• 전자공학회논문지A
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• 제32A권2호
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• pp.130-139
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• 1995

A hierarchical placement system based on routing region assignment has been developed to increase the probability of routing completion after placement. While most of the existing placement systems attempt to reduce the cell density at the portions where routing density is high, our method is distinguished in that specific routing regions are allocated to secure complete routing where the routing density is greater than the routing capacity. Hierarchy is vuilt by clustering and recursive paritioning, and the initial placement obtained by partitioning at each level is improved by using the region refinement algorithm. After placement at each hierarchical level, global routing is performed and fouting regions are assigned, if routing density is greater than routing capacity, to be considered at the next level of placement. the proposed algorithm has been implemented and applied to place several industrical gate-array circuits. A couple of circuits which cannot be routed by using conventional placement techniques can be completely routed by using our new placement technique with routing region assignment.

• Journal of Communications and Networks
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• 제12권3호
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• pp.246-252
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• 2010

A binary linear integer program is formulated for the problem of expanding the capacity of a fiber optic network and routing the traffic to deliver new interactive multimedia services. A two-phase Lagrangian dual search procedure and a Lagrangian heuristic are developed. Computational results show superior performance of the two-phase subgradient optimization compared with the conventional one-phase approach.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2362-2378
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• 2017

To mitigate the performance degradation caused by performance anomaly, a number of channel assignment algorithms have been proposed for multi-rate wireless mesh networks. However, network conditions have not been fully considered for routing process in these algorithms. In this paper, a joint scheme called Multi-rate Dijkstra's Shortest path - Rate Separated (MDSRS) is proposed, combining routing metrics and channel assignment algorithm. In MDSRS, the routing metric are determined through the synthesized deliberations of link costs and rate matches; then the rate separated channel assignment is operated based on the determined routing metric. In this way, the competitions between high and low rate links are avoided, and performance anomaly problem is settled, and the network capacity is efficiently improved. Theoretical analysis and NS-3 simulation results indicate that, the proposed MDSRS can significantly improve the network throughput, and decrease the average end-to-end delay as well as packet loss probability. Performance improvements could be achieved even in the heavy load network conditions.

• ETRI Journal
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• 제21권4호
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• pp.9-22
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• 1999

This paper considers a problem of configuring both physical backbone and logical virtual path (VP) networks in a reconfigurable asynchronous transfer mode (ATM) network where links are subject to failures. The objective is to determine jointly the VP assignment, the capacity assignment of physical links and the bandwidth allocation of VPs, and the routing assignment of traffic demand at least cost. The network cost includes backbone link capacity expansion cost and penalty cost for not satisfying the maximum throughput of the traffic due to link failures or insufficient link capacities. The problem is formulated as a zero-one non-linear mixed integer programming problem, for which an effective solution procedure is developed by using a Lagrangean relaxation technique for finding a lower bound and a heuristic method exploited for improving the upper bound of any intermediate solution. The solution procedure is tested for its effectiveness with various numerical examples.

• 경영과학
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• 제10권1호
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• pp.207-216
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• 1993

The purpose of this paper is to develop a branch and bound algorithm for the transportation problem with a limited number of company owned vehicles. First, we find an initial solution by solving quasi-assignment subproblem induced by relaxing constraints of the vehicle capacity and illegal tours elimination equations. Second, we build routing from the assignment, and if there is a routings which violates relaxed constraints, we introduce branches of the subproblem in order to remove it. After all branches are searched, we get the optimal solution.

• Journal of Communications and Networks
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• 제9권4호
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• pp.368-376
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• 2007

The large potential bandwidth available in wavelength-division multiplexed optical networks makes this technology of crucial importance for satisfying the ever increasing capacity requirements of the next-generation Internet. In this scenario, the routing and wavelength assignment(RWA) problem that concerns determining the optical paths and wavelengths to be used for connection establishment in a wavelength-routed network, is still one of the most important open issues. In this paper we propose a new online dynamic grooming-capable RWA heuristic scheme working on wavelength division multiplexing(WDM) networks as a multistage selection process. The proposed algorithm is transparent with respect to the presence of wavelength converters, achieves very low connection rejection ratios with minimal computational complexity and is appropriate for the modern multilayer optical circuit and wavelength switched networks with sparse wavelength conversion capability.

• 대한산업공학회지
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• 제39권6호
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• pp.554-561
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• 2013

As a special topic of the vehicle routing problems (VRP), VRPSDP extends the vehicle routing problem as considering simultaneous pickup and delivery for goods. The past studies have mainly dealt with a only weight constraint of a loading capacity for heterogeneous products. However. this study suggests VRPSDP considering separate loading area according to characteristics of loading species. The objective is to design a set of minimum distance routes for the vehicle routing assignment with independent capacity for heterogeneous species. And then we present a another HVRPSDP model which is easy to utilizes in a unique circumstance that is a guarantee of executing a task simultaneously from the various areas under restricted time and raising an application of vehicles that returns at the depot for the next mission like the military group. The optimal results of the suggested mathematical models are solved by the ILOG CPLEX software ver. 12.4 that is provided by IBM company.

