• Annual Conference of KIPS
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• 2008.05a
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• pp.913-916
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• 2008

TPS(Triple Play Service)를 통한 IP-TV,인터넷, 전화 등이 통합되는 추세에서, IPv6 상용네트워크가 수 년 안에 구축될 필연성을 공감하고 있다. 그러나 [1] 현재 IP-TV 서비스에서 Delay, Jitter,전송장애등 QoS에 대한 사용자 불만이 계속 발생하고 있다. 또한 현재 서비스중지 (DoS : Denial of Service)를 유발하는 [2] 인터넷 침해 사고가 월 평균 2157건 이상 발생하는 등, Security Issue의 증가 문제가 지속 되고 있다. IPv4/IPv6 듀얼 스택 멀티 캐스트 네트워크를 구현하여, 라우팅, 멀티캐스트(PIM-SM), QoS, Security 이슈에 대한, 최적의 방안을 도출하여, 라우팅 구현시 IPv6 라우팅 프로토클 간에 재분배(Redistribution) 장애 해결책, IPv6 특성에 따른 멀티캐스트 그룹주소 지정시의 장애대책을 제시하였고, QoS 에서는 기존의 QoS 정책의 문제점과 IPv6의 고유한 패킷 구조의 장점을 활용한 Adaptive QoS 방법을 제시하고, IPv6 멀티캐스트 서비스 중지 공격 유형을 정의하여, 최적화된 IPv6 멀티캐스트 구성 모델을 제시 하였다. 결론적으로 구현된 시스템에서 IPv6 패킷 분석을 통해서 최적화된 경로 통신 및 차별화된 IPv6 패킷의 QoS 방안을 제시하였으며, 서비스 중지공격을 대응하는 Security 보장성을 갖고 있음을 검증하여, 향후 상용화된 IPv4/IPv6 네트워크 구현을 위한 최적화 방안을 제시 하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.113-120
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• 2006

This thesis deals with solutions such as coverage area extension, reduction of the shadow region and performance enhancement of handover caused by structural modification of WiBro network. The More far the distance of RAS(Radio Access Station) and SS(Subscriber Station) is in micro cell, the more bad the quality of channel environment becomes owing to radio interference. Consequently, it causes the deterioration of the throughput and also the deterioration of communication quality in many sides. In fact, most users of WiBro are located in the region, the QPSK region which is bad in point of channel quality. It brings the service complaint by user. We select RS(relay station) to solve the matter caused by channel environment in this cell, and extend coverage and improve the performance of handover call blocking.

• Journal of Korea Multimedia Society
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• v.13 no.4
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• pp.560-574
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• 2010

Recently, many people can easily contact video telephony service through the mobile terminal owing to the commercialization of 3G communication technology. However, the quality of the serviced video telephony has been not good yet by the actual mobile restrictions. For solving quality problems, this paper presents the design of the object-based video CODEC using hybrid transform in mobile video telephony. The proposed design firstly segment each frame into a significant object and an insignificant object. The proposed design is to improve the quality of a significant object by limiting the bit rate of a insignificant object. Thus, we compress a significant object with high quality and low compression ratio and compress an insignificant object with low quality and high compression ratio. Furthermore, we control the bit rate of the video stream in the limited bandwidth by adjusting the compression ratio of each object. From experimental results, we confirmed that our method has more higher quality than methods in the conventional CODECs at the significant region on the same bit rate.

• Journal of Convergence for Information Technology
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• v.7 no.6
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• pp.209-218
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• 2017

To propose a contents model for children's smart watch, this study interview 15mothers who have a child using smart watches. Most mothers purchase smart watches for children to warrant their security and manage their schedules, and they use them for sending a call or text to their children, tracking or managing children's location and schedule. Mothers were satisfied with a smart watch's function of communication and safety management, but dissatisfied learning-oriented contents and worrried about bad influenced on children development. Through in-depth interviews, this study propose a persona model for children's smart watch for enhancing parent-child interaction and physical cognitive language socioemotional convergence play contents.

