• 대한산업공학회지
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• 제38권4호
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• pp.285-288
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• 2012

The connectivity-based reliable multicast MAC protocol was proposed for IEEE 802.11 wireless LANs and the formulae for the lower bounds of the multicast downlink throughput and the uplink throughput of the connectivity-based reliable multicast MAC protocol were derived in our previous study. We provide the tighter throughput lower bounds of the connectivity-based reliable multicast MAC protocol than the lower bounds presented in our previous study.

• Journal of information and communication convergence engineering
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• 제10권2호
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• pp.141-148
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• 2012

This paper presents a simple but efficient scheme incorporating a reputation-based approach and a cross-layer approach, called the SIM scheme, for maintaining reliable connectivity and high performance in ad-hoc wireless networks. The SIM scheme incorporates the following two things: an ad-hoc routing scheme with a reputation-based approach exploiting the game theory concept based on an evolutionarily stable strategy, and a cross-layer approach between the network layer and the transport layer employing a reputation-based approach.

• 대한산업공학회지
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• 제36권2호
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• pp.94-100
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• 2010

The reliable multicast MAC (Medium Access Control) protocol is needed to guarantee the recipients' nonerroneous reception of the multicast data frames, which can be transmitted by the AP (Access Point) in infrastructure mode IEEE 802.11 wireless LANs. Enhancing the BMMM (Batch Mode Multicast MAC) protocol, in the literature, the connectivity-based reliable multicast MAC protocol was proposed to reduce the RAK (Request for ACKnowledgement) frame transmissions and enhance the multicast MAC performance. However, the number of necessary RAK frame transmissions increases as the number of multicast recipients increases. To alleviate the problem of the larger number of RAK frame transmissions with the larger number of multicast recipients, we propose the clustering algorithm for partitioning the recipients into a small number of clusters, so that the recipients are connected each other within the same clusters. Numerical examples are presented to show the reliable multicast MAC performance improvement by the clustering algorithm.

• 한국식품영양학회지
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• 제29권6호
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• pp.1050-1057
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• 2016

SNS (Social network service) characteristics are perceived to simplify use. We carried out empirical studies on these parameters to observe the impact on the image of catering SNS online by word-of-mouth. The subjects of the study were as follows: 32.3% (392 persons) 19 years old, 67.7% (821 persons) over 19 years, 51.0% (619 persons) in their 20s, 22.1% (268 persons) in their 30s, 17.6% in their 50s, and 9.3% (112 persons) over 50 years. After verifying the hypothesis proposed that SNS characteristics perceived the ease of use, the significant factor identified in usability were connectivity Speed (${\beta}=0.213$), playfulness (${\beta}=0.246$), information (${\beta}=0.115$), and reciprocity (${\beta}=0.357$). Dual reciprocity had the most impact. It was observed that a longer impact of these significant factors improved the feel and fun of use. If SNS companies cater to, quick and easy, diverse, reliable and latest information, they can increase the ease of use, and availability, depending on the goals. Also, significant factors in the SNS features and online word of mouth was playfulness (${\beta}=0.312$), information (${\beta}=0.207$), reciprocity (${\beta}=0.066$) and perceived ease of use, and usefulness (${\beta}=0.293$), double playfulness had the maximum impact. These features provided more fun, reliable information, and could quickly deliver the latest information. The more the perceived usefulness, and ease of use, higher was the online word-of-mouth effect. SNS usage characteristics of connectivity Speed did not show any statistical significance in online word-of-mouth. Thus, catering businesses need to find ways to increase the ease of use, make the usefulness multifaceted, constantly checking the catering information on the SNS and ensuring to get the latest information is from diverse and reliable sources. This would increase the fun for the customer making the SNS to actively be utilized as a marketing tool.

• 한국정보과학회논문지:정보통신
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• 제34권1호
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• pp.33-40
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• 2007

멀티호밍은 하나의 기업 혹은 자율 시스템(AS, Autonomous System)이 둘 이상의 인터넷 서비스 제공업체(ISP, Internet Service Provider)로부터 인터넷 연결 서비스를 제공받는 메커니즘이다. 멀티호밍 메커니즘을 사용하는 AS는 망 내의 호스트들에게 여러 ISP를 통하여 좋은 성능과 신뢰성을 가지는 인터넷 연결을 제공할 수 있다. IPv6 멀티호밍에서는 멀티호밍 사이트가 하나의 ISP하의 연결에 문제가 발생하였을 경우 멀티호밍 사이트로 전송되어야 하는 패킷을 손실 없이 목적지로 전달할 수 있도록 하기 위하여 Non-direct EBGP(Exterior Border Gateway Protocol)를 통한 터널링 메커니즘이 정의되었다. 그러나 이 메커니즘의 경우 신뢰성 있는 인터넷 연결은 제공하지만 통신 경로가 최적화되지 못하는 문제점을 가진다. 본 논문에서는 IPv6 멀티호밍 환경에서 IPv6 확장 헤더를 사용함으로써 멀티호밍 사이트가 하나의 ISP와의 연결에 문제가 발생하였을 경우에 최적화된 경로를 통하여 신뢰성 있는 인터넷 연결을 제공할 수 있는 메커니즘을 제안한다.

