• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.285-290
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• 2010

We investigate the outage probability in terms of QoS (quality of service) in indoor PLC network. We consider various kinds of appliances for realistic indoor PLC network. For estimation of the outage probability, we calculate the time-varying channel responses considering the loading conditions based on regular human activities and include the additive noise. We calculate the outage probability for each terminal and investigate relationship between the outage probability and the channel length, and transmit powers. Our results suggest that the outage probability is increased when the channel length becomes longer because more appliances affect the amount of reduced channel capacity and is not improved distinctly for very high and low outage threshold by increasing the transmit power. However, we can see outage probability improvement for 30% outage threshold case by increasing the transmit power.

• Journal of Korean Society for Quality Management
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• v.42 no.1
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• pp.1-14
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• 2014

Purpose: In this paper, the minimal repair-replacement warranty policy is used to carry out a warranty cost analysis with warranty servicing times and failure times that are statistically correlated to bivariate distributions. Methods: Based on the developed approach by Park and Pham (2012a), we investigate the property of the Freund's bivariate exponential distribution and obtain the number of warranty services using the field data to conduct the warranty cost analysis. Results: Maximum likelihood estimates are presented to estimate the parameters and the warranty model is investigated using a Freund's bivariate exponential distribution. A numerical example is discussed to deal with the applicability of the developed approach in the paper. Conclusion: A novel approach of analyzing the warranty cost is proposed for a product in which failure times and warranty servicing times are used simultaneously to investigate the eligibility of a warranty claim.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.441-447
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• 2003

Recently there is a growing Interest In mobile cellula r network providing multimedia service. However, the link bandwidth of mobile cellular network is not sufficient enough to provide satisfactory services to use rs. To overcome this problem, an adaptive framework has been proposed in this study, we propose a new method of estimating DPR(degradation period ratio) in an adaptive multimedia network where the bandwidth of ongoing call can be dynamically adjusted during its lifetime. DPR is a QoS(quality of service) parameter which represents the ratio of allocated bandwidth below a pre-defined target to the whole service time of a call. We improve estimation method of DPR using DTMC(discrete time Markov chain) model. We also calculate mean degradation period and degradation probability more precisely than in existing studies. Under Threshold CAC(call admission control) algorithm, we present analytically how to guarantee QoS to users and illustrate the method by numerical examples. The proposed method is expected to be used as one of CAC schemes in guaranteeing predefined QoS level of DPR

• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.43-49
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• 2023

In modern wireless communication systems including beamformers or location-based services (LBS), which employ multiple antenna elements, estimating the number of signals is essential for accurately determining the quality of the communication service. Representative signal number estimation algorithms including the Akaike information criterion (AIC) and minimum description length (MDL) algorithms, which are information theoretical criterion models, determine the number of signals based on a reference value that minimizes each criterion. In general, increasing the number of elements mounted onto the array antenna enhances the performance of estimating the number of signals; however, it increases the computational complexity of the estimation algorithm. In addition, various configurations of array antennas for the increased number of antenna elements should be considered to efficiently utilize them in a limited location. In this paper, we introduce an efficient signal number estimation algorithm based on the beamspace based AIC and MDL techniques that reduce the computational complexity by reducing the dimension of a uniform circular array antenna. Since this algorithm is based on a uniform circular array antenna, it presents the advantages of a circular array antenna. The performance of the proposed signal number estimation algorithm is evaluated through computer simulation examples.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.1040-1057
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• 2014

In this paper, a new bit rate estimation scheme is proposed to determine the bit rate for each subclass in an MPEG-2 TS to H.264/AVC transcoder after dividing an input MPEG-2 TS sequence into several subclasses. Video format transcoding in conventional IPTV and Smart TV services is a time-consuming process since the input sequence should be fully transcoded several times with different bit-rates to decide the bit-rate suitable for a service. The proposed scheme can automatically decide the bit-rate for the transcoded video sequence in those services which can be stored on a video streaming server as small as possible without losing any subject quality loss. In the proposed scheme, an input sequence to the transcoder is sub-classified by hierarchical clustering using a parameter value extracted from each frame. The candidate frames of each subclass are used to estimate the bit rate using a statistical analysis and a mathematical model. Experimental results show that the proposed scheme reduces the bit rate by, on an average approximately 52% in low-complexity video and 6% in high-complexity video with negligible degradation in subjective quality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.882-888
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• 2006

