• Journal of the Korea Society of Computer and Information
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• v.21 no.5
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• pp.1-10
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• 2016

Magnetic disks have been used for decades in auxiliary storage devices of computer systems. In recent years, the use of NAND flash memory, which is called SSD, is increased as auxiliary storage devices. However, NAND flash memory, unlike traditional magnetic disks, necessarily performs the erase operation before the write operation in order to overwrite data and this leads to degrade the system lifetime and performance of overall NAND flash memory system. Moreover, NAND flash memory has the lower endurance, compared to traditional magnetic disks. To overcome this problem, this paper proposes EPET (Enhanced Prediction and Elapsed Time) wear leveling technique, which is especially efficient to portable devices. EPET wear leveling uses the advantage of PET (Prediction of Elapsed Time) wear leveling and solves long-term system failure time problem. Moreover, EPET wear leveling further improves space efficiency. In our experiments, EPET wear leveling prolonged the first bad time up to 328.9% and prolonged the system lifetime up to 305.9%, compared to other techniques.

• Journal of Aerospace System Engineering
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• v.4 no.2
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• pp.32-37
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• 2010

Use of wireless portable devices, like mobile phones, PDAs and Laptops is explosively increasing. Used in the aircraft, these PEDs can introduce EMI problem to aircraft Com/Nav systems. This paper addresses some foreign research result on interference caused by PEDs which are used onboard and policy of Japan and USA to limit use of PED on board.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.12
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• pp.491-498
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• 2016

Recently leakages of confidential information and internal date have been steadily increasing by using booting technique on portable OS such as Windows PE stored in portable storage devices (USB or CD/DVD etc). This method allows to bypass security software such as USB security or media control solution installed in the target PC, to extract data or insert malicious code by mounting the PC's storage devices after booting up the portable OS. Also this booting method doesn't record a log file such as traces of removable storage devices. Thus it is difficult to identify whether the data are leaked and use trace-back technique. In this paper is to propose method to help facilitate the process of digital forensic investigation or audit of a company by collecting and analyzing BIOS firmware images that record data relating to BIOS settings in flash memory and finding traces of portable storage devices that can be regarded as abnormal events.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.1
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• pp.1-8
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• 2007

In this paper, we developed a file system architecture for portable multimedia devices. To enhance user convenience, the information about the stored files should be easily retrieved and organized. We defined NMD (Networked MetaData), which can organize the files in networked fashion by attaching user-defined attributes and relation between files. The NMD is stored in flash memory to utilize its nonvolatile property and low-power consumption, while multimedia files are stored in hard disk, an inexpensive mass storage. The experimental implementation showed that this architecture was able to save about 10% power compared to the hard disk NMD-store.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.267-269
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• 2006

Recently, flash memories are one of best media to support portable computer's storages in mobile computing environment. The features of non-volatility, low power consumption, and fast access time for read operations are sufficient grounds to support flash memory as major database storage components of portable computers. However, we need to improve traditional Indexing scheme such as B-Tree due to the relatively slow characteristics of flash operation as compared to RAM memory. In order to achieve this goal, we devise a new indexing scheme called F-Tree. F-Tree improves tree operation performance by compressing pointers and keys in tree nodes and rewriting the nodes without a slow erase operation in node insert/delete processes.

• Proceedings of the Korean Society of Computer Information Conference
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• 2014.01a
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• pp.1-4
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• 2014

Although physical modeling synthesis is becoming more and more efficient in rich and natural high-quality sound synthesis, its high computational complexity limits its use in portable devices. This constraint motivated research of single-instruction multiple-data many-core architectures that support the tremendous amount of computations by exploiting massive parallelism inherent in physical modeling synthesis. Since no general consensus has been reached which grain sizes of many-core processors and memories provide the most efficient operation for sound synthesis, design space exploration is conducted for seven processing element (PE) configurations. To find an optimal PE configuration, each PE configuration is evaluated in terms of execution time, area and energy efficiencies. Experimental results show that all PE configurations are satisfied with the system requirements to be implemented in portable devices.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.720-740
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• 2011

Wi-Fi-enabled portable devices have recently been introduced into the consumer electronics market. These devices download or upload content, from or to a host machine, such as a personal computer, a laptop, a home gateway, or a media server. This paper investigates the fairness among multiple Wi-Fi-enabled portable devices in a home network when they are simultaneously communicated with the host machine. First, we present that, a simple IEEE 802.11-based home network suffers from unfairness, and the fairness is exaggerated by the wireless link errors. This unfairness is due to the asymmetric response of the TCP to data-packet loss and to acknowledgment-packet loss, and the wireless link errors that occur in the proximity of any node; the errors affect other wireless devices through the interaction at the interface queue of the home gateway. We propose a QoS-provisioning framework in order to achieve per-device fairness and service differentiation. For this purpose, we introduce the medium access price, which denotes an aggregate value of network-wide traffic load, per-device link usage, and per-device link error rate. We implemented the proposed framework in the ns-2 simulator, and carried out a simulation study to evaluate its performance with respect to fairness, service differentiation, loss and delay. The simulation results indicate that the proposed method enforces the per-device fairness, regardless of the number of devices present and regardless of the level of wireless link errors; furthermore it achieves high link utilization with only a small amount of frame losses.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.678-683
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• 2010

This paper presents a wireless (contactless) charging technique with a new core material called permalloy. For charging portable devices wirelessly, ferrosilicon or ferrite has been conventionally used. Due to high permeability of permalloy, charging efficiency can be significantly improved and subsequently this high efficiency increases charging distance between charger and portable devices. Comparative experimental studies demonstrate that the charging performance and efficiency with permalloy employed are significantly improved. The proposed wireless charging techniques can be used to charge portable devices efficiently.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.11
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• pp.105-113
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• 2004

This paper proposes 3D graphics accelerator, especially rendering unit, for portable devices. The existing 3D architecture is not suitable for portable devices because of its huge size. To reduce the size, we use iterative architecture and fixed-point calculation. In this paper, we suggest the format of fixed-point comparing with the result images, and some special technique to control. Finally, it is implemented with FPGA and 0.25um ASIC technology respectively. The ASIC chip can execute 47.88M pixels per second. The size of ASIC chip is 4.9287mm*4.9847mm and the power consumption is 263.7mW with 50MHz operation frequency.

• IEMEK Journal of Embedded Systems and Applications
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• v.8 no.5
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• pp.273-283
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• 2013

The traditional medical equipments are devices used by medical professionals but not used in public environment. Common people, however, require light-weight medical devices to make healthcare for themselves nowadays. Those medical devices are used to monitor personal health status such as blood pulse, blood pressure, diabetes. Also, some of them are operated in mobile environment called u-healthcare. This paper implements a portable healthcare system composed of $SpO_2$(Saturation of Partial Pressure Oxygen) sensors and a gateway for detecting hypoxemia during people's leasure activity such as climbing or hiking. The $SpO_2$ sensor is designed as watch style to support dynamic exercise and the gateway is designed as necklace style to support the elderly. The result of a performance evaluation shows that the performance of the $SpO_2$ sensor using reflection technology is not lower than that of a clairvoyant styled $SpO_2$ sensor.