• Annual Conference of KIPS
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• 2018.05a
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• pp.267-270
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• 2018

구제역으로 인하여 국내 축산업계 및 관련 산업분야는 매년 막대한 피해를 입고 있다. 구제역과 관련한 다양한 학술적 연구들이 현재 진행되고는 있으나, 구제역의 발병에 따른 사회적 파급효과에 관한 공학적 분석 연구는 매우 제한적이다. 본 연구에서는 구제역에 관한 일반 시민들의 감성적 반응을 텍스트 마이닝 방법론을 사용하여 분석하는 체계적인 방법론을 제안한다. 제안하는 시스템은 먼저, 트위터에 게시된 트윗 중 구제역과 관련된 데이터를 수집한 후, 감성사전을 기반으로 극성탐지 과정을 거친다. 둘째, 토픽 모델링의 대표적인 기법 중 하나인 LDA를 활용하여 트윗으로 부터 키워드들을 추출하고, 추출된 키워드들로부터 극성별 동시출현 키워드 네트워크를 구성한다. 셋째, 키워드 네트워크을 통해 각 구간별 구제역의 사회적 파급효과를 분석한다. 사례 분석으로써, 2010년 7월부터 2011년 12월까지 국내에서 발생한 구제역에 관한 일반 시민들의 감성적 변화를 분석하였다.

• Annual Conference of KIPS
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• 2008.11a
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• pp.1215-1218
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• 2008

IEEE 802.15.4 기반의 무선 센서 네트워크는 다양한 종류의 센서들로 구성된다. 이러한 센서들은 각각 다양한 주기들로 중심 노드에게 데이터를 전송하고자 한다. 슈퍼프레임마다의 주기적인 전송을 위해 IEEE 802.15.4에서는 GTS(Guaranteed Time Slot) 메커니즘을 제공한다. 하지만 하나의 센서 네트워크에서 슈퍼프레임 길이는 모두 동일하기 때문에 이보다 긴 주기를 갖는 센서들은 GTS를 할당받고도 데이터를 전송하지 않는 경우가 발생할 수 있다. 때문에 IEEE 802.15.4의 GTS 메커니즘에서는 낮은 사용 효율의 문제가 발생한다. 본 논문은 이러한 문제를 보완하고자 주기적 GTS 할당 방법(PGTS: Periodic Guaranteed Time Slot)을 제안한다. 주기적 GTS 할당 방법에서는 단말들이 GTS 요청 시 자신의 데이터 전송 주기를 PAN 코디네이터에게 보고하고, PAN 코디네이터는 이를 고려하여 단말의 주기에 따른 슈퍼프레임에서만 GTS 구간을 할당한다. 이를 통해 주기적 GTS 할당 방법은 기존 GTS 할당 방법보다 대역의 낭비를 줄여 GTS를 효율적으로 사용가능하도록 하고 더 많은 수의 단말들에게 GTS를 배정할 수 있게 한다. 본 논문에서는 시뮬레이션 결과를 통해 주기적 GTS 할당 방법이 IEEE 802.15.4의 GTS 할당 방법보다 효율적이며 더 많은 수의 단말에게 GTS를 할당할 수 있음을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.11
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• pp.924-933
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• 2013

In this paper, we propose a modeling of the broadcasting in the IEEE 802.11p MAC protocol for the VANET(Vehicular Ad hoc Networks). Due to the fact that the beacon message which is needed for the safety services is shared via broadcasting, the analytical modeling of the broadcasting is crucial for the optimum design of the services. Two characteristics specific to the IEEE 802.11p are reflected in the modeling; the time limited CCH interval caused by the channel switching between the CCH and SCH, and no retransmission of the broadcasted messages. In the proposal, we assumed no restriction on the moment of generation of the beacon messages. We allow the messages to be generated and broadcasted within the whole CCH interval. Simulation results prove the accuracy of the proposed modeling. Noticeable improvements are also observed in terms of the performance indices such as the successful delivery ratio, transmission delay, and the variation of the delay.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.25-34
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• 2006

In this paper, we propose the new Cellular Ethernet System that supports faster handovers than IP layer handover scheme for WiBro Networks and analyze the performance of the proposed scheme. In WiBro Networks, it is very important for service providers that supports fast handovers for mobile users who want superior service. But in case of Mobile IPv6, which supports IP layer handovers, there exists very long latency for detecting movement and duplicated IP address. And besides, handovers in wired area must be carried out after completing handovers in wireless area. So, Mobile IPv6 cannot provide superior service to mobile users. To remedy these problems, we here propose the new Cellular Ethernet System that consists of MAC layer bridges for WiBro Networks and analyze the performance of Cellular Ethernet System handover scheme and show that it has better performance than Mobile IPv6.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.299-306
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• 2010

