, Yi-Hao
5G mobile networks introduce Virtualized Network Functions (VNFs) to provide flexible services for incoming huge mobile data traffic. Compared with fixed capacity legacy network equipment, VNFs can be scaled in/out to adjust system capacity. However, hardware-based legacy network equipment is designed dedicatedly for its purpose so that it is more efficient in terms of unit cost. One challenge is to best use VNF resources and to balance the traffic between legacy network equipment and VNFs. To address this challenge, we first formulate the problem as a cost-performance tradeoff, where both VNF resource cost and system performance are quantified. Then, we propose an adaptive VNF scaling algorithm to balance the tradeoff. We derive the suitable VNF instances to handle data traffic with minimizing cost. Through extensive simulations, the adaptive algorithm is proven to provide good performance.
Astaxanthin down-regulates Rad51 expression via inactivation of AKT kinase to enhance mitomycin C-induced cytotoxicity in human non-small cell lung cancer cells
(2016-04-01)
Ko, Jen-Chung
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Chen, Jyh-Cheng
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Wang, Tai-Jing
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Zheng, Hao-Yu
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Chen, Wen-Ching
Astaxanthin has been demonstrated to exhibit a wide range of beneficial effects, including anti-inflammatory and anti-cancer properties. However, the molecular mechanism of astaxanthin-induced cytotoxicity in non-small cell lung cancer (NSCLC) cells has not been identified. Rad51 plays a central role in homologous recombination, and studies show that chemo-resistant carcinomas exhibit high levels of Rad51 expression. In this study, astaxanthin treatment inhibited cell viability and proliferation of two NSCLC cells, A549 and H1703. Astaxanthin treatment (2.5-20 mu M) decreased Rad51 expression and phospho-AKT(Ser473) protein level in a time and dose-dependent manner. Furthermore, expression of constitutively active AKT (AKT-CA) vector rescued the decreased Rad51 mRNA and protein levels in astaxanthin-treated NSCLC cells. Combined treatment with phosphatidylinositol 3-kinase (PI3K) inhibitors (LY294002 or wortmannin) further decreased the Rad51 expression in astaxanthin-exposed A549 and H1703 cells. Knockdown of Rad51 expression by transfection with si-Rad51 RNA or cotreatment with LY294002 further enhanced the cytotoxicity and cell growth inhibition of astaxanthin. Additionally, mitomycin C (MMC) as an anti-tumor antibiotic is widely used in clinical NSCLC chemotherapy. Combination of MMC and astaxanthin synergistically resulted in cytotoxicity and cell growth inhibition in NSCLC cells, accompanied with reduced phospho-AKT(Ser473) level and Rad51 expression. Overexpression of AKT-CA or Flag-tagged Rad51 reversed the astaxanthin and MMC-induced synergistic cytotoxicity. In contrast, pretreatment with LY294002 further decreased the cell viability in astaxanthin and MMC co-treated cells. In conclusion, astaxanthin enhances MMC-induced cytotoxicity by decreasing Rad51 expression and AKT activation. These findings may provide rationale to combine astaxanthin with MMC for the treatment of NSCLC. (C) 2016 Elsevier Inc. All rights reserved.
Channel Holding Time of Packet Sessions in All-IP Cellular Networks
(2014)
Weng, Jeng-Feng
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Ku, Bying-He
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Chen, Jyh-Cheng
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Chen, Wen-Tsuen
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資訊工程學系
In this paper, we analyze the packet session channel holding time for packet-switched cellular networks. Channel holding time depends on mobility which is characterized by cell residence time in this paper. We apply Hyper-Erlang distribution model to investigate the packet session channel holding time in which a session will experience active and idle periods. In terms of new session, handoff session in busy mode, handoff session with new arrival packets in idle mode and handoff session without arrival packet in idle mode, we demonstrate that the effective channel holding time is exponentially distributed if and only if the cell residence time is exponentially distributed. The analytical results provide a new approach to evaluate traffic performance and system design in packet-switched cellular networks.
