• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.4
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• pp.21-29
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• 2003

The traffic scheduling problem for a satellite cluster with an arbitrary number of satellites is considered. which is one of the most interesting problems in the satellite communication scheduling area. This problem is to find a time slot assignment maximizing the transponder utilization for a satellite cluster This problem is known to be NP-complete, and several heuristic algorithms have been proposed. In this paper, we suggest new efficient algorithms for this problem, which have less time complexity than the best existing one and provide much better solution quality. Extensive simulation results are reported.

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.3
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• pp.63-74
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• 1996

Ordering plays an important role in solving an LP problem with sparse matrix by the interior point method. Since ordering is NP-complete, we try to find an efficient method. The objective of this paper is to present an efficient heuristic ordering method for implementation of the minimum deficiency method. Both the ordering method and the data structure play important roles in implementation. First we define a new heuristic pseudo-deficiency ordering method and a data structure for the method-quotient graph and cliqued storage. Next we show an experimental result in terms of time and nonzero numbers by NETLIB problems.

• The KIPS Transactions:PartC
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• v.8C no.4
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• pp.479-488
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• 2001

디지털 오디오나 비디오와 같은 멀티미디어 트래픽 QoS 제약 조건(종단간 지연, 대역폭 가용성, 패킷 분실률, 지터 등)을 요구하고 있다. 이러한 멀티미디어 트래픽의 제약 조건을 보장하기 위해서는 데이터 전송을 하기 전에 실시간 채널을 설정할 필요가 있으며 그러한 채널의 설정은 QoS 제약 조건을 고려한 효율적인 경로 설정 알고리즘을 필요로 한다. 일반적으로 네트워크에서 지연 제약 조건과 최소 비용을 만족하는 경로를 찾는 것은 NP-complete임이 증명되었다. 따라서 본 논문에서는 간단하고 분산된 루프 프리 라우팅 알고리즘(Loop-free Delay-constrained Routing algorithm with Load balancing : DRL)을 제안한다. 제안한 DRL은 지연 제약 조건을 만족하는 경로를 선택하며 네트워크의 상태에 따라 부하를 분산시키는 기능을 갖고 있다. 또한 지연 제약 라우팅을 위해 각 노드에서는 한정된 네트워크 상태 정보만을 필요로 한다. 시뮬레이션 결과는 DRL이 LDP와 마찬가지로 지연 제약조건을 만족하는 경로를 제공하면서 DCUR에 비해 루프가 발생하지 않는 경로 설정을 수행한다는 것을 보여주고 있다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.8
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• pp.1-10
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• 1993

In this paper, we will propose 4-move ZKIP and its application. Using bit-commitment scheme that is necessary to organize the ZKIP related to NP-Complete problem and WH and WI preserving the property for security under parallel composition of protocols, we will show that the proposed ZKIP is 4-move ZKIP of SAT comparing to 6-move ZKIP of SAT proposed by Brassard. Chaum and Yung, and under claw-free pairs of function the proposed ZKIP is also 4-move ZKIP comparing to 5-move ZKIP proposed by Goldreich and Krawczyk under the same assumption. Moreover we will show the efficiency of the proposed scheme better than Fiat and Shamir's scheme at the points of computational complexity and communication complexity, and also propose the efficient and secure identification scheme against the chosen ciphertext attack, using the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.2196-2218
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• 2017

Multicast communication has been widely used in the Internet. However, multicast communication is vulnerable to DoS attack due to static router configuration. In this paper, HMC, a hopping multicast communication method based on SDN, is proposed to tackle this problem. HMC changes the multicast tree periodically and makes it difficult for the attackers to launch an accurate attack. It also decreases the probability of multicast communication being attacked by DoS and in the meanwhile, the QoS constrains are not violated. In this research, the routing problem of HMC is proven to be NP-complete and a heuristic algorithm is proposed to solve it. Experiments show that HMC has the ability to resist DoS attack on multicast route effectively. Theoretically, the multicast compromised probability can drop more than 0.6 when HMC is adopt. In addition, experiments demonstrate that HMC achieves shorter average multicast delay and better robustness compared with traditional method, and more importantly, it better defends DoS attack.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.12 no.1
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• pp.20-28
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• 2012