• 한국정보과학회논문지:정보통신
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• 제37권5호
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• pp.374-385
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• 2010

최근 유선 네트워크의 설치가 어려운 먼 거리의 인터넷 접속을 낮은 비용으로 가능하게 해주는 기술인 무선 메쉬 네트워크에 대한 관심이 증가하고 있다. 무선 메쉬 네트워크의 각 노드는 데이터를 송수신하는 호스트의 역할 뿐만 아니라 데이터를 전달하는 라우터의 역할도 수행한다. 이 때 메쉬 라우터는 기존 유선 망 또는 다른 무선 통신망으로의 연결을 제공하는 게이트웨이의 역할을 함으로써 무선 네트워크에서의 백본으로 동작할 수도 있다. 무선 메쉬 네트워크에서 멀티 채널 멀티 인터페이스를 사용하는 것은, 서로 간섭하지 않는 채널을 사용하여 동시에 통신이 가능함으로써 천체 네트워크의 데이터 처리량을 높이게 된다. 이러한 멀티 채널 멀티 인터페이스 무선 메쉬 네트워크에서 각 인터페이스에 채널들을 할당하고 라우팅을 결정하는 것은 중요한 연구 과제이다. 따라서 멀티 채널 멀티 인터페이스를 지원하는 무선 메쉬 네트워크에서의 채널 할당 및 라우팅의 목적은 네트워크의 연결성을 유지하면서 간섭을 최소화하며 네트워크의 데이터 처리량을 향상시키는 것이다. 본 논문에서는 멀티 채널 멀티 인터페이스 무선 메쉬 네트워크에서 네트워크의 전체 데이터 처리량을 높이며, 평균 종단간 지연시간을 줄이는 중앙 집중적이며 휴리스틱한 방법의 채널 할당 및 라우팅 알고리즘들을 제안한다. 이를 위해 링크의 잔여 채널 용량을 고려한 라우팅 방법과 링크의 통신 참여 수를 고려한 채널 할당 및 라우팅 방법, 그리고 우회 경로를 허용하는 라우팅 방법을 제안한다. 마지막으로 본 논문에서 제안한 방법의 성능을 평가하기 위해 NS-2 시뮬레이터를 사용하여 기존 관련 연구와 비교 분석하였다. 제안한 방법은 기종 관련 연구에서의 방법보다 우선 메쉬 네트워크에서의 평균 데이터 처리량을 증가시키며 평균 종단간 지연시간을 감소시키는 결과를 보임으로써 전체 네트워크의 성능이 향상됨을 확인할 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3955-3966
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• 2014

With the exponentially increasing Internet traffic and emergence of more versatile and heterogeneous applications, the design of datacenter networks (DCNs) is subject to unprecedented requirements for larger capacity and more flexible switching granularities. Envisioning Optical-Orthogonal Frequency Division Multiplexing (O-OFDM) as a promising candidate for such a scenario, we motivate the use of O-OFDM as the underlying switching technology in order to provide sufficient switching capacity and elastic bandwidth allocation. For this purpose, this article reviews the recent progresses of DCN deployment and assesses the scenario where the O-OFDM transmission and switching technology is employed in the underlying transport plane. We discuss the key issues of the datacenter-oriented O-OFDM optical networks, and in particular, elaborate on a number of open issues and solutions including system interconnection architecture, routing and resource assignment, survivability, and energy-efficiency.

• 한국정보과학회논문지:정보통신
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• 제36권4호
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• pp.286-296
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• 2009

고밀도 파장 분할 다중화 방식(DWDM: Dense-Wavelength Division Multiplexing) 기반 차세대 광 인터넷 백본망(NGOI: Next Generation Optical Internet)의 주요 연구주제 중 하나는 다양한 멀티미디어 응용 서비스들의 서비스 품질(QoS: Quality-of-Service)을 고려한 멀티캐스트 서비스용 효율적인 라우팅 및 파장할당(RWA: Routing and Wavelength Assignment) 문제이다. 특히, 차세대 광 인터넷 백본망에서 망 대역폭의 효율적인 사용 측면의 RWA 문제는 매우 중요한 요소이다. 그러나 기존의 RWA 알고리즘들은 멀티캐스트 트리 형성 시 발생하는 혼잡상황과 경로에 대한 우선순위를 고려하지 않아 성능이 매우 제한적이다. 따라서 본 논문에서는 이러한 문제를 해결하기 위한 방안으로 멀티캐스트 트리 형성시 발생하는 혼잡경로를 피하고 노드의 우선순위를 고려하는 효율적인 우선순위기반 최소간섭 경로 멀티캐스트 라우팅(PMIPMR - Priority-based Minimum Interference Path Multicast Routing) 알고리즘을 제안한다. 제안된 알고리즘은 시뮬레이션 결과를 통해 파장 사용률과, 파장 채널 사용률 측면에서 기존의 알고리즘과 비교, 제안된 알고리즘의 효율성을 검증한다.