• 한국인터넷방송통신학회논문지
• /
• 제12권6호
• /
• pp.189-197
• /
• 2012

본 논문에서는 위성과 모바일기기 간의 전파수신감도를 활용한 최적경로탐색 알고리즘을 제안한다. 일반적인 경로탐색은 최단경로를 기반으로 하기 때문에 위성을 이용하는 모바일기기의 안정적인 멀티미디어 서비스 제공이 어렵다. 제안된 알고리즘은 전파수신감도를 기반으로 하는 경로탐색을 통해 안정적인 통신환경의 제공을 목적으로 한다. 위성통신에서 수신환경에 따라 전파수신감도 변화가 심하기 때문에 수신환경의 특성을 정확하게 분석하는 것이 매우 중요하다. 전파감쇠 요인으로 대기감쇠, 수풀감쇠, 건물에 의한 감쇠 등을 적용하여 시뮬레이션을 통해 분석하고 전파수신감도로 활용한다. 제안된 알고리즘은 도심지에서 위성을 활용한 안정적인 멀티미디어 서비스 제공을 위한 최적경로를 찾을 수 있다.

• 한국전자통신학회논문지
• /
• 제15권2호
• /
• pp.211-218
• /
• 2020

실내 환경에서 송수신기의 위치 변화에 따른 전파 전달 특성을 시뮬레이션을 통하여 예측하고, 경로손실 측정을 통하여 얻어진 결과를 예측결과와 비교하고 분석하였다. 경로손실 측정 환경으로는 대회의실을 선택하였으며, 또한 실내 장식물 및 비품이 없는 전시실을 선택하여 두 환경의 전파 전달 특성을 비교하였다. 각 실내 환경에서 송신기의 위치는 전방 벽면 중앙과 측면 벽면 중앙에 위치하는 두 가지 경우를 선택하였고, 수신기의 위치는 실내 공간의 중심선과 측면 벽을 따라 움직이며 수신 전력을 측정하였다. 각각의 송수신기 위치변화에 대하여 3GHz와 6GHz의 수신 전력을 측정하고 시뮬레이션 예측 결과와 비교하였다. 송신기의 위치 및 주파수 대역 변화에 따라 각 수신점에서 수신 전력의 변화를 분석하였다.

• 천문학회지
• /
• 제56권2호
• /
• pp.213-224
• /
• 2023

Type II solar radio bursts show frequency drifts from high to low over time. They have been known as a signature of coronal shock associated with Coronal Mass Ejections (CMEs) and/or flares, which cause an abrupt change in the space environment near the Earth (space weather). Therefore, early detection of type II bursts is important for forecasting of space weather. In this study, we develop a deep-learning (DL) model for the automatic detection of type II bursts. For this purpose, we adopted a 1-D Convolution Neutral Network (CNN) as it is well-suited for processing spatiotemporal information within the applied data set. We utilized a total of 286 radio burst spectrum images obtained by Hiraiso Radio Spectrograph (HiRAS) from 1991 and 2012, along with 231 spectrum images without the bursts from 2009 to 2015, to recognizes type II bursts. The burst types were labeled manually according to their spectra features in an answer table. Subsequently, we applied the 1-D CNN technique to the spectrum images using two filter windows with different size along time axis. To develop the DL model, we randomly selected 412 spectrum images (80%) for training and validation. The train history shows that both train and validation losses drop rapidly, while train and validation accuracies increased within approximately 100 epoches. For evaluation of the model's performance, we used 105 test images (20%) and employed a contingence table. It is found that false alarm ratio (FAR) and critical success index (CSI) were 0.14 and 0.83, respectively. Furthermore, we confirmed above result by adopting five-fold cross-validation method, in which we re-sampled five groups randomly. The estimated mean FAR and CSI of the five groups were 0.05 and 0.87, respectively. For experimental purposes, we applied our proposed model to 85 HiRAS type II radio bursts listed in the NGDC catalogue from 2009 to 2016 and 184 quiet (no bursts) spectrum images before and after the type II bursts. As a result, our model successfully detected 79 events (93%) of type II events. This results demonstrates, for the first time, that the 1-D CNN algorithm is useful for detecting type II bursts.