• Steel and Composite Structures
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• 제19권2호
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• pp.263-275
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• 2015

This study presents conceptual information of newly optimized shapes and connectivity of the so-called outrigger truss system for modern tall buildings that resists lateral loads induced by wind and earthquake forces. In practice, the outrigger truss consists of triangular or Vierendeel types to stiffen tall buildings, and the decision of outrigger design has been qualitatively achieved by only engineers' experience and intuition, including information of structural behaviors, although outrigger shapes and the member's connectivity absolutely affect building stiffness, the input of material, construction ability and so on. Therefore the design of outrigger trusses needs to be measured and determined according to scientific proofs like reliable optimal design tools. In this study, at first the shape and connectivity of an outrigger truss system are visually evaluated by using a conceptual design tool of the classical topology optimization method, and then are quantitatively investigated with respect to a structural safety as stiffness, an economical aspect as material quantity, and construction characteristics as the number of member connection. Numerical applications are studied to verify the effectiveness of the proposed design process to generate a new shape and connectivity of the outrigger for both static and dynamic responses.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권9호
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• pp.3034-3055
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• 2014

Wireless Sensor Networks have extensively been utilized for ambient data collection from simple linear structures to dense tiered deployments. Issues related to optimal resource allocation still persist for simplistic deployments including linear and hierarchical networks. In this work, we investigate the case of dimensioning parameters for linear and tiered wireless sensor network deployments with notion of providing extended lifetime and reliable data delivery over extensive infrastructures. We provide a single consolidated reference for selection of intrinsic sensor network parameters like number of required nodes for deployment over specified area, network operational lifetime, data aggregation requirements, energy dissipation concerns and communication channel related signal reliability. The dimensioning parameters have been analyzed in a pipeline monitoring scenario using ZigBee communication platform and subsequently referred with analytical models to ensure the dimensioning process is reflected in real world deployment with minimum resource consumption and best network connectivity. Concerns over data aggregation and routing delay minimization have been discussed with possible solutions. Finally, we propose a node placement strategy based on a dynamic programming model for achieving reliable received signals and consistent application in structural health monitoring with multi hop and long distance connectivity.

• 한국전자파학회논문지
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• 제26권10호
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• pp.914-923
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• 2015

UAS(Unmanned Aircraft System)는 과거 군용으로 국한되어 활용되었으나, 최근 기술발전에 힘입어 점차 민간용 시장으로 확대되고 있으며, 그 시장 규모가 급격히 성장할 것으로 예상된다. 특히 초연결 시대의 UAS의 이용 형태는 넥스트(next) 5G 시스템 아키텍처에서 하나의 가능한 기반시설로 큰 역할을 할 것이다. UAS에서의 궁극적인 목표는 국가 공역 시스템(NAS: National Airspace System)으로의 통합 운용이며, 이를 위해 무인 비행체 제어를 위한 비업무용(non-payload) 주파수뿐만 아니라, 초연결시대의 다양한 활용분야에 필요한 업무용(payload) 주파수 확보가 중요한 요소이다. 이에 본 연구에서는 기존의 UAS 무선조정용 주파수의 분석과 비업무용 주파수 개발 연구동향 및 향후 UAS 주파수의 효율적 활용방안을 제안한다.

• 한국정보과학회논문지:정보통신
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• 제32권2호
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• pp.215-219
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• 2005

Ad-hoc 네트워크 내의 무선 이동 노드들은 일반적으로 전원 용량이 충분하지 않기 때문에 통신 중의 전원관리가 매우 중요하다. 이러한 전력 소모를 고려한 프로토콜로 MTPR, MBCR, MMBCR, CMMBCR 등이 제안되어 있으나, 전송 중 중간노드가 방전되어 링크가 단절되는 현상은 고려하지 못하고 있다. 따라서 경로의 연속성을 보장하기에는 미흡하다. 본 논문에서는 경로의 연속성을 증대하기 위한 세 가지 방안을 제안한다. 신호 세기가 임계치 이하인 경우 사전에 대체 경로를 설정하여 링크 단절에 대비한다. 전원용량이 임계치 이하로 떨어지는 경우에도 이를 미리 알려 대체 경로를 설정한다. 또한 멀티채널상의 중간 노드는 잔여 용량과 신규 링크 설정 요청에 필요한 전력을 비교하여 선택적으로 허락함으로써 중간 노드의 수명을 연장시키는 방안을 제안한다. 시뮬레이션 결과를 통하여 제안된 방안이 경로 연속성을 강화시키며, 신뢰적인 연결 관리에 의하여 지연 시간을 줄이는 성능 향상을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2218-2244
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• 2016

In this paper, we propose a hybrid routing scheme that utilizes location information to support reliable data transmission in mobile ad hoc networks. The proposed scheme determines and maintains routing path by considering the directionality and connectivity of nodes using grid zones and information on neighbor nodes. In addition, it generates alternative paths with consideration for node distance and reliability. To show the superiority of the proposed routing scheme, a performance evaluation was conducted using simulations. The performance evaluation results show that the proposed scheme offers faster and more reliable data transmission than the existing routing schemes, and the number of messages decreases by approximately 31% compared to the existing schemes on average.