• 한국통신학회논문지
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• 제38B권7호
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• pp.535-542
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• 2013

Coordinated multi-point transmission (CoMP) is considered to be a promising technique to improve the throughput for LTE-Advanced systems. One important approach for CoMP is Joint Transmission (JT). However, the analytical model of JT has not been fully studied, as user equipments (UEs) receiving the desired signals from an adjacent base station (BS) as well as serving BS, or only serving BS were not distinguished. We derive a new analytical model to describe the call admission control in JT based systems. The performance measures of interest are the call blocking probability, and resource utilization. Furthermore, we compare the performance of JT-based systems and non-JT- based systems. The analytical results are in reasonable agreement with the simulation results.

• 한국군사과학기술학회지
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• 제13권3호
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• pp.413-420
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• 2010

An Estimation of VHF data link range for EW(Electronic Warfare) equipment in the sea environment was studied to predict the data link range between transmitting and receiving station. The theoretical estimation predicts within 3% error with actual measurement of VHF data link range at sea. Data link range factors including refraction and reflection are added in the basic wave propagation equation. The effect of refraction and reflection to the range is analysed with quantity level.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.7-11
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• 2007

The aim of this paper is to design and implement a new ECG signal monitoring and analysis method for the home care of elderly persons or patients, using wireless sensor network (WSN) technology. The wireless technology for home-care purpose gives new possibilities for monitoring of vital parameter with wearable biomedical sensors and will give the patient freedom to be mobile and still be under continuously monitoring. Developed platform for portable real-time analysis of ECG signals can be used as an advanced diagnosis and alarming system. The ECG features are used to detect life-threatening arrhythmias, with an emphasis on the software for analyzing the P-wave, QRS complex, and T-wave in ECG signals at server after receiving data from base station. Based on abnormal ECG activity, the server transfer diagnostic results and alarm conditions to a doctor's PDA. Doctor can diagnose the patients who have survived from arrhythmia diseases.

• 한국항해학회지
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• 제24권4호
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• pp.299-312
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• 2000

Because shore(ship) to ship(shore) communication service via INMARSAT pay expensive cost, satellite service typically use two stage service that land users dial up LES(Land Earth Station) for sending or receiving message. In order to send and receive message, land users must maintain online state with LES on dedicated line. Also, two stage INMARSAT communication service must consume long time that processes step by step. In case of large company, they have own communication system, but small companys communicate simple messages with only telex. This paper describes the design and implementation of an integrated communication services via INMARSAT-C. This system uses inexpensive INMARSAT-C for transmission between ship and land. Because this system provides web and E-Mail interface, users send and receive messages easily and quickly. This system provides most users with inexpensive and easy communication facilities between ship and land.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1039-1041
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• 2003

Ocean color products derived from remote sensing satellite data are useful for monitoring the sea water quality such as the concentrations of chlorophyll, sediments and dissolved organic matter. Currently, ocean color products derived from MODIS data can be requested from NASA over the internet. However, due to the bandwidth limitation of most users in this region, and the time delay in data delivery, the products cannot be use for near-real time monitoring of sea water chlorophyll. CRISP operates a MODIS data receiving station for environmental monitoring purposes. MODIS data have been routinely received and processed to level 1B. We have adapted the higher level processing algorithms from the Institutional Algorithms provided by NASA to run in a standalone environment. The implemented algorithms include the MODIS ocean color algorithms. Seasonal chlorophyll concentration composite can be compiled for the region. By comparing the near-real time chlorophyll product with the seasonal composite, anomaly in chlorophyll concentration can be detected.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.811-813
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• 2003

The Satellite Technology Research Centre (SaTReC), Korea Advanced Institute of Science and Technology (KAIST) has developed and is to launch STSAT-1 (Science and Technology Satellite - 1) on 27$^{th}$ September 2003. The data collection system (DCS) is the one of its payloads. The DCS is a data relay system used for transmission from ground-based sensors through satellite to receiving station. This is one of the important methods collecting global data from the remote locations. In this paper, the DCS on the STSAT-1 will be introduced and the development of the mobile terminal (MT) will be reported.

• 대한원격탐사학회지
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• 제14권1호
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• pp.95-101
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• 1998

본 논문에서는 일본 지구관측 위성인 JERS-1의 광학 센서 (OPS) 영상에 나타나는 줄무늬를 제거하기 위해 개발된 알고리즘에 대해서 기술한다. 개발된 알고리즘은 주위의 화소 값을 사용하는 공간 또는 주파수 대역의 필터링 기술과는 달리 영상 각 줄의 평균 값을 사용하는 통계적 방법을 사용하기 때문에 영상의 방사학적 성질을 변화시키지 않는다. 개발된 알고리즘은 인공위성연구센터 위성영상 직수신국의 터리 단계의 일부로 삽입되어 사용자에게 줄무늬 효과를 크게 줄인 OPS 영상을 제공하는데 도움을 줄 것이다.

• Journal of Information Processing Systems
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• 제18권6호
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• pp.803-812
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• 2022

With the increasing number of mobile device users worldwide, utilizing mobile edge computing (MEC) devices close to users for content caching can reduce transmission latency than receiving content from a server or cloud. However, because MEC has limited storage capacity, it is necessary to determine the content types and sizes to be cached. In this study, we investigate a caching strategy that increases the hit ratio from small base stations (SBSs) for mobile users in a heterogeneous network consisting of one macro base station (MBS) and multiple SBSs. If there are several SBSs that users can access, the hit ratio can be improved by reducing duplicate content and increasing the diversity of content in SBSs. We propose a Deep Q-Network (DQN)-based caching strategy that considers time-varying content popularity and content redundancy in multiple SBSs. Content is stored in the SBS in a divided form using maximum distance separable (MDS) codes to enhance the diversity of the content. Experiments in various environments show that the proposed caching strategy outperforms the other methods in terms of hit ratio.

• 한국약용작물학회지
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• 제7권2호
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• pp.138-142
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• 1999

지황(Rehmannia glutinosa)의 국내 수요증가와 재배확대에 따른 우량 신품종 육성의 기초자료를 얻고자 몇몇 지황속 식물의 작물학적 특성을 조사하고, 재배환경이 지황의 생육 및 수량에 미치는 영향을 조사한 결과는 다음과 같다. 지황종 식물의 학명은 Rehmannia glutinosa Libosc, Rehmannia glutinosa Libosc var. purpurea Makino 및 Rehmannia glutinosa Libosch var. hueichingensis (Chao et Schih) Hsiao 등으로 지상부 생육특성과 뿌리의 작물학적인 형태는 다양한 차이를 보였다. 중국으로부터 도입 육성한 지황 1호는 근경이 굵고 다수성이고 일본종은 가늘며 깊게 신장하는 특성을 보였으며 국내재래종은 중간형질을 지니고 있었다. 지황1호를 공시하여 적정재배 환경을 조사한 결과 지황의 근비대 생장은 7월 중하순경에 근중과 근경 모두 급속하게 증가함을 보였고, 일장과 온도는 제한된 3처리중 13시간 일장에서 주간 $23^{\circ}C$ 야간 $18^{\circ}C$ 처리에서 근비대 생장이 가장 양호 하였다. 토양은 양토조건에서 2,144kg/10a로 가장 높은 수량성을 보였고 토양수분이 $60{\sim}70%$에서 근비대 생장이 양호하였다.

• 한국통신학회논문지
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• 제36권3A호
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• pp.232-239
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• 2011

IEEE 802.11n 표준은 새로운 방식의 전송속도 조절기법(Link adaptation)을 위한 기반을 제공한다. 802.11n에서 채널의 변화로부터 최대한의 이득을 얻기 위해, 한 단말은 다른 단말에게 Modulation and Coding Scheme (MCS) 피드백을 요청할 수 있다. 그러나 무선 채널의 상태는 시간에 따라 변한다. MCS 피드백 요청으로부터 피드백 받은 정보의 적용까지 걸린 시간이 특정 값보다 커지면 그 사이의 채널 상태 변화로 언해 피드백 받은 정보는 쓸모없어지게 된다. 단말이 무선채널 상태의 변화 정도를 추정할 수 있다면 전송속도 조절기법의 정확도를 개선할 수 있다. 이 논문은 크게 두 항목에 초점을 맞추고 있다. 첫째, NS-2 시뮬레이션을 통해 802.11n에서 coherence time이 MCS 피드백 기반 전송속도 조절기법의 성능에 어떤 영향을 마치는지 분석한다. 둘째로, 이 논문은 전송속도 조절기법의 성능에 큰 영향을 주는 채널의 coherence time을 추정하는 효율적인 방법을 제시한다. Allan variance 정보 통계를 활용하여 단말은 수신 링크의 coherence time을 추정할 수 있다. 추정한 coherence 기반의 Link adaptation에 적용할 경우 기존의 기법보다 더 나은 성능을 얻을 수 있다.