• ETRI Journal
• /
• v.40 no.5
• /
• pp.613-623
• /
• 2018

The instability of operational channels on cognitive radio networks (CRNs), which is due to the stochastic behavior of primary users (PUs), has increased the complexity of the design of the optimal routing criterion (ORC) in CRNs. The exploitation of available opportunities in CRNs, such as the channel diversity, as well as alternative routes provided by the intermediate nodes belonging to routes (internal backup routes) in the route-cost (or weight) determination, complicate the ORC design. In this paper, to cover the channel diversity, the CRN is modeled as a multigraph in which the weight of each edge is determined according to the behavior of PU senders and the protection of PU receivers. Then, an ORC for CRNs, which is referred to as the stability probability of communication between the source node and the destination node (SPC_SD), is proposed. SPC_SD, which is based on the obtained model, internal backup routes, and probability theory, calculates the precise probability of communication stability between the source and destination. The performance evaluation is conducted using simulations, and the results show that the end-to-end performance improved significantly.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.8 s.350
• /
• pp.47-58
• /
• 2006

Due to the movement of nodes, ad-hoc networks suffer from the problems such as the decrease of data delivery ratio, the increase of end-to-end delay, and the increase of routing overhead. The backup routing schemes try to solve these problems by finding the backup routes during the route discovery phase and using them when a route fails. Generally the backup routing schemes outperform the single-path routing schemes in terms of data delivery ratio, end-to-end delay, and routing overhead when the nodes move rapidly. But when the nodes don't move rapidly, the backup routing schemes generate more routing traffics than the single-path routing schemes because they need to exchange packets to find the backup route. In addition, when the backup route fails earlier than the main route, it can not use the backup route because in many backup route algorithms, the backup route is found only at the initial route discovery phase. RBR(Reactive Backup Routing Algorithm) proposed in this paper is an algorithm that provides more stable data delivery than the previous backup routing schemes through the selective maintenance of backup route and the backup route rediscovery. To do that RBR prioritize the backup routes, and maintain and use them selectively Thus it can also decrease the routing overheads. Also, RBR can increase data delivery ratio and decrease delay because it reestablishes the backup route when the network topology changes. For the performance evaluation, OPNET simulator is used to compare RBR with the single-path routing scheme and some of the well known backup routing schemes.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.79-82
• /
• 2002

The addition of switches to a distribution feeder does, in general, increase reliability by decreasing the duration of the outage of many to the customers on the feeder. To cover its service area so that feeder-level delivery reaches sufficiently close to all customers, feeders typically split their routes many times, in what is often called a lateral feeder. It is interesting to note, however, that the effectiveness of a switch is very much dependent on the types of lateral feeder. The types of lateral are classified into two types. The first is loop lateral feeder that can connect its load to an adjacent feeder through a tie line in case that a fault occurs in its feeder and it is laid out so that every feeder has complete fault backup through re-switching of its loads to other sources like a main feeder. The second is the radial lateral feeder cannot connect its load to an adjacent line, no provision is made for contingency backup of feeders. There are no other circuits in the radial lateral feeder form which to restore power. In this study, we evaluate the effectiveness of a switch installation between on the radial and loop lateral feeders to increase reliability by decreasing the duration of the outage. These results can help power utility to design the switch layouts on the radial and loop lateral feeder system.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.51 no.9
• /
• pp.433-440
• /
• 2002

The addition of switches to a distribution feeder does, in general, increase reliability by decreasing the duration of the outage of many to the customers on the feeder. To cover its service area so that feeder-level delivery reaches sufficiently close to all customers, feeders typically split their routes many times, in what is often called a lateral feeder. It is interesting to note, however, that the effectiveness of a switch is very much dependent on the types of lateral feeder. The types of lateral are classified into two types. The first is loop lateral feeder that can connect its load to an adjacent feeder through a tie line in case that a fault occurs in its feeder and it is laid out so that every feeder has complete fault backup through re-switching of its loads to other sources like a main feeder The second is the radial lateral feeder cannot connect its load to an adjacent line, no provision is made for contingency backup of feeders. There are no other circuits in the radial lateral feeder form which to restore power. In this study, we evaluate the effectiveness of a switch installation between on the radial and loop lateral feeders to increase reliability by decreasing the duration of the outage. These results can help power utility to design the switch layouts on the radial and loop lateral feeder system.

