• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.129-132
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• 2009

Frame erasure is one of the most difficult problems in voice over IP (VoIP) networks and is a major source of speech quality degradation. In this paper, a frame erasure concealment algorithm based on nonlinear regression analysis is presented to minimize speech quality deterioration in code-excited linear prediction (CELP) based coders. We applied the proposed scheme to the ITU-T G.729 standard and obtained improved perceptual evaluation of speech quality (PESQ) scores compared to the conventional methods.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.347-351
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• 2010

SSD의 칩을 구성하는 셀의 집적도가 높아지고 시스템 오류가 높아짐에 따라, 저장장치의 고신뢰성을 보장해야 하는 필요성은 점점 증가하고 있다. 현재 SSD 의 오류를 복구하기 위한 방법으로 ECC 가 사용되고 있으나 비트단위의 오류복구만 가능하여 복구 성능의 한계를 가지고 있다. 본 논문에서는 SSD 계층구조인 하나의 칩을 디스크로 설정하고 내부에 RAID 시스템을 구성하여 칩 단위의 오류 복구 기법을 제안한다. 제안된 칩 단위의 오류 복구 기법은 기존 하드디스크 기반 RAID 시스템에 적용 되었던 세 가지 Erasure 코드들을 SSD 에 적용한 방법이다. 또한 실험을 통해 각각의 Erasure 코드 성능을 비교하였다.

• 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.

• 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 Information Processing Systems
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• v.15 no.1
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• pp.55-66
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• 2019

Storage system often applies erasure codes to protect against disk failure and ensure system reliability and availability. Liberation code that is a type of coding scheme has been widely used in many storage systems because its encoding and modifying operations are efficient. However, it cannot effectively achieve fast recovery from single disk failure in storage systems, and has great influence on recovery performance as well as response time of client requests. To solve this problem, in this paper, we present HRSF, a Hybrid Recovery method for solving Single disk Failure. We present the optimal algorithm to accelerate failure recovery process. Theoretical analysis proves that our scheme consumes approximately 25% less amount of data read than the conventional method. In the evaluation, we perform extensive experiments by setting different number of disks and chunk sizes. The results show that HRSF outperforms conventional method in terms of the amount of data read and failure recovery time.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.347-350
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• 2013

본 논문에서는 무선 인터넷이 대중화 되면서 프록시 서버의 역할의 중요성과 대용량 데이터 보안, 대용량 트래픽을 처리할 수 있는 확장성이 요구되어지고 있다. 무선 인터넷은 유선 인터넷과 달리 기술 환경과 그 특성상 여러가지 제약점들을 가지고 있다. 낮은 대역폭, 이동성 문제, 네트워크 프로토콜, 보안, 데이터 압축, 캐싱 방법 등 아직 기술적으로 해결하여야 문제점을 가지고 있다. 본 논문에서는 데이터 보안을 위하여 무선 인터넷 프록시 서버에 Erasure code 코드를 사용하여 기밀성, 무결성, 가용성 등을 강화하면서 서버의 성능 저하를 해결하기 위하여 서버 부하분산을 적용시키고자 한다.

• 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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.91-103
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• 2015

This paper presents "The 3-User NOR switching channel based on interference decoding with receiver cooperation" in succession to "Jeju Jong Nang channel code I, II". The Jeju Jong Nang code is considered as one of the earliest human binary coded communication (HBCC) in the world with a definite "1" or "0" binary symbolic analysis of switching circuits. In this paper, we introduce a practical example of interference decoding with receiver cooperation based on the three user Jong Nang NOR switching channel. The proposed system models are the three user Jong Nang (TUJN) NOR logic switching on-off, three-user injective deterministic NOR switching channel and Gaussian interference channel (GIC) with receiver cooperation. Therefore, this model is well matched to Shannon binary symmetric and erasure channel capacity. We show the applications of three-user Gaussian interference decoding to obtain deterministic channels which means each receiver cooperation helps to adjacent others in order to increase degree of freedom. Thus, the optimal sum rate of interference mitigation through adjacent receiver cooperation achieves 7 bits.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1073-1077
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• 2010

This paper proposes a new 4-dimensional(4D) constellation-rotation(CR) method which obtains diversity gain of 4 under Rayleigh fading channels. The proposed scheme uses two consecutive CR operations for the constellation of QAM signals unlike a conventional 2-dimensional(2D) CR method using only one CR operation. The computer simulation results show that the new method outperforms the conventional one even more as both the channel code rate and the erasure ratio increase. In a point of system flexibility, the proposed scheme has a great advantage since the conventional 2D CR scheme can be simply implemented by only changing rotation angle values used in the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.4B
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• pp.427-436
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• 2001

RS product codes are widely used in digital storage systems. There are lots of decoding strategies for product code for short-length RS codes. Unfortunately many of them cannot be applied to long-length RS product codes because of the complexity of decoder. This paper proposes new decoding strategies which can be used in long length RS product codes.