• Proceedings of the Korea Information Processing Society Conference
• /
• 2010.04a
• /
• pp.75-77
• /
• 2010

실시간 환경에서 저전력 설계의 효율적인 방법으로 동적 전압 조절 기법(Dynamic Voltage Scaling)이 있다. 동적 전압 조절 기법의 성능을 올리기 위하여 정확한 작업 시간의 예측이 필수적이며, 많은 예측 필터들이 이를 위하여 사용되었다. 하지만 각 예측 필터들은 여러 가지 다른 상황에 대하여 모두 적절하게 처리하는데 한계를 가지고 있다. 이 논문에서는 여러 가지 다른 예측필터들의 상황 별 성능을 분석하고 이를 바탕으로 동적으로 상황에 따라 예측 필터를 변화시키며 항상 최적의 성능을 가지는 새로운 예측 방법을 제안하였다. 또한 MPEG 환경에서의 시뮬레이션을 통하여 제안한 방법이 모든 상황에서 다른 예측 필터들에 비하여 높은 성능을 보이는 것을 확인할 수 있었다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.29 no.11
• /
• pp.601-610
• /
• 2002

Intra-task voltage scheduling (IntraVS), which adjusts the supply voltage within an individual task boundary, is an effective technique for developing low-power applications. In this paper, we propose a novel intra-task voltage scheduling algorithm for hard real-time applications based on average-case execution time. Unlike the conventional IntraVS algorithm where voltage scaling decisions are based on the worst-case execution cycles, tile proposed algorithm improves the energy efficiency by controlling the execution speed based on average-case execution cycles while meeting the real-time constraints. The experimental results using an MPEG-4 decoder program show that the proposed algorithm reduces the energy consumption by up to 34% over conventional IntraVS algorithm.

• Journal of KIISE:Computer Systems and Theory
• /
• v.30 no.12
• /
• pp.736-748
• /
• 2003

Dynamic voltage scaling(DVS), which adjusts the clock speed and supply voltage dynamically, is an effective technique in reducing the energy consumption of embedded real-time systems. The energy efficiency of a DVS algorithm largely depends on the performance of the slack estimation method used in it. In this paper, we propose novel DVS algorithms for periodic hard real-time tasks based on an improved slack estimation algorithm. Unlike the existing techniques, the proposed method can be applied to most priority-driven scheduling policies. Especially, we apply the proposed slack estimation method to EDF and RM scheduling policies. The experimental results show that the DVS algorithms using the proposed slack estimation method reduce the energy consumption by 20∼40 % over the existing DVS algorithms.

• Journal of KIISE:Computer Systems and Theory
• /
• v.35 no.11
• /
• pp.517-526
• /
• 2008

As the functionality of portable devices arc being enhanced and the performance is being greatly improved, power dissipations of battery driven portable devices are being increased. So, an efficient power management for reducing their power consumption is needed. In this paper, we propose a window-based DVS algorithm for MPEG Player. The proposed algorithm maintains the recently frame information and execution time received from MPEG player in window queue and dynamically adjusts (frequency, voltage) level based on window queue information. Our algorithm can be implemented in the common multimedia player as a module. We employed well-known MPlayer for the measurement of performance. The experimental result shows that the proposed algorithm reduces energy consumption by 56% on maximal performance.

• Journal of Korea Multimedia Society
• /
• v.13 no.1
• /
• pp.30-37
• /
• 2010

Many embedded real - lime systems have adopted processors supported with dynamic voltage scal-ing(DVS) recently. Power is one of the important metrics for Optimization in the design and operation of embedded real-time systems. We can save considerable energy by using slowdown of processor sup-ported with DVS. In this paper, we improved the previous algorithm at a point of view of time complexity to calculate task slowdown factors for an efficient energy consumption in embedded real-time systems with task synchronization. We grasped the properties of the previous algorithm having $O(n^{2})$ time complexity through mathematical analysis and s simulation. Using its properties we proposed the improved algorithms with O(nlogn) and O(n) time complexity which have the same performance as the previous algorithm has.

