• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권5호
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• pp.888-908
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• 2011

The increasing demand from passengers in vehicles to improve safety, traffic efficiency, and comfort has lead to the growing interest of Wi-Fi based vehicle-to-infrastructure (V2I) communications. Although the V2I system provides fast and cost-effective Internet connectivity to vehicles via roadside Wi-Fi access points (APs), it suffers from frequent handoffs due to the high mobility of vehicles and the limited coverage of Wi-Fi APs. Recently, the Mobile AP (MAP) platform has emerged as a promising solution that overcomes the problem in the V2I systems. The main advantage is that MAPs may yield longer service duration to the nearby vehicles that have similar mobility patterns, yet they provide smaller link capacities than the roadside APs. In this paper, we present a new association control technique that harnesses available connection duration as well as achievable link bandwidth in high-speed vehicular network environments. We also analyze the tradeoff between two association metrics, namely, available connection duration and achievable link bandwidth. Extensive simulation studies based on real traces demonstrate that our scheme significantly outperforms the previous methods.

• 한국인터넷방송통신학회논문지
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• 제9권4호
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• pp.87-97
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• 2009

A Mobile Ad hoc Network (MANET) is characterized by multi-hop wireless connectivity, frequently changing network topology with mobile nodes and the efficiency of the dynamic routing protocol plays an important role in the performance of the network. In this paper, the performance of five routing protocols for MANET is compared by using OPNET modeler: AODV, DSR, GRP, OLSR and TORA. The various performance metrics are examined, such as packet delivery ratio, end-to-end delay and routing overhead with varying data traffic, number of nodes and mobility. In our simulation results, OLSR shows the best performance in terms of data delivery ratio in static networks, while AODV has the best performance in mobile networks with moderate data traffic. When comparing proactive protocols (OLSR, GRP) and reactive protocols (AODV, DSR) with varying data traffic in the static networks, proactive protocols consistently presents almost constant overhead while the reactive protocols show a sharp increase to some extent. When comparing each of proactive protocols in static and mobile networks, OLSR is better than GRP in the delivery ratio while overhead is more. As for reactive protocols, DSR outperforms AODV under the moderate data traffic in static networks because it exploits caching aggressively and maintains multiple routes per destination. However, this advantage turns into disadvantage in high mobility networks since the chance of the cached routes becoming stale increases.

• Journal of Communications and Networks
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• 제10권4호
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• pp.422-429
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• 2008

Mobile peer-to-peer (P2P) systems have recently got in the limelight of the research community that is striving to build efficient and effective mobile content addressable networks. Along this line of research, we propose a new peer-to-peer file sharing protocol suited to mobile ad hoc networks (MANET). The main ingredients of our protocol are network coding and mobility assisted data propagation, i.e., single-hop communication. We argue that network coding in combination with single-hop communication allows P2P file sharing systems in MANET to operate in a more efficient manner and helps the systems to deal with typical MANET issues such as dynamic topology and intermittent connectivity as well as various other issues that have been disregarded in previous MANET P2P researches such as addressing, node/user density, non-cooperativeness, and unreliable channel. Via simulation, we show that our P2P protocol based on network coding and single-hop communication allows shorter file downloading delays compared to an existing MANET P2P protocol.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제11권4호
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• pp.9-17
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• 2007

