• Electronics and Telecommunications Trends
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• v.25 no.5
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• pp.84-96
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• 2010

국내 휴대폰 시장은 최근 급격한 변화의 시기를 맞고 있다. 음성정보 송 수신과 단순한 개인정보관리, 또는 멀티미디어 데이터 처리에 주력하던 피처폰 시장은 고사양의 운영체제, HD급 비디오, 수십만 가지의 앱(App.; Application), 고성능 디스플레이로 대표되는 스마트폰 시장으로 급격히 전환되고 있다. 이러한 스마트폰의 고사양화는 모바일프로세서, 베이스밴드 칩, 다양한 센서를 포함하는 스마트폰 하드웨어와 데스크톱 수준에 근접하는 고사양의 운영체제가 견인하고 있다. 특히, 모바일 프로세서는 스마트폰 기술 발전을 견인하는 핵심 부품으로서 다수의 프로세서와 외부인터페이스 장치를 포함하는 고성능, 저전력의 시스템온칩(SoC)이며 모바일프로세서의 동작속도, 전력소모량 등은 스마트폰의 성능을 가늠하는 척도로 인식되고 있다. 최근, 모바일프로세서는 스마트폰 시장을 넘어서 넷북, MID, 스마트 TV 등 다양한 산업영역에서 채용되고 있으며 2018년에 100억 개의 제품이 생산될 것으로 전망되어 모바일 시장의 폭발적인 성장을 견인하는 핵심 부품이다.

• Journal of the Korea Society of Computer and Information
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• v.18 no.12
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• pp.1-9
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• 2013

Even though the multiple pages TLB are effective in improving the performance, a conventional method with OS support cannot utilize multiple page sizes in user application. Thus, we propose a new multiple-TLB structure supporting multiple page sizes for high performance and low power consumption without any operating system support. The proposed TLB is organised as two parts of a S-TLB(Small TLB) with a small page size and a L-TLB(Large TLB) with a large page size. Both are designed as fully associative bank structures. The S-TLB stores small pages are evicted from the L-TLB, and the L-TLB stores large pages including a small page generated by the CPU. Each one bank module of S-TLB and L-TLB can be selectively accessed base on particular one and two bits of the virtual address generated from CPU, respectively. Energy savings are achieved by reducing the number of entries accessed at a time. Also, this paper proposed the simple 1-bit LRU policy to improve the performance. The proposed LRU policy can present recently referenced block by using an additional one bit of each entry on TLBs. This method can simply select a least recently used page from the L-TLB. According to the simulation results, the proposed TLB can reduce Energy * Delay by about 76%, 57%, and 6% compared with a fully associative TLB, a ARM TLB, and a Dual TLB, respectively.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.504-507
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• 2008

유비쿼터스 센서 네트워크 환경에서 센서 운영체제 기술의 중요성은 날이 갈수록 높아져 가고 있으며 센서 하드웨어의 하드웨어 자원의 부족, 극소형의 크기, 저전력으로 운용되어야 하는 특성을 보충하기 위한 노력은 이미 많은 연구가 진행되었으며 진행되고 있다. 하지만 물리적인 세계와 디지털 세계를 연결하는 역할을 하는 센서에서 데이터의 신뢰성은 반드시 보장이 되어야 하는 요소임에도 많은 부분이 간과되어 왔다. 데이터의 신뢰성을 보장하기 위해서 센서는 안정성을 확립할 수 있어야 하며 다양한 환경에 동적으로 적응이 가능해야만 한다. 그리하여 본 논문에서는 센서에 안정성을 확립할 수 있는 방법과 동적인 환경에 적응이 쉬운 형태의 확장이 쉬운 구조를 가질 수 있는 방법을 제시함으로서 센서의 신뢰성에 기여할 수 있도록 한다.

• The Journal of the Korea Contents Association
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• v.15 no.1
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• pp.31-43
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• 2015

For battery based real-time embedded systems, high performance to meet their real-time constraints and energy efficiency to extend battery life are both essential. Real-Time Dynamic Voltage Scaling (RT-DVS) has been a key technique to satisfy both requirements. In this paper, we present an efficient RT-DVS algorithm called EccEDF that is designed based on ccEDF. The proposed algorithm can precisely calculate the maximum unused utilization with consideration of the elapsed time while keeping the structural simplicity of ccEDF, which overlooked the time needed to run the task in calculating the available slack. The maximum unused utilization can be calculated by dividing remaining execution time($C_i-cc_i$) by remaining time($P_i-E_i$) on completion of the task and it is proved using Fluid scheduling model. We also show that the algorithm outperforms ccEDF in practical applications which is modelled using a PXA250 and a 0.28V-to-1.2V wide-operating-range IA-32 processor model.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.5
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• pp.665-671
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• 2011

