• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.625-631
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• 2010

In this paper, robustness performance of SNUR message is compared with those of existing ones, RTCM(Radio Technical Commission for Maritime Services) v2 MT(Message Type) 18/19 and MT 20/21 under a poor broadcast condition such as temporary data loss or disconnection We defined the temp oral data loss as 2 second delay and reconnection after disconnection as 7 second latency, and then evaluated its robustness for each latency case by double differentiating the observables. Our result shows that SNUR protocol method can reduce the latency error of the existing RTCM messages by 30~60%. Moreover, a rover using SNUR message, whose latency error is bounded within 1/4 L1 wave length, can figure out its own fixed position continuously in spite of 7 second disconnection, while the other using RTCM message, whose error is larger than half wave length, cannot keep its previous fixed solution.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.615-618
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• 2007

It has able to express digital video/audio data from analog and to broadcast it via improvement of video/audio compression technology and publishing standard of MPEG-2 System. Nowaday many System Operators are provide regular digital broadcasting program to customer with their own access program. To provide access program, two process needs that are creating broadcasting information and remultiplexing it with video/audio data, and this solution is providing with high-cost system only. For this reason, digital access program bas week point to product. In this paper, we designed and implemented Generating PSIP Information System to product digital access program which generate PSIP information via receiving broadcasting information from user, and map PSIP information directly to video/audio data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.7-20
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• 2011

Recently, Proxy Mobile IPv6(PMIPv6) networks have been studied as the mobility management protocol to effectively use limited wireless resources. And the multicasting, which is core technology of the Internet broadcast system such as mobile IPTV, has been discussed mainly based on PMIPv6 network. However, multicasting based on PMIPv6 network causes disconnection of services because it does not solve problems of packet loss during binding and group joining procedure. Hence, we propose a seamless multicast scheme which prevents packet loss in PMIPv6 networks. The proposed scheme achieves lower latency than the existing scheme because it combines binding and group joining procedure, a1so it does not cause about packet losses due to performing buffering. We proved the performance using the simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.258-267
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• 2013

Recently, Proxy Mobile IPv6(PMIPv6) networks have been drawing attention as the mobility management protocol that uses limited wireless resources effectively. And the multicast, which is a core technology of the Internet broadcast system such as mobile IPTV, has been widely discussed mainly based on PMIPv6 network. However, PMIPv6-based multicast cannot support the global mobility directly between different PMIPv6 domains because PMIPv6 is basically designed for local mobility in single PMIPv6 domain. Moreover, PMIPv6-based multicast causes the disconnection of services because it does not solve the packet loss problem during binding and group joining procedure. In this paper, we propose a global mobility scheme that supports the seamless multicast service in PMIPv6 networks. The proposed scheme supports the global mobility due to the addition of extra signalling messages between LMAs. Also, it achieves low latency because it performs fast binding and group joining procedure. We present the simulation results which show that the proposed scheme achieves the global mobility with low latency through the NS-2 simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.2972-2991
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• 2016

WLAN is the best choice in the place where complex network is hard to set up. Intelligent terminals are more and more assembled in some areas now. However, according to IEEE 802.11n/802.11ac, the access-point (AP) can only serve one user at a single frequency channel. The spectrum efficiency urgently needs to be improved. In theory, AP with multi-antenna can serve multiple users if these users do not interfere with each other. In this paper, we propose a user clustering scheme that could achieve multi-user selection through the mutual cooperation among users. We focus on two points, one is to achieve multi-user communication with multiple antennas technique at a single frequency channel, and the other one is to use a way of distributed users' collaboration to determine the multi-user selection for user clustering. Firstly, we use the CSMA/CA protocol to select the first user, and then we set this user as a source node using users' cooperation to search other proper users. With the help of the users' broadcast cooperation, we can search and select other appropriate user (while the number of access users is limited by the number of antennas in AP) to access AP with the first user simultaneously. In the network node searching, we propose a maximum degree energy routing searching algorithm, which uses the shortest time and traverses as many users as possible. We carried out the necessary analysis and simulation to prove the feasibility of the scheme. We hope this work may provide a new idea for the solution of the multiple access problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7C
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• pp.627-636
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• 2012

