• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.121-127
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• 2016

Satellite communication is a communication method using a satellite as a repeater communication on the air and have a communication range is wide and is possible to transmit high-speed data, so Satellite communication has been highlighted as the next generation communication. However, because the distance between the ground and the satellite is far away, there is a disadvantage that propagation delay time is very long and packet is damaged. Therefore, this study was applied to Link Relay H-ARQ system in order to complement the damage to the packet. Furthermore, we propose the Modified Link Relay H-ARQ scheme is a new scheme to supplementation the delay time. By applying the Markov channel for implementing a channel of satellite communications, the results of analyzing the performance, when applying the Link Relay HARQ scheme, BER and PER performance was improved, when applying the Modified Link Relay H-ARQ scheme, Throughput performance was confirmed improvement.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.59-64
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• 2020

Occasionally, MODEM test in satellite communication systems are needed. But Rx terminals in satellite communications are designed to obtain high SNR generally, therefore artificial bad conditions and environments are demanded for the test. One of the typical method is satellite output power reduction. Using noise generator can be another method. However, these costs a lot of money, time, and procedures in reality. In order to overcome these problems, this paper proposes an artificial noise generation method for MODEM test in satellite communication systems. First of all, SNR of a general heterodyne Rx terminal is calculated. Based on the calculation, a new model which is including variable attenuator is proposed to increase noise level. Simulation results illustrate the variable attenuator can control SNR, and these show that MODEM test in satellite communication systems be possible.

• Journal of information and communication convergence engineering
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• v.3 no.3
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• pp.123-130
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• 2005

This study performed five methods of tests and measurements to verify the improvement of connection time and bandwidth efficient of FSS (fixed satellite service) TCP/IP network by means of the cash function and the spoofing function. Tests and measurements are performed with; 1. Not to apply the cash and spoofing function 2. Apply the cash function 4. Apply both cash and spoofing function in HUB station and VSAT 5. In a typical commercial terrestrial Internet with LAN. The study results in this paper show that application of the spoofing and cash function greatly improves the bandwidth efficiency to FSS TCP/IP Internet service.

• Electronics and Telecommunications Trends
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• v.35 no.5
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• pp.83-91
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• 2020

In this paper, the contemporary deployment of broadband and Internet-of-Things (IoT) services based on the Low Earth Orbit (LEO) satellite communication network is presented. First, the global service and key technologies of small and nanosatellites are briefly addressed, and then, the progress of relevant standard technologies is explained. Finally, the overall potential for the future development of the LEO satellite communication network is highlighted.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.1-8
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• 2011

In this paper, data transmission corrugated horn antenna for RF sensor satellite system and its radiation characteristic are presented. The proposed antenna is designed, fabricated and measured to obtain the maximum gain at ${\pm}60^{\circ}$ of its radiation patterns. The result of the proposed antenna is that the return loss is less than -15 dB and the gain is over 5 dBi at ${\pm}60^{\circ}$ of its radiation patterns. From these results, it is confirmed that the proposed can be used as data transmission corrugated horn antenna for RF sensor satellite system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5610-5624
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• 2017

A novel scheme based on polarization modulation and the weighted fractional Fourier transform (PM-WFRFT) is proposed in this paper to enhance the physical layer security of dual-polarized satellite systems. This scheme utilizes the amplitude and phase of the carrier as information-bearing parameters to transmit the normal signal and conceals the confidential information in the carrier's polarization state (PS). After being processed by WFRFT, the characteristics of the transmit signal (including amplitude, phase and polarization state) vary randomly and in nearly Gaussian distribution. This makes the signal very difficult for an eavesdropper to recognize or capture. The WFRFT parameter is also encrypted by a pseudo-random sequence and updated in real time, which enhances its anti-interception performance. Furthermore, to prevent the polarization-based impairment to PM-WFRFT caused by depolarization in the wireless channel, two components of the polarized signal are transmitted respectively in two symbol periods; this prevents any mutual interference between the two orthogonally polarized components. Demodulation performance in the system was also assessed, then the proposed scheme was validated with a simulated dual-polarized satellite system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.221-227
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• 2013

In this paper, Satellite DMB/WiBro antenna and PCS/WiBro antenna improving indoor coverage for mobile services are designed and fabricated. Satellite DMB/WiBro bands repeater antenna and PCS/WiBro bands repeater antenna are proposed as a simple radiator with loading capacitor to generate LHCP(Left Hand Circular Polarization). The proposed antenna for Satellite DMB/WiBro and PCS/WiBro bands communication are fabricated by copper plate uploader type and substrate uploader type. The designed and fabricated antenna has a bandwidth of 70MHz at 1.816GHz~1.886GHz and bandwidth of 107MHz at 2.247GHz~2.354GHz. Maximum gain of radiation pattern was up to 5dBi.

• Journal of Environmental Science International
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• v.20 no.2
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• pp.199-205
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• 2011

This study used to the satellite photograph and drew up a flood inundation map. To past used digital map and showed reflect the inundation map and change of the city was difficult. The acquisition of the satellite photograph is easy from internet Site of Korea and is updated quickly. So, used the satellite photograph from flood inundation drawing up of existing and reflected the change of the city. Drawing up method of the inundation map in compliance with the research which sees the reflection of the land use which is actual is possible. Results of HEC-RAS with depth and an inundation location to be show easily. But there is to a combination method of the satellite photographs and GIS data and more objective and the subject the development of the technique which has reached fixed quantity must be researched continuously judges.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2B
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• pp.118-123
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• 2007

This paper studied the transmission control protocol over IP network to enhance the performance of the GSO satellite communication networks. The focus of this study is how to reduce the long round trip time and the transmission data rates over satellite link in the bidirectional satellite network. To do it, this study applied the caching and spoofing technology. The spoofing technology is used to reduce the required time for the link connection during communication. The caching technology is to improve the transmission bandwidth efficiency in the high transmission data rate link The tests and measurements in this study was performed in the commercial GSO communication satellite network and the terrestrial Internet network. The results of this paper show that the studied protocol in this paper highly enhance the performance of the bidirectional satellite communication network compare to the using TCP/IP satellite network protocol.

• Proceedings of the KSRS Conference
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• v.1
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• pp.356-359
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• 2006

The high prices and lack of information for satellite images prevent researchers from studying remote sensing and most non-professional people can't have the simple and easy solutions for the manipulation of satellite images. 'Satellite Imagery Information Management Center'(SIMC) project which is promoted by ETRI (Electronics and Telecommunications Research Institute) from 2002 to 2005 in Korea have the purpose to provide the satellite images freely to the public domain and the solutions for the above mentioned problems. Our project have the following five systems; Data Acquisition System, Data Preservation System, Integrated Solution System, Technology Development System, Operation Plan System. Data Acquisition System collects the satellite images such as LANDSAT, IKONOS, etc. Data Preservation System consists of database which registers the diverse satellite images. Integrated Solution System gives the user of public domain for the web service which search, order and transfer the satellite images. Technology Development System has the many processing technologies for the satellite images. Finally, the Operation Plan system has the role to plan the future of our SIMC project. In this paper, we will give the result of SIMC Project for each five systems during the fast four years from 2002 to 2005.