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무선 메쉬 네트워크에서 적응적 경쟁 윈도우를 이용한 TCP Fairness 개선 방안
장인식,민석홍,김봉규,최형석,이종성,김병철,이재용,Jang, In Sik,Min, Seok Hong,Kim, Bong Gyu,Choi, Hyung Suk,Lee, Jong Sung,Kim, Byung Chul,Lee, Jae Yong 한국군사과학기술학회 2013 한국군사과학기술학회지 Vol.16 No.3
Wireless Mesh Networks(WMNs) is generally composed of radio nodes in the mesh topology. WMNs consists of mesh client, mesh router and gateway connected to a wired network. Each client and router relay messages to the gateway for communication. WMNs is widely used recently in many areas can provide extended coverage based on multi-hop communication and ubiquitous communication at any time and any location. However the competition and collision between each node to transmit data is inevitable when the same channel is used for transmission. The transmission opportunities and the throughput of nodes located far from gateway decrease more if the communication channel is accessed based on competitive CSMA/CA scheme using DCF(Distributed Coordination Function) provided by IEEE 802.11 MAC. In this paper, we improve the performance of the TCP fairness and throughput of the nodes with more than 2 hops by applying various algorithms for controlling contention window values. Also, we evaluate the performance using ns-2 simulator, According to the results, proposed scheme can enhance the fairness characteristic of each node irrespective of data to the gateway.
[구조강도부문] 충돌사고 재구성을 위한 차체 변형형상의 수치 모델 개발
장인식(In-Sik Jang),채덕병(Duck-byoung Chae) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The deformation pattern is one of the major factors to resume the crash configuration in collision accident reconstruction. Crash analysis are carried out using finite element method and deformed shapes are enumerated for different crash conditions. Linear equation representing force-deformation relationship is derived and deformation energy is calculated. This energy can be utilized as one of indices to identify the type of the collision accident result. Crash analysis between two vehicles is accomplished with three crash angles and three velocities for each angle condition. The deformations are measured for six selected points and numerical models are obtained for two dimensional deformation patterns by least square curve fitting. Quadratic and cubic polynomials are used as trial functions, and the fitted curves approximate deformation shapes with reasonable errors.