• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.1163-1166
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• 2007

핸드오버가 발생하는 이동망 환경에서 주요 이슈 중 하나는 핸드오버 후 MN(Mobile Node)의 트래픽이 전송될 새로운 경로 상에 자원 재예약을 위한 지연 시간을 최소화하는 것이다. 이를 위해, 데이터 전달 경로가 변경된 경로에서만 자원예약 시그널링이 이루어지도록 CRN(Crossover Node)을 발견하는 것이 중요하다. 이동망 환경에서 자원 재예약을 위한 CRN은 SID(Session ID)를 이용하여 발견될 수 있다. 그러나 HMIPv6 네트워크에서 MAP(Mobility Anchor Point)과 HA(Home Agent)간 군집(Aggregate) 자원 예약이 이루어진 경우에서는 SID를 이용하여 CRN을 발견할 수 없다. 왜냐하면, MN의 핸드오버 후, 종단간 SID는 동일할지라도 이전 MAP과 HA간 설립된 세션의 군집 SID가 새로운 MAP과 HA간 설립된 세션의 군집 SID와 다르기 때문이다. 이에, 본 논문에서는 HMIPv6 네트워크에서의 CRN 발견방안을 제안한다. 제안하는 방안에서는 시그널링 메시지에 이전 군집 세션 정보를 포함하여 전달함으로서 시그널링 메시지가 목적지까지 도달하기 전에 CRN이 발견될 수 있도록 하였다. 제안하는 방안은 군집 자원예약이 갖는 시그널링 및 플로우별 상태 정보 감소 효과를 그대로 유지하면서, MN의 핸드오버 후, 자원 재예약을 위한 지연 시간을 단축시킴으로서 통신 성능을 향상 시킬 수 있을 것으로 기대된다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.370-371
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• 2010

The Long Range Navigation (LORAN) had been mainly used world-wide until GPS (Global Positioning System) activation. In particular. it was essential junctionality for the ships to sail the oceans. However, according to the industry's developing, the current accuracy of Loran is insufficient for the utilization such as the harbour approach, the land navigation and the field of precise timing. Therefore it is necessary the study on the improvement of the positioning accuracy of Loran. The method of its improvement is to measure and compensate the propagation time delay, that is, additional secondary factor (ASF) between the transmitter and user's receiver. This study shows the technique for the absolute time delay measurement without a time of coincidence (TOC) table, and represents the ASF measurement result between Pohang transmitter station(9930M) and each measure points.

• The Korean Journal of Financial Management
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• v.17 no.1
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• pp.203-226
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• 2000

본 연구는 주가지수 선물시장이 도입된 1996년 5월 3일부터 1998년 12월 5일까지 1분 간격 KOSPI 200 선물가격과 현물가격의 거래자료를 이용하여 각 선물가격과 기초자산가격간의 관계와 상호작용을 검토하는데 있다. 특히 본 연구는 차익거래자나 초단기 투기자(scalper)들이 거래체결을 위해 촌각을 다투는 선물시장의 거래행태에서 볼 때, 경제적 의미를 부여할 수 있는 1분 간격 수익률 자료를 이용함으로써 시장참여자의 실제 거래에서 표출되는 정형화된 현상을 정확히 파악한다는 점에서 중요하다. 본 연구의 주요 결과를 제시하면 다음과 같다. 첫째, 주가지수 선물시장과 현물시장간에 체계적이고 긴 선도-지연 관계가 발견되었다. 주가지수 선물가격의 변화가 현물가격의 변화를 대략 26분 정도 선도하고 있으며, 대략 5분 정도 현물시장의 선도효과도 발견된다. 따라서 KOSPI 200 선물수익률과 현물수익률간의 선도-지연 관계는 한 시장에서 다른 시장으로의 일방적인 것이 아니라 시장간의 피드백(feedback)효과가 존재하며, 선물의 선도효과가 지배적인 것으로 보인다. 이러한 선도-지연 현상은 노이즈에 의한 비동시거래보다는 거래비용과 공매제약 차이 등 각 시장의 제도적 차이에 의해 발생하는 것으로 보여진다. 둘째, 약세시장 하에서 선물의 선도효과가 더욱 크게 나타났다. 이러한 현상은 약세시장 하에서 현물시장의 공매제약이 선물가격과 현물가격간의 괴리를 더욱 크게 하여 선물가격이 현물지수를 더욱 선도하게 하는 요인이 될 수도 있음을 나타내는 것이다. 셋째, 만기별 하위기간 중 97년 6월과 97년 12월을 제외한 기간은 선물과 현물가격간에 장기 안정적인 균형관계가 성립함을 발견하였다. 넷째, ARMA(p, q) 여과를 거친 선물과 현물수익률을 이용하여 97년 6월과 12월은 백터자기회귀(VAR)모형, 그 외의 기간은 오차수정(EC)모형으로 추정하였다. 표본전체기간동안 장기균형오차에 대한 조정은 선물과 현물시장에서 동시에 이루어지고 있으며, 시장간에 발생하는 불균형 상황은 아비트라지 거래로 조정되고 있음이 발견되었다. 각 만기별 모든 하위기간에 있어서는 시장간의 장기 불균형 상황이 현물시장을 통해서 조정되고 있으며, 시장이 성숙된 최근의 만기 98년 12월 하위기간에서는 선물의 15분 선도효과와 현물의 1분 선도효과가 발견되어 선물의 선도효과가 지배적임을 발견하였다.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.244-253
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• 2005

