Cheol-Sig Pyo

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Novel slot-shaped defected ground structures (DGSs) on the microstrip line are presented to provide a band-rejection property with an improved Q factor. Two different geometries (U-slot and V-slot) are investigated. U-slot and V-slot DGSs have simple shapes compared to the conventional DGSs, however, they provide more steep rejection characteristics. The Q(More)
This paper presents a low-power RF receiver/transmitter front-end for 2.4-GHz-band IEEE 802.15.4 standard in 0.18-mum CMOS technology. An RF receiver comprises a single-ended low-noise amplifier, a quadrature passive mixer, and a transimpedance amplifier. A current-mode passive mixer showing a very good 1/f noise performance is adopted to convert an RF(More)
To provide a more reliable link and deterministic delay for the mission-critical services, enhancement of the IEEE 802.15.4-2006 MAC specification was started in March 2008. The enhanced MAC specification offers three types of medium access control: Low Latency (LL), Time Slotted Channel Hopping (TSCH), and Distributed Synchronous Multi-Channel Extension(More)
Fog computing extends cloud-based computing concept to the edge of the network, thus enabling a breed of services and applications. Previous research topics on fog computing have significantly focused on the concepts and fundamentals of fog computing and its importance in the context of Internet of things (IoT) and Web of object (WoO). Recently, inspired by(More)
In a star network, the coverage of networking is limited by the transmission range of the device. After the initial deployment of the wide area monitoring network, the geographical environment may be changed and some place will be totally different to the times designed over 20 years ago. To keep infrastructure costs to a minimum, it is required to extend(More)
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