• Journal of Korea Multimedia Society
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• v.15 no.6
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• pp.814-826
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• 2012

In this paper, we propose scheduling algorithms for transporting variable-bit-rate video stream using playback buffer level of the clients over wireless communication networks. The proposed algorithms attempt to maximize the utilization of limited bandwidth between the central video server and the clients over a mobile network. Since a video server may serve several video request at the same time, it is important to allocate and utilize network bandwidth to serve them fairly and efficiently. In order to improve the quality of service and real-time performance of individual video playback, the video server attempts to allocate temporarily more network bandwidth to serve a video request with the lower buffer level preferentially. The simulation results prove the fair service and load balancing among the mobile concurrent clients with different buffer levels and hence maximizing the number of frames that are transported successfully to the client prior to their playback times.

• The Transactions of the Korea Information Processing Society
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• v.6 no.2
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• pp.467-475
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• 1999

This paper presents an algorithm for scheduling jobs in soft real-time systems. To simplify the scheduling for soft real-time systems, we introduce two-level deadline scheme. Each job in the system has two deadlines, which we call first-level and second-level deadlines, respectively. The first-level deadline is the same as the deadline in traditional real-time systems. The second-level deadline is later than the first-level deadline, and defines the latest point in time when the result is still acceptable. Partial-credit is given for jobs meeting the second-level deadline but missing the first-level deadline, whereas jobs meeting the latter are given full credit. We heuristically compute priorities of jobs in a dynamic way by combining the first-level adn second-level deadlines with the partial-credit. Simulation results indicate that our two-level scheduling algorithm is a viable approach for dealing with both soft real-time systems and temporary overloaded hard real-time systems.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.1
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• pp.23-33
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• 2000

We propose a model which overlaps communication with computation for efficient communication in the data-parallel programming paradigm. The overlapping model divides a given loop partition into several sub-partitions to obtain computation which can be overlapped with communication. A loop partition sometimes refers to other data partitions, but not all iterations in the loop partition require non-local data. So, a loop partition may be divided into a set of loop iterations which require non-local data, and a set of loop iterations which do not. Each loop sub-partition is dynamically scheduled depending on associated message arrival, The experimental results for a few benchmarks in IBM SP2 show enhanced performance in our overlapping model.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.11
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• pp.11-19
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• 1994

Turnaround time of a job performing frequent disk I/O operations is greatly affected by I/O bottleneck which incurs due to the large gap in the speeds of I/O devices and the CPU. This paper proposes to employ a Write Dedicated Buffer(WDB) in disk arrays to improve the response time for read requests and analyzes the scheduling policies and the efficiency of the WDB. Through a series of simulations we show that, among the three policies examined, the partial stripe join(PSJ) policy is the most effective in terms of response time for both read and write requests and that, especially when using a WDB on declustered arrays, improvement of response time for read requests becomes greater as the request rate increases.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.529-534
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• 1998

본 논문에서는 초고속 통신망을 기반으로 하여 사용자의 온라인 개입이 가능한 실시간 멀티미디어 프리젠테이션 및 저작을 위한 도구를 설계 및 구현하였다. 실시간 네트워크 전송 동기화 기술은 멀티미디어 프리젠테이션 시스템의 핵심적인 부분으로서 지금까지 다수의 기법이 제안된 바 있으나 아직 초보적인 구현 단계에 있는 실정이다. 본 연구에서는 수신자 기반의 동적 동기화 기법과 스케쥴링 기법을 이용한 멀티미디어 프리젠테이션 및 저작 도구를 개발하였다. 또한, 미디어 동기화를 비롯하여 프리젠테이션시 고려해야 할 다양한 제어 요소들을 하나의 스레드가 통합된 제어 창구 역할을 하면서 시스템이 요구하는 작업을 분석하여 해당 작업 스레드 및 모듈로 이벤트 정보를 전송하여 처리하게 하는 방식으로 프리젠테이션 QoS를 향상시킬 수 있도록 하였다.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.3
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• pp.431-446
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• 1998

In this paper, we consider the problem of scheduling n jobs with sequence-dependent processing times on a set of parallel-identical machines. The processing time of each job consists of a pure processing time and a sequence-dependent setup time. The objective is to maximize the total remaining machine available time which can be used for other tasks. For the problem, we first propose a dynamic programming(DP) algorithm for sequencing jobs processed on a single machine. The algorithm is then extended to handle jobs on parallel-identical machines. Finally, we developed an improved version of the algorithm which generates optimal solutions using much smaller amount of memory space and computing time. Computational results are provided to illustrate the performance of the DP algorithms.

