• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1084-1093
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• 2012

For large multihop networks, large time synchronization (TS) errors can accumulate with conventional methods, such as TPSN, RBS, and FTSP, since they need a large number of hops to cover the network. In this paper, a method combining Concurrent Cooperative Transmission (CCT) and Semi- Cooperative Spectrum Fusion (SCSF) is proposed to reduce the number of hops to cover the large network. In CCT, cooperating nodes transmit the same digitally encoded message in orthogonal channels simultaneously, so receivers can benefit from array and diversity gains. SCSF is an analog cooperative transmission method where different cooperators transmit correlated information simultaneously. The two methods are combined to create a new distributed method of network TS, called the Cooperative Analog and Digital (CANDI) TS protocol, which promises significantly lower network TS errors in multi-hop networks. CANDI and TPSN are compared in simulation for a line network.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.1011-1016
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• 2018

Ubiquitous services for the convenience and safety of human beings along with the development of society are being realized through RFID technology and sensor network, and its application range of fields is also broaden. However, since the USN contains all the information of individuals and things, all of its private spaces can be attacked by external attacks; so, that the problem of security continues to arise. We designed a one-way chaotic feedback synchronization method as a secure communication method to fit the USN composed of one sync node and n number of sensor nodes. We designed the method by which the sensor node is synchronized in one direction of the sync node. This method solves the problem that all sensor nodes need to be resynchronized when the sync node is changed, which is shown in bidirectional synchronization. This is a security method that can be effectively applied to 1:n communication such as USN.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.159-163
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• 2017

The artificial insemination (AI) is one of the best assisted reproductive technologies for increasing reproductive capacity and facilitating the genetic improvement in farm animals. AI has been used in Uganda for over 60 years, but a small population of the total herd has been used. This study was conducted to investigate the efficacy of AI with estrus synchronization technique and to propose ways of improving the productivity of dairy farms through AI services in Uganda. In total, 78 cows from 11 dairy farms were selected for timed-AI. Synchronization was performed according to the ovsynch programs followed by AI using frozen semen from Korean Holstein (0.5 ml straws). Pregnancy rate was varying among farms (0-50%) and the overall pregnancy rate was 28.2%. Cows in luteal phase at the time of treatment was 40.0% whereas that in follicular phase was 20.8%. After treatment, cows that showed normal estrus signal were 45.5% (25/55). Abnormal estrus was categorized into pre-estrus (9.1%), cystic ovaries (21.8%), anestrus (18.2%) and delayed ovulation (5.5%), respectively. These results imply that an assured protocol for timed-AI should be developed to improve the productivity of dairy farms through AI services in Uganda.

• Journal of Korea Multimedia Society
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• v.9 no.5
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• pp.615-623
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• 2006

It has been estimated that 'RFID' technology would be playing an important role in the incoming ubiquitous environment. For this reason, many studies on 'RFID' have been conducted and its application has been on the increase in various fields such as finance, medicine, transportation and culture as well as in logistics distribution. However, the communication between Tag and Reader in RFID system has been conducted by wireless communication of radio frequency so that the information on identification could be eavesdropped by the third party maliciously. Such eavesdropped information could be also used as basic information in attacking others; in this regard, it could impair the privacy of its users and the users have avoided using 'RFID.' To solve theses problems, many studies are being performed to different output of tags by renewing ID. However, protocols have been devised without considering an ID Synchronization in the ID renewal process between database and tag in the existing studies. In this regard, this study has suggested a RFID Authentication Protocol while considering the ID Synchronization.

