• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1999-2007
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• 2017

In this paper, we implement a multi-band network selection (MNS) system based on Linux operating system which determines the optimal communication link for given network conditions among the available LTE, very high frequency (VHF), and high frequency (HF). The implemented software consists of a network interface, an MNS server, and a user GUI. We perform indoor test to verify the function of the implemented MNS system using two sets of MNS system. To this end, two types of VHF communication links that follow ITU-R M.1842-1 Annex 1 and Annex 4 are emulated in software. In addition, the HF transmission (reception) port of one MNS is directly connected to the HF reception (transmission) port of another MNS. We demonstrate through indoor tests that the implemented MNS system can support seamless maritime communication service in spite of artificial disconnection or re-connection of LTE, VHFs, and HF. The implemented MNS system is applicable to various maritime communication services including e-navigation.

• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.101-106
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• 2016

A femtocell network has been attracting attention as a promising solution for providing high data rate transmission over the conventional cellular network in an indoor environment. In this paper, we propose a distributed power control algorithm considering both indoor coverage and data load balancing in the femtocell network. As data traffic varies by time and location according to user distribution, each femto base station suffers from an unbalanced data load, which may degrade network performance. To distribute the data load, the base stations are required to adjust their transmission power dynamically. Since there are a number of base stations in practice, we propose a distributed power control algorithm. In addition, we propose the simple algorithm to detect the faulty base station and to recover coverage. We also explain how to insert a new base station into a deployed network. We present the simulation results to evaluate the proposed algorithms.

• Journal of the Korea Society of Computer and Information
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• v.13 no.5
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• pp.179-186
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• 2008

In proportion as the growth of the wireless sensor network applications, we need for more accuracy wireless channel information. In the case of indoor or outdoor wireless sensor networks, multipath propagation causes severe problems in terms of fading. Therefore, a path-loss model for multipath environment is required to optimize communication systems. This paper deals with log-normal path loss modeling of the indoor 2.4 GHz channel. We measured variation of the received signal strength between the sender and receiver of which separation was increased from 1 to 30m. The path-loss exponent and the standard deviation of wireless channel were determined by fitting of the measured data. By using the PRR(Packet Reception Rate) of this model. Wireless sensor channel is defined CR(Connect Region), DR(Disconnected Region). In order to verify the characteristics of wireless channel, we performed simulations and experiments. We demonstrated that connection ranges are 24m in indoor, and 14m in outdoor.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.337-339
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• 2008

실내에서 많은 시간을 보내는 현대인들에게 있어서 공기 청정기는 필수품이 되어가고 있다. 이런 상황에서 현재 출시된 대부분의 공기 청정기들은 본체에 장착된 센서만을 이용하기 때문에 효율적인 제어가 어렵다. 따라서 본 논문은 센서 네트워크를 이용하여 보다 효율적으로 공기 청정기를 제어하는 알고리즘을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.847-856
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• 2013

This paper presents an AP placement technique considering indoor location-awareness and examines its performance. The proposed AP placement technique is addressed from three performance metrics: location-awareness and AP-based wireless network performance as well as its cost. The proposed AP placement technique consists of meta-heuristic algorithms that yield a near optimal AP configuration for given performance metrics, and deterministic algorithms that improve the fast convergence of the near optimal AP configuration. The performance of the AP placement technique presented in this paper is measured under the environments simulating indoor space, and numerical results obtained by experimental evaluation yield the fast convergence of a near-optimal solution to a given performance metric.

• Electronics and Telecommunications Trends
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• v.22 no.2 s.104
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• pp.48-57
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• 2007

