• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.42-49
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• 2017

지연/분열 허용 네트워크는 간헐적인 통신링크 단절, 높은 전송 에러율와 같은 행성 간 통신에서 마주하는 주된 문제점들을 해결할 주된 기술로 여겨진다. 행성 간 통신에서 종단간 연결성이 보장되지 않아 간헐적으로 통신링크가 단절되면 길고 일정하지 않은 시간 지연과 정보 손실이 발생하고, 따라서 종단간 연결성을 요구하는 인터넷 프로토콜은 행성 간 통신에 적합하지 않다. Store-and-forward 메시지 전송 방식을 따르는 지연/분열 허용 네트워크는 행성 간 통신에서 종단간 연결성이 보장되지 않아 발생하는 문제점을 해결할 수 있다. 본 논문에서는 지구 기지국-지구 위성-달궤도선-달탐사체로 구성된 3-hop 릴레이 우주통신 환경에 지연/분열 허용 네트워크 개념을 적용한 통신 모델을 제시하며, ONE 시뮬레이터를 이용한 실제 우주통신환경 모델링 및 성능 분석을 통해, 안정적인 메시지 전송을 보장하는 최적의 메시지 수명, 버퍼 공간 및 메시지 분할 방법을 제시한다.

• 한국정보통신학회논문지
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• 제18권1호
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• pp.201-209
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• 2014

본 논문에서는 애드혹 네트워크에서 협력통신을 위한 이동노드 간 연결을 최대화하는 유전 알고리즘을 제안한다. 일반적으로 네트워크에서 이동노드의 이동량이 증가하면 노드 연결을 위한 계산량은 급격히 늘어나게 된다. 본 논문에서는 밀집도가 높은 네트워크에서 적정한 시간 내에 최적의 노드 연결을 위한 유전 알고리즘을 제안하며, 효율적인 검색을 위해 유전 알고리즘의 효과적인 이웃해 생성 동작을 제안한다. 제안된 알고리즘은 최대 노드 연결 수와 실행시간 관점에서 성능을 평가하며, 평가 결과에서 제안된 알고리즘이 기존의 알고리즘들에 비해 성능이 우수함을 보인다.

• 한국통신학회논문지
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• 제40권9호
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• pp.1767-1775
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• 2015

무선 센서 네트워크는 다양한 응용 서비스에 이용이 가능한 네트워크이다. 다양한 응용 서비스에 따라서 서비스에서 요구하는 네트워크 전송량은 매우 다양하다. 특히 무선 센서 네트워크에서는 센서 노드의 에너지 소모를 줄이고 통신 효율성을 높이기 위해서 다양한 토폴로지 제어 방법들이 제시되어 왔다. 이러한 토폴로지 제어 방법들은 대부분 통신의 효율성 측면에서 연구가 되어왔기 때문에 실제 응용 서비스에서 요구되는 데이터 전송량을 만족시키지 못하는 문제점이 있다. 본 논문에서는 이러한 문제를 해결하기 위해서 응용 서비스에서 요구하는 데이터 전송량을 만족시킬 수 있도록 하는 토폴로지 제어 알고리즘을 제시하였다.

• 정보와 통신
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• 제34권2호
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• pp.12-19
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• 2017

The LED technology advancement introduce cuttingedge technology on Internet of Things (IoT) to connect the physical world to the digital realm, using digital smart lighting infrastructure called Internet of light (IoL). This paper proposes an Integrated IoT agent on networked smart LED lighting controller called IoL Filed Gateway using lighting infrastructure in which a lighting system that can connect to a network and can be monitored and controlled from a centralized system or via the cloud. The IoL Field Gateway defines new world of smart connected intelligence, lighting can become an integral and responsive part of everyday human life environments. The proposed connected lighting gateway uses the concept of multi-hop ad hoc network using visible light communication (VLC) with RF wireless technologies and Wired PLC (Power Line Communication). This connectivity and intelligence integrated into LED-based luminaires form the backbone of smart buildings and cities and make the Internet of Things (IoT) vision feasible and enables the lighting administrator can control numerous lightings easily and visitors can get visual information from the lightings with their smart devices. The proposed IoL gateway design is emulated on Arduino based HW platform with VLC, RF, and PLC connectivity and evaluated with four sensor interface.

