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MIL-STD-188-220C 기반 전술 무선 이동 Ad-Hoc 망에서 1-hop내 데이터 트래픽 감소 방법
유지상,You, Ji-Sang 한국군사과학기술학회 2008 한국군사과학기술학회지 Vol.11 No.1
The data delivery confirmation method of MIL-STD-188-220C, which is a tactical wireless mobile Ad-Hoc communication protocol, is that a source node requires the end-to-end ack from all destination nodes and the data-link ack from 1-hop neighboring destination nodes and relaying nodes, regardless of the hop distance from a source node to destination nodes. This method has the problem to degrade the whole communication network performance because of excessive data traffic due to the duplicate use of end-to-end ack and data-link ack, and the collision among end-to-end acks on the wireless network in the case of confirming a data delivery within an 1-hop distance. In order to solve this problem, this paper has proposed the method to perform the data delivery confirmation with the improvement of communication network performance through the data traffic reduction by achieving the reliable data delivery confirmation requiring the only data-link ack within an 1-hop distance. The effects of the proposed method are analyzed in the two aspects of the data delivery confirmation delay time and the data delivery confirmation success ratio.
지상 무인체계용 다중입출력 통신 시스템 설계 및 성능시험 분석
유지상,최준성,강홍구,백인철,김도종,You, Jisang,Choi, Joonsung,Kang, Hongku,Baek, Incheol,Kim, Dojong 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.5
High-capacity video, control and situation awareness data should be transmitted efficiently to control robots properly in the ground unmanned system, which requires the technology maximizing the communication range and the data transmission throughput. This technology is connected to the OFDMA(Orthogonal Frequency Division Multiple Access)-MIMO(Multiple Input Multiple Output) transmission technology under the limited bandwidth and transmission power. In this paper, we design MIMO communication system for ground unmanned systems, and investigate the data reception performance experimentally, comparing with SISO(Single Input Single Output) system. Experiment results show that the data reception performance of MIMO is significantly improved compared to that of SISO, e.g. 4dB gain of sensitivity and 5dB of SNR at the value MPR = 1, for the mobile stations with $2{\times}2$ STBC diversity.
저온 분사 공정으로 제조된 티타늄 코팅층의 치밀화에 미치는 열처리 분위기의 영향
유지상,김형준,오익현,이기안,Yu, Ji-Sang,Kim, Hyung-Jun,Oh, Ik-Hyun,Lee, Kee-Ahn 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.2
This study investigated the effects of annealing environment for the densification and purification properties of pure titanium coating layer manufactured by cold spraying. The annealing was conducted at $600^{\circ}C$/1 h and three kinds of environments of vacuum, Ar gas, and $5%H_2+Ar$ mixture gas were controlled. Cold sprayed Ti coating layer (as sprayed) represented 6.7% of porosity and 228 HV of hardness, showing elongated particle shapes (severe plastic deformation) perpendicular to injection direction. Regardless of gas environments, all thermally heat treated coating layers consisted of pure ${\alpha}$-Ti and minimal oxide. Vacuum environment during heat treatment represented superior densification properties (3.8% porosity, 156.7 HV) to those of Ar gas (5.3%, 144.5 HV) and $5%H_2+Ar$ mixture gas (5.5%, 153.1 HV). From the results of phase analysis (XRD, EPMA, SEM, EDS), it was found that the vacuum environment during heat treatment could be effective for reducing oxide contents (purification) in the Ti coating layer. The characteristic of microstructural evolution with heat treatment was found to be different at three different gas environments. The controlling method for improving densification and purification in the cold sprayed Ti coating material was also discussed.
ON THE RETRACTS AND RECODINGS OF CONTINUING CODES
유지상 대한수학회 2015 대한수학회보 Vol.52 No.4
We investigate what happens when we try to work with continuing block codes (i.e., left or right continuing factor maps) between shift spaces that may not be shifts of finite type. For example, we demonstrate that continuing block codes on strictly sofic shifts do not behave as well as those on shifts of finite type; a continuing block code on a sofic shift need not have a uniformly bounded retract, unlike one on a shift of finite type. A right eresolving code on a sofic shift can display any behavior arbitrary block codes can have. We also show that a right continuing factor of a shift of finite type is always a shift of finite type.
유지상,김준환 에스케이텔레콤 (주) 2007 Telecommunications Review Vol.17 No.5
본 논문에서는 다시점 비디오 부호화를 위한 적응적 조명보상기법을 제안한다. 다시점 비디오의 특성상 시점 간에 조명의 차이가 존재하고, 이는 부호화 효율을 떨어뜨리는 원인이 된다. 이와 같은 성능 저하를 해결하기 위해 다시점 비디오 부호화 기법 가운데 조명 차이를 보상하여 압축 효율을 높이는 조명보상기법이 연구되고 있지만 계산 복잡도가 높은 단점이 있다. 본 논문에서는 조명보상기법의 계산 복잡도를 줄여 부호화 효율을 높이는 적응적 조명보상기법을 제안한다. 히스토그램 차이를 이용하여 프레임 단위로 조명 보상기법의 적용 여부를 판별함으로써 선택적으로 조명보상을 수행한다. 제안한 조명보상기법을 통해 다시점 비디오 부호화 효율을 높일 수 있었다.