We define a language $\mathcal{RS}$, a subclass of the scheduling language $\mathcal{RS}V$ (resource constrained project scheduling with variant processes). $\mathcal{RS}$ involves the determination of the starting times for ground activities of a project satisfying precedence and resource constraints, in order to minimize the total project duration. In $\mathcal{RS}$ ground activities and two structural symbols (operators) 'seq' and 'pll' are used to construct activity-terms representing scheduling problems. We consider three different variants for formalizing the $\mathcal{RS}$-scheduling problem, the optimizing variant, the number variant and the decision variant. Using the decision variant we show that the problem $\mathcal{RS}$ is $\mathcal{NP}$-complete. Further we show that the optimizing variant (or number variant) of the $\mathcal{RS}$-problem is computable in polynomial time iff the decision variant is computable in polynomial time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.535-539
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• 1998

오늘날 멀티미디어 응용들은 다양하고 세분화된 QoS 지원을 요구하는데, 이와 같이 만족시켜야 할 QoS 파라미터의 수가 둘 이상이 되는 경우 라우팅 문제는 NP-complete하다고 말하며, 이러한 문제는 휴리스틱 알고리즘을 통해 해결된다. 본 논문에서는 ATM Forum에서 정의한 다섯 가지 서비스 유형 별로 연관된 서비스 품질 파라미터를 분류하고, 서비스 유형별로 독립된 경로 선택 기준 및 경로 계산 알고리즘을 적용하여 호 설정 시간 및 호 차단율을 낮출 수 있는 휴리스틱 알고리즘을 제안한다. 또한 임의의 망 모델 환경에서 CBR 서비스 유형에 대해 제안된 알고리즘을 시뮬레이션하여 성능 분석을 수행한다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.1056-1064
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• 2003

The Euclidean steiner tree problem (ESTP) is to find a minimum-length euclidean interconnection of a set of points in the plane. It is well known that the solution to this problem will be the minimal spanning tree (MST) on some set steiner points, and the ESTP is NP-complete. The ESTP has received a lot of attention in the literature, and heuristic and optimal algorithms have been proposed. In real field, heuristic algorithms for ESTP are popular. A key performance measure of the algorithm for the ESTP is the reduction rate that is achieved by the difference between the objective value of the ESTP and that of the MST without steiner points. In recent survey for ESTP, the best heuristic algorithm showed around $3.14\%$ reduction in the performance measure. We present a evolution programming (EP) for ESTP based upon the Prim algorithm for the MST problem. The computational results show that the EP can generate better results than already known heuristic algorithms.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.1065-1070
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• 2003

Facility Layout Planning is concerned with how to arrange facilities necessary for production in a given space. Its objective is often to minimize the total sum of all material flows multiplied by the distance among facilities. FLP belongs to NP complete problem; i.e., the number of possible layout solutions increases with the increase of the number of facilities. Thus, meta heuristics such as Genetic Algorithm (GA) and Simulated Annealing have been investigated to solve the FLP problems. However, one of the biggest problems which lie in the existing meta heuristics including GA is hard to find an appropriate combinations of parameters which result in optimal solutions for the specific problem. The Ant System algorithm with elitist and ranking strategies is used to solve the FLP problem as an another good alternative. Experimental results show that the AS algorithm is able to produce the same level of solution quality with less sensitive parameters selection comparing to the ones obtained by applying other existing meta heuristic algorithms.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.433-440
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• 2003

통신시스템의 발전과 더불어 WDM 전송기술의 등장은 미래의 다양한 광대역 서비스의 제공이 가능하게 되었다. 하지만, 개별 수요들이 요구하는 대역폭이 광파장의 대역폭에 비해 매우 작으므로. 개별 수요들을 다중화하여 하나의 광경로를 통해 전송하는 수요집적(traffic grooming)에 관한 연구들이 많은 관심을 받고. 있다 본 연구는 mesh 구조의 WDM 통신망에서의 수요집적 및 광경로 설정에 관한 문제를 다루고 있다. 주어진 네트워크 상에 하나의 가상노드와 아크를 추가하여 새로운 네트워크를 구성하고 이를 대상으로 목적함수를 사용되는 광파장의 수를 최소화하는 혼합정수계획 모형을 수립하였다. 아울러. NP-Complete로 알려진 본 문제의 해를 효과적으로 구하기 위한 발견적 해법을 제안하며, 실제 다양한 실험을 통해 제안된 알고리즘의 효율성을 보인다.