Browsing by Author "Chen, Yu-Jia"

Now showing 1 - 20 of 31

A Cloud-Assisted Network Coded Packet Retransmission Approach for Wireless Multicasting
(2014)
Chen, Yu-Jia
;
Ho, Wan-Ling
;
Wang, Li-Chun
;
Wang, Kuo-Chen
;
交大名義發表
In this paper, we propose a cloud-assisted network coded packet retransmission approach to reduce the number of packet retransmission in wireless multicasting. It is shown that the efficiency of packet retransmission can be significantly improved if we include network topology information (e.g., network connectivity) during the encoding process of network coding. We leverages the capability of software-defined networking (SDN) to dynamically monitor and control the entire network and design a network topology based network coded packet retransmission (NTNCPR) mechanism. The proposed NTNCPR mechanism can easily calculate the good packet combination based on network topology information.
A Dynamic Security Traversal Mechanism for Providing Deterministic Delay Guarantee in SDN
(2014-01-01)
Chen, Yu-Jia
;
Lin, Feng-Yi
;
Wang, Li-Chun
;
Lin, Bao-Shuh
;
電機資訊學士班
For security concerns, a security traversal service can route data flows through a sequences of security devices (middleboxes). In this paper, we identify the problem of delay guarantee in security traversal and propose a scheme to dynamically change the security traversal path. To provide deterministic delay guarantee with minimum virtual machine (VM) and transmission cost, we model this security traversal path determination as a constrained shortest path problem (CSP) and propose an optimal security traversal with middlebox addition (OSTMA) mechanism. Besides, we implement the proposed OSTMA mechanism in an Open Flow network by designing a centralized security traversal controller to dynamically monitor the network condition information and reconfigure the security traversal path. Our experimental results show that the proposed dynamic security traversal scheme can still achieve delay requirements for network topology changes and burst traffic.
A Personal Emergency Communication Service for Smartphones using FM transmitters
(2013-01-01)
Chen, Yu-Jia
;
Lin, Chia-Yu
;
Wang, Li-Chun
;
交大名義發表
;
National Chiao Tung University
Communication networks such as cellular phone networks are quite likely to be severely damaged during a large-scale of disaster, making SOS message dissemination to rescue authorities extremely difficult. In this paper, we first propose a FM radio-based emergency communication service through the integration of FM transmitters into smartphones. FM radio provides a number of advantages such as longer propagation length and less susceptible to obstacles, making it suitable for broadcasting SOS messages. Besides, we design Morse code-based SOS message dissemination using FM transmitters (MCSOS-FM) and its corresponding communication procedure for the emergency communication service in order to improve communication range, victim localization and evacuation route planning. The combination of FM radio and Morse code is completely compatible with the current radio system equipped by rescue workers, and thus increases the possibilities of successful receiving and recognizing SOS messages. Our experiment result based on smartphone implementation shows that the proposed emergency communication service is cost effective and energy efficient with relatively large communication range.
A Privacy-Preserved Joint Group Time Scheduling Mechanism for Mobile Social Applications
(2013)
Chen, Yu-Jia
;
Lin, Chia-Yu
;
Wang, Li-Chun
;
交大名義發表
;
National Chiao Tung University
In this paper, we develop a privacy preserving mechanism for a scheduling service for a group of users, which can compute the joint available time based on users' calendar information. We also propose a weighted voting game with partially homomorphic encryption (WVGPHE) scheme to protect the privacy of users' calendar information as well as users' weight. Even with the privacy protection, our experimental results show that the proposed scheme is still very computational and bandwidth efficient enough to provide immediate group meeting in mobile communications environments.
