Browsing by Author "Cheng, E-Cheng"

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Energy-conserving always-on schemes for a mobile node with multiple interfaces in all-IP network
(2007)
Tsao, Shiao-Li
;
Cheng, E-Cheng
;
資訊工程學系
;
Department of Computer Science
In a heterogeneous overlay wireless network, a mobile node (MN) with multiple wireless interfaces can attach to various networks and obtains multiple IP addresses simultaneously. To allow correspondent nodes (CNs) to connect to an MN at anytime through any MN's IP address, an MN must keep its interfaces awake to receive incoming packets. Unfortunately, the previous studies indicate that power consumption of an MN with multiple interfaces poses a serious problem, even when interfaces are idle. This work presents two novel energy-conserving always-on schemes for an MN with multiple interfaces. These schemes only maintain one awake interface of an MN and turn off completely other interfaces of the MN to minimize its power consumption. By updating proper binding information on home agents (HAs), packets sent to the IP addresses associated with these turned-off interfaces can be received by the MN without packet loss.
PIANO: A power saving strategy for cellular/VoWLAN dual-mode mobiles
(2008-10-01)
Tsao, Shiao-Li
;
Cheng, E-Cheng
;
資訊工程學系
;
Department of Computer Science
The integration of cellular and VoIP over WLAN (VoWLAN) systems recently has attracted considerable interest from both academia and industry. A cellular/VoWLAN dual-mode system enables users to access a low-cost VoIP service in a WLAN hotspot and switch to a wide-area cellular system without WLANs. Unfortunately, cellular/VoWLAN dual-mode mobiles suffer the power consumption problem that becomes one of the major concerns for commercial deployment of the dual-mode service. In this study, we present a novel power saving mechanism, called PIANO (paging via another radio), for the integration of heterogeneous wireless networks, and further apply the proposed methods to implement a cellular/VoWLAN dual-mode system. Based on the proposed mechanisms, a dual-mode mobile can completely switch off its WLAN interface, only leaving the cellular interface awake to listen to paging messages. When a mobile receives a paging message from its cellular interface, it wakes up the WLAN interface and responds to connection requests via WLAN networks. Therefore, a dual-mode mobile reduces the power consumption by turning off the WLAN interface during idle, and can also receive VoWLAN services. Measurement results based on the prototype system demonstrate that the proposed methods significantly extend the standby hours of a dual-mode mobile.