• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.465-474
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• 2005

In this paper, a directional reconstruction of lost block in image over noisy channel is presented. DCT coefficients or pixel values in the lost blocks are recovered by using the linear interpolation with available neighboring blocks that are adaptively selected by the directional measure that are composed of the DDC (Difference of DC opposite blocks)and SAC(Similarity of AC opposite blocks) between opposite blocks around lost blocks. The proposed directional recovery method is effective for the strong edge and texture regions because we do not make use of the fixed 4-neighboring blocks but exploit the varying neighboring blocks adaptively by the directional information in the local image. In this paper, we describe the novel directional measure(CDS: Combination of DDC and SAC) composed of the DDC and the SAC and select the usable block to recover the lost block with the directional measure. The proposed method shows about 0.6dB PSNR improvement in average compared to the conventional methods.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.375-384
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• 2002

In the current Internet, the QoS of interactive applications is hardly guaranteed because of variable bandwidth, packet loss and delay. Moreover, VoIP which is becoming an important part of the information infra-structure in these days, is susceptible to network packet loss and end-to-end delay. Therefore, it needs error control mechanisms in network level or application level. The FEC-based error control mechanisms are used for interactive audio application such as VoIP. The FEC sends a main information along with redundant information to recover the lost packets and adjusts redundant information depending on network conditions to reduce the bandwidth overhead. However, because most of the error control mechanisms do not consider end-to-end delay but packet loss rate, their performances are poor. In this paper, we propose a new error control algorithm, SCCRP, considering packet loss rate as well as end-to-end delay. Through experiments, we confirm that the SCCRP has a lower packet loss rate and a lower end-to-end delay after reconstruction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.989-998
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• 2014

Recently volcanic eruptions and activities occurring in many parts of world have become a common global concern to many countries. The severity of these Volcanic disasters, such as of Mt. Eyjafjallajokull in Iceland and Mt. Merapi in Indonesia, have caused damages and causalities reaching astronomical levels. The infrastructure is categorized into 18sections that appropriately reflecting the survey data collected from various government agents, current inhabitant and engineers to accumulate a database on the priorities and preferences of restoring and reconstructing many kinds of infrastructure and facilities. The survey data was collect by using the "Likert 5 Scale Method" which emphasized the importance and priority of reconstruction and restoration for the specific facilities and infrastructures. The data was corrugated, organized and used in plotting and planning a strategic recovery agenda. The survey results were analyzed and verified to ensure the validity and reliability of the data by using chi-square test. This paper presents that recovery period and recovery cost to the total damage of infrastructure and facilities were used to make a recovery network with implemented construction management method. The research is expected that a more efficient and prompt recovery protocol and recovery plan can be executed and can be use as a reference and database.

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.401-408
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• 2005

We propose a new MPLS restoration scheme that uses network resources more efficiently and minimizes the backup path cost effectively. Contrary to other restoration strategies, the proposed restoration scheme starts the recovery action at the selected node of a working LSP. At LSP setup, the working and backup path cost is evaluated and the starting node of restoration is designated. By doing so, the restoration speed could be further increased and resource utilization could be maximized. We simulated the proposed scheme and compared with other restoration and protection schemes. The result shows that our scheme can provide fast restoration with acceptable delay and loss characteristics.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.5
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• pp.143-150
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• 2009

In this paper, we present a spatial domain error concealment method to recover a lost block in intra-coded frames. The edge directions of the lost block are estimated by the difference values of the border pixels of the accurately received blocks. The lost block is interpolated according to the estimated edge directions. Our algorithm can adaptively recover a lost block according to the estimated edge direction. The distances between pixels are used as weights for interpolation. In spite of the low computational cost, the proposed method outperforms the previous methods in objective and subjective qualities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1496-1502
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• 1998

In this paper, a real-time audio broadcasting service system which is robust to loaded traffic on the Internet is developed. For implementing reliable real-time data transfer, the transfer characteristics of TCP/IP and UDP/IP was compared and analyzed. For lost packet recovery, redundant audio data algorithm was used and interleaving technique was applied for scattering consecutive packet loss. Test results showed, when using TCP/IP, pause occurred during playback, and when using UDP/IP, a stable receive rate was noticeable but the quality of the sound was lower than that of uisng TCP/IP. The recovery rate using redundant audio data and interleaving technique is shown in Fig. 9 and the delay is shown in Fig 4.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.409-411
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• 2018

