• Journal of Digital Convergence
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• v.12 no.2
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• pp.335-341
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• 2014

To play the networked video contents in a client's mobile device in real time, the contents should be delivered to it by the contents server with streaming technology. Generally, in a server-client based commerce model, the server is in charge of both the authentication of the paid customer and distribution of the contents. The drawback of it is that if the customers' requests go on growing rapidly, the service quality would be degraded results from the problems of overloaded server or restricted network bandwidth. On the contrary, in P2P based networks, more and more the demand for service increasing, the service quality is upgraded since a customer can act as a server. But, in the P2P based network, there are too many servers to manage, it's possible to distribute illegal contents because the P2P protocol cannot control distributed servers. Thus, it's not suitable for commercial purposes. In this paper, the dymanic group authentication scheme is proposed which is suited to P2P based applications. The proposed scheme consists of group based key generation, key update, signature generation and verification protocols. It can control the seeder's state whether the seeder is joining or leaving the network, and it can be applied to hybrid P2P based commerce model where sales transactions are covered by the index server and the contents are distributed by the P2P protocol.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.18-26
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• 2012

As the performance of the next-generation broadband wireless networks is dramatically enhanced, various services (i.e., education, video conferencing, online games, etc.) have been provided to users through a smart mobile platform. Since those services are usually provided by using the centralized architecture, it is difficult for a lot of users to provide the scalable communication service with regard to traffic management. To solve these problems, we have proposed an architecture of P2P-based group communication management scheme using smart mobile device. More specifically, we design the group management protocol and algorithm for the group member management and the traffic management. By using these methods, the mobile multimedia streaming service can be provided with scalability. In order to verify the performance of the proposed scheme, we have mathematically analyzed the performance in terms of the average transmission delay and bandwidth utilization.

• 대한공업교육학회지
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• v.32 no.2
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• pp.199-216
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• 2007

Stream Control Transmission Protocol(SCTP) is a transport layer protocol to support the data transmission. SCTP is similar to Transmission Control Protocol(TCP) in a variety of aspects. However, several features of SCTP including multi-homing and multi-streaming incur the performance difference from TCP. This paper highlights the data transfer during the initial slow start phase in SCTP congestion control composed of slow start phase and congestion avoidance phase. In order to compare the mean transfer time between SCTP and TCP, we experiment with different performance parameters including bandwidth, round trip time, and data length. By varying data length, we also measure the corresponding initial window size, which is one of factors affecting the mean transfer time. For the experiment, we have written server and client applications by C language using SCTP socket API and have measured the transfer time by ethereal program. We transferred data between client and server using round-robin method. Analysis of these experimental results from the testbed implementation shows that larger initial window size of SCTP than that of TCP brings the reduction in the mean transfer time of SCTP compared with TCP by 15 % on average during the initial slow start phase.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.511-514
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• 2012

IPTV는 기술적으로 TV에 PC적 기능이 더해지고 인터넷 프로토콜(IP)을 통해 인터넷과 연결되는 서비스로, 국내 초고속인터넷의 속도가 VDSL, 광랜과 같은 서비스의 등장으로 최대 100Mbps에 이르러 동영상 콘텐츠의 실시간 스트리밍 서비스가 가능한 환경이 구현되었다. IPTV 도입을 통해 산사건 방송, VOD 등의 기본적인 서비스뿐만 아니라, 양방향 광고, IPTV 민원발급 및 IPTV 공공서비스 제공 등 다양한 응용서비스의 개발 및 활성화를 기대하였다. 또한 IPTV를 통해 유료방송의 경쟁을 촉진시키고 케이블TV의 디지털 전환을 촉진시킴으로써 시청자들의 복지를 향상시킨다는 취지도 함께 있었다. 정량적으로는 IPTV가입자가 2012년에 이르러 보수적으로 290만가구, 낙관적으로는 450만 가구에 이를 것으로 예상하였으며, 관련 시장규모도 동년도에 약 7,515억원에 이를 것으로 전망하였다. 하지만, 2011년 말이 이미 450만 가입자를 돌파하고 2012년 8월 500만 가입자를 유치하면서 IPTV 서비스는 본격적인 mass market을 형성해 나가고 있다. IPTV 시장이 확대해 나가면서 유료방송 가입가구 수도 증가하였는데, 도입당시인 2008년 말 1,740만 가구가 유료방송에 가입하여 104%의 보급률을 보였으나 2011년 6월말 현재 가구수 대비 유료방송 가입자구수는 127%로 증가하였다. 이렇게 IPTV서비스 시장이 확대되고는 있으나, 정부의 신규 서비스에 대한 과도한 요금규제, IPTV와 경쟁하는 케이블방송사(SO) 계열의 콘텐츠 사업자(CP)들의 방송채널 공급거절 및 지상파 방송사의 과도한 재전송 대가, 전국 권역사업자인 IPTV에 대한 권역별 가입자점유율 규제, IPTV의 차별성으로 내세웠던 T-Commerce 및 양방향 광고에 대한 규제는 앞으로 개선해 내가야할 과제이다. 이에 본고는 IPTV의 시장성과를 조망하고, 시장의 지속성장을 위해 필요한 제도개선 방향을 살펴보았다.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.4
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• pp.141-146
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• 2015

