• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.325-338
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• 2012

In this paper, a radio resource allocation scheme for a multi-hop relay transmission in cognitive radio (CR) system is proposed to support the employment of relay nodes in IEEE 802.22 standard for wireless regional area network (WRAN). An optimization problem is formulated to maximize the number of serving secondary users (SUs) under system constraints such as time-divided frame structure for multiplexing and a single resource-unit to every relay-hop. However, due to mathematical complexity, the optimization problem is solved with a sub-optimal manner instead, which takes three steps in the order of user selection, relay/path selection, and frequency selection. In the numerical analysis, this proposed solution is evaluated in terms of service rate denoting as the ratio of the number of serving SUs to the number of service-requesting SUs. Simulation results show the condition of adopting multi-hop relay and the optimum number of relaying hops by comparing with the performance of 1-hop system.

• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2479-2492
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• 1999

Network management system(NMS) provides not only effective monitoring and controlling of network which consists of heterogeneous network elements but prompt response to users' need for high-level communication services. Recommendations of ITU-T and ISO stipulate the managerial abstraction of static and dynamic characteristics of network elements, management functions as well as management communication protocol. But the current description method does not provide the formal mechanism for the behavior characteristics of managed objects in clear manner but in natural language form, the complete specification of managed objects is not fully described. In this paper, we describe determinants for the behaviour of managed objects applicable to every managed object, and present a language for specifying behavioral aspects of managed objects based on their temporal and active properties.

• The Transactions of the Korea Information Processing Society
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• v.4 no.8
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• pp.1961-1974
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• 1997

WWW has accepted widely to the who wants the hypermedia-based internet services. And WWW introduces intranet environment which consists of the networks supporting TCP/IP and HTTP protocol for processing the task of company inside that. Intranet application should support not only acquiring the informations, but also producing, modifying and deleting the ones. But since previous hypermedia development methods lack modeling behavior of system and reuse, we need a new method for intranet application. In this thesis, we have proposed the OOIDM(Object Oriented Intranet application Development Method)supporting modeling behavior of system and reuse. And we have proposed the design patterns available for the intranet domain in order to reuse the design information. And we introduces a case study about OOIDM applying design patterns. Adaptation of design patterns to intranet domain gives us much benefits. Design patterns make it easier to reuse the successful design, architecture and reducing the design decisions.

• The Transactions of the Korea Information Processing Society
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• v.4 no.8
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• pp.1907-1920
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• 1997

In this paper, we present integrated model of postal business that would be newly organized. The integrated model is developed through four phase. First, postal business is analyzed by three parts;collection, transportation and delivery. Second, the modeling criteria are developed that will be used for designing integrated postal business model. Third, object-oriented concepts are used by the steps of postal business modeling criteria captured. Finally, methods applied to developed model are grouped according to their function. Also, active-based mechanisms such as trigger and constraints are developed, and knowledge-based mechanisms such as inference are developed. These selected methods and attributes are encapsulated into objects. These constitute an object-active-knowledge based database model. Finally, Operational Scenario and Service Scenario are composed for real application according to proposed O-A-K model.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.4
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• pp.67-73
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• 2002

There have been increased concerns on mobile stratospheric communication system(SCS) for the purpose of advanced service of personal and high speed communication systems. In fact, this SCS is considered and studied for IMT-2000 service by ITU. Although, it is important to make accurate channel model for prediction of the SCS performance, there is no measured channel data in this system. Thus, in this paper, we estimate the performance of SCS bye use of channel model provided by Corazza(2) and modified by You(3). And also, the effects of channel codings on system performance are analyzed by deriving bit error performance based on realistic Rician log-normal fading channel models. The performance results are divided into three kinds of areas with three kinds of elevation angles 20$^\cire$, 45$^\cire$, and 80$^\cire$. And also the effects of forward error correction channel codings on system performance with Hamming(7,4), HCH( IS,7) and convolutional code of constraint length 3 and code rate R=1/2.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.750-760
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• 1994