• Journal of Korea Society of Industrial Information Systems
• /
• v.26 no.3
• /
• pp.9-22
• /
• 2021

This study proposes a supply chain network (SCN) model considering supply disruption in assembly industry. For supply disruption, supplier disruption and its route disruption are simultaneously taken into consideration in the SCN model. With the simultaneous consideration, the SCN model can achieve its flexibility and efficiency. A mathematical formulation is suggested for representing the SCN model, and a proposed hybrid genetic algorithm (pro-HGA) is used for implementing the mathematical formulation. In numerical experiment, the performance of the pro-HGA approach is compared with those of some conventional approaches using the SCN models with various scales, and a sensitivity analysis considering the change of the numbers of suppliers and backup routes is done. Experimental results show that the performances of the pro-HGA approach are superior to those of the conventional approaches, and the flexibility and efficiency of the SCN model considering supply disruption are proved. Finally, the significance of this study is summarized and a potential future research direction is mentioned in conclusion.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.11
• /
• pp.2067-2072
• /
• 2016

Recently, due to the development of attack techniques that can circumvent existing information protection systems, continuous threats in a form unrecognized by the user have threatened information assets. Therefore, it is necessary to support the prompt responses to anticipated attempts of APT attacks, bypass access attacks, and encryption packet attacks, which the existing systems have difficulty defending against through a single response, and to continuously monitor information protection systems with a defense strategy based on Indicators of Attack (IOA). In this paper, I suggest a centralized intelligent information protection system to support the intelligent response to a violation by discerning important assets through prevention control in a performance impact assessment about information properties in order to block the attack routes of APT; establishing information control policies through weakness/risk analyses in order to remove the risks in advance; establishing detection control by restricting interior/exterior bypass networks to server access and monitoring encrypted communications; and lastly, performing related corrective control through backup/restoration.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.4
• /
• pp.1911-1930
• /
• 2017

Overlay routing has emerged as a promising approach to improve reliability and efficiency of the Internet. The key to overlay routing is the placement and maintenance of the overlay infrastructure, especially, the selection and placement of key relay nodes. Spurred by the observation that a few relay nodes with high betweenness centrality can provide more optimal routes for a large number of node pairs, we propose a resilient routing overlay network construction method by introducing Super-Relay nodes. In detail, we present the K-Minimum Spanning Tree with Super-Relay nodes algorithm (SR-KMST), in which we focus on the selection and connection of Super-Relay nodes to optimize the routing quality in a resilient and scalable manner. For the simultaneous path failures between the default physical path and the overlay backup path, we also address the selection of recovery path. The objective is to select a proper one-hop recovery path with minimum cost in path probing and measurement. Simulations based on a real ISP network and a synthetic Internet topology show that our approach can provide high-quality overlay routing service, while achieving good robustness.

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

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.45 no.3
• /
• pp.165-176
• /
• 2009

The process of berthing/deberthing operations for entering/leaving vessels in Busan northern harbor was analyzed and evaluated by using an integrated VTS(vessel traffic service) system installed in the ship training center of Pukyong National University, Busan, Korea. The integrated VTS system used in this study was consisted of ARPA radar, ECDIS(electronic chart display and information system), backup(recording) system, CCTV(closed-circuit television) camera system, gyro-compass, differential GPS receiver, anemometer, AIS(automatic identification system), VHF(very high frequency) communication system, etc. The network of these systems was designed to communicate with each other automatically and to exchange the critical information about the course, speed, position and intended routes of other traffic vessels in the navigational channel and Busan northern harbor. To evaluate quantitatively the overall dynamic situation such as maneuvering motions for target vessel and its tugboats while in transit to and from the berth structure inside a harbor, all traffic information in Busan northern harbor was automatically acquired, displayed, evaluated and recorded. The results obtained in this study suggest that the real-time tracking information of traffic vessels acquired by using an integrated VTS system can be used as a useful reference data in evaluating and analyzing exactly the dynamic situation such as the collision between ship and berth structure, in the process of berthing/deberthing operations for entering/leaving vessels in the confined waters and harbor.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.7
• /
• pp.1541-1548
• /
• 2012

This paper proposes a new multipath-based routing protocol on MANETs with Fast-Recovery of failures. The proposed protocol establishes the primary and secondary paths between a source and a destination considering the end-to-end packet reception reliability of routes. The primary path is used to transmit messages, and the secondary path is used to recover the path when detecting failures on the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to recover locally the route failure, the proposed protocol can reduce the number of packet loss and the amount of control packets for setting up new paths. The simulation result using QualNet simulator shows that the proposed protocol was about 10-20% higher than other protocols in terms of end-to-end message delivery ratio and the fault recovery time in case of link fault was about 3 times faster than the other protocols.