• 경영과학
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• 제18권1호
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• pp.41-54
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• 2001

In this paper, we proposed a method to determine optimal wave source for mobile telephone communication. The approach is based on wave propagation simulation. Given a wave source we can determine wave propagation effects on every surfaces of wave simulation environment. The effect is evaluated as a cost function while the source’s position x, y, z work as variables for a parameter optimization. Wave propagated 3 dimensional space generates reflected waves whenever it hits boundary surface, it receives multiple waves which are reflected from various boundary surfacers in space. Three algorithms being implemented in this paper are based on a raytracing theory. If we get 3 dimensional geometry input as well as wave sources, we can compute wave propagation effects all over the boundary surfaces. In this paper, we present a new approach to compute wave propagation. First approach is tracing wave from a source. Source is modeled as a sphere casting vectors into various directions. This approach has limit in computing necessary wave propagation effects on all terrain surfaces. The second approach proposed is tracing wave backwards : tracing from a wave receiver to a wave source. For this approach we need to allocate a wave receiver on every terrain surfaces modeled, which requires enormous amount of computing time. But the second approach is useful for indoor wave propagation simulation. The last approach proposed in this paper is tracing sound by geometric computation. We allow direct, 1-relfe tion, and 2-reflection propagation. This approach allow us to save in computation time while achieving reasonable results. but due to the reflection limitaion, this approach works best in outdoor environment.

• International Journal of Aeronautical and Space Sciences
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• 제7권2호
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• pp.56-69
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• 2006

For a relatively small country like Korea, a radionavigation system using airships can be considered, which is to provide the navigation service utilizing the stratospheric airships that are deployed in the stratosphere at the altitude of around 20-23km, and which is an independent or a back-up radionavigation system other than current GPS or GLONASS. In this paper, a feasibility study on the constellation of stratospheric airships for the navigation system has been performed. A measure of a geometrical condition between a receiver and navigation transmitters. called the DOP (Dilution of Precision), determines the resulting positioning error of the navigation system, if the error of range measurement is predictable. Therefore, with assumption that the range measurement error of the stratospheric airship navigation system is quite similar to GPS. the several DOP values have been used to evaluate the performance of the navigation system with comparing with the DOP values of GPS as the reference values. To provide the position information of the navigation transmitters to users, a receiver cluster system fixed on the ground, called an IGPS (inverted GPS), is proposed, and the error is also evaluated using the DOP values. Five areas around five major cities in South Korea have been selected, and then by numerical simulations the DOP values are compared those of GPS to assess the performance of the proposed navigation system using stratospheric airships. The possible frequency bands have been proposed. and then link budget of the navigation transmitter has been analyzed for the proposed navigation system.

• 한국위성정보통신학회논문지
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• 제4권1호
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• pp.8-13
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• 2009

한국전자통신연구원은 다양한 위성항법 응용프로그램과 항법알고리즘을 시험 및 평가하기 위한 소프트웨어 레벨의 환경을 제공하는 위성항법 신호생성 및 수신처리 시뮬레이터 툴을 개발하고 있다. 본 시뮬레이션 툴은 GPS 및 갈릴레오의 디지털 신호 생성하고 이를 수신처리하는 툴을 제공하게 된다. 본 논문에서는 이러한 위성 항법 신호생성 및 수신처리 시뮬레이션 툴의 상세설계 및 모듈 구현에 대하여 기술하고 있다.

• 한국멀티미디어학회논문지
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• 제20권6호
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• pp.853-864
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• 2017

HD padding area is essential redundancy in HD broadcasting. It is possible to use this padding area for the purpose of improving DTV broadcasting services. For utilization of this area, The bit of a service data was converted to black and white $8{\times}8$ block image. Converted block images are compressed with active video and are delivered to a receiver as only DC coefficients in a video stream. video quality is not effected by the proposed method, and service data was perfectly recovered in receiver without errors by using block average and threshold. The proposed utilization of HD essential padding area can possibly overcome the limited transmission stream rate with the bandwidth of HD broadcasting. If service data in transport or video stram were transferred using this padding area, it is possible to improve video quality with expanded video stream rate. Additionally, because the proposed methods are based on well-established standards, it is also useful for world-wide HD broadcasting systems such as ATSC, DVB, and IPTV.

• 제어로봇시스템학회논문지
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• 제10권11호
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• pp.1089-1094
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• 2004

Diseases in the gastro-intestinal track are on an increasing trend. In order to diagnose a patient, the various signals of the digestive organ, such as temperature, pH, and pressure, can offer the helpful information. Among the above mentioned signals, we choose the pressure variation as a monitoring signal. The variation of a pressure signal of the gastro-intestinal track can offer the information of a digestive trouble or some clues of the diseases. In this paper, a pressure monitoring system for the digestive organs of a living pig is presented. This system concept is to transmit the measured biomedical signals from a transmitter in a living pig to wireless receiver that is positioned out of body. The integrated solution includes the following parts: (1) the swallow type pressure capsule, (2) the receiving set consisting of a receiver, decoder box, and PC. The merit of the proposed system if that the monitoring system can supply the precise and repeatable pressure in the gastro-intestinal track. In addition, the design of low power consumption enables it to keep sending reliable signals while the pressure capsule is working in the digestive organ. The subject of the study for the pressure monitoring system is in-vivo experiments for a living pig. We achieved the pressure tracings in digestive organs and verified the validity of system after several in-vivo tests using pressure monitoring system. As a result, we found each organ has its own characterized pressure fluctuation.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.647-655
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• 2008

