• 한국통신학회논문지
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• 제25권9A호
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• pp.1441-1451
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• 2000

There are two types of protection switching : a) automatic switching and b) forced switching. The switching mechanism is generally realised by OAM functions, therefore, the required OAM information field should be reserved in the PLOAM cells. This paper proposes an unidirectional and a bidirectional protection switching method and potential advantages. The unidirectional protection switching method can be faster than the bidirectional method because the unidirectional method does not require an APS protocol for protection switching. The bidirectional protection switching method uses APS K1 byte and K2 byte, which is included in octets of a PST message through downstream or upstream PLOAM cells, for protection switching. As making comparisons between the unidirectional and the bidirectional protection. switching method, this paper proposes an effective constructing method for ATM-PON network.

• 전기학회논문지
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• 제62권6호
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• pp.744-749
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• 2013

The protection switching technology is widely adopted in the fiber-optical transmission equipments based on TDM(Time Division Multiplexing), such as PDH, SDH/SONET. A variety of protection switching algorithms for Ethernet networks and the progress of standardization are summarized in the document. There are several kinds of protection switching algorithms for Ethernet networks, such as STP, RSTP, MSTP and etc. However, since Ethernet signal move through detour route, it causes much time to recover. Accordingly, it is difficult to secure a usability of Ethernet networks and QOS(Quality of Service). Also, if the protection switching protocol standardized by IEEE and ITU-T is used, it remains a inherent network switching time for protection. Therefore, a specific protection switching algorithm for Ethernet are needed for seamless and stable operation of Ethernet networks service for Distribution Automation System(DAS). A reliable protection algorithm with no switching delay time is very important to implement Self-healing service for DAS. This study of FPGA based protection switching algorithm for Ethernet networks shows that in case of faults occurrence on distribution power network, immediate fault isolation and restoration are conducted through interaction with distribution equipments using P2P(Peer to Peer) communication for protection coordination. It is concluded that FPGA based protection switching algorithm for Ethernet networks available 0ms switching time is crucial technology to secure reliability of DAS.

• Journal of Communications and Networks
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• 제8권2호
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• pp.228-233
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• 2006

Survivability is a very important requirement for the deployment of broadband networks because out of service links can affect volumes of traffic even if it is a very short time. And the data paths of broadband networks, which are critical for traffic engineering, are always necessary to be well protected. The procedure of protection or restoration for a path is initiated when failure is detected within the working path. In order to minimize the influence on transmission quality caused by the failure of links and to provide a definite time for the recovery from the failure, the protection switching time (PST) should be carefully considered in the path arrangement. Several researches have been devoted to construct the protection and restoration schemes of data paths over dense wavelength division multiplexing (DWDM) networks, however, there was rare research on the design of data paths with guaranteed protection switching time. In this paper, the PST-guaranteed scheme, which is based on the concept of short leap shared protection (SLSP), for the arrangement of data paths in DWDM networks is proposed. The proposed scheme provides an efficient procedure to determine a just-enough PST-guaranteed backup paths for a working path. In addition to selecting the PST-guaranteed path, the network cost is also considered in a heuristic manner. The experimental results demonstrate that the paths arranged by the proposed scheme can fully meet the desired PST and the required cost of the selected path is competitive with which of the shared path scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권7호
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• pp.2568-2588
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• 2021

Shared mesh protection (SMP) protects traffic against failures occurring in a working path, as with linear protection, and allows resource sharing of protection paths with different endpoints. The SMP mechanism coordinates multiple protection paths that require shared resources when failures occur on multiple working paths. When multiple failures occur in SMP networks sharing limited resources, activation can fail because some of the resources in the protection path are already in use. In this case, a node confirming that a resource is not available has the option to wait until the resource is available or to withdraw activation of the protection path. In this study, we recognize that the protection switching time and the number of protected services can be different, depending on which option is used for SMP networks. Moreover, we propose a detailed design for the implementation of SMP by considering options and algorithms that are commonly needed for network nodes. A simulation shows the performance of an SMP system implemented with the proposed design and utilizing two options. The results demonstrate that resource utilization can be increased or protection switching time can be shortened depending on the option selected by the network administrator.

• ETRI Journal
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• 제31권5호
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• pp.631-633
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• 2009

We introduce an improved Ethernet ring protection method, selective filtering database (FDB) advertisement, to minimize traffic overshoot in the event of a failure or recovery. On the protection switching event, the proposed method makes all ring nodes perform an FDB flush except the FDB entries associated with their client subnets. Then, ring nodes rapidly exchange their client MAC address lists so that their FDBs are immediately updated by indirect MAC address learning. The proposed scheme guarantees fast and reliable protection switching over the standard scheme.

