• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.9
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• pp.49-57
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• 2009

In this paper, we propose a multiple voltage scheduling method which reduces energy consumption considering both timing constraints and resource constraints. In the other multiple voltage scheduling techniques, high voltage is assigned to operations in the longest path and low voltage is assigned to operations that are not on the longest path. However, in those methods, voltages are assigned to specific operations restrictively. We use a simulated annealing technique, in which several voltages are assigned to specific operations flexibly regardless of whether they are on the longest path. In this paper, a post processing algorithm is proposed to further reduce the energy consumption. In some cases, designers may want to reduce the level shifters. To make tradeoff between the total energy and the number (or energy) of level shifters weighted term can be added to the cost function. When the level shifter energy is weighted six times, for example, the number of level shifters is reduced by about 24% and their energy consumption is reduced by about 20%.

• The Journal of the Acoustical Society of Korea
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• v.33 no.5
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• pp.341-350
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• 2014

In this paper, an energy efficient clustering scheme using self organization method is proposed. The proposed scheme selects a cluster head considering not only the number of neighbor nodes but also the residual battery amount. In addition, the network life time is extended by re-selecting the cluster heads only in case the current cluster head's residual energy falls down below a certain threshold level. Accordingly, the energy consumption is evenly distributed over the entire network nodes. The cluster head delivers the collected data from member nodes to a Sink node in a way of multi-hop relaying. In order to evaluate the proposed scheme, we run computer simulation in terms of the total residual amount of battery, the number of alive nodes after a certain amount of time, the accumulated energy cost for network configuration, and the deviation of energy consumption of all nodes, comparing with LEACH which is one of the most popular network clustering schemes. Numerical results show that the proposed scheme has twice network life-time of LEACH scheme and has much more evenly distributed energy consumption over the entire network.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.3
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• pp.62-74
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• 2020

Although the government and local governments devote efforts to activate bicycles, they only access to the supply infrastructure such as bike lanes and the public bicycle rental service centers without considering the measures to overcome the geographical constraints of slope. Therefore, this study constructs bicyclist's energy consumption estimation model through experimental methods of slope gradient and heart rate measurement and suggest the bicycle route choice model which could minimize the energy by the slope gradient. After calculating the RMSE of the estimated energy consumption by applying this model to the simulation section, it is confirmed to be 41% better than the model which does not reflect slope gradient. The results of this study are expected to be applied to the bicycle infrastructure planning that considers both longitude and transverse of bike lanes and the algorithm of bicycle route guidance system in the future.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.7
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• pp.22-28
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• 2009

As multiprocessors have been widely adopted in embedded systems, task computation energy consumption should be minimized with several low power techniques supported by the multiprocessors. This paper proposes an energy-aware task scheduling algorithm that adopts both dynamic voltage scaling and power shutdown in multiprocessor environments. Considering the timing and energy overhead of power shutdown, the proposed algorithm performs an iterative task assignment and task ordering for multiprocessor systems. In this case, the iterative priority-based task scheduling is adopted to obtain the best solution with the minimized total energy consumption. Total energy consumption is calculated by considering a linear programming model and threshold time of power shutdown. By analyzing experimental results for standard task graphs based on real applications, the resource and timing limitations were analyzed to maximize energy savings. Considering the experimental results, the proposed energy-aware task scheduling provided meaningful performance enhancements over the existing priority-based task scheduling approaches.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1295-1304
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• 2010

This paper proposes a fault-tolerant data aggregation which provides energy efficient and reliable data collection in wireless sensor networks. The traditional aggregation scheme does not provide the countermeasure to packet loss or the countermeasure scheme requires a large amount of energy. The proposed scheme applies caching and re-transmission based on the track topology to the adaptive timeout scheduling. The proposed scheme uses a single-path routing based on the traditional tree topology at normal, which reduces the dissipated energy in sensor nodes without any countermeasure against packet loss. The proposed scheme, however, retransmits the lost packet using track topology under event occurrences in order to fulfill more accurate data aggregation. Extensive simulation work under various workloads has revealed that the proposed scheme decrease by 8% in terms of the dissipated energy and enhances data accuracy 41% when the potential of event occurrence exists as compared with TAG data aggregation. And the proposed scheme decrease by 53% in terms of the dissipated energy and shows a similar performance in data accuracy when the potential of event occurrence exists as compared with PERLA data aggregation.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.58-60
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• 2001

