• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.25-33
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• 2008

Video telephony is a representative service in 3G mobile network. And there have been efforts to improve quality of video telephony service in different fields. In Korea, the leading mobile service provider SKTelecom and KTF service the WCDMA network as 3G mobile network. Now, more than a million people is using the network. In this paper, we study about video telephony over WCDMA network. and propose error minimizing algorithm using cross-layer adaptation between physical layer and video codec. We simulated 3G-324M protocol with MPEG-4 video codec, and simulation results show suggested algorithm improve packet transmission rate for improving quality of video telephony service.

• Journal of Information Technology Applications and Management
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• v.17 no.1
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• pp.107-125
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• 2010

The purpose of this research is to identify the critical factors influencing on the continuous use of video telephony service for mobile devices. An empirical analysis has been performed by using service quality, brand image, price, fun as influencing factors, and satisfaction and commitment as mediating factors. The partial least squares(PLS) methodology with 228 questionnaires has been conducted. The results indicated that brand image, price, and fun were mediated by satisfaction and commitment to have a statistically significant influence on continuous use of video telephony service. Service quality showed a significant effect on continuous use mediated by satisfaction while it did not show any influence through commitment. Based on the results, companies in the communication service industry should consider and focus on the improved brand image, appropriate fees, and individual preferences for fun for the successful marketing activities, and should also maintain amicable relations with their customers.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.361-362
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• 2008

Video quality is degraded by codec and transmission error. By analyses video pattern through NR(no reference) method, we get to aware that telephony video has particular blocking and blurring pattern and NR is suitable for telephony video quality testing. So NR will make contribution to enhancing video quality and monitoring video quality in advance.

• Journal of Information Technology Applications and Management
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• v.17 no.2
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• pp.111-132
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• 2010

Korean telecommunications industry has a large scale market and boasts on high service quality and high technologies enough to provide the mobile video telephony service(the VTS) satisfactorily. For many years, Korean telecommunications companies have been investing enormous amount of money to advertise their VTS widely and to allow their customers to change their cell phones for the 3G(the third generation) devices indispensable for the VTS. However, despite their efforts, the VTS adoption rate in Korea is very low as of January, 2010 and it seems that customers seldom feel the necessity to use. From this viewpoint, it becomes necessary to identify antecedents influencing the intention to use for the VTS empirically. For this purpose, we have proposed several hypotheses from the perspective of the Value-based Adoption Model(VAM). We conducted a survey and found the several factors which influence the value perception of VTS.

• Journal of Industrial Technology
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• v.26 no.B
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• pp.199-206
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• 2006

Internet telephony provides voice communication services with added flexibility for multimedia extension at a lower cost compared to traditional telephone systems. We implemented an internet telephony system as an overlay network without a centralized server, using a distributed hash table (DHT). Compared to the current server-based internet telephony system, our system is fault-tolerant, scalable, and can be flexible extended to various services and advanced to integrated service. To demonstrate the high flexibility of our DHT-based internet telephony system, we made our system cooperate with web servers. Web users can check up others' online stales and establish voice communication sessions to online users at a mouse click. This technology can be applied to more complex services such as multimedia messaging or video conference service.

• 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.

• The Journal of Korea Robotics Society
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• v.5 no.2
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• pp.93-101
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• 2010

This paper presents the system design and implementation of 'Mon-e', the KT's edutainment robot for young children. We paid our special attention to the computer- illiterate young children, and the provision of the physical and friendly human interface of robots. Specifically, the paper focuses on the video telephony and home monitoring service using the Mon-e robot. RFID cards -based calling makes it possible for the computer-illiterate children to make a phone call to their parents. The SIP and DTMF based remote control of the robot enables the search and track of the children. This experimental development shows the potentialities and values of the convergence service of telecommunication and robotics.

• 한국HCI학회:학술대회논문집
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• 2008.02b
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• pp.317-322
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• 2008

WCDMA 의 등장으로 영상통화를 지원하는 휴대폰의 보급은 빠르게 확산되고 있다. 하지만 예상과 달리 사용자들의 실제 영상통화 이용율은 그리 활성화 되지 못하고 있는 실정이다. 본 연구자들은 이러한 현상이 나타나게 된 원인이 영상통화 기능이 단순한 통화기능으로만 활용될 뿐 그 실질적 효용성이 높지 못하기 때문이라 판단하여, 영상 통화를 활성화 시킬 수 있는 방안에 대한 연구를 진행하였다. 오늘날 IT 기반의 서비스 중에 매우 활성화 된 것이 쇼핑 관련 서비스이다. 무선 인터넷과 모바일 환경에서 금융과 통신의 융합이 사회적 화두로 떠오르고, 이러한 이유로 영상통화 기능을 쇼핑과 연계한다면 그 효용성이 매우 커질 것으로 판단하였다. 그리하여 본 연구에서는 사용자 행태 조사을 통해 그들의 needs 를 범주화하고 분석하여 영상통화 쇼핑 서비스 어플리케이션을 도출하였다. 그리고 도출된 어플리케이션의 세부적 절차와 원활한 인터페이스의 설계를 위해 시나리오 형식으로 개방하여 그 형태를 구체화시키고자 하였다.

• Journal of Digital Convergence
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• v.10 no.6
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• pp.259-267
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• 2012

Internet telephony is an Internet service which supports voice telephone using VoIP technology on the IP-based Internet. It has some advantages in that voice telephone services can be accompanied with multimedia services such as video communication and messaging services. Recently, the introduction of smart phones has led to a growth in social networking services and thus, the research and development of Internet telephony has been actively progressed and has the potential to become a replacement for the telephone service that is currently being used. In this paper we designed and implemented an Internet telephony network system which is developed by using Asterisk and open source softwares. It is developed on the linux system and has some features such as VoIP telephony service between SIP phones, voice mail, and call recording. It also supports web-based functions such as SIP users and server system management that is implemented by Apache web server and PHP programs. Afterwards, this system will be applied as VoIP network base technology for small sized companies and organizations. It will paly a role for encouraging companies to use open source softwares.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.235-242
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• 2014

Internet telephony is an Internet service which supports voice telephone using VoIP technology on the IP-based Internet. It has some advantages in that voice telephone services can be accompanied with multimedia services such as video communication and messaging services. In this paper we suggested an Asterisk-based Internet telephony system which can be easily scalable. Most current systems use text files to manage their configuration: SIP users, dialplans, IVR service and etc. But we designed the management system which introduces database tables for efficiency and scalability. It also supports web-based functions developed by using Asterisk, Apache, MySQL, jQuery, PHP and open source softwares.