• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1753-1756
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• 2010

최근 들어 가상화 기술은 서버의 통합에 뿐만 아니라, 임베디드 시스템에서도 널리 사용되고 있다. 하지만, 가상화 시스템에서는 물리 프로세서가 게스트 운영체제에게 직접 전달되지 않으며, 게스트 운영체제는 가상 프로세서를 통해서 실행할 수 밖에 없다. 따라서, 기존의 처리량 기준의 공평성 스케줄러가 가상머신 모니터에서 동작하는 경우, 실시간 스케줄링이 불가능하다. 본 연구에서는 멀티코어 기반의 가상화 시스템에서 실시간 태스크의 실행을 보장하는 기법을 소개한다. 특히, 본 논문에서는 계층형 스케줄링의 특성과 최대 병렬성 조건을 통하여 멀티코어 가상머신의 스케줄 가능성 분석 기법을 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1106-1112
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• 2007

As a demand for high speed uplink packet services increases, the WCDMA enhanced uplink, also known as high speed uplink packet access (HSUPA), has been specified in release 6 by 3GPP. This HSUPA will provide various types of multimedia services, such as real-time video streaming, gaming, VoIP, and FTP. Generally, the performance of HSUPA is dominated by scheduling policy. Therefore, it is required to design a scheduling algorithm considering the traffic characteristics to provide QoS guaranteed services in various traffic environments. In this paper, we propose a scheduling algorithm considering the traffic characteristics to guarantee QoS in a mixed traffic environment. Finally, the performance of the proposed scheduling algorithm is evaluated in terms of average packet delay, packet delay jitter, and system throughput using a system level simulator.

• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.94-102
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• 2010

In recent years, embedded systems such as cellular phones, Portable Multimedia Player, intelligent appliance, automobile engine control are reshaping the way people live, work, and play. Thereby, services application to guarantee various requirements of users become increasingly sophisticated and complicated, such embedded computing platforms use real-time operating systems (RTOSs) with time determinism. These RTOSs must not only provide predictable services but must also be efficient and small in size. Kernel services should also be deterministic by specifying how long each service call will take to execute. Having this information allows the application designers to better plan their real-time application software so as not to miss the deadline of each task. In this paper, we present the complete generalized real-time scheduling algorithm using multi-dimensional methodology to determine the highest priority in the ready list with 2r levels of priorities in a constant time without additional memory overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4A
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• pp.393-401
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• 2006

Energy consumption is an important design parameter for battery-operated embedded systems. Dynamic power management is one of the most well-known low-power design techniques. This paper proposes an online realtime scheduling algorithm, which we call energy-aware realtime scheduling using slack stealing (EARSS). The proposed algorithm gives the highest priority to the task with the largest degree of device overlap when the slack time exists. Scheduling result enables an efficient power management by reducing the number of state transitions. Experimental results show that the proposed algorithm can save the energy by 23% on average compared to the DPM-enabled system scheduled by the EDF algorithm.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.533-542
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• 2001

In this paper, we present a scheduling method for real-time mobile transaction manager in mobile computing environment. The proposed method checks whether a transaction is executable or not. It is able to by considering not only the deadline of real-time data in mobile hosts. And then, it schedules the real-time mobile transactions by making optimal execution window based on the priority queue, while considering transaction value and deadline. Disconnection with mobile hosts is monitored in selecting the transaction for execution. Using the proposed method reduces the number of restarting times after transaction aborts which is caused by the violation of the validity constraints of real-time data. And in has merits of maximizing the sum of values of real-time mobile transactions which meet the deadline. The performance evaluation demonstrates that the number of committed real-time transactions within the deadline is improved by 20%. This method can be used in real-time mobile transaction manager is such environments as cellular communications, emergency medicine information system and so on.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.571-573
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• 2004

지금까지 시스템의 자원을 효율적으로 활용하고, 응용 프로그램의 실시간 응답을 보장하는 등의 사용자의 요구를 만족시키기 위해 다양한 다중 프로세스 스케줄링 기법들이 연구되어 왔다. 대부분의 스케줄링 기법들은 프로세서, 즉 CPU 자원을 어떻게 할당할 것인가에 초점을 맞추고 있다. 그러나 오늘날 급격한 발전을 이루고 있는 무선 모바일 네트워크 시스템에서는 전력 자원이 네트워크의 지속시간을 결정짓는 중요한 지표가 되기 때문에 프로세스 스케줄링 기법에 있어서도 전력 자원을 고려할 필요가 있다. 따라서 본 논문에서는 충.방전을 고려하여 전력 자원을 효율적으로 사용하기 위한 스케줄링 기법에 대해 연구하였다. 각 프로세스의 실행시간과 실행 시 소비되는 전력량을 기준으로 한 6가지의 스케줄링 기법을 제안하고 이를 비교 분석하여, 그 중 단위 실행시간 당 소비되는 전력량이 작은 순서로 프로세스를 실행시키는 스케줄링 기법이 가장 효율적임을 확인하였다.

• 전기의세계
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• v.46 no.5
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• pp.19-27
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• 1997

본 논문은 제 2장에서 실시간 시스템의 기본 특성에 대해 보다 자세하게 살펴본 후, 제 3장에서 플랜트의 동적 특성을 관련 제어이론을 활용하여 실시간 시스템의 가장 중요한 정보인 작업 데드라인을 유도하는 방법을 살펴본다. 제 4장에서는 효율적인 실시간 제어 컴퓨터를 설계 및 평가하기 위해 실시간 시스템 분야에서 수행되는 연구동향으로 다음과 같은 세부 분야를, i) 스케줄링, ii)실시간 컴퓨터 언어, iii)실시간 운영체계(O/S), iv)실시간 동기화, v) 실시간 H/W 구조(architecture), vi) 실시간 통신, vii) 고장허용기법(fault-tolerance)에 대해 설명하고, 마지막 장에서 향후의 관련 연구 과제들에 대해 간단한 소개로 결론짓는다.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.73-82
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• 2007

In recent years, embedded systems have been expanding their application domains from traditional applications (such as defense, robots, and artificial satellites) to portable devices which execute more complicated applications such as cellular phones, digital camcoders, PMPs, and MP3 players. So as to manage restricted hardware resources efficiently and to guarantee both temporal and logical correctness, every embedded system use a real-time operating system (RTOS). Only when the RTOS makes kernel services deterministic in time by specifying how long each service call will take to execute, application programers can write predictable applications. Moreover, so as for an RTOS to be deterministic, its scheduling and context switch overhead should also be predictable. In this paper, we present the complete generalized algorithm to determine the highest priority in the ready list with 22r levels of priorities in a constant time without additional memory overhead.

• Journal of Internet Computing and Services
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• v.8 no.1
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• pp.71-78
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• 2007

In this paper, an effective task scheduling scheme was proposed for the flexible real time LINUX systems with the selection between EDF(earliest deadline first) and RMS(rate monotonic scheduling). It was known that many task scheduling schemes were analyzed according to the characteristics of scheduling schemes and the guarantee of an earliest deadline scheduler for process utilities.

• The Journal of the Korea Contents Association
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• v.6 no.2
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• pp.9-16
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• 2006

This paper proposes a scheduling algorithm for efficiently processing multimedia pakcet services in OFDMA physical system of the future broadband wireless access networks. The scheduling algorithm uses wireless channel state estimation, and allocates transmission rates after deciding transmission ordering based on class and priority policy. As the result, the proposed scheduling algorithm offers maximum throughput and minimum jitter for realtime services, and fairness for non-realtime services. In simulation study, the proposed algorithm proves superior performances than traditional round robin method.