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통합 필터 변별도와 그래프 컬러링을 이용한 전술통신망 백본 무선 링크의 주파수 지정 방법
함재현,박휘성,이은형,최증원,Ham, Jae-Hyun,Park, Hwi-Sung,Lee, Eun-Hyoung,Choi, Jeung-Won 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.4
The tactical communications network has to be deployed rapidly at military operation area and support the communications between the military command systems and the weapon systems. For that, the frequency assignment is required for backbone wireless links of tactical communications network without frequency interferences. In this paper, we propose a frequency assignment method using net filter discrimination (NFD) and graph coloring to avoid frequency interferences. The proposed method presents frequency assignment problem of tactical communications network as vertex graph coloring problem of a weighted graph. And it makes frequency assignment sequences and assigns center frequencies to communication links according to the priority of communication links and graph coloring. The evaluation shows that this method can assign center frequencies to backbone communication links without frequency interferences. It also shows that the method can improve the frequency utilization in comparison with HTZ-warfare that is currently used by Korean Army.
안현민,함재현,김명섭,An, Hyun Min,Ham, Jae Hyun,Kim, Myung Sup 한국정보처리학회 2013 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.2 No.8
네트워크의 고속화와 다양한 서비스의 등장으로 오늘날의 네트워크 트래픽은 복잡 다양해지고 있다. 효율적인 네트워크 관리를 위해서 QoS, SLA와 같은 정책을 적용하기 위해서는 트래픽 분석 중에서도 응용 트래픽 분류의 중요성이 크다. 현재까지 트래픽 분류에 관한 연구가 활발히 진행되어 왔는데 최근에는 플로우의 통계 정보를 이용한 트래픽 분류 방법론이 많이 연구되고 있다. 하지만 플로우의 통계 정보를 이용한 트래픽 분류 방법론에는 필히 고려해야 할 여러 문제점이 있다. 본 논문에서는 정답지 트래픽 분석을 통해 통계 정보 기반 트래픽 분석 방법론의 해결해야 하는 문제점들을 분석하고 그 해결방안에 대해 제안한다. 통계 정보 기반 트래픽 분석 방법론에서 필히 해결해야 할 문제점은 총 네 가지로 Feature들의 거리 측정 방법과 대표값 추출 방법, TCP 세션의 이상동작, 그리고 패킷 별 가중치이다. 제안하는 방법은 선정한 통계 시그니쳐 기반 트래픽 분석 시스템을 이용한 학내 망에서의 실험을 통해 그 성능을 검증한다. Nowadays, the traffic type and behavior are extremely diverse due to the growth of network speed and the appearance of various services on Internet. For efficient network operation and management, the importance of application-level traffic identification is more and more increasing in the area of traffic analysis. In recent years traffic identification methodology using statistical features of traffic flow has been broadly studied. However, there are several problems to be considered in the identification methodology base on statistical features of flow to improve the analysis accuracy. In this paper, we recognize these problems by analyzing the ground-truth traffic and propose the solution of these problems. The four problems considered in this paper are the distance measurement of features, the selection of the representative value of features, the abnormal behavior of TCP sessions, and the weight assignment to the feature. The proposed solutions were verified by showing the performance improvement through experiments in campus network.
전술 에드혹 환경에서 이종망 게이트웨이 구조 및 시뮬레이션 연구
노봉수,한명훈,권대훈,함재현,윤선희,하재경,김기일,Roh, Bong Soo,Han, Myoung Hun,Kwon, Dae Hoon,Ham, Jae Hyun,Yun, Seon Hui,Ha, Jae Kyoung,Kim, Ki Il 한국시뮬레이션학회 2019 한국시뮬레이션학회 논문지 Vol.28 No.2
전술 에드혹 환경은 개별 지상 노드 간 분산적인 형태의 자율망으로 구성되므로 네트워크의 생존 가능성 및 유연성 측면에서 효과적이나 기동 간 통신 시 제한된 출력, 지형특성, 이동성 등의 제약으로 인하여 잦은 링크 단절 및 음영지역이 발생할 수 있다. 반면 위성 통신망은 지상 기동 망에 비해 지형특성과 이동성을 극복한 광역 무선 링크를 제공할 수 있는 장점이 있으나 상대적으로 한정된 대역폭 및 고지연 특성의 망이다. 미래 전장 환경에서 기존의 단독망 형태의 제약사항을 극복하고 지휘 통제 통신의 신뢰성 및 효율성을 높이기 위해서는 이종망 게이트웨이(Heterogeneous network gateway, HNG)를 중심으로 위성 통신망을 포함한 다계층 통합 네트워크 구조가 요구된다. 본 논문에서는 전술 에드혹 환경에서 위성-전술 에드혹 망을 통합적으로 고려하고 유통되는 임무 트래픽의 플로우 특성에 기반하여 신뢰성 있는 데이터 전달이 가능한 이종망 게이트웨이 구조 및 세부 알고리즘을 제시한다. 시뮬레이션은 네트워크 수준의 시뮬레이터인 Riverbed Modeler를 활용하여 제시하는 구조의 유효성을 확인하였다. The tactical mobile ad-hoc network(MANET) consists of distributed autonomous networks between individual ground nodes, which is effective in terms of network survivability and flexibility. However, due to constraints such as limited power, terrain, and mobility, frequent link disconnection and shadow area may occur in communication. On the other hand, the satellite network has the advantage of providing a wide-area wireless link overcoming terrain and mobility, but has limited bandwidth and high-latency characteristic. In the future battlefield, an integrated network architecture for interworking multi-layer networks through a heterogeneous network gateway (HNG) is required to overcome the limitations of the existing individual networks and increase reliability and efficiency of communication. In this paper, we propose a new HNG architecture and detailed algorithm that integrates satellite network and the tactical MANET and enables reliable data transfer based on flow characteristics of traffic. The simulations validated the proposed architecture using Riverbed Modeler, a network-level simulator.
