• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.510-520
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• 2014

By adopting the MAC(Media Access Control) protocol which enables to pack multiple MPDUs(MAC-level Protocol Data Units) into a single PPDU(Physical Layer Protocol Data Unit), IEEE 802.11n WLAN supports high throughput. Up to now, there have been a lot of existing channel information-based A-MPDU schemes dynamically determining the number of MSDUs according to the wireless channel condition information which is sent from the receiver to sender. However, the channel information-based scheme has a serious drawback having a high system overhead due to the frequent channel feedback information. To reduce the system overhead, the proposed BA-base dynamic A-MPDU scheme simply chooses the number of MSDUs to be retransmitted by not the frequent channel feedback information but the BA signal representing whether MPSUs belonging to the A-MPDU are received or not. Through NS-2(Network Simulator-2), we found that the proposed scheme had higher throughput and lower packet error rate than the existing fixed A-MPDU scheme.

• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.502-509
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• 2014

Broadcast encryption is a cryptographic primitive that allows a sender to securely transmit a message to a set of receivers. The most influential broadcast encryption system was proposed in 2001 by Naor, Naor, Lotspiech, based on binary trees and the Subset Difference (SD) method. In 2006, Jang, Nyang, and Song suggested a new broadcast encryption system that can reduce transmission rate by 50% compared to the SD method, by introducing the so-called '2-SD' method. Their result was later given the registration of a patent in Korea (registration number: 100879083). Unfortunately, however, this paper shows that Jang et. al.'s broadcast encryption system is not secure against collusion attacks that are considered as being the basic security requirement in designing broadcast encryption.

• Proceedings of the Korea Contents Association Conference
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• 2004.11a
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• pp.516-530
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• 2004

With the advent of knowledge-based society where knowledge generates power, the importance of information is growing than ever before. However, it is not easy to find necessary information in time. Collecting, processing and disseminating valuable information is getting more and more important. If those information include scientific and technical issues, it is more difficult to connect the sender and receiver, provider and consumer and also creates various factors and situation. This study aims to provide an application method of IMC(Integrated Marketing Communication) Strategy for efficient information services of science and technology which is one of KISTI's major functions. An analysis was proceeded in 3 categories with provider and receiver, and medium and message. The current problem in system was reviewed through each analysis and a feasible plan for the realization of IMC Strategy in future is proposed.

• The Journal of the Korea Contents Association
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• v.20 no.5
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• pp.500-512
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• 2020

This research aimed to verify organizational culture of resort underlying bottom of organization and shared by employees. Healing-seeking and life style oriented experiences are in prevailing recently, which resort industry insomuch as presumably held from its origin. Unfortunately, it is also widely recognized that resort lost its entity, blurring business domains with hotel industry or yielding integrated resort by imitating theme park. In order to probe organizational culture, in-depth interview with 16 resort experts conducted in resort setting, prepared by Gremeis actant model which is effective in finding myth(story) structure of interviewees. Firstly, interviewer matched six actants with resort business involving-group and asked interviewee to metaphor freely based on 3 night resort experiences. Results showed that sender, receiver, subject, object, helper and opponent were matched with resort, visitor, company, product & service, supporters, and opponent group in orderly manners and also interviewees made each actant into metaphor as healing, patient, medical doctor, medicine, helper and charlatan, respectively. Significance and limitation of research were included in the end of article.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6845-6848
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• 2014

This paper proposes a system design of IDS for detecting and defending against DDoS attacks on a network. The proposed system has three parts; the Alert, Attack Analyzer and Defense agent. When the server resource was reduced too much by incoming traffic, the Alert Agent sends message and traffic information to the Attack Analyzer. The message and traffic to the Attack analyzer include only the sender & receiver address and packet numbers for minimizing the overload of Attack Analyzer. Message Received Attack Analyzer investigates the Message. If the pattern of traffic is the same as the DDoS Style, the Analyzer sends a message to the Defense Agent to block that traffic. In this system, at the serious state of the server-down, the Attack analyzer uncovers the DDoS Attacker and send a message to the Defense Agent to block that traffic. This works for server reactivation as soon as possible.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.721-727
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• 2016

