• The Transactions of the Korea Information Processing Society
• /
• v.5 no.10
• /
• pp.2627-2640
• /
• 1998

In this paper, we analyze the performance of the virtual cell system[1] for the transmission of IP datagrams in mobile computer communications. A virtual cell consistsof a group of physical cells shose base stationsl are implemented b recote bridges and interconnected via high speed datagram packet switched networks. Host mobility is supported at the data link layer using the distributed hierachical location information of mobile hosts. Given mobility and communication ptems among physical cells, the problem of deploying virtual cells is equivalent to the optimization cost for the entire system where interclster communication is more expesive than intracluster communication[2]. Once an iptimal partitionof disjoint clusters is obtained, we deploy the virtual cell system according to the topology of the optimal partition such that each virtual cell correspods to a cluser. To analyze the performance of the virtual cell system, we adopt a BCMP open multipel class queueing network model. In addition to mobility and communication patterns, among physical cells, the topology of the virtual cell system is used to determine service transition probabilities of the queueing network model. With various system parameters, we conduct interesting sensitivity analyses to determine network design tradeoffs. The first application of the proposed model is to determine an adequate network bandwidth for base station networking such that the networks would not become an bottleneck. We also evaluate the network vlilization and system response time due to various types of messages. For instance, when the mobile hosts begin moving fast, the migration rate will be increased. This results of the performance analysis provide a good evidence in demonsratc the sysem effciency under different assumptions of mobility and communication patterns.

• Journal of the Korean Data and Information Science Society
• /
• v.26 no.5
• /
• pp.1129-1139
• /
• 2015

Inference process generates additional triples from knowledge represented in RDF triples of semantic web technology. Tens of million of triples as an initial big data and the additionally inferred triples become a knowledge base for applications such as QA(question&answer) system. The inference engine requires more computing resources to process the triples generated while inferencing. The additional computing resources supplied by underlying resource pool in cloud computing can shorten the execution time. This paper addresses an algorithm to allocate the number of computing nodes "elastically" at runtime on Hadoop, depending on the size of knowledge data fed. The model proposed in this paper is composed of the layered architecture: the top layer for applications, the middle layer for distributed parallel inference engine to process the triples, and lower layer for elastic Hadoop and server visualization. System algorithms and test data are analyzed and discussed in this paper. The model hast the benefit that rich legacy Hadoop applications can be run faster on this system without any modification.

• The Journal of the Korea Contents Association
• /
• v.13 no.11
• /
• pp.187-197
• /
• 2013

Objectives : The purpose of this study was to analyze the effect of outpatient cost sharing reduction on health care utilization of children under 6 years old. Methods : The data in this analysis was the health insurance claims data between August 2006 and July 2008. The study group was divided into two age groups, namely 0-5 years old and 6-10 years old. This study evaluated the impact of policy change on office visits per person and expenditure per visit. In order to do so, the double difference analysis is used. Results: The results showed that outpatient cost-sharing reduction has never really had a huge impact on office visits per person and expenditure per visit. Conclusions: This study showed that the outpatient cost sharing reduction for children under 6 years old policy is not working. Therefore, cost sharing of National Health Insurance by income class is needed.

• Journal of Internet Computing and Services
• /
• v.12 no.5
• /
• pp.47-61
• /
• 2011

Recently, the importance of digital forensic has been magnified because of the dramatic increase of cyber crimes and the increasing complexity of the investigation of target systems such as PCs, servers, and database systems. Moreover, some systems have to be investigated with live forensic techniques. However, even though live forensic techniques have been improved, they are still vulnerable to anti-forensic activities when the target systems are remotely accessible by criminals or their accomplices. To solve this problem, we first suggest a layer-based model and the anti-forensic scenarios which can actually be applicable to each layer. Our suggested model, the Anti-Forensic Activites layer-based model, has 5 layers - the physical layer, network layer, OS layer, database application layer and data layer. Each layer has possible anti-forensic scenarios with detailed commands. Second, we propose a fuzzy expert system for effectively detecting anti-forensic activities. Some anti-forensic activities are hardly distinguished from normal activities. So, we use fuzzy logic for handling ambiguous data. We make rule sets with extracted commands and their arguments from pre-defined scenarios and the fuzzy expert system learns the rule sets. With this system, we can detect anti-forensic activities in real time when performing live forensic.