• The KIPS Transactions:PartA
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• v.13A no.3 s.100
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• pp.223-230
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• 2006

A MMORPG(Massively Multiplayer Online Role-Playing Game) is an online role-playing game in which a large number of players can interact with each other in the same world at the same time. Most of them require significant hardware requirements(e.g., servers and bandwidth), and dedicated support staff. Despite the efforts of developers, users often cite overpopulation, lag, and poor support as problems of games. In this paper, a dynamic load balancing method for MMORPGS is proposed. It tries to adapt to dynamic change of population by using dynamic map-partition method with VML(Virtual Map Layer) which consists of fields, sector groups, sectors, and cells. From the experimental results, our approach achieves about $23^{\sim}67%$ lower loads for each field server. By the modification to Virtual Area Layer, we can easily manage problems that come from changes of map data, resources' status, and users' behavior pattern.

• The Journal of Society for e-Business Studies
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• v.16 no.4
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• pp.125-137
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• 2011

Product reviews in online shopping sites can serve as a useful guideline to buying decisions of customers. However, due to the massive amount of such reviews, it is almost impossible for users to read all the product reviews. For this reason, e-commerce sites provide users with useful reviews or statistics of ratings on products that are manually chosen or calculated. Opinion mining or sentiment analysis is a study on automating above process that involves firstly analyzing users' reviews on a product to tell if a review contains positive or negative feedback, and secondly, providing a summarized report of users' opinions. Previous researches focus on either providing polarity of a user's opinion or summarizing user's opinion on a feature of a product that result in relatively low usage of information that a user review contains. Actual user reviews contains not only mere assessment of a product, but also dissatisfaction and flaws of a product that a user experiences. There are increasing needs for effective analysis on such criteria to help users on their decision-making process. This paper proposes a model that stores various types of user reviews in a data warehouse, and analyzes integrated reviews dynamically. Also, we analyze reviews of an online application shopping site with the proposed model.

• Journal of Intelligence and Information Systems
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• v.21 no.4
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• pp.53-77
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• 2015

Mobile commerce provides a convenient shopping experience in which users can buy products without the constraints of time and space. Mobile commerce has already set off a mega trend in Korea. The market size is estimated at approximately 15 trillion won (KRW) for 2015, thus far. In the Korean market, social commerce and open market are key components. Social commerce has an overwhelming open market in terms of the number of users in the Korean mobile commerce market. From the point of view of the industry, quick market entry, and content curation are considered to be the major success factors, reflecting the rapid growth of social commerce in the market. However, academics' empirical research and analysis to prove the success rate of social commerce is still insufficient. Henceforward, it is to be expected that social commerce and the open market in the Korean mobile commerce will compete intensively. So it is important to conduct an empirical analysis to prove the differences in user experience between social commerce and open market. This paper is an exploratory study that shows a comparative analysis of social commerce and the open market regarding user experience, which is based on the mobile users' reviews. Firstly, this study includes a collection of approximately 10,000 user reviews of social commerce and open market listed Google play. A collection of mobile user reviews were classified into topics, such as perceived usefulness and perceived ease of use through LDA topic modeling. Then, a sentimental analysis and co-occurrence analysis on the topics of perceived usefulness and perceived ease of use was conducted. The study's results demonstrated that social commerce users have a more positive experience in terms of service usefulness and convenience versus open market in the mobile commerce market. Social commerce has provided positive user experiences to mobile users in terms of service areas, like 'delivery,' 'coupon,' and 'discount,' while open market has been faced with user complaints in terms of technical problems and inconveniences like 'login error,' 'view details,' and 'stoppage.' This result has shown that social commerce has a good performance in terms of user service experience, since the aggressive marketing campaign conducted and there have been investments in building logistics infrastructure. However, the open market still has mobile optimization problems, since the open market in mobile commerce still has not resolved user complaints and inconveniences from technical problems. This study presents an exploratory research method used to analyze user experience by utilizing an empirical approach to user reviews. In contrast to previous studies, which conducted surveys to analyze user experience, this study was conducted by using empirical analysis that incorporates user reviews for reflecting users' vivid and actual experiences. Specifically, by using an LDA topic model and TAM this study presents its methodology, which shows an analysis of user reviews that are effective due to the method of dividing user reviews into service areas and technical areas from a new perspective. The methodology of this study has not only proven the differences in user experience between social commerce and open market, but also has provided a deep understanding of user experience in Korean mobile commerce. In addition, the results of this study have important implications on social commerce and open market by proving that user insights can be utilized in establishing competitive and groundbreaking strategies in the market. The limitations and research direction for follow-up studies are as follows. In a follow-up study, it will be required to design a more elaborate technique of the text analysis. This study could not clearly refine the user reviews, even though the ones online have inherent typos and mistakes. This study has proven that the user reviews are an invaluable source to analyze user experience. The methodology of this study can be expected to further expand comparative research of services using user reviews. Even at this moment, users around the world are posting their reviews about service experiences after using the mobile game, commerce, and messenger applications.