무인 지상 차량 네트워크에서 GPS 재밍에 강인한 위치기반 라우팅
이진우,정우성,김용주,고영배,함재현,최증원,Lee, Jinwoo,Jung, Woo-Sung,Kim, Yong-joo,Ko, Young-Bae,Ham, Jae-Hyun,Choi, Jeung-Won 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.4
UGVs(Unmanned Ground Vehicles) are robots that can substitute humans in reconnaissance operations of potentially dangerous and contaminated sites. Currently, there have been active research on utilizing UGVs in military environments. Much resrach has been focused on exploiting the weakness of topology-based routing and instead utilize location-based routing for the networking of UGVs. It is generally assumed that location-based routing methods can fully utilize the location information gained from GPS. However, this may not be possible in tactical environments due to enemy GPS jamming and LOS(Line of Sight) limitations. To solve this problem, we propose a location-based routing scheme utilizing low control message that can calibrate the location information using GPS information as well as location of neighboring UGV, movement direct and speed information. Also utilizing topology-based routing scheme to solve incorrect location information in GPS jamming region.
녹색 신교통 시스템 바이모달트램의 비용-수요 공급곡선을 고려한 도시 대중교통체계 적용 특성 분석
김홍석(Kim Hong-seok),김량균(Kim Ryang-Gyun),함재현(Ham Jae-Hyun),전재청(Jeon Jae-Cheong),윤희택(Yoon Hee-Taek) 한국철도학회 2010 한국철도학회 학술발표대회논문집 Vol.2010 No.7
We studied the cost-volume supply characteristic of public transportation systems focused on Bi-modal Tram in the main cities to analyze the applicability and status for the new transit system Bi-modal Tram as public transportation system. The operation cost considering the characteristic of vehicle, facilities, operation and average cost for respective public transportation system and the time cost considering the travel and transfer time are defined to the social cost, and the cost-volume supply curve is based on this social cost. The cost-volume supply characteristic between public transportation modes in the city is determined on the basis of cost-volume supply curve. Through the comparison between cost-volume supply characteristic of main transportation systems, it is analyzed about the relation between public transportation systems in the city and the characteristic for proper service provision. The application of Bi-modal Tram in the city is concluded that it is effective to reduce the social cost on the existing public transportation system.
녹색 신교통 시스템 바이모달트램의 운행을 위한 친환경 선로형 콘크리트 전용포장의 해석 및 가속시험
배을호(Bae Eul-Ho),김홍석(Kim Hong-Seok),김경만(Kim Kyung-Man),함재현(Ham Jae-Hyun),윤희택(Yoon Hee-Taek) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월
The purpose of this study is to perform 3-dimension continuum finite element numeric analysis about the section of environment-friendly track-type concrete pavement on exclusive track for operation of New transit system Bi-modal Tram and calculate the strain and stress of the section, then examine the pavement performance based on the fatigue model. In result of comparison between accelerated pavement test / measuring test about the section of pavement and the finite element numeric analysis, it is analyzed that the durability of new developed environment-friendly track-type concrete pavement is expected over 20 years.
무선 애드혹 네트워크에서 우선순위를 고려한 분산 노드 스케줄링
이원석(WonSeok Lee),김태준(Taejoon Kim),김태홍(Taehong Kim),이재생(JaeSeang Lee),함재현(Jae-Hyun Ham) 제어로봇시스템학회 2020 제어·로봇·시스템학회 논문지 Vol.26 No.2
Wireless networks are deployed in a variety of environments and must deliver high-priority data to a destination node as quickly as possible. For this reason, several node-scheduling algorithms have been proposed and some distributed scheduling algorithms make the load among nodes semi-equal through slot exchange. In spite of the distributed scheduling nature, they achieve similar performance with centralized scheduling schemes. However, the enhanced processing for high-priority packets has not been considered. Accordingly, this paper proposes an algorithm that uses multi-queues for the purpose of slot preemption in high-priority packets. Using a network simulator, we compared the performance of the proposed algorithm and the existing scheduling algorithm under various simulation environments in which the generation ratio of high priority packets was changed. Through the simulation, we can confirm that the proposed algorithm showed excellent performance.
김용정(Yong Jeong Kim),Linh-An Phan,김태준(Taejoon Kim),김태홍(Taehong Kim),이재생(JaeSeang Lee),함재현(Jae-Hyun Ham) 제어로봇시스템학회 2019 제어·로봇·시스템학회 논문지 Vol.25 No.12
Gradient Time Synchronization Protocol (GTSP) is a consensus-based time synchronization protocol in which each node adjusts its logical clock by averaging the relative clock rate of neighbor nodes in every beacon interval. This process is repeated until the network achieves convergence of time synchronization. Therefore, a short beacon interval can reduce the convergence time, although it causes high energy consumption because messages are sent frequently. In contrast, a longer beacon interval can reduce energy consumption but may result in a longer convergence time. In this paper, we propose the Adaptive Gradient Time Synchronization Protocol (AGTSP), which enables dynamic adjustment of the beacon interval of each node in a fully-distributed manner to reduce convergence time and energy. A performance evaluation demonstrates that AGTSP provides superior performance to GTSP as measured by convergence time, synchronization errors, and beacon transmission overhead.