Browsing by Author "Wu, Q"

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A mobile service platform using proxy technology
(2006-02-01)
Chen, MF
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Lin, YB
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Rao, HCH
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Wu, Q
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資訊工程學系
This paper proposes iMobile, a proxy-based platform for developing mobile services for various mobile devices and wireless access technologies. iMobile acts as a message gateway that allows mobile devices to relay messages to each other through various protocols on different access networks. It allows mobile devices to access internet services, corporate databases and to control various network devices. iMobile implements three key abstractions: dev-let, info-let and app-let. An info-let provides abstract view of information space. An app-let implements service or application logic by processing information from various info-lets. A dev-let receives and sends messages through any particular protocols for mobile devices. The let engine supports user and device profiles for personalization and transcoding, and invokes proper app-lets and info-lets to answer requests from a dev-let. The Mobile modular architecture allows developers to write device drivers, information access methods and application logic independently from each other. Copyright (c) 2005 John Wiley & Sons, Ltd.
Development and deployment of IPv6-based SIP VoIP networks
(2005)
Chen, WE
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Wu, Q
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資訊工程學系
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Department of Computer Science
This paper presents an IPv6-based SIP VoIP network deployed in Taiwan. This deployment project is supported by N1CI IPv6 R&D Division. The major contributions of this paper are exercising the ENUM deployment on IPv6 SIP network, developing the IPv6 SIP User Agent and the IPv6 SIP Analyzer.
Enhancing teredo IPv6 tunneling to traverse the symmetric NAT
(2006-05-01)
Huang, SM
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Wu, Q
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Lin, YB
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資訊工程學系
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Department of Computer Science
By tunneling IPv6 packets over IPv4 UDP, Teredo supports IPv4/IPv6 dual-stack nodes in private IPv4 networks behind Network Address Translation (NAT) to access IPv6 networks. However, the current Teredo protocol does not work with symmetric NAT. This letter proposes SymTeredo, an extension of Teredo with capability to traverse the symmetric NAT. Our extension preserves the Teredo architecture, and offers backward compatibility with the original Teredo protocol.
Prepaid mechanism of VoIP and messaging services
(2005-01-01)
Son, SI
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Wu, Q
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Lin, YB
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Yeh, CH
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資訊科學與工程研究所
Session Initiation Protocol (SIP) is used for Voice over IP (VoIP) signaling and call control. Billing mechanisms for messaging and VoIP are typically deployed for postpaid services. Prepaid mechanisms for SIP-based VoIP calls toward Public Switched Telephone Network (PSTN) are seldom discussed. In this paper, we propose a prepaid mechanism that can simultaneously process messaging and VoIP calls. This prepaid mechanism is implemented in a VoIP platform developed under National Science & Technology Program for Telecommunications (NTP). Unlike previous VoIP prepaid approaches which require modifications to endpoints, our mechanism can be easily integrated to a VoIP platform without modifying existing network components.
The approximability of the weighted Hamiltonian path completion problem on a tree
(2005-09-05)
Wu, Q
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Lu, CL
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Lee, RCT
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生物科技學系
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Department of Biological Science and Technology
Given a graph, the Hamiltonian path completion problem is to find an augmenting edge set such that the augmented graph has a Hamiltonian path. In this paper, we show that the Hamiltonian path completion problem will unlikely have any constant ratio approximation algorithm unless NP = P. This problem remains hard to approximate even when the given subgraph is a tree. Moreover, if the edge weights are restricted to be either 1 or 2, the Hamiltonian path completion problem on a tree is still NP-hard. Then it is observed that this problem is strongly NP-hard, so it does not have any fully polynomial-time approximation scheme (FPTAS) unless NP = P. When the given tree is a k-tree, we give an approximation algorithm with performance ratio 1.5. (c) 2005 Elsevier B.V. All rights reserved.
Tunneling IPv6 through NAT with Teredo mechanism
(2005)
Huang, SM
;
Wu, Q
;
Lin, YB
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資訊工程學系
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Department of Computer Science
Teredo is a service that enables hosts located behind one or more IPv4 NATs to obtain IPv6 connectivity by tunneling packets over IPv4 UDP Under the national IPv6 deployment project in Taiwan, we developed the first Linux-based Teredo service in 2003. In this paper we explain how IPv6 candidates located behind NATs can enlist the help of "Teredo servers" and "Teredo relays" to learn their "global addresses" and to obtain connectivity, and how clients, servers and relays can be organized in Teredo networks. We also describe in details our strategies for implementing Teredo server and Teredo relay under Linux, and show the performance of different Teredo implementations in public domain.