A Proximity Sensor Based No-Touch Mechanism for Mobile Applications on Smart Phones
(2012-01-01)
Lin, Chia-Yu
;
Chen, Yu-Jia
;
Wang, Li-Chun
;
Tseng, Yu-Chee
;
電機工程學系
Smart phones with touch screens have become very popular and have changed our behaviors of using handsets. However, using touch screens is not safe for mobile phone users especially when they are driving cars. Thus, many applications using smart phones cannot be initiated because users who are driving the cars cannot easily touch the small icons on the screens of smart phones. To overcome this issue, we propose a proximity sensors based "no-touch" mechanism for smart phones by applying proximity sensors to initiate mobile applications without the need of touching the screen. We will discuss how to implement the proximity-sensors driven "no-touch" mechanism in Android platform and investigate its performance issues regarding detection accuracy and power consumption. Speech-oriented applications using the proposed "no-touch" mechanism on Android is also demonstrated in this paper.
Achieving Energy Saving with QoS Guarantee for WLAN using SDN
(2016)
Chen, Yu-Jia
;
Shen, Yi-Hsin
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
In recent years, the wireless local area networks (WLAN) access points (APs) are being deployed rapidly in the offices and the campuses to satisfy the quality of service (QoS) requirements such as network bandwidth. However, many empirical studies show that a large fraction of idle WLAN resources result in the significant energy losses. To reduce the energy consumption without violating the QoS requirement, we propose a QoS-aware AP energy saving mechanism using software defined network (SDN). We leverage the capability of the SDN controller to dynamically monitor the network condition information to estimate the network bandwidth requirement of the devices and then manage the network forwarding to provide seamless handover. Our experimental results show that the proposed scheme can effectively reduce the number of power-on WLAN APs while still providing QoS guarantee, such as network bandwidth and handover cost.
An Eavesdropping Prevention Problem When Repairing Network Coded Data from Remote Distributed Storage
(2013-01-01)
Chen, Yu-Jia
;
Liao, Chen-Hung
;
Wang, Li-Chun
;
交大名義發表
;
National Chiao Tung University
We consider the cloud storage systems with data stored in two geographically different datacenters for remote backup. In such system, inter-data center communication is established for data repair when storage nodes fail in the data center. Since the repairing data are transmitted over the Internet, the communication between the datacenters can become susceptible to eavesdropping. This problem is especially crucial in network coding-based distributed storage systems because more repair bandwidth and repair links are required, compared to conventional replication. In this paper, we show that remote repair bandwidth can be reduced by increasing storage per node and derive the tradeoff curves between remote repair bandwidth and storage. Moreover, we show that there exist another tradeoff for storage cost and reliability for different amount of remote and local storage nodes.
An Overflow Problem in Network Coding for Secure Cloud Storage
(2019-04-01)
Chen, Yu-Jia
;
Wang, Li-Chun
;
交大名義發表
;
電機工程學系
;
National Chiao Tung University
In this paper, we present the overflow problem of a network coding storage system (NCSS) when the encoding parameters and the storage parameters are mismatched. The overflow problem of the NCSS occurs because the network-coded encryption yields extended coded data, resulting in high storage and processing overhead. To avoid the overflow problem, we propose an overflow-avoidance NCSS scheme that takes account of security and storage requirements in both encoding and storage procedures. We provide the analytical results of the maximum allowable stored encoded data under the perfect secrecy criterion. The design guidelines to achieve high coding efficiency with the lowest storage cost are also presented.
Analytical Modeling of Read-Induced SET-State Conductance Change in a Hafnium-Oxide Resistive Switching Device
(2020-01-01)
Su, Po-Cheng
;
Jiang, Cheng-Min
;
Chen, Yu-Jia
;
Wang, Chih-Chieh
;
Li, Kai-Shin
A SET-state conductance change in a hafnium-oxide resistive switching memory cell due to repeated read events is investigated. We characterize a read-induced conductance change at different read voltages and SET-state conductance levels. Our result shows that the read-induced conductance degradation exhibits a two-stage evolution with the read pulse number. A SET-state conductance decreases slightly in the first stage and then follows inverse power-law dependence on the read number in the second stage. The power factor is an exponential function of a read voltage without regard to the SET-state conductance level, and the read pulse number at the transition of the two stages is related to a read voltage and conductance level. An analytical model to describe the two-stage conductance evolution is proposed. The parameters in the model are extracted from measurement data. Our model is verified by good agreement between the modeled and measured results in a wide range of read pulse number, read voltage, and SET-state conductance level.