In this paper, a performance evaluation model of the switch router with the multiple-buffered crossbar switches is proposed and examined. Buffered switch technique is well known to solve the data collision problem of the crossbar switch. The proposed evaluation model is developed by investigating the transfer patterns of data packets in a switch with output-buffers. The performance of the multiple-buffered crossbar switch is analyzed. Steady state probability concept is used to simplify the analyzing processes. Two important parameters of the network performance, throughput and delay, are then evaluated. To validate the proposed analysis model, the simulation is carried out on a network that uses the multiple buffered crossbar switches. Less than $2\%$ differences between analysis and simulation results are observed. It is also shown that the network performance is significantly improved when the small number of buffer spaces is given. However, the throughput elevation is getting reduced and network delay becomes increasing as more buffer spaces are added in a switch.

• Journal of KIISE:Information Networking
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• v.29 no.6
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• pp.738-748
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• 2002

In this paper, a performance evaluation model of the Multistage Interconnection Network(MIN) with the multiple-buffered crossbar switches is Proposed and examined. Buffered switch technique is well known to solve the data collision problem of the MIN. The proposed evaluation model is developed by investigating the transfer patterns of data packets in a switch with output-buffers. The performance of the multiple-buffered${\alpha}{\times}{\alpha}$ crossbar switch is analyzed. Steady state probability concept is used to simplify the analyzing processes, Two important parameters of the network performance, throughput and delay, are then evaluated, To validate the proposed analysis model, the simulation is carried out on a Baseline network that uses the multiple buffered crossbar switches. Less than 2% differences between analysis and simulation results are observed. It is also shown that the network performance is significantly improved when the small number of buffer spaces is given. However, the throughput elevation is getting reduced and network delay becomes increasing as more buffer spaces are added in a switch.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.74-80
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• 2000

In this paper, we proposed the MAC protocol and analyzed the performance for CATV/LAN network which was based upon HFC(hybrid optic coaxial) increased abruptly as alternative method of high speed network. Upstream channel which analyzed very deeply for CATV/LAN network have the preferential access property depending upon that position and unidirectional property. To solve this fairness problem, we propose the CSMA-CD/U/P protocol that transm it as $P_i$ probability although data packets is immediately transmitted when it was occurred. As the analytic result and simulation, we obtained $P_i$ value and its average delay time. Also, we get its variance value and queue length distribution. The mean delay time and queue length increase as the load and number of stations increase in the CATV/LAN network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.113-116
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• 2001

In this paper, a new multicasting scheduling is proposed for WDM single-hop broadcast network. The main idea of traditional multicast scheduling algorithms is partitioning the multicast group into several subgroups to reduce the delay time after receiving previous message. Those partitioning algorithms are grouping method of receivers already tuned to transmitters wavelength. However, multicast scheduling shows better performance by considering the previous status of receivers. Thus, in this paper, a new subgrouping method is proposed to minimize delay through collecting the current status of receivers. This method is operated by using the tunable transceiver in WDM single hop broadcasting network and uses fixed control channel for collecting the status of receivers. In addition, we analyzed the performance of proposed method through the computer simulation and then compared with existing multicast scheduling algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.321-330
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• 2010

In this paper, the theoretical background and the specific implementation method of a compressive receiver for RFID signal detection as well as the design method of DDL(Dispersive Delay Line) and chirp LO are described. DDL, which is one of the main components of the compressive receiver, is designed to have $13{\mu}s$ dispersive delay time and 6 MHz bandwidth using the SAW technique based on $LiNbO_3$ material. The chirp LO is designed using DDS(Direct Digital Synthesizer). Also the compressive receiver is fabricated to be installed into the RFID reader. Test results show the maximum frequency error of 25 kHz for single signal input, the receiver sensitivity of -44 dBm, and the maximum frequency error is 75 kHz for 6 multi-tone input signals. These results indicate that the fabricated compressive receiver is working well even in dense RFID operating environments.

• Journal of KIISE
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• v.44 no.12
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• pp.1258-1268
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• 2017

Capturing real-time daily information on food prices is invaluable to help policymakers and development organizations address food security problems and improve public welfare. This study analyses the possible use of large-scale online data, available due to growing Internet connectivity in developing countries, to provide updates on food security landscape. We conduct a case study of Indonesia to develop a time-series prediction model that nowcasts daily food prices for four types of food commodities that are essential in the region: beef, chicken, onion and chilli. By using Twitter price quotes, we demonstrate the capability of social data to function as an affordable and efficient proxy for traditional offline price statistics.

• Informatization Policy
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• v.19 no.4
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• pp.27-45
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• 2012

Smart grid, which is a sort of convergence of numerous technologies, can be deployed only with cooperation and fair competition among various stakeholders. If the interest conflicts were not coordinated properly, related business and investment would become delayed and inactive. Therefore, this study analyzes the causes of interest conflicts and related issues in smart grid sector and suggests policy directions by issue. As the result of AHP analysis, the majority of respondents surveyed said that ambiguity of the role and authority is the key problem causing conflicts of interest in smart grid deployment process. Differences in values, communications problems, etc. are pointed as additional main reasons of the interest conflicts. To resolve interest conflicts in smart grids, the Korean government should enhance its leadership in the coordination of stakeholders' interests. Government should make efforts to coordinate the various interests in terms of the development of the smart grid market and win stakeholders' sympathy of their desirable roles in the smart grid market.