• Korean Journal of Hydrosciences
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• 제1권
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• pp.1-14
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• 1990

The analytical diffusion model is first formulated and its characteristics are critically reviewed. The flood events during the 1985-1986 flood seasons in the IHP Pyungchang Representative Basin are routed by this model and are compared with those routed by the kinematic wave model. The present model is proven to be an excellent means of taking the backwater effects due to lateral inflow or downstream river stage variations into consideration in channel routing of flood flows. It also requires much less effort and computing time at a desired station compared to any other reliable flood routing methods.

• Journal of Communications and Networks
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• 제18권6호
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• pp.884-891
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• 2016

The wireless mesh network (WMN) has attracted significant interests as a broadband wireless network to provide ubiquitous wireless access for broadband services. Especially with incorporating multiple orthogonal channels and multiple directional antennas into the WMN, each node can communicate with its neighbor nodes simultaneously without interference between them. However, as we allow more freedom, we need a more sophisticated algorithm to fully utilize it and developing such an algorithm is not easy in general. In this paper, we study a joint channel assignment, link scheduling, routing, and rate control problem for the WMN with multiple orthogonal channels and multiple directional antennas. This problem is inherently hard to solve, since the problem is formulated as a mixed integer nonlinear problem (MINLP). However, despite of its inherent difficulty, we develop an algorithm to solve the problem by using the generalized Benders decomposition approach [2]. The simulation results show the proposed algorithm provides the optimal solution to maximize the network utility, which is defined as the sum of utilities of all sessions.

• 물과 미래
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• 제23권3호
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• pp.385-395
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• 1990

측방유입수가 고려되는 3변수 Muskingum하도추적모형을 낙동강 수계중 왜관에서 적포교구간의 12개 홍수사상에 대하여 적용하였고, 기존 방법인 2변수 Muskingum방법의 저류상수 K와 가중계수 x에 추가된 α는 측방유입수를 고려해주는 변수이다. 3변수모형의 추적방정식은 유한차분방정식으로 표현되며, 추적상수 결정은 Matrix Inversion에 의하여 직접 계산 가능하며, 이로부터 각 홍수사상의 K x 값을 구할 수 있다. 본 연구를 실유역에 적용하여 실측치와 비교하여본 결과 비교적 잘 맞음을 알 수 있어쓰ㅇ며 K와 x값은 하도특성인자로서 홍수규모와 관계되고 측방유입인자 α는 강우 특성에 의하여 지배되는 변수로 판단되었으며 α값은 측방유입량이 클수록 값이 커지는 성향으로 나타났다.

• 대한전자공학회논문지TC
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• 제44권10호
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• pp.110-118
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• 2007

멀티 홈 무선 네트워크에서 멀티 채널의 사용은 무선노드의 채널 간섭 및 채널 경쟁을 줄임으로써 네트워크 성능을 향상시킨다. 최근 이를 위한 다양한 기법들이 제안되고 있다 특히 하이브리드 인터페이스 할당 방식을 사용하는 MCR(Multi channel routing protocol)은 간단한 채널 할당 방법을 통해 채널 간섭을 줄여주는 대표적인 라우팅 기술이다. 본 논문에서는 MCR의 링크 계층에서 사용하고 있는 채널 스위칭 알고리즘의 문제점을 지적하고 이를 개선할 수 있는 방안으로 트래픽 부하를 고려한 채널 스위칭 알고리즘인 LCS(Load-aware channel switching) 방안을 제안한다. LCS에서는 이웃 노드의 큐 상태 정보를 수집하여 네트워크 트래픽 상황을 파악하고 이를 바탕으로 최선의 채널을 선택한다. 또한 본 논문에서는 시뮬레이션과 테스트 베드 실험을 통해 LCS의 성능을 시험한다. 시험 결과 LCS를 적용한 MCR이 기존의 채널 스위칭 알고리즘 보다 향상된 성능을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.146-170
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• 2017

Joint channel assignment and routing is a well-known problem in multi-radio wireless mesh networks for which optimal configurations is required to optimize the overall throughput and fairness. However, other objectives need to be considered in order to provide a high quality service to network users when it deployed with high traffic dynamic. In this paper, we propose a re-configuration optimization model that optimizes the network throughput in addition to reducing the disruption to the mesh clients' traffic due to the re-configuration process. In this multi-objective optimization model, four objective functions are proposed to be minimized namely maximum link-channel utilization, network average contention, channel re-assignment cost, and re-routing cost. The latter two objectives focus on reducing the re-configuration overhead. This is to reduce the amount of disrupted traffic due to the channel switching and path re-routing resulted from applying the new configuration. In order to adapt to traffic dynamics in the network which might be caused by many factors i.e. users' mobility, a centralized heuristic re-configuration algorithm called State-Aware Joint Routing and Channel Assignment (SA-JRCA) is proposed in this research based on our re-configuration model. The proposed algorithm re-assigns channels to radios and re-configures flows' routes with aim of achieving a tradeoff between maximizing the network throughput and minimizing the re-configuration overhead. The ns-2 simulator is used as simulation tool and various metrics are evaluated. These metrics include channel-link utilization, channel re-assignment cost, re-routing cost, throughput, and delay. Simulation results show the good performance of SA-JRCA in term of packet delivery ratio, aggregated throughput and re-configuration overhead. It also shows higher stability to the traffic variation in comparison with other compared algorithms which suffer from performance degradation when high traffic dynamics is applied.

