• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.250-252
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• 2006

ALC(Asyncronous Layered Coding)는 LCT(Layered Coding Transport)기반의 폭넓은 확장성과 다양한 전송속도로 신뢰성 있는 멀티캐스트 전송을 주 목적으로 한다. ALC는 다른 RMT 프로토콜과는 달리 재전송을 하지 않고 receiver-driven 형태의 혼잡제어를 하기 때문에 신뢰성을 제공하기 위해 FEC(Forward Error Correction) 스킴를 이용한다. 본 논문은 신뢰적인 멀티캐스트 전송 프로토콜을 위해 ALC와 FEC 스킴 중 하나인 LDPC 코드를 이용하여 구현한다. 인코딩 비율(Encoding ratio)에 따라 일정 수준 이상의 복구 성공 확율에 대해 최대 허용 가능한 패킷 손실률을 측정하여 신뢰치를 측정한다. 마지막으로 일대다의 파일 전송 시, TCP와 비교하여 본 구현물의 유연성과 효율성에 대해 분석 및 평가한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.249-252
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• 2010

최근 광대역 미디어 보급이 확산되고 통신 속도가 향상됨에 따라 인터넷은 원 소스 멀티서비스를 가능하게 해주는 새로운 매개체로 떠오르고 있다. 이러한 원 소스 멀티서비스의 예로, 다수의 공중파 텔레비전, 라디오 채널들은 물론, 인터넷 사업자에 의해 제공된 멀티미디어 콘텐츠들이 인터넷을 통하여 방송 서비스로 제공되고 있다. 인터넷 이용 인구의 급격한 증가와 더불어 원 소스 멀티서비스를 제공하는 인터넷 방송에 수요도 증가 추세에 있다. 이러한 배경에서 등장한 대표적인 서비스로, 인터넷 프로토콜을 기반으로 한 IPTV를 들 수 있다. 본 논문에서는 VoD 멀티캐스트 서비스를 지원하는 통신시스템에서 중간 부분부터 비디오를 시청하고 싶은 사용자가 연속적인 서비스를 요청하는 경우 발생 가능한 지연시간을 효율적으로 줄임으로써 서비스의 연속성을 보장할 수 있는 방법을 제안한다. 제안된 기법은 서비스 요청 대기시간을 줄이는데 있어, 기존의 기법과 본 제안 기법을 비교하였다.

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.53-61
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• 2018

In this paper, the author proposes an efficient group key agreement scheme in a mobile environment where group members frequently join and leave. This protocol consists of basic protocols and general ones and is expected to be suitable for communications between a mobile device with limited computing capability and a key distributing center (or base station) with sufficient computing capability. Compared with other schemes, the performance of the proposed protocol is a bit more efficient in the aspects of the overall cost for both communication and computation where the computational efficiency of the scheme is achieved by using exclusive or operations and a one-way hash function. Also, in the aspect of security, it guarantees both forward and backward secrecy based on the computational Diffie-Hellman (CDH) assumption so that secure group communication can be made possible. Furthermore, the author proves its security against a passive adversary in the random oracle model.

• The KIPS Transactions:PartC
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• v.11C no.4
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• pp.409-418
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• 2004

Multicast services are provided on the Internet in fast increasing . Therefore it is important to keep security for multicast communication. Member leaving is deeply associated with scalability problem for group key management. If one member of the group is removed, new group key has to be generated and distributed to all remaining members of group. Minimizing the number of messages and operation cost for generation of the composite keys are important evaluating criteria of multicast key management scheme since generation and distribution of new keys for rekeying require expensive operation. Batch removal can reduce these important parameters rather than removing members sequentially In fashion one after another. In this paper, Hamming distance is calculated between eve교 members to be removed. The members with Hamming distance less than threshold are selected for rekeying procedure. With running the round assignment algorithm In the case of removing several members simultaneously, our model has advantages of reducing the number of message and operation cost for generation of the composite keys and eliminating possibility of collusion attack for rekeying.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.930-938
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• 1999

