• Journal of Korea Multimedia Society
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• v.6 no.7
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• pp.1231-1238
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• 2003

As the demand on multicast services increases to support the terminal mobility in the midst of the development of wireless mobile communication technology, many new methods have been studied. However, previous methods occur delay and packet loss during re-joining to multicast service group when moving mobile node. In this paper, we will propose a scheme that decreases packet loss using regional registration method. Proposed scheme modified signaling message of previous regional-registration and added caching. In case move to same GFA, we can prevent packet loss by keeping registration to FA until perfectly registration ends. Also, In case move to other GFA, we can reduce packet loss by using cache. Therefore, we can receive efficient multicast service.

• Journal of information and communication convergence engineering
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• v.8 no.3
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• pp.245-250
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• 2010

To support various bandwidth requirements for many kinds of devices such as PC, notebook, PDA, cellular phone, a transcoding proxy is usually necessary to provide not only adapting multimedia streams to the client by transcoding, but also caching them for later use. Due to huge size of streaming media, we proposed the 3 kinds of segmentation - PT-2, uniform, bitrate-based segmentation. And to reduce the CPU cost of transcoding video, we proposed the DQS service policy. In this paper, we simulate the combined our previous two researches that are bitrate-based segmentation and DQS(Degraded Quality Service) policy. Experimental results show that the combined policy outperforms companion schemes in terms of the byte-hit ratios and delay saving ratios.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.649-651
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• 2005

본 논문에서는 실제 모바일 환경에서의 멀티미디어 컨텐츠의 요청 패턴을 분석하고 그 결과를 반영한 캐싱 알고리즘을 제안한다. 로그 데이터를 분석한 결과 컨텐츠의 연속적인 요청이 매우 짧은 시간 동안 이루어지는 시간적인 특성을 발견했으며, 컨텐츠의 다른 버전 사이의 요청 시간이 짧음을 통해서 버전별 컨텐츠의 요청이 응집되어 나타남을 확인했다. 제안된 알고리즘에서는 시간적인 특성과 컨텐츠의 인기도 특성을 반영하기 위해 측정 시간 윈도우 내에서 컨텐츠의 요청 횟수를 측정하고, 요청 횟수의 임계값 이상의 컨텐츠에 대해서 유지 시간 단위만큼의 컨텐츠 만료 시간을 정한다. 또한 공간적인 특성을 이용하여 컨텐츠가 캐시에서 제거될 때, 만료시간이 지난 컨텐츠의 다른 버전을 동시에 캐시에서 제거하는 방법을 사용한다 실험 결과 캐시의 크기가 작은 경우 제안된 알고리즘이 기존 알고리즘에 비해 $1-5\%$ 정도 성능향상을 보였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04a
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• pp.155-158
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• 2001

본 논문은 주문형 서비스의 한 분야로서 부족한 네트워크 자원을 고갈시키지 않을 뿐만 아니라 서버의 부하를 크게 경감시켜 MOD의 성능을 최대화시켜 효율적인 노래방 서비스를 위한 새로운 프락시 캐슁을 제안한다. 제안된 프락시 캐슁 구조는 일반적인 unicast 전송으로 멀티미디어 데이터를 서비스 받고 동시에 요청된 데이터가 다른 종단노드(HEN)에 이미 캐슁 되어 있을 경우 후 순위 예약 곡들을 그 종단노드(HEN)로부터 데이터를 전송 받아 스위칭 에이전트(SA)의 스위칭 테이블을 통해 미리 디스크에 저장하여 unicast 채널의 서비스 종료된 다음 후 순위 예약 곡을 서비스 받는 방법을 사용한다. 제안된 분산 프락시 캐슁은 예약 곡목이 많을수록 서버 부하와 과도한 네트워크 트래픽으로 인한 병목현상으로 인한 지연을 크게 감소시킬 수 있고, 시뮬레이션을 통해 성능의 우수함을 확인하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.12
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• pp.1476-1484
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• 1999

TV 방송 분야에서 다양한 정보와 상호 작용성을 제공하기 위해서 최근 기존 방송 내용인 A/V 스트림 외 부가정보 방송이 시도되고 있다. 데이타 방송에 대한 기존 연구는 대부분 고정된 내용의 데이타를 방송하는 환경을 가정하고 있어서 그 결과가 방송 내용의 변화가 많은 환경에 부적합하다. 본 논문에서는 데이타에 대한 접근이 반복되지 않을 가능성이 높고 사용자 접근 확률을 예상하기 어려운 상황에서 응답 시간을 개선하는 방안으로 수신 데이타를 무조건 캐쉬에 반입하고 교체가 필요한 경우 다음 방송 시각이 가장 가까운 페이지를 축출하는 사용자 단말 시스템에서의 캐슁 정책을 제안하였다. 제안된 캐쉬 관리 정책은 평균적인 캐쉬 접근 실패 비용을 줄임으로써 사용자 응답 시간을 개선하며, 서로 다른 스케줄링 기법을 사용하는 다양한 방송 제공자가 공존하는 환경에서 보편적으로 효과를 가져올 수 있다.Abstract Recently, many television broadcasters have tried to disseminate digital multimedia data in addition to the traditional content (audio-visual stream). The broadcast data need to be cached by a client system, to provide a reasonable response time for a user request. Previous studies assumed the dissemination of a fixed set of items, and the results are not suitable when broadcast items are frequently changed. In this paper, we propose a novel cache management scheme that chooses the replacement victim based on the remaining time to the next broadcast instance. The proposed scheme reduces response time, where it is hard to predict the probability distribution of user accesses. The caching policy we present here significantly reduces expected response time by minimizing expected cache miss penalty, and can be applied without difficulty to different scheduling algorithms.

