• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.136-137
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• 2003

데이터 통신의 지속적인 수요증가로 그동안 충분한 투자가 없었던 메트로망 영역과 가입자망 영역의 광부품 수요는 지속적으로 계속될 것이며, 메트로 기간망 영역의 변조속도도 622Mbit／s, 2.5Gbit／s에서 2.5Gbit／s와 10Gbit／s가 같이 사용되는 상황이 예상된다. 현재까지 10Gbit／s 광송신기에는 성능이 증명된 리튬나이오베이트(LN) 광변조기가 주로 사용되고 있었으나 최근의 메트로 광통신에서는 전송거리에 따라 소형이고 가격이 저렴한 EML 혹은 uncooled DFB 레이저의 사용이 증가하고 있다. (중략)

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.443-444
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• 2009

무선 센서 네트워크에서 통신하는 센서노드들은 여러 제약사항이 따른다. 이 중 가장 중요한 요소는 네트워크의 생존기간과 직접 관련된 센서노드의 전력이다. 따라서 센서노드의 전력을 효율적으로 사용할 수 있는 라우팅 기법에 관한 연구가 중요한 과제로 자리 잡았다. 자주 쓰이는 라우팅 기법인 DD(Directed Diffusion) 알고리즘은 질의기반 알고리즘으로서 최적경로 설정을 통한 효율적 데이터 전송이 가능하다는 장점이 있는 반면, 자주 쓰이는 경로의 전력 소비가 크다는 단점이 존재한다. 본 논문에서는 센서노드의 전력량 반영 및 gradient의 가중치 설정, 기존 경로 재사용을 통한 개선된 알고리즘을 제안한다. 또한 시뮬레이션을 통해 제안한 알고리즘의 성능을 검증하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1018-1020
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• 2007

한정된 배터리 전원을 사용하는 무선 센서네트워크에서 노드의 수명유지를 위해 전력 소모량은 매우 중요한 문제이다. 이러한 문제를 해결하기 위해 계층적 클러스터링 기법을 적용한 라우팅 기법들이 연구되고 있다. 열악한 환경에서 작동하는 센서 노드의 오류는 전송에서 발생하는 오류뿐만 아니라 센서 자체의 오류도 포함하지만 기존의 라우팅 기법에서는 이를 배제하고 있다. 본 논문에서는 데이터마이닝을 이용하여 센서의 오류를 탐지하고 센서의 오류를 포함한 센서 노드를 클러스터 헤드로 사용하여 에너지 집약적인 기능을 담당하는 라우팅 알고리즘을 제안한다. 센서 노드의 빠른 교체가 이루어 질 수 없는 상황이나, 해당 센서 노드에서 수집되는 데이터가 교체 비용보다 효용성의 측면에서 떨어질 경우에는 일정기간 네트워크의 전력 소모를 전담하도록 하여 전체 센서네트워크의 생존성을 높일 수 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.147-151
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• 2010

In this paper, we propose network-coding based two-way relay communication using adaptive modulation scheme for satisfying relay QoS(Quality of Service) according to channel environment between user and relay. Two-way relay communication is bidirectional cooperative communication that users exchange own signal with help of relay. Network-coding based two-way relay communication can achieve high throughput compared to conventional scheme through reducing time slots. we propose adaptive M-QAM modulation scheme in network-coding based two-way relay communication for satisfying QoS of relay. Simulation result shows that the proposed scheme satisfies goal QoS of system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.162-168
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• 2018

The UAV(Unmanned Aerial Vehicle) system, including the drone of a variety of fields, which has become an issue and utilized in various fields, has begun to develop in military fields and is actively developed in the commercial field. In various types of UAV systems, which have been developed recently, the communication system that is responsible for the connection between the ground control unit and the UAVs is called the data link. Especially, common data link used in military UAVs is required stability of communication to transmit surveillance and reconnaissance intelligence information and UAV's status. In this paper, the requirement for a modem was defined to secure the communication stability of the common data link used in surveillance UAVs. And, the design of the data link modem to satisfy applicable specifications was proposed. The proposed modem design was verified through the performance measurement of the implemented systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.97-105
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• 2010

