• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1486-1491
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• 2017

In this paper, we propose a private multimedia caching scheme based on wireless local area network (WLAN) to improve the quality of service for high capacity and high quality multimedia streaming services which are recently increasing and to reduce the traffic load of core networks. The proposed caching scheme stores multimedia in the storage device mounted on WLAN APs and provides streaming services on its own without Internet connection in accordance with the request from clients. We have implemented a test network based on real commercial networks and measured the performance of the proposed caching scheme in terms of frames per second (FPS) and buffering time. According to the performance measurement results, the proposed caching scheme can reduce the average buffering time by 73.3% compared to the conventional streaming scheme. In addition, the proposed caching scheme can also improve the average FPS by 71.3% compared to the conventional streaming scheme.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.5_6
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• pp.223-231
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• 2003

Video-on-Demand (VOD) service needs high resource consumption because of high bandwidth and long playback duration which are characteristics of multimedia. Various techniques such as Patching and Channel-Reserving Patching have been proposed to reduce the demand on the network-I/O bandwidth. Patching allows new clients to join an existing multicast for realization of true VOD, and Channel-Reserving Patching reserves the part of total channel capacity of video server in order to serve the requests for popular videos on which requests of users concentrate. To improve the performance of Channel-Reserving Patching, we propose the method that determines the reserved channel capacity of video server for the popular videos in this paper. The performance of our method is evaluated in terms of average servile latency, defection ratio and fairness through simulation, and is compared with those of Patching and another Channel-Reserving Patching.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.403-408
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• 2010

The sensor nodes can be installed in the environment in which the temperature change is considerable, such as desert, urban, and data center. Particularly, because the output power becomes less than the targeted power if a temperature is increasing, link quality is degraded and packet losses are occurred. In order to compensate the temperature changes, existing schemes detect the change of the link quality between nodes and control transmission power through a series of feedback process. However, these approaches can cause heavy overhead by additional control packets. In this paper, we propose the T2PC(Temperature-aware Transmission Power Control) to keep up the link quality despite temperature variation. At each node, T2PC compensates the attenuated link quality by controlling the transmission power based on the local temperature measurement. In addition, the packet reception ratio can be improved with less control packets than ones required in existing transmission power control methods based on the feedback control.

• The KIPS Transactions:PartD
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• v.13D no.5 s.108
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• pp.725-730
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• 2006

Recently Web services have become a key technology which is indispensable for e-business. Due to its ability to provide the desired information or service regardless of time and place, integrating current application systems within a single business or between multiple businesses with standardized technologies are realized using the open network and Internet. However, the current Web Services Retrieval Systems, based on text oriented search are incapable of providing reliable search results by perceiving the similarity or interrelation between the various terms. Currently there are no web services retrieval models containing such semantic web functions. This research work is purported for solving such problems by designing and implementing an extended Semantic Web Services Retrieval Model that is capable of searching for general web documents, UDDI and semantic web documents. Execution result is proposed in this paper and its efficiency and accuracy are verified through it.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.197-212
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• 2002

Transmission Control Protocol (TCP) [1] has been tuned as a reliable transfer protocol for traditional networks comprising wired links and stationary hosts with same link characteristics. TCP assumes that congestion in the network be a primary cause for packet losses and unusual delays. TCP performs welt over such networks adapting to end-to-end delays and congestion losses, by standard congestion control mechanisms, such as slow-start, congestion avoidance, fast retransmit and recovery. However, networks with wireless and other lossy links suffer from significant losses due to bit errors and handoffs. An asymmetry network such as ADSL has different bandwidth for both directions. As a result, TCP's standard mechanisms incur end-to-end performance degradation in various links. In this paper, we analyze the TCP problems in wireless, satellite, and asymmetry links, and measure the new TCP mechanisms that are recommended by IETF Performance Implications of Link Characteristics (PILC) WG[2], by using Network Simulator 2 (NS-2).

• The Transactions of the Korea Information Processing Society
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• v.6 no.2
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• pp.385-395
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• 1999

Video-On-demand system provides electronic video rental services from remote video servers on a broadband communication networks. When we assume some situation that serve the same video stream by batching, each time single video stream became available at server-end side, we face the problem that what video stream to be scheduled at what time instant. Hence, in order to manage the resource bandwidth which is different at each stream, the policy of channel allocation became important factor. In this work, we proposed three type of scheduling policies with queueing, as are cumulative Waiting Time(CWT), Mean Waiting Time(MWT) and Predictable Popular Factor(PPF). While CWT policy is good for popular video, MWT policy was good for non-popular video. Also, we know that PPT policy has some fairness for average wait time and reneging rate of user requests.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5135-5142
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• 2011

A flexible mechanism is proposed in this paper to improve the dynamic response performance of a traffic flow control system in an urban area. The roads, vehicles, and traffic control systems are all modeled as intelligent systems, wherein a wireless communication network is used as the medium of communication between the vehicles and the roads. The necessary sensor networks are installed in the roads and on the roadside upon which reinforcement learning is adopted as the core algorithm for this mechanism. A traffic policy can be planned online according to the updated situations on the roads, based on all the information from the vehicles and the roads. This improves the flexibility of traffic flow and offers a much more efficient use of the roads over a traditional traffic control system. The optimum intersection signals can be learned automatically online. An intersection control system is studied as an example of the mechanism using Q-learning based algorithm, and simulation results showed that the proposed mechanism can improve the traffic efficiency and the waiting time at the signal light by more than 30% in various conditions compare to the traditional signaling system.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.238-243
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• 2006

