• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.473-476
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• 2000

The network reliability is to be computed in terms of the terminal reliability. The computation of a termini reliability is started with a Boolean sum of products expression corresponding to simple paths of the pair of nodes. This expression is then transformed into another equivalent expression to be a Disjoint Sum of Products form. But this computaion of the terminal reliability obviously does not consider the communication between any other nodes but for the source and the sink. In this paper, we derive the overall network reliability which is the probability of communication that each node in the network communicates with all other remaining nodes. For this, we propose a method to make the SOP disjoint for deriving the network reliability expression from the system success expression using the modified Sheinman's method and modified BDD method.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.1009-1023
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• 1999

이 논문은 재귀원형군 G(2^m , 2^k ) 그래프 이론적 관점에서 고찰하고 정점이 서로소인 경로에 관한 위상 특성을 제시한다. 재귀원형군은 1 에서 제안된 다중 컴퓨터의 연결망 구조이다. 재귀원형군 {{{{G(2^m , 2^k )의 서로 다른 두 노드 v와 w를 잇는 연결도 kappa(G)개의 서로소인 경로의 길이가 두 노드 사이의 거리d(v,w)나 혹은 G(2^m , 2^k )의 지름 \dia(G)에 비해서 얼마나 늘어나는지를 고려한다. 서로소인 경로를 재귀적으로 설계하는데, 그 길이는 k ge2일 때 d(v,w)+2^k-1과 \dia(G)+2^k-1의 최솟값 이하이고, k=1일 때 d(v,w)+3과 \dia(G)\+2의 최솟값 이하이다. 이 연구는 (2^m , 2^k )의 고장 감내 라우팅, 고장 지름이나 persistence의 분석에 이용할 수 있다.Abstract In this paper, we investigate recursive circulant G(2^m , 2^k ) from the graph theory point of view and present topological properties concerned with node-disjoint paths. Recursive circulant is an interconnection structure for multicomputer networks proposed in 1 . We consider the length increments of {{{{kappa(G)disjoint paths joining arbitrary two nodes v and win G(2^m , 2^k )compared with distance d(v,w)between the two nodes and diameter {{{{\dia(G)of G(2^m , 2^k ), where kappa(G)is the connectivity of G(2^m , 2^k ). We recursively construct disjoint paths of length less than or equal to the minimum of {{{{d(v,w)+2^k-1and \dia(G)+2^k-1for kge2 and the minimum of d(v,w)+3 and \dia(G)+2for k=1. This work can be applied to fault-tolerant routing and analysis of fault diameter and persistence of G(2^m , 2^k )

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.718-720
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• 2001

본 논문에서는 하이퍼큐브보다 망 비용이 개선된 상호연결망 HCN(n,n)의 임의의 두 노드간에 노드중복하지 않는 n+1개의 병렬경로를 구성하는 방법을 제시하고, 그 결과를 통하여 HCN(n,n)의 고장지름이 dia(HCN(n,n))+4 이하임을 보인다. 이러한 병렬경로는 노드간에 메시지를 전송하는 시간을 줄일 수 있으며, HCN(n,n)의 노드 몇 개가 고장이 발생해도 통신지연시간이 발생하지 않음을 의미한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.11
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• pp.911-923
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• 2013

Multipath routing is one of challenging issues for improving the reliability of end-to-end data delivery in wireless sensor networks. Recently, a disjointedness and management of path have been studying to enhance the robustness and efficiency of the multipath routing. However, previous multipath routing protocols exploit the disjointed multipath construction method that is not to consider the wireless communication environment. In addition, if a path failures is occurred due to the node or link failures in the irregular network environment, they maintain the multipath through the simple method that to construct a new extra path. Even some of them have no a method. In order to cope with the insufficiency of path management, a hole detouring scheme, to bypass the failures area and construct the new paths, was proposed. However, it also has the problem that requires a heavy cost and a delivery suspension to the some or all paths in the hole detouring process due to the centralized and inflexible path management. Due to these limitations and problems, the previous protocols may lead to the degradation of data delivery reliability and the long delay of emergency data delivery. Thus, we propose a flexible disjoint multipath routing protocol which constructs the radio disjoint multipath by considering irregular and constrained wireless sensor networks. It also exploits a localized management based on the path priority in order to efficiently maintain the flexible disjoint multipath. We perform the simulation to evaluate the performance of the proposed method.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.176-186
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• 2007

