• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권5호
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• pp.527-547
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• 2009

Moving object management is widely used in traffic, logistic and data mining applications in ubiquitous environments. It is required to analyze spatio-temporal data and trajectories for moving object management. In this paper, we proposed a novel index structure for spatio-temporal aggregation of trajectory in a constrained network, named aCN-RB-tree. It manages aggregation values of trajectories using a constraint network-based index and it also supports direction of trajectory. An aCN-RB-tree consists of an aR-tree in its center and an extended B-tree. In this structure, an aR-tree is similar to a Min/Max R-tree, which stores the child nodes' max aggregation value in the parent node. Also, the proposed index structure is based on a constrained network structure such as a FNR-tree, so that it can decrease the dead space of index nodes. Each leaf node of an aR-tree has an extended B-tree which can store timestamp-based aggregation values. As it considers the direction of trajectory, the extended B-tree has a structure with direction. So this kind of aCN-RB-tree index can support efficient search for trajectory and traffic zone. The aCN-RB-tree can find a moving object trajectory in a given time interval efficiently. It can support traffic management systems and mining systems in ubiquitous environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권9호
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• pp.3138-3150
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• 2021

Multimedia services on the Internet are continuously increasing. Accordingly, the demand for a technology for efficiently delivering multimedia traffic is also constantly increasing. The multicast technique, that delivers the same content to several destinations, is constantly being developed. This technique delivers a content from a source to all destinations through the multicast tree. The multicast tree with low cost increases the utilization of network resources. However, the finding of the optimal multicast tree that has the minimum link costs is very difficult and its calculation complexity is the same as the complexity of the Steiner tree calculation which is NP-complete. Therefore, we need an effective way to obtain a multicast tree with low cost and less calculation time on SDN-based smart network platforms. In this paper, we propose a new multicast tree generation algorithm which produces a multicast tree using an agent trained by model-based meta reinforcement learning. Experiments verified that the proposed algorithm generated multicast trees in less time compared with existing approximation algorithms. It produced multicast trees with low cost in a dynamic network environment compared with the previous DQN-based algorithm.

• 한국통신학회논문지
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• 제33권1A호
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• pp.24-35
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• 2008

이동 애드혹 네트워크에 Mobile IP를 효율적으로 지원하기 위하여 인프라구조 네트워크와 이동 애드혹 네트워크의 트리 기반 통합 네트워크 구조를 제안하고, 통합 네트워크의 형성 및 관리를 위한 네트워크 구조 관리 프로토콜 및 통합 네트워크에 특화된 트리 기반 라우팅 프로토콜을 제안한다. 통합 네트워크는 두 이기종 네트워크를 연결하는 고정 인터넷 게이트웨이(IG)를 가지고 있으며, 이동 노드들은 IG와 직접 통신 거리에 있는 이동 노드들을 중심으로 작은 트리들을 형성한다. 새로운 노드는 먼저 임의의 트리에 가입하고 트리를 따라 자신의 흠 에이젼트(HA) 및 외부 에이젼트(FA)에 등록한다. 또한, 제안하는 라우팅 프로토콜은 트리 정보를 이용하여 효율적으로 경로를 설정한다. 주요 네트워크 전개 시나리오에 대한 시뮬레이션을 통해서 트리 기반 통합 네트워크의 효율성을 분석하였으며, 제안하는 라우팅 프로토콜을 기존의 Mobile IP 지원 AODV 프로토콜과 성능을 비교 분석하였다.

• 한국통신학회논문지
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• 제34권12B호
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• pp.1498-1505
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• 2009

In centralized control sensor network, tree-based multi-channel communication overcomes the recurrent channel switching and makes possible to transfer data simultaneously from different sources. In our paper, we propose a greedy algorithm named as NIT (Non-Intersecting Tree) that the trees can avoid inter-tree interference. We also propose channel switching technique by which trees can avoid link failure or area blocking due to external interference locally without rerunningthe algorithm and without interrupting the whole network. At first we applied our algorithm for a random topology and then we evaluate the performance of the network using NS-2 simulator. The results show that with the increasing of channel the throughputand delivery ratio are increased significantly. We got better performance than a using a recent proposed Tree-based Multi-Channel Protocol (TMCP).

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.637-647
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• 2018

In this paper, we propose a method to search candidates of network reconfiguration to restore distribution system with distributed energy resources using a level-based tree search algorithm. First, we introduce a method of expressing distribution network with distributed energy resources for fault restoration, and to represent the distribution network into a simplified graph. Second, we explain the tree search algorithm, and introduce a method of performing the tree search on the basis of search levels, which we call a level-based tree search in this paper. Then, we propose a candidate search method for fault restoration, and explain it using an example. Finally, we verify the proposed method using computer simulations.