This paper proposes an effective medium access mechanism which is based on IEEE 802.11 to transmit an urgent message, The main features of the proposed mechanism are as follows. First, when it comes to channel access to have high priority, it has a shorter interval between frames than that specified in standard document. Second, we use fixed window size instead of back-off window with an exponential increase. Performance evaluation of proposed mechanism is executed by simulation and compare with the node using the specified mechanism in standard document. Performance evaluation results show that according to increasing competition the nodes using proposed method have less accessing time than the conventional methods. Also, the proposed method can improve processing time because of the decreasing transmission delay.

• The Journal of the Korea Contents Association
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• v.9 no.8
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• pp.99-112
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• 2009

The research is to develop U-IT Technology Transfer Re-auction System Model for technology transfer enable transactions of buyer-oriented. The buyer sends condition technology parts and data informations to provider. The First step, The buyer sends condition technology parts and data informations to provider. The Second step, the buyer's technology and conditions in the First step will be transferred to the DB of a provider who can provide that technology. The Third step, a provider can bid after inputting the conditions. The Fourth step, the buyer decides the ranking of successful bids in condition-optimized auction process. The Fifth step, the buyer invites a provider to be a successful bidder. The last step, if there's no successful bid within the period, the sale considered failed. The buyer-oriented re-auction system is that the deal will become extinct automatically when its sale failed more than two times.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.345-349
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• 2004

In order to index exactly moving objects(vehicle, mobile phone, PDA, etc.) in the mobile database, continuous updates of their locations are inevitable as well as time-consuming. The studies of pure spatial indices have focused on the efficient retrievals. However, the acquisition and management of the terminal Location of moving objects are more important than the efficiency of the query processing in the moving object databases. Therefore, it will be need to adopt parallel processing system for the moving object databases which should maintain the object's current location as precise as possible. This paper proposes a architecture of spatial indexing mobile objects using multiple processors. More precisely, we newly propose a method of splitting buckets using the properties of moving objects in order to minimize the number of database updates. We also propose a acquisition method for gathering the location information of moving objects and passing the information of the bucket extents in order to reduce the amount of passed messages between processors.

• 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.149-158
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• 2006

We proposed a method for improving a performance of TCP downstream between a desktop PC as a fixed host and a PDA as a mobile host in a wired and wireless network based on IEEE 802.11x wireless LAN. With data transmission between these heterogeneous terminals a receiving time during downstream is slower than that during upstream by 20% at maximum. The reason is that their congestion window size will be oscillated due to a significantly lower packet processing rate at receiver compared to a packet sending rate at sender. Thus it will cause to increase the number of control packets to negotiate their window size. To mitigate these allergies, we proposed two distinct methods. First, by increasing a buffer size of a PDA at application layer an internal processing speed of a socket receive buffer of TCP becomes faster and then the window size is more stable. However, a file access time in a PDA is kept nearly constant as the buffer size increases. With the buffer size of 32,768bytes the receiving time is faster by 32% than with that of 512bytes. Second, a delay between packets to be transmitted at sender should be given. With an inter-packet delay of 5ms at sender a resulting receiving time is faster by 7% than without such a delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.787-790
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• 2015

Recently, M2M (Machine to Machine) communication is possible the development of MTC (Machine Type Communication) devices becomes active. MCT devices in the form of home appliances have a low power consumption, low cost, short-range wireless communication in wireless home network. For purpose, MTC devices based on IEEE 802.15.4/Zigbee are composed in the form of cluster-tree topology, which consists of one PAN (Personal Area Network), one or other router and end of nodes. It happens that transmission delay, packet drop, and lacking data resulted from collision originated by a competition for allocating channels among MTC devices that greatly increased. At last performance of entire network can be degradated. This paper proposes that the beacon frame-based grouping algorithm using multiple channels in a MTC devices in the presence of wireless home network interference. The proposed algorithm decreases the transmission delay, dropped packet and throughput is more increase, so the proposal algorithm is more efficient than the IEEE 802.15.4/ Zigbee standard.