An interconnection network can be represented as a graph where a vertex corresponds to a node and an edge corresponds to a link. The diameter of an interconnection network is the maximum length of the shortest paths between all pairs of vertices. The fault diameter of an interconnection network G is the maximum length of the shortest paths between all two fault-free vertices when there are $_k(G)-1$ or less faulty vertices, where $_k(G)$ is the connectivity of G. The fault diameter of an R-regular graph G with diameter of 3 or more and connectivity ${\tau}$ is at least diam(G)+1 where diam(G) is the diameter of G. We show that the fault diameter of a 2-dimensional $m{\times}n$ torus with $m,n{\geq}3$ is max(m,n) if m=3 or n=3; otherwise, the fault diameter is equal to its diameter plus 1. We also show that in $d({\geq}3)$-dimensional $k_1{\times}k_2{\times}{\cdots}{\times}k_d$ torus with each $k_i{\geq}3$, there are 2d mutually disjoint paths joining any two vertices such that the lengths of all these paths are at most diameter+1. The paths joining two vertices u and v are called to be mutually disjoint if the common vertices on these paths are u and v. Using these mutually disjoint paths, we show that the fault diameter of $d({\geq}3)$-dimensional $k_1{\times}k_2{\times}{\cdots}{\times}k_d$ totus with each $k_i{\geq}3$ is equal to its diameter plus 1.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1167-1169
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• 2009

Multipath routing in wireless sensor networks has been proven to provide with increased data delivery ratio, security, robustness to node and link failures, network throughput, etc. However, the energy cost for multiple routes construction and their maintenance is very high. This paper proposes a sink-initiated, node-disjoint multipath routing protocol for static wireless sensor networks that significantly minimizes the route construction messages and thereby saves the critical batter energy of sensor nodes. It also distributes the traffic load spatially over many nodes in the forwarding paths, which ensures balanced energy consumption in the network and thereby increases the network lifetime. The simulation results show that it decreases the routing overhead as well as the standard deviation of nodes' residual energies.

• The KIPS Transactions:PartC
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• v.15C no.2
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• pp.79-86
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• 2008

MANET(Mobile Ad hoc Network) is a collection of two or more nodes equipped with wireless communications and constrained by the factor of energy limitation. The running out of energy on some nodes may bring down the performance of network seriously. For solving the problems above, this paper uses completely separated Node-Disjoint multipaths from a source to a destination as many as possible. And, based on average, minimum or variance of energy values on the each multipath, the packets are distributed on paths. Generally, collecting methods for energy information can be classified into two main categories, Static and Dynamic. As the different energy values collected, the packet distribution methods are classified into six criteria, Static-Average, Static-Minimum, Static-Variance, Dynamic-Average, Dynamic-Minimum and Dynamic-Variance respectively. The performance of the packet distribution methods and that of AODV are compared by NS2 simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.173-179
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• 2008

An ad hoc network is multi-hop wireledss formed by mobile node without infrastructure. Due to the mobility of nodes in mobile ad hoc networks, the topology of network changes frequently. In this environments, multicast protocols are faced with the challenge of producing multi-hop routes and limitation of bandwidth. We compare the performance of two multicast routing protocols for mobile ad hoc networks - Serial Multiple Disjoint Tree Multicast Routing Protocol (Serial MDTMR) and Adaptive Core Multicast Routing Protocol (ACMRP). The simulator is implemented with GloMoSim.

• Journal of Information Processing Systems
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• v.12 no.1
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• pp.57-72
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• 2016

To provide effective communication in the wireless mesh network (WMN), several algorithms have been proposed. Since the possibilities of numerous failures always exist during communication, resiliency has been proven to be an important aspect for WMN to recover from these failures. In general, resiliency is the diligence of the reliability and availability in network. Several types of resiliency based routing algorithms have been proposed (i.e., Resilient Multicast, ROMER, etc.). Resilient Multicast establishes a two-node disjoint path and ROMER uses a credit-based approach to provide resiliency in the network. However, these proposed approaches have some disadvantages in terms of network throughput and network congestion. Previously, the buffer based routing (BBR) approach has been proposed to overcome these disadvantages. We proved earlier that BBR is more efficient in regards to w.r.t throughput, network performance, and reliability. In this paper, we consider the node/link failure issues and analogous performance of BBR. For these items we have proposed a resilient packet transmission (RPT) algorithm as a remedy for BBR during these types of failures. We also share the comparative performance analysis of previous approaches as compared to our proposed approach. Network throughput, network congestion, and resiliency against node/link failure are particular performance metrics that are examined over different sized WMNs.

• Journal of the Korean Operations Research and Management Science Society
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• v.16 no.2
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• pp.86-102
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• 1991

The purpose of this paper is to present a branch and bound algorithm for the hierarchical transportation network design problem in 2-level directed networks. This problem is to find the least cost of hierarchical transportation networks which consist of a primary path and a secondary path. The primary path is a simple path from a prespecified orgin node to a prespecified terminal node. All nodes must be either a transsipment node on the primary path or connected to that path via secondary arcs. This problem is formulated to a 0-1 inter programming problem with assignment and illegal subtour elimination equations as constaints. We show that the subproblem relaxing subtour elimination constraints is transformed to a linear programming problem by means of the totally unimodularity. Optimal solutions of this subproblem are polynoially obtained by the assignment algorithm and complementary slackness conditions. Therefore, the optimal value of this subproblme is used as a lower bound. When an optimal solution of the subproblem has an illegal subtour, a better disjoint rule is adopted as the branching strategy for reducing the number of branched problems. The computational comparison between the least bound rule and the depth first rule for the search strategy is given.