• Journal of Korea Multimedia Society
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• v.14 no.11
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• pp.1431-1437
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• 2011

This paper proposes a novel watermarking algorithm that protects digital copyrights and is robust to attacks. Watermarks are embedded in the subband including the significant part of the signal such as a pitch. Generally, the subband containing the pitch has the biggest energy. In order to find this subband, wavelet packet transform is used to decompose the subbands and their energy are calculated. The signal of the selected subbands is transformed in frequency domain using FFT. The watermarks are embedded using QIM for samples higher than a certain threshold. The blind detection uses the Euclidean distance. The proposed method shows less than 5% BER in the audio watermark benchmarking.

• 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.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.358-366
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• 2010

In the wireless network the congestion and delay occurs mainly when there are too many packets for the network to process or the sender transmits more packets than the receiver can accept. The congestion and delay is the reason of packet loss which degrades the performance of multimedia streaming. This paper proposes a novel transmission rate monitoring-based optimization mechanism to optimize packet loss and to improve QoS. The proposed scheme is based on the trade-off relationship between transmission rate monitoring and overhead monitoring. For this purpose this paper processes a source rate control-based optimization which optimizes congestion and delay. Performance evaluated RED, TFRC, and the proposed mechanism. The simulation results show that the proposed mechanism is more efficient than REC(Random Early Detection) mechanism and TFRC(TCP-friendly Rate Control) mechanism in packet loss rate, throughput rate, and average response rate.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.21-28
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• 2016

This paper presents a cooperative transmission scheme for underwater acoustic sensor networks to improve packet transmission rate and reduce energy consumption. Source node transmits duplicated information relayed by distributed antennas called a virtual antenna array. Destination node combines that information to reduce packet error rate. The suggested cooperative scheme enhances the reliability by providing high diversity gains through intermediate relay nodes to overcome the distinct characteristics of the underwater channel, such as high transmission loss, propagation delay, and ambient noises. It is suggested that the algorithm select destinations and potential relays from a set of neighboring nodes that utilize distance cost, the residual energy of each node and local measurement of the channel conditions into calculation. Simulation results show that the proposed scheme reduces average energy consumption, response time, and increases packet delivery ratio compared with the SPF(Shortest Path First) and non-cooperative scheme using OPNET Moduler.

• Journal of Internet Computing and Services
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• v.16 no.2
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• pp.27-40
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• 2015

Inferring firewall policy is to discover firewall policy by analyzing response packets as results of active probing without any prior information. However, a brute-force approach for generating probing packets is unavailable because the probing packets may be regarded as attack traffic and blocked by attack detection threshold of a firewall. In this paper, we propose a firewall policy inference method using an efficient probing algorithm which considers the number of source IP addresses, maximum probing packets per second and interval size of adjacent sweep lines as inference parameters to avoid detection. We then verify whether the generated probing packets are classified as network attack patterns by a firewall, and present the result of evaluation of the correctness by comparing original firewall policy with inferred firewall policy.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.4
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• pp.216-223
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• 2013

As the fast growth of using Internet, the requests of clients having different types and pressing loads on the server have been increased in World Wide Web. Thus the interesting issue is how to measure the real capacity of a Web Server. There have been much recent studies about measuring the capacity of web server. But the cause of Server response time delay is not just server itself but also network packet loss. To measure the practical capacity of web server, we generate scalable clients using Posix Thread, transport packets which were generated by scalable clients to the server using UDP and receive the packets which were the remain packet from network packet loss using TCP. In this paper, we propose a method to measure the practical capacity of a web server using the Scalable Clients based on Posix Thread and the transport on Application level.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.1011-1016
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• 2020

Rapid change in network topology in high-speed VANET(: Vehicular Ad Hoc Network) is an important task for routing protocol design. Selecting the next hop relay node that affects the performance of the routing protocol is a difficult process. The disadvantages of AODV(: Ad Hoc On-Demand Distance Vector) related to VANET are end-to-end delay and packet loss. This paper proposes the AAODV (Advanced AODV) technique to reduce the number of RREQ (: Route Request) and RREP (: Route Reply) messages by modifying the AODV routing protocol and adding direction parameters and 2-step filtering. It can be seen that the proposed AAODV reduces packet loss and minimizes the effect of direction parameters, thereby increasing packet delivery rate and reducing end-to-end delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.243-246
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• 2003

The design of router that converts IP packets from IPv4 network to IPv6 network using embedded Linux toolkit based on processor is presented. As an address transition platform, IPv6 module is transplanted to Linux using processor and the experiment was done with IPv4 and IPv6. In order to build the test network, it is constructed with Tunneling mechanism of IPv4 and IPv6 network. The packet value is obtained about 2$\mu$sec on average a 2 hops on the ICMP ping6.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1505-1508
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• 2004

반응적 Ad hoc 라우팅인 AODV의 경로관리는 노드 이동, 노드 혼잡 등의 원인으로 지정시간 내에 응답을 하지 못할 경우 경로 단절을 감지한 뒤 경로복구 과정을 수행한다. 그러나 이러한 경로관리 방법은 능동적이지 못하여 단절 후 경로 재 설정까지 시간 지연이 발생하기 때문에 신속한 경로 복구에 어려움이 있다. 본 논문에서는 기존 AODV에 대한 추가적인 제어 패킷을 발생시키지 않고 경로를 구성하고 있는 이웃노드 Hello 패킷의 수신 시간차를 이용하여 경로 불안정을 예측, Expanding Ring Search 알고리즘을 활용한 효율적인 경로관리 기법을 제시한다.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.1_2
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• pp.11-19
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• 2001

근래에 들어, 백플레인 버스를 기반으로 하는 멀티프로세서 시스템의 프로세서간 통신에도 TCP/IP와 같은 표준 네트워크 프로토콜을 이용하여 표준 MAC 계층을 구현하는 것이 일반적이다. 본 논문은 이러한 MAC 에뮬레이션 기반 버스 네트워크상에서 내장형 실시간 은용을 지원하기 위한 최악 응답 시간 분석법을 제시한다. 본 논문의 분석법은 구체적으로 MAC 에뮬레이션 방법의 하나인 ANSI BusNet 프로토콜을 대상으로 진행된다. 각 실시간 태스크를 주기, CPU 시간, 종료시한, 메시지 패킷 개수로 모델링하고 스케쥴 가능성, 즉 주어진 종료 시한 내에 작업을 완료할 수 있는지의 여부를 검사하는 수식을 유도한다. 이를 위해 물리적인 버스 특성을 고려한 버스 전송 모델을 제시하고, 버스 중재 방식과 버스 하드웨어의 캐슁 지원 여부에 따른 스케쥴 가능성을 분석한다. 또한 본 논문에서는 실험을 통해 블록 전송이 실시간 통신 성능에 미치는 영향을 살펴본다. 비록 본 논문의 분석법이 BusNet에 기반하여 개발되었지만, BusNet이 대부분의 백플레인 하드웨어가 지원하는 기본적인 기능만을 가정하고 있으므로, 본 논문의 분석법은 다른 종류의 백플레인 네트워크 프로토콜에도 쉽게 적용될 수 있다.