• Journal of KIISE:Information Networking
• /
• v.29 no.3
• /
• pp.253-264
• /
• 2002

Recently, hierarchical architectures of databases for location management have been proposed in order to accommodate the increase in user population in future personal communication systems. In particular, a 3-level hierarchical database architecture is compatible with current cellular mobile systems. In the architecture, a newly developed additional databases, regional location database(RLR), are positioned between HLR and VLRs. We propose an efficient cache scheme, called the Double T-thresholds Location Cache Scheme. The cache scheme extends the existing T-threshold location cache scheme which is competent only under 2-level architecture of location databases currently adopted by IS-41 and GSM. The idea behind our scheme is to use two pieces of cache information, VLR and RLR serving called portables. The two pieces are required in order to exploit root only locality of registration area(RA) but also locality of regional registration area(RRA) which is the wide area covered by RLR. We also use two threshold values in order to determine whether the two pieces are obsolete. In order to model the RRA residence time, the branching Eralng-$\infty$ distribution is introduced. Our minute cost analysis shows that the double T-threshold location cache scheme yields significant reduction of network and database costs for molt patterns of portables.

• Journal of the Economic Geographical Society of Korea
• /
• v.17 no.4
• /
• pp.771-785
• /
• 2014

As marine desertification and chlorosis in Korean coast have been intensified over time, Korean government is promoting marine afforestation projects. However, marine afforestation location is mainly decided by administrative convenience. Also, there is limited literature on location suitability about the marine afforestation. This study aims to assess location suitability of marine afforestation considering 3 significant criteria: ecological, submarine topographical, and human-social environment. Jeju, the study area of this study, first observed chlorosis in Korean coast at the small fishery town in Seogwipo. Jeju is currently suffering from chlorosis all around the island. Habitat Evaluation Procedure (HEP), 3D kriging, Analytic Hierarchy Process (AHP) is applied as analysis methods. Especially, 3D kriging is utilized for modeling 3D ocean space reflecting ocean environment appropriately. The result shows that Jocheon coast has better location suitability than Seogwipo Pyoseon coast. Jocheon coast has the maximum 61% suitability as the habitat of Ecklonia cava Kjellman, and is highly evaluated in other criteria. The results of this study are expected to find optimal marine afforestation location, and to contribute to the restoration of the Jeju coastal ecosystem and the revitalization of Jeju fishing village societies.

• Journal of Digital Contents Society
• /
• v.15 no.6
• /
• pp.663-673
• /
• 2014

The WBAN technology means a short distance wireless network which provides each device interactive communication by connecting devices inside and outside of body. Standardization on the physical layer, data link layer, network layer and application layer is in progress by IEEE 802.15.6 TG BAN. Wireless body area network is usually configured in energy efficient using sensor and zigbee device due to the power limitation and the characteristics of human body. Wireless sensor network consist of sensor field and sink node. Sensor field are composed a lot of sensor node and sink node collect sensing data. Wireless sensor network has capacity of the self constitution by protocol where placed in large area without fixed position. In this paper, we proposed the efficient addressing scheme for improving the performance of routing algorithm by using ZigBee in WBAN environment. A distributed address allocation scheme used an existing algorithm that has wasted in address space. Therefore proposing x, y and z coordinate axes from divided address space of 16 bit to solve this problems. Each node was reduced not only bitwise but also multi hop using the coordinate axes while routing than Cskip algorithm. I compared the performance between the standard and the proposed mechanism through the numerical analysis. Simulation verified performance about decrease averaging multi hop count that compare proposing algorithm and another. The numerical analysis results show that proposed algorithm reduced the multi hop better than ZigBee distributed address assignment

