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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.
대형 RFID 시스템에서의 효율적인 인식 작업을 위한 RFID 리더들 간의 로드 밸런싱
윤상기(Sangki Yun),서현덕(Hyundoc Seo),하지훈(Jihun Ha),김효곤(Hyogon Kim) 한국정보기술학회 2009 한국정보기술학회논문지 Vol.7 No.1
A large scale RFID system consists of multiple readers and tags, in which identification range of the readers can be overlapped. Recently, a load balancing of the tags in the overlapped area has been addressed, but previous work is too conceptual to be practically used. In this paper, we propose a distributed load balancing algorithm which minimizes the number of idle queries when Adaptive Query Splitting (AQS) tag anti-collision protocol is used. Our assignment algorithm is efficient and does not incur much overhead. Performance evaluation shows that our scheme can significantly reduce the number of idle cycles in a frame, and it can highly decrease the energy consumption compared with the random tag assignment approach.
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.