Comparative Analysis of Energy-Saving Techniques in 3GPP and 3GPP2 Systems
(2009-01-01)
Yeh, Jui-Hung
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Chen, Jyh-Cheng
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Lee, Chi-Chen
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瑞昱交大聯合研發中心
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Pealtek NCTU Joint Res Ctr
Energy conservation is essential to wireless networks, particularly for third-generation (3G) and fourth-generation (4G) wireless systems, because high-speed data transmissions would rapidly exhaust the energy of a mobile station. This paper presents the details of energy-saving mechanisms for packet data services in two major standards, namely, the Third-Generation Partnership Project (3GPP) and the Third-Generation Partnership Project 2 (3GPP2). In addition to qualitative comparison, analytic models and quantitative comparison based on the energy-saving models are provided. The proposed analytic models analyze and quantify the energy consumption for bursty and streaming traffic in cdma2000 and wideband code division multiple access (WCDMA). The impacts of an inactivity timer on energy consumption and reconnection cost are demonstrated further by simulation and analysis. The analytic results could be used to suggest proper timer lengths that can balance the energy consumption and the reconnection cost. In addition to providing insights of the energy-conservation mechanisms of 3GPP and 3GPP2, which are often difficult to directly obtain from standards specifications, results shown in this paper are also practical for 3GPP and 3GPP2 operators to determine proper parameters for energy efficiency.
Congestion Control for Machine-Type Communications in LTE-A Networks
(2016-01-01)
Chang, Chia-Wei
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Lin, Yi-Hao
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Ren, Yi
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Chen, Jyh-Cheng
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資訊工程學系
Collecting data from a tremendous amount of Internet-of-Things (IoT) devices for next generation networks is a big challenge. A large number of devices may lead to severe congestion in Radio Access Network (RAN) and Core Network (CN). 3GPP has specified several mechanisms to handle the congestion caused by massive amounts of devices. However, detailed settings and strategies of them are not defined in the standards and are left for operators. In this paper, we propose two congestion control algorithms which efficiently reduce the congestion. Simulation results demonstrate that the proposed algorithms can achieve 20 similar to 40% improvement regarding accept ratio, overload degree and waiting time compared with those in LTE-A.
Design and Analysis of a Threshold Offloading (TO) Algorithm for LTE Femtocell/Macrocell Networks
(2016)
Chen, Wei-Han
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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.
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.
Design and Analysis of Deadline and Budget Constrained Autoscaling (DBCA) Algorithm for 5G Mobile Networks
(2016-01-01)
Than Phung-Duc
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Ren, Yi
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Chen, Jyh-Cheng
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Yu, Zheng-Wei
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資訊工程學系
In cloud computing paradigm, virtual resource autoscaling approaches have been intensively studied recent years. Those approaches dynamically scale in/out virtual resources to adjust system performance for saving operation cost. However, designing the autoscaling algorithm for desired performance with limited budget, while considering the existing capacity of legacy network equipment, is not a trivial task. In this paper, we propose a Deadline and Budget Constrained Autoscaling (DBCA) algorithm for addressing the budget-performance tradeoff. We develop an analytical model to quantify the tradeoff and cross-validate the model by extensive simulations. The results show that the DBCA can significantly improve system performance given the budget upper-bound. In addition, the model provides a quick way to evaluate the budget-performance tradeoff and system design without wide deployment, saving on cost and time.
Design and Analysis of the Gateway Relocation and Admission Control Algorithm in Mobile WiMAX Networks
(2012-01-01)
Liu, Zong-Hua
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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
The WiMAX Forum has defined a two-tiered mobility management to minimize handover delay and packet loss. However, it leads to another problem: When to perform ASN GW relocation? The standards only define the ASN GW relocation procedures without specifying when the ASN GW relocation should be performed. It is left for vendors and operators to develop their own proprietary solutions. In this paper, we propose an algorithm, which incorporates traditional Admission Control (AC) and Wiener Process (WP)-based prediction algorithms to determine when to carry out ASN GW relocation. We further develop an analytical model to analyze the proposed algorithm. Simulations are also conducted to evaluate the performance of the proposed algorithm. The results show that the proposed algorithm can improve the performance significantly in terms of blocking probability, dropping probability, average serving rate, and average signaling overhead.
Design and Analysis of the Key Management Mechanism in Evolved Multimedia Broadcast/Multicast Service
(2016-12)
Ren, Yi
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Chen, Jyh-Cheng
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Chin, Jui-Chih
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Tseng, Yu-Chee
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資訊工程學系
3GPP introduced the key management mechanism (KMM) in evolved multimedia broadcast/multicast service (eMBMS) to provide forward security and backward security for multicast contents. In this paper, we point out that KMM may lead to frequent rekeying and re-authentication issues due to eMBMS\'s characteristics: 1) massive group members; 2) dynamic group topology; and 3) unexpected wireless disconnections. Such issues expose extra load for both user equipment (UE) terminals and mobile operators. It seems prolonging the rekeying interval is an intuitive solution to minimizing the impact of the issues. However, a long rekeying interval is not considered the best operational solution due to revenue loss of content providers. This paper quantifies the tradeoff between the load of the UEs and the operators as well as the revenue loss of the content providers. Moreover, we emphasize how essential this rekeying interval has impacts on the problems. Using our proposed tradeoff model, the operators can specify a suitable rekeying interval to best balance the interest between the above three parties. The tradeoff model is validated by extensive simulations and is demonstrated to be an effective approach for the tradeoff analysis and optimization on eMBMS.
