• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1330-1335
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• 2012

This paper proposes an automatic measurement sampling method for the semiconductor manufacturing process. The method recommends sampling rates using information of process capability indexes and production scheduling plan within the restricted metrology capacity. In addition, it automatically controls the measurement WIP (Work In Process) using measurement priority values to minimize the measurement risks and optimize the measurement capacity. The proposed sampling method minimizes measurement controls in the semiconductor manufacturing process and improves the fabrication productivity via reducing measurement TAT (Turn Around Time), while guaranteeing the level of process quality.

• Journal of Technology Innovation
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• v.12 no.3
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• pp.111-134
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• 2004

Current technology innovation or new product development project is composed of various process elements that conduct researches on fundamental technologies. However, with the effects of PERT and CPM, the greater part of the existing project management researches have only focused on the resource allocation and scheduling. But in the multi-project environment, priorities between technology elements need to be considered. Furthermore, a disagreement of opinion between project managers and researchers should be considered. In this study, technology element priority was determined using modified QFD and Taguchi method. Outcome of each method was compared to analyze the difference between project managers and researchers. As a result, QFD method showed relatively high level of consistency between project managers and researchers.

• Journal of KIISE:Information Networking
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• v.27 no.3
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• pp.315-322
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• 2000

네트워크에서 QoS를 보장하기 위해 최근에 제안되는 패킷 스케줄링 알고리즘은 대부분 우선 순위에 입각한 패킷 전송 서비스를 한다. 이러한 우선 순위를 유지하기 위한 큐의 관리에는 많은 비용이 들므로 QoS를 보장하는 네트워크에서 우선 순위 큐의 관리 비용을 줄이는 노력이 필요하다. 패킷 스케줄링 알고리즘 중 RPO+(Rotate Priority Queue)는 우선 순위 FIFO(First in first out)큐를 사용하여 주기 적으로 재명명되는 패킷 스케줄링 알고리즘이다. FIFO 큐에 패킷들을 근사 정렬하여 패킷의 우선 순위를 유지하므로 계산 복잡도를 줄이지만, 패킷 우선 순위를 유지하기 위해 2배(2P)의 큐를 필요로 한다.[1] 본 논문에서는 필요한 큐의 개수를 P개의 큐로 제한하여 큐에 대한 관리 비용을 줄였으며 엔터프라이즈 환경에서 애플리케이션이 요구하는 서비스 특성에 따라 클래스로 구분하여 적합한 패킷 스케줄링 서비스를 제공하는 알고리즘을 제시한다. 본 기법은 추가적인 오버플로우 큐를 관리하고 패킷 어드미션 컨트롤러를 통해 패킷 전송 지연 시간을 제한함으로 다양한 애플리케이션의 네트워크 QoS 요구를 보장하고 패킷 전손 효율을 높였다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.4
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• pp.18-26
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• 2006

여러 형태의 고객이 외부로부터 포아송과정에 따라 각 대기행렬에 도착하고 정해진 서비스규칙에 따라 해당 서비스를 받은 후 마코비안 확률분포에 따라 시스템을 떠나거나 다른 형태의 고객으로 시스템을 다시 돌아 올 수도 있는 M/G/1 대기행렬시스템을 고려한다. 본 연구에서는 기존의 연구 모형을 확장하여 계층적 서비스 규칙을 갖는 우선순위 대기행렬모형을 제시하고 이에 대한 시스템 성능척도를 보다 체계적으로 구할 수 있는 방법을 소개한다. 이를 위하여 먼저 대기행렬시스템의 거동을 나타내는 시스템 상태를 정의하고, 바쁜기간과 서비스기간 분석을 통하여 시스템 상태의 선형 함수로 평균체제시간을 구할 수 있음을 보인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.489-492
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• 2011

SIP (Session Initiation Protocol)는 사용자간의 멀티미디어 세션의 초기화, 변경 및 종료를 위한 응용 계층의 시그널링 프로토콜이다. SIP는 실시간 멀티미디어 서비스 통신에 많이 이용되기 때문에 주로 Unreliable Transport Protocol을 사용한다. 따라서 손실된 SIP 메시지들의 신뢰성을 보장하기 위하여 재전송 메커니즘을 제공한다. 하지만 이러한 재전송 메커니즘은 SIP 프록시 서버가 과부하 상황일 경우 신뢰성보다는 오버헤드가 증가되는 문제점을 가진다. 기존의 여러 SIP 과부하 제어 방법이 제안되었지만 네트워크 혼잡이 증가함에 따라 프록시 서버의 처리율이나 호 설정 시간의 지연 문제를 효율적으로 해결하지 못한다. 본 논문에서는 SIP 시그널링 네트워크에서 프록시 서버가 과부하 상황일 경우 낮은 호 설정 지연시간과 높은 처리율을 위해 우선순위 스케줄링 기반의 과부하 제어 알고리즘을 제안한다. 그리고 기존 과부하 제어에서 사용하는 알고리즘과 제안하는 알고리즘을 비교하여 보았다. 성능 평가 결과 부하에 따른 프록시 서버의 처리율과 호 설정 시간의 지연 측면에서 기존의 과부하 제어 알고리즘보다 향상됨을 보였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.143-150
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• 2013

