• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.904-913
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• 2006

The QoS(Quality of Service) of VoD(Video on Demand) systems can be improved by reducing the faults that the stream service request from clients is rejected by the VoD server or lost during the service. This paper proposes a model of Dynamic Workload Balancer that can adjust the workload dynamically through the periodical monitoring of the VoD system, and so increase the throughput. The proposed model runs independently from the VoD system by adopting the agent concept. The model comprises the agency part interfacing the VoD system and the intelligence part reasoning or teaming the facts required for the adjustment of workload. An experiment of implementing a simulator was conducted to see whether or not application of the proposed model to VoD system is effective. As a result of the experiment, it was found that the throughput was relatively increased when the proposed model was applied compared to existing means.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.719-731
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• 2008

This paper defines QoE (Quality of Experience) for multi-view video streaming service over WiBro and proposes the CLO (Cross-Layer Optimization) algorithm can maximize this. Proposal CLO algorithm contains from physical layer to video layer. Under the time-varying wireless channel condition, the CLO technique takes view-wise and the temporal priority of the multi-view video into consideration in order to decide the transmission of frames and its FEC level. At the handover situation, it is shown through computer simulation that the optimal quality of the multi-view video can be achieved using the minimum amount of resources if the proposed CLO technique is applied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.928-938
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• 2008

Though services requiring Quality-of-Service (QoS) guarantees such as Voice over Internet Protocol (VoIP) have been widely deployed on the internet, most of internet backbone networks, unfortunately, do not distinguish them from the best-effort services. Thus estimating the effective capacity meaning the traffic volume that the backbone networks maximally accommodate with keeping QoS guarantees for the services is very important for Internet Service Providers. This paper proposes a test-bed based on ns-2 to evaluate the effective capacity of backbone networks and then estimates the effective capacity of an experimental backbone network using the test-bed in terms of the service standard of the VoIP service. The result showed that the effective capacity of the network is estimated as between 12% and 55% of its physical capacity, which is depending on the maximum delay guarantee probability, and strongly affected by not only the type of offered workload but also the quality standard. Especially, it demonstrated that in order to improve the effective capacity the maximum end-to-end delay requirement of the VoIP service needs to be loosened in terms of the probability to guarantee.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8S
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• pp.2722-2728
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• 2000

현재의 인터넷 망을 이용하여 음성, 화상 정보를 실시간으로 이용하고자 하는 다양한 응용이 시도되고 있다. 차세대 통신으로 주목 받고 있는 IMT-2000에서도 기존의 회선 교환망 대신 인터넷 망을 이용함으로써 경제성, 관리의 편의성, 새로운 서비스의 창출이 가능한 등의 이점이 있다. 인터넷 망이 최선의 노력(best effort)만을 제공하기 때문에 발생되는 신뢰성과 지연의 문제는 이미 많은 연구가 있어왔고 현재 어느 정도의 서비스 품질을 획득하여 VoIP(Voice Over Internet Protocol)와 같은 서비스가 실제로 이용되고 있다. 그러나 무선 통신의 경우는 이에 더하여 무선 구간에서의 자원 할당의 문제가 남아 있다. 본 연구에서는 코어 망으로 인터넷 프로토콜을 사용하는 차세대 All-IP 망에서, 무선 이동단말 간의 멀티미디어 서비스가 가능하도록 효율적인 주파수 할당을 지원하는 QoS 관리자를 설계하였다. 제안한 QoS(Quality Of Service)관리자는 요구 대역폭이 다른 멀티미디어 호 요청에 대해 융통성 있는 주파수 할당이 가능하도록 대국의 QoS 관리자와의 협상을 통해 제한된 범위 내에서 서비스 품질을 조절하여 보다 많은 호 연결 요청이 성공할 수 있도록 한다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2
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• pp.446-453
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• 2000

Mobile computing refers to an emerging new computing environment incorporating both wireless and wired high-speed networking technologies. In the near future, it is expected that mobile users will have access to a wide variety of services that will be made available over highspeed networks. The quality of these services in the high-speed networks can be specified in terms of several QoS paameters. The important QoS parameter in mobile computings is the guarantee for seamless communication which is to provide disruption free service to mobile users. A disruption in service could occur due to active handoffs. This paper proposes an extended staggened muticast approach which provides a probabilistic guarantee for disruption free service. The extended staggerd multicast approach estimates mobility direction and mobility velocity for a user. It is possible that data packets for a mobile host are multicasted to not all neighbor cells but a part of neighbor cells on the basis of these information. Therefore, the extended staggered multicast significantly reduces the static network bandwidth usage also provides a probabilistic guarantee for disruption free service.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.4
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• pp.49-56
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• 2009