• Journal of Internet Computing and Services
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• v.8 no.2
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• pp.77-87
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• 2007

A typical VOD service allows that a number of remote clients playback a desired video from a large collection of videos stored in one or more video servers. The main bottleneck for a VOD service is the network bandwidth connecting to the VOD server to the client due to the high bandwidth requirements. Many previous researches have shown that VOD server can be greatly improved through the use of multicast, broadcast, or P2P scheme. Broadcast is one of the most efficient techniques because it can transmit a stream to many users without additional network bandwidth. But the broadcast has long latency time. In order to overcome the drawback, in this paper, we propose P2Prefix broadcast scheme that can solve the service latency time, which is the problem of broadcast scheme, by using P2P caching as well as minimizing the client buffer requirement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.75-82
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• 2008

Mobile IP was proposed to overcome identity problem of original IP address system caused by mobility of wireless mobile host. To complete its network handoff procedure, it must receive a mobile advertisement broadcasted by mobile agent. Generally, in a mobile IP system, mean time delay, 500ms, in a network handoff procedure is a critical problem of wireless service such as Voip, multimedia streaming. A caching agent caches a latest mobile advertisement, and replays it by receiving solicitation message from a mobile node finishing link layer detection. But, during the procedure of mobile registration, many packets from service provider to the mobile host would be lost and handoff time delay would be increased. In this thesis, we propose an unproved caching agent technique which can forward data packets while handoff procedure, and CoA pool for fast mobile IP registration.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.709-718
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• 2002

Cluster based VOD systems require elaborate load balancing and buffer management techniques in order to ensure real-time display for multiuser concurrently. In this paper, we propose a new load balancing technique based on the dynamic buffer partitioning in cluster based VOD servers. The proposed technique evenly distribute the user requests into each service node according to its available buffer capacity and disk access rate. In each node, the dynamic buffer partitioning technique dynamically partitions the buffer to minimize the average waiting time for the requests that access the same continuous media. The simulation results show that our proposed technique decreases the average waiting time by evenly distributing the user requests compared with the exiting techniques and then increases the throughput in each node. Particularly under the overloaded condition in the cluster server, the simulation probes that the performance of the proposed technique is better two times than the Generalized Interval Caching based technique.

• The KIPS Transactions:PartA
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• v.12A no.5 s.95
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• pp.341-354
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• 2005

The main bottleneck for large scale VOD systems is bandwidth of storage or network I/O due to the large number of client requests simultaneously, and then efficient techniques are required to solve the bottleneck problem of the VOD system. Patching is one of the most efficient techniques to overcome the bottleneck of the VOD system through the use of multicast scheme. In this paper, we propose a new patching scheme, called P2P proxy patching, for improving the typical patching technique by jointly using the prefix caching and P2P proxy. In our proposed scheme, each client plays a role in a proxy to multicast a regular stream to other clients that request the same video stream. Due to the use of the P2P proxy and the prefix caching, the client requests that ive out of the patching window range can receive the regular stream from other clients in the previous patching group without allocating the new regular channels from the VOD server to the clients. In the performance study, we show that our patching scheme can reduce the server bandwidth requirement about $33\%$ less than that of the existing patching technique with respect to prefix size and request interval.

• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2524-2532
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• 1999

In this paper, we present a new buffer pool management scheme designed for video type news objects to build a cost-effective News On Demand storage server for serving users requests beyond the limitation of disk bandwidth. In a News On Demand Server where many of users request for video type news objects have to be serviced keeping their playback deadline, the maximum numbers of concurrent users are limited by the maximum disk bandwidth the server provides. With our proposed buffer cache management scheme, a requested data is checked to see whether or not it is worthy of caching by checking its average arrival interval and current disk traffic density. Subsequently, only granted news objects are permitted to get into the buffer pool, where buffer allocation is made not on the block basis but on the object basis. We evaluated the performance of our proposed caching algorithm through simulation. As a result of the simulation, we show that by using this caching scheme to support users requests for real time news data, compared with serving those requests only by disks, 30% of extra requests are served without additional cost increase.