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문현선(Hyunsun Moon),이경수(Kyungsoo Lee),민주홍(Juhong Min),조치호(Chiho Cho),서현덕(Hyundoc Seo),김효곤(Hyogon Kim) 한국정보기술학회 2008 한국정보기술학회논문지 Vol.6 No.6
In this paper, we present the first measurement study of the Internet access performance of real-life WiMax and HSDPA as the next generation Internet access method, both of which began to be commercially offered to public in Korea. We run three different types of traffic to shed light on various aspects of the two technologies. Since our study is based on the performance as observed at one particular locale, direct and fair comparison between these two competing technologies is not possible. In spite of the limitation, however, we could obtain a few interesting observations. First, the access delay from the wireless station to the first-hop router is high and accounts for the large part of the end-to-end delay for both HSDPA and WiMax. Second, the performance is highly variable, both in terms of delay and throughput. Third, HSDPA and WiMax are observed to suffer relatively frequent and elongated packet loss bursts and packet reorderings, respectively. Fourth, the asymmetry between the upload and download throughput performance of HSDPA could pose a problem for symmetric applications such as P2P. We expect the problem to go away with the advent of HSUPA. The asymmetry problem does not seem to exist for WiMax. In summary, the current HSDPA and WiMax commercial offerings seem to have room for improvement, still being in the initial deployment phase.
Interject: 802.11기반 다중 홉 네트워크상의 협동적인 MAC 재전송 기법
서현덕(Hyundoc Seo),윤상기(Sangki Yun),민주홍(Juhong Min),문현선(Hyunsun Moon),김효곤(Hyogon Kim) 한국정보기술학회 2008 한국정보기술학회논문지 Vol.6 No.6
Recently, co-operative transmission have gained much attention. In IEEE 802.11 network, wireless transmission intended for a particular destination node can be overheard by other neighbor node. We consider a novel method that is orthogonal to the existing approaches. Instead of following a single routed path, the transmission on each hop is broadcast, where a node farthest in the direction of the destination forwards it. In our proposed scheme, we let an intermediate node interject the frame that is considered to have been lost. the intermediate node transmits the lost frame, quickly resolving the transmission failure. Simulation experiments show that Interject significantly increases network capacity compared to existing algorithm.
The important role of Asp 280 and Arg 282 residues in the E. coli leader peptidase
Sung, Meesook,Moon, Hyunsun 關東大學校 醫科大學 醫科學硏究所 1999 關東醫大學術誌 Vol.3 No.1
박테리아 leader peptidase는 모든 생물에 필수적인 요소이고, periplasm이나 extracellular space에 위치하여 항생제 제조에 target으로 이용되기 때문에 특히 leader peptidase의 활성 메카니즘의 연구가 중요시 되고 있다. 최근의 leader peptidase-inhibitor complex의 X-ray crystal 구조를 보면, E. coli leader peptidase Asp 280과 Arg 282가 서로 가까이 위치하고 또한 그들의 residues는 conserved domain에서 매우 높은 consensus sequence 이기 때문에, leader peptidase protein의 activity를 나타내는 중요한 역할을 하리라고 가정하였다. 이 가설을 증명하기 위하여 sire-directed mutagenesis를 이용하여 다음과 같은 leader peptidase double mutants를 만들었고 [(D280C, R282C), (D280E, R282K) and(D280R, R282D)], 니켈 컬럼으로 정제한 후 in vitro assay 한 결과 모든 mutants가 inactive 함을 보였다. 따라서 E. coli leader peptidase Asp 280 과 Arg 282는 그 protem의 activity를 나타남에 있어서 중요한 residues라고 제시한다.