Browsing by Author "Huang, Chung-Huei"

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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.
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.
Energy Conserving Packet Transmission Schemes for Video and Voice over WLAN
(2006)
Tsao, Shiao-Li
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Huang, Chung-Huei
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Lin, Tzu-Ming
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資訊工程學系
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Department of Computer Science
The design of packet transmission mechanisms of video and voice over wireless networks generally utilizes the characteristics of real-time data to improve the network performance, the energy efficiency of mobile devices, and etc. Unfortunately, WLAN medium access control (MAC) layer does not distinguish real-time and data packets during MAC frame transmission, and this design introduces network overheads and extra power consumption of video and voice over WLAN (V(2)oWLAN) stations (STAs). In this paper, we propose a transmission scheme to eliminate WLAN MAC acknowledgment frames of real-time packets dynamically in order to reduce the power consumption of V(2)oWLAN STAs and to improve the network utilization without sacrificing video and voice qualities. The proposed transmission scheme utilizes the WLAN multicasting method that does not require MAC acknowledgment, and the method thus can be implemented on the existing WLAN infrastructures by only software upgrades. Simulation results demonstrate that the proposed scheme improves the network utilization and the energy efficiency of V(2)oWLAN applications.