• 전자공학회논문지
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• 제53권9호
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• pp.26-37
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• 2016

현재 전달망의 핵심기술은 링크 또는 노드 장애가 발생했을 경우에 경로 이중화를 통해 50ms이내에 망을 복구하는 OAM 및 보호절체 기술이다. 개별 통신사업자, 지방/중앙 정부, 중요 기업의 전달 망은 장애에 대한 실시간 망 복구를 위해 보호 서브네트워크를 개별적으로 설정, 관리되고 있다. 그래서 개별 보호 서브네트워크의 종단 노드에 대해 노드 이중화를 적용하여 종단 노드 장애에 대해 대비하는 것이 중요하다. 하지만 MPLS-TP, 캐리어 이더넷과 같은 패킷 전달망에서 선형 보호절체가 적용되는 보호 서브네트워크는 이중 노드 상호 연결 방안이 존재하지 않는다. 비록 이더넷 링 보호절체는 이중 노드 상호 연결방안을 포함하고 있지만 이더넷 링 보호절체의 기술적 특성상 연결 노드에서 장애가 발생하면 전이 트래픽이 급격하게 증가될 수 있다. 본 논문에서는 보호 서브네트워크에서 연결 노드 이중화를 위한 선형 보호절체 적용 방안을 제시한다. 그리고 링크와 상호 연결 노드의 장애에 대한 여러 실험을 통해 제안된 선형 보호와 링 보호 프로세스의 다양한 조합이 어떻게 다중 보호 서브네트워크에서 서비스 트래픽의 복구 탄력성에 영향을 미치는 지를 분석한다.

• Journal of Communications and Networks
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• 제9권4호
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• pp.377-382
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• 2007

This paper presents a new enhanced dynamic and multilayer protection(DMP) routing scheme that considers cooperation between packet and wavelength switching domain in order to minimize the resource consumption. The paper describes the architecture of the multilayer network scenario and compares the proposed algorithm with other routing mechanisms applying protection at the IP/multi-protocol label switching(MPLS) layer or at the optical layer. Simulation results show that DMP reduces the number of optical-electrical-optical(o-e-o) operations and makes an efficient use of the network resources compared to non-multilayer proposals.

• 전기학회논문지
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• 제58권2호
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• pp.292-300
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• 2009

This paper presents an LED BLU driving circuit with a local-dimming structure. The efficiency of the proposed LED driver has been improved by parallel driving 8 serial-connected LED arrays. It employed the soft-switching boost converter topology to reduce the switching power loss of the hard switching boost converter. Soft- and hard-switching converters have the same structure except that the free-wheeling diode in the hard-switching converter is replaced with the n-channel MOSFET in the soft-switching one. The proposed boost converter was compared with the hard switching converter. The soft-switching converter reveals superior ripple and efficiency. A smaller inductance can be used for the soft-switching converter contrasting to the hard-switching one. We also studied on an over-voltage protection circuit of the output of the driver at the no load condition. The protection circuit was applied to the proposed driver, and its operation was confirmed by experiment. Using a local-dimming technique, power consumption of LCD BLUs can be reduced as low as possible according to the brightness of its image.

• 한국초전도ㆍ저온공학회논문지
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• 제19권3호
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• pp.49-53
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• 2017

The superconducting magnets have a large inductance as well as high operating current. Therefore, mega-joule scale energy can be stored in the magnet. The energy stored in the magnet is sufficient to damage the magnet when a quench occurs. Quench heater and dump resistor can be used to protect the magnet. However, using quench heater to create quench resistors through heat transfer can be slower than instantly switching resistors. Also, electrical short, overheating and breakdown can occur due to quench heater. Moreover, the number of dump resistor should be limited to avoid large terminal voltage. Therefore, in this paper, we propose a quench protection method for extracting the energy stored in a magnet by charging and discharging energy through a capacitor switching without increasing resistance. The simulation results show that the proposed system has a faster current decay within the allowable voltage level.

• 전력전자학회논문지
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• 제7권6호
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• pp.570-578
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• 2002

음극방식은 지하매설 및 해양 금속 구조물의 부식을 방지하기 위해 가장 많이 사용되고 있는 방식법이다. 기존의 음극방식용 정류기는 SCR 위상제어 정류기로 구성되어 입련단 역율이 낮으며, 부피와 무게가 큰 단점을 지니고 있다. 본 논문에서는 이러한 문제를 해결하기 위해 새로운 음극방식용 모듈타입 스위칭 정류기를 제안한다. 제안한 정류기 회로는 크게 두 부분, 즉 한 대로 구성된 AC/DC 컨버터부와 네 대로 구성된 Module Ttpe DC/DC 컨버터부로 되어 있다. AC/DC 컨버터는 IGBT PWM Rectifier로서 입력전압의 역률을 거의 1로 제어하고 있으며 또한 DC Link 전압을 일정하게 제어하고 있다. Module Type DC/DC 컨버터는 ZCS/ZVS 스위칭 동작을 통하여 스위칭 손실 감소와 함께 고주파 동작을 가능하게 하여, 입력측과 출력측의 전기적 절연을 위한 변압기로 고주파 변압기를 사용할 수 있게 하였다. 이로 인해 시스템의 부피와 무게를 현저히 감소시켰다. 본 논문에서 개발한 방식용 정류기 기술은 다른 유사 분야에의 적용도 가능할 것으로 기대된다.