• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1439-1442
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• 2006

위치기반서비스 시스템에서 가장 기본이 되는 요소는 사용자의 위치를 정확히 측정하는 것이다. 본 논문은 삼각 측량법을 이용한 전자캠퍼스를 위한 옥내 측위 시스템 구현 사례를 소개한다. 캠퍼스에는 일반적으로 무선 LAN이 설치되어 있다. 본 측위 시스템의 측위 방법은 무선 LAN의 액세스 포인트(AP)로부터 수신된 신호의 RSSI를 이용하여 AP까지의 거리를 추정하고, 이 거리들을 바탕으로 삼각 측량법을 이용하여 사용자의 위치를 추정한다. 구현한 측위 시스템의 성능을 검증하기 위한 실험 결과도 소개한다.

• Journal of IKEEE
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• v.12 no.2
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• pp.75-80
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• 2008

There are many researches to reduce power consumption of battery-operated Transceiver for 2.4 GHz smartRF applications. However, components such as processor, memory and LCD based power managements reach the limit of reducing power consumption. To overcome the limit, this research proposes novel low-power Transceiver and transceiver Hardware Design. Experimental results in the real smartRF Transceiver show that the proposed methods can reduce power consumption additionally than component based power managements.

• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.170-175
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• 2009

This paper introduces Zigbee based ubiquitous service. Most of ubiquitous services require the position information. Positioning algorithms utilize the transmission characteristics of the signal. Zigbee based positioning researches have been conducted mainly for the spatial factors inside the building. This paper proposes the possibility to consider the temporal factors of Zigbee signal and analyzes empirically the signal characteristics influenced according to the temporal factors as well as the spatial factors for ubiquitous services based on Zigbee sensor network.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.53-56
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• 2003

In order to enhance the system capacity of multi rate IEEE 802.11 WLAN, we propose the transmission rate select method using the control frame in this paper. The transmission rate is selected dynamically based on the RSSI(Received Signal Strength Indicator) of received control frame. And we also propose the Enhanced NAV Update method for Fragmented MPDU burst transmission in multirate WLAN environment. This method can improve the system capacity by support the burst transmission of fragmented MPDU.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.2047-2051
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• 2009

In this paper, we propose the localization method on WSN(Wireless Sensor Network) using fuzzy model and Kalman filter. The proposed method is as follows: First, we estimate the distance of RSSI(Receive Signal Strength Index) by using fuzzy model in order to minimize the distance error. Second, we use a triangulation measurement for estimating the localization. And then, we minimize the localization error using a Kalman filter. Finally, we show the effectiveness and feasibility of the proposed method through some experiments.

• International conference on construction engineering and project management
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• 2007.03a
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• pp.88-95
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• 2007

In this paper, the authors discussed the overview of a method for estimating working area for development of a monitoring system for labor management using RFID technology. RSSI (Receive Signal Strength Indication) data of RFID tag was obtained from readers set around the indoor space. An estimating model of the working area was prepared. The model had a range of the percentage of correctly classified from 61% to 95%. According to the result, the possibility of the monitoring system and the factors necessary to develop for practical were proposed.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.853-856
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• 2008

센서 네트워크의 한 개의 노드인 모바일 센서 차량들은 주위를 이동하면서 장애물을 탐지하고, 자신이 만든 지도를 서로 교환하여 합쳐 자신의 위치를 지역화한다. 이를 위해서 모바일 센서 차량들은 각종 센서를 탑재하여 자신의 위치를 파악한다. 이 논문에서는 데드-레코닝, 카메라, 그리고 RSSI 를 사용한 모바일 센서 차량의 지역화를 개별적으로 실험해봄으로써 거리에 따른 정확성을 알아보고, 이로써 각각 방식들이 가진 장점을 융합하여 보다 낳은 지역화할 수 있는지 살펴본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.6
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• pp.824-834
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• 1993

In cellular mobile communication systems, if the size of a cell is decreasing for economic utilization of frequency resources, frequent handovers may be requested because the time a mobile stays in a cell is decreasing. In general the measured parameters to decide handover including RSSI, BER, and the distance between mobile station and base station, are usually incorrect and handover decision using single parameter insufficient. Therefore, the better handover algorithm should take over the problems of this uncertain measurements, and make the decision more robust and flexible by the consideration of all those decision parameters at the same time. We propose a novel handover algorithm based the multicriteria decision making, in which those parameters are participated in the decision process using aggregation function in fuzzy set theory. As a simulation results, the overall decision making is more reliable and flexible than the conventional method using only one parameter, RSSI in terms of call force ratio, and handover request ratio.

• Journal of Advanced Navigation Technology
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• v.12 no.4
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• pp.324-331
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• 2008

In this paper, we developed the crops monitoring system using wireless sensor networks. It can acquire the information about the cultivation environments from a temperature, humidity, illumination and soil sensor then use the detailed information for very useful. The acquisition about the cultivation environment information with wireless sensor networks can be made up an environment that an administrator is able to confirm the information and wherever in a remote place instead of conventional way visiting the cultivate place by investing a lot of money and time. Therefore, it could be saving money, time and effort, and reduced the damages from the natural disasters such as a cold-weather damage and drought. In addition, we could be possible preventing from the damages of blight and harmful insects according to the temperature by an analysis. In agriculture field, this system could be supported for making a foundation of the advanced technology developing endless, and, in IT field, it is look forward to preparing the opportunity which creates a new requirement on the new technology.

• Journal of the Korea Society of Computer and Information
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• v.25 no.1
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• pp.63-69
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• 2020

In this paper, we propose an indoor positioning technique using the landmark based on relative Access Point (AP) signal strengths. The absolute values of AP signals are used to conventional indoor positioning technologies, but they may be different because of the difference of the measuring device, the measuring environment, and the timing of the measurements. However, we found the fact that the flow of the AP's RSSI in certain places shows almost constant patterns. Based on theses characteristics, we identify the relative strength between the APs and store the certain places as landmarks where they show certain patterns. Once the deployment of the landmark map is complete, system calculate position of user using the IMU sensor of smartphone and calibrate it with stored landmarks. Our system shows 75.2% improvement over technology that used only sensors, and 39.6% improvement over technology that used landmarks that were selected with absolute values.