Designing an anamorphic illumination system with an RTIR prism for a tilt-and-roll-pixel-type projector
(2020-04-20)
Chen, Yu-Jia
;
Pan, Jui-wen
;
光電系統研究所
;
Institute of Photonic System
A relay lens system design for a mini-projector with telecentric illumination is described. The reverse total internal reflection (RTIR) prism for angular magnification and lateral magnification is discussed in detail, and magnifications under different digital micromirror devices (DMD) are compared. The tilt-and-roll pixel (TRP) DMD chip (tilt angle is +/- 17 degrees) is the latest spatial light modulator, and the f-number of the illumination system is 1.71. Using the TRP DMD, the lateral magnification and the angular magnification for the RTIR prism can be increased by 3.77% and 8.73% over that obtainable using the conventional DMD chip (tilt angle is +/- 12 degrees). In order to solve for the angular magnification of an RTIR prism, the baffle is set at the aperture stop of the relay lens system. There is a trade-off between the efficiency and the contrast ratio with the baffle. When B (the position of the baffle) is at 0.11, the contrast ratio of the illumination system is 7590:1 and the efficiency is 57%. The spot size at the edge and corner of the DMD active area is controlled to be less than 250 mu m, and the optical distortion is less than 1%. (C) 2020 Optical Society of America
Deterministic Quality of Service Guarantee for Dynamic Service Chaining in Software Defined Networking
(2017-12-01)
Chen, Yu-Jia
;
Wang, Li-Chun
;
Lin, Feng-Yi
;
Lin, Bao-Shuh Paul
;
交大名義發表
In this paper, we present a systemic approach to provide deterministic delay guarantee for dynamic service chaining in software defined networking (SDN). The delay performance of service chaining in SDN is affected by signaling message exchange in control plane and packet transmissions in data plane, respectively. First, we develop an analytical method to characterize the delay performance of control plane when handling traffic with different priorities according to network calculus (NC) and queuing theory. Second, taking into account the estimated delay in control plane, we propose a novel service traversal mechanism to calculate the optimal traversal path for the service chain. We demonstrate that NC delay analysis can provide deterministic quality of service (QoS)-guaranteed service chaining for any specified delay requirements, whereas theoretical queueing delay analysis can only provide statistical QoS guarantee. In summary, the proposed NC delay analysis can help to understand the network design for a future delay sensitive Internet in which deterministic latency must be guaranteed.
Eavesdropping Prevention for Network Coding Encrypted Cloud Storage Systems
(2016-08)
Chen, Yu-Jia
;
Wang, Li-Chun
;
Liao, Chen-Hung
;
電機學院
;
College of Electrical and Computer Engineering
Network coding is an important cloud storage technique, which can recover data with small repair bandwidth and high reliability compared to the existing erasure coding and replication methods. However, regardless of which data recovery technique is used, the repaired data in a geographically distributed cloud storage system are easy to be eavesdropped at the transmission link between the local datacenter and its remote backup site. This kind of network security issue is called link eavesdropping in this paper. For a network coded cloud storage system, we propose a systematic design methodology to determine the important data recovery system parameters for any specified security level. Through analysis, we present the performance curves to relate the remote repair bandwidth and the number of coded data fragments. Consequently, all the important system parameters of a network coded data recovery system, including the number of storage nodes and the link capacity between the datacenter and the backup site, can be precisely designed for satisfying different security level requirements.