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.1
• /
• pp.138-145
• /
• 2007

Wireless transmission system using the multipath channel is affected ISI due to the delay spread. So we use a decision feedback equalizer which consist of decision part and feedback filter for remove the ISI effectively. In this paper, we propose a improved adaptive decision feedback equalizer to mitigate ISI effectively. The proposed adaptive decision feedback equalizer is construct by using soft decision device and hierarchical feedback filter based on MMSE sub-optimal equalizer using the LMS algorithm. Soft decision device mitigate the error propagation in feedback filter by incorrectly detected decision symbol and feedback filter which is divided two step independently mitigate the ISI by using a adaptive algorithm. As a result this structure shows better performance than conventional decision feedback equalizer by mitigating the error propagation in filter cause incorrectly detecting symbol. and we get the MSE more rapidly by using larger step-size due to reduce the number of feedback filter tap. In computer simulation, we compare the bit error rate performance of proposed decision feedback equalizer with conventional one on the S-V channel model for UWB system.

• International Commerce and Information Review
• /
• v.4 no.1
• /
• pp.107-128
• /
• 2002

In order to clarify the relationship between the Internet utilization of the Korean small export firms for export marketing and it's performance, first, a research model and hypothesis have been made on a theoretical basis. This research hypothesis has been examined through gathering survey data and a statistical analysis based on MANOVA. The conclusion, as well as the main point of this thesis, is that, in most cases, there was a significant statistical connection between the variables of export performances and Internet-utilized export marketing strategies, which are both based on the classical AIDA model of effective hierarchy of communication for sales and advertising. This conclusion brings forth a substantial topic as well as provides meaningful implications for the Korean small export firms when putting together a marketing strategy using the Internet. It is also hoped that this will come as a reference for other researchers henceforth. However, there is an issue of lack of representativeness when considering that the samples were chosen on the basis of the convenience sampling method. Another issue may be that a portion of the subjects were not related to actual trade, but were, in fact, Web masters who operated e-trade systems. Furthermore, there are also numerous problems of missing data, and 6 out of the 8 main hypotheses possessed the issue of fitness level with the data. Therefore, in order to enhance both the representative and fitness levels of the data of further research for this topic, future respondents will have to have special trade knowledge, as well as technical knowledge of e-trade. However, unless the Internet begins to greatly contribute to export marketing of corporations, this type of enterprising spirit by corporations in gathering suitable respondents will not surface. Although not used in examining the hypotheses of this particular thesis, the relationship between competitive and circumstantial variables, which were added to the upcoming survey, and export performances will soon be analyzed and announced in order to atone for some of the standards this thesis fell short of.

• Journal of KIISE:Information Networking
• /
• v.29 no.2
• /
• pp.117-128
• /
• 2002

Virtual LAN (VLAN) is an architecture to enable communication between end stations as if they were on the same LAN regardless of their physical locations. VLAN defines a limited broadcast domain to reduce the bandwidth waste. The Newbridge Inc. developed a layer 3 VLAN product called VIVID, which configures a VLAN based on W subnet addresses. In a VIVID system, a single route server is deployed for address resolution, VLAN configuration, and data broadcasting to a VLAN. If the size of the network, over which the VLANS supported by the VIVID system spans, becomes larger, this single route server could become a bottleneck point of the system performance. One possible approach to cope with this problem is to deploy multiple route servers. We propose two architectures, organic and independent, to expand the original VIVID system to deploy multiple route servers. A course of simulations are done to analyze the performance of each architecture that we propose. The simulation results show that the performances of the proposed architectures depend on the lengths of VLAN broadcasting sessions and the number of broadcast data frames generated by a session. It has also been shown that there are tradeoffs between the scalability of the architecture and their efficiency in data transmissions.