• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.99-100
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• 2006

One of the fundamental problems in sensor networks is the deployment of sensor nodes. The Fuzzy C-Means(FCM) clustering algorithm is proposed to determine the optimum location and minimum number of sensor nodes for the specific application space. We performed a simulation using two dimensional L shape model. The actual length of the L shape model is about 100m each. We found the minimum number of 15 nodes are sufficient for the complete coverage of modeled area. We also found the optimum location of each nodes. The real deploy experiment using 15 sensor nodes shows the 95.7%. error free communication rate.

• Journal of the Korea Safety Management & Science
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• v.13 no.2
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• pp.147-155
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• 2011

For an effective energy management in intelligent buildings it is necessary to gather information about position/absence of people and the level of population. In this paper the smart occupancy detection system based on the active RFID is developed to satisfy such a demand. The performance of the developed system is tested and verified through various experiments. Furthermore the feasibility test of the active RFID tag is performed to verify whether it can be used as a location-based occupancy sensor. The developed core technology can be also applied to other fields such as security, healthcare, smart home, etc.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.445-447
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• 2003

본 논문에서는 PDA(Personal Digital Assistants)를 이용한 차세대 위치기반서비스를 위한 분산 DB 제어기(DB Scheduler)와 XML interpreter 및 UI Manager를 개발하고 구현하였다. 분산 DB 제어기에서는 지리적으로 뜯어져있는 많은 분산 DB의 데이터에 대해 실시간으로 지능적 수집 및 변경 등이 가능하도록 하는 DB 제어기술을 개발하였으며, XML Interpreter 및 UI Manager에서는 하나의 단말기로 다양한 환경 및 서비스 수용이 가능하도록 하는 클라이언트용 기능 개발을 하였으며 단말기를 서비스 및 목적에 맞게 customize 할 수 있도록 단말기 기종별 개발 언어 등 세부 규격을 분석하고 가능한 국제 표준을 따라 설계서를 작성하였다.

• Annual Conference of KIPS
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• 2004.05a
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• pp.1529-1532
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• 2004

A Mobile Ad Hoc NETwork (MANET) is a collection of wireless mobile nodes that forms a temporary network without the need for any existing network infrastructure or centralized administration. Therefore, such a network is designed to operate in a highly dynamic environment due to node mobility. In mobile ad hoc network, frequent topological changes cause routing a challenging problem and without the complete view of the network topology, establishing the shortest path from the source node to the destination node is difficult. In this paper, we suggest a routing approach which utilizes location information to setup the shortest possible path between the source node and the destination node. Location information is obtained through Global Positioning System (GPS) and this geographical coordinate information of the destination node is used by the source node and intermediate nodes receiving route request messages to determine the shortest path to the destination from current node.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.3
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• pp.207-214
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• 2021

A new positioning technique for positioning of LTE base stations is proposed. The positioning information of the base station is absolutely necessary for model-based wireless positioning, and is required in some of the various merhodologies for estimating signals in an uncorrected area when construnting a database for fingerprinting-based positioning. Using the acquired location-based Reference Signal Received Power (RSRP) information to estimate the location of the base station, it is impossible with the existing trilateration methods. Therefore, in this paper, a method using reference particles is proposed. Particles are randomly generated in the application area, and signal propagation modeling is performed assuming that a base station is located in each particle. Based on this, the errors of measurements are calculated. The particle group with the minimum measurement errors is selected, the position of the base station is estimated through weighted summation, and the signal propagation model of the corresponding base station is built at the same time. The performance of the proposed technology is verified using data acquired in Seocho-dong, Seoul.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.27 no.1
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• pp.139-142
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• 2023

In this paper, we propose a GNSS-UWB hybrid positioning system for indoor and outdoor seamless positioning. Fusion of GNSS and inertial sensors has been widely used as a method for estimating positions in places where GNSS reception sensitivity is low, and UWB technology, which started as a short-range wireless communication technology, is widely used indoors where GNSS is completely blocked. This paper proposes a method of mutual correction and fusion of the location information collected through GNSS and the location information collected from the UWB indoor positioning system when indoor and outdoor work occurs continuously and repeatedly, such as in an industrial site.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.285-291
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• 2022

