• Information and Communications Magazine
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• v.12 no.12
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• pp.152-165
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• 1995

본 논문은 단계적으로 B-ISDN을 구축할 때 단계구분의 기준으로 널리 이용되는 ITU-T의 3단계 B-ISDN 신호(망제어) 능력의 주요 특성과 능력차이를 살펴보고, 이 능력기준에 의거해 구현된 B-ISDN간에 호환성을 고려한 네가지 망진화 방안들을 제안한다. 또한 B-ISDN 구축을 위해 현재 진행 중인 HAN/B-ISDN 연구개발 사업의 체계종합 연구 결과로 제시하는 단계별 B-ISDN 구축방안과 각 단계별 망의 형상과 주요 특징을 소개한다. 그리고, 신호 능력 단계에 따른 망 진화 방안으로서, 1 단계 망으로부터 2 단계 망으로 진화해가는 과정에서 어떻게 기능을 발전시킬 것인가에 대한 고찰을 통해 HAN/B-ISDN 사업에서 추구하는 단계별 망의 진화방안을 제시한다. 아울러 초고속정보통신망 구축을 위해 수반될 B-ISDN과 이종망간 연동을 위한 방안을 살펴보고, B-ISDN과 프레임릴레이망, N-ISDN등의 기존 유선 통신망과의 연동과 위성통신 및 이동 통신망, 그리고 ATM-Forum 규격을 토대로 한 사설 ATM망의 수용 방안을 제시한다.

• Korean Journal of Remote Sensing
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• v.15 no.3
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• pp.183-194
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• 1999

The Brightness, color and texture included in a multispectral satellite data are used as important factors to analyze and to apply the image data for a proper use. One of the most significant process in the satellite data analysis using texture or color information is to extract features effectively expressing the information of original image. It was described in this paper that six features were introduced to extract useful features from the analysis of the satellite data, and also a classification network using the back-propagation neural network was constructed to evaluate the classification ability of each vector feature in SPOT imagery. The vector features were adopted from the training set selection for the interesting region, and applied to the classification process. The classification results showed that each vector feature contained many merits and demerits depending on each vector's characteristics, and each vector had compatible classification ability. Therefore, it is expected that the color and texture features are effectively used not only in the classification process of satellite imagery, but in various image classification and application fields.

• Journal of Digital Contents Society
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• v.9 no.1
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• pp.87-99
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• 2008

High Altitude Platform network systems utilize Unmanned Aerial Vehicle as routers for ground node communication. For this purpose, geographical clustering of ground nodes must be required. In this paper, we assume mobile ground nodes over wide area and the clusters composed of ground nodes are identified. UAVs can be positioned at the point of centroid of clusters. The number of UAVs are derived from the area size and the number of ground nodes deployed in that area. From the simulation and application of clustering algorithms, we showed visual clustering results with dynamic variance of number of ground nodes.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.32-36
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• 2016

In wireless communication systems, jamming attack is a critical threat. Especially, reactive jamming can jam when the sender and receiver are communicating, which can maximize the attack efficiency of jamming. In this paper, we use the property of multi-input multi-output (MIMO) technology to achieve jamming resilient orthogonal frequency-division multiplexing (OFDM) communications. In particular, we use MIMO interference cancellation to remove the jamming signals strategically. We first investigate the reactive jamming attack model and their impacts on the MIMO-OFDM systems. We then present an iterative channel estimation algorithm that exploits MIMO interference cancellation. Our simulations show various anti-jamming methods and demonstrate the efficiency of our proposed algorithm under the reactive jamming attack.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.209-216
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• 2018

High-resolution satellite imagery is used in diverse fields such as meteorological observation, topography observation, remote sensing (RS), military facility monitoring and protection of cultural heritage. In satellite imagery, low-resolution imagery can take place depending on the conditions of hardware (e.g., optical system, satellite operation altitude, image sensor, etc.) even though the images were obtained from the same satellite imaging system. Once a satellite is launched, the adjustment of the imaging system cannot be done to improve the resolution of the degraded images. Therefore, there should be a way to improve resolution, using the satellite imagery. In this study, a super resolution (SR) algorithm was adopted to improve resolution, using such low-resolution satellite imagery. The SR algorithm is an algorithm which enhances image resolution by matching multiple low-resolution images. In satellite imagery, however, it is difficult to get several images on the same region. To take care of this problem, this study performed the SR algorithm by calibrating geometric changes on images after applying automatic extraction of feature points and projection transform. As a result, a clear edge was found just like the SR results in which feature points were manually obtained.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.32-37
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• 2014

The panorama is a good alternative to overcome narrow FOV under study in robot vision, stereo camera and panorama image registration and modeling. The panorama can materialize view with angles wider than human view and provide realistic space which make feeling of being on the scene based on realism. If we use all correspondence, it is too difficult to find strong features and correspondences and assume accurate homography matrix in geographic changes in images as load of calculation increases. Accordingly, we used SURF algorithm to estimate overlapping areas with high similarity by comparing and analyzing the input images' histograms and to detect features. And we solved the problem of input order so we can make panorama by input images without order.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.26-29
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• 2013

In order to estimate people crowdedness in public area, the texture based method or motion based method can be used. In this paper we have proposed a mixed method. By designating the region of interest, we made the degree of crowdedness more accurate. The feature normalization also reduced the image distortion which results from difference of camera angle. The proposed system was optimized to real time embedded hardware system.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.140-144
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• 2012

The classic method of recording and retrieving of images for video monitoring was very inefficient since the system required huge storage capacity. It's because it stored images without separating background and monitored objects. The recording and retrieval method of images for the video monitoring system we proposed in this paper makes it possible to retrieve images easily by using database by the hour and the place. Hence, it retrieve images much more efficiently than the existing method.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.41-45
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• 2011

This paper presents a fire detection criterion based on flame color, spatial and temporal characteristic analysis of color fire images. To propose the criterion, Firstly the fire candidate regions were selected by using analyzed Cr and Y threshold value, and then texture analysis of candidate regions was performed by using DCT. Finally variation of Y values of these regions was calculated for temporal analysis. The proposed fire detection criterion was simulated by using fifteen test images and practicality was verified.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.418-426
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• 2022

Unlike OSR(observation space representation), the SSR(state space representation) augmentation system is suitable for a one-way broadcasting service because it provides the same corrections to all users in the service area. Due to this advantage, several GNSS(global navigation system) systems such as Galileo, BDS(beidou navigation satellite system), QZSS(quasi zenith satellite system) are establishing PPP (precise point positioning)/PPP-RTK precision positioning services based on SSR messages. Therefore, in this paper, we try to understand the trends of satellite-based PPP/PPP-RTK correction services by analyzing the system configurations, characteristics, and precise positioning performance of satellite-based SSR correction broadcasting services.