• Journal of Internet Computing and Services
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• v.16 no.2
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• pp.1-6
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• 2015

In this paper, we designed an embedded audio video bridging (AVB) platform based on IEEE 802.1BA for real-time multimedia transmission in smart-car, smart-home, smart-theater, and then evaluated a performance of the implemented platform by analysis of IEEE 802.1AS (time synchronization protocol) and IEEE 802.1Qat (stream reservation protocol). Especially, the AVB Layer-2 protocol of MRP(Multiple Registration Protocol), MMAP(Multicast Address Acquisition Protocol), IEEE 1722, 1722.1 etc. was and implemented by linux based operating system. It is shown by interoperability tests with commercial products that the implemented platform transmits real-time multichannel AV data over AVB networks for Multichannel Multimedia Transmission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2088-2096
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• 2009

This paper deals with hybrid MAC protocol design for underwater acoustic networks. The proposed MAC protocol has the cluster structure with a master node and slave nodes, and the hybrid network structure that combines a contention free period based on TDMA(Time Division Multiple Access) with a contention period. The suggested MAC protocol has a beacon packet for supervising network, a guard period between time slots for packet collision, time tag for estimation of propagation delay with a master node, the time synchronization of nodes, entering and leaving of network, and the communication method among nodes. In this paper, we adapt the proposed hybrid MAC protocol to AUV network, that is the representative mobile device of underwater acoustic network, and verify this protocol is applicable in real underwater acoustic network environment.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.220-222
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• 2003

최근 무선 임베디드 시스템의 사용이 증가하면서 기존의 분산 환경에 무선 임베디드 시스템이 포함되기 시작하였고, 이를 고려한 분산 어플리케이션들이 개발되고 있다. Global clock과 동기화할 수 있는 GPS가 모든 무선 임베디드 시스템에 장착되지 않은 상황에서 분산된 임베디드 시스템간 혹은 고성능 컴퓨터와의 내부 동기화를 수행할 동기화 기법이 필요하다. 현재 무선환경에서의 동기화에 대한 연구들이 이루어지고 있지만 제한된 리소스의 임베디드 시스템에 그대로 적용하기 어렵다. 이에 본 논문에서는 무선 임베디드 시스템만이 가지는 제한사항을 고려하여 메시지 지연값의 변화량을 측정하여 적용할 수 있는 시간 동기화 기법을 제시하고 실험을 통해 그 성능을 평가한다.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.746-749
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• 2009

유비쿼터스 센서 네트워크에서 사용되는 센서노드는 동종의 센서 노드와 많은 수의 이기종 센서 노드들을 포함하게 된다. 이기종 센서노드들간의 시간동기화로 인한 배터리 전력소모를 최소화하기 위해서 본 논문에서는 싱크노드 아래에 있는 싱크노드와 클럭소스가 같은 동종 센서노드를 시간동기 마스터로 설정하고, 싱크노드와 다른 클럭소스를 가지는 다수의 이기종 센서노드를 마스터 아래에 속하는 시간동기 슬레이브로 설정하여 시간동기 마스터가 동작을 개시할 때에만 시간동기 슬레이브 노드들이 동작하도록 동기화하는 이기종 센서노드들의 시간동기화 기법을 제안한다.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.31-43
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• 2005

OTAR system is a highly authentic key management system that has functions with access control. data integrity and data confidentiality, In this paper, we analyze the existing TIA/EIA Over-The-Air-Rekeying key managements protocol. focused to symmetric ciphers. It can be used to understand the technical trend on technologies about TIA/EIA OTAR standardization. This results can be used to evaluate security properties of a remote rekeying, The proposed system contains a highly reliable system synchronization.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.277-279
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• 2008

현재 많은 전력계통용 보호제어 벤더들은 변전소 자동화 국제표준 프로토콜인 IEC 61850을 적용한 전력 장비들을 개발하여 변전소에 적용하고 있다. 이러한 많은 장비들은 표준화된 IEC 61850 프로토콜을 적용하여 상호 호환성을 유지하였으며, 기존에 적용되고 있는 표준화된 기술들을 채택하고 있다. 변전소 장비들은 정밀한 시간 동기를 위해서 표준화된 시각 동기 프로토콜인 SNTP(Simple Network Time Protocol)나 NTP(Network Time Protocol)를 사용하고 있다. 본 연구에서는 IEC 61850 프로토콜을 적용한 IED가 시각 동기 장치로부터 시간 동기화되는 방안에 대해 연구하였다.