• Progress in Medical Physics
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• v.20 no.4
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• pp.199-207
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• 2009

It is important to initialize Image Plate (IP) completely for removing residual latent image by sodium lamp for reliability and repeatability of computed radiography (CR) system. The purpose of this study was to evaluate latent images of computed radiography (CR) images respect to delay time after erasure of foregone latent image and its effect, and erasure level. Erasure thoroughness for CR acceptance test from American Association of Physicist in Medicine (AAPM) Report 93 (2006) was also evaluated. Measurements were made on a CR (Agfa CR 25; Agfa, BELGIUM) system. Chest postero-anterior (PA), Hand PA, L-spine lateral radiographs were chosen for evaluation. Chest phantom (3D-torso; CIRS, USA) was used for Chest PA and L-spine lateral radiography. For Hand PA radiography, projections was done without phantom. Except Hand PA radiographs, noise was increased with delay time, and ghost image was appeared on overexposed area. Effect of delay after erasure on latent image was not seen on naked eye, but standard deviation (SD) of pixel value on overexposed area was relatively higher than that of other areas. On Hand PA and Chest PA radiographs, noise were not occurred by adjustment of erasure level. On L-spine lateral images at lower erasure level than standard level, noise including ghost image were occurred because of high tube current. Erasure thoroughness of CR system in our department was to be proved by these evaluation. The results of this study could be used as a baseline for IP initialization and reliability of CR images.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.6
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• pp.47-56
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• 2010

HDD-based RAIDs have been used in high-capacity storage systems for traditional data server. However, their data reliability are relatively low and they consume lots of power since hard disk drive is weak on shock and its power consumption is high due to frequent spindle motor operation. Therefore, this paper presents new SSD based RAID system architecture using various erasure codes. The proposed methode applys Reed-Solomon, EVENODD, and Liberation coding schemes onto file system level and device driver level, respectively. Besides, it uses data allocation method to minimize the side effect of reducing the lifespan of SSD. Detail experimental results show that Liberation code increase wear-leveling rates of SSD based RAID-6 more than other codes. The SSD based RAID system applying erasure codes at the device driver level shows better performance than that at the file system level. I/O performance of RAID-6 system using SSD is 4.5%~8.5% higher than that of using HDD and the power consumption of the RAID system using SSD is 18%~40% less than that of using HDD.

• Journal of Communications and Networks
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• v.13 no.2
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• pp.160-166
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• 2011

In u-healthcare services based on wireless body sensor networks, reliable connection is very important as many types of information, including vital signals, are transmitted through the networks. The transmit power requirements are very stringent in the case of in-body networks for implant communication. Furthermore, the wireless link in an in-body environment has a high degree of path loss (e.g., the path loss exponent is around 6.2 for deep tissue). Because of such inherently bad settings of the communication nodes, a multi-hop network topology is preferred in order to meet the transmit power requirements and to increase the battery lifetime of sensor nodes. This will ensure that the live body of a patient receiving the healthcare service has a reduced level of specific absorption ratio (SAR) when exposed to long-lasting radiation. We propose an efficientmethod for delivering delay-intolerant data packets over multiple hops. We consider forward error correction (FEC) in an erasure correction mode and develop a mathematical formulation for packet-level scheduling of delay-intolerant FEC packets over multiple hops. The proposed method can be used as a simple guideline for applications to setting up a topology for a medical body sensor network of each individual patient, which is connected to a remote server for u-healthcare service applications.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.1-10
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• 2004

This study discusses Application-layer FEC using erasure codes. Because of the simple decoding process, erasure codes are used effectively in Application-layer FEC to deal with Packet-level errors. The large number of parity packets makes the loss rate to be small, but causes the network congestion to be worse. Thus, a redundancy control algorithm that can adjust the number of parity packets depending on network conditions is necessary. In addition, it is natural that high-priority frames such as I frames should produce more parity packets than low-priority frames such as P and B frames. In this paper, we propose a redundancy control algorithm that can adjust the amount of redundancy depending on the network conditions and depending on data priority, and test the performance in simple links and congestion links.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.1
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• pp.62-77
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• 2010