• Proceedings of the Korean Information Science Society Conference
• /
• 2008.06b
• /
• pp.509-514
• /
• 2008

동적 전력 관리 기법은 임베디드 시스템과 같은 저전력성이 요구되는 시스템에서 널리 활용되고 있다. 동적 전력 관리 기법은 처리율과 소비전력 간의 상관 관계를 통해, 프로세서의 전압과 주기를 조절하여 소비 전력당 처리율을 높이는 기법이다. 이러한 동적 전압 관리 기법이 실시간 특성이 필요한 임베디드 시스템에 적용되는 경우, 실시간 스케줄러에 큰 영향을 끼치게 된다. 실시간 스케줄러에서는 주어진 임계 시간 이내에 작업의 수행을 마치기 위하여, 스케줄 가능성 테스트를 수행하여 적합한 작업들만을 실행하도록 한다. 하지만, 인터럽트 처리 등으로 인한 선점 가능성은 스케줄 가능성에 대한 분석을 복잡하게 만들고 있다. 본 논문에서는 인터럽트 처리를 고려한 실시간 스케줄링 분석 연구를 기반으로 하여, 동적 전력 관리가 추가된 경우의 영향을 분석하도록 한다. 동적 전력 관리로 인한 실시간 처리 요구 사항의 증가와 실제 적용 가능한 사례를 보인다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.35 no.6
• /
• pp.273-283
• /
• 2008

Many embedded real-time systems have adopted processors supported with dynamic voltage scaling(DVS) recently. Power is one of the important metrics for optimization in the design and operation of embedded real-time systems. We can save considerable energy by using slowdown of processor supported with DVS. In this paper, we propose heuristic algorithms to calculate task slowdown factors for an efficient energy consumption in embedded real-time systems with task synchronization. The previous algorithm has a following constraint : given the tasks are ordered in a nondecreasing order of their relative deadline, the task slowdown factors computed are in a nonincreasing order. In this paper, we relax the constraint and propose heuristic algorithms which have the same time complexity that previous algorithm has and can save more energy. Experimental results show that the proposed algorithms are energy efficient.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.12
• /
• pp.96-104
• /
• 2009

In the real system environments, the performance of the application is not linearly proportional to the clock frequency of the microprocessor, in contrast to the general assumption of conventional dynamic voltage scaling. In this paper, we analytically model the relation between the performance of the application and the clock frequency of the microprocessor, and introduce the energy-optimal scheduling algorithm for a task set with distinct application characteristics. In addition, we present a theorem for the energy-optimal scheduling, which the derivative of the energy consumption with respect to the execution time should be the same for all the tasks. The proposed scheduling algorithm always generates the energy-optimal scaling factor thanks to the theorem for energy-optimal scheduling. We achieved about 7% additional energy reduction in the experiments using synthetic task sets.

• Communications of the Korean Institute of Information Scientists and Engineers
• /
• v.24 no.8 s.207
• /
• pp.61-69
• /
• 2006

• Proceedings of the Korea Multimedia Society Conference
• /
• 2001.11a
• /
• pp.35-40
• /
• 2001

동적 전압 조정(DVS)은 모바일 환경에서 프로세서에서의 전력 소모를 줄일 수 있는 가장 효율적인 방법으로 많은 연구가 진행중이다 또한 MPEG 디코딩은 모바일 기기에서 가장 중요하고 또한 전력 소모가 큰 어플리케이션 중 하나이다. 본 논문에서는 모바일 환경에 적합한 MPEG 디코더를 DVS를 이용하여 구현하였고 전력 소모를 측정하였다. 제안된 첫번째 DVS 알고리즘은 이전의 workload에 의해 다음 workload를 예측하여 전압을 조정하는 것이고, 두번째 알고리즘은 MPEG 프레임의 종류 및 크기를 이용하여 다음 프레임의 디코딩 시간을 예측 한 후 전압을 조절하는 것이다. 실험을 통하여 두번째 알고리즘에 의한 MPEG 디코더가 더 정확한 workload 예측을 통하여 QoS의 저하를 최소화하면서 전력 소모를 더 많이 줄일 수 있었다.