• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.505-506
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• 2007

일반적으로 저가 장비를 이용한 수신 신호 강도(RSSI)의 측정은 전파의 특성상 다소 부정확한 정보를 제공하고, 이는 최소평균제곱오차(MMSE)를 이용한 위치 추정 방법에 있어 큰 오차 요인으로 작용한다. 따라서 이 논문에서는 수신 신호 강도를 이용한 기존의 위치 추정 방법을 개선하기 위해 센서 네트워크상의 유효 노드선정 알고리즘을 제시한다. 그리고 개선된 방법을 이용하여 센서 네트워크 기반의 실내 위치 추정 시스템을 구현 한다. 끝으로, 개선된 방법의 성능 검증을 위한 실험 결과를 제시 한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.01a
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• pp.91-92
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• 2016

무선 센서 네트워크에서 무선통신기술을 활용한 저비용의 정밀 측위 기술은 교통상황, 의료, 생활정보 등의 다방면에서 활용되고 있다. RSSI를 기반으로 한 측위기법은 TOA, AOA, TDOA에 비해 추가적인 전력 또는 하드웨어가 필요하지 않아 비용 면에서 효율적이다. 하지만 RSSI 값의 패턴은 실제 환경에서 전파방해 요소가 존재하여 작은 움직임에도 크게 변하게 되는 문제점이 있다. 본 논문에서는 RSSI와 IEEE 802.15.4 표준에서 제공되는 정보인 LQI를 이용하여 타겟 노드의 실내 위치를 추정하는 기법을 제안한다. 제안하는 기법을 통해 실제 환경에서 보다 정확한 위치추정을 할 수 있음을 보여준다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.132-132
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• 2023

본 연구에서는 식생대 퇴적과 침식, 하안침식을 고려한 식생대의 발달과정을 실내실험을 수행하여 정량적으로 분석하고 하도의 지형변화를 해석하는데 중요한 결과를 도출하였다. 식생대 입구와 중류부에서 식생대 좌완과 우안으로 흐름이 집중되며, 유속이 빠르다. 식생대와 식생이 없는 좌안과 우안의 유속차에 의하여 전단층이 형성되고 조직와가 발생하였다. 식생하도의 지형변화는 초기에 하안침식이 발생하고, 하폭이 증가하면 상류 유입구에서 중앙사주가 발달하였다. 시간이 증가하면서 사주는 하류로 이동하였다. 식생대에서 흐름이 분리되면서, 좌안와 우안에서수충부가 형성되고 하안이 침식되었다. 식생대 전면부에서 유사가 퇴적되며, 후면부에서 침식이 발생하였다. 식생밀도가 증가하면서 퇴적량은 증가하지만, 한계 이상으로 증가하면 퇴적량은 감소하였다. 수치모의 결과, 식생의 밀도가 증가함에 따라, 식생대 전면부에서 유사가 퇴적이 되고, 사주가 상류로 성장하면서 하안침식이 발생하였다. 또한 식생대에 의해 유사가 포착되면서, 식생대 후미에서 하상이 침식되었다. 식생대의 밀도가 증가하면서, 식생대 후미에서 침식이 발생하는 지점은 상류로 전파되었다. 식생대에 의해 발달한 사주는 실내실험에서 식생대 하류에서 성장하지만, 수치모의 결과는 식생대 상류에서 성장하는 특성을 보여주었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.620-622
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• 2009

본 논문에서는 독거노인의 응급상황이 실내에서 발생할 경우, 집안에 사람이 없을지라도 신속히 대처할 수 있는 방안을 연구하였다. 이를 위해 USN기반의 네트워크을 설계하고, 위치인식 알고리즘과 노드간 라우팅 기술을 개발하였다. 위치인식 알고리즘으로는 RSSI방식에 의해 이동노드가 고정노드로부터 오는 전파세기를 감지하는 방식을 이용하여, 비례값을 산출하는 방식을 채택하였으며, 삼각 측량법에 의한 이동노드 위치인식 알고리즘을 적용하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.9-14
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• 2008

Ubiquitous implementation of indoor location-based technology is recognized that one of the important elements of the technology. Specifically, the hospital management of patients, the silver-town management, the implementation of the smart home for the indoors rather than outdoors in a range of broadband users for location-aware technology is needed. This paper in wireless devices with an indoor location awareness shows about the system's technical design and implementation. Location-based technology for wireless LAN users aware of the strength of radio signals (Received Signal Strength Indication, RSSI) using trilateration. Topographic mapping system will be implemented wireless devices and servers, Access Point (AP), which is the system's development and testing throughout the physical environment to determine the potential for real-life applications.