Recently, studies for effective multimedia contents delivery have been widely performed in the multimedia streaming area. Overlay multicast, which can be implemented in the application layer, is method to transmit multimedia content's effectively. The Overlay multicast method can implement multicast transmission without changing the physical layer, and it has the characteristic that the application method can be diversify according to the algorithm. This paper has proposed the backup path construction method of overlay multicast for stabilized multimedia contents transmission. The proposed method can construct a backup path with the minimum searching method for guaranteed QoS(Quality of Service) and in overlay multicast so a fast and simple backup path can be constructed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.303-309
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• 2005

This paper will suggest how can we guarantee terminal QoS like ship waiting time ratio and ship residing time applying RFID(Radio Frequence Identification) technology, raising up rapidly as a fundamental solution of new growing industry, to port information system. Also, lead time of whole port logistics can be decreased for reduction of loading & discharging time resulted from productivity improvement of Twinlift G/C(Gantry Crane) and Y/T(Yard Tract) etc as applying RFID technology to terminal operation. The purpose of this paper is suggesting of new business model of u-Port that port QoS can be guaranteed from mutual agreement of each terminals RFID technology applied and focusing on the implementation plan.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.533-535
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• 2017

MQTT provides three QoS levels on top of the TCP/IP layer to ensure message delivery reliability. However, in an environment where messages are concurrently transmitted and received in a node, messages are lost due to the delivery method for QoS level. In this paper, it construct an experimental environment in which MQTT generates concurrently messages, and confirm the message reliability according to QoS level. Therefore, we analyze the message reception ratio on the subscriber side by changing number of publisher and transmission cycle of message. Experimental results show that the message reception ratio of 1 and 2 except QoS level 0 decreases as the number of publisher increases or the message transmission cycle increases.

• Journal of the Korea Computer Industry Society
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• v.6 no.3
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• pp.391-400
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• 2005

최근 몇 년 사이 컴퓨터와 초고속 통신망의 대중적인 보급으로 인하여 인터넷 사용 인구가 급격하게 증가하였고 인터넷 사용량 또한 폭발적으로 증가하였다. 이와 같이 막대한 양으로 늘어난 트래픽은 서버에 과도한 양의 부하를 발생시켜 서비스 전반에 걸친 성능 저하를 가져왔다. 따라서 서버에 많은 양의 트래픽이 발생하더라도 정상적인 서비스를 제공할 수 있도록 하는 것이 필요하다. 본 논문에서는 이러한 서버의 트래픽 폭주로 인한 서버 과부하 문제를 해결하기 위해 수락 제어 알고리즘을 이용한다. 수락 제어 기법은 컨텐츠 변환이나 로드 밸런싱과 같이 수동적으로 부하를 덜어주거나 분산시키는 방식이 아닌 트래픽에 제한을 가하여 능동적으로 서버의 부하를 조절하는 방식이다. 클라이언트에 의한 연결 요청이 이루어질 때 서버의 부하 상태를 평가한 후 서버가 수용 가능한 수준이면 클라이언트 새로운 연결 요청을 수락하여 이를 서비스할 수 있도록 한다. <중략> 또한 서비스 요청에 제한적인 정책을 따를 경우 서버의 부하 변화에 빠르게 반응하지만 QoS(Quality of Service)의 향상을 얻을 수 있는 반면 더 많은 서비스 요청을 수용하는 정책을 취할 경우 서버의 부하 변화에 대한 반응이 느리지만 throughput이 증가하는 이득을 얻을 수 있게 된다. QoS와 throughput가 서로 tradeoff 관계에 있다는 것을 알 수 있다. 또한 요구되는 서비스의 성격에 따라 즉 더 높은 수준의 QoS 보장이 중요한 서비스인가 아니면 더 높은 수준의 throughput 보장이 요구되는 서비스인가에 따라 다른 수락 제어 정책을 적용하는 것이 가능하게 된다.

• Journal of Korea Multimedia Society
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• v.7 no.4
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• pp.518-531
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• 2004

This paper discusses a testbed architecture for implementing scalable service differentiation in the Internet. The differentiated services (DiffServ) testbed architecture is based on a model in which a bandwidth broker (BB) can control network resources, and the ALTQ can reserve resources in a router to guarantee a Quality of Service (QoS) for incoming traffic to the testbed. The reservation and releasemessage for the ALTQ is contingent upon a decision message in the BE. The BB has all the information in advance, which is required for a decision message, in the form of PIB. A signaling protocol between the BB and the routers is the COPS protocol proposed at the IETF. In terms of service differentiation, a user should make an SLA in advance, and reserve required bandwidth through an RAR procedure. The SLA and RAR message between a user and the BB has implemented with the COPS extension which was used between a router and the BB. We evaluates the service differentiation for the video streaming in that the EF class traffic shows superb performance than the BE class traffic where is a network congestion. We also present the differentiated service showing a better packet receiving rate, low packet loss, and low delay for the EF class video service.