휴대용 단말기의 보급과 인터넷 및 무선 네트워크의 발달로 사용자들이 사용하는 개별 장치들이 보편화되어 있으며, 이들을 서로 유기적으로 엮은 서비스가 등장하고 있다. 본 논문에서는 이러한 서비스의 한 종류로 U-Kiosk의 개념을 소개한다. U-Kiosk는 Kiosk 단말장치나 공용 PC를 사용자 개인의 PC처럼 사용할 수 있도록 하여 이들의 리소스를 직접 제어할 수 있는 기능을 제공한다. 이것을 실현하기 위한 방안으로 본 논문에서는 공용 PC에서 개인 PC의 바탕화면 설정을 포함해 모든 자원을 직접 사용할 수 있도록 하는 부분을 구현하고 설명을 하였으며, 인증 과정에서 사용자의 개입을 최소한으로 줄이는 방법에 대해서 소개한다. 이를 위하여 초소형 보안 단말기인 PANDA를 사용하였으며, Zigbee 통신을 사용하여 사용자의 위치정보를 파악하여 자동으로 인증을 하도록 하는 Transient Authentication의 개념을 도입하였다. 두 컴퓨터 간의 원격 접속을 위해서는 VNC를 이용하여 구현하였으며, 사용자가 공용 PC로부터 일정 거리 안에 있을 경우, 자동으로 원격 접속이 이루어지고, 공용 PC로부터 멀어질 경우 자동으로 접속이 종료되도록 구현하였다. 이를 기반으로 제안하는 U-Kiosk의 개념에 맞는 테스트 베드를 구축 하였다. 이는 UFC Project$^{2)}$의 일부로서 차후 완벽한 인증 인프라를 구축하여 보다 안정적이고 사용하기 편리한 U-Kiosk의 구현에 초석이 될 것이다.

• Journal of Korea Multimedia Society
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• v.7 no.5
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• pp.721-736
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• 2004

Because of increasing the notebook computer and PDA, users' requirement with respect to mobility is growing more and more. However, current IP protocol is not changed IP address and can not deliver IP packets on new location of host in case moving another network. To solve this problem, the IETF has proposed mobile IP. Today users want to be provided suitable QoS in the internet since demand of services is variety. The policy-based network management is method which can solve various problems of QoS, security, and complication of management in IP networks. This paper presents the network topology constitution, operation procedure and architecture of policy-based network management for providing internet DiffServ on mobile IP environment. In this paper we propose policy classes of policy-based DiffServ network management on mobile environment and create policy scenarios using the proposed policy description language to represent the policy classes. Finally, we implemented a policy-based DiffServ network management system on mobile IP environment.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.6
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• pp.771-781
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• 1999

오늘날의 컴퓨팅 환경은 통신 네트워크의 복잡성과 다양한 멀티미디어 서비스 처리를 위해 객체지향 기술을 분산 시스템에 도입하고 통신망을 소프트웨어 계층적 모델로 구조화한 개방형 정보 통신망 구조 연구가 활발히 진행되고 있다. 본 논문은 분산환경에서 멀티미디어 스트림 데이타를 전송하기 위한 아키텍쳐에 관한 모델의 설계 및 구현에 관한 것으로 분산 환경에서 멀티미디어 스트림 데이타를 효율적으로 전송할 수 있는 구조를 제시하고 있다. 설계한 구조는 Point-to-Point와 멀티캐스트를 지원하며 컴퓨터 통신망에서 멀티캐스트 연결을 효율적으로 관리하고 추후 기능 확장 및 기능 변경이 용이하도록 모듈화하고 유연성을 가지는 연결 관리 구조를 설계하고 구현하였다. 신호기능은 CORBA(Common Object Request Broker Architecture)의 ORB를 이용하여 실현하였으며, 데이타 전송 기능은 TCP/IP연결을 이용하였다. 이렇게 신호처리 부분과 데이타 전송 부분을 독립적으로 만들어서 하부망 기술에 독립적인 연결 관리 구조를 채택하고 있으므로 향후 다른 환경에서도 신호처리 부분을 그대로 적용할 수 있다. 분산 객체 개념을 적용하여 연결 관리 기능을 분산 객체화 하였으며 각 분산 객체간 인터페이스를 OMG(Object Management Group) IDL(Interface Definition Language)로 정의함으로써 유연성을 갖도록 하였다.AbstractThis paper proposes communication service architecture to support dynamic communication configuration and multiple connection management which are required to handle a variety of multimedia multicast application. Our communication service architecture was designed to fulfil the objectives as the following:- To build a common networking system for various multimedia multicast services- To build a platform for rapid service development and provisioning- To provide service networking independent on transport network technologiesWe implemented communication service architecture based on Common Object Request Broker Architecture (CORBA) for multimedia multicast applications. Our communication service architecture is distributed and object-oriented for extensibility and easy modification. The interfaces between the distributed objects are specified in (Object Management Group) OMGs Interface Definition Language.