Browsing by Author "Lai, TH"

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Minimum disc cover set construction in mobile ad hoc networks
(2005)
Sun, MT
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Ma, XL
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Yi, CW
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Yang, CK
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Lai, TH
The minimum disc cover set can be used to construct the dominating set on the fly for energy-efficient communications in mobile ad hoc networks. The approach used to compute the minimum disc cover set proposed in previous study has been considered too expensive. In this paper, we show that the disc cover set problem is in fact a special case of the general a-hull problem. In addition, we prove that the disc cover set problem is not any easier than the a-hull problem by linearly reducing the element uniqueness problem to the disc cover set problem. In addition to the known a-hull approach, we provide an optimal divide-and-conquer algorithm that constructs the minimum disc cover set for arbitrary cases, including the degenerate ones where the traditional alpha-hull algorithm incapable of handling.
Quorum-based asynchronous power-saving protocols for IEEE 802.11 ad hoc networks
(2005-02-01)
Jiang, JR
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Tseng, YC
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Hsu, CS
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Lai, TH
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資訊工程學系
This paper investigates the power mode management problem for an IEEE 802.11- based mobile ad hoc network (MANET) that allows mobile hosts to tune to the power-saving ( PS) mode. There are two major issues that need to be addressed in this problem: ( a) wakeup prediction and (b) neighbor discovery. The former is to deliver buffered packets to a PS host at the right time when its radio is turned on. The latter is to monitor the environment change under a mobile environment. One costly, and not scalable, solution is to time-synchronize all hosts. Another possibility is to design asynchronous protocols as proposed by Tseng et al. in [ 25]. In this paper, we adopt the latter approach and correlate this problem to the quorum system concept. We identify a rotation closure property for quorum systems. It is shown that any quorum system that satisfies this property can be translated to an asynchronous power-saving protocol for MANETs. Thus, the result bridges the classical quorum system design problem in the area of distributed systems to the power mode management problem in the area of mobile ad hoc networks. We derive a lower bound for quorum sizes for any quorum system that satisfies the rotation closure property. We identify a group of quorum systems that are optimal or near optimal in terms of quorum sizes, which can be translated to efficient asynchronous power-saving protocols. We also propose a new e-torus quorum system, which can be translated to an adaptive protocol that allows designers to trade hosts' neighbor sensibility for power efficiency. Simulation experiments are conducted to evaluate and compare the proposed protocols.
Special issue on mobile computing
(2004-05-01)
Tseng, YC
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Lai, TH
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Sadayappan, P
;
Lin, YB
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資訊工程學系