The Competitiveness of Hybrid hard disk drive(H-HDD) for solid state disk(SSD) comes from both lower power consumption and higher reading speed. This paper suggests a prefetching scheme that can improve the performance of Non-Volatile cache(NVCache) memory installed on the H-HDD through prefetching disk blocks as well as files to the NVCache. The proposed scheme makes the highly used data such as booting files copy to the NVCache as an unit of file and the frequently accessed blocks copy to the NVCache. This prefetching is done on the idle time of disk queue and the priorities of prefetched target blocks are based on both time and spatial locality of blocks. Experiments results show that the suggested method can improve response time of H-HDD and also lower the power consumption.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.641-644
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• 2008

This paper describes the GUI implementation of an intelligent embedded system which can be used for a personal information platform and an industrial mobile application system. It shows the architecture and the necessary structure and components of X Window graphic system. The embedded system used in this paper has low power and high performance processor, and has a large memory size with a nand-flash memory device. We configured the linux kernel with a TIT-LCD and touch screen device for the operation of X Window system. And we used GTK+2 for running application softwares on the platform embedded system. The GUI library of GTK+2 is useful for providing the same graphics programming environment with host Linux PC. We have developed in this paper the X Window system and the GUI environment for GTK+2 in a new embedded system, and verified the full operation of X Window system and application softwares using GTK+2. The embedded system with large memory size can be used in X Window application softwares for providing a personal information service with a mobile embedded system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.137-140
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• 2013

Conventionally embedded devices used simple operating system (OS); however, the number of embedded devices using Linux as OS is increasing to keep up with hardware's performance improvement and customer's various needs. While embedded devices using Linux can take advantage of expandability, generality, portability, Linux's flexibility nature may cause undesirable overheads because of its increased complexity. One such overhead makes boot stage optimization essential in most embedded systems, where many features are redundant and possible to be removed or reconfigured. This paper applies well-known software optimization technique for Linux's boot stage to an CLM9722 DTK, measures the results, and studies about limitation of such techniques from hardware dependancy on the standard framework of Linux. The booting time from power-on until completion were decreased by 33% approximately.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.3
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• pp.117-124
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• 2018

Wearable devices have become widespread. Fitness band is one of common wearable devices, providing useful functions. It helps users to monitor and collect their status such as heart rate and travel distance. Wearable devices, including fitness bands, are designed in small size and it ends up having small battery capacity. In that regard, it is necessary to expand the lifetime of wearable devices. Conventional power management scheme of wearable devices is based on DVFS Ondemand Governor and peripheral control by timeout event, such as turning off the LCD. In this paper, we propose a hybrid governor applying hardware supporting low power mode such as sleep mode to exploit the periodicity of fitness band task. In addition, we show hybrid governor outperforms in power consumption than conventional power management scheme of wearable devices based on Ondemand Governor through experiments.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.268-271
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• 2014

iOS, Android 등의 모바일 운영체제를 탑재한 스마트폰 기술의 급속한 발전으로 인해 다양한 모바일 어플리케이션들이 개발 되고 있다. 그 중에서 모바일을 통해 물품을 관리 하기 위한 기반 기술로 안드로이드의 NFC 기술을 이용하거나 블루투스 바코드 스캐너와 스마트폰의 연계 기술을 이용하고 있는 것이 현재의 추세이다. NFC 기술 또는 단순 블루투스 바코드 스캐너와의 연계만으로는 공간 내 대량의 물품을 지능적으로 관리 하기에는 한계가 있는 것이 사실이다. 본 논문에서는 Beacon 기술을 이용하여 기존의 NFC 기술 및 바코드 스캐너만으로 구현이 불가능했던 문제들을 해결할 방안을 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.23-31
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• 2011

Recently, Solid state disk is mainly used because this device has lower power consumption as well as higher response time. But it features higher price and lower performance at delete and write operations compared with HDD. To compensate this defect, Hybrid hard disk with internal non-volatile flash memory was issued. This NVCache is used as a kind of cache for disk blocks. In this paper, an I/O scheme for H-HDD is proposed for improving low power consumption as well as response time. Our method is to use this NVCache as read cache mainly and write cache when write requests are concentrated. In read cache operation, disk blocks with higher priority determined on basis of time as well as spatial localities are prefetched, which can improve response time. The write operation is conducted only at write peak time as disk spindle up costs higher battery power as well as response time. Experiments results show that the suggested method can improve response time of H-HDD and lower the power consumption.