박세웅 교수

Low-power and lossy networks (LLNs) comprised of thousands of embedded networking devices can be used in a variety of applications, such as smart grid automated metering infrastructures (AMIs) and wireless sensor networks. Connecting these LLNs to the Internet has even greater potential, leading to the emerging concept of the Internet of Things (IoT). With the goal of integrating LLNs into IoT, the IETF has recently standardized RPL and 6LoWPAN to allow the use of IPv6 on LLNs. Although there al

Abstract Structural coloration is closely related to the progress of innovative optoelectronic applications, but the absence of direct, on‐demand, and rewritable coloration schemes has impeded advances in the relevant area, particularly including the development of customized, reprogrammable optoelectronic devices. To overcome these limitations, a digital laser micropainting technique, based on controlled thin‐film interference, is proposed through direct growth of the absorbing metal oxide laye

Selective laser sintering of metal nanoparticle ink is a low-temperature and non-vacuum technique developed for the fabrication of patterned metal layer on arbitrary substrates, but its application to a metal layer composed of large metal area with small voids is very much limited due to the increase in scanning time proportional to the metal pattern density. For the facile manufacturing of such metal layer, we introduce micropatterning of metal nanoparticle ink based on laser-induced thermocapi

In-band wireless full-duplex is a promising technologythat enables a wireless node to transmit and receive at the sametime on the same frequency band. Due to the complexity of selfinterferencecancellation techniques, only base stations (BSs) areexpected to be full-duplex capable while user terminals remain aslegacy half-duplex nodes in the near future. In this case, two differentnodes share a single subchannel, one for uplink and theother for downlink, which causes inter-node interference betwee

With the proliferation of emerging Internet of Things(IoT) devices and applications, mobility is becoming an integralpart of low-power and lossy networks (LLNs). However, most LLNprotocols have not yet focused on the support for mobility with anexcuse of resource constraints. Some work that do provide mobilitysupport fail to consider radio duty-cycling, control overhead,or memory usage, which are critical on resource-limited lowpowerdevices. In this paper, we introduce MAPLE, an asymmetrictransm

Jamming in wireless networks has advanced to be morestealthy and long-lasting with limited energy. Stealthy attackerstransmit short jamming signals to become less detectable with lessenergy, and yet powerful enough to ruin entire packet transmissionprocedures. In this article, we deal with three types of stealthyattacks: ‘Reactive jamming’, ‘Jamming ACK’, and ‘Fake ACK’attacks. These attacks are fatal to low-power and lossy wirelessnetwork (LLN) applications because they not only interfere withc

In this paper, we investigate two types of in-phase and quadrature-phase (IQ) data transfer methods for cloud multiple-input multiple-output (MIMO) network operation. They are termed “after-precoding” and “before-precoding”. We formulate a cloud massive MIMO operation problem that aims at selecting the best IQ data transfer method and transmission strategy (beamforming technique, the number of concurrently receiving users, the number of used antennas for transmission) to maximize the ergodic sum

In this work, we describe a simple and effective strategy for the fabrication of a thin silver (Ag) layer with a multiporous structure, showing a high electromagnetic interference shielding effectiveness (EMI SE). The Ag layer with a multiporous structure was produced by a simple spray coating of conductive ink containing porous Ag nanoparticles synthesized using a simple chemical reduction method in a wet medium, followed by a low-energy sintering process to develop the Ag layer with an interco

Selective laser sintering of metal nanoparticle ink is an attractive technology for the creation of metal layers at the microscale without any vacuum deposition process, yet its application to elastomer substrates has remained a highly challenging task. To address this issue, we introduced the shear-assisted laser transfer of metal nanoparticle ink by utilizing the difference in thermal expansion coefficients between the elastomer and the target metal electrode. The laser was focused and scanned

Device-to-device (D2D) communications are becomingpopular and promising owing to the proliferation of the Internet ofThings (IoT). Since existing D2D technologies only consider D2Dcommunications on either licensed band or unlicensed band, thispaper proposes a traffic steering scheme that jointly exploits threetypes of transmission links: Cellular links, D2D links on licensedband, and D2D links on unlicensed band. Our scheme aims to significantlyincrease system capacity while ensuring QoS for eac

To meet the increased demand of video-on-demand (VoD)services, peer-to-peer (P2P) mesh-based multiple video approaches have been recently proposed, where each peer is able to find a video segment interestedwithout resort to the video server. However, they have not considered the constraint of the server’s upload bandwidth and the fairness between upload and download amounts at each peer. In this paper, we propose a novel P2P VoD streaming system,named peer cache adaptation (PECAN) where each pee

본 논문은 유비쿼터스 사회를 실현하기 위해 준비되어야 할 핵심기술을 정의하고 관련 최근 동향을 살펴봄으로써 현재 기술수준과 실현가능성을 가늠해 보는 것을 목적으로 한다. 먼저 유비쿼터스 사회의 모형이라고 할 수 있는 유비쿼터스 지능공간(Ubizuitous Smart Space)개념과 이를 구현하기 위해 필요한 5가지 핵심기술분야를 설명한다. 특히 U 컴퓨팅 인프라 기술을 고도지능화 기술과 네트워크 기술로 구분하여 집중 조명하여 요소기술분야를 설명한다. 특히 U 컴퓨팅 인프라 기술을 고도지능화 기술과 네트워크 기술로 구분하여 집중 조명하여 요소기술들과 기술개발 동향을 소개한다. 한편 국가별로 추진되고 있는 유비쿼터스 기술로 대변되는 미래기술개발 정책과 추진체계를 고찰함으로써 한국의 경쟁력과 우열을 비교하고 최근에 꾸준히 추진되고 있는 주요 프로젝트들의 구체적인 개발성과를 소개한다. 마지막으로 유비쿼터스컴퓨팅사업의 추진 경험을 통해 미래사회 요구사항을 만족하기 위한 바람직한 통합연구 개

Wireless mesh networks (WMNs) provide high-speed backbone networks without any wired cable. Many researchers have tried to increase network throughput by using multi-channel and multi-radio interfaces. A multi-radio multi-channel WMN requires channel assignment algorithm to decide the number of channels needed for each link. Since the channel assignment affects routing and interference directly, it is a critical component for enhancing network performance. However, the optimal channel assignment

Silver nanowire (AgNW) networks have been adopted as a front electrode in Cu(In,Ga)Se2 (CIGS) thin film solar cells due to their low cost and compatibility with the solution process. When an AgNW network is applied to a CIGS thin film solar cell, reflection loss can increase because the CdS layer, with a relatively high refractive index (n ~ 2.5 at 550 nm), is exposed to air. To resolve the issue, we apply solution-processed ZnO nanorods to the AgNW network as an anti-reflective coating. To obta