• Asia pacific journal of information systems
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• 제26권4호
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• pp.489-508
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• 2016

Growth in the use of mobile commerce services (MCS) as an enabler to conduct business more effectively has been phenomenal. Technology acceptance model (TAM) has been applied in different contexts to examine a wide range of information technology. As more and more companies are finding ways to utilize MCS, an important issue is to understand what factors will affect the decisions of consumers in adopting the services. Based on TAM with two additional groups of external factors (i.e., service-related factors [ubiquitous access and contextual service] and technology-related factors [perceived security risk and network connectivity]) that are theoretically justified to affect both perceived usefulness and perceived ease of use, which are also considered, a research model for the investigated technology acceptance was developed and empirically examined. The major results of this study are as follows. First, ubiquitous access affects perceived usefulness and perceived ease of use. Contextual service affects perceived usefulness. Second, perceived security risk affects perceived usefulness and perceived ease of use. Finally, network connectivity affects perceived usefulness and perceived ease of use.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2009년도 학술논문요약집
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• pp.186-186
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• 2009

The characterization strategy of fracture networks are classified into a deterministic or statistical characterization according to the type of required information. A deterministic characterization is most efficient for a sparsely fractured system, while the statistics are sufficient for densely fractured rock. In this study, the ensemble mean and variability of the effective connectivity is systematically analyzed with various density values for different network structures of a power law size distribution. The results of high resolution Monte Carlo analyses show that statistical characteristics can be a necessary information to determine the transport properties of a fracture system when fracture density is greater than a percolation threshold. When the percolation probability (II) approaches unity with increasing fracture density, the effective connectivity of the network can be safely estimated using statistics only (sufficient condition). It is inferred from conditional simulations that deterministic information for main pathways can reduce the uncertainty in estimation of system properties when the network becomes denser. Overall results imply that most pathways need to be identified when II < 0.5 statistics are sufficient when II $\rightarrow$ 1 and statistics are necessary and the identification of main pathways can significantly reduce the uncertainty in estimation of transport properties when 0.5$\ll$1. It is suggested that the proper estimation of the percolation probability of a fracture network is a prerequisite for an appropriate conceptualization and further characterization.

• Journal of information and communication convergence engineering
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• 제13권1호
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• pp.7-14
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• 2015

In a multi-hop wireless network, connectivity is determined by the link that is established by the receiving signal strength computed by subtracting the path loss from the transmission power. Two path loss models are commonly used in research, namely two-ray ground and shadow fading, which determine the receiving signal strength and affect the link quality. Link quality is one of the key factors that affect network performance. In general, network performance improves with better link quality in a wireless network. In this study, we measure the network connectivity and performance in a shadow fading path loss model, and our observation shows that both are severely degraded in this path loss model. To improve network performance, we propose power control schemes utilizing link quality to identify the set of nodes required to adjust the transmission power in order to improve the network throughput in both homogeneous and heterogeneous multi-hop wireless networks. Numerical studies to evaluate the proposed schemes are presented and compared.

• 한국통신학회논문지
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• 제38C권1호
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• pp.33-42
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• 2013

본 논문에서는 비등방성 센서 네트워크에서 노드 간 연결 정보만을 이용하여 일반노드의 위치를 찾는 다중 홉 Range-free 측위 알고리즘을 제안한다. 제안하는 측위 알고리즘에서 일반노드는 자신과 앵커노드 쌍이 이루는 최단경로의 측정 홉 수와 기대 홉 수를 비교하여 최단경로의 우회 정도를 측정하고, 우회 정도에 따라 자신으로부터 앵커노드까지의 거리를 추정한다. 일반노드는 이러한 과정을 네트워크의 모든 앵커노드 쌍에 대하여 반복하며, 획득한 거리 정보를 사용하여 위치를 추정한다. 제안하는 알고리즘은 기존의 Range-free 알고리즘에 비해 적은 수의 앵커노드를 필요로 하며, 적은 통신 오버헤드를 갖는다. 마지막으로 성능평가를 위하여 MATLAB 시뮬레이션을 수행하였으며, 기존의 Range-free 측위 알고리즘에 비해 향상된 위치정확도를 보였다.

• 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.

• 대한원격탐사학회지
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• 제20권1호
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• pp.57-64
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• 2004

In GIS-based network analysis, topological measure of network structure can be considered as one of important factors in the urban transportation analysis. Related to this measure, it is known that the connectivity indices such as alpha index and gamma index, which mean degree of network connectivity and complexity on a graph or a circuit, provide fundamental information. On the other hand, shimbel index is one of GIS-based spatial metrics to characterize degree of network concentration. However, the approach using these quantitative indices has not been widely used in practical level yet. In this study, an application program, in complied as extension, running on ArcView- GIS is implemented and demonstrated case examples using basic layers such as road centerline and administrative boundary. In this approach, geo-spatial imagery can be effectively used to actual applications to determine the analysis zone, which is composed of networks to extract these indices. As the results of the implementation and the case examples, it is notified that alpha and gamma indices as well as shimbel index can be used as referential data or auxiliary information for urban planning and transportation planning.