• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.508-510
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• 2002

인터넷 수요의 증대에 따라 오디오나 비디오 같은 실시간 전송을 요구하는 멀티미디어 데이터 응용들도 증가하게 되었다. 이런, 멀티미디어 데이터들의 전송은 패킷 손실과 지연을 최소화 하고, 대역폭 상태에 대해 TCP보다 순화된 전송률 조절이 가능한 혼잡제어 기법이 필요하다. Receiver-based 혼잡 제어방식은 network traffic의 변화에 신속히 대응할 수 있으며, 이 방식은 Sender-based 방식에 비해 멀티캐스팅 환경에 적당하다는 장점도 가진다. 본 논문에서는 인터넷 상에서 audio/video 데이터들의 종 단간 Layered Quality Adaptation을 제공하는 receiver-based 혼잡 제어 기법을 소개한다. 이를 통해 사용자들은 보다 좋은 QoS를 제공받을 수 있다.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.21-25
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• 2005

In this paper, we constructed a two-phase spam-mail filtering system based on the lexical and conceptual information. There are two kinds of information that can distinguish the spam mail from the legitimate mail. The definite information is the mail sender's information, URL, a certain spam list, and the less definite information is the word list and concept codes extracted from the mail body. We first classified the spam mail by using the definite information, and then used the less definite information. We used the lexical information and concept codes contained in the email body for SVM learning in the $2^{nd}$ phase. According to our results the spam precision was increased if more lexical information was used as features, and the spam recall was increased when the concept codes were included in features as well.

• IE interfaces
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• v.13 no.3
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• pp.548-555
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• 2000

TAn E-Mail system is one of the most important services for enterprise and electronic commerce end users on the Internet. However, security for an E-Mail service is not satisfied yet, an E-Mail system with security service is definitely required especially in electronic commerce system. In this paper, an E-Mail system with confirmation of e-mail delivery is proposed, The certification of delivery of E-Mail message is not provided in conventional E-Mail systems. The proposed E-Mail system is composed of this certification of delivery and basic security services. The certification of delivery can prove sender's E-Mail message is securely sent to legitimate receivers. The system is designed and implemented by Java Cryptography API.

• Journal of Korea Multimedia Society
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• v.17 no.6
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• pp.681-686
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• 2014

In this paper, we propose a traffic adaptive mechanism that controls the receiver's wakeup periods based on the generated traffic amounts. The proposed control mechanism is designed for military, wild animal monitoring, and forest fire surveillance applications. In these environments, a low-rate data transmission is usually required between sensor nodes. However, continuous data is generated when events occur. Therefore, legacy mechanisms are ineffective for these applications. Our control mechanism showed a better performance in energy efficiency compared to the RI-MAC owing to the elimination of the sender node's idle listening.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.256-259
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• 2007

Multicast and Broadcast Service (MBS) provides flexible and efficient transmission of the same information to multiple users using shared radio resources on WiBro network. The advantage of this service is to achieve the most efficient use of radio and network resources as well as to lessen sender's processing load when sending the same information to multiple users. Though radio resources are saved since a multicast or broadcast transport connection is associated with a service flow, it is hard to change MBS service channel dynamically. In this paper, we propose a Radio Resource Management System (RRMS) for supporting dynamic scheduling of MBS service channels. Results show that our proposed scheme using Radio Resource Allocation Table (RRAT) can efficiently support MBS services by providing dynamic schedule for MBS service channels.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1380-1385
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• 2006

A Pipelined Tone Wakeup(PTW) scheme(1) was proposed to support energy saving and end-to-end delay for sensor networks by providing an asynchronous wakeup pipeline to overlap the wakeup procedures with the packet transmission. But the scheme uses two radios and assumes error-free environments. In this paper, we propose a modified PTW scheme for wireless sensor networks. The proposed scheme is based on the PTW. The difference is that next hop information will be included in the ack packet from receiver node to sender node, So all the other neighbor nodes can stay in sleep mode long enough to save energy. Also ore get enhanced delay performance.

• Journal of information and communication convergence engineering
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• v.15 no.3
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• pp.151-159
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• 2017

Steganography, which is popular as an image processing technology, is the art of using digital images to hide a secret message in such a way that its existence can only be discovered by the sender and the intended receiver. This technique has the advantage of concealing secret information in a cover medium without drawing attention to it, unlike cryptography, which tries to convert data into something messy or meaningless. In this paper, we propose two efficient least significant bit (LSB)-based steganography techniques for designing an image-based steganography system on chip using hardware description language (HDL). The proposed techniques manipulate the LSB plane of the cover image to embed text inside it. The output of these algorithms is a stego-image which has the same quality as that of the original image. We also implement the proposed techniques using the Altera field programmable gate array (FPGA) and Quartus II design software.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3289-3298
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• 1999

E-mail system is the most important service that enterprises and normal users in internet use. However, because a data security is not satisfied yet, and E-mail system with security service is essential. In this paper, We implemented the E-mail system with Certification of Delivery that was not provided in prior mail system with basic security services and can prove that sender's document is properly sent to the intended receipt. And an implementation of the system used Java Cryptography API.

• Journal of Information Processing Systems
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• v.6 no.2
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• pp.147-162
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• 2010

In this paper, we present a fine-grained localization algorithm for wireless sensor networks using a mobile beacon node. The algorithm is based on distance measurement using RSSI. The beacon node is equipped with a GPS sender and RF (radio frequency) transmitter. Each stationary sensor node is equipped with a RF. The beacon node periodically broadcasts its location information, and stationary sensor nodes perceive their positions as beacon points. A sensor node's location is computed by measuring the distance to the beacon point using RSSI. Our proposed localization scheme is evaluated using OPNET 8.1 and compared with Ssu's and Yu's localization schemes. The results show that our localization scheme outperforms the other two schemes in terms of energy efficiency (overhead) and accuracy.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.541-543
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• 2004

TCP does not distinguish between congestion and packet losses due to route change and link failures, which are prevalent in mobile ad hoc networks. So, TCP does not show satisfactory performance in ad hoc networks since it assumes that all packet losses are due to network congestions. In particular, when a route is reestablished it needs to be adaptively determined CWND according to the new route features. In this paper, we proposed CWND adjustment scheme to improve the TCP performance overad hoc networks. TCP sender effectively adjusts CWND by monitoring the network situation using control packets. Simulation results using NS-2 show that the proposed scheme increases TCP throughput compared with those of general TCP.