• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.41-42
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• 2006

In this paper, we propose a rapid asynchronous UWB (Ultra Wide Band) position location scheme based on double RTTs (Round-Trip Transmissions). In the proposed scheme, to avoid performance degradation of the position location in harsh multipath channel environments where LoS (Line-of-Sight) components are not always guaranteed, the remaining RTT information is solved from realistic double RTTs. Simulation results in IEEE 802.15.4a UWB channel models reveal that the proposed scheme can achieve closely comparable position location accuracy of the conventional ToA (Time of Arrival) method based on triple RTTs, while reducing the processing delay required for the calculation of the position locations.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.8
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• pp.742-747
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• 2004

Outdoors we can easily acquire our accurate location by GPS. However, the GPS signal can't be acquired indoors because of its weak signal power level. Adequate positioning method is demanded for many indoor positioning applications. At present, wireless local area network (WLAN) is widely installed in various areas such as airport, campus, and park. This paper proposes a positioning algorithm using WLAN signal strength to provide the position of the WLAN user indoors. There are two methods for WLAN based positioning, the signal propagation method uses signal strength model over space and the empirical method uses RF power propagation database. The proposed method uses the probability distribution of the power propagation and the maximum likelihood estimation (MLE) algorithm based on power strength DB. Test results show that the proposed method can provide reasonably accurate position information.

• IEMEK Journal of Embedded Systems and Applications
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• v.4 no.1
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• pp.16-22
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• 2009

This paper aims at designing an impulse-radio ultra-wideband (IR-UWB) transceiver, especially targeting the IEEE 802.15.4a indoor ranging and communication systems. We first investigate the IEEE 802.15.4a IR-UWB signals and suggest the full-digital transceiver architecture accordingly. Since the wireless systems equipped with the impulse signal have the property of low-duty cycle, i.e., discontinuity in time, while the conventional systems takes the continuous signals, it is required to reconfigure the system design, including link budget. Following brief introduction to our IEEE 802.15.4a IR-UWB system hardware, we finally examine the ranging performance in indoor environments to verify our system design.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.211-213
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• 2005

최근의 위치 측위 기술과 무선 통신 기술의 발전에 따라 위치 기반 서비스에 대한 관심이 크게 증가하고 있다. 기존의 단일 노드 기반 시스템으로는 처리하기 힘든 휴대폰 사용자와 같은 대용량의 객체를 처리하기 위해 제시된 클러스터 기반 분산 컴퓨팅 구조로 GALIS 아키텍처가 제안되었다. 본 논문에서는 제시한 프로토타입은 그동안 구현된 기존 GALIS 프로토타입보다 개선된 구조로 SLDS에서 Global $Cell\_ID$를 적용하여 노드의 분할 합병 시 발생할 수 있는 처리 비용을 감소시켰다. 또한 LLDS에서는 필터링을 통해 손실들 수 있는 위치 데이타 정보를 보다 신뢰할 수 있는 데이타로 만들기 위한 기능을 추가하여 질의 시 발생할 수 있는 여러 가지 상황을 대비할 수 있게 되었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.73-75
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• 2018

LoRaWan(Long Range Wide Area Network)은 저전력, 장거리 특성을 가진 무선 통신기술로 그 특성상 스마트 시티(Smart City), IoT(Internet of Things) 등에 각광받고 있다. 또한 LoRaWan은 Chirp 신호 특성에 의해 실외 삼각측량에 따른 사용자 위치 추정 기술을 제공한다. 본 논문에서는 이러한 LoRaWan의 특성에 더해 Wi-Fi 지문 정보를 활용하여 위치 추정 정확도를 개선하고 또한 이웃 Wi-Fi 단말들, 가령 스마트폰 등의 위치 정보를 LoraWan 게이트웨이와 통신하여 최종적으로 서버에서 측위 할 수 있는 시스템을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.703-706
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• 2007

위치기반서비스에서 사용자의 정확한 위치가 요구되면서 옥내 위치기반서비스를 위한 무선 LAN기반 옥내 측위와 추적에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 AP 신호의 세기를 바탕으로 거리와 신호세기의 관계를 통해 사용자의 위치에서 AP들까지의 거리를 구한 후, Trilateration으로 위치를 추적하는 방법과 EKF 방법을 비교한다. EKF를 이용할 때 필터링에 사용되는 파라메타들의 값에 따라 달라지는 실험 결과들을 비교 분석하여 적절한 파라메타 값을 찾고, 나아가서 파라메타 값을 적절히 적용함으로써 경로의 정확성을 제고하는 방법을 제시한다. 제안하는 방법의 효율성을 실험적으로 증명하기 위한 실험 결과와 분석 내용도 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.755-762
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• 2014

In recent year, along with the rapid development of LED technology, many applications using LEDs with Visible Light Communication(VLC) have been researched. Since it is easy to provide LOS communication environment along with cheap deployment cost, the indoor positioning system based on VLC has been actively studied. In this paper, we propose an accurate indoor positioning algorithm using a stereo image sensor and white-light LEDs with the visible light communication. Indoor white-light LEDs are located at the ceiling of a room and broadcast their position information by VLC technology. Mobile receiver with stereo image sensor receives LED position information by VLC and estimates its position and angle information. Simulation results are given to show the efficiency of proposed indoor positioning algorithm.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.58-62
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• 2016

In this paper, we propose a pre-processing scheme for improving indoor positioning accuracy in impulsive noise channel environments. The impulsive noise can be generated by multi-path fading effects by complicated indoor structures or interference environments, which causes an increase in demodulation error probability. The proposed pre-processing scheme is performed before a triangulation method to calculate user's position, and providing reliable input data demodulated from a received signal to the triangulation method. Therefore, we studied and proposed an adaptive threshold function for mitigation of the impulsive noise based on wavelet denoising. Through results of computer simulations for the proposed scheme, we confirmed that Bit Error Rate and Signal-to-Noise Ratio performance is improved compared to conventional schemes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.89-91
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• 2022

Wireless sensor networks(WSN), which are mainly used for indoor positioning, rely on the accuracy of RSSI. This RSSI is sensitive to several factors that cause interference, and there are foreign studies showing that temperature has a large effect on RSSI in indoor/outdoor environment among several factors. The temperature of the indoor space is uneven due to heat sources or air cooling systems indoors, and temperature changes frequently occur at certain locations. In particular, in case of an indoor fire, the accurate positioning system is required to guide an evacuation route, but a high temperature is locally formed due to a fire around the receiver, so the RSSI value could be influenced. In this paper, the effect on RSSI is studied by analyzing the correlation between SoC internal/local temperature and RSSI.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.101-104
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• 2015

In this paper, a flight techniques many quadcopters which can be configured flexibly squadron according to the situation in wireless sensor networks is suggested. In previous studies, aircrafts fly only as part of a prescribed form and know the distance between the aircraft by sensor was able to maintain the fleet. Also, the problem occurs that between the aircraft distance is not constant. In this paper, proposes an algorithm that the context of the formation fly using the current position of the quadcopter through a virtual map is based on the relative coordinates without being affected by Indoor, outdoor and obstacles. Proposed algorithm is Leader-Follower Technique that the method of determinin the shape of the squadron to the down command to the sub-quadcopter using the wireless network by the main quadcopter to determine a given situation. As simulation result, the proposed algorithm was confirmed that formation flight efficient in sensing the all conditions as compared to the conventional method.