Design, Implementation and Experiments of a Wi-Fi D2D-based Automatic Vehicle Location (AVL) System
(2016)
Ho, Ping-Fan
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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
In this paper, we propose WiAVL, a novel Automatic Vehicle Location (AVL) system based on Wi-Fi Device-to-Device (D2D) communications. WiAVL can monitor, record and notify the location of public transportation vehicles with low communication cost by leveraging Wi-Fi Beacons. In addition, we address the interference problem. A proof-of-concept prototype is implemented. Experimental results are also presented to demonstrate the feasibility and performance results of the proposed system.
Development of LabVIEW Based Micro Computed Tomography System on Vertical Rotary Gantry
(2015-01-01)
Tu, Shih-Huan
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Chen, Ya-Chen
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Hsiao, Tzu-Chien
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Jin, Shih-Chun
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Chen, Jyh-Cheng
Construction of a micro computed tomography (micro-CT) system has been proposed and developed in recent years. For the need of exploring and investigating a novel computed tomography (CT) image reconstruction method, custom-built micro-CT system offers a corresponding laboratory research environment. To develop a controllable program capable of incorporating with different devices efficiently, we use Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW), a graphical programming language, as our programming environment to implement micro-CT system on vertical rotary gantry. We scanned and reconstructed the 360 projections derived from full 360 degrees scan with angular stepping of 1 degrees. Total scan time is about 9.1 minutes. We will combine micro fluorescence tomography (micro-FT) and micro-CT on uni-platform in the future.
Development of Limited-Angle Iterative Reconstruction Algorithms with Context Encoder-Based Sinogram Completion for Micro-CT Applications
(2018-12-01)
Jin, Shih-Chun
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Hsieh, Chia-Jui
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Chen, Jyh-Cheng
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Tu, Shih-Huan
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Chen, Ya-Chen
Limited-angle iterative reconstruction (LAIR) reduces the radiation dose required for computed tomography (CT) imaging by decreasing the range of the projection angle. We developed an image-quality-based stopping-criteria method with a flexible and innovative instrument design that, when combined with LAIR, provides the image quality of a conventional CT system. This study describes the construction of different scan acquisition protocols for micro-CT system applications. Fully-sampled Feldkamp (FDK)-reconstructed images were used as references for comparison to assess the image quality produced by these tested protocols. The insufficient portions of a sinogram were inpainted by applying a context encoder (CE), a type of generative adversarial network, to the LAIR process. The context image was passed through an encoder to identify features that were connected to the decoder using a channel-wise fully-connected layer. Our results evidence the excellent performance of this novel approach. Even when we reduce the radiation dose by 1/4, the iterative-based LAIR improved the full-width half-maximum, contrast-to-noise and signal-to-noise ratios by 20% to 40% compared to a fully-sampled FDK-based reconstruction. Our data support that this CE-based sinogram completion method enhances the efficacy and efficiency of LAIR and that would allow feasibility of limited angle reconstruction.
Dynamic Auto Scaling Algorithm (DASA) for 5G Mobile Networks
(2016-01-01)
Ren, Yi
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Phung-Duc, Tuan
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Chen, Jyh-Cheng
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Yu, Zheng-Wei
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資訊工程學系
Network Function Virtualization (NFV) enables mobile operators to virtualize their network entities as Virtualized Network Functions (VNFs), offering fine-grained on-demand network capabilities. VNFs can be dynamically scale-in/ out to meet the performance desire and other dynamic behaviors. However, designing the auto-scaling algorithm for desired characteristics with low operation cost and low latency, while considering the existing capacity of legacy network equipment, is not a trivial task. In this paper, we propose a VNF Dynamic Auto Scaling Algorithm (DASA) considering the tradeoff between performance and operation cost. We develop an analytical model to quantify the tradeoff and validate the analysis through extensive simulations. The results show that the DASA can significantly reduce operation cost given the latency upper-bound. Moreover, the models provide a quick way to evaluate the cost-performance tradeoff and system design without wide deployment, which can save cost and time.