• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12B
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• pp.1100-1105
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• 2003

In this paper, we propose a solution, called DQDMR, for generating delay-constrained bandwidth- appropriated multicast routing trees to reduce end-to-end delay and conserved bandwidth resources. At the current router system the router keep the information of link which neighboring node in the routing table to guarantee QoS(Quality of Service). When we construct multicast tree, DQDMR algorithm dynamically adjusts the path in the least delay and appropriate bandwidth. Through simulations comparing to another multicast algorithms, we reach a conclusion that DQDMR algorithm can simply and dynamically adjusts the construction of multicast tree in hight-speed and conserve bandwidth resources.

• Journal of Korea Game Society
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• v.16 no.4
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• pp.57-68
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• 2016

As the size of the data used in the game application increase gradually, the physical resources of game server grow. Accordingly, it is necessary to/it is required to introduce I/O virtualization in game server to improve I/O performance of the server. But it is difficult to ensure high responsiveness in game server where I/O delay change from time to time. To maximize the benefit of I/O virtualization, guaranteeing I/O response time is very important and it is necessary to have I/O scheduling techniques to manage the I/O latency in the order of priority of virtual machines. In this paper, we propose an efficient delay-constrained scheduling algorithm in a virtualization environment to ensure maximum I/O latency. In addition, a reduced amount of loss of the packet was found to increase the fairness of scheduling in the experiments with the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1134-1143
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• 2000

We propose a scheduling algorithm, Bandwidth Allocation Scheme (BAS), that guarantees bounded delay in a switching node. It is based on the notion of the GPS (Generalized Processor Sharing) mechanism, which has clarified the concept of fair queueing with a fluid-flow hypothesis of traffic modeling. The main objective of this paper is to determine the session-level weights that define the GPS sewer. The way of introducing and derivation of the so-called system equation' implies the approach we take. With multiple classes of traffic, we define a set of service curves:one for each class. Constrained to the required profiles of individual service curves for delay satisfaction, the sets of weights are determined as a function of both the delay requirements and the traffic parameters. The schedulability test conditions, which are necessary to implement the call admission control, are also derived to ensure the proposed bandwidth allocation scheme' be able to support delay guarantees for all accepted classes of traffic. It is noticeable that the values of weights are tunable rather than fixed in accordance with the varying system status. This feature of adaptability is beneficial towards the enhanced efficiency of bandwidth sharing.

• Journal of KIISE:Information Networking
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• v.27 no.4
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• pp.507-521
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• 2000

실시간 멀티미디어 서비스에서 Quality of Service(QoS) 보장의 필요성이 증가하고 있다. 멀티미디어 서비스 제공 형태의 대다수가 될 멀티캐스트 경로설정에서도 QoS 보장은 확장성 신뢰성과 함께 매우 중요한 문제이다. QoS 기반 코어 선택 알고리즘을 제안한다. 제안 알고리즈믄 멀티캐스트 경로설정에서 코어 선택시에 다중 QoS 제약조건을 고려한다. QoS 제약조건은 최소보장 대역폭, 종단 지연, 종단 지연변이 등으로 정의한다. 모의 실험결과는 제안한 QCSA와 Maximum Centered Tree(MCT) Average Centered Tree (ACT) Initial Delay-Constrained Shared Tree(Dcinitial) Random Tree(Random)등의 기존 코어 선택 알고리즘의 성능을 각 항목별로 비교한다 멀티캐스트 그룹 멤버수와 QoS 제약조건을 인자로 한 모의 실험 결과는 제안한 QoS 기반 코어 선택 알고리즘이 기존 코어 선택 알고리즘에 비해서 다중 QoS 제약조건 보장 코어 선택 성공률에서 성능 개선 효과를 가짐을 보여준다. 제안 알고리즘이 본 논문에서 설정한 모의 실험 환경에서는 QoS 기반 코어 선택의 정도를 나타내는 성공률에서 약 10% 정도 기존 알고리즘보다 우수함을 보인다. 이 결과는 제안 알고리즘이 코어 선택 과정의 초기부터 멀티캐스트 그룹내의 모든 멤버에 대한 다중 QoS 제약조건을 고려하는 점이 QoS 기반 코어 선택에서 개선 효과를 나타냄을 보여준다.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.91-100
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• 2004

This paper presents a receiver-driven TCP flow control mechanism, which is adaptive to the wireless condition, for memory constrained mobile receiver. A receiver-driven TCP flow control is, in general, achieved by adjusting the size of advertised window at the receiver. The proposed method constantly measures at the receiver both the available wireless bandwidth and the packet round-trip time. Depending on the measured values, the receiver adjusts appropriately the size of advertised window. Constrained by the adjusted window which reflects the current state of the wireless network, the sender achieves an improved TCP throughput as well as the reduced round-trip packet delay. Its implementation only affects the protocol stack at the receiver and hence neither the sender nor the router are required to be modified. The mechanism has been implemented in real environments. The experimental results show that in CDMA2000 1x networks the TCP throughput of the proposed method has improved about 5 times over the conventional method when the receiver's buffer size is limited to 2896 bytes. Also, with 64Kbytes of buffer site, the packet round-trip time of the proposed method has been reduced in half, compared the case with the conventional method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.1-6
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• 2014

