• Journal of Korea Multimedia Society
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• v.7 no.10
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• pp.1436-1442
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• 2004

A shared-based tree established by the Core Based Tree multicast routing protocol (CBT), the Protocol Independent Multicast Sparse-Mode(PIM-SM), or the Core-Manager based Multicast Routing(CMMR) is rooted at a center node called core or Rendezvous Point(RP). The routes from the core (or RP) to the members of the multicast group are shortest paths. The costs of the trees constructed based on the core and the packet delays are dependent on the location of the core. The location of the core may affect the cost and performance of the shared-based tree. In this paper, we propose three methods for selecting the set of candidate cores. The three proposed methods, namely, k-minimum average cost, k-maximum degree, k-maximum weight are compared with a method which select the candidate cores randomly. Three performance measures, namely, tree cost, mean packet delay, and maximum packet delay are considered. Our simulation results show that the three proposed methods produce lower tree cost, significantly lower mean packet delay and maximum packet delay than the method which selects the candidate cores randomly.

• Journal of Internet Computing and Services
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• v.5 no.5
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• pp.17-26
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• 2004

Mobile multicast schemes are classified into remote subscription and bi-directional tunneling. While the former scheme has much overhead in the maintenances of multicast tree, the latter suffers from inefficient routing. In this paper, we propose dynamic mobile multicast routing (DMMR) scheme, which is operated on the basis of cost functions related with forwarding cost and tree reconstruction cost, Basically DMMR intends to find lower cost between forwarding cost and tree reconstruction cost. Forwarding cost is the cost of tunneling multicast packets from home agent, and tree reconstruction cost is the joining cost of foreign agent to multicast group. In the case that a mobile host moves to the other area, its foreign agent calculates cost functions related with forwarding cost and tree reconstruction cost. If forwarding cost is higher than tree reconstruction cost, foreign agent joins to multicast group and reconstructs the multicast tree. Accordingly, foreign agent can dynamically adapt remote subscription or bi-directional tunneling, Our scheme provides more stable multicast service to the mobile hosts regardless of the movements of mobile host and the number of mobile group members.

• The KIPS Transactions:PartC
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• v.16C no.1
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• pp.83-90
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• 2009

Wireless Sensor Network (WSN) is a wireless network that gathers information from remote area with autonomously configured routing path. We propose a fusion based routing for a 'convergecast' in which all sensors periodically forward collected data to a base station. Previous researches dealt with only full-fusion or no-fusion case. Our Fusion rate based Spanning Tree (FST) can provide effective routing topology in terms of total cost according to all ranges of fusion rate f ($0{\leq}f{\leq}1$). FST is optimum for convergecast in case of no-fusion (f = 0) and full-fusion (f = 1) and outperforms the Shortest Path spanning Tree (SPT) or Minimum Spanning Tree (MST) for any range of f (0 < f < 1). Simulation of 100-node WSN shows that the total length of FST is shorter than MST and SPT nearby 31% and 8% respectively in terms of topology lengths for all range of f. As a result, we confirmed that FST is a very useful WSN topology.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.943-946
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• 1999

In this paper, we present a new clock routing algorithm which minimizes total wirelength under any given path-length skew bound. The algorithm onstructs a bounded-skew tree(BST) in two steps:(ⅰ) a bottom-up phase to construct a binary tree of shortest-distance feasible regions which represent the loci of possible placements of clock entry points, and (ⅱ) a top-down phase to determine the exact locations of clock entry points. Experimental results show that our clock routing algorithm, named BST/DME, can produce a set of solutions with skew and wirelength trade-off.

• IEMEK Journal of Embedded Systems and Applications
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• v.1 no.2
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• pp.104-112
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• 2006

ZigBee is the emerging industrial standard for ad hoc networks based on IEEE 802.15.4. It is used for low data rate and low power wireless network applications. Expected applications of ZigBee include wireless sensor networks for remote monitoring, home control, and industrial automation. Since one of the most important design goals of ZigBee is to reduce the installation and running costs, the ZigBee stack is embedded in the cheap and small micro-controller unit. The hierarchical routing algorithm is used for ZigBee end devices which have very limited resources. Using the block addressing scheme, end devices can send data to the destination without a routing table. However, hierarchical routing has the problem that the packets follow the tree hierarchy to the destination even if the destination is located nearby. In this paper, we propose a scheme to improve the hierarchical routing algorithm in ZigBee networks by employing the neighbor table that is originally used together with the routing table. We suggest selecting the neighbor node that has the minimum remaining hops to the destination as the next hop node. Simulation result shows that the proposed scheme saves more than 30% of the hop counts compared with the original hierarchical routing.

• Journal of the Korea Society of Computer and Information
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• v.9 no.3
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• pp.189-194
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• 2004

This paper proposes a Simulated Annealing(SA) algorithm for cluster-based Multicast Routing problems. Multicasting, the transmission of data to a group, can be solved from constructing multicast tree, that is. the whole network is partitioned to some clusters and the clusters are constructed by multicast tree. Multicast tree can be constructed by minimum-cost Steiner tree. In this paper, an SA algorithm is used in the minimum-cost Steiner tree. Especially, in SA, the cooling schedule is an important factor for the algorithm. Hence, in this paper, a cooling schedule is proposed for SA for multicast routing problems and analyzed the simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.24-35
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• 2008

We propose a tree-based integrated network of infrastructure network and mobile ad hoc network to effectively support Mobile IP for mobile ad hoc networks and also proposed a network management protocol for formation and management of the integrated network and a tree-based routing protocol suitable for the integrated network. The integrated network has fixed gateways(IGs) that connect two hybrid networks and the mobile nodes in the network form a small sized trees based on the mobile nodes that are in the communication distance with a IG. A new node joins an arbitrary tree and is registered with its HA and FA along tree path. In addition, the proposed protocol establishes a route efficiently by using the tree information managed in every node. We examined the effectiveness of the tree-based integrated network for some possible network deployment scenarios and compared our routing protocol against the Mobile IP supported AODV protocol.

• Proceedings of the IEEK Conference
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• 2001.06c
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• pp.199-202
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• 2001

In this paper, we proposed and analyzed a new class of irregular fault-tolerant multistage interconnection network named as Extended-QT(Quad Tree) network. E-QT network is extended QT network. A unique path MIN usually is low hardware complexity and control algorithm. So we proposes a class of multipath MIN which are obtained by adding self-loop auxiliary links at the a1l stages in QT(Quad Tree) networks so that they can provide more paths between each source-destination pair. The routing of proposed structure is adaptived and is based by a routing tag. Starting with the routing tag for the minimum path between a given source-destination pair, routing algorithm uses a set of rules to select switches and modify routing tag. Trying the self-loop auxiliary link when both of the output links are unavailable. If the trying is failure, the packet discard. In simulation, an index of performance called reliability and cost are introduced to compare different kinds of MINs. As a result, the prouosed MINs have better capacity than 07 networks.

• Journal of information and communication convergence engineering
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• v.6 no.4
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• pp.383-390
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• 2008

Clock skew modeling is important in the performance evaluation and prediction of clock distribution network and it is one of the major constraints for high-speed operation of synchronous integrated circuits. In clock routing synthesis, it is necessary to reduce the clock skew under the specified skew bound, while minimizing the cost such as total wire length and delay. In this paper, a new efficient bounded clock skew routing method is described, which generalizes the well-known bounded skew tree method by allowing loops, i.e., link-edges can be inserted to a clock tree when they are beneficial to reduce the clock skew and/or the wire length. Furthermore, routing topology construction and wire sizing is used to reduce clock delay.

• Journal of Information Processing Systems
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• v.14 no.2
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• pp.396-417
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• 2018

GR-tree and query aggregation techniques have been proposed for spatial query processing in conventional spatial query processing for wireless sensor networks. Although these spatial query processing techniques consider spatial query optimization, time query optimization is not taken into consideration. The index reorganization cost and communication cost for the parent sensor nodes increase the energy consumption that is required to ensure the most efficient operation in the wireless sensor node. This paper proposes itinerary-based R-tree (IR-tree) for more efficient spatial-temporal query processing in wireless sensor networks. This paper analyzes the performance of previous studies and IR-tree, which are the conventional spatial query processing techniques, with regard to the accuracy, energy consumption, and query processing time of the query results using the wireless sensor data with Uniform, Gauss, and Skew distributions. This paper proves the superiority of the proposed IR-tree-based space-time indexing.