• Journal of Broadcast Engineering
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• v.19 no.3
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• pp.372-384
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• 2014

DTV field tests have been performed to measure field strength and to check reception ratio on indoor and outdoor sites. They use an antenna of 9m to measure DTV signal in case of outdoor measurement on the road. Modern skyscrapers require the analysis of vertical-directional wave propagation by measuring vertical-directional DTV signal. Even if the field strength is above the reception threshold of $43dB{\mu}V/m$, the reception is impossible in case of strong multi-path or high impulse noise. So, vertical-directional field measurement is essential in environment of tall buildings. In this paper, we developed an octo type multi-copter to measure vertical-directional DTV signal level. A compact and portable DTV signal level meter, an antenna, a microwave transmitter for data transmission, and a recording equipment are equipped in the multi-copter. Three different sites are selected to test the measurement system. Developed measurement system using the multi-copter is very useful in measuring vertical-directional DTV signal, especially in apartments, non-accessible area by vehicles, and forbidden areas.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.75-82
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• 2007

As one of the main support systems, rock bolts play a crucial role in the reinforcement of tunnels. Numerical and experimental studies using a transmission method of ultrasonic guided waves are performed to evaluate the integrity of rock bolts encapsulated by grouting paste. Numerical simulations using "DISPERSE" are carried out for the selection of the optimal experimental setup, i.e. non-destructive testing (NDT) system of the rock bolt. Based on results of the numerical simulation, the calculated frequency range for NDT testing is between 20kHz and 70kHz with the first longitudinal L(1) mode. Laboratory transmission tests are performed by attaching the piezo electric sensor at the tip of the rock bolt before embedding. Both of analytical and experimental results show that the amplitude of signals as well as the wave velocity increases with increase in the defect ratio of grouting paste. The defect in grouting paste means that the space around the rock bolt is not fully filled with the grouting paste. Experimental results also show that the increase of the wave velocity is more sensitive to the defect ratio increase than that of the amplitude. This study demonstrates that the transmission technique of ultrasonic guided waves may be a valuable tool in the evaluation of the rock bolt integrity.

• Journal of Korea Water Resources Association
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• v.50 no.3
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• pp.201-210
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• 2017

This study proposes a numerical model which is able to simulate turbidity currents intruding into a reservoir and resulting sediment depositions. The proposed model is applied to laboratory experiments by Toniolo and Schultz (2005), and propagation of turbidity currents, morphological change, and trap of suspended sediment are simulated. It is simulated that the turbidity current after plunging at the foreset of the model delta, propagates along the bottom. The thickness of the turbidity current increases significantly after being blocked by the dam, and this effect is propagated in the upstream direction. In addition, it is simulated that the foreset moves in the downstream direction due to both the bedload and suspended load and the thickness of the bottom set increases due to the suspended load. It is found that the height of the intake affects the thickness of the turbidity current and the location of the internal hydraulic jump. The impact of the height of the intake on the trap efficiency is not clear in the experimental results, however, overall trap efficiency is predicted quite successfully by the model. Also, sensitivity analysis is carried out, and the results indicates that the particle size affects the trap efficiency most.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2141-2152
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• 1998

In this paper, we design and implement an indoor wireless modem using small signal of ISM band regulation, which can tranceive reliable data streams. We use direct sequence spead spectrum (DS-SS) signaling with synchronous BPSK and QPSK modulation, convolutional coding with viterbi decoding. The radio frequency module uses frequency devision duplexing in 900 MHz band, and the digital module is implemented with FPGAs for the purpose fo ASIC design. The perfomrance of our own acquistion and tracking circuit consisting digital matched filter and decision logic is proved by experiments, and the possibility of file transfer at indoor environment with the entrie system that the modem is connected the PC through RS-232C port is verified.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.766-776
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• 1999

In this paper to evaluate the performance of the polarization diversity and the space diversity in the indoor environment, we used 3D Ray-tracing simulation. This model is capable of predicting small scale fading characteristics of the channel for evaluating the performances of both the polarization and the space diversity scheme. The measurement and simulation results show that the polarization diversity and the space diversity are expected to be efficiently used for the indoor environments. Moreover, the results show that the proposed polarization diversity technique using directional dual polarization microstrip array antennas has more diversity gain than the conventional polarization and space diversity using dipole antenna.