Effect of mechanical-strain-induced defect generation on the performance of flexible amorphous In-Ga-Zn-O thin-film transistors
(2016-12)
Liao, Po-Yung
;
Chang, Ting-Chang
;
Su, Wan-Ching
;
Chen, Yu-Jia
;
Chen, Bo-Wei
In this study, we investigate the effect of mechanical strain on the performance of flexible amorphous In-Ga-Zn-O (a-.InGaZnO) thin-film transistors. Drain current-gate voltage (ID-VG) and capacitance-voltage (C-V) transfer curves are measured to analyze the degradation behavior. The ID-VG characteristic exhibits a clear negative shift under mechanical strain regardless of the tension or compression state. In addition, the C-V characteristic curves show a leftward shift with extra distortion or stretching out under mechanical strain. This indicates that InGaZnO generates additional defects under this mechanical strain, a phenomenon that can be attributed to the generation of mechanical-strain-induced oxygen vacancies on the flexible a-InGaZnO TFTs. (C) 2016 The Japan Society of Applied Physics.
HiAuth: Hidden Authentication for Protecting Software Defined Networks
(2019-06-01)
Abdullaziz, Osamah Ibrahiem
;
Wang, Li-Chun
;
Chen, Yu-Jia
;
電機工程學系
;
Department of Electrical and Computer Engineering
Software defined networking (SDN) enables network function programmability for ease of configuration and maintenance, and also allows network administrators to change traffic rules on the fly. However, denial of service (DoS) attacks pose security challenges on the centralized control plane of SDN. Although the transport layer security (TLS) can help secure the control plane, it is computationally intensive, complex to configure, and not mandatory in OpenFlow protocol. In this paper, we present a lightweight authentication solution, called hidden authentication (HiAuth), to protect the SDN controller by hiding the identities of the forwarding devices into the control packets via efficient bitwise operations. HiAuth is the first to incorporate information hiding techniques into OpenFlow to provide security against DoS attacks. HiAuth exploits the IP identification field of IPv4 and the transaction identification field of OpenFlow in two authentication schemes. The experimental results show that HiAuth can effectively mitigate intruder DoS attacks and provide high undetectability to attackers.
Impact of Aggregation Factor on Delay Performance in Group-based Machine Type Communications
(2017-01-01)
Chen, Yu-Jia
;
Wang, Zi-Qi
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
This paper investigates the impact of request aggregation on delay performance in group-based machine type communications (MTC). To alleviate the network congestion caused by concurrent transmissions from massive MTC devices, group-based MTC with request aggregation are shown to be one of the effective schemes. In group-based MTC, the devices are grouped into clusters with a dedicated cluster head (CH) which aggregates the requests sent by the cluster members. Hence, the amount of concurrent transmissions for connection establishment to the base station (BS) can be reduced. However, how to determine the amount of aggregated requests in one CH-to-BS transmission, namely aggregation factor, is still an open issue. To this end, we formulate an optimal aggregation problem to minimize the request delay subject to a drop ratio constraint. Based on our analytical and simulation results, we present the performance curves to relate the aggregation factor and the request delay as well as the drop ratio. Consequently, we suggest the optimal aggregation factors for MTC applications requiring ultra-low latency and ultra-reliable delivery.
Improving Handover Performance in 5G mm-Wave HetNets
(2017-01-01)
Chen, Yu-Jia
;
Hsu, Tong
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
In future 5G communication systems, the mm-wave transmission is considered as a key solution to fulfill the growing demands in mobile traffic. To overcome the high propagation loss experienced at high frequencies, mm-wave transmission relies heavily on highly directional antennas. Because directional transmission is sensitive to position changes, the existing handover strategies which only consider the instantaneous received signal strength fails to provide robust connections for moving users. In this paper, we propose an improved handover strategy for mmwave mobile networks taking the connection robustness issue into account. The connection robustness is evaluated in terms of the effective beam coverage probability, which is defined as the probability that a user stays in the coverage area of the same beam after a certain time interval. We show that the proposed handover strategy can reduce handover frequency up to 35% with negligible throughput loss compared to the existing signal strength based scheme.