Emerging applications with high data rates will need to transport bulk data reliably in wireless sensor networks. ARQ (Automatic Repeat request) or Forward Error Correction (FEC) code schemes can be used to provide reliable transmission in a sensor network. However, the naive ARQ approach drops the whole frame, even though there is a bit error in the frame and the FEC at the bit level scheme may require a highly complex method to adjust the amount of FEC redundancy. We propose a bulk data transmission scheme based on erasure-resilient code in this paper to overcome these inefficiencies. The sender fragments bulk data into many small blocks, encodes the blocks with LT codes and packages several such blocks into a frame. The receiver only drops the corrupted blocks (compared to the entire frame) and the original data can be reconstructed if sufficient error-free blocks are received. An incidental benefit is that the frame error rate (FER) becomes irrelevant to frame size (error recovery). A frame can therefore be sufficiently large to provide high utilization of the wireless channel bandwidth without sacrificing the effectiveness of error recovery. The scheme has been implemented as a new data link layer in TinyOS, and evaluated through experiments in a testbed of Zigbex motes. Results show single hop transmission throughput can be improved by at least 20% under typical wireless channel conditions. It also reduces the transmission time of a reasonable range of size files by more than 30%, compared to a frame ARQ scheme. The total number of bytes sent by all nodes in the multi-hop communication is reduced by more than 60% compared to the frame ARQ scheme.

• International Journal of Contents
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• v.6 no.4
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• pp.22-29
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• 2010

In flash memory, many previous garbage collection methods only merge blocks statically and do not consider the contents of buffer. These schemes may cause more unnecessary block erase operations and page copy operations. However, since flash memory has the limitation of maximum rate and life cycle to delete each block, an efficient garbage collection method to evenly wear out the flash memory region is needed. This paper proposes a memory compaction scheme based on block-level buffer for flash memory. The proposed scheme not only merges the data blocks and the corresponding log block, but also searches for the block-level buffer to find the corresponding buffer blocks. Consequently, unnecessary potential page copying operations and block erasure operations could be reduced, thereby improving the performance of flash memory and prolonging the lifetime of flash memory.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.5
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• pp.733-739
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• 1987

In this paper, variable threshold detection with weighted pulse code modulation-encoded signals transmitted over Gaussian channels has been investigated. Each bit in the \ulcornerlaw PCM word is weighted according to its significance in the transmitter. It the output falls into the erasure zone, the regenerated sample replaced by interpolation or prediction. To overall system signal to noise ratio for BPSK/PCM speech signals of this technique has been found. When the input signal level was -17 db, the gains in overall signal s/n compared to weighted PCM and variable threshold detection were 5 db and 3 db, respectively. Computer simulation was performed generating signals by computer. The simulation was in resonable agreement with our theoretical prediction.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.6
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• pp.163-172
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• 2003

Proposed in this paper is an authentication mechanism for multimedia streaming data in the Intemet multicast environment. The multicast authentication mechanism is coupled with the packet-level forward error correction code which has been recently applied for a reliable multicast transport transmission. Associated with this, Reed-Solomon erasure code is chosen for tolerating packet loss so that each of the received packets can be authenticated independently of the lost packets.

• The Journal of Korean Institute of Next Generation Computing
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• v.15 no.3
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• pp.7-15
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• 2019

Cloud computing markets are rapidly growing as cost savings and business innovation are being carried out through ICT worldwide. In line with this paradigm, the nation is striving to introduce cloud computing in various areas, including the public sector and defense sector, through various research. In the defense sector, DIDC was established in 2015 by integrating military, naval, air and military computing centers, and it provides cloud services in the form of IaaS to some systems in the center. In DIDC and various future cloud defense systems, It is an important issue to ensure availability in cloud defense systems in the defense sector because system failures such as network delays and system resource failures are directly linked to the results of battlefields. However, ensuring the highest levels of availability for all systems in the defense cloud can be inefficient, and the efficiency that can be gained from deploying a cloud system can be reduced. In this paper, we classify and define the level of availability of defense cloud systems step by step, and propose the strategy of introducing Erasure coding and failure acceptance systems, and disaster recovery system technology according to each level of availability acquisition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1234-1243
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• 1994

We propose an adaptive decoding scheme for a concatenated codes with frequency-hopped spread-spectrum communication system in the presence of a pulse-burst jammer and its performance is analyzed. Concatenated coding system employing binary inner code and Reed-Solomon outer code is investigated and the use of side information is allowed to decode both erasures and errors. Our scheme makes the decoder adapts to the level of jamming by switching between two decoding modes such that the overall block error probability can be reduced. It is shown that the proposed decoding scheme yields a significant performance improvement over a conventional decoding scheme.