미래의 통합 이동 통신망은 멀티미디어 데이터 서비스를 하기 위해 작은 셀로 망이 구성될 것이다. 셀이 작은 경우, 이동 호스트의 셀간 이동이 상대적으로 증가해서 잦은 핸드오프 처리로 서비스 중단이 빈번히 발생할 수 있을 뿐만 아니라 자원의 낭비도 많아지게 된다. 따라서 이런 문제를 해결하기 위해 이동 호스트의 이동성을 예측해서 멀티캐스트 연결을 구성해서 사전 핸드오프 처리를 하는 SGMH방법을 제안한다. SGMH방법의 성능 평가를 위해 핸드오프 처리과정의 데이터 및 제어 정보의 흐름을 분석하고, 망 종속 인자들을 도입해서 버퍼 오버헤드와 서비스 중단 시간 면에서 기존 핸드오프 방법들과 비교했다. 비교 분석한 결과는 제안한 방법이 기존의 방법보다 기지국에서의 버퍼 오버헤드뿐만 아니라 서비스 중단 시간을 줄일 수 있음을 보였다.Abstract For mobile multimedia data services, future mobile communication networks will consist of small cells. In case of smaller cell size, the number of user movements between cells will increase and more network resources will be consumed for processing frequent handoffs. This processing delay will cause frequent connection service disruptions. To solve these problems, a multicast-based handoff method ,called SGMH(Sub-Group Multicast-based Handoff), is suggested. SGMH method estimates future movements of mobile hosts and setups a dynamic multicast connection tree for procesing handoffs. For performance evaluation, we represent flows of data and control messages as timing diagrams and introduce several network related factors. In terms of buffer overhead and service disruption time we compared the SGMH method to other methods. The results show that SGMH method has better performance in that it can reduce consumption of network resources and minimize service disruption time.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.277-286
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• 2000

Switch-based network is suitable for the environment of demanding high performance network. Traditional shared-medium Local Area Networks(LANs) do not provide sufficient throughput and latency. Specially, communication performance is more important with multimedia application. In these environments, switch-based network results in high performance. A kind of switch-based network provides higher bandwidth and low latency. Thus high-speed switch is essential to build switch-based LANs. An effective switch design is the most important factor of the switch-based network performance, and is required for the multicast message processing. In the previous cut-through switching technique, switch element reconfiguration has the capability of multicasting and deadlock-free. However, it has problems of low throughput as well as large scale of switch. Therfore, effective multicating can be implemented by using divided hardware unicast and multicast. The objective of this thesis is to suggest switch configuration with these features.

• The KIPS Transactions:PartD
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• v.12D no.2 s.98
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• pp.289-302
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• 2005

The mobile agent has very various performance according to the element of communication number of times between hosts, quantity of transmission data agent's size, network state etc. specially, migration method is caused much effect in whole performance of distributed system. Most existing migration methods have simplicity structure that it moves doing to accumulate continuously result after achieving task by visiting host in the fixed order. Therefore, in case there are situation such as fault, obstacle, and service absence etc. This can be inefficient due to mobile agent increased network required time. In this paper, we design and implementation Multicast Migration Model for minimizing network required time by solving this problems. Multicast Migration Model includes components such as mobile agent including call module and naming agent, which provides object replication information and distributed server's location transparence. And we evaluate and compare with existing migration method applying prototype system to verify implemented migration model.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.191-201
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• 2013

In this paper, we propose a location based multicast routing protocol, called Geomulticast, in mobile ad-hoc wireless networks. The main features and contributions of the proposed geomulticast are as follows. First, support data transmission to only the specific mobile nodes within a target area. Second, establish stable routing route by using mobility information of nodes. Third, reduce control overhead, power for construction of routing route by using geomulticast guided line information. Fourth, present a theoretical model for establishing stable route. The performance evaluation of the proposed geomulticast is executed by using OPNET simulation and theoretical analysis, and the results of simulation and theoretical analysis have similar patterns. And we can see that data packets are efficiently transmitted to specific user groups within a specific area.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.515-518
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• 2011

Recently we all agree with the fact that conference is the most important communication method in industrial fields. With improvement of information technology, the conference using computer-aided system has been increased. Therefore, software, which can support the conference, is highly needed. In our work, we implemented the display sharing system in WLANs that sends the presenter's display to all audience in real-time manner. In order to share the display, we used multicast transmission which shows good performance in one to many communications. And also, to solve the data error and loss problem, which are weak points of multicast transmission, we used Reed-Solomon coding scheme.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2158-2170
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• 1999

It has been required more reliable communication on processes and improvement of system performance as distributed systems using multicast protocol became widespread. In distributed environment maintaining data consistency through asynchronous execution of processes and coordinating the activities of them would occurs. This paper proposes a total ordering algorithm, TORMP, in order to resolve these problems. TORMP takes advantage of multicast protocol and uses an effective token passing method. It reduces a process delaying time before transmitting its message by multicasting a token simultaneously to every process that initiates the request of the message. Moreover, the processes receiving the token start multicasting the message at the same time, which causes to cut down the overall transmission dely. In case that one process sends a message, TORMP hardly uses the procedure of controlling for ordering. It gives fairly the right of sending messages to all processes in a group with utilizing vector clock. In TORMP, unlike other algorithms, the number of packets generated during ordering process does not depend on the number of processes.