Network Mobility basic support protocol (NEMO Basic) extends the operation of Mobile IPv6 to provide uninterrupted Internet connectivity to the communicating nodes of mobile networks. The protocol uses a mobile router (MR) in the mobile network to perform prefix scope binding updates with its home agent (HA) to establish a bi-directional tunnel between the HA and MR. This solution reduces location-update signaling by making network movements transparent to the mobile nodes (MNs) behind the MR. However, delays in data delivery and higher overheads are likely to occur because of sub-optimal routing and multiple encapsulation of data packets. To manage the mobility of the mobile network, it is important to minimize packet overhead, to optimize routing, and to reduce the volume of handoff signals over the nested mobile network. This paper proposes en aggregate router-assisted route optimization (ARARO) scheme for nested mobile networks support which introduces a local anchor router in order to localize handoff and to optimize routing. With ARARO, a mobile network node (MNN) behind a MR performs route optimization with a correspondent node (CN) as the MR sends a binding update message (BU) to aggregate router (AGR) via root-MR on behalf of all active MNNs when the mobile network moves. This paper describes the new architecture and mechanisms and provides simulation results which indicate that our proposal reduces transmission delay, handoff latency and signaling overhead. To evaluate the scheme, we present the results of simulation.

• 한국정보기술학회 영문논문지
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• 제9권2호
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• pp.15-27
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• 2019

This paper deals with a web-based public address system for conveying information for different institutions. An architecture for a Short Messaging Service (SMS) based public address (PA) system that can be programmed by an authorized mobile phone or device is proposed. This PA system will facilitate information transfer from heads of offices, managers, directors, and deans of the institutions to its constituents or unit area as well as enable postings of information with proper authentication and validation remotely. The system supports high priority messaging, allowing the conveyance of critical and time sensitive information. The mobility management support for the PA system will be based on the Hierarchical Mobile Internet Protocol version 6 (HMIPv6), hence, allowing for a seamless connectivity to the system. The major advantage of this proposed PA system as compared with the traditional electronic displays and bulletin boards is seamless mobility wherein the display devices can be programmed remotely by heads of the institutions and business organization. It also allows faster communication and immediate actions concerning the different institutions, organizations, and businesses, thus, ensuring high productivity.

• 지식경영연구
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• 제24권4호
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• pp.131-152
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• 2023

스마트관광 도시의 핵심 분야 중 하나인, 스마트 모빌리티는 개인형 교통수단인 공유 자전거, 공유 킥보드를 비롯해 공유 자동차 서비스, 스마트교통 인프라 등 ICT 기술을 기반으로 진보된 모든 수단과 서비스를 포함하며, 기존 교통수단의 한계를 극복하고 사람과 물자의 이동을 개선한다. 관광객에게는 관광지 간 이동 시 저렴하고 이용하기 쉬운 교통수단으로 활용될 뿐만 아니라, 관광 경험 그 자체가 되어 여행의 질을 향상시키는 역할도 한다. 이 연구는 스마트 모빌리티의 관광적 측면을 포함한 '스마트관광 모빌리티'를 '정보통신기술을 기반으로 뛰어난 연결성을 갖추고, 공익성을 가지고 있으며, 스마트관광 도시에서 거주민과 관광객 모두가 교통수단으로 사용함과 동시에 관광 경험 그 자체가 될 수 있는 모빌리티'로 정의하였다. 그리고 관련 산업의 범위를 전문가 델파이 조사를 기반으로 규명하고, 스마트관광도시에서 어떤 경제적 파급효과를 낳는지 파악하고자 했다. 구체적으로, RAS 기법과 입지계수법을 활용하여 산업연관표를 업데이트하고, 스마트관광 모빌리티에 대한 투자 증대가 서울시의 전 산업에 미치는 영향을 살펴보았다. 그 결과, 2022년 한 해 동안 예정된 서울시의 스마트관광 모빌리티에 대한 약 28억 원 규모의 투자로 인해 전 산업에 걸쳐 약 41억 4천만 원 이상의 생산유발효과가 창출될 것으로 추정되었으며, 이로 인해 약 16억 6천만 원의 소득유발효과, 약 36억 1천만 원의 부가가치유발효과, 그리고 약 54명을 위한 일자리가 창출될 것으로 예상되었다. 이러한 결과를 통해 스마트관광 모빌리티가 첨단기술과 관광·운송 서비스의 단순한 결합이 아니며, 도시 내·외부의 다양한 산업과 이해관계를 연계하는 생태계적 관점에서 발전해야함을 강조한다.

