• 한국통신학회논문지
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• 제19권7호
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• pp.1224-1233
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• 1994

업링크와 다운링크 경로상에 각각 가산성 백색 가우스잡음이 존재하는 이동 위성 통신로에서 TWTA의 비성형성에 의한 BPSK신호와 QPSK신호의 오율성능을 조사하였따. 다운링크 경로상의 페이딩은 Rice분포를 한다고 가정하였다. Rice 분포에 대한 근사 이산 확률분포를 고전적인 모멘트 기법(CMT)을 이용하여 처음으로 유도하였다. 최종적으로 오율은 근사 이산 확률 분포와 Gauss Quadrature Formula를 이용하여 계산하였다.

• 한국통신학회논문지
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• 제42권5호
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• pp.989-991
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• 2017

본 논문은 다양한 범위의 간섭 및 잡음 영향에서 잘 동작하는 확률 기하 기반의 순방향 다중셀 네트워크 성능 근사화 방안을 제안한다. 제안 방안은 기지국 수 및 송신전력을 변수로 갖는 다중셀 네트워크 설계 문제의 간소화에 용이하게 활용될 수 있다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.526-529
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• 2007

Due to its inherent feature of high-resolution satellite, there is strong need in some specific area to minimize the processing time required to get a standard image on hand from downlink signal acquisition. However, in general image processing system, it takes considerable time to get image data up to certain level from raw data acquisition because the huge amount of data is dealt sequentially as input data. This paper introduces the high-speed image processing system which generates the image data only for the area selected by user. To achieve the high speed performance, this system includes Quick Look Image display function with sampling, ROI selection function, Image Line Index function, and Distributed processing function. The developed RPS was applied to KOMPSAT-2 320Mbps downlink channel and its effectiveness was successfully demonstrated. This feature to provide the image product very quickly is expected to promote the application of high resolution satellite image.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.493-495
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• 2007

Future sub-meter resolution LEO missions require simultaneous dual-polarization downlink and/or multiple channel downlinks in single polarization. Especially, dual-polarization is needed to cope with bandwidth limitation due to high speed data transmission. Current KARI 13m X-Band antenna system needs to be upgraded to cope with such downlink schemes. This paper describes brief discussions on engineering work regarding how to meet the new requirements with minimum impact on current system as well as C&M (Control and Monitoring) software.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권3호
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• pp.446-458
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• 2013

Recently, energy-efficient cellular transmission has received considerable research attention to improve the energy efficiency of wireless communication. In this paper, we consider a cellular network consisting of one base station (BS) and multiple user terminals and explore the network coding for enhancing the energy efficiency of cellular downlink transmission from BS to users. We propose the network coded cellular transmission scheme and conduct its energy consumption analysis with target outage probability and data rate requirements in Rayleigh fading environments. Then, the energy efficiency in Bits-per-Joule is further defined and analyzed to evaluate the number of bits delivered per Joule of energy cost. Numerical results show that the network coded cellular transmission significantly outperforms the traditional cellular transmission in terms of energy efficiency, implying that given a Joule of energy cost, the network coded cellular transmission scheme can deliver more bits than the traditional cellular transmission.

• 디지털산업정보학회논문지
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• 제4권2호
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• pp.49-55
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• 2008

Combining OFDMA with MIMO is the key technology for the 4G mobile communication. OFDMA can relieve inherent difficulties of high-speed transmission. MIMO technology can be largely categorized into two techniques: one is STC for diversity gain and the other is SM for high frequency efficiency. In this paper, we depict various MIMO techniques of two transmit antenna and compare the computational complexity of decoding process for the techniques. Then, we analysis the performance of the techniques in the WiBro downlink environment based on OFDMA. We perfer ML algorithm which is the optimum performance and ZF algorithm of least computational complexity for SM detection.

• Journal of Communications and Networks
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• 제13권6호
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• pp.633-638
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• 2011

In this paper, we consider resource allocation with proportional fairness in the downlink orthogonal frequency division multiple access relay networks, in which relay nodes operate in decode-and-forward mode. A joint optimization problem is formulated for relay selection, subcarrier assignment and power allocation. Since the formulated primal problem is nondeterministic polynomial time-complete, we make continuous relaxation and solve the dual problem by Lagrangian dual decomposition method. A near-optimal solution is obtained using Karush-Kuhn-Tucker conditions. Simulation results show that the proposed algorithm provides superior system throughput and much better fairness among users comparing with a heuristic algorithm.

• 한국통신학회논문지
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• 제42권1호
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• pp.153-156
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• 2017

본 논문은 TCP 수정 없이 상향링크 혼잡 상황에서 확인응답 지연시간 개선을 통해 하향링크 TCP 성능을 향상시킬 수 있는 새로운 상향링크 혼잡 제어 기술을 제안한다. 제안한 방법으로 하향링크 TCP 성능이 향상됨을 실험을 통해 확인한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.344-346
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• 2004

KOMPSAT-2 (Korea Multi Purpose Satellite 2) which is scheduled to launch in 2005 year will communicate with KARI TTC (Tracking, Telemetry, and Command) station flying along sun synchronous orbits (685 km). The command from KARI TTC passes S-band omni-antenna, RF assembly, and transponder and finally reachs OBC (On Board Computer). The telemetry from KOMPSAT-2 arrives at KARI TTC through inverse procedure. In this paper, RF compatibility test between KOMPSAT-2 and KARI TTC station is demonstrated. RF interface for this test was established through real space and uplink signal test and downlink signal test and uplink & downlink signal test were performed.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (3)
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• pp.508-510
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• 2004

저궤도 위성은 고도가 낮아 하루에도 지구주위를 여러 번 회전해야 하고 주로 극궤도로 운영되므로 지상국과 접촉할 수 있는 시간에 상당한 제약을 가진다. 따라서 저궤도 위성의 경우 대부분의 시간을 지상의 모니터링이나 제어 없이 스스로 임무수행에 필요한 기능을 유지하면서 위성에서 생성되는 각종 데이터를 저장해 두었다가 다음 번 지상과의 접촉에서 위성의 실시간 상태정보 및 저장된 데이터들을 지상으로 송신하고 수행해야 할 임무를 지상명령으로 수신하는 과정을 통해서 운명된다. 본 논문은 국내 대표적인 저궤도 위성인 다목적실용위성 2호의 비행소프트웨어에서 위성의 실시간 상태정보 및 대용량 메모리에 저장된 데이터를 지상으로 전송하기 위한 전송제어 소프트웨어 및 전송 제어절차에 대해서 서술하였다.