• IEMEK Journal of Embedded Systems and Applications
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• v.4 no.4
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• pp.148-155
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• 2009

Precise localization heavily relies on the accuracy of its underlying ranging technique. It has been known that the Chirp Spread Spectrum (CSS) defined in the IEEE 802.15.4a provides more dependable ranging accuracy than the Received Signal Strength Indicator (RSSI) in the IEEE 802.15.4. This paper examines the accuracy of the CSS-based ranging technique in the indoor/outdoor environments and discovers its consistent inaccuracy in different environments. Next, it proposes an error-correction architecture for the CSS-based ranging technique that exploits the per-environment consistent inaccuracy information and user visiting patterns (represented by weights for each environment).

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.175-181
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• 2014

Location awareness is one of the key functions to build an U-city. Recently, many of works for the location-aware systems are emerging to be applied to on-going large-scale apartment complex. For example, when dwellers or cars with active tags are move in the apartment complex, the active tags broadcast their own identifiers periodically and receivers such that routers use this information to calculate the location of the active tags. Since the active tags can actually move between routers and coordinators, it requires a hand-off mechanism. In this paper, we investigate the hand-off problem occurred in location awareness system based on ZigBee active tags. We propose and analyze a new approach for handling the hand-off problem. Through a mathematical analysis, we show that our approach diminishes the quantity of packet transfer than ZigBee's approach.

• Journal of the Korea Society of Computer and Information
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• v.22 no.8
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• pp.9-14
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• 2017

In this paper, we propose the smart belt system for preventing loss of items using Beacon. The proposed system monitors the distances of the registered items via the belt that is always worn. The belt determines the loss of the items by measuring the relative distance via RSSI (Received Signal Strength Indicator) value of the signals received from the BLE (Bluetoothl Low Energy) sensor, which is attached on the items such as bags and wallets. If the registered item is determined to be lost, the belt rings to remind the user of the loss. The missing status could be known to users through the smartphone application connected to the belt. The smartphone application communicates with the belt using Beacon, and provides users with a quick and easy way to check the status of their items.

• International Journal of Advanced Culture Technology
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• v.6 no.3
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• pp.216-225
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• 2018

Strangely enough, there has not been much effort in applying the latest technologies to help referees make accurate calls in a soccer game compared to other sports. Modern soccer tries to apply VAR (Video Assistant Referee) technology to correct inaccurate calls such as an offside, but this is being put off due to the fact that real time decision-making cannot be carried out by using this technology. This has led this study to decide developing a device that will accurately identify offsides on a real time basis using various latest sensors and related technologies. This device will aid referees in calling offsides in a soccer match.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.87-92
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• 2011

In this paper, we got the 800 ~ 900 MHz path loss model for Russia PNG area using the free space model and the Okumura-Hata Model. In order to add new regional properties to the existing path loss model, the mean square error technique is used to obtain the correction factor. The correction factors for the free space and the Hata model are 28, 13 dB respectively. By applying this correction factors, the new Russain PNG path loss model is proposed.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.1
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• pp.25-31
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• 2012

We propose a method for an indoor mobile robot to track user with infrared transmitter. Several infrared receivers attached around by the mobile robot enable the robot to determine the moving direction by comparing the received signal patterns. The cost of the proposed system is not only cheaper than ultrasonic system, image signal processing, RFID, and RSSI method, but also robust against environment change because any complex algorithm is not necessary. In the mobile robot, ultrasonic sensors are equipped to avoid obstacles located in the moving direction, and a simple algorithm is embedded to avoid the case of poor signal reception.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.430-432
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• 2007

This paper proposes the possibility of SonicID system which is the active RFID based on the ultrasonic spectrum instead of using radio frequency. For the feasibility study, various performance indexes are measured in terms of power consumption and signal path loss onto the frequencies of 40KHz, 433MHz, and 2.4GHz. In addition to the line of sight condition, realistic situations are considered for diverse deploying environments. The results of these analyses demonstrate that the SonicID holds the potential to meet the needs of future advanced RFID system in a scalable fashion.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1323-1324
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• 2015

최근, 다수의 이동 로봇으로 구성된 무선 네트워크 기반 군집 로봇 시스템을 제한적인 환경을 벗어나 다양하고 동적인 환경에서 운용하기 위한 연구가 진행 중이다. 특히, 다수 로봇의 위치를 측정하기 위해 실내 환경에 기반 시설 없이 로봇에 장착된 센서들에 의해 위치를 추정하는 방법이 필요하다. 이를 위해, 본 논문에서는 로봇간의 상대적인 정보를 통해 다수 이동 로봇의 거리를 추정하는 방법을 제안한다. 제안한 방법은 먼저, 다수 이동 로봇의 거리를 추정하기 위해 무선 신호를 기반으로 하는 RSSI 방법을 이용하여 다수 이동 로봇의 거리를 추정한다. 그 다음, 추정된 거리와 추측 항법(Dead Reckoning)을 융합하여 이동 중인 로봇의 거리를 추정하는 방법을 제안한다. 마지막으로, 시뮬레이션 도구를 이용하여 응용 가능성을 증명한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.793-796
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• 2016

정보통신 기술의 발달로 사물인터넷에 대한 관심이 증가하였다. 사물인터넷의 한 요소인 무선 큰거리 통신 기술에는 WIFi, 블루투스, ZigBee 등이 있다. 이러한 기술들 중 저전력 블루투스는 낮은 전력 소비와 범용성 덕분에 많은 각광을 밭고 있다. BLE(Bluetooth LE)의 한 형태인 비콘은 더욱 저전력이며, 패킷을 전달하는 방식 또한 기존의 블루투스와 차이가 있다. 본 논문에서논 컨텐츠 보안이 필요한 비콘 서비스의 예시로 비콘을 통한 새로운 형태의 음악 음반을 제시하였다. 또한, 그 보안 특성에 맞춰 패킷 이중화, RSSI, Serial Number Binding 등의 기술들을 사용한 보안 방법을 설계 및 구현한 보안 사레에 대하여 서술한다.

• The Journal of Korea Robotics Society
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• v.4 no.3
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• pp.177-184
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• 2009

This paper presents an active assisted-living system in wireless sensor and actor network (WSAN) in which the mobile robot roles an actor. In order to provide assisted-living service to the elderly people, position recognition of the sensor node attached on the user and localization of the mobile robot should be performed at the same time. For the purpose, we use received signal strength indication (RSSI) to find the position of the person and ubiquitous sensor nodes including ultrasonic sensor which performs both transmission of sensor information and localization like global positioning system. Active services are moving to the elderly people by detecting activity sensor and visual tracking and voice chatting with remote monitoring system.