기존에 게임 업계에서는 데이터베이스 관리를 위해 중앙에 집중된 서버 관리 시스템을 사용해 왔다. 때문에 계정 도용 등의 부정사용이나 관리 상의 사고 등에 취약한 모습을 보여 왔다. 현재는 사고 발생한 경우 주로 서버 전체를 복구하는 등의 조치를 위하여 문제를 보완해 왔는데, 백업 과정에서 문제가 발생하면 복구 불가능한 손실이 발생할 수밖에 없다. 이에 본 연구에서는 앞서 말한 사고로 인해 데이터가 손실되더라도, 손실된 데이터를 복구할 방법으로 블록체인 기술을 활용해보고자 하였다. 블록체인 기술을 활용하여 게임 시스템 속 데이터베이스의 일부를 분산 저장하는 방법을 실험해 봄으로서 앞서 제기한 문제들을 해결해 보고자 한다.

• Journal of KIISE:Information Networking
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• v.31 no.2
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• pp.233-241
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• 2004

In this paper, we propose a packet-lossless fast rerouting scheme at a link/node fault in MPLS (Multiprotocol Label Switching) network with minimized accumulated buffer delay problem at ingress node. The proposed scheme uses a predefined, alternative LSP (Label Switched Path) In order to restore user traffic. We propose two restoration approaches. In the first approach, an alternative LSP is initially allocated with more bandwidth than the protected working LSP during the failure recovery phase. After the failure recovery, the excessively allocated bandwidth of the alternative LSP is readjusted to the bandwidth of the working LSP. In the second approach, we reduce the length of protected working LSP by using segment-based restoration. The proposed approaches have merits of (ⅰ) no buffer delay problem after failure recovery at ingress node, and (ⅱ) the smaller required buffer size at the ingress node than the previous approach.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.87-94
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• 2003

When faults occur in a distribution network, blackout loads must be restored as fast as possible to minimize interruption of electric service. This paper presents an expert system to restore distribution networks. The system is designed to minimize switching operations in a heuristic sense by using heuristic rules. The restoration process is converted to the feasible path finding problem in the state space of expert system by application of general topological knowledge base. Multiple load transfer algorithm is proposed to deal with complex situations.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.52-53
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• 2006

현재 국내 배전자동화 시스템의 고장구간을 최소한으로 하는 불필요 정전구간 복구시스템은 고장발생 시 중앙에서 고장구간을 판단하고 Fuzzy Rule을 이용한 복구해를 통하여 계통의 Device들을 운영자가 직접 제어하는 방식이다. 이러한 방식은 원격으로 제어가 가능하며 운영자가 직접 상황에 따라 적절한 판단을 하여 신뢰성이 크다는 장점이 있지만, 운영자의 실수에 의해서 계통에 문제가 발생할 가능성도 있고, 정전복구시간 면에서 볼 때 오퍼레이터의 실수에 의해 생기는 복구지연시간은 소비자들에게는 경제적 손실 및 불편을 초래할 수 있다. 따라서 이러한 운영자의 실수를 미연에 방지하고 정전복구 시간 또한 가급적 줄일 수 있는 방안을 마련하는 것이 필요하다. 본 연구에서 제안하는 Multi-Agent 기반의 분산형 정전복구 시스템은 중앙의 제어를 통하지 않고 계통 내의 Device들이 Agent 개념의 지능을 가지고 상호 정보교환을 통하여 고장구간을 판단하고 정전을 복구하는 시스템으로 현재 배전자동화 시스템의 복구시간을 1분 이내로 단축시킬 수 있는 시스템을 제안하였다. 간단한 배전계통을 구성하고 전력계통의 현재 통신망중 유/무선의 대표적인 LAN 및 CDMA 통신을 이용한 사례연구를 통해 제안한 시스템에서의 정전구간 1분 이내의 복구시간을 입증하였다.