In this paper we proposed a multiplexing scheme of real time and non-real traffics in which a congestion control is embedded. Real time traffics are assumed to be nonqueuable and have preemptive priority over non-real time traffics in seizing the common output link, whereas the non-real time traffics wait in the common buffer if the output link is not available for transmission. Real time traffics are encoded according to the bandwidth reduction strategy, paticularly when congestion occurs among non-real time traffics. This scheme provides us an efficient way for utilizing the costly bandwidth resources, by accommodation as many real time traffics as possible with gauranteeing its mimimum bandwidth requirements, and also resloving the congestion encountered among non-real time traffics. We describe the system as a Markov queueing system, provide the analysis by exploiting the matrix geometric method, and present the performance for various performance measures of interest. Some numerical results are also provided.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.411-413
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• 2010

The wireless AP positioning system is under active progress regarding research and commercialization due to its merit of being able to overcome the representing demerits of existing GPS positioning, which are signal distortion and poor signal reception. This system's feature is to collect AP information distributed throughout the real world, store it on database, and execute positioning by comparing with searched AP information. The positioning process uses collected data, whereas comparison of database data uses the fingerprinting method. The fingerprinting method is a probabilistic modeling method that acquires as much of the data collected from one location upon database composition, to store the value's average value and use it in positioning. Yet, using the average value may contain the probability of errors. Such errors are fatal weaknesses for services based on the background of accurate positioning. This paper deals with the characteristics and problems of the previously used wireless AP positioning system, and proposes measures of using AP information for outdoor positioning in order to solve the aforementioned problems.

• Journal of KIISE
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• v.43 no.7
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• pp.763-772
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• 2016

With the spread of smartphones containing multiple on-board sensors, the market for context aware applications have grown. However, due to the limited power capacity of a smartphone, users feel discontented QoS. Additionally, context aware applications require the utilization of many forms of context and sensing information. If context transition has occurred, types of needed sensors must be changed and each sensor modules need to turn on/off. In addition, excessive sensing has been found when the context decision is ambiguous. In this paper, we focus on power consumption associated with the context transition that occurs during indoor/outdoor detection, modeling the activities of the sensor associated with these contexts. And we suggest a freezing algorithm that reduces power consumption in context transition. We experiment with a commercial application that service is indoor/outdoor location tracking, measure power consumption in context transition with and without the utilization of the proposed method. We find that proposed method reduces power consumption about 20% during context transition.

• The KIPS Transactions:PartD
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• v.15D no.5
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• pp.621-628
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• 2008

Many of today's businesses need IT system's flexibility for on-demand business which can be rapidly adapted to environment changes. Service oriented architecture (SOA) provides the infrastructure which makes business flexibility possible under the on-demand operating environment. Therefore, to satisfy these requirements, new approach for assuring business flexibility and enhancing reuse is needed. In this paper, we propose an approach for developing a business process family model (BPFM) in which the variabilities in business process family can be explicitly represented by using the variability analysis method of software product line. In addition, we describe the supporting tool for this approach. It can model the BPFM and generate automatically BPMs through decision and pruning process from BPFM. By using our approach, the business and its IT system can correspond to business environment changes rapidly and efficiently.

• The KIPS Transactions:PartA
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• v.10A no.3
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• pp.189-198
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• 2003

In this paper, we propose a method of analysis to show the heavy-tailed statistical distribution of file sizes in web servers, using TTT plot technique. TTT plot technique, a well-known method in the area of reliability engineering, determines that a distribution of samples fellows a heavy tailed one when their TTT statistical plots are lied on a straight line. We performed an intensive simulation using data gathered from real web servers. The simulation indicates that the proposed method is superior to Hill estimation technique or LLCD plot method in efficiency of data analysis. Moreover, the proposed method eliminates the possible decision error, which Pareto distribution or traditional method might cause.