• Journal of the Korea Society for Simulation
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• v.19 no.3
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• pp.45-54
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• 2010

The inherent complexity of semiconductor fabrication processes makes it hard to solve well-known job scheduling problems in analytical ways, which leads us to rely practically on discrete event modeling simulations to learn the effects of changing the system's parameters. Meanwhile, unpredictable disturbances such as machine failures and maintenance diminish the productivity of semiconductor manufacturing processes with fixed scheduling policies; thus, it is necessary to adapt job scheduling policy in a timely manner in reaction to critical environmental changes (disturbances) in order for the fabrication process to perform optimally. This paper proposes an adaptive job control framework for a wafer fabrication process in a control system theoretical approach and implements it based on a DEVS modeling simulation environment. The proposed framework has the advantages in view of the whole systems understanding and flexibility of applying new rules compared to most ad-hoc software approaches in this field. Furthermore, it is flexible enough to incorporate new job scheduling rules into the existing rule set. Experimental results show that this control framework with adaptive rescheduling outperforms fixed job scheduling algorithms.

• Journal of Navigation and Port Research
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• v.36 no.5
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• pp.387-394
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• 2012

In an automated container terminal, automated stacking cranes(ASCs) take charge of handling of containers in a block of the stacking yard. This paper proposes a multi-criteria strategy to solve the problem of job dispatching of twin ASCs which are identical to each another in size and specification. To consider terminal situation from different angles, the proposed method evaluates candidate jobs through various factors and it dispatches the best score job to a crane by doing a weighted sum of the evaluated values. In this paper, we derive the criteria for job dispatching strategy, and we propose a genetic algorithm to optimize weights for aggregating evaluated results. Experimental results are shown that it is suitable for real time terminal with lower computational cost and the strategy using various criteria improves the efficiency of the container terminal.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.406-412
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• 2006

정보통신 기술의 발달로 근래에는 인터넷 방송 서비스가 활성화되었으며 누구든 자유롭게 방송을 제작하거나 청취할 수 있다. 이러한 인터넷 방송을 이용하기 위해서는 PC 를 이용하는 방법이 일반적이지만 오디오 서비스만을 이용할 경우 불편하다. 본 논문에서는 낮은 사양의 시스템에서 인터넷 방송을 청취하기 위한 하드웨어와 소프트웨어 설계 기법 그리고 효율적인 버퍼링 방법을 제안하였다. 제안된 시스템은 8 비트 마이크로 컨트롤러, 32KB 의 메모리, Hardwired TCP/IP Stack 그리고 Hardwired MP3 디코더를 이용하여 설계하였으며 각 작업간의 스케쥴링을 위하여 타이머 인터럽트를 이용하였다. 16KB의 메모리로 몇 가지 버퍼링 기법을 제안했다. 폴링 방식은 가장 보편적인 방법으로 데이터를 전송받는 작업과 음악을 재생하는 작업이 순차적으로 이루어진다. 이 방법은 데이터 전송과 음악 재생을 동시에 할 수 없기 때문에 타이머 인터럽트를 이용한 버퍼링 모델이 사용된다. 두 번째로 메모리를 두개의 블록으로 나누어 한 블록에는 데이터를 저장하고 다른 한 블록에는 데이터를 내보내는 '더블 버퍼링'을 제안했다. 세 번째는 메모리 블록을 여러 단계로 나눈'n-Queue 버퍼링' 기법을 제안했다. 마지막으로 네트워크 상황에 따라서 블록의 개수를 유동적으로 조절하는 '가변 길이 n-Queue 버퍼링' 기법을 제안했다. 이 방법은 네트워크 상황에 따라 메모리의 크기를 유동적으로 할당하기 때문에 메모리 사용률이 높아지는 장점이 있다. 본 논문에서 제안하는 시스템은 운영체제를 사용하지 않았기 때문에 TV 나 오디오 등 다른 시스템에 이식이 용이하므로 다양한 기기에 적용이 가능하다.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.7
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• pp.354-360
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• 2008

Power-related issues have become important considerations in current generation microprocessor design. One of these issues is that of elevated on-chip temperatures. This has an adverse effect on cooling cost and, if not addressed suitably, on chip reliability. In this paper we investigate the general trade-offs between temporal and spatial hot spot mitigation schemes and thermal time constants, workload variations and microprocessor power distributions. By leveraging spatial and temporal heat slacks, our schemes enable lowering of on-chip unit temperatures by changing the workload in a timely manner with Operating System (OS) and existing hardware support.