Browsing by Author "Tsao, Shiao-Li"

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A Dynamic Load-Balancing Scheme for Heterogeneous Wireless Networks
(2014)
Tsao, Shiao-Li
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Wang, Chen-Wei
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Lin, Yun-Ciou
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Cheng, Ray-Guang
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資訊工程學系
Current heterogeneous wireless networks often overlap because of their complementary characteristics and the large deployment of various wireless access technologies. Mobile devices, which are equipped with multiple wireless interfaces, called multiple radio access technologies (multi-RATs) mobile stations (MSs), are also becoming increasingly popular. Therefore, common radio resource management (CRRM) has been proposed to coordinate heterogeneous radio resource allocations and improve the resource utilization of heterogeneous wireless networks. However, CRRM is an NP-hard problem, and low-complexity approaches for dynamic resource management are in high demand. In this paper, the resource request and allocation between multi-RAT MSs and heterogeneous wireless networks are modeled as a directed graph. Thus, the problem of searching for feasible radio resource allocations is simplified to finding trees in a directed graph. Based on the proposed model, a heuristic scheme can be used to find a feasible solution efficiently, and dynamically adjust the workload of heterogeneous BSs to accommodate new requests. Experimental results demonstrate that the heuristic scheme can reduce the request reject rate by 10%-55% compared with conventional approaches.
A Low-Latency Scanning with Association Mechanism for Real-Time Communication in Mobile WiMAX
(2012-10-01)
Chen, You-Lin
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Tsao, Shiao-Li
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資訊工程學系
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Department of Computer Science
In Mobile WiMAX, a mobile station (MS) scans neighboring base stations (BSs) before conducting handover. The MS may perform the association further, i.e., initial ranging, with neighboring BSs during scanning to obtain ranging parameters and/or service availability information for a potential handover to a BS and/or the selection of target BSs. However, the scanning with association scheme may introduce additional latency for handover. This study first evaluates the conventional scanning with association process, and then proposes a mechanism to reduce the association latency. The performance models of the proposed mechanism are presented and the accuracies of analytical models are verified by simulations. Results demonstrate that the proposed mechanism reduces the association latency by 61.9%-78.0% for audio services and 41.3%-65.4% for video services.
A Novel Search Scheme for Nonintrusive Load Monitoring Systems
(2012)
Lai, Yi-Sheng
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Chen, Yung-Chi
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Tsao, Shiao-Li
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Tsai, Tzung-Cheng
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資訊工程學系
A nonintrusive load monitoring (NILM) system analyzes the changes of voltage and current on an electrical circuit and can disaggregate the usage and power consumption of appliances on the same circuit loop according to different power consumption signatures of the appliances. An NILM system is regarded as one of the most important features for energy monitoring and management in a smart home and building. Advances in computing, communication and storage technologies further make an NILM system possible to accommodate a huge amount of power consumption signatures of appliances, and to detect appliances and/or appliance states through database search techniques. In this study, we propose a low-cost NILM system for a smart home and building to facilitate end users contributing the power consumption signatures of their appliances to a datacenter through confirmations or feedbacks of the NILM search. Based on those user contributed datasets, a new NILM search algorithm is then presented in this paper. To evaluate and compare the performance and accuracy of NILM search results by employing the proposed and existing approaches, an evaluation test-bed is established. The experimental results demonstrate that the proposed scheme outperforms the existing algorithms and can achieve 85% to 96% accuracy of appliance state detections.
A Practical Implementation Course of Operating Systems: Curriculum Design and Teaching Experiences
(2008)
Tsao, Shiao-Li
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資訊工程學系
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Department of Computer Science
The embedded software engineers are highly demanded in recent several years in order to support fast development of SoCs and embedded systems. These engineers need both strong hardware/software knowledge and hands-on experiences of system-level software. Unfortunately, the practical training of the system software development such as the OS design and implementation is often insufficient for computer science students in Taiwan recently. To minimize the gap between theory and practical implementation, a practical implementation course of OSs is thus developed in National Chiao Tung University. The course provides students trainings on the design details of modern OSs and comprehensive hands-on practices on OS implementation. In this paper, the curriculum and hands-on lab design, the teaching experiences and student feedbacks for the trial run are presented.
