• Journal of Communications and Networks
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• v.15 no.6
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• pp.614-634
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• 2013

The proliferation of real-time multimedia services requires huge amounts of data transactions demanding strict quality-of-service (QoS) guarantees. Multicast transmission is a promising technique because of its efficient network resource utilization. However, high head-of-line (HOL) blocking probability and lack of service-specific QoS control should be addressed for practical implementations of multicast networks. In this paper, a topology aware fanout set division (TAFD) scheme is proposed to resolve these problems. The proposed scheme is composed of two techniques that reduce HOL blocking probability and expedite packet delivery for large-delay branches regarding multicast tree topology. Since management of global topology information is not necessary, scalability of the proposed scheme is guaranteed. Mathematical analysis investigates effects of the proposed scheme and derives optimal operational parameters. The evaluation results show that the TAFD scheme achieves significant delay reduction and satisfies required delay bounds on various multicast networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.4864-4882
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• 2016

In this work, we consider the optimization problem of minimizing energy consumption for real-time multicast over wireless multi-hop networks. Previously, a distributed primal-dual subgradient algorithm was used for finding a solution to the optimization problem. However, the traditional subgradient algorithms have drawbacks in terms of i) sensitivity to iteration parameters; ii) need for saving previous iteration results for computing the optimization results at the current iteration. To overcome these drawbacks, using a joint network coding and scheduling optimization framework, we propose a novel distributed primal-dual Random Deflected Subgradient (RDS) algorithm for solving the optimization problem. Furthermore, we derive the corresponding recursive formulas for the proposed RDS algorithm, which are useful for practical applications. In comparison with the traditional subgradient algorithms, the illustrated performance results show that the proposed RDS algorithm can achieve an improved optimal solution. Moreover, the proposed algorithm is stable and robust against the choice of parameter values used in the algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1399-1406
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• 2009

In the internet broadcast, efficient and scalable mechanism of multicast is needed for the communication between groups. Furthermore, Optimization of the multicast tree is required to improve the performance of overlay multicast. This optimization is well-known as NP-complete. If a node in the tree has limited out-degree, a user who wants to join the group has to find parent user who has already joined. In this paper, the users who want to join the group need to setup their level using delay test from source node. And then new users can find candidate parent nodes effectively using ACK-SEND approach and take proper position by comparing level. The closer node of the user to root node should be located in lower level. Also, even if a barrier is caused, fast recovery will be guaranteed using ACK-SEND approach. Through this, the newcomer node can fine their location in the multicast tree and join the group fast and effectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.27-33
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• 2004

A new multicast scheme for mobile nodes is proposed to support real-time communication in a more efficient way. In the proposed multicast scheme, the Xcast (a very flexible data plane mechanism) is integrated with the SIP (a very flexible control plane protocol) to support multicast for mobile nodes. The simulation results verify that the proposed scheme reduces unnecessary network traffic and achieves low latency of packets in the network.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.446-459
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• 2016

In this paper, we propose virtual direction multicast (VDM) for video multicast applications on peer-to-peer overlay networks. It locates the end hosts relative to each other based on a virtualized orientation scheme using real-time measurements. It builds multicast tree by connecting the nodes, which are estimated to be in the same virtual direction. By using the concept of directionality, we target to use minimal resources in the underlying network while satisfying users' quality expectations. We compare VDM against host multicast tree protocol.We simulated the protocol in a network simulator and implemented in PlanetLab. Results both from simulation and PlanetLab implementation show that our proposed technique exhibits good performance in terms of defined metrics.

• Journal of Ubiquitous Convergence Technology
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• v.2 no.2
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• pp.88-96
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• 2008

IPTV Content delivery systems over wired networks confront scalability problems due to their high network bandwidth requirement for real-time services. Especially, VoD service provides Trick Mode features such as pause, fast forward and similar operations. However, Trick Mode services are delivered by the method of unicast only for controlling of the stream. With a point of views, this paper propose a new real-time multimedia streaming architecture over IP Networks, which tries to achieve bandwidth efficiency and supporting for mass clients better than traditional unicast services. The proposed methods divide the Transport Stream into a series of segments. After that, this divided partial Transport Stream makes multicast streaming periodically. Meanwhile Set-top Box of a client makes a rearrangement orderly by using Presentation Time Stamp field from the served Transport Stream packets. While the current Transport Stream segment is playing, it should be guaranteed that the next segment is downloaded on time. Consequently, the original video content can be played out continuously. The detail introduction of a new real-time multimedia streaming system with analysis and simulation follows as below.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1B
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• pp.27-38
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• 2005

