• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.391-398
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• 2011

In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.

• Journal of Information Processing Systems
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• v.7 no.4
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• pp.679-690
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• 2011

In this paper we consider a local area network (LAN) of dual mode service where one is a token bus and the other is a carrier sense multiple access with a collision detection (CSMA/CD) bus. The objective of the paper is to find the overall cell/packet dropping probability of a dual mode LAN for finite length queue M/G/1(m) traffic. Here, the offered traffic of the LAN is taken to be the equivalent carried traffic of a one-millisecond delay. The concept of a tabular solution for two-dimensional Poisson's traffic of circuit switching is adapted here to find the cell dropping probability of the dual mode packet service. Although the work is done for the traffic of similar bandwidth, it can be extended for the case of a dissimilar bandwidth of a circuit switched network.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2373-2376
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• 1998

This paper describes the development of the SCADA(Supervisory Control and Data Acquisition) system which can be controlled via the Internet. In this paper, the SCADA system is composed of a number of microprocessor-based RTU(Remote Terminal Unit)s, a MMI(Man Machine Interface) host, a SCADA server, and SCADA clients. There are two protocols used in the system. Each RTU and the MMI host are connected by a RS-485 line and CSMA/CD(Carrier Sense Multiple Access / Collision Detection) protocol is used to communicate with each other. TCP/IP(Transmission Control Protocol/Internet Protocol) is used among the MMI host, the SCADA server, and SCADA clients. The equipments installed in the field are controlled by a number of RTUs. The function of the MMI host is to acquire real-time data from RTUs and control them. The SCADA server supports data transfer between the networked MMI host and the SCADA client on the web-server through TCP/lP. Data transfer is possible regardless of the type of network only if there are TCP/lP Winsock-compatible stack driver. The SCADA client is implemented as the shape of web-page by means of JAVA language. Therefore, it runs on a web-browser such as Netscape and Explorer, and allows a number of users to access this SCADA system.