• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.14-20
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• 2012

CoMP(Coordinated Multi-Point transmission and reception) refers to a cooperative transmission strategy to control the interference from adjacent base stations in cellular mobile communication systems, which efficiently enhances the data throughput of the systems. As the number of the base stations participating in cooperative transmission increases, however, a larger amount of information exchange to carry the CSI(Channel State Information) of the mobile terminals is required. In this paper, we propose a partial CoMP transmission method for systems under the constraint of finite feedback information data. This method selects candidates of base stations which can provide high efficiency gain when they participate in the CoMP set. To achieve this, the cooperative base station combination is constructed by considering the preferred base stations of users. The cooperative base station combinations are dynamically applied since the preferred base station combinations of users may be different. We perform computer simulations to compare performance of the non-CoMP, full-CoMP and partial CoMP in terms of the average throughput using finite feedback and demonstrate the performance improvement of the proposed method.

• Journal of Korea Multimedia Society
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• v.14 no.3
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• pp.423-432
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• 2011

In a warehouse, because there exist frequent changes of stock status and the quality of some contents are influenced by the environment such as temperature, fast and accurate management of the warehouse's environment is very important for Warehouse Management Systems (WMS). However, due to the absence of a unified standard for the communication protocol between RFID nodes, the connection between RFID nodes can be broken in case of movement of a RFID reader to a region with a different protocol. Moreover, centralized MAC schemes for RFID communications in previous studies have severe problems. For an example, if a cluster header disappears from the cluster due to the cluster header's movement or bad channel conditions, the RFID member nodes of the cluster waste lots of time and energy to re-elect a new cluster header. Therefore, in this paper, we propose a WiMedia Distributed MAC (D-MAC) scheme for RFID communications and its cooperative relay transmission scheme for WMS applications Simulation results show performance improvement at the RFID node by using the proposed cooperative relay transmission scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.28-35
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• 2011

Cooperative ARQ scheme is effective for better QoS guarantee for the next generation mobile communication systems where multimedia data transmission highly increases. In this paper, we propose a cooperative ARQ strategy in ad hoc cognitive relays for mobile multimedia communication for supporting instantaneous cooperation in MANET environment. In the proposed strategy, to support real time, delay-sensitive services, whenever a frame is transmitted from the source, each relay actively senses the SINR of the signal transmitted from the source, and determine whether to propose retransmission or not before the destination transmits feedback signal. To minimize the false retransmission decision or needless retransmission, we propose an adaptive sensing threshold optimization algorithm to maintain suboptimal sensing thresholds for each relay. By computer simulation, it is shown that the proposed cooperative ARQ retransmission scheme outperforms the conventional schemes with respect to frame transmission delay and frame loss probability in real time multimedia data transmission system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.66-72
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• 2011

In Japan, the specification for digital terrestrial television broadcasting systems has been approved for employing a transmission scheme for ISDB-T, which can accommodate HDTV service and portable mobile reception by adapting segmentation of frequency. In this paper, we have developed 3.5 inch mobile TV according to One-Seg system and presented the results of our development. In addition, we introduce two diversity schemes to compensate the defect that signal is interrupted when the portable TV is moving fast. In order to achieve a reliable communication in One-Seg system, we introduce STD(space time diversity) which uses more than 2 antennas at TX and cooperative reception diversity which utilizes signal-exchanging between different mobile terminals. And, its performance enhancements to reception reliability of previous system are evaluated by computer simulations.

• Journal of Science and Technology Studies
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• v.8 no.2
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• pp.83-108
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• 2008

A analytical framework is suggested to explain how different standardization each country makes with incorporation of institutional elements such as the state's intervention and inter-firm relations which are considered to have a significant effect on it. Application to mobile telecommunication industry of the framework shows that different innovation system has its own technological standardization. In isolated inter-firm relation system, standardization is achieved through market but in cooperative one, through coordinating activities between participant firms. The state, however, intervenes more deeply in standardization and inter-firm relations are shorter in state-led and isolated firm relation system than in state-led and cooperative firm relation system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1013-1020
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• 2011

This paper deals with the tracking problem of a moving target using multiple unmanned aerial vehicles. A decentralized extended information filter is designed to cooperatively estimate the position and the velocity of the moving target. The extended information filter is adopted to consider the range and the line-of-sight angle as measurement data. The decentralized scheme is applied to enhance the estimation performance using the information provided by other vehicles. Numerical simulation is performed to verify the tracking performance of the proposed decentralized filters.