• 한국정보과학회논문지:정보통신
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• 제34권5호
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• pp.396-404
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• 2007

본 논문에서는 다수의 라디오와 채널을 사용하는 무선 애드혹 통신망에서 대역폭 측정을 기반으로 호 접속 제어와 연동되는 애드혹 라우팅 프로토콜을 제안한다. 단일 라디오에 단일 채널을 사용하는 기존 애드혹 노드와 달리 제안한 MCQosR(Multiple Channel Quality of Service Routing) 프로토콜에서는 각 노드가 다수의 채널과 라디오를 사용하여 노드사이에 전이중 통신을 가능하게 하고 경로의 내부 간섭을 감소시켰다. 또한 각 노드마다 수신전용의 고정된 채널을 갖도록 하였으며, 대역폭 측정을 기반으로 새로운 호에 대한 수락제어를 수행함으로써 QoS 제공을 가능하도록 하였다 제안된 프로토콜은 시뮬레이션을 통하여 성능을 검증하였다.

• 한국콘텐츠학회논문지
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• 제11권1호
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• pp.404-410
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• 2011

1차원 개수로 부정류의 수치 해석을 위하여 Taylor-Galerkin 기법의 유한요소법을 St. Venant 방정식의 차분에 적용하였다. 단일 수로에서 수문의 닫힘에 의한 배수문제와 3개 이상 하도가 만나는 합류점을 포함하는 수지상(dendritic) 하천 네트워크에 적용하고 그 결과를 기존에 제시된 유한차분법, 유한요소법 등의 수치기법과 비교하였으며 매우 잘 일치함을 확인하였다. 본 연구에서 적용한 기법은 연속방정식과 운동량방정식을 순차적으로 해석해 나가기 때문에 적용이 간편하며, 최종적으로 삼대각 행렬과 합류점의 적합조건을 위한 최소한의 요소를 포함하기 때문에 삼대각 행렬의 연산 방법을 적용할 수 있어 계산 측면에서 빠르고 안정적이다. 또한, 행렬의 저장을 위한 메모리 측면에서 경제적이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5149-5173
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• 2016

Cooperative forwarding has shown a substantial network performance improvement compared to traditional routing in multi-hop wireless network. To further enhance the system throughput, especially in the presence of highly congested multiple cross traffic flows, a promising way is to incorporate the multi-radio multi-channel (MRMC) capability into cooperative forwarding. However, it requires to jointly address multiple issues. These include radio-channel assignment, routing metric computation, candidate relay set selection, candidate relay prioritization, data broadcasting over multi-radio multi-channel, and best relay selection using a coordination scheme. In this paper, we propose a simple and efficient cluster-based cooperative data forwarding (CCDF) which jointly addresses all these issues. We study the performance impact when the same candidate relay set is being used for multiple cross traffic flows in the network. The network simulation shows that the CCDF with MRMC not only retains the advantage of receiver diversity in cooperative forwarding but also minimizes the interference, which therefore further enhances the system throughput for the network with multiple cross traffic flows.

• 대한전자공학회논문지
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• 제23권4호
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• pp.550-556
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• 1986

This paper proposes a two-layer channel routing algorithm using the division of signal nets in LSI/VLSI layout design. To solve the vertical constraint problem, the doglegging method is used. Although signal net division and the dogleg are used, the routing is accomplished within local channel density and the increase in vias is repressed by assining the vertical segments to the metal layer and the horizontal segments to the poly layer. The algorithm was implemented on a VAX 11/780 computer. The effectiveness of the proposed algorithm is proved by appling this algorithm to Deutch's difficult example.

• Korean Journal of Hydrosciences
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• 제8권
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• pp.41-56
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• 1997

A new routing computer model for the symmetric compound channel called the ASRMCS(Apparent Shear Force Muskingum-Cunge Method in Symmetry) has been developed. The Muskingum-Cunge routing method is adapted. The Apparent Shear Force (ASF) between the deep main channel and the shallow floodplan flow is introduced while the flow is routed. The nonlinear parameter method is applied. The temporal and spatial increments are varied according to the flow rate. The adaptation of above schemes is tested against the routed hydrographs using the DAMBRK model. The results of general routing practice of Muskingum-Cunge Method(GPMC) are also compared with those of above two models. The results of the new model match remarkably well with those of DAMBRK. The routed hydrographs show a smooth variation from the inflow boundary condition without any distortions caused by the difference of cross-section shape. However, the results of GPMC, showing early rise and fall of routed hydrograph, have considerable differences from those of the ASFMCS and DAMBRK.