Multiuser detection can significantly increase system capacity and improve service quality compared with the existing matched filter. In this paper, we introduce an method which efficiently calculates the maximum likelihood (ML) metric based on the gradient search (GS). The ML detection needs user powers as well as their spreading codes. A method is also proposed that allows us to detect data bits with the estimation of user powers when they are unknown. Computer simulation shows that the proposed method can nearly achieve the same performance as the GS with perfectly hewn user powers.

• ETRI Journal
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• v.28 no.2
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• pp.205-215
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• 2006

Wireless data communication (WDC) services are increasingly penetrating the market. The two main alternative WDC technologies are wireless LAN and mobile Internet. Services based on these technologies display differences in quality attributes such as terminal device, data transmission speed, pricing scheme and so on. How consumers choose between these two alternatives will be determined by their preferences regarding such quality attributes. In turn, their preferences will affect the evolution of WDC services and related technologies. This study employs a conjoint analysis of consumer valuations of quality attributes of wireless LAN and mobile Internet services. Respondents rate hypothetical service alternatives featuring various combinations of quality attributes. By estimating consumer willingness to pay for the attributes of WDC services, the authors predict the evolution of WDC services and related technologies along various quality dimensions, make a comparison with the results of a previous study, and draw policy implications for national-and company-level R&D strategies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4125-4132
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• 2011

The research of image quality estimation standard and the image quality change according to the network traffic load increase at IPTV multicasting service is necessary because the concern of IPTV(Internet Protocol TV) service become active recently. In the research, for finding out the threshold value of network performance elements giving the effect to the image quality according to the network traffic load, we developed S/W to operate the test bed network and make the test scenario through test bed network test and then we expand the test environment scope to the college network and try to measure the image quality change of IPTV multicasting service according to the network traffic load increase at the college network similar to the real IPTV service environment.

• Journal of Internet Computing and Services
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• v.5 no.1
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• pp.33-39
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• 2004

In this paper, so that government official in target extent of relevant shame capacitates CMM measuring achievement result by each process as quantitative because do standard, repeat and achieves gap analysis and estimation solidify knowledge management of information base enabling "Quality control, production management, cost control, integral management of knowledge", Solidify customer service through "high-quality, differentiation" of information. Establish administration and supervision item to reach 4 steps level in information ability measurement in formation to prove business efficiency through process optimization and improves formation maturity through voluntary effort of formation continuously. Suggested model who analyze and evaluates application in domestic SI specialty company.I specialty company.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.419-427
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• 2009

In existing studies about benefit of water quality improvement using WTP, the object of survey is described pre-policy water quality as "current water quality" and improved (post-policy) water quality as "boatable, fishable and swimmable". Multiply WTP by the number of households of basin is total benefit. The existing studies are not benefit of a specific water resource business but benefit of a policy on unsubstantial water resource business. Because of a lack of objectivity and oversimplification, it is difficult for survey respondents to understand an object of survey. The purpose of this study is to evaluate a benefit estimation methodology for raw water quality improvement in water resource development business. After conducting a survey of WTP of 1,000 housewives who is using water service in the National Capital region, the relational expression of water quality improvement (BOD) and WTP is derived by using statistical analysis of the survey. As a case study, the stream water quality improvement benefit of Song Li Won multipurpose dam was evaluated, which is planned to be built at the local secondary stream section on Nae Sung stream in Nak-Dong River system. As a result of study, annual average benefit evaluation is 5,980 million won on the average annual planned discharge, 8,663 million won on the planned discharge during the period except for wet season (July to October), 11,905 million won on the planned discharge during water quality declining period and 14,502 million won on the planned discharge during water quality declining period respectively. By using the relational expression of BOD-WTP, it is easy to estimate the benefit without regard for water quality.