• 산업경영시스템학회지
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• 제35권1호
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• pp.10-15
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• 2012

This paper considers an economic design problem of a tree-based network which is a kind of computer network. This problem can be modeling to be an objective function to minimize installation costs, on the constraints of spanning tree and maximum traffic capacity of sub tree. This problem is known to be NP-hard. To efficiently solve the problem, a tabu list coupled genetic algorithm approach is proposed. Two illustrative examples are used to explain and test the proposed approach. Experimental results show evidence that the proposed approach performs more efficiently for finding a good solution or near optimal solution in comparison with a genetic algorithm approach.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권4호
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• pp.1223-1247
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• 2012

The need for securing Wireless Sensor Networks (WSNs) is essential especially in mission critical fields such as military and medical applications. Security techniques that are used to secure any network depend on the security requirements that should be achieved to protect the network from different types of attacks. Furthermore, the characteristics of wireless networks should be taken into consideration when applying security techniques to these networks. In this paper, energy efficient Security Model for Tree-based Routing protocols (SMTR) is proposed. In SMTR, different attacks that could face any tree-based routing protocol in WSNs are studied to design a security reference model that achieves authentication and data integrity using either Message Authentication Code (MAC) or Digital Signature (DS) techniques. The SMTR communication and processing costs are mathematically analyzed. Moreover, SMTR evaluation is performed by firstly, evaluating several MAC and DS techniques by applying them to tree-based routing protocol and assess their efficiency in terms of their power requirements. Secondly, the results of this assessment are utilized to evaluate SMTR phases in terms of energy saving, packet delivery success ratio and network life time.

• 융합신호처리학회논문지
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• 제3권2호
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• pp.89-95
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• 2002

글로벌 라우팅(global routing)은 VLSI 설계 과정중의 하나로, 네트리스트의 모든 네트들을 연결하기 위하여 각 네트들을 라우팅 영역(routing area)에 할당시키는 문제이며, 글로벌 라우팅에서 최적의 해를 얻기 위해 maze routing 알고리즘, line-probe 알고리즘, shortest path 기반 알고리즘, Steiner tree 기반 알고리즘등이 이용된다. 본 논문에서는 라우팅 그래프에서 최단 경로 Steiner tree 탐색방법인 weighted network heuristic(WNH)과 이를 기반으로 하는 글로벌 라우팅 유전자 알고리즘(genetic algorithm; GA)을 제안하였으며, 제안한 방식을 시뮬레이티드 어닐링(SA) 방식과 비교, 분석하였다.

• Journal of information and communication convergence engineering
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• 제10권3호
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• pp.264-268
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• 2012

Tree-based structures offer assured optimal paths from the data source to the sink. Shortest routes are disregarded since these do not consider the remaining energy level of the nodes. This shortens the lifetime of the whole network. Most tree-based routing protocols, although aware of the nodes' energy, do not consider an energy aware sleep scheduling scheme. We propose an energy-aware sleep scheduling (EASS) scheme that will improve the sleep scheduling scheme of an existing tree-based routing protocol. An energy harvesting structure will be implemented on the wireless sensor network. The depth of sleep of every node will be based on the harvested energy.

• 한국정보과학회논문지:데이타베이스
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• 제35권2호
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• pp.169-181
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• 2008

대부분의 이동객체들은 공간 네트워크상을 움직이기 때문에, 그들의 궤적을 효과적으로 색인 검색할 수 있는 궤적 기반 색인 구조가 필요하다. 하지만 도로와 같은 공간 네트워크상의 궤적 기반 색인 구조에 대한 연구는 FNR-트리나 MON-트리와 같은 연구가 진행되었을 뿐 연구가 많이 진행되어 있지 않다. 하지만, FNR-트리나 MON-트리 또한 이동객체의 세그먼트만을 저장할 뿐 전체 궤적을 유지하지 못하여, 궤적 질의에 대해 비효율적이다. 따라서 본 논문에서는 공간 네트워크상의 이동객체를 위한 궤적기반 색인 구조인 TMN -Tree(Trajectory of Moving objects on Network-Tree)를 제안한다. 이를 위해, 이동객체를 공간과 시간 특성으로 분류하고, 궤적을 유지함으로써 영역질의와 궤적질의를 동시에 처리할 수 있는 색인 구조를 설계한다. 아울러, 사용자 질의를 시공간영역 내 궤적 질의, 시간영역 내 유사궤적 질의, k-최근접 질의로 분류하고, 이들을 처리하기 위한 질의 처리 알고리즘을 제안한다. 마지막으로 본 논문에서 제안한 궤적 기반 색인 구조가 기존의 색인구조인 FNR-Tree, MON-Tree보다 성능이 향상되었음을 보여준다.