A Real-Time Road Traffic Information System based on a Peer-to-Peer Approach
(2008)
Yang, Ya-Chu
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Cheng, Chien-Ming
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Lin, Pei-Yun
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Tsao, Shiao-Li
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資訊工程學系
Conventional traffic information systems based on client-server approaches allow car drivers to navigate real-time road traffics, but the cost for maintaining the centralized traffic centers is high. On the other hand, decentralized traffic information systems that traffic conditions are exchanged between vehicles via inter-vehicle communication (IVC) significantly reduce the construction cost and efforts. Unfortunately, while the penetration of vehicles with such the system is insufficient, the systems suffer from problems to disseminate traffic conditions in disconnected vehicular ad-hoc networks. Therefore, we propose a novel road traffic information system which utilizes both IVC and infrastructure-based peer-to-peer communications. The system is organized as a two-tier hierarchical architecture where all vehicles broadcast traffic conditions over lower-tier vehicular ad-hoc networks. Moreover, parts Of vehicles with infrastructure communication facilities further form a high-tier peer-to-peer overlay and exchange traffic information and look-ups to redeem the dis-connectivity of the vehicular ad-hoc networks. Simulation results demonstrate that the proposed system performs well in terms of both delay for traffic information lookup and message exchanging overheads.
A Simple and Efficient Data Forwarding Mechanism In Wireless Relay Networks
(2009)
Chen, Wen-Tsuen
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Lin, Tzu-Ming
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Tsao, Shiao-Li
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資訊工程學系
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Department of Computer Science
Wireless relay network Is a low-cost solution for extending the service coverage and increasing the throughput of the conventional single-hop wireless network. By deploying a relay network, a base station (BS) can provide services to subscriber stations (SSs) through relay links. The functionality of a relay station (RS) is simpler than a BS, and RSs only forward packets between SSs, RSs and the BS without too much packet processing. However, current solutions require a RS to store and process the packet before it can determine the destination, and thus introduce extra processing and buffering overheads on the RS. This study proposes a simple and efficient forwarding scheme which multiplexes bursts to the SSs attached to the same access RS. By applying the proposed end-to-end burst switching mechanism, the RS merely checks the frame header and can decide the final destination without packet processing. The experiment results demonstrate the superior performance of the proposed scheme than other approaches.
A survey of energy efficient MAC protocols for IEEE 802.11 WLAN
(2011-01-15)
Tsao, Shiao-Li
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Huang, Chung-Huei
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資訊工程學系
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Department of Computer Science
In recent years, IEEE 802.11 wireless local area networks (WLANs) have been widely deployed, and more and more mobile devices have built-in WLAN interfaces. However, WEAN employs the carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol, which consumes a significant portion of the energy resources of a mobile device. Hence, minimizing the energy consumption of the WLAN interface in mobile devices has recently attracted considerable interest in both academia and industry. This article provides a survey and an experimental study of the energy consumption issues and energy-efficient technologies of the MAC protocol in IEEE 802.11 WLAN. (C) 2010 Elsevier B.V. All rights reserved.
Adaptive Lookup Protocol for Two-Tier VANET/P2P Information Retrieval Services
(2015-03-01)
Cheng, Chien-Ming
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Tsao, Shiao-Li
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資訊工程學系
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Department of Computer Science
Intelligent transportation system (ITS) services have attracted significant attention in recent years. To support ITS services, architecture is required to retrieve information and data from moving vehicles and roadside facilities in an efficient manner. A two-tier system that integrates low-tier vehicular ad hoc networks (VANETs) and a high-tier infrastructure-based peer-to-peer (P2P) overlay, which can achieve a high lookup success rate and low lookup latency for information retrieval, has been developed. However, conventional information lookups in the two-tier VANET/P2P system may introduce extra lookup messages and latencies because the lookup queries are simultaneously performed over the VANET/P2P networks. This paper proposes an adaptive lookup protocol for the two-tier VANET/P2P system to improve the efficiency of information retrieval. The proposed protocol uses a Bloom filter, which is a space-efficient data structure, to collect reachability information of road segments; therefore, adaptive routing of queries between low-and high-tier networks according to reachability probability can be employed. Simulations based on the SUMO traffic simulator and QualNet network simulator demonstrate that compared with the conventional two-tier lookup mechanism, the adaptive lookup protocol can reduce the lookup latency by 12%, reduce the P2P lookup overhead by 20%-33%, and achieve a high success rate in information lookups.
