Browsing by Author "Sung, Ya-Chin"

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Effects of the EAPOL, timers in IEEE 802.1X authentication
(2007-06-01)
Sung, Ya-Chin
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Lin, Yi-Bing
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資訊工程學系
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Department of Computer Science
This paper studies IEEE 802.1X authentication for WLAN and cellular integration. In the IEEE 802.1X standard, several timeout timers are defined for message exchanges in the EAPOL protocol, where the same fixed value is suggested for these timeout timers. We observe that the delays for the EAPOL message exchanges may significantly vary. A modeling study is performed to tune the values of individual timers to yield better performance than that for the identical timeout period setting. Our study provides guidelines to select appropriate timeout values for IEEE 802.1X operation.
IPsec-Based VoIP Performance in WLAN Environments
(2008-11-01)
Sung, Ya-Chin
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Lin, Yi-Bing
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資訊工程學系
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交大工研院聯合研發中心
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Department of Computer Science
The Third-Generation Partnership Project (3GPP) specifies 3G-WLAN interworking that lets mobile stations (MSs) access 3G networks via WLAN-based packet data gateways (PDGs). The specification mandates that packets delivered between an MS and a PDG should be protected by IPsec. This article studies IPsec-based VoIP performance (in terms of throughput, packet loss rate, latency, and jitter) in the 3G-WLAN integration environment. The study is designed to provide guidelines for selecting appropriate system parameter values for VoIP over WLAN.
NCTU-VT: a freeware for wireless VoIP performance measurement
(2012-03-01)
Sung, Ya-Chin
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Lin, Yi-Bing
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Liou, Ren-Huang
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Shieh, Lon-Fon
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資訊工程學系
Voice over IP (VoIP) is a promising low-cost voice communication over the wireless IP network. To provide satisfactory VoIP services, the Quality of Service (QoS) of the wireless network should be guaranteed. This paper proposes a VoIP performance measurement freeware called NCTU VoIP Testing Tool (NCTU-VT). We compare NCTU-VT with two commercial tools SmartVoIPQoS and IxChariot in terms of packet loss, latency, and Mean Opinion Score (MOS) of the VoIP sessions in Wi-Fi network. Our study indicates that these three tools can accurately measure VoIP performance in Wi-Fi environment. Copyright (c) 2010 John Wiley & Sons, Ltd.