• Convergence Security Journal
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• v.13 no.4
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• pp.41-46
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• 2013

Routing protocol using in the existing wire network cannot be used as it is for efficient data transmission in MANET. Because it consists of only mobile nodes, network topology is changing dynamically. Therefore, each mobile node must perform router functions. Variety of routing attack like DoS in MANET is present owing to these characteristic. In this paper, we proposed cooperative-based detection method to improve detection performance of flooding attack which paralyzes network by consuming resource. Accurate attack detection is done as per calculated adaptively threshold value considered the amount of all network traffic and the number of nodes. All the mobile nodes used a table called NHT to perform collaborative detection and apply cluster structure to the center surveillance of traffic.

• Information and Communications Magazine
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• v.30 no.12
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• pp.3-11
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• 2013

2020년대에는, 7조개의 스마트 디바이스의 급증, 70억의 인구, 새로운 고품질 매체에 대한 요구가 급증하면서, 새로운 이동통신 환경 및 비즈니스 모델의 변화에 대한 선제대응이 필요하고, 현재 셀률라의 1000배의 용량, 사용자당 Gbps 서비스, 그리고 사용자당 1000분의 1의 에너지효율을 높이면서도, 사용자와 인터액션과 감성을 만족시키는 서비스에 대한 선도적인 연구개발이 필요하다. 이를 통해서, 현재 이동 통신 사업자들의 투자 대비 수익 감소에 따른 불합리한 투자 및 수익 구조를 개선할 수 있을 것으로 예상한다. 이러한 기술을 바탕으로 5G 이동통신 네트워크는 Early Adpater 시장뿐 아니라, 보편적 모바일 핵심 인프라기반으로 미래의 사회 문제를 해결하고 지식의 양극화를 적은 비용으로 해소할 수 있어야 하며, 또한 창조지식 국가 실현을 위한 성장엔진으로, 새로운 혁신 산업 및 지식산업의 생태계를 창조함으로서, 산업 육성 패러다임의 역할을 할 수 있어야 한다. 본 고에서는 이동통신 환경 및 서비스 변화를 예측하면서, 5G 이동통신에서 실현해야 할 이동통신 기술의 비젼과 그 추진 전략에 대해서 살펴보고자 한다. 그 구체적인 추진 전략으로서 국가 정책 및 연구 개발 활성화 방안을 수립하고, 그 실행을 위한 민관 연합의 협력 기구인 5G 포럼의 구성과 역할에 대해서 살펴본다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.439-441
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• 2001

에이전트는 보다 폭넓고 정확한 정보를 다른 도메인과 플랫폼의 다중 에이전트 시스템과의 협력을 통해 사용자에게 제공해야 하고, 다른 시스템의 유휴 컴퓨팅 용량을 활용하는 진정한 의미의 분산환경을 제공해야 할 필요성이 대두되었다. 이러한 문제를 해결하기 여러 논문에서는 이동 에이전트를 제안하고 있다. 하지만 이동 에이전트를 보다 효율적으로 개발하기 위해서는 이에 대한 아키텍쳐가 여러 가지 도메인에서 사용될 수 있도록 제시되어야 한다. 따라서 본 논문에서는 이동 에이전트의 아키텍쳐를 재사용이 가능하도록 설계하기 위한 방안을 연구하고, 이동 에이전트를 다중 에이전트 시스템에 적응할 수 있는 방안에 대한 연구 결과로 에이전트의 이동성을 지원하는 다중 에이전트 시스템 아키텍쳐를 제안한다.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.75-77
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• 2012

In recent years, with the development of various transportation, railway evolved a lot. With advanced rail system, efficient communication system was required. for the delivery of accurate information of railway communications systems. Accordingly, railway communication system has evolved in a variety of ways. Cooperative communication method was proposed railway minimize the effects of fading in wireless communications and more efficient communication. In this paper, we present cooperative transmission techniques and channel characteristics and examples, and simulation results.