An Adaptive Routing Algorithm for Two-Tier Traffic Information System
(2012)
Lu, Kowen
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Cheng, Chien-Ming
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Tsao, Shiao-Li
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資訊工程學系
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Department of Computer Science
Intelligent Transportation Systems (ITSs) have attracted much attention recently. One of the most important services for ITSs is to provide real-time traffic information service. To reduce the deployment cost and achieve high service availability, decentralized approaches such as vehicular ad hoc network (VANET)-based or infrastructure-based peer-to-peer (P2P) traffic information systems were proposed. To further improve the success rate and lookup latency of traffic information lookups, a new two-tier traffic information system which integrates low-tier VANET and high-tier P2P overlay has been developed. However, conventional two-tier traffic information system may introduce extra routing overheads since the information lookups are broadcasted over two tier networks and introduce redundant lookup messages. This paper proposes an adaptive routing mechanism in the two-tier traffic information system to improve the efficiency of traffic information lookup. Simulation results demonstrate that the proposed adaptive scheme reduces the lookup latency and overhead while achieving the same lookup success rate compared with the conventional approach.
An Efficient Automatic Repeat Request Mechanism for Wireless Multihop Relay Networks
(2013-07-01)
Lin, Tzu-Ming
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Chen, Wen-Tsuen
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Tsao, Shiao-Li
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資訊工程學系
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Department of Computer Science
Recently, relay technology has been adopted to enhance the coverage and performance of wireless networks such as Worldwide Interoperability for Microwave Access and Long-Term Evolution Advanced (LTE-A). However, using relays to forward packets may induce more packet losses than traditional single-hop wireless networks because transmissions are conducted through multiple radio links. When there are lost packets, relay stations (RSs) decide whether to retransmit these packets with automatic repeat request (ARQ) strategies. We observe that an improper ARQ strategy increases latency, blocked packets, and workloads on the multihop relay network. This paper proposes a new relay ARQ (RARQ) scheme, providing efficient acknowledgement to reduce packet latency and the number of blocked packets with small workloads. We also propose an analytic model to evaluate the performance of the proposed mechanism. Simulation results have validated the proposed model and demonstrated that our ARQ scheme outperforms conventional approaches.
An Efficient Thermal Estimation Scheme for Microprocessors
(2014-01-01)
Huang, Pei-Shu
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Chen, Quan-Chung
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Huang, Chen-Wei
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Tsao, Shiao-Li
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資訊工程學系
In recent years, thermal management, which improves the reliability, performance, power leakage, etc. of modern microprocessors, has been the subject of numerous computer architecture and system software studies. To determine the detailed thermal distribution of a microprocessor is among the critical tasks for thermal management. However, because thermal modeling tools require considerable computation time and memory to simulate fine-grain thermal information, they may be unsuitable for dynamic thermal management and hardware implementation. This study proposes a novel model based on reduced resistance-capacitance (RC) networks for efficiently calculating the temperature of a microprocessor. The proposed model is compared with two existing thermal simulation tools, namely, HotSpot [1] and Temptor [2]. The experiment studies show that the results generated using the proposed model differ from those of the existing tools by only 0.5 to 1.5%. However, the suggested model can increase computation speeds by 5 to 9 times and 98 to 161 times that of Temptor and HotSpot, respectively. For the memory usage, the proposed model consumes merely 0.45% of the space used by the existing tools.
