• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.223-230
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• 2003

Feature-based similarity retrieval has become an important research issue in multimedia database systems. The features of multimedia data are useful for discriminating between multimedia objects (e 'g', documents, images, video, music score, etc.). For example, images are represented by their color histograms, texture vectors, and shape descriptors, and are usually high-dimensional data. The performance of conventional multidimensional data structures(e'g', R- Tree family, K-D-B tree, grid file, TV-tree) tends to deteriorate as the number of dimensions of feature vectors increases. The R＊-tree is the most successful variant of the R-tree. In this paper, we propose a SOM-based R＊-tree as a new indexing method for high-dimensional feature vectors.The SOM-based R＊-tree combines SOM and R＊-tree to achieve search performance more scalable to high dimensionalities. Self-Organizing Maps (SOMs) provide mapping from high-dimensional feature vectors onto a two dimensional space. The mapping preserves the topology of the feature vectors. The map is called a topological of the feature map, and preserves the mutual relationship (similarity) in the feature spaces of input data, clustering mutually similar feature vectors in neighboring nodes. Each node of the topological feature map holds a codebook vector. A best-matching-image-list. (BMIL) holds similar images that are closest to each codebook vector. In a topological feature map, there are empty nodes in which no image is classified. When we build an R＊-tree, we use codebook vectors of topological feature map which eliminates the empty nodes that cause unnecessary disk access and degrade retrieval performance. We experimentally compare the retrieval time cost of a SOM-based R＊-tree with that of an SOM and an R＊-tree using color feature vectors extracted from 40, 000 images. The result show that the SOM-based R＊-tree outperforms both the SOM and R＊-tree due to the reduction of the number of nodes required to build R＊-tree and retrieval time cost.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.129-140
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• 2002

In this paper, we consider the problem of packet transmission in a wavelength division multiplexed(WDM) optical network. Our network model assumes that receivers are fixed-tuned and transmitters are tunable such that optical lasers assigned to transmitters have limited access to the network bandwidth: hence each node must be equipped with multiple optical lasers and/or multiple optical filters in order to maintain a single-hop network. We first analyze scheduling all-to-all packet transmissions and present optimum scheduling for all-to-all packet transmissions. We then extend the analysis to the case of arbitrary traffic demands. We show that the scheduling with arbitrary traffic demand is NP-hard. A heuristic algorithm based on list scheduling is presented. The upper bound so obtained is compared with the lower bound and provides performance guarantees with arbitrary demands. The result are applicable to arbitrary tuning delay, arbitrary number of wavelength channels and optical lasers of arbitrary tuning ranges.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.2
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• pp.105-115
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• 2002

Since NUMA architecture has to access remote memory an interconnection network determines the performance of CC-NUMA system Bus which has been used as a popular interconnection network has many limits to build a large-scale system because of the limited physical scalabilty and bandwidth Dual ring interconnection network composed of high speed point-to-point links is made up for resolving the defects of the bus for large-scale system But it also has a problem that the response latency is rapidly increased when many node are attached to snooping based CC-NUMA system with dual ring In this paper we propose a chordal ring architecture in order to overcome the problem of the dual ring on snooping based CC-NUMA system and design and efficient link controller adopted to this architecture. We also analyze the effects of chordal ring architecture on the system performance and the response latency by using probability driven simulator.

• Smart Media Journal
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• v.8 no.1
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• pp.43-50
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• 2019

As numerous devices are connected through a wireless network, there exist many studies conducted to efficiently connect the devices. While earlier studies often use clustering for efficient device management, there is a load-intensive cluster node which may lead the entire network to be unstable. In order to solve this problem, we propose a scheduling model for centralized unequal chain clustering for efficient management of sensor nodes. For the cluster configuration, this study is based on the cluster head range and the distance to the base station(BS). The main vector projection technique is used to construct clustering with concentricity where the positions of the base stations are not the same. We utilize a multiple radio access interface, multiple-input multiple-output (MIMO), for data transmission. Experiments show that cluster head energy consumption is reduced and network lifetime is improved.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.53-64
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• 2005

Previous secure routing protocols for wireless sensor networks assume that a sink is static. In many cases, however, a sink operated by man or vehicle is moving. A mobile sink creates a lot of technical problems such as reconfiguration of routing path exposure of sink location. and selection of secure access point node, which are not considered by many previous researches. In this paper, we propose a new secure routing scheme for solving such problems using hi-directional hash chain and delegation nodes of grid structure. This scheme provides a secure routing path and prevents attacker from recognizing the location of a mobile sink in sensor networks. This new method reduces the resource requirements compared to the cashed routing schemes. Simulation results also show that the system is secure and efficient enough.

