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Optimum TCP/IP Packet Size for Maximizing ATM Layer Throughput in Wireless ATM LAN
이하철,Lee, Ha-Cheol The Korea Institute of Information and Commucation 2006 韓國通信學會論文誌 Vol.31 No.11B
This paper provides optimum TCP/IP packet size that maximizes the throughput efficiency of ATM layer as a function of TCP/IP packet length for several values of channel BER over wireless ATM LAN links applying data link error control schemes to reduce error problems encountered in using wireless links. For TCP/IP delay-insensitive traffc requiring reliable delivery, it is necessary to adopt data link layer ARQ protocol. So ARQ error control schemes considered in this paper include GBN ARQ, SR ARQ and type-I Hybrid ARQ, which ARQ is needed, but FEC can be used to reduce the number of retransmissions. Especially adaptive type-I Hybrid ARQ scheme is necessary for a variable channel condition to make the physical layer as SONET-like as possible.
이하철,Lee Ha-Cheol The Korean Institute of Communications and Informa 2005 韓國通信學會論文誌 Vol.30 No.9b
In this paper it is focused on the relation between CLR(Cell Loss Ratio) and blocking probability in the wireless ATM access transport. Traffic model of wireless ATH access transport is based on the cell scale, burst scale and call connection level. The CLR due to buffer overflow for wireless access node is derived for VBR traffic. The CLR due to transmission errors for wireless channel is derived. Using the CLR for both access node and wireless channel: the CLR of wireless ATM access transport is derived. The relation between CLR and blocking probability is analyzed for VBR traffic to evaluate performance of wireless ATM access transport.
이하철(Lee Ha Cheol) 한국통신학회 2010 한국통신학회 학술대회논문집 Vol.2010 No.6
본 논문에서는 ONNET 네트워크 시뮬레이션 S/W를 이용하여 Ethernet LAN의 여러 가지 구조에 대한 네트워크 성능 및 서버 성능을 정량적으로 비교분석하였다. 네트워크 성능평가 항목으로 송신트래팩(패킷/초)에 대한 수신 트래픽(패킷/초), Ethernet 지연(초) 및 Ethernet 충돌횟수가 이용되며 서버 성능으로는 부하량(bits/sec)이 평가된다. 본 시물레이션에서 사용한 네트워크 구성모델은 네트워크 성능평가를 위해서 4가지로 구분하였으며 서버 성능평가를 위해서 3가지로 구분하였다.
A MAC Layer Throughput in the 802.11g-based Wireless Internet over Ricean Fading Channel
Ha Cheol Lee(이하철) 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.6
This paper analyzes throughput performance of DCF(Distributed Coordination Function) protocol in the IEEE 802.11g-based wireless Internet over Ricean fading channel. With the same maximum transmission rate of 54 Mbps, IEEE 802.11g-based wireless access network is operated as the infrastructure mode. It is assumed that the number of stations is fixed and each station always has packets for transmission. In other words, it is operated in saturation conditions. In this evaluation , payload size is used as the variable parameter, and packet transmission probability, the ratio of direct-to-diffuse signal power and the ratio of received average energy per bit-to-noise power spectral density are used as the fixed parameters.
이하철(Lee Ha Cheol) 한국정보기술학회 2019 Proceedings of KIIT Conference Vol.2019 No.6
본 연구는 사물인터넷(IoT) 클라우드 서비스 환경에서 물리보안 모델을 구현하였다. IETF는 IoT 서비스를 위한 웹서비스 구조로서 ReST(Representational State Transfer)로 알려진 웹기반 패러다임을 채택함으로서 IoT 노드로 확장가능한 융통성있는 상호운용 시스템을 구현케 한다. 이를 위해 unconstrained 및 constrained 프로토콜 스택을 포함하는 IoT 기준 프로토콜 구조를 살펴보고 보안방안을 검토하였다. This paper implemented physical security model for securing cloud service in the Internet of Things. The IETF standards embrace a web service architecture for IoT services. The web services permit to realize a flexible and interoperable system that can be extended to IoT nodes, through the adoption of the web-based paradigm known as ReST. It also investigated security strategy and IoT protocol architecture for unconstrained and constrained IoT nodes.