• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.65-75
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• 2003

The internet telephony service is one of the successful internet application services. VoIP is the key technology for the service to come true. VoIP uses H.323 or SIP as the standard protocol for the distributed multimedia services over the internet environment, in which QoS is not guaranteed. VoIP carries the packetized voice by using the RTP/UDP/IP protocol stack. The UDP-based internet services cause the data transmission problem to the users behind the internet firewall. So does the internet telephony service. The users are not able to listen the voices of the counter-parts on the public internet or PSTN. It makes the problem more difficult that the internet telephony service addressed in this paper uses only one UDP port number to send the voice data of all sessions from gateway to terminal node. In this paper, two schemes including the usage of dummy UDP datagrams, and the protocol conversion are suggested. The implementation of one of the schemes, the protocol conversion, and the performance evaluation are described in detail.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.923-926
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• 2003

인터넷 환경은 고정된 위치에서 사용하는 형태에서 이동하면서 사용하는 형태로 변화하고 있다. PDA 는 올해부터 CDMA 통신 모듈을 탑재한 PDA 폰과 무선랜 기능을 갖춘 이른바 '컨버전스 PDA'의 등장이 본격화할 것으로 보인다. 주요 PDA 업체들은 이미 CDMA 모듈을 장착한 PDA 폰과 무선랜 PDA를 주력 제품으로 내세우고 있다. 이러한 환경에서 VoIP 서비스, 메신저 서비스, 전자칠판을 이용하여 데이터를 공유, 전송하는 등의 공동작업 서비스 등 PDA 중심의 모바일 협동작업 서비스가 가장 유용한 서비스중의 하나로 부각될 것이다. 본문에서는 이러한 모바일 협동작업 서비스를 제공할 수 있는 서버에 요구사항을 정의하고 본문에서 채택한 SIP/SIMPLE 표준에 대하여 설명한 후 이를 기반으로 개발한 모바일 협동 작업 서버시스템에 대한 특징들을 설명한다.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.130-133
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• 2001

VoIP(voice over internet protocol) technology is based on IP protocol. The IP protocol can be involved in two types of communication: unicasting and multicasting. Unicasting is the communication between one sender and one receiver. It is one-to-one communication. Multicasting is one-to-many communication. So that, many receivers can get same data from one sender simultaneously. and, the different protocol are proposed for VoIP; H.323, SIP and MGCP. MGCP is perfect server-client protocol, so MGCP is very attractive VoIP protocol to ISP. This paper uses MGCP and offers modified MGCP for conference call. So that, Modified MGCP is compatible to MGCP, and supports conference call using IP-multicast.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1602-1608
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• 2013

PoC (Push-to-Talk over Cellular) provides one-to-one as well as one-to-many communications with VoIP technology based on SIP over cellular networks. According to above property, PoC is considered as perscrptive technology for public protection for disaster relief networks. For this networks, group communication is the essential function. However, since current standardization process takes into general scenarios account without any consideration for mentioned networks, it have some problems in the point of adaptability. To solve above problem, in this paper, we propose how to reduce the overhead on the PoC server to reduce the transmission delay. Simulation results are shown to evaluate the improved performance.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.514-520
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• 2018

Presence service provides various information about users such as locations, status of on/offline and network access methods, and number of presence resources required by each users increases largely in mobile environment. Therefore an effective method which can reduce load of presence servers is needed. In this paper, a large scale distributed presence service system which can distribute effectively total presence system load of presence servers using message control session has been presented. This large scale distributed presence service system provides various presence information for massive volumes of users. In this study, a new message control session architecture which can dynamically distribute loads of the presence servers to multiple servers has been presented, and a new presence information data architecture for controlling load of the presence servers has been designed. In this architecture, each presence server can exchange current load level in real time to get variance of the total system load change according to user numbers, and can distribute system load to maintain load level of each server evenly. The performance of the proposed large scale distributed presence service system has been analysed by experiments. The results has been showed that average presence resource subscription processing time reduced from 42.6% to 73.6%, and average presence notification processing time reduced from 37.6% to 64.8%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8B
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• pp.730-735
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• 2006