• KIPS Transactions on Software and Data Engineering
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• v.7 no.8
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• pp.287-296
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• 2018

In the recent commercial DBMS market, as the users' burden and complaint which are related to high price licensing policy and late technical support service are increasingly rising, the concern for use of open source DBMS which has no problem with compatibility or stability is escalating. Due to the fact, the cases saving the cost are growing by converting Oracle Corporation's applications, which has about 60% share in the DBMS market, to an open source DBMS. However, in converting non-interchange sentences to an ANSI standard-based open source DBMS because of the use of PL/SQL in Oracle Corporation provides, a lot of manual work accompanies, so there is a lot of loss of time and money. Therefore, a tool that automatically converts PL/SQL to standard SQL is required. The proposed automation tool for the conversion of applications converts PL/SQL to Java Stored Procedure, an open source DBMS-based ANSI standard programming language. Through carrying out a test on the automation tool, it is proved that the tool will contribute to shortening time and saving cost by verifying the identity of input-output data and its reliability after correcting errors in converting to Java Stored Procedure.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.5
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• pp.14-24
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• 2010

Although the existing X-CASH card system observes the KS standard for a transportation card system, there has been an issue for interoperability between X-CASH and other public transportation system due to the partially undefined part in the standard. This issue is followed by the inconvenience of the existing X-CASH users. If the existing X-CASH card user wants to get any other public transportations which are not interoperated with X-CASH, the user would have to buy other cards. Consequently, some users have to bring more than one card with them. In addition, it is almost impossible that the existing X-CASH system operator makes the X-CASH card available for the infrastructure built by other cards operators because their technologies are too much different. The X-CASH operator must construct its own infrastructure on the same route and it would cause an unnecessary loss of expense and labor. To solve these problems, We modified the existing X-CASH system and developed the Nation-wide Interoerable X-CASH system which lets both the existing X-CASH card and Nation-wide Interoperable X-CASH card work. This developed X-CASH system consists of the purchase SAM, the purchase terminal and the settlement. And The conformity test for it was successfully authorized. Also we, KORAIL NETWORKS, have done the test-bed on this Nation-wide interoperable X-CASH system in Gwangju for six months with Telecommunications & Clearings, the HiPlusCard Corporation. This test confirmed that the Nation-wide Interoperable X-CASH system would practically work well.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.5
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• pp.13-20
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• 2008

Although digital hearing aid algorithms have been developed to compensate hearing loss and to help hearing impaired people to communicate with others, digital hearing aid user still complain about difficulty of hearing the speech. The reason could be the quality of speech through digital hearing aid is insufficient to understand the speech caused by feedback, residual noise and etc. And another thing is masking effect among formants that makes sound quality low. In this study, we measured the masking characteristics of normal listeners and hearing impaired listeners having presbyacusis to confirm masking effect in speech itself. The experiment is composed of 5 tests; pure tone test, speech reception threshold (SRT) test, word recognition score (WRS) test, puretone masking test and speech masking test. In speech masking test, there are 25 speeches in each speech set. And log likelihood ratio (LLR) is introduced to evaluate the distortion of each speech objectively. As a result, the speech perception became lower by increasing the quantity of formant enhancement. And each enhanced speech in a speech set has statistically similar LLR, however speech perception is not. It means that acoustic masking effect rather than distortion influences speech perception. In actuality, according to the result of frequency analysis of the speech that people can not answer correctly, level difference between first formant and second formant is about 35dB, and it is similar to result of pure tone masking test(normal hearing subject:36.36dB, hearing impaired subject:32.86dB). Characteristics of masking effect is not similar between normal listeners and hearing impaired listeners. So it is required to check the characteristics of masking effect before wearing a hearing aid and to apply this characteristics to fitting.