• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.184-190
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• 2006

Using COMS which provides multi-beam switching function, the optimal transmission channel environments which provides the high data rate communication are proposed in this paper. Also the link budget for communication transponder of COMSAT is designed. Bsaed on the channel modeling for group delay, non-linear and gain flatness characteristics, the system performances which provide high data rate (HDR) service were analyzed in Ka-band satellite channel. As the transmission data rate is increased, the degradation due to these channel characteristics is severely affect the system performance. To efficiently provide the various service via the same transmission system it is necessary to equlize the primary impairment factors. The optimum operating points of HDR satellite transmission system are implemeted and operated by considering the analyzed results on channel characteristics.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1113-1116
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• 2005

Using COMSAT which provides multi-beam switching function, the optimal transmission channel environment which provides the high data rate communication are proposed in this paper. Also the link budget for communication transponder of COMSAT is designed. Based on the channel modeling for group delay, non-linear and gain flatness characteristics, the system performances which provide various data rate services were analyzed in Ka-band satellite channel. As the transmission data rate is increased, the degradation due to these channel characteristics is severely increased. The linear component of group delay and the AM-AM component of non-linear characteristics severely affect the system performance. To efficiently provide the various service via the same transmission system it is necessary to equalize the primary impairment factors. The optimum operating points of HDR satellite transmission system are implemented and operated by considering the analyzed results on channel characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.757-766
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• 2014

To compensate signal loss due to the channel blockage in satellite communication link, we propose a cooperative communication scheme for OTM(On-The-Move) terminal in next generation satellite communication systems. The proposed scheme configures cooperation subnet with adjacent OTM terminal with the help of ground communication equipment. Shared data is spread by orthogonal spreading code, then the spread sequences are transmitted simultaneously. The receiver combines the power of received signals by EGC(Equal gain combining). The OTM terminal blockage channel is modeled by 2-state Markov chain. We evaluate the bit error rate according to the blockage channel of the channel state for the performance analysis of the proposed scheme. As a result, the proposed scheme shows better BER performance than traditional scheme with the help of subset members. In particular, the proposed scheme shows superior performance as the channel block probability is higher. However, as the number of subset members is increasing, there is a constraint because of the higher multiple access interference.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.279-282
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• 2006

분광혼합은 위성영상에서 공간해상도의 한계로 인해 다른 분광 속성을 가진 물질들이 하나의 픽셀 내에 존재하게 될 때 발생하게 된다. 이러한 문제를 해결하고자 분광분리 알고리즘을 통해 픽셀의 순수한 영역만을 선정하여 정확도 높은 탐지가 가능하도록 하는 분광혼합분석(Spectral Mixture Analysis, 이하 SMA)을 고해상도 영상에 적용하였다. 본 연구는 산림의 훼손이 심각한 강원도 정선군 임계지역의 QuickBird 다중분광 위성영상을 이용하였다. 주성분분석(Principal Component Analysis, 이하 PCA)으로 생성된 결과 영상의 1, 2, 3번 밴드를 추출한 후에 밴드간의 Scatter plots 내에서 끝지점에 위치하는 Endmember를 3개(나지, 산림, 초지) 선정하였다. 선정된 Endmember를 토대로 작성된 fraction 영상을 이용하여 강원도 임계지역의 산림훼손으로 초지와 나지로 변화된 지역을 탐지하여 보았다.

• Journal of the Korean Professional Engineers Association
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• v.37 no.2
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• pp.47-53
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• 2004

Space-based radio-positioning and time transfer system, Provide accurate position, velocity, and time(PVT) information \longleftarrowunlimited number of suitably equipped ground, sea, air and space users, by the U.S Department of Defense(DoD), Comprises major system segments\longrightarrowSpace, Control and User

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.15-21
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• 2017

Following the successful launch of KOMPSAT-3 in May 2012, KOMPSAT-5 in August 2013, and KOMPSAT-3A in March 2015 have succeeded in launching the integrated operation of optical, radar and thermal infrared sensors in Korea. We have established a foundation to utilize the characteristics of each sensors. In order to overcome limitations in the range of application and accuracy of the application of a single sensor, multi-sensor image fusion techniques have been developed which take advantage of multiple sensors and complement each other. In this paper, we introduce the development of software (InFusion) for multi-sensor image fusion and valued-added product generation using KOMPSAT series. First, we describe the characteristics of each sensor and the necessity of fusion software development, and describe the entire development process. It aims to increase the data utilization of KOMPSAT series and to inform the superiority of domestic software through creation of high value-added products.

• Journal of Satellite, Information and Communications
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• v.4 no.1
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• pp.1-7
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• 2009

As the information age comes out, the aspect of future war brings about the many changes in terms of war-fighting environment. Accordingly, information superiority and intelligence-centric warfare have been important and new war-fighting concept such as NCW(network centric warfare) have been turned up. This paper proposed all-weather core-strategy communications systems guaranteeing not only the real-time transmission of the information collected in a battlefield and expansion, automation, and rapidity of a battlefield but also broadband, mobility, survivability, and flexibility. The proposed military satellite communications system is classified into wideband mass capacity link, survivability, and the system supporting OTM(on the move) communication for the real-time transmission of battlefield information. This paper analyzed the essential operation concepts and core schemes of the U.S. Army's next generation system, TSAT(Transformational Satellite Communication System). Base on the analysis results, this paper proposed that the architecture of next generation military satellite communications systems for NCW have to provide the data rate, anti-jamming capability, network control and management capability which are optimally adaptable for the wireless channel environments such as jamming and interference and to support the variety of platforms like high-speed mobile vehicles, micromini devices, super-high speed unmanned aerial vehicles. Finally, this paper also proposed that next generation military satellite communications systems need the technologies such as the adaptable multi-antenna, laser link, and next-generation anti-jamming waveform.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.44-49
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• 2008

In this paper, the performance for the non-linear satellite channel including the characteristics of group delay and gain ripple of transponder is analyzed with multi-level QAM-OFDM schemes. Comparing the BER performances between general OFDM and CI(Carrier Interferometry)-OFDM for various QAM schemes, the degree of performance improvement is presented in AWGN environments for specified nonlinear characteristics. The simulations are performed with the 36MHz bandwidth of transponder channel and 120Mbps transmission rate for QPSK, 8QAM, 16QAM, 32QAM, 64QAM schemes between normal and worst case condition. It is shown that the improvement measure by the CI-OFDM for the group delay of channel and nonlinear characteristic of HPA outperforms that for the gain ripple in the case of higher level QAM scheme in normal condition. And the simulation results show that the additional techniques like the channel coding and compensation scheme against the nonlinear characteristic are required for 32QAM and higher level QAM in worst case condition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.464-472
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• 2018

Future spaceborne satellite synthetic aperture radar(SAR) system is expected to acquire high-resolution images over wide swath areas. Conventional SAR systems suffer from ambiguity problems in both azimuth and range directions that lead to image quality degradation. Recently, multiple input multiple output(MIMO) SAR techniques having multiple orthogonal waveforms are proposed to overcome the conventional ambiguity problems in wide-swath imaging modes. In this paper, noisy orthogonal frequency division multiplex(OFDM) waveforms are developed to reduce the ambiguity problems and suppress the image quality degradation. SAR simulations are performed to evaluate the performance of the proposed technique for wide-swath SAR imaging.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.491-498
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• 2017

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military applications such as guided missiles. However, since the carrier frequencies of the GPS signals are well known and the received power is extremely low, the GPS systems are vulnerable to intentional jamming attacks. To remove jammers while maintaining GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired directions, but removes the unknown jamming signals adaptively. The performance of the proposed method is verified through computer simulation.