• ETRI Journal
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• v.37 no.6
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• pp.1077-1086
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• 2015

This paper presents a general-purpose design scheme of a filter bank (FB)-based radio frequency (RF) transceiver that operates across the entire ultra-high frequency (UHF) TV band from 470 MHz to 698 MHz and complies with the TV white space (TVWS) regulatory requirements. To this end, an intermediate frequency (IF) band-pass filter (BPF) with a sharp skirt characteristic is considered as a solution for handling the incoming signals from a baseband modem. Specifically, an FB-based BPF structure with four ceramic resonator filters that effectively rejects unwanted signals is proposed to extract a desired signal in the TV band. Achievable data rates of a cognitive radio system (CRS) employing the proposed FB-based RF transceiver at the application layer are investigated in both wired and wireless environments. The service coverage of the CRS network is measured according to several modulation and coding schemes (MCSs) of the CRS. The results show that the coverage of a wireless network in a nearly open area can be extended by more than 9.3 km in the TVWS. Experimental results also confirm that the proposed FB-based RF transceiver is adequate for utilization in TVWS applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.386-390
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• 2011

Modem warfares have changed from PCW (platform Centric Warfare) to NCW (Network Centric Warfare). Therefore, it is more important to operate and manage the network. This paper proposed a node management scheme in military wireless networks. In military wireless networks, nodes can join and leave the networks easily. It causes a degradation of network capacity. This paper figured out a problem caused by node which is leaving the network. This paper proposed a RSSI based method of estimating and detecting the leaving nodes in the networks. Finally, an experimental result was demonstrated to show the efficiency of the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1434-1441
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• 2003

Recent technological advances in utilization and generalization of Internet have overcome some of the limitations of remote robot control range and real-time monitoring system. However, It needs Embedded system with control protocol or hardware which has avility to port the micro realtime operating system in robot control system communicate with remote controlled robot, because those system use the wireless LAM or Bluetooth as a network media. In this paper, we design and implement the wireless MODEM protocol and install it to the server system. Also, we implement a client system could control the remote robot through the server and we assure that this protocol and client/server system ate suitable for small size remote control system based on Internet.

• IEMEK Journal of Embedded Systems and Applications
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• v.3 no.2
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• pp.82-90
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• 2008

In this paper, we introduce a biped walking robot which can do static walking with 22 degree-of-freedoms. The developed biped walking robot is 480mm tall and 2500g, and is constructed by 22 RC servo motors. Before making an active algorithm, we generate the motions of robot with a motion simulator developed using C language. The two dimensional simulator is based on the inverse kinematics and D-H transform. The simulator implements various motions as we input the ankle's trajectory. Also the simulator is developed by applying the principle of inverted pendulum to acquisite the center of gravity. As we use this simulator, we can get the best appropriate angle of ankle or pelvic when the robot lifts up its one side leg during the walking. We implement the walking motions which is based on the data(angle) getting from both of simulators. The robot can be controlled by text shaped command through RF signal of wireless modem which is connected with laptop computer by serial cable.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.773-777
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• 2005

This article is about using information technology to apply with water loss inspection system in District Metering Area (DMA). Inspector can check Flow rate and Minimum Night Flow; NMF via Smart Phone or PDA include sending SMS Alert in case the Pressure, Flow rate and NMF is over the range of controlling. This will be used as equipment to implement water loss in international proactive and can keep on water loss reduction more efficiency. The system consists of Data Logger which collects data of Flow rate from DMA Master Meter. PC is Wap Server which dial via modem in order to get data through FTP Protocal that will convert text file to Microsoft Access Database. Wappage will use xhtml language to show database on Wapbrowser and can show the result on Smart Phone or PDA by graph and table for system analysis.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2350-2355
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• 2005

In this paper, we introduce biped walking robot which can static walking with 22 degree-of-freedoms. The developed biped walking robot is 480mm tall and 2500g, and 22 RC servo motors are used to actuate. Before made an active algorithm, we generated the motions of robot with the motion simulator which developed using by C language. The two dimension simulator is Based on the inverse kinematics and D-H transform. The simulator implements various motions as inputted the ankle's trajectory. Also we developed a simulator which is applied the principle of inverted pendulum to acquires the center of gravity. As we use this simulator, we can get the best appropriate angle of ankle and pelvis when the robot lifts up its one side leg during the working. We implement the walking motions which is based on the data(angle) getting from both of simulators. The robot can be controlled by text shaped command through RF signal of wireless modem which connected with laptop computer by serial cable.

• ETRI Journal
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• v.39 no.2
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• pp.255-263
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• 2017

This paper proposes a graph-theatrical approach to optimize spatial reuse by adopting a technique that quantizes the channel information into single bit sub-messages. First, we introduce an interference graph to model the network topology. Based on the interference graph, the computational requirements of the algorithm that computes the optimal spatial reuse factor of each user are reduced to quasilinear time complexity, ideal for practical implementation. We perform a resource allocation procedure that can maximize the efficiency of spatial reuse. The proposed spatial reuse scheme provides advantages in beamforming systems, where in the interference with neighbor nodes can be mitigated by using directional beams. Based on results of system level measurements performed to illustrate the physical interference from practical millimeter wave wireless links, we conclude that the potential of the proposed algorithm is both feasible and promising.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.339-342
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• 1999

무선 환경에서는 한정된 주파수 자원과 소비전력을 고려하여 시스템을 설계하여야 한다. 이와 같은 조건을 만족하는 모뎀기술이 Trellis Coded Modulation(TCM) 방식이다. TCM의 복호 알고리즘으로는 확률적인 최적의 경로추적 알고리즘인 Viterbi 복호 알고리즘을 적용한다. 본 논문에서는 오디오 데이타의 무선전송을 위한 무선모뎀시스템의 수신단에 