• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.761-763
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• 2003

이동 컴퓨팅 환경은 협소한 대역폭. 전력공급의 한계성, 그리고 무선통신망의 낮은 신뢰성 등의 제약사항을 갖고 있다. 이동 컴퓨팅 시스템은 제한된 대역폭의 효율적인 사용과 거래의 수행성능을 향상시키기 위한 비용 효과적인 거래 스케줄링 알고리즘의 개발이 필요하다. 이 논문에서는 캐슁과 방송기법을 사용하는 이동 컴퓨팅 환경에서 이동 클라이언트의 갱신 연산이 가능한 경우에 캐쉬 데이터의 현재성과 상호 일관성을 만족할 수 있는 거래 스케줄링 알고리즘을 제안한다. 제안한 기법은 이동 클라이언트에서 사용하는 캐쉬에 있는 데이터에 대한 유효성을 각 데이터의 동적인 갱신 비율을 기준으로 하여 결정한다. 동적 갱신 비율의 도입은 거래의 철회율을 낮추어 제한된 대역폭의 사용과 서버의 부하를 줄여 시스템의 성능을 향상시킨다.

• Annual Conference of KIPS
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• 2012.11a
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• pp.160-163
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• 2012

맵리듀스는 데이터 집약적인 어플리케이션에서 대량의 데이터를 분산 병렬 처리하기 위한 프로그래밍 모델이다. 하둡은 맵리듀스의 오픈소스 구현으로 맵리듀스를 사용하기 위한 도구로 많이 알려져 있다. 실제 하둡을 이용하여 맵리듀스를 적용할 때 맵 태스크 단계는 병렬로 수행되어 순차처리에 비해 시간이 단축된다. 그러나 맵 태스크의 결과물인 중간 단계의 데이터는 단일 리듀스 태스크에서 처리됨으로써 시간 지연이 발생한다. 따라서 본 논문에서는 단일 리듀스 태스크 처리에서 발생하는 오버로드 및 시간 지연 문제를 해결하기 위해 적응적으로 리듀스 태스크를 할당하는 스케줄링 기법을 제안하고 실험을 통해 이 기법의 성능을 검증한다.

• Annual Conference of KIPS
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• 2011.04a
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• pp.211-212
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• 2011

스트림 프로세싱 시스템은 실시간 데이터 수집 장치와 대규모 분산 컴퓨팅 환경이 결합되어 데이터 생성과 가공을 통하여 다수의 결과를 병렬적으로 도출하는 분산 프로그래밍 모델이다. 본 논문에서는 프로세스간에 필수적으로 요구되는 유입데이터 버퍼 관리에 초점을 두고 있다. 데이터의 유입률에 따라 동적으로 분석 프로세스를 확장시킴으로서 프로세스간 버퍼의 크기를 제어하는 기법을 제안하며 시뮬레이션을 통하여 성능 분석을 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.44-53
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• 2010

This paper proposes a traffic management policy for delay control in the wireless networks. The so-called EDD(Earliest Due Date) scheme is adopted as the packet scheduling policy, so that the service provision is performed in the order of the transmission urgency of the backlogged packets. In addition, we derive a formula to determine the contention window, one of the MAC parameters, with the goal of minimizing the non-work conserving characteristics of the traditional MAC scheme. This method eliminates the burden of the class-wise parameter settings which is typically required for the priority control. Simulations are performed to show the validity of the proposed scheme in comparison with the policy that adopts the class-level queue management such as the IEEE 802.11e standard. Smaller delays and higher rates of delay guarantees are observed throughout the experiments.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.45-56
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• 2011