This paper proposes a media key distribution scheme for lawful interception in secured VoIP systems. A problem of the current US or EU standards for lawful interception is that they do not provide a mechanism for collecting keys used for encrypting media streams between two end points. In the proposed scheme, dual encryption was applied on the media keys using two shared secrets: one between the ISP AAA server and user agent, and the other between the TSP registrar and user agent. Only the lawful agency with court warrant can collect both keys from the service providers. This scheme can still provide a privacy by preventing the misusage of the keys by the service providers.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.501-508
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• 2003

VoIP that conveys voice in internet is getting into the spotlight as means to alternate existing PSTN in corporation as well as users. Current VoIP is furnishing voice efficiently, but it needs to support various services for VoIP acceleration. IETF is developing CPL standard which is call processing language for supporting various services. User has to store script to specific server for the use of CPL, therefore it is required client to support CPL. This paper describes about design and implementation of SP-based CPL client for various services. The CPL client was implemented using LINUX 2.4.x, C, and GTK1.2.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.752-757
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• 2016

Machine to Machine (M2M) communications is communications between a business application and devices via a communication network without any direct human interaction. The aim of our research is to connect any M2M device with an M2M AS (Application server) through an IMS (IP Multimedia Subsystem) Network Core using a M2M Gateway, in order to develop an M2M Horizontal Services Platform over IMS. An IP Multimedia Subsystem (IMS) is an architectural framework defined by the wireless standards body of the 3rd Generation Partnership Project (3GPP) for delivering IP multimedia services to mobile users. This paper shows the design and implementation of a Horizontal M2M Network Services Platform over an IP Multimedia Subsystem (IMS) using the Message Session Relay Protocol (MSRP). We summarize the protocols and architectures that formed the basis for the creation of our architecture. We provide a detailed description of our architecture design, describing the call flow of the proposed architecture and the entities operating in each process. We also describe the design and implementation process detailing the different tools used, explaining the selection of each component and its importance; also how we designed and implemented the M2M gateway, M2M Application Server, Open IMS Core, business application and M2M devices.

• Journal of Internet Computing and Services
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• v.13 no.2
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• pp.21-32
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• 2012

We develop architecture of a virtual aggregation gateway (VAG) which enables composite application streaming based on N-Screen-as-a-Service (NaaS) using cloud computing in thin-client environment. We also discuss the problem of server computing burden in large scale multi-client case for screens sharing with composite application streaming over the internet. In particular, we propose an efficient Framework of N-Screen Session Manager which manages all media signaling that are necessary to deliver demanded contents. Furthermore, it will provides user with playback multimedia contents method (TV Drama, Ads, and Dialog etc) which is not considered in other research papers. The objectives of proposing N-Screen Session Manager are to (1) manage session status of all communication sessions (2) manage handling of received request and replies (3) allow users to playback multimedia contents anytime with variety of devices for screen sharing and (4) allow users to transfer an ongoing communication session from one device to another. Furthermore, we discuss the major security issues that occur in Session Initiation Protocol as well as minimizing delay resulted from session initiations (playback or transfer session).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.129-132
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• 2003

In this paper, which sees the Strong-ARM SA1110 it used the main CPU and RTP in VoIP system. It will be able to apply the information communication field it embodied. It used the Tynux_box2 with the hardware side and it composed a VOIP system. And it used the RTP which is a real-time protocol in software control portion. The development environment of the paper that used the Target board and a Linux PC for connection used the RS-232C, USB connection, Ethernet LAN. The VoIP the environment for a communication used the wave file in the substitution which changes analog signal with the digital signal. And For the communication of the both sides it used the socket. This paper explained the fact that against a general technique from the operation of VoIP system. Using the Embedded linux development board which explained an operational process of the RTP protocol.