• 한국시뮬레이션학회논문지
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• 제15권3호
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• pp.87-91
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• 2006

이동통신이 생활화됨에 따라 유선망에서 사용하고 있는 초고속 인터넷을 무선망에서도 사용하고자 하는 욕구가 증가하게 되었으며 기존 WLAN(Wireless Local Area Network)시스템에서 커버리지 제한 문제와 단말의 이동성을 제공해주지 못하는 단점을 보안하고, 이동통신 시스템에서 고가의 통신요금 문제를 해결하기 위해 WMAN(Wireless Metropolitan Area Network) 표준이 새롭게 등장하였다. IEEE 802.16 계열의 WMAN 표준은 다양한 PHY 계층(SC, SCa, OFDM OFDMA)을 수용할 수 있는 MAC 표준과 단말의 이동성을 지원해주는 MAC 표준을 규정하고 있어서 차기 무선 인터넷에서 중요한 위치를 차지 할 것으로 보인다. 본 논문에서는 VoIP 서비스를 IEEE 802.16d에서 규정하고 있는 4가지 서비스 중 UGS 서비스 형태로 효과적으로 스케줄링 할 수 있는 상향링크 ON/OFF Grant 알고리즘을 제안하고 제안된 알고리즘이 규격에서 정의하는 기존의 방식과 참고문헌의 방식을 이용하여 서비스하는 것보다 VoIP 사용자의 평균 지연시간과 상향링크 자원 활용 측면에서 우수함을 NS-2 시뮬레이션을 통해 제시한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.329-329
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• 2016

Large-area graphene films produced by means of chemical vapor deposition (CVD) are polycrystalline and thus contain numerous grain boundaries that can greatly degrade their performance and produce inhomogeneous properties. A better grain boundary engineering in CVD graphene is essential to realize the full potential of graphene in large-scale applications. Here, we report a defect-selective atomic layer deposition (ALD) for stitching grain boundaries of CVD graphene with ZnO so as to increase the connectivity between grains. In the present ALD process, ZnO with hexagonal wurtzite structure was selectively grown mainly on the defect-rich grain boundaries to produce ZnO-stitched CVD graphene with well-connected grains. For the CVD graphene film after ZnO stitching, the inter-grain mobility is notably improved with only a little change in free carrier density. We also demonstrate how ZnO-stitched CVD graphene can be successfully integrated into wafer-scale arrays of top-gated field effect transistors on 4-inch Si and polymer substrates, revealing remarkable device-to-device uniformity.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.765-766
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• 2008

In this paper, It has been emphasized of important path access during transmit of node when each node transmit broadcast service which one's of new MANET (Mobile Ad hoc Networks) of autonomy and mobility network structures. It has proposed analysis methods are hierarchical path structure of transmit which experience context aware through confidence to network connectivity alone as issue which can be reduce duplicate of beam forming on networks and maintenance one's of method got to optimized of transmission network that status information of context awareness using ad hoc ODDMRP(Ontology Doppler effect Dynamic Multicast Routing Protocol) path method.

• 한국정보시스템학회지:정보시스템연구
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• 제16권2호
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• pp.69-91
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• 2007

The mobile computing environment has already matured and mobile services are activated throughout many industries. In the following years, these changes are expected to evolve into a ubiquitous computing environment. In the meantime, whether newly developed information technologies will thrive or diminished depends on user's intention to adopt them. Hence, the necessity of user-centered research considering ubiquitous computing in mobile computing environment is obvious. This study, thus, investigated ubiquitous factors in various literature related to ubiquitous computing and technology acceptance and it proposes a research model of the ubiquitous factors affecting user's intention to use mobile services, in terms of meaning(connectivity, mobility), service(contextual offer), compatibility(compatibility), and infrastructure(privacy, truth). The proposed model is expected to help both researchers and practitioners extend their understanding about the ubiquitous factors in mobile computing environment