Recently, XML is used to describe details of service and contents for various fields such as IPTV and digital broadcast services because of it's high readability and extensibility. TV-Anytime's schema and delivery protocol have been especially adopted as basic standards for them, and extended to include their own private functions. However, XML describes documents using text-based method, and this causes to create big documents rather than traditional methods. Therefore, many encoding algorithms have been proposed to reduce XML documents like EXI, BiM, GZIP and fast-info set etc. Although these algorithms shows efficient compression effects for XML documents, but they can't avoid fragmentation degradation during encapsulation steep. This paper proposes an efficient encapsulation scheme of TV-Anytime to avoid fragmentation degradation of encoding effect using common string tables.

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.1-10
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• 2007

This paper describes the development of a network-based passenger information system(PIS) which provides the convenience of the passenger of the train and heightens the effect of the subtitle service, the advertising and the shelter guidance broadcasting against the urgent event. The existing system uses VGA signal distributor in order to broadcast information with image and subtitle and voice guidance. In this paper we improve the existing system by applying the UDP and TCP/IP protocol and use a reference clock to solve a data loss and synchronization problem which occurs in this case. We also developed an XML-based subtitle authoring tool which can edit and play the subtitles with various 3D to improve the automatic guidance broadcasting and advertisement effect according to the operation schedule of the train. The system performance was evaluated through a simulation.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.183-190
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• 2012

Internet Protocol Television(IPTV) is the use of an IP broadband network to deliver television (cable TV type) services to the end user. Traditional telecommunications service providers as well as alternate service providers and Internet service providers can utilize their IP networks (and broadband consumer access) to deliver broadcast TV, Video on Demand (VOD) and other Internet services to the consumer. As digital technologies progress, illegal copy and redistribution of IPTV content become easier and simpler. Therefore it is required to protect IPTV content or service. In this paper, we analyze the security threats and requirements. We also discuss related issues and solutions for IPTV.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.9-19
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• 2004

WLAN (Wireless Local Area Networks) needs error recovery and flow control schemes to support reliable multicast protocol. Limited wireless bandwidth, as well as queuing losses caused by the asymmetric wired/wireless interactions, demands more effective approaches for reducing packet losses. Moreover, since the wireless channel is a shared broadcast medium, if sender receives feedback information simultaneously from several receivers, the feedback delays data frame transmission of forward direction by introducing channel congestion and burden at the sender. Therefore, it is important to minimize the amount of feedback information from receivers. In this paper, we propose an ARS(Adaptive Redundancy Scheme) that combines FEC(Forward Error Correction) using channel state estimation and ARQ(Automatic Repeat Request) both to reduce the amount of feedback information and the number of retransmissions and to guarantee high data reliability in a WLAN multicast environment. Performance of the proposed scheme is evaluated by means of analysis and simulations in AWGN and Rayleigh fading channels. The results show that the proposed scheme reduces the amount of feedback information and the number of retransmissions and guarantees high data reliability, while keeping throughput efficiency similarly with the conventional FEC and ARQ scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.57-65
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• 2007

The overlay multicast that has been recently presented as IP alternative for the IP multicast has been getting much persuasion by the computing power of the hardware and the advancement of the network techniques to enforce Routing in application-level. In an overlay multicast, the system resource and the network bandwidth must be utilized efficiently to service real-time HDTV images. Specifically, the system must consider the delay and the jitter that can be incurred at the application-level. In this paper, we implement a server and a client to broadcast HDTV, in the session composed by the existing overlay multicast protocol. The broadcasting server performs the service using a TV tuner, An HDTV camcorder, and files, clients constituting a multicast group relay the received data to other clients. At this time, the information that the clients report periodically, including their delay and the network state, to the server is used as an important information to maintain an overlay session. The implementation is based on the DirectX and its performance is evaluated by the LAN test bed that has been set.