An end-to-end channel allocation scheme for a wireless mesh network
(2014-12-01)
Tsao, Shiao-Li
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Su, Jiun-Jang
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Huang, Kuei-Li
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Shih, Yung-Chien
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Tseng, Chien-Chao
Co-channel interference seriously influences the throughput of a wireless mesh network. This study proposes an end-to-end channel allocation scheme (EECAS) that extends the radio-frequency-slot method to minimize co-channel interference. The EECAS first separates the transmission and reception of packets into two channels. This scheme can then classify the state of each radio-frequency-slot as transmitting, receiving, interfered, free, or parity. A node that initiates a communication session with a quality of service requirement can propagate a channel allocation request along the communication path to the destination. By checking the channel state, the EECAS can determine feasible radio-frequency-slot allocations for the end-to-end path. The simulation results in this study demonstrate that the proposed approach performs well in intra-mesh and inter-mesh communications, and it outperforms previous channel allocation schemes in end-to-end throughput. Copyright (c) 2013 John Wiley & Sons, Ltd.
An energy-efficient transmission mechanism for VoIP over IEEE 802.11 WLAN
(2009-12-01)
Tsao, Shiao-Li
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Huang, Chung-Huei
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資訊工程學系
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Department of Computer Science
Voice over IP (VoIP) over WLAN (VoWLAN) is an important application for public and private WLANs. However, VoWLAN systems suffer from several technical challenges such as power consumption of a WLAN station (STA) and service capacity of an access point (AP), making the commercial deployment of a large-scale VoWLAN service problematic. This study presents a cross-layer and energy-efficient mechanism for transmitting VoIP packets over IEEE 802.11 WLAN. The proposed mechanism considers the characteristics of voice packets that call tolerate certain loss, and dynamically disables the medium access control (MAC) layer acknowledgement for voice packets. In doing so, the time and energy consumed to transmit and receive voice packets for an STA call be reduced. Simulation results demonstrate that the mechanism improves the energy efficiency of a VoWLAN STA and WLAN utilization without sacrificing voice qualities. Copyright (C) 2009 John Wiley & Soils, Ltd.
Analyzing OpenCL 2.0 Workloads Using a Heterogeneous CPU-GPU Simulator
(2017-01-01)
Wang, Li
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Tsai, Ren-Wei
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Wang, Shao-Chung
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Chen, Kun-Chih
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Wang, Po-Han
Heterogeneous CPU-GPU systems have recently emerged as an energy-efficient computing platform. A robust integrated CPU-GPU simulator is essential to facilitate researches in this direction. While few integrated CPU-GPU simulators are available, similar tools that support OpenCL 2.0, a widely used new standard with promising heterogeneous computing features, are currently missing. In this paper, we extend the existing integrated CPU-GPU simulator, gem5-gpu, to support OpenCL 2.0. In addition, we conduct experiments on the extended simulator to see the impact of new features introduced by OpenCL 2.0. Our OpenCL 2.0 compatible simulator is successfully validated against a state-of-the-art commercial product, and is expected to help boost future studies in heterogeneous CPU-GPU systems.
DATA INQUIRY SYSTEM AND METHOD FOR THREE-DIMENSIONAL LOCATION-BASED IMAGE, VIDEO, AND INFORMATION
(2009-10-08)
Tsao, Shiao-Li
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Lin, Cheng-Lung
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Lin, Kaun-Ju
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Chen, Hsin-Chung
This invention discloses a data inquiry system for three-dimensional location-based image, video, and information, which comprises a client device and a remote server. The client device provides space parameters and lens parameters to the remote server through a transmission module. The remote server determines a space inquiry range by the space parameter and lens parameter, inquires an object data of an object space position parameter at the space inquiry range, shows the object data in an image data displayed by the client device to facilitate users to identify the desired viewing object, and further inquires the object data and related image and/or video data.
Design and Evaluation of a Two-Tier Peer-to-Peer Traffic Information System
(2011-05-01)
Tsao, Shiao-Li
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Cheng, Chien-Ming
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資訊工程學系
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Department of Computer Science
Decentralized traffic information systems realize real-time traffic information services without the need for a server infrastructure. However, existing systems rely on either the vehicular ad hoc network or application-layer peer-to-peer protocols over a broadband wireless network suffering from low lookup success rate, high lookup latency, and maintenance overhead of the P2P network. This article proposes a two-tier VANET/P2P architecture that exploits both VANET and P2P technology. In the low tier, vehicles form a VANET via intervehicle communication to exchange traffic information. On top of the VANET, a portion of the vehicles further establish a P2P overlay through a broadband wireless infrastructure to mitigate the disconnectivity problems of the VANET. Simulation results demonstrate that the two-tier architecture can significantly improve the lookup success rate compared to the single-tier VANET systems while reducing lookup latency and maintenance overhead compared to the single-tier P2P systems.