This paper presents real-time algorithm for an ultrasonic Local Positioning System(LPS). An ultrasonic LPS consists of 4 transmitters and n receivers. Each transmitter transmits an sequential ultrasonic signal to avoid interference of ultrasonic signal. This method is a noneffective application for a fast object. Because receiver detects four sequential transmissive ultrasonic signal and calculates a position. This paper proposes the method which 4 transmitters transmit simultaneous ultrasonic signal and each transmitter distinguished by frequencies and codes. And Auto-Correlation Function(ACF) method separates codes from an ultrasonic echo signal which is interference of each transmitter's code. If the receiver uses only ACF method, it is difficult to implement real time application for increased computation. This paper implements LPS using dual frequencies and ACF method. Using dual frequencies reduces codes length. The reduced codes length save computation in ACF. To prove this algorithm by experiment, high performance DSP(digital signal processor) used. The result shows the performance of the designed system is good enough positioning.

• Journal of Positioning, Navigation, and Timing
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• 제3권2호
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• pp.45-51
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• 2014

GNSS has the disadvantage of being vulnerable to jamming, and thus, the necessity of jamming countermeasure techniques has gradually increased. Jamming countermeasure techniques can be divided into an anti-jamming technique and a jammer localization technique. Depending on the type of a jammer, applicable techniques and performance vary significantly. Using an appropriate jamming countermeasure technique, the effect of jamming on a GNSS receiver can be attenuated, and prompt action is enabled when estimating the location of a jammer. However, if an inappropriate jamming countermeasure technique is used, a GNSS receiver may not operate in the worst case. Therefore, jammer identification is a technique that is essential for proper action. In this study, a technique that identifies a jammer based on template matching was proposed. For template matching, analysis of a received jamming signal is required; and the signal analysis was performed using a spectral correlation function. Based on a simulation, it was shown that the proposed identification of jamming signals was possible at various JNR.

• 한국항행학회논문지
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• 제3권1호
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• pp.52-59
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• 1999

선형 증폭단, ADC 그리고 디지털 신호 처리기로 이루어진 디지털 광대역 마이크로파 수신기는 시스템의 감도와 동적 범위로 성능 평가를 해석할 수 있다. 시스템의 감도와 동적 범위는 시스템의 이득, 3차 상호변조적과 ADC 특성으로 결정되어지며 선형 증폭단의 설계 방법 또한 중요한 영향을 미친다. 그리고 수신기로 입력되는 두 신호의 주파수가 인접한 경우 디지털 신호 처리기는 두 신호를 분리할 수 있어야 한다. 본 논문에서는 증폭단의 이득을 변화시켜 동적 범위를 측정한 다음, 가장 적절한 감도와 동적 범위를 선택할 수 있는 이득 값을 결정하고, 인접한 두 신호의 분리를 위해 고해상도 스펙트럼 추정법을 사용하였다.

• 한국정보통신학회논문지
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• 제15권8호
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• pp.1813-1819
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• 2011

본 연구에서 제안하는 위치인식시스템은 전파의 위상 및 크기를 이용하여 거리를 구하고 여기서 구한 거리 정보를 보다 정확하게 측정하기 위해서 비젼에 의한 영상 히스토그램 기법을 이용하여 보완하는 기술이다. 제안하는 기술은 거리측정용 무선송수신기로부터 송수신된 900Mhz대 RF 신호로부터 중간주파수인 450Khz의 아날로그 데이터를 디지털신호처리를 통하여 얻어내며, 여기서 얻어진 거리 정보에다 비젼에 의해 얻어진 거리를 상호 보완하여 보다 정확한 거리 정보를 획득한다. 측정된 거리의 평가를 위해서 실제거리와 측정된 거리를 비교 분석하고, 또한 평균처리 및 진폭특성을 통한 측정오차 개선 방법과 기존의 RF 신호만 이용하는 경우와 비교 검토한다.

• 한국음향학회지
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• 제24권8호
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• pp.462-468
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• 2005

본 논문에서는 초음파를 이용한 수중 버스트 QPSK 전송에서 높은 과샘플율을 갖는 수신기에서의 프레임 동기방법에 대하여 제안한다. 제안한 프레임 동기 검출기에서는 두 번 반복되는 16심벌 길이의 CAZAC 신호열 중 가운데 16심벌을 취하여 이 심벌열과 수신 신호의 샘플과의 상관값을 계산한 후, 문턱값과 비교하여 프레임 동기를 검출한다. 또한, 설계한 프레임 동기 검출기의 성능의 근사값을 유도하였으며, 시뮬레이션을 통하여 유도한 성능 근사값이 실험값과 잘 맞음을 확인하였다.