IPTV and VoIP services are considered as killer applications over Mobile WiMAX network, which provideshigh mobility and data rate. Among those which affect the quality of voice in those services, the jitter buffer or playout buffer can compensate the poor voice quality caused by the packet drop due to frequent route change or differences among routes between service endpoints. In this paper, we analyze the correlation between the sleep interval length and jitter buffer size in order to guarantee a predefined level of voice quality. For this purpose, we present an end-to-end delay model considering additional delay incurred by the WiMAX PSC-II sleep mode and a VoIP service quality requirement based on the delay constraints. Through extensive simulation experiments, we also show that the increase of jitter buffer size may degrade the voice quality since it can introduce additional packet drop in the jitter buffer under WiMAX power saving mode.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.25-32
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• 2010

The Supervisory Control and Data Acquisition Systems (SCADA) system provides monitoring, data gathering, analysis, and control of the equipment used to manage most infrastructure. The SCADA Network is implemented in a various manner for larger utilities, and multiple types of protocol and communication interfaces are used to network the control center to remote sites. The existing SCADA equipment and protocols were designed and implemented with availability and efficiency, and as a result security was not a consideration. So, performance, reliability, flexibility and safety of SCADA systems are robust, while the security of these systems is often weak. This makes some SCADA networks potentially vulnerable to disruption of service, process redirection, or manipulation of operational data that could result in public safety concerns and/or serious disruptions to the infrastructure. To reduce the risks, therefore, there is a need to have a security device such as cipher devices or cryptographic modules for security solutions. In this paper we develop an embedded cipher device for the SCADA equipment. This paper presents a cipher device designed to improve the security of its networks, especially in the serial communication.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1337-1345
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• 2009

In the railway, the delay of a train may affect the schedule of other trains. Hence, the timetable management activity involving overtaking and transferring becomes an important issue. The timetable rescheduling is the conflict resolution of the disrupted schedule and a matter of deciding the sequence of moves among trains and the place for meeting. In Korea, there are few cases where operations research models were applied to railway timetable rescheduling problem in consideration of the transfer between Korea Train eXpress (KTX) trains and conventional trains. Hence, we present a mathematical approach that can minimize the total delay of the whole trains secondly. We applied the model to the exemplary section of a double-line track, the Gyung-Boo Line, and it is confirmed that the mathematical model could effectively address the transfer service as well as the complicated railway conflicts of Gyung-Boo Line.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.9
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• pp.341-348
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• 2014

The advance in web accessibility with dissemination of smart phones gives rise to rapid increment of users on social network platforms. Many research projects are in progress to detect events using Twitter because it has a powerful influence on the dissemination of information with its open networks, and it is the representative service which generates more than 500 million Tweets a day in average; however, existing studies to detect events has been used TFIDF algorithm without any consideration of the various conditions of tweets. In addition, some of them detected predefined events. In this paper, we propose the RTFIDF VT algorithm which is a modified algorithm of TFIDF by reflecting features of Twitter. We also verified the optimal section of TF and DF for detecting events through the experiment. Finally, we suggest a system that extracts result-sets of places and related keywords at the given specific time using the RTFIDF VT algorithm and validated section of TF and DF.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.1-9
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• 2007

The development of efficient Qualify of Service (QoS) routing algorithms in high speed networks is extremely difficult to achieve, because in order to operate, divergent services require various quality conditions. If the parameter of concern is to measure the delay on a specific link, the routing algorithm obtains the Least Delay (LD) path. Meanwhile, if the parameter is to measure the link cost, the Least Cost (LC) path is calculated. The Delay Constrained Least Cost (DCLC) path problem of the mixed issues on the LD and LC has been shown to be NP-hard. The path cost of LD path is relatively more expensive than that of the LC path, and the path delay of the LC path is relatively higher than that of the LD path in the DCLC problem. In this paper, we introduce the new factor for balancing cost and delay. The simulation result shows that our introduced factor is satisfied to solve the DCLC problem.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.113-116
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• 2005

In general, multiple mobile hosts (MH) access at a base station (BS) that terminates the wired link and relays data flow to the wireless link in wired and wireless heterogeneous network. In this network, the BS is tend to be a bottleneck and to degrade a network performance. Many studies have been done throughout several protocol layers. Especially on the transport layer, many techniques were studied to enhance TCP performance. But most of them are concerned to enhance TCP throughput and TCP fairness is hardly considered. In this paper, an algorithm for enhancing TCP fairness is proposed and its performance is verified by ns-2 simulation.