Solid-state disks (SSDs) have been widely used by high-performance personal computers or servers due to its good characteristics and performance. The NAND flash-based SSDs, which take large portion of the whole NAND flash market, are the major type of SSDs. They usually integrate a cache buffer which is built from DRAM and uses the write-back policy for better performance. Unfortunately, the policy makes existing scheduling methods less effective at the I/F level of SSDs Therefore, in this paper, we propose a scheduling method for the I/F with consideration of the cache buffer. The proposed method considers the hit/miss status of cache buffer and gives higher priority to the read requests. As a result, the requests whose data is hit on the cache buffer can be handled in advance and the read requests which have larger effects on the whole system performance than write requests experience shorter latency. The experimental results show that the proposed scheduling method improves read latency by 26%.

• Journal of KIISE:Databases
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• v.29 no.1
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• pp.44-57
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• 2002

Multiple spatial queries are defined as two or more spatial range queries to be executed at the same time. The primary processing of internet-based map services is to simultaneously execute multiple spatial queries. To improve the throughput of multiple queries, the time of disk I/O in processing spatial queries significantly should be reduced. The declustering scheme of a spatial dataset of the MIMD architecture cannot decrease the disk I/O time because of random seeks for processing multiple queries. This thesis presents query scheduling strategies to ease the problem of inter-query random seeks. Query scheduling is achieved by dynamically re-ordering the priority of the queued spatial queries. The re-ordering of multiple queries is based on the inter-query spatial relationship and the latency of query processing. The performance test shows that the time of multiple query processing with query scheduling can be significantly reduced by easing inter-query random seeks as a consequence of enhanced hit ratio of disk cache.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.20-29
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• 2014

Recently, LTE is preparing to make a new leap forward LTE-A all over the world. As LTE privides high speed service, the role of mobile phones seems to change from voice to data service. According to Cisco, global mobile data traffic will increase nearly 11-fold between 2013 and 2018. Mobile video traffic will reach 75% by 2018 from 66% in 2013 in Korea. However, voice service is still the most important role of mobile phones. Thus, controllability of throughput and low BLER is indispensable for high-quality VoIP service among various type of traffic. Although the maximum AMR-WB, 23.85 Kbps is sufficient to a VoIP call, it is difficult for the LTE which can provide tens to hundreds of MB/s may not keep the certain level VoIP QoS especially in the cell-edge area. This paper proposes a new scheduling algorithm in order to improve VoIP performance after analyzing various scheduling algorithms. The proposal is the technology which applies more priority processing for VoIP than other applications in cell-edge area based on two-tier scheduling algorithm. The simulation result shows the improvement of VoIP performance in the view point of throughput and BLER.

• Journal of Internet of Things and Convergence
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• v.10 no.3
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• pp.19-24
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• 2024

Recent advances in large-scale data processing technologies such as big data, cloud computing, and artificial intelligence have increased the demand for high-performance storage devices in data centers and enterprise environments. In particular, the fast data response speed of storage devices is a key factor that determines the overall system performance. Solid state drives (SSDs) based on the Non-Volatile Memory Express (NVMe) interface are gaining traction, but new bottlenecks are emerging in the process of handling large data input and output requests from multiple hosts simultaneously. SSDs typically process host requests by sequentially stacking them in an internal queue. When long transfer length requests are processed first, shorter requests wait longer, increasing the average response time. To solve this problem, data transfer timeout and data partitioning methods have been proposed, but they do not provide a fundamental solution. In this paper, we propose a dual queue based scheduling scheme (DQBS), which manages the data transfer order based on the request order in one queue and the transfer length in the other queue. Then, the request time and transmission length are comprehensively considered to determine the efficient data transmission order. This enables the balanced processing of long and short requests, thus reducing the overall average response time. The simulation results show that the proposed method outperforms the existing sequential processing method. This study presents a scheduling technique that maximizes data transfer efficiency in a high-performance SSD environment, which is expected to contribute to the development of next-generation high-performance storage systems

• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.437-442
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• 2009

For multiprocessor systems, Earliest Deadline First (EDF) based on deadline and Least Laxity First (LLF) based on laxity are not suitable for practical environment since EDF has low schedulability and LLF has high context switching overhead. As a combining of EDF and LLF to improve the performance, Earliest Deadline Zero Laxity (EDZL) was proposed. EDZL is basically the same as EDF. But if the laxity of a task becomes zero, its priority is promoted to the highest level. In this paper, we propose Least Laxity Zero Laxity (LLZL) which is based on LLF. But context switching is allowed only if the laxity of a task on rady queue becomes zero. Simulation results show that LLZL has high schedulability approaching to LLF and low context switching overhead similar to EDF. In comparison with EDZL, LLZL has better performance in both of schedulability and context switching overhead.