Design and Implementation of a Home and Building Gateway with Integration of Non intrusive Load Monitoring Meters
(2012)
Lin, Ming-Chun
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Chen, Yung-Chi
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Tsao, Shiao-Li
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Tang, Wenshiang
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資訊工程學系
Home and building automation system is proposed not only for improving user comfort and safety but also for energy management of a house and building. However, conventional home and building automation system may not know detailed information of appliances and appliance states in a house and building so that some advanced services might not be able to provide. In this study, we integrate nonintrusive load monitoring (NILM) meters with a gateway so that the gateway can understand the power consumptions of appliances in a house and building and provide detailed information of appliances and their states. We design and implement the proposed gateway based on Open Service Gateway Initiative (OSGi) framework with the integration of NILM smart meters, sensors and actuators. Based on this infrastructure, we then present a data mining and event association algorithm to establish the relationships between appliances, sensors and actuators. The association and relationship information can be used to identify appropriate smart home and building services to specific houses and buildings, to locate appliances in a particular room and area, and to help an NILM system to collect the signatures of unknown appliances. Our prototype system demonstrates that the functionalities of a gateway and its services for a smart home and building can be significantly improved by integrating NILM meters.
Design and Implementation of a Skype Protocol Analyzer
(2013)
Cheng, Ray-Guang
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Tsai, Po-Yao
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Lin, Ping-Chen
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Lian, Chia-Liang
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Liu, Tse-Han
Proprietary protocols on the Internet often pose challenges for users and analysts to determine how secure the applications are or how easy private information can be accessed. This work presents a tool that processes packets generated by Skype and analyzes its proprietary implementation. The goal of the exercise is to determine how one may reverse engineer a proprietary protocol and obtain private information. The results demonstrate that a buddy-list of a target user can be obtained through the developed Skype Protocol Analyzer.
DESIGN ISSUES AND EXPERIMENTAL STUDIES OF WIRELESS LAN MESH
(2010-04-01)
Lin, Ying-Dar
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Tsao, Shiao-Li
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Chang, Shun-Lee
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Cheng, Shau-Yu
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Ku, Chia-Yu
Wireless mesh networking, as a low-cost and reliable technology for rapid network deployment, has attracted considerable attention from academia and standardization in the industry. The IEEE 802.11s standard defines a wireless LAN mesh using the IEEE 802.11 medium access control and physical layers, and is one of the most active standards with increasing commercial opportunities. This study presents the design and development of a WLAN mesh system conforming to the latest IEEE 802.11s draft amendment. Without costly hardware modifications, the proposed solution is a pure software extension for commercial off-the-shelf WLAN chipsets. This study constructs an experimental testbed, and evaluates issues such as the transmission reliability of mesh broadcast-type control messages and multichannel transmissions. Experimental results demonstrate that the delivery of mesh broadcast-type control messages, such as routing construction frames, using the multiple acknowledged unicast scheme improves mesh stability from an 86 to a 98 percent success ratio in a 16-node grid. Transmitting packets using a single radio interface switching between multiple channels reduces inter-flow interference and doubles the throughput in our testbed.
Detecting Users' Behaviors based on Nonintrusive Load Monitoring Technologies
(2013)
Chen, Yung-Chi
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Chu, Chun-Mei
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Tsao, Shiao-Li
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Tsai, Tzung-Cheng
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資訊工程學系
Conventional user behavior detection relies on a large amount of sensors and expensive monitoring devices. Moreover, the systems are usually intrusive and may suffer from deployment problems. In this paper, we design and implement an energy management system (EMS) consisting of a non-intrusive load monitoring (NILM) meter, gateway, server and mobile device. The NILM meter provides a non-intrusive and low-cost solution to recognize the states of appliances and to disaggregate the energy consumption of appliances in a house/building. Based on the proposed EMS, we further implement a data mining scheme to detect users' behaviors based on the usage patterns of appliances. A prototype system verifies our design concept and the simulation results show that the detection accuracy of users' behaviors is more than 80% for most of the activities.