(Invited Paper) Handoff Delay Analysis in SDN-enabled Mobile Networks: A Network Calculus Approach
(2017-01-01)
Lin, Chun-Rong
;
Chen, Yu-Jia
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
With the great potential in flexible network provisioning adapted for various quality of service (QoS) requiremen ts, software-defined network (SDN) has been considered as one of the most promising network architectures in the next generation mobile networks. However, the rule management in SDN-enabled mobile networks becomes a challenging task due to rapid topology changes caused by high user mobility. One primary issue is how to handle the continuous cachemisses in the new routing path during a handoff process. To resolve the cache missing issue and reduce its handoff delay, different prefetching approaches have been proposed. However, the pre-installed rules in current prefetching approaches will incur extra delay in the core network, which cannot be ignored. In this paper, based on network calculus theory, we develop an analytical handoff delay performance model for different prefetching approaches in SDN-enabled mobile networks. The derived delay bounds of prefetching approach in different network environments are validated by simulations. We show that the presented network-calculus-based delay analysis methodology can be an effective and interesting analytical approach for evaluating ultra low delay communications systems in 5G wireless.
Learning-assisted Beam Search for Indoor mmWave Networks
(2018-01-01)
Chen, Yu-Jia
;
Cheng, Wei-Yuan
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
This paper proposes a learning-assisted beam search scheme for indoor millimeter wave (mmWave) networks with multi-base stations. Recently, directional antennas are often used to achieve the high data rates and compensate the high free-space loss in the mmWave frequency range. However, establishing reliable communication links with narrow beamwidth is a challenging task in indoor moving environments since the sector search space scales with device mobility and base station density. To tackle such an issue, we develop a multistate Q-learning approach that incorporates the base station selection into the beam selection process. By exploiting the radio environment data from ray tracing simulation, the proposed learning approach can enable fast and reliable beam selection for different indoor environments and mobility patterns. Simulation results show that the proposed scheme outperforms the beam search schemes based on the existing exhaustive search approach and the original Q-learning approach in terms of beam search latency, link outage times, and aggregated throughput.
Light-Induced Nanowetting: Erasable and Rewritable Polymer Nanoarrays via Solid-to-Liquid Transitions
(2020-08-12)
Lin, Kuan-Ting
;
Chen, Yu-Jia
;
Huang, Meng-Ru
;
Karapala, Vamsi Krishna
;
Ho, Jhih-Hao
Template wetting methods have been widely applied in the preparation of one-dimensional (1D) polymer nanomaterials. The pattern control using the template wetting methods, however, still remains a great challenge, mainly due to the nonselectivity of the polymers toward the environmental triggering. In this work, we present a facile light-induced nanowetting (LIN) method to fabricate patterned nanoarrays using anodic aluminum oxide (AAO) templates. Photoresponsive azobenzene-containing polymers (azopolymers) that exhibit light-induced reversible solidto-liquid transitions are used. Upon exposure to ultraviolet lights, the azopolymer chains can wet the nanopores of the AAO templates in a liquid state via capillary force. The azopolymer chains are then solidified by illuminating them with visible lights, resulting in the formation of azopolymer nanoarrays. Notably, using designed photomasks, the patterns of the nanoarrays can be ingeniously controlled with the characteristic of erasable and rewritable nanostructures.
Lightweight Authentication Mechanism for Software Defined Network using Information Hiding
(2016-01-01)
Abdullaziz, Osamah Ibrahiem
;
Chen, Yu-Jia
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
Software defined network (SDN) is an emerging network architecture which offloads the control logic of the network from the underlying forwarding devices to a centralized controller. This centralized control intelligence software defines the behavior of the network. However, the programmability and centralization of the SDN architecture introduce potential security concerns. In this paper, we first investigate the threats of denial of service (DoS) attacks on the SDN control channel. Then, we evaluate the impact of DoS by simulating a DoS attack against the network controller. Our results show that it is possible to exhaust the controller resources in the absence of an authentication mechanism. Finally, we propose a lightweight information hiding authentication mechanism to prevent DoS attacks in the SDN control channel.