• Journal of Korea Multimedia Society
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• v.22 no.8
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• pp.940-949
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• 2019

Classroom response systems (CRS) have been proven to have positive educational effects on student engagement and participation by allowing immediate feedback to both students and instructors. We explore the use of a chatbot and slide widget-based CRS to overcome some of the challenges of existing mobile-based CRSs while retaining their advantages. Our system uses widely available instant messaging services and operates web-based slide widgets that can be seamlessly integrated into instructors' slides to visualize student feedback in various formats. The student survey results indicate that our system is as effective as conventional CRSs in promoting student engagement and participation.

• Journal of Korea Multimedia Society
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• v.12 no.8
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• pp.1142-1154
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• 2009

The brand new type of mobile terminal services are kept being introduced in accordance with the development of mobile communication technology. Among many kinds of mobile application services, the PoC application standard which is using instant messaging service and group calls method with the existing walkie-talkie technology has been finished as the version 1.0 after tremendously active discussion and is being continued to be confirmed as 2.0 and 2.1. The PoC Box, which is discussed for replacing the PoC client and intermediate object as a voice messaging box, is currently being introduced and the biggest issues for PoC Box technology topics include the part of saved informations' processing and effective multimedia contents' transmission in the PoC Box system. In this research, we propose that the PaC client could effectively transmit the media to the end-user by specifying the playback location or range, focusing on the contents and the methods of dynamic controlling for saved media in PoC Box. This paper deals with the way of dynamic controlling method using the RTSP which is appropriate for PoC Box and the effective method for generation, expression, processing of various multimedia contents including audio and video objects.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.581-590
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• 1996

In this paper, we describe the design consideration and the system configuration of the AV service terminal which supports the multiple services simultaneously. We present a service control scheme to support the multiple services in the limited network capability and system hardware capability. The system was developed in the form of an add-on board in a PC system based on N-ISDN BRI. Through the field test in domestic N-ISDN, we confirmed the interoperability and robustness of the system. At present, the developed system can basically support the videoconference service. Also the system can support the multimedia retrieval service, messaging service, fine transmission, and group working environment.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10A
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• pp.1632-1638
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• 2001

본 논문은 MPEG-4 인코딩/디코딩 기반의 멀티미디어 메시징 서비스 시스템 설계 및 구현에 관한 연구인다. 본 시스템은 멀티미디어 스트리밍 기술을 기반으로 한 영상 통신 시스템의 구현을 목표로 했으며, 이 기술은 IP 환경에서 동영상을 기반으로 1:1 통화와 상대방이 부재시 음성과 영상이 통합된 멀티미디어 메시지 데이터를 수신하여 저장하고 상대방에게 전송하는 비 실시간 멀티미디어 메시징 서비스를 제공하는 구조를 제안한다. 또한, 수신된 영상 메시지는 웹 검색기를 사용하여 웹을 통해 확인할 수 있는 인터페이스 프로토콜을 제안하였다. 제안된 구조 및 프로토콜은 Solaris 2.7 및 oracle 8i 환경 하에서 Visual C++를 이용하여 구현하였다.

• Journal of Korea Multimedia Society
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• v.25 no.8
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• pp.1075-1084
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• 2022

Internet of Things(IoT) has become a key available technology for efficiently implementing device to device(D2D) services in various domains such as smart home, healthcare, smart city, agriculture, energy, logistics, and transportation. A lightweight publish/subscribe(Pub/Sub) messaging protocol not only establishes data dissemination pattern but also supports connectivity between IoT devices and their applications. Also, a Pub/Sub broker is deployed to facilitate data exchange among IoT devices. A scalable edge-based publish/subscribe (Pub/Sub) broker overlay networks support latency-sensitive IoT applications. In this paper, we design a hypercube grid quorum(HGQ) for distributed Pub/Sub systems based IoT applications. In designing HGQ, the network of hypercube structures suitable for the publish/subscribe model is built in the edge layer, and the proposed HGQ is designed by embedding a mesh overlay network in the hypercube. As their applications, we propose an HGQ-based mechansim for dissemination of the data of sensors or the message/event of IoT devices in IoT environments. The performance of HGQ is evaluated by analytical models. As the results, the latency and load balancing of applications based on the distributed Pub/Sub system using HGQ are improved.

• Journal of Digital Convergence
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• v.9 no.5
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• pp.225-233
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• 2011

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 a recording system which records voice data of SIP-based Internet telephone's voice calls. It is developed on the linux system and has some features such as audio mixing of two in/out voice channels, live packet sniffing, and the ability to transfer mixed audio files to the log file server. These functions are implemented using various open source softwares. Afterwards, this VoIP recording system will be applied as a base technology to advanced services like a VoIP-based call center system.

• Journal of Broadcast Engineering
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• v.10 no.4 s.29
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• pp.528-539
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• 2005

The H.264 has been adopted as the video codec for various multimedia services such as DMB and next-generation DVD because of its superior coding performance. However, the reference codec of the standard, the joint model (JM) contains quite a few algorithms which are too complex to be used for the resource-constraint embedded environment. This paper introduces very low-complexity H.264 encoding algorithm which is applicable for the embedded environment. The proposed algorithm was realized by restricting some coding tools on the basis that it should not cause too severe degradation of RD-performance and adding a few early termination and bypass conditions during the motion estimation and mode decision process. In case of encoding of 7.5fps QCIF sequence with 64kbpswith the proposed algorithm, the encoder yields worse PSNRs by 0.4 dB than the standard JM, but requires only $15\%$ of computational complexity and lowers the required memory and power consumption drastically. By porting the proposed H.264 codec into the PDA with Intel PXA255 Processor, we verified the feasibility of the H.264 based MMS(Multimedia Messaging Service) on PDA.

• Korean journal of communication and information
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• v.27
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• pp.247-282
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• 2004

The purpose of this study is to examine the mobile phone service usage patterns of Korean teenagers and their motivation to use it, and to explore the relationships between the teenagers' social-psychological characteristics and their trails of mobile phone usage. After reviewing prior theoretical studios, three hypotheses regarding the research questions shown above were generated. Questionnaire study was conducted with 400 high school students in Busan and Ulsan metropolitan areas. They were to answer three categories of questions, such as frequencies of voice calls and text messaging services and the other mobile services, questions asking their social-psychological characteristics, and their motivations for using mobile phone services. Findings show that the teenagers more likely to tend to use voice calls when communicating family members. They tend to avoid those services with high rate of use as multimedia, game, and broadcasting services via mobile phones. The teenagers use mobile phone services for the similar purposes to conventional telephone uses. Therefore, the classical theories showing the alternative purposes or motivations to use conventional telephone usage, which divided the main purposes for phone uses in to two; work/instrumental and socializing/entertaining, proved to be reasonable. The cheap messaging services with texts are popular among the teenagers and are used for socializing/entertaining purposes rather than instrumental/functional purposes. In addition, the teenagers' social-psychological characteristicss are significantly associated with the amount of mobile phone uses. A characteristic of "individual-centeredness" is positively related with non-voice service uses, while "group-centeredness" explains heavy amount of using voice calls and text messaging services. Such characteristics as "immediacy," "directness," "innovativeness," and "other-direction" are positively associated with the frequencies and amounts of mobile phone uses, while "inner-direction" and "tradition-direction" are negatively correlated.

• 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.