Data have been increased enormously due to the development of IT technology such as recent smart equipments, social network services and streaming services. To meet these environments the technologies that can treat mass data have received attention, and the typical one is Hadoop. Hadoop is on the basis of open source, and it has been designed to be used at general purpose computers on the basis of Linux. To initial Hadoop nearly no security was introduced, but as the number of users increased data that need security increased and there appeared new version that introduced Kerberos and Token system in 2009. But in this method there was a problem that only one secret key can be used and access permission to blocks cannot be authenticated to each user, and there were weak points that replay attack and spoofing attack were possible. Hence, to supplement these weak points and to maintain efficiency a protocol on the basis of group key, in which users are authenticated in logical group and then this is reflected to token, is proposed in this paper. The result shows that it has solved the weak points and there is no big overhead in terms of efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10B
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• pp.909-918
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• 2006

Recently, the qualities of the call and QoS of data service in mobile wireless IP networks inclusive of internet wired networks are very challenging issues. IntServ, DiffServ and MPLS model for supporting QoS in wired networks are representative models which are investigated generally up to now. While, MIPv4(Mobile IPv4) and MIPv6 are proposed to support mobility management for mobile wireless internet networks. But, MIPv4 and MIPv6 based UDP and TCP/IP protocol have many issues to be solved like efficient QoS and frequent handover management. In this paper, we propose a efficient management platform to support seamless data services and end-to-end QoS management in IP-based wireless mobility environments using transport layer protocol, SCTP which support multi-homing and multi-streaming. We used SCTP protocol and IntServ technology for end-to-end communications to support multi-homing and seamless QoS management in the IP-based mobile wireless networks.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.6
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• pp.565-570
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• 2015

In this paper, we implemented the smart door lock system that control remotely devices using the concept of internet of things. Internet of things is intelligent system that can help devices to communicate with people and devices. And recently internet of things is getting attention because of advance of hardware technology and big data. The smart doorlock system based on internet of things used raspberry pi, sensor and doorlock. Using the smart phone, doorlock can be controlled from the raspberry pi server. And the user can identify some people that is in front of doorlock. also user can check around of doorlock in realtime using the raspberry pi camera.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.304-309
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• 2004

Recently, the needs for multimedia stream such as digital audio and video in the Internet has increased tremendously. Unlike TCP, the UDP protocol, which has been used to transmit streaming traffic thorough the Internet, does not apply any congestion control mechanism to regulate the data flow thorough the shared network And it leads to congestion collapse of the Internet and results in long-term transmission delay. To avoid any adverse effect on the current Internet functionality, a now protocol of modification or addition of some functionality to perform congestion control and to reduce huge transmission delay in transmitting of multimedia stream are in study. TCP-friendly congestion control mechanism is classified into two : one is window-based congestion control scheme using general window management functionalities, the other is rate-based congestion control scheme using TCP modeling equation. In this paper, we propose an algorithm for improving the transmitting rate on a hybrid TCP-friendly congestion control scheme combined with widow-based and late-based congestion control for multimedia stream. And we also simulate the performance of improved TEAR implementation using NS. With He simulation results, we show that the improved TEAR can provide better fairness and lower rate fluctuations than TCP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.899-915
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• 2003

Delivering rich and continuous media contents robustly over a wide range of network conditions of the wired/wireless Internet is a highly challenging task. To address this challenges, the continuous media applications at the edge of network has become more and more adaptive while the best-effort Internet is slowly progressing towards improved networking services. That is, the role of network adaptive media delivery, which dynamically links the quality demand of application contents to the underlying networking services, has become more crucial. In this paper, we will first review the required network adaptation functionalities seen from the application side: congestion control / rate control, error control, and synchronization / adaptive playout. Then, we start the coverage of networking support issues that helps the realization of network adaptive media streaming - from network support and protocol support toward consolidated support via middleware. Finally, we propose a dynamic network adaptation framework that efficiently leverages its awareness of both media application (including contents) and underlying networking support.

• 대한공업교육학회지
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• v.33 no.2
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• pp.287-299
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• 2008

HTTP is one of the most widely used protocols of the WWW. Currently it uses TCP as the transport layer protocol to provide reliability. The HTTP uses separate TCP connection for each file request and adds unnecessary head-of-line blocking overhead for the file retrieval. The web application is short sized and affected by the increased handover latency of TCP in wireless environment. SCTP has attractive features such as multi-streaming and multi-homing. SCTP's multi-streaming and multi-homing avoid head-of-line blocking problem of TCP and reduce handover latency of TCP in wired and wireless environment. Mean response time is the important measure in most web application. In this paper, we present the comparison of mean response time between HTTP over SCTP with that of HTTP over TCP in wired and wireless environments using NS-2 simulator. We measured mean response time for varying packet loss rate, bandwidth, RTT, and the number of web objects in wired environment and mean response time and packet loss rate for varying moving speed and region size in wireless environment. Our experimental result shows that SCTP reduces the mean response time of TCP based web traffic.