• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.94-100
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• 2017

In this paper, we suggest a design method of a metamaterial-based low-profile antenna working at 425 MHz for LEO/Cube satellites. Satellites play an important role in linking th remote nodes in a wireless communication network and covering wide areas of the globe. Especially, an increasing number of universities or individuals aspire having their own satellites and build low-budget structures such as cube satellites in LEO and the ways to reduce the sizes of their satellites. Since the antenna occupies a major portion of the satellite surface, the antenna should be miniaturized for lighter weight. The proposed metamaterial low-profile antenna, unlike the conventional patch antenna, produces such a zeroth-order resonance to create an omnidirectional radiation pattern. Also, it is connected to a UHF waveguide bandpass filter as the feeding system to examine the possible change in the situation that the antenna is combined with the system. The performances of the monopole and proposed metamaterial antennas are compared to one another.

• Atmosphere
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• v.27 no.2
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• pp.119-131
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• 2017

We present and discuss the Tropopause Folding Turbulence Detection (TFTD) algorithm for the Korean Communication, Ocean, Meteorological Satellite (COMS) which is originally developed for the Tropopause Folding Turbulence Product (TFTP) from the Geostationary Operational Environmental Satellite (GOES)-R. The TFTD algorithm assumes that the tropopause folding is linked to the Clear Air Turbulence (CAT), and thereby the tropopause folding areas are detected from the rapid spatial gradients of the upper tropospheric specific humidity. The Layer Averaged Specific Humidity (LASH) is used to represent the upper tropospheric specific humidity calculated using COMS $6.7{\mu}m$ water vapor channel and ERA-interim reanalysis temperature at 300, 400, and 500 hPa. The comparison of LASH with the numerical model specific humidity shows a strong negative correlation of 80% or more. We apply the single threshold, which is determined from sensitivity analysis, for cloud-clearing to overcome strong gradient of LASH at the edge of clouds. The tropopause break lines are detected from the location of strong LASH-gradient using the Canny edge detection based on the image processing technique. The tropopause folding area is defined by expanding the break lines by 2-degree positive gradient direction. The validations of COMS TFTD is performed with Pilot Reports (PIREPs) filtered out Convective Induced Turbulence (CIT) from Dec 2013 to Nov 2014 over the South Korea. The score test shows 0.49 PODy (Probability of Detection 'Yes') and 0.64 PODn (Probability of Detection 'No'). Low POD results from various kinds of CAT reported from PIREPs and the characteristics of high sensitivity in edge detection algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.523-528
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• 2004

The bands 27.5 ∼ 28.35GHz and 31.0 ∼ 31.3GHz were allocated to the High Altitude Platform Station in WRC-2000. However, since these bands were already allocated to the existing fixed-satellite service, the analysis on the interference effects between the existing FSS/GSO system and FS/HAPS system should be needed. To do study on the interference effects between above two systems, we can consider two frequency operational conditions, one is the Reverse mode and the other Forward mode. In this paper, we considered the Forward mode as the frequency operational condition and analyzed the interference effect from a number of GSO satellites to HAPS ground station due to the I/N values, the latitude of HAPS and the satellite separation. In future, these results will be vital data to share between HAPS and GSO systems.

• The Journal of Korean Institute of Information Technology
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• v.17 no.3
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• pp.31-41
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• 2019

In this paper, we design and implement the simulator for the transmitter and receiver of 4D-8PSK TCM with 2.0, 2.25, 2.5, and 2.75 bits/symbol-channel transmission efficiency recommended by the CCSDS for satellite communications, and then analyze the BER performance of 4D-8PSK TCM system in AWGN channel. The transmitter of 4D-8PSK TCM is designed in accordance with the recommendation in the CCSDS standard. Meanwhile, for the receiver design of 4D-8PSK TCM, we design the differential decoder generalizing the differential encoder/decoder scheme. The trellis decoding algorithm is designed by applying the auxiliary trellis information and the Viterbi algorithm, and an 8-dimensional constellation mapper equation given in the CCSDS standard is deconstructed to design constellation mapper. Especially, we present the optimized receiver for 4D-8PSK TCM system by investigating the BER performances for the traceback lengths in the Viterbi decoder through computer simulations..