The IoT (Internet of Things) is considered as a core technology to realize interconnected world. At this, companies composing ICT industry and standard organizations make efforts to accelerate it. IETF CoRE(Constrained RESTful Environment) working group standardized CoAP (Constrained Application Protocol) for the constrained device. CoAP has RESTful architecture and CoAP option is provided to use forward-proxy. The forward-proxy is used to translate protocol and perform requests on behalf of the client. However, communication between Internet based client and LLN(Low-power and Lossy Network) based CoAP server architecture has limitations to deploy real IoT service. In this architecture, problems like response delay, URI assignment and DoS attack can be occurred. To solve these problems, we propose the reverse-proxy based system. We consider both of static IoT and mobility IoT environments. Finally, our proposed system is expected to provide efficient IoT service.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.4
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• pp.973-988
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• 2012

Delay tolerant networks (DTNs) characterized by the lack of guaranteed end-to-end paths exploit opportunistic data forwarding mechanism, which depends on the hypothesis that nodes are willing to store, carry, and forward the in-transit messages in an opportunistic way. However, this hypothesis might easily be violated by the presence of selfish nodes constrained with energy, bandwidth, and processing power. To address this problem, we propose a practical reputation-based incentive scheme, named PRI, to stimulate honest forwarding and discipline selfish behavior. A novel concept of successful forwarding credential and an observation protocol are presented to cope with the detection of nodes' behavior, and a reputation model is proposed to determine egoistic individuals. The simulation results demonstrate the effectiveness and practicality of our proposal.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.4
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• pp.1076-1089
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• 2012

Home automation networks are good environments for merging sensor networks and consumer electronics technologies. It is very important to reduce the energy consumption of each sensor node because sensor nodes operate with limited power based on a battery that cannot be easily replaced. One of the primary mechanisms for achieving low energy operation in energy-constrained wireless sensor networks is the duty-cycle operation, but this operation has several problems. For example, unnecessary energy consumption occurs during synchronization between transmission schedules and sleep schedules. In addition, a low duty-cycle usually causes more performance degradation, if the network becomes congested. Therefore, an appropriate control scheme is required to solve these problems. In this paper, we propose UDC (Unsynchronized Duty-cycle Control), which prevents energy waste caused by unnecessary preamble transmission and avoids congestion using duty-cycle adjustment. In addition, the scheme adjusts the starting point of the duty-cycle in order to reduce sleep delay. Our simulation results show that UDC improves the reliability and energy efficiency while reducing the end-to-end delay of the unsynchronized duty-cycled MAC (Media Access Control) protocol in sensor-based home automation networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3851-3866
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• 2015

The dynamic nature of opportunistic networks results in long delays, low rates of success for deliveries, etc. As such user experience is limited, and the further development of opportunistic networks is constrained. This paper proposes a prediction-based routing method for opportunistic networks (PB-OppNet). Firstly, using an ARIMA model, PB-OppNet describes the historical contact information between a node pair as a time series to predict the average encounter time interval of the node pair. Secondly, using an optimal stopping rule, PB-OppNet obtains a threshold for encounter time intervals as forwarding utility. Based on this threshold, a node can easily make decisions of stopping observing, or delivering messages when potential forwarding nodes enter its communication range. It can also report different encounter time intervals to the destination node. With the threshold, PB-OppNet can achieve a better compromise of forwarding utility and waiting delay, so that delivery delay is minimized. The simulation experiment result presented here shows that PB-OppNet is better than existing methods in prediction accuracy for links, delivery delays, delivery success rates, etc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.1
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• pp.241-269
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• 2012

Wireless networks composed of multimedia-enabled resource-constrained sensor nodes have enriched a large set of monitoring sensing applications. In such communication scenario, however, new challenges in data transmission and energy-efficiency have arisen due to the stringent requirements of those sensor networks. Generally, congested nodes may deplete the energy of the active congested paths toward the sink and incur in undesired communication delay and packet dropping, while bit errors during transmission may negatively impact the end-to-end quality of the received data. Many approaches have been proposed to face congestion and provide reliable communications in wireless sensor networks, usually employing some transport protocol that address one or both of these issues. Nevertheless, due to the unique characteristics of multimedia-based wireless sensor networks, notably minimum bandwidth demand, bounded delay and reduced energy consumption requirement, communication protocols from traditional scalar wireless sensor networks are not suitable for multimedia sensor networks. In the last decade, such requirements have fostered research in adapting existing protocols or proposing new protocols from scratch. We survey the state of the art of transport protocols for wireless multimedia sensor networks, addressing the recent developments and proposed strategies for congestion control and loss recovery. Future research directions are also discussed, outlining the remaining challenges and promising investigation areas.