Wooguil Pak

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The duty cycle of a wireless sensor node is a key factor that determines the life time of a wireless sensor network. In general, sensor medium access control protocols reduce the duty cycle to achieve longer lifetime. However, we found out that their performance improvements substantially decrease under extremely low duty cycles (<0.1%). Our proposed W-MAC(More)
In a wireless sensor network, the routing control overhead is prohibitive because mostly many nodes are involved in routing. To overcome the overhead problem, tier based anycast protocol was proposed in (Kulkarni et al., 2006). However, it has a shortcoming of using much more energy compared to other competitors of deterministic routing protocols in(More)
Cognitive radio is a key to resolve scarcity of radio spectrum. To exploit unused spectrum bands, cognitive capable devices called secondary users should perform spectrum sensing; but need to vacate the band, when a licensee of the band, i.e. a primary user, appears. For seamless communication in this case, they should discover a free channel to switch to;(More)
In this paper, we propose a new centralized routing protocol named WRP that aims at maximizing the network lifetime. In WRP, the sink node is assumed to be with more capabilities and basically collects each node’s estimated wakeup time. This enables the sink node to estimate the wakeup times of all sensor nodes even if some of them are multi-hops away from(More)
* This work was supported by the KOSEF under grant 1999-1-30200-005-3. Abstract-To support various services in the current Internet, QoS routing was proposed. QoS routing finds a path to meet the requested QoS specification for a user, reserves network resource, thereby guaranteeing the QoS for the user. Many works have been done for QoS routing in an(More)
0140-3664/$ see front matter 2012 Elsevier B.V. A http://dx.doi.org/10.1016/j.comcom.2012.03.014 ⇑ Corresponding author. Tel.: +82 2880 8434; fax: + E-mail addresses: wgpak@netlab.snu.ac.kr (W. Pak 1 Part of this paper was presented at IEEE PIMRC’09 Although various medium access control (MAC) and routing protocols have been designed for WSNs (wireless(More)
For security of Android operating systems, permission-based solutions are one of popular approaches but still exposed to two problems. First, there is coarse-grained relationship between a permission and its associated methods. Second, mobile users do not have rights to control the permissions of their applications. To solve these problems, we propose(More)