• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6A
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• pp.361-370
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• 2003

This paper attempts to improve the existing architecture of location register for location management in Private Network to Network Interface(PNNI)-based wireless ATM networks. Our approach enhances the hierarchical architecture of location registers based on a PNNI hierarchical architecture, which is referred to as the logical hierarchy architecture of location registers. This paper introduces a logical hierarchy architecture for location registers to reduce the cost of their location management. This logical hierarchy architecture of location registers begins with the lowest level physical location registers that are organized into clusters called logical groups. These logical groups are then represented in higher layers by logical nodes. These logical nodes are again grouped into clusters that are treated as single nodes by the next higher layer. In this way, all location registers are included in this tree-type logical hierarchy architecture. Compared with the existing physical hierarchy architecture of location registers, the analysis results show that the proposed logical hierarchy architecture can reduce the number of databases and thereby the average total location management cost.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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• pp.3219-3236
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• 2012

A tree routing structure is often adopted for many-to-one data gathering and aggregation in sensor networks. For real-time scenarios, considering lossy wireless links, it is an important issue how to construct a maximum-lifetime data gathering tree with delay constraint. In this work, we study the problem of lifetime-preserving and delay-constrained tree construction in unreliable sensor networks. We prove that the problem is NP-complete. A greedy approximation algorithm is proposed. We use expected transmissions count (ETX) as the link quality indicator, as well as a measure of delay. Our algorithm starts from an arbitrary least ETX tree, and iteratively adjusts the hierarchy of the tree to reduce the load on bottleneck nodes by pruning and grafting its sub-tree. The complexity of the proposed algorithm is $O(N^4)$. Finally, extensive simulations are carried out to verify our approach. Simulation results show that our algorithm provides longer lifetime in various situations compared to existing data gathering schemes.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.3
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• pp.161-168
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• 2002

A secret sharing scheme is a cryptographic protocol to share a secret among a set of participants P in the way that only qualified subsets of P can reconstruct the secret whereas any other subset of P, non-qualified to know the secret, cannot determine anything about the secret. In this paper, we propose a new secret sharing scheme in hierarchical groups, whose hierarchy can be represented as a tree structure. In the tree structure, participants of higher levels have priorities to reconstruct the secret over participants of lower levels. In the absence of the participant of a higher level, it is possible for this participant to delegate the ability to reconstruct the secret to the child nodes of the next lower level through the transfer of his delegation ticket. This scheme has a dynamic access structure through the recursive delegation process from the root to lower levels where participants aren't absent.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.846-856
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• 2016

Wireless sensor networks (WSNs) are widely applied in monitoring and control of environment parameters. It is sometimes necessary to disseminate data through wireless links after they are deployed in order to adjust configuration parameters of sensors or distribute management commands and queries to sensors. Several approaches have been proposed recently for data dissemination in WSNs. However, none of these approaches achieves both high efficiency and low complexity simultaneously. To address this problem, cluster-tree based network architecture, which divides a WSN into hierarchies and clusters is proposed. Upon this architecture, data is delivered from base station to all sensors in clusters hierarchy by hierarchy. In each cluster, father broadcasts data to all his children with instantly decodable network coding (IDNC), and a novel scheme targeting to maximize total transmission gain (MTTG) is proposed. This scheme employs a new packet scheduling algorithm to select IDNC packets, which uses weight status feedback matrix (WSFM) directly. Analysis and simulation results indicate that the transmission efficiency approximate to the best existing approach maximum weight clique, but with much lower computational overhead. Hence, the energy efficiency achieves both in data transmission and processing.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.223-234
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• 2011

For advanced database security, various researches and challenges are being done to keep pace with new information technologies. We suggests new extended access control that make it possible to conform security policies even with uncertain context and purpose. There may be a discrepancy between the syntactic phrase in security policies and that in queries, called semantic gap problem. New access control derive semantic implications from context and purpose hierarchy tree and control the exceed privileges using semantic gap factor calculating the degree of the discrepancy. And then, We illustrate prototype system architecture and show performance comparison with existing access control methods.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.6
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• pp.683-697
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• 2012

In this paper, a risk analysis methodology applicable to shield TBM tunnels was studied. Fault Tree Analysis (FTA) was utilized to identify all risk items and to calculate the probability of failure of each item and Analytic Hierarchy Process (AHP) was used to obtain the impact of each risk item. Finally, a risk level of each risk item can be assessed. Developed methodology is applied to a Seoul subway site in which EPB shield tunnel method was utilized and it was found that risk analysis results matched reasonably well with field data.

• Journal of Korea Game Society
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• v.19 no.5
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• pp.133-142
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• 2019

In this study, 100 types of computationally proposed digital games were analyzed based on the expected marketability. The game classification methodology with five classification criteria proposed by Kim (2017) and the elimination method leveraged by the Decision Tree have been adopted as the methodology of the study. As a result, digital games could be classified into three groups. With the result, designers in the field will be able to leverage computational design methodology to develop a new type of digital game more efficiently by following the proposed hierarchy.

• Korean Institute of Interior Design Journal
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• v.20 no.3
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• pp.249-258
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• 2011

As the elderly population are rapidly growing, the elderly who needs special care and nursing homes for them are also growing. However, many nursing homes were planned without considering the hierarchial space organization such as division of housing unit and nursing unit based on the cognitive and behavioral characteristics of the elderly or accessibility and supportiveness of the staff. This study was to examine the hierarchial characteristics in space organization of nursing homes by using Space Syntax. The subjects were 8 nursing homes in Busan. First, spaces in nursing homes were divided into five areas based on the literature review. Then the hierarchy of space organization for the access layer and layers of living floors was grasped by using G-graph. The access layer has a tree-type hierarchical structure and high visuality. Also, average depth of the space was 5. Then the full integration was analyzed. Mobile area, such as elevator, hallways, or living rooms has a high accessibility and the middle corridor type has commonly been characterized. The nursing stations were analyzed through the control degree and it was low in three nursing homes such as B, C, and G. The low clarity was showed in B, D, and F. The low clarity means that it is relatively difficult to recognize the whole space organization of nursing home. Even though the hierarchy of their living floors was tree-type structure with a high visuality, they has a type of grouping spaces around hallways and spreading, or a ring type.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1859-1862
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• 2002

The replication of data is used to increase its availability, improve the performance of a system, and advance the fault-tolerance of a system. In this paper, it is required for the information about the location of a primary site of the replicas of each data item. The replicas of each data item are hierarchically organized to a tree based on the fact that the root is the primary replica in partially replicated databases. It eliminates useless propagation since the propagation can be done to only sites having replicas following the hierarchy of data. And our algorithm schedules transactions so that the execution order of updates at each primary site is identical at all sites by using timestamp. Using our algorithm, the consistent data are supplied and the performance of read-only transactions can be improved by using tree structure of replicas of each data item.

• International journal of advanced smart convergence
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• v.7 no.4
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• pp.66-74
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• 2018

While new information technology advances have made information access and acquisition methods much more diverse and easier, there are side effects that allow illegal access using diverse and high-performance tools. In order to cope with such threats, there are access control methods in database technology, and various studies are being conducted to extend traditional access control to cope with new computing environments. In this paper, we propose an extended access control with uncertain context-awareness. It enables appropriate security policy enforcement even if the contextual constraints specified by the security policy does not match those accompanied by access request query. We extract semantic implications from context tree, and define the argument that can quantitatively measure the semantic difference between two nodes in the context tree. It is used to semantically enforce the security policy, and to prevent the excessive authorization caused by the implication.