WBAN is short range wireless communication technology which is consists of several small devices close to, attached to or implanted into the human body. WBAN is classified into between medical and non-medical by applications based on technology and medical data with periodic characteristics is used the GTS method for transmitting data to guarantee the QoS. In this paper we proposed algorithm that resolve lack of GTSs while data transmit GTS method in superframe structure of WBAN. Coordinator dynamically allocates GTSs according to the data rate of devices and make devices share GTSs when lack of GTSs. We compared delay bounds, throughput for performance evaluation of the proposed algorithm. In other words, we proposed algorithm adaptive WFQ scheduling that GTS allocation support differential data rate in environments of WBAN. The experiment results show the throughput increased and the maximum delay decreased compared with Round Robin scheduling.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.538-541
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• 2006

Recently researches of P2P media streaming have been actively published, but the research what kind of P2P overlay networks are better to delivering media data has not been attended. This paper designs a P2P streaming media system model. In this system, we constructs a Half-Structure P2P overlay protocol based on node's capability as the infrastructure of streaming application, which utilizes the heterogeneity of the nodes to maintain topology, presents a active contents diffusing algorithm and Two-stage search algorithm, make it possible for nodes in P2P system to collect information according their capacity and reduces the number of forwarding packet compared with flooding. Also, we give an optimal scheme to scheduling media data.

• Journal of Internet Computing and Services
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• v.24 no.1
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• pp.87-97
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• 2023

Charger infrastructure facilities are designed and installed based on a constant power supply. Initially designed charging facilities support charging of rapidly growing electric vehicles on a limited power supply basis. In addition, current commercial vehicles can only be fully charged, and are supported by the rapid equalization charging method. However, commercial vehicles operate according to a set schedule, so flexible charging is essential. In this paper, we propose a power operation method with more than 20% efficiency improvement by using a fixed schedule-based charging scheduling and power distribution technique of a commercial bus based on the same amount of power in accordance with the rapid growth and increase of electric vehicles.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.31-40
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• 2004

In this paper, we analyze mathematically the performance of the gated service scheduling in the Interleaved Polling with Adaptive Cycle Time(IPACT) was proposed to control upstream traffic for Gigabit Ethernet-PONs. In the analysis, we model EPON MAC protocol as a polling system and use mean value analysis. We divide arrival rate λ into three regions and analyze each region accordingly In the first region in which λ value is very small, there are very few ONUs' data to be transmitted. In the second region in which λ has reasonably large value, ONUs have enough data for continuous transmission. In the third region, ONUs' buffers are always saturated with data since λ value is very large. We obtain average packet delay, average Queue size, average cycle time of the gated service. We compare analysis results with simulation to verify the accuracy of the mathematical analysis. Simulation requires much time and effort to evaluate the performance of EPONs. On the other hand, mathematical analysis can be widely used in the design of EPON systems because system designers can obtain various performance results rapidly. We can design appropriate EPON systems for varioustraffic property by adjusting control parameters.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.1-7
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• 2010

Network Centric Warfare(NCW) is becoming a prominent concept in the current trend of warfare. To support high quality communication between strategic/tactical units in the concept of NCW, Tactical Airborne Networks are likely to be constructed in the near future to take part in the NCW. In these Tactical Airborne Networks with dynamic topology variations due to very high mobility of participants nodes, more efficient and reliable neighbor discovery protocols are needed. This paper presents the adaptive HELLO message scheduling algorithm for Tactical Airborne Network using directional antennas. The purposed algorithm can reduce the overhead of periodic HELLO message transfer, while guaranteeing successful data transmission. We concluded a mathematical analysis and simulation studies using Qualnet 4.5 for evaluation the performance and efficiency of the proposed scheme.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.140-148
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• 2011

Multimedia streaming service is susceptible to loss and delay of data as it requires high bandwidth and real time processing. Therefore QoS cannot be guaranteed due to data loss caused by heavy network traffic. To deal with these problems, a study on algorithm that can provide high quality multimedia service by considering both network congestion and characteristics of multimedia data is required. In this paper, we propose APQM algorithm which probabilistically removes packet by the congestion level of the queue in wireless station. The comparison with other existing scheduling algorithms shows tht congestion in the network is reduced and multimedia service quality of the proposed algorithm is improved.