IP Multicast has not been deployed because of hardware problems. So a new scheme that is called Overlay Multicast for group communication has been emerged. It supports IP Multicast functions, which is located on application level. For developing it, we have been focused on efficient overlay tree construction among group members with low stretch and stress. However, we should consider a variety of transmission or receipt condition since a real internet environment has users with various transmission/receipt rates. Thus, we make one-time source specific tree depending on required bandwidth informationof group members when a member requests data transmission. Our mechanism provides satisfied data quality limited maximum transmission rate of the source to each group members. Furthermore, we manage a large group enough as distributing control information to cores that are designated membersfor maintaining host member information. Lastly, we prove that our tree guarantees data quality to each group members, and show low tree consruction time is required. In addition, for evaluating group scalability, we analyze control information increasing rate via group size, and validate its scalability.

• Journal of Communications and Networks
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• v.8 no.1
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• pp.116-122
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• 2006

Most of the multimedia applications require strict quality of service (QoS) guarantee during the communication between a single source and multiple destinations. This gives rise to the need for an efficient QoS multicast routing strategy. Determination of such QoS-based optimal multicast routes basically leads to a multi-objective optimization problem, which is computationally intractable in polynomial time due to the uncertainty of resources in Internet. This paper describes a network model for researching the routing problem and proposes a new multicast tree selection algorithm based on genetic algorithms to simultaneously optimize multiple QoS parameters. The paper mainly presents a QoS multicast routing algorithm based on genetic algorithm (QMRGA). The QMRGA can also optimize the network resources such as bandwidth and delay, and can converge to the optimal or near-optimal solution within few iterations, even for the networks environment with uncertain parameters. The incremental rate of computational cost can close to polynomial and is less than exponential rate. The performance measures of the QMRGA are evaluated using simulations. The simulation results show that this approach has fast convergence speed and high reliability. It can meet the real-time requirement in multimedia communication networks.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.460-462
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• 2004

분산 환경에서의 효과적인 통신 방법인 멀티캐스트 프로토콜이 그동안 많이 연구되었다. 하지만 인터넷 기반 네트워크의 급속한 발달로 실시간 데이터를 요구하는 환경으로 변화함에 따라 실시간 멀티캐스트 프로토콜의 필요성이 대두되었다. 실시간 프로토콜 중 하나인 RFRM(Release-time based Fault-tolerant Real-time Multicast protocol)은 메시지의 신뢰성을 보장하고 뷰의 일관성을 유지하며 고장을 감내한다는 장점이 있지만 한 개의 그룹만을 지원한다는 단점을 가지고 있다. 따라서 본 논문에서는 실시간 멀티캐스트 프로토콜인 RFRM을 확장하여 멀티그룹을 지원하는 뷰 관리기능을 추가하였고, 그 성능을 분석하기 위하여 Erlang/OTP를 사용하여 구현된 결과를 TMO(Time-triggered Message-triggered Object) 모델을 사용한 실시간 시뮬레이션의 결과와 기존의 RFRM의 그룹 연산 성능과 비교하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.741-762
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• 2011

Recently, multicast routing protocols become increasingly important aspect in Mobile Ad hoc Networks (MANETs), as they effectively manage group communications. Meanwhile, multimedia and real-time applications are becoming essential need for users of MANET. Thus it is necessary to design efficient and effective Quality of Service (QoS) multicast routing strategies. In this paper, we address the scalability problem of multicast routing protocols to support QoS over MANETs. In particular, we introduce a Position-Based QoS Multicast Routing Protocol (PBQMRP). Basically, the protocol based on dividing the network area into virtual hexagonal cells. Then, the location information is exploited to perform efficient and scalable route discovery. In comparison with other existing QoS multicast routing protocols, PBQMRP incurs less control packets by eliminating network flooding behavior. Through simulation, the efficiency and scalability of PBQMRP are evaluated and compared with the well-known On-Demand Multicast Routing Protocol (ODMRP). Simulation results justify that our protocol has better performance, less control overhead and higher scalability.