• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.197-203
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• 2012

This paper studies network recovery method using logical multiple ring architecture embedded in WDM optical Internet environment. The multiple ring-based recovery method provides fast and simple network restoration operation, and performs local recovery that is detouring the failed link. The multiple ring architecture can provide higher resource efficiency by sharing the backup routes and reducing the number of spare wavelengths. This paper calculates the required spare capacity ratio using Cut-Sets in the given network topology and performs simulation for comparative analysis.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.348-350
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• 2012

광파장다중화(WDM) 기반 광인터넷 환경에서 논리적인 다중 링 구조에 의한 통신망 복구 기법을 연구한다. 이 방법은 링 토폴로지의 특성을 이용해 빠르고 간단한 복구 동작을 제공하며, 지역적인 복구를 수행한다. 동시에 다중 링 구성을 통하여 대체 경로의 분산과 공유 정도를 높이고 단위 링크당 예약되어야 하는 예비 광파장의 수를 줄임으로써 전체 통신망 자원 이용의 효율성을 높일 수 있다. 본 논문에서는 위험공유 링크그룹(SRLG) 개념을 이용하여 링크 손실을 복구하는데 필요한 예비대역폭 비율을 토폴로지상의 Cut-Set을 이용해 계산하고 이를 실험을 통해 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.11
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• pp.2897-2908
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• 1996

This paper presents an effective call admission control algorithm using the Common Pool on the virtual path in ATM networks. Call admission control decides whether or not to accept a new call, so as to ensure the service quality of both individiual existing calls and of the new call itself. In the proposed algorithm, a new call is accepted when the sum of the bandwidths of existing calls and of the new call will not exceed lind capacity. If the sum of their bandwidths exceed link capacity, reserved bandwidth of Common Pool is considreed to accept the new call. Computer simulation results using a simuple network model are algorithm given to evaluate accuracy and call blocking probability by the proposed method.

• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.891-900
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• 2005

This paper studies network recovery methods for WDM optical mesh networks, concentrating on improving spare resource utilization. The resource efficiency can be obtained by sharing spare resources needed for network recovery. To improve the sharability of spare resources in WDM networks, methods to share backup paths us well as spare capacity should be studied. The proposed method in this paper uses multiple ring-covers and this method provides fast and simple recovery operation by exploiting the characteristics of logical ring topology, and also provides efficient resource utilization by using multiple distributed backup paths to improve the sharability of overall spare resources in the networks. This method can provide layered reliability to network service by enabling hierarchical robustness against multiple failures. The performance results show that the proposed method provide improved resource efficiency for single failure and enhanced robustness for multiple failures.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.83-88
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• 2012

This paper studies the effects of wavelength conversion on self-healing optical networks. We examined the effects of wavelength conversion capability on the backup routing and the spare wavelength utilization. The efficiency of spare wavelength utilization is proportionally increased as the wavelength conversion capability increases, different from the call blocking probability for which about 30% of wavelength conversion capability shows nearly the same performance as full wavelength conversion capability. The spare resource utilization efficiency can be improved by using alternate routing and wavelength assignment algorithms.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.530-532
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• 2003

이 논문에서는 Semi-lightpath를 이용한 복구 경로의 준-동적 조합에 의한 WDM 망 복구 기법을 제안한다. 제안된 기법에서는 광파장 채널의 종단 노드간에 여러 개의 부분적인 대체 광파장 채널을 연결함으로써 복구를 수행한다. 이 방법은 정적인 복구 기법과 동적인 복구 기법의 장점을 모두 수용하여 빠른 복구 속도와 복구 동작의 유연성을 동시에 제공하며, 종단간 대체 경로를 여러개의 부분적인 대체 경로로 분할함으로써 복구 경로 및 예비 대역폭의 공유 정도를 높여 통신망 자원 이용의 효율성을 높일 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1421-1424
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• 2003

무선 ad-hoc 네트워치 환경이란 유선망 하부구조를 갖지 않고 이동 호스트들만으로 구성되는 임시적 네트워크 환경을 말한다. 이러한 환경에서는 저대역폭 저전력, 잦은 오류 등의 특성에도 불구하고 이동 호스트들이 라우팅 기능을 수행해야 하므로, 보다 효율적인 라우팅 프로토콜이 요구된다. 본 논문에서는 무선 ad-hoc 네트워크 환경에서 이동 호스트들이 라우팅을 위한 주기적 라우팅 정보 방송을 하지 않도록 하면서 경로를 필요로 하는 호스트가 자발적으로 경로를 찾는 과정을 시작하여 하나 이상의 경로 응답을 밭고 그 중에서 하나의 경로를 선택하도록 하는 프로토콜을 제안한다. 경로 응답을 받은 나머지 경로는 예비경로가 되어, 라우팅 역할을 하는 이동 호스트들의 이동으로 데이터 전송 경로가 실패하는 경우에 빠른 경로 재 설정을 가능하게 한다. 이러한 기법은 데이터의 송수신 패턴이 지역성을 갖는 경우에 매우 유용한 기법이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.850-858
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• 2000

Increased network reliability is required as the size of communication network becomes larger and the bandwidth requirement is increasing. And preparing of backup path is required to protect the network from serious network failures in high speed network. In this paper, we construct multiple logical networks on a physical ATM network according to the ATM bearer service category(CBR, rt-VBR, nrt-VBR, ABR, UBR) defined by ATM Forum to support the required QoS(Quality of Service) and to manage the network more efficiently. We use backup path restoration algorithm rather than dynamic restoration to achieve rapid restoration when active path fails and we use fault management function in TINA. We propose a restoration scheme that is suitable for high-speed network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.1
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• pp.21-28
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• 1990

In this paper, the effects of Intersymbol Interference(ISI) of Gaussian filtered minimum shift Keying (GMSK) with two-bit differential defection on the probability of error is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels and a closed form for the probability of error is derived. Numerical results are presented for cased of interest, BT=0.25 to 0.4, taking fading rate $f_\rho$T as a parameter. It is shown that the probability of error taking the ISI of the only one adjacent bit into consideration is accurate enough to evaluate the performance of GMSK with two-bit differential detetion.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.331-337
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• 2003

This paper represents 50 ㎓ narrow band pass filters for fiber optical communication fabricated by dual ion beam sputtering method. We have analyzed the characteristics of the TA$_2$ $O_{5}$ and $SiO_2$ single layers in order to optimize the process conditions for the 50 ㎓ narrow band pass filters, and controlled the film thickness uniformity to less than 0.1 nm deviation by dual peak spike filter pre-deposition. We designed and fabricated 50 ㎓ narrow band pass filters that consist of 216 layers including 4 cavities based on quarter wave optical thickness. Class substrates with high thermal expansion coefficients were used to reduce the film stress. Anti-reflection coating at the rear side of the substrate was also needed to reduce the optical thickness errors of the Optical Monitoring System caused by multiple beam interference between the front side and the rear side of substrate. The optical characteristics of this 50 ㎓ narrow band pass filters are insertion loss of 0.40 ㏈, pass band ripple of 0.20 ㏈, and pass bandwidth at -0.5 ㏈ of 0.20 nm. and isolation bandwidth at -25 ㏈ of 0.6 nm, which satisfy specifications of dense WDM system in fiber optical communications.tions.