본 고에서 다루고자 하는 지능형 로봇 공간(intelligent robotic space)은 이동성(mobility), 조작성(manipulability)으로 대표되는 로봇의 독특한 기능을 분산센싱, 분산처리환경을 구축하여 고기능화함으로써 자연스러운 이동, 조작기능의 구현이 가능한 공간으로 정의할 수 있다. 이는 개념적으로 가상 공간(virtual space), 추론 공간(semantic space), 물리 공간(physical space)으로 구성된다. 가상 공간은 로봇-센서간 융합을 통한 환경지도 작성 및 표현을 위한 플랫폼 기술이고 추론 공간은 로봇 및 로봇과 연동된 사람이나 사물의 상태 해석을 위한 객체 모델 기술이다. 물리 공간은 지능형이동성과 로봇 조작 능력의 향상을 위한 지능형 하드웨어 공간이다. 본 고에서는 물리공간에서 가장 핵심적인 이슈인 실내 측위기술에 대해서 알아본다. 측위기술은 사람이나 사물의 위치를 정밀하게 결정하여 로봇이 인간과 공존할 수 있도록 안정적이고 신뢰성 있는 측위 정보를 제공하는 것을 목적으로 한다. 지능형 로봇을 위한 측위기술은 크게 무선 센서네트워크 기반의 광역(coarse) 위치 결정과 RFID 및 로봇 비전(vision)을 기반으로 하는 정밀(fine) 위치 결정으로 나뉘어진다. 본 고에서는 Wi-Fi, ZigBee, UWB를 이용하는 무선 센서네트워크 기반의 실내 위치 측정에 관한 연구 개발 동향을 분석하고 각각의 기술이 가지는 장단점을 비교한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.159-160
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• 2019

It would be very important to localize people at risk as soon as possible in order to minimize the damage. Generally the infrastructure should be deployed additionally for indoor positioning system. In this paper, we proposed an indoor localization system for people at risk using the existing fire alarm networks. The system detects the signal of smart devices of people in danger immediately and let the main alarm controller ring all alarms in vessel and display the position. Thus, the proposed system can make the burden much less to deploy additional network and infrastructure.

• Journal of the Korea Computer Graphics Society
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• v.27 no.3
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• pp.31-42
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• 2021

We propose a deep learning-based method that can estimate an appropriate lighting of both indoor and outdoor images. The method consists of two networks: Crop-to-PanoLDR network and LDR-to-HDR network. The Crop-to-PanoLDR network predicts a low dynamic range (LDR) environment map from a single partially observed normal field of view image, and the LDR-to-HDR network transforms the predicted LDR image into a high dynamic range (HDR) environment map which includes the high intensity light information. The HDR environment map generated through this process is applied when rendering virtual objects in the given image. The direction of the estimated light along with ambient light illuminating the virtual object is examined to verify the effectiveness of the proposed method. For this, the results from our method are compared with those from the methods that consider either indoor images or outdoor images only. In addition, the effect of the loss function, which plays the role of classifying images into indoor or outdoor was tested and verified. Finally, a user test was conducted to compare the quality of the environment map created in this study with those created by existing research.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.2
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• pp.1-9
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• 2012

Wireless sensor nodes are widely used for various applications such as environmental monitoring. In this paper, the RSSI and PER are measured for the indoor environment with the various interferences such as obstacles(concrete walls, steel doors) and the 2.4GHz wireless LAN interference. Also, the RSSI and PER are measured for the outdoor environments. From the measured values of the RSSI and PER, the guideline for the stable operation of the wireless sensor network is suggested.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.436-439
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• 2008

위치기반 서비스(LBS : Local Based Service)는 단연 GPS가 그 중심이라 할 수 있다. 그러나 실외가 아닌 실내에서의 측위는 GPS신호가 도달할 수 없고, 또한 기존에 연구 중인 실내측위 기술들은 여러 가지 문제점을 갖고 있다. 따라서 다양한 서비스가 구현 가능한 ZigBee 기반의 USN내에서 기존의 다양한 센서들이 구동되면서 ZigBee 노드 간의 신호의 세기인 RSSI(Received Signal Strength Indicator)를 활용한 위치측위시스템을 구현한다. 또한 기존의 RSSI를 활용한 실내측위의 문제점들을 보완하기 위하여 신경회로망을 이용한 위측측위 알고리즘을 제안하여 보다 정확하고 안정적인 위치정보 시스템을 구현한다. 따라서 실내위치측위가 필요한 다양한 공공장소에 적합한 위치기반 서비스가 도입될 수 있는 가능성을 제시한다.