In this paper, in order to resolve the problem of reduction for D2D (device to device) advertisement dissemination efficiency of conventional dissemination algorithms, we here propose several clustering algorithms (modified single linkage algorithm (MSL), K-means algorithm, and expectation maximization algorithm with Gaussian mixture model (EM)) based advertisement dissemination algorithms to improve advertisement dissemination efficiency in D2D communication networks. Target areas are clustered in several target groups by the proposed clustering algorithms. Then, D2D advertisements are consecutively distributed by using a routing algorithm based on the geographical distribution of the target areas and a relay selection algorithm based on the distance between D2D sender and D2D receiver. Via intensive MATLAB simulations, we analyze the performance excellency of the proposed algorithms with respect to maximum number of relay transmissions and D2D user density ratio in a target area and a non-target area.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.154-163
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• 2008

In a mobile broadband wireless access (MBWA) network, many users access a base station (BS), which relays data transferred from high-speed wired network to low-speed wireless network. For this difference of their data rate, a BS suffers from the lack of its buffer space when many users run multiple applications at the same time, and thus packet losses occur. TCP, which guarantees end-to-end reliability, is used as transport protocol also in wireless networks. But TCP lowers their transmission rate incorrectly and frequently whenever packet losses occur. And they increase their transmission rate differently with each other; finally TCP throughput of each TCP flow varies largely, and then TCP fairness goes worse. In this paper, a scheme that controls packet transmission rate adaptively according to TCP flows' transmission rate, that prevents buffer overflows at BS, and that guarantees TCP fairness at a certain degree is proposed. As it is analyzed by simulations, the proposed scheme enhances TCP fairness by maintaining TCP throughput of each TCP sender similarly with each other.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.921-926
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• 2009

After the scientific development of human history, numerous images have been developed and expanded in digital media as a communication tools. Image digital media make communication closer between sender and receptor. The image digital media which has been developed with the change of technology and media transformation have shortened visual information transportation and the time as well by combining the sense of visual and audio. Motion graphic field has been emerged as the type of image digital media development. The development of motion graphic make possible for the expressive effect and dynamic image technique which is impossible by the existing media type. Especially, it is applied to various field such as the title of movie, TV program, and advertise or music video etc. These image expression techniques are stimulating acceptor's emotion to take a role of emotion communication function also. This study aims to find the characteristics motion graphic of which how influence as an effective communication tool as important role to the receptors, and the examine the effect and application of motion graphic to the receptors as a emotion communication tool by case study.

• The Transactions of the Korea Information Processing Society
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• v.4 no.12
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• pp.3139-3149
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• 1997

E-mail system has been widely used for information transmission. As multimedia technologies are developed, many Internet services support multimedia. E-mail system only transmits 7bit ASCII data using simple mail transfer protocol(SMTP) specified in RFC 821. E-mail system can't support the authoring and the transmission of multimedia data. In this study multimedia mail authoring system has been designed and implemented in order to provide message integration. Multimedia messages can be authored and transformed into text types with this system. Transformed messages are transmitted from sender's mail transfer agent (MTA) to receiver's MTA by means of SMTP. Messages can be authored in hypertext markup language (HTML) including text, image, audio and video. This system provides integrated messages which consist or various media. BASE64 Encoding method is used in order to transform multimedia messages into text types. Received mails are managed by multimedia user agent (MUA) which is proposed in this study. Convenience for user is improved in this system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.583-588
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• 2004

For the Explicit Multicast (Xcast) scheme, we propose a scheme that provides dynamic group membership and supports a large, dense multicast group. To do so, we use a hierarchical joining mechanism, where a domain agent joins a group on behalf of hosts. In our scheme, a sender transmits multicast packets to a domain agent, and then the agent forwards the packets to receivers in a domain. A host can join or leave a group at my time via the domain agent. Thus, a destination field of the Xcast header has addresses of domain agents instead of hosts. Simulation results show that our scheme can reduce more the Xcast header size and cost in forwarding packets than the Xcast, especially for a large multicast group. Like traditional multicast schemes, our scheme can support large multicast group members.