제한된 전력 원을 사용하는 휴대용기기의 대중화에 따라 제한된 전력 원을 보다 효율적으로 사용할 수 있게 하는 저 전력에 대한 연구가 활발히 진행 중에 있다. 특히 휴대용 기기의 성능이 더욱더 고성능화 됨에 따라 휴대용 기기에도 SRAM, DRAM, SDRAM등의 각종 메모리 시스템이 사용되기 시작하였다. 또한 이러한 메모리 시스템은 전체 시스템에 있어서 주요한 전력소모 요인이 되었다 따라서 본 논문에서는 이러한 메모리 장치에 대한 전력 소모 특성을 분석 수행하였으며 분석 수행 방법에 있어서 기존의 방법과는 다르게 Address, Data, 제어신호등에 따른 에너지 소모 특성을 분석함으로서 기존의 연구와는 다르게 H/W차원뿐 아니라 더 상위레벨의 S/W차원가지의 에너지 소모 절감 기법 개발을 위한 흑은 저 전력 S/W 제작을 위한 자료로서 사용될 수 있는 기초 자료를 제공하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.577-579
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• 2004

전원을 전적으로 배터리에 의존하는 모바일 임베디드 시스템은 배터리 용량의 한계 때문에 효율적인 에너지의 사용이 매우 중요하다. 특히 memory subsystem은 전체 system에서 소모되는 에너지에서 큰 비중을 차지한다. 이 논문은 성능 면에서 cache의 대안이 되고, cache보다 간단한 구조 때문에 전력소모가 훨씬 적은 on-chip scratch-pad memory(SPM)를 효율적으로 이용할 수 있는 소스 코드 변환 방법 및 SPM 관리방법을 제안한다. 각 함수 단위로 코드 변환을 하며, 어떤 변수를 SPM에 할당하기 위한 소스코드 변환을 했을 때, 소스코드 분석만으로 알 수 있는 변수의 정적인 참조 횟수를 가중치로 고려하여, 코드 변환 후 메모리 참조에 의한 실행 시간과 에너지 소모를 계산하고 이를 바탕으로 SPM에 할당한 변수를 결정한 다음 실제 그 코드 변환을 적용한다. 제안된 코드 변환은 컴파일러에 의해 자동화 될 수 있다. 10개의 임베디드 벤치마크 프로그램을 이용하여 본 논문에서 제안하는 방법의 성능 평가를 한 결과, 실행 시간은 평균 23% 향상되고 에너지 소모는 평균 49% 감소함을 알 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6469-6477
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• 2013

As the Internet has grown, energy consumption and GHG emission from internet use have become issues in recent years. On the other hand, such interest in greening the Internet has focused on edge devices, and there is a lack of deeper related studies of the energy wasted by excessive network-connectivity and the savings potential in wired network equipment. This study presents the background and reasonability of studies on the energy efficiency of wired networks in terms of the environment, economy and energy resources. The energy consumption and savings potential of network equipment were also estimated and the major factors of energy consumption was analyzed based on the data, and future studies for the Internet are presented.

• The KIPS Transactions:PartD
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• v.18D no.1
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• pp.45-56
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• 2011

The importance of low-power embedded system is being increased. The studies on low-power system have been performed in issues of hardware architecture and operating system. However because the behaviors of software control the working of hardware devices, the power analysis of software is one of critical issues in energy-efficient embedded system development. This paper proposes a technique to extract tasks from software design models with considering power consumption. We first define the criteria for task extraction, and then propose the way to separate out the task from UML 2.0 design models. Our technique can provide the chance to reduce the power consumption as well as to fulfill the performance requirement in the early phase of software development.

• The KIPS Transactions:PartD
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• v.16D no.6
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• pp.871-880
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• 2009

Along with the complexity and size growth of embedded software, it is critical to meet the nonfunctional requirements such as power consumption as well as functional requirements such as correctness. This paper, apart from the existing studies of source code-based power analysis, proposes an approach of model-based power analysis using UML 2.0. Specially, we focus on the development of energy library to analyze the power consumption of embedded software. Our energy library supports model-based power analysis, and also supports the easy adaption for the change of embedded application.