Kwangil Lee

Cross-layer Design for Fast TCP ACK-Clocking over WiMedia UWB Networks

The WiMedia UWB technology is a viable solution to provide high throughput for multimedia streams in future wireless multimedia home networks. The quality of experience for home users, however, could not be satisfactory due to the severe degradation of the TCP throughput caused by late TCP ACK-clocking. To solve the problem, we propose a cross-layer fast TCP ACK-clocking (FTAC) scheme, where a normal MAC ACK conveys a TCP ACK in both contention-based and reservation-based MAC protocols. With FTAC, it is shown by simulation that the utilization of UWB link by TCP is greatly enhanced and the TCP throughput approaches to that of UDP, which could be the upper bound of the utilization of UWB links by higher layers.

QoS-aware bridge for high-speed powerline communication and Ethernet

Recently, high-speed powerline communication gets great attention as the home network backbone for multimedia services because of the low cost and QoS support. Since a home network is mixed with various types of networks, the high-speed powerline communication is often connected with non-QoS networks such as Ethernet. Then it is very difficult to provide end-to-end QoS for multimedia services in the home network environments since traffics are often transported to Ethernet. In this paper we deal with some QoS issues at the bridge for multimedia service when it connects high-speed powerline communication and Ethernet. Also, we introduce a QoS support Ethernet/high-speed powerline communication bridge system and shows some experimental results in this paper.

Convergence of high-speed powerline communication and WiMedia UWB for multimedia home networks

For the future premium home network services, the high volume of network bandwidth and QoS support is essential in the home networks. Even though ultra-wideband (UWB) is considered as a promising technology because of its high bandwidth up to 480 Mbps, it has a limitation of short transmission range. To overcome UWB short coverage, we converge here UWB and high-speed powerline communication. Here we introduce a high-speed powerline communication bridge, more specifically a HomePlug AV and WiMedia UWB bridge. We explain the functions of hardware and software structure of it. Our bridge provides not only the connectivity between two networks but also supports various types of QoS for multi-media services.

Design and Implementation of QoS Guaranteed Bridge System for High Speed PLC and UWB

This paper presents the software architecture of a high speed power line communication and ultra-wideband bridge system that can guarantee quality of service (QoS) for multimedia streaming in a home network. Due to recent wireless technology developments, ultra-wideband is becoming a viable solution for low cost personal area communication and home entertainment applications. Ultra-wideband has good features such as high bandwidth and low power consumption for mobile multimedia streaming, but it only supports communications over short distances due to its wave characteristics. Therefore, we have to use wired communication to extend the ultra-wideband coverage area. High speed PLC does not require any additional wiring in order to transmit a high bandwidth multimedia stream and provides sufficient bandwidth for handling a home entertainment network. Therefore a high speed PLC and ultra-wideband bridge system provides a multimedia streaming environment in the home without new wiring. The bridge system proposed can provide UPnP QoS device service and the traffic characteristic management function for end-to-end QoS for various multimedia services in the home.

A Development of Remote Ship Maintenance System Based on Ship Area Network

Abstract The rapid growth of IT technology has enabled ship automation systems to gain better functionality and safety with reducedcosts and crew numbers. Nowadays, the remote maintenance services for the systems are required because a ship may belocated in a very remote area. To provide the remote maintenance services, some issues such as how to collect the ship automation systems data, how to monitor a ships data from onshore offices, how to get support from experts while sailing,and how to reduce the maintenance costs, should be addressed. In this paper, we propose a remote ship maintenance system for remote monitoring and diagnostics of ship automation systems, which is based on both a ship area network to integrate separate system networks and a ship-shore communication infrastructure to support a remote access using satellitecommunications. Finally, we present the function test to verify the applicability of the proposed system.Keywords : Ship automation system(선박 자동화 시스템), Remote maintenance(원격 유지보수), Ship area network(선박 통합통신망), Satellite communications(위성통신)

An Agent-Based Remote Operation and Safety Monitoring System for Marine Elevators

The reliability of marine elevators are important because of the tough conditions in the marine environment. For the safety purpose, more than 26 safety lists shall be checked by persons when the ship is docked. However, its maintenance costs of the elevator increases as the rise of personnel expenses increases. Also the efficiency is highly dependent on the ability of the personnel but it is not feasible to provide expert maintenance services all the time. Therefore we propose an agent-based remote operation and safety monitoring system for the marine elevators through a shipborne gateway, called MariComm. So expert A/S personnel can inspect status of marine elevators and provide best maintenance service through the marine elevator management server whenever and wherever he wants. In our experimental analysis, we illustrated that the performance and reliability of the elevator can be improved through analyzing the accumulated data.

Design Challenges and Implementation of a Shipborne Gateway for Safe and Secure Navigational Networks

As the shipborne system becomes more complex by integrating more shipborne equipment through a network, the safety and security for the navigational system becomes an important issue. In this paper, we address some design challenges and issues for the design of safe navigational networks including cyber security. In addition, we introduce the safety and security system for navigational networks. Finally, we implement a security shipborne gateway system to interconnect with safe and secure navigational networks.

A Design and Implementation of Lightweight ENC for Android App

A large ship has an expensive electronic chart display and information system (ECDIS) installed on its bridge for the safety of navigation and uses a variety of mobile equipment for auxiliary purposes. In contrast, small- and mid-sized vessels, passenger ships and fishing boats employ mobile equipment instead of such ECDISs, as their primary devices for navigation. Small-sized vessels only require some information and features of the ECDIS owing to the performance and resource restrictions of mobile devices and the characteristics of inshore or offshore navigation. This study proposed information lightening and indexing methods for electronic navigational charts to fit mobile equipment and implemented a tailored display configuration feature for navigators.

Design and Implementation of Ethernet/High-speed Power Line Communication Bridge Supporting QoS

The QoS support is very important for the future home network services. Since home network is mixed with various types of networks, it is required to support QoS even when traffics flow over non-QoS network like Ethernet. We design and implement a bridge system providing QoS which connects non-QoS and QoS networks, more specifically Ethernet and high-speed power line communication (H-PLC). This paper explains the issues for supporting QoS and introduces a QoS bridge system for Ethernet and H-PLC.

Fermi-edge singularity of two dimensional electrons in asymmetric coupled double quantum wells

Abstract We present photoluminescence (PL) and PL excitation investigations on modulation doped GaAs AlGaAs asymmetric coupled double quantum wells. A Fermi-edge singularity is observed in the emissions between the electrons in the second sub-band and the holes bound at acceptors and in the valence band. The emission related to the holes bound at acceptors in the PL spectra is enhanced remarkably with decreasing excitation power for the sample occupied in the second electron sub-band, whereas this enhancement is much smaller for that which is unoccupied. These behaviours are interpreted as a consequence of the Fermi-edge singularity caused by the localisation of the holes for the former sample and the presence of an adjacent unoccupied sub-band for the latter.