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.88-92
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• 2006

Proto Flight Model of Reaction Wheel Assembly Interface Unit(RIU) for STSAT-2 was developed. The RIU of STSAT2 has three major functions for interface between satellite system and RWAs. It has switches for RWA main power, communication Mux. and communication line driver.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.25-28
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• 2003

본 논문은 Ka 밴드(26.5GHz-40GHz)를 사용한 양방향 멀티미디어 시스템의 설계에 대해서 다루고 있다. 우선 무궁화 3호 위성을 이용한 시범사업의 구성 및 운영과정에 대해서 개괄하고, 시범운영에서 발견된 문제점을 소개한다. Ka 밴드 양방향 위성 시스템은 MF-TDMA(Multi-Frequency Time Division Multiple Access) 방식을 사용하여 최대 전송속도 2Mbps 이상이고, QOS(Quality of Service) 제공 등 다양한 기능을 갖추고 있으나 Ka 주파수 특성상 그 안정성에 있어서 어려움을 갖고 있다. 강우감쇄 및 전송 지연 등의 현상들을 소개하고 향후 위성 양방향 시스템의 구성과 응용 서비스를 구현할 때 고려해야 할 사항들에 대해 고찰해 보고, 해결방안을 제시하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1833-1841
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• 1996

Recently, by emerging of the ALE techniques that make it possible to providereliable communications link automatically, high frequency communiation is newly used as emergency communication and back-up for satellite communications. ALE signal is transmitted in burst, and the received signal is subject to distortions by detrimental multipath fading channels. In the case of that channel, the performance of ALE system is highly dependent upon that of synchronization techniques. In this paper, M-ary FSK signals are detected by a bank of bandpass filter, which is implemented using recusive DFT(Discrete Fourier Transform). Also an acquisition and trancking algorithm are designed uisng parallel structure and early-late-gate methods respectively. Finally, we verify the performance ofthe proposed synchronization algorithm by the computer simulation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.513-519
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• 2013

The fishing industry in Europe has faced environmental, economic, and social challenges. Since the early 2000s, a key tool in addressing these challenges has been information and communication technology (ICT), which has helped to modernize fishery systems in European Union (EU) countries. The ICT used in EU fisheries can be categorized broadly as 1) macro-technologies such as satellite and other remote sensing technologies in combination with geographical information systems, 2) micro-technologies adapted for fishing vessels such as echo sounders, ship navigation devices, and mobile communication devices to connect fishermen and consumers, and 3) onshore micro-technologies related to internet technology and mobile devices. The European Monitoring Center on Change has used ICT to effectively manage fisheries bio-resources. This use of ICT has contributed to the development of sustainable and competent fisheries in the 2000s, even though the knowledge-sharing practices involved are contrary to the long tradition of autonomy within the fishery industry.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.139-147
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• 2014

The ballast water may be discharged into another sea area with marine organisms, it caused problems to disturb the marine ecosystem. So, in order to remove these environmental risk factors, the IMO has mandated the installation of BWTS to the all ships. Our monitoring system diagnose and predict a failure of BWTS by analyzing the sensor information of BWTS collected from which the ships scattered in the ocean of several. This paper presents the design and implementation of communication modules for BWTS remote monitoring considering the satellite communication charge fee. In the our study, we implemented the safety and cost-saving communication modules by LabVIEW program. The collected sensor informations is encrypted and compressed by LabVIEW modules running on RIO. Then they will be transfer to the land server and will be decrypt to enable monitoring in the land server. For the verification, we build the test modules which can verify from collecting the sensor data to consuming them in the monitoring server. We carried out 20 times for the data pattern in all of case. So, we verified the excellent functionality and reliability through the experimental result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.788-794
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• 2007

The policy of US DoD is moving towards implementation of Network Centric Warfare(NCW) concepts. NCW is commonly described as the integration and synchronization of four key interdependent elements such as command and control, sensor system, engagement systems and the network. Therefore the military policy of Korea military is needed to access and examine the policy of NCW communication environment and crypto communication, which is able to apply it. In this case study, We are reviewed the security framework of the concept of network centric warfare in the centering around the US. It is introduced the core technology in the network centric warfare, and it is reviewed the security framework such as, the requirements of security, the characteristics security of global information grid, joint tactical radion system, net centric enterprise services, transformational communication satellite, in the basis of core technology, and analysis the effect of crypto communication relay between command node and surbornate node in NCW environment. This report support the assistance, which is considered the elements of surrounding effects in the varied crypto communication research area of NCW.