WSN is the major component for information transfer in IoT environments. Source Location Privacy (SLP) has attracted attention in WSN environments. Effective SLP can avoid adversaries to backtrack and capture source nodes. This work presents a Two-Level Randomized Sector-based Routing (TLRSR) model to ensure SLP in wireless environments. Sector creation is the initial process, where the nodes in the network are grouped into defined sectors. The first level routing process identifies sector-based route to the destination node, which is performed by Ant Colony Optimization (ACO). The second level performs route extraction, which identifies the actual nodes for transmission. The route extraction is randomized and is performed using Simulated Annealing. This process is distributed between the nodes, hence ensures even charge depletion across the network. Randomized node selection process ensures SLP and also avoids depletion of certain specific nodes, resulting in increased network lifetime. Experiments and comparisons indicate faster route detection and optimal paths by the TLRSR model.

• Annual Conference of KIPS
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• 2010.11a
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• pp.879-882
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• 2010

본 연구는 idle 상태의 단말을 위한 이종 무선 통신망 환경에서 네트워크 선택 알고리즘을 제안한다. 제안 하는 알고리즘은 셀과 사용자 각각의 상대적 상태 정보를 이용하는 프로필기반 네트워크 선택 프레임워크(Profile-based Network Selection Framework, PNSF)에 기반한다. PNSF 는 traffic status, mobility, 그리고 QoS (Quality of Service) 카테고리의 정보들을 바탕으로 셀과 사용자의 프로필을 생성한다. 생성된 프로필들을 3 차원의 프로필 공간에서 위치 시키고 각 셀과 사용자 프로필 사이의 거리를 각 카테고리를 구성하는 요소의 정적 특성을 반영하여 계산한다. 사용자는 최종적으로 가장 거리가 긴 셀을 선택하여 location update 를 수행한다. 본 연구에서 제안하는 알고리즘은 이종의 무선통신망 환경의 특성과 idle 모드의 특성을 반영하여 location update 의 발생 빈도를 합리적으로 줄이면서도 급증하는 데이터 통신 사용을 고려하여 사용자가 네트워크에 전체에 적절히 분산되도록 선택한다.

• ETRI Journal
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• v.44 no.1
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• pp.125-134
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• 2022

Visible light communication (VLC) systems incorporate ambient lighting and wireless data transmission, and the experienced channel in indoor VLC is a major topic that should be examined for reliable communication. In this study, it is realized that multiple transmitters in classical alignment are the forceful factors for channel characteristics. In the frequency band, fluctuations with sudden drops are observed, where the fluctuation shape is related to the source layout and receiver location. These varying frequency-selective channels need solutions, especially for mobile users, because sustained channel estimation and equalization are necessary as the receiver changes its location. It is proven that using light-emitting diodes (LEDs) with highly directional beams as sources or using a detector with a narrow field of view (FOV) in the receiver may help partially alleviate the problem; the frequency selectivity of the channel reduces in some regions of the room. For flat fading channel characteristics all over the room, LEDs should be aligned in hexagonal cellular structure, and detector FOV should be arranged according to the cell dimension outcomes.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.138-143
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• 2002

This paper describes a framework for extending GIS databases to support moving object data type and query language. The rapid progress of wireless communications, positioning systems, and mobile computing devices have led location-aware applications to be essential components for commercial and industrial systems. Location-aware applications require GIS databases system to represent moving objects and to support querying on the motion properties of objects. For example, fleet management applications may require storage of information about moving vehicles. Also, advanced CRM(Customer Relationship Management) applications may require to store and query the trajectories of mobile phone users. In this trend, maintaining consistent information about the location of continuously moving objects and processing motion-specific queries is challenging problem. We formally define a data model and query language for mobile objects that includes complex evolving spatial structure, and propose core algebra to process the moving object query language. Main profit of proposed moving objects query language and algebra is that proposed model can be constructed on the top of GIS databases.