Browsing by Author "Wu, Quincy"

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A Monte Carlo Method for Estimating the Extended All-terminal Reliability
(2008)
Huang, Shiang-Ming
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Wu, Quincy
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Tsai, Shi-Chun
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資訊工程學系
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Department of Computer Science
Designing a network with optimal deployment cost and maximum reliability considerations is a hard problem, especially when the all-terminal reliability is required. For efficiently finding out an acceptable solution, Genetic Algorithms (GAs) have been widely applied to solve this problem. In these GAs, the reliability values could be calculated in their objective functions. In year 2002, an extended network reliability model was proposed which considers the connection important level between each pair of nodes. This paper proposes an approximation algorithm based on Monte Carlo simulation for the new network reliability model. This approximation algorithm can be integrated into GAs to solve the optimal cost reliable network design problem under the extended model.
A Survey of NAT Behavior Discovery in VoIP Applications
(2011-03-01)
Hunag, Shiang-Ming
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Wu, Quincy
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資訊工程學系
;
Department of Computer Science
Because of the foreseeing depletion of Internet Protocol (IP) addresses, Network Address Translation (NAT) is ubiquitously deployed to allow hosts to connect to the Internet through a single shared public IP address, which is a popular approach in deploying wireless local area network (WLAN). Although NAT proves to work well with traditional client/server applications, its existence and non-standard behaviors are the major problem which cripples voice over IP (VoIP) applications. In addition to some efforts which attempt to devise complicated protocols to tackle all NAT varieties, there are also efforts in Internet communities trying to standardize the behaviors of NAT. Therefore, it becomes crucial for a network device to discover the existence of NAT in its subnet and to determine the NAT behaviors, so that it can choose the optimal NAT traversal mechanisms to apply. In this paper, we surveyed the divergent NAT behaviors and then proposed a simplified NAT behavior discovery approach which is more suitable for VoIP applications. The proposed approach can reduce the call establishment time of VoIP applications, which is useful in scenarios where VoIP devices are administrated within a specific domain, e.g., 3G cellular networks.
Modeling prepaid application server of VoIP and messaging services for UMTS
(2007-05-01)
Sou, Sok-Ian
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Lin, Yi-Bing
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Wu, Quincy
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Jeng, Jeu-Yih
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資訊工程學系
Universal mobile-telecommunication system supports IP multimedia services through the IP multimedia core-network subsystem (IMS). This paper proposes a prepaid application server (PAS) to handle both the prepaid calls and messaging services in the IMS. When both voice and messaging are simultaneously offered, a potential problem is that the delivery of a message during a call may result in force-termination of that call due to credit depletion. To address this issue, we describe a strategy to determine if a prepaid message can be sent out during a call session. We propose an analytic model to investigate the performance of this strategy. This paper provides guidelines to select appropriate input parameters for the PAS.
SIP mobility and IPv4/IPv6 dual-stack supports in 3G IP multimedia subsystem
(2006-08-01)
Huang, Shiang-Ming
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Wu, Quincy
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Lin, Yi-Bing
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Yeh, Che-Hua
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資訊工程學系
In the Universal Mobile Telecommunications System (UNITS), session initiation protocol (SIP) and IPv6 are the default protocols for IP multimedia core network subsystem (IMS). However, a user equipment (UE) may not be allowed to roam or hand off from UNITS to a private-lPv4 GPRS network. In this paper, we utilize SIP mobility and an automatic IPv6 tunneling mechanism, called Teredo, to support roaming/handoff of a UE between different networks. We have developed the first non-commercial Linux-based Teredo mechanism, and compared our solution with other Teredo implementations in the public domain. Our study indicates that our solution can reduce the tunneling overhead and transmission delay over two other implementations by 44-74%. Copyright (C) 2006 John Wiley & Sons, Ltd.