• Journal of electromagnetic engineering and science
• /
• 제3권2호
• /
• pp.91-98
• /
• 2003

Software Communication Architecture(SCA) has been made to reduce the development period of new waveform applications by reusing design modules. Software Defined Radio(SDR) forum adopted SCA specification and follows its design concept. However, SCA specification does not describe interfaces and deployments of resources in details, which are software components, and how to implement them as well as how to communicate each other are another missing points in specification. In this paper, we propose a resource design methodology and details of adapter implementation for Core Framework(CF) that is a core set of open interface and services providing an abstraction of the underlying software and hardware layer. We also present SDR prototype system which communicates with resources implemented in different programming languages and processors in legacy environment through our design methodology.

• Journal of electromagnetic engineering and science
• /
• 제6권2호
• /
• pp.117-122
• /
• 2006

This paper presents the impacts of Ultra-wideband(UWB) applied in the communication applications using frequency band from 3.1 GHz to 10.6 GHz on Broadband Wireless Access(BWA) based on orthogonal frequency division multiplexing(OFDM) using frequency band of 3.5 GHz. It proposes low duty cycle(LDC) for enabling UWB to mitigate strong interference to BWA. The effects of interference mitigation are evaluated and analyzed in the environment of UWB coexistence with BWA. UWB with LDC scheme will be given to bring higher transmit power level corresponding to Federal Communications Commission(FCC) provisional limit for enabling UWB operation at 3.5 GHz bands.

• 한국군사과학기술학회지
• /
• 제11권2호
• /
• pp.16-22
• /
• 2008

So far, Korean command post vehicles(CPs) have used voice-only radio communication among the mechanized troop units such MBTs and IFVs, etc. But digital data communication technology should be introduced to improve mission success capabilities and accommodate integrated combat capabilities through increasing SA(situation Awareness), or spatiotemporal synchronization of military operation in battle field environment. Therefore, conventional CPs, which have been operated without digital network, urgently needs to mount a battle management system which furnish with tactical information network, considering that korean new MBTs or new IFVs will be fielded soon. This study suggests some performance enhancement method which might be applicable to CPs which have a role of connecting Battalion unit to Brigade C4I system.

• 한국정보과학회:학술대회논문집
• /
• 한국정보과학회 2005년도 가을 학술발표논문집 Vol.32 No.2 (1)
• /
• pp.112-114
• /
• 2005

In today's hyper-competitive business environment, Radio Frequency Identification (RFID) technology is expected to enhance the operation efficiency of supplying chain management in both manufactures and retail industries. However, the widespread deployment of RFID tags may create new threats to user privacy, due to the powerful tracking capability of the tags. Many authentication protocols for RFID have been proposed. They are helpful preventing passersby being scanned to determine what articles they are carrying. However, most of them would not prevent the bigger physical tracking problem of RFID, especially when being tracked by the 'constellation' of products they carry. We proposed this RFID scheme to prevent these tracking problems.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.255-260
• /
• 2011

The train control system is a facility to ensure safe train operation, and its safety is the most important factor for system introduction. Therefore, in order to improve practical usability in the business, safety analysis and evaluation of train control system and train control related core technologies are needed. Korea Railroad Research Institute has carried out standard development of radio-based train control system as a government research and development project. In this paper, we present a system specification of ATP, a core part of train control system, for standard system of Korean radio-based train control system(KRTCS). The paper present a operation environment and primary ATP functions, and functional requirement specifications.

• Ocean and Polar Research
• /
• 제34권4호
• /
• pp.453-462
• /
• 2012

Ocean surface current data in Korea was collected using sets of High-Frequency Ocean Surface Radars (HFOSRs) with 25 radial sites in the frequency range of 5~43 MHz. Site selection and the correct installation of HFOSR are very important considerations in order to secure continuous and reliable results. The installation procedures of HFOSR are summarized as follows: 1. Survey area selection; 2. Investigation of ambient radio waves and installation environment; 3. Domestic license of radio station; 4. Installation of antenna and housing of electrical and communication devices. The current work describes the entire processes of HFOSR installation within Korea.

• 대한전자공학회논문지TC
• /
• 제43권5호
• /
• pp.17-23
• /
• 2006

본 논문에서는 광대역통합망 응용을 위하여 ROF 링크와 접속된 무선 OFDM 시스템의 인접채널전력비를 해석하였다. RF 증폭기에서 비선형 효과에 의한 인접채널전력비의 해석을 다룬 기존의 결과들과 다르게 본 논문에서는 ROF 링크를 포함한 유무선통합 링크에 대하여 IEEE 802.11a의 5.8GHz OFDM 신호의 인접채널전력비를 해석하고 시뮬레이션한 결과를 보였다.