• The Journal of Korean Institute of Information Technology
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• v.17 no.5
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• pp.1-12
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• 2019

Unlike existing Open APIs, Linked Data are made as a huge intelligent base to perform high-level SPARQL queries, and it is possible to create efficiently a new content by mashuping different information from various datasets. This paper implements a responsive web application for location-based semantic search. We mashup DBpedia, a kind of Linked Data, and GoogleMap API provided by Google, and provide a semantic browser function to confirm detail information regarding retrieved objects. Our system can be used in various access environments such as PC and mobile by applying responsive web design idea. The system implemented in this paper compares functional specifications with existing systems with similar functions. The comparison results show the superiority of our system in various aspects such as using semantic, linked-based browser, and mashup function.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.8
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• pp.985-992
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• 2020

Edge computing is a technology that can prepare for a new era of cloud computing. Edge computing is not a remote data center where data is processed and computed, but low-latency/high-speed computing is realized by adding computing power and data processing power to the edge side close to an access point such as a terminal device or a gateway. It is possible. The types of edge computing include mobile edge computing, fog computing, and cloudlet computing. In this article, we describes existing open source platforms for implementing edge computing nodes. By presenting and comparing the structure, features of open source edge platforms, it is possible to acquire knowledge required to select the best edge platform for industrial engineers who want to build an edge node using an actual open source edge computing platform.

• Journal of Internet of Things and Convergence
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• v.8 no.5
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• pp.55-61
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• 2022

Today's payment systems are becoming unmanned and changing to a way of paying with kiosks. This has the advantage of convenient payment because consumers can select a menu and specify the number of products to be purchased with just a touch of the screen. However, from the point of view of system security, the actual kiosk system has various vulnerabilities. This can hijack the administrator account, gain system privileges, and perform malicious actions. In addition, it is exposed to a number of security threats, such as the possibility of wasting unnecessary resources by abnormally increasing the number of payments, and causing the device to fail to operate normally. Therefore, in this paper, if any node of a participant in the solana blockchain approves an incorrect fork, the stake of the voting nodes is deleted. Also, since all participants can see the transaction history due to the nature of the block chain, I intend to write a thesis on a system that improves the vulnerability of kiosk payments by separating the access rights through the private blockchain.

• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.409-414
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• 2008

In mobile ad hoc networks, most of on demand routing protocols such as DSR and AODV do not deal with traffic load during the route discovery procedure. To solve the congestion and achieve load balancing, many protocols have been proposed. However, the existing load balancing schemes has only considered avoiding the congested route in the route discovery procedure or finding an alternative route path during a communication session. To mitigate this problem, we have proposed a new scheme which considers the packet bursting mechanism in congested nodes. The proposed packet bursting scheme, which is originally introduced in IEEE 802.11e QoS specification, is to transmit multiple packets right after channel acquisition. Thus, congested nodes can forward buffered packets promptly and minimize bottleneck situation. Each node begins to transmit packets in normal mode whenever its congested status is dissolved. We also propose two threshold values to define exact overloaded status adaptively; one is interface queue length and the other is buffer occupancy time. Through an experimental simulation study, we have compared and contrasted our protocol with normal on demand routing protocols and showed that the proposed scheme is more efficient and effective especially when network traffic is heavily loaded.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.2
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• pp.91-101
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• 2006

Researches on services of vehicles have been mainly focused on how to provide useful information and entertainment for an in-vehicle driver. However, the needs are appreciably increased for more advanced services that help drivers to check and manage their vehicles conveniently, without requiring drivers to attach to their vehicles. It is a sort of ubiquitous computing, providing an intelligent interactive services for human at any time and any where. In this paper, we present an intelligent vehicle information system to enable a driver to remotely diagnose and control a vehicle via CDMA communication network connected to the Internet. The system improves mobility for diagnosis and control of vehicle by implementing a cut and call back mechanism, which allows the vehicle terminal to have access to the information server on the Internet via CDMA call. No matter where the driver is, he can obtain the remote diagnosis and control services on the web browser without any additional application installation. Design methodology is introduced and evaluation results are analyzed for the CDMA-based intelligent vehicle information system. The experimental results show that the response time of the vehicle terminal to a web client request is 10.302 seconds at the beginning and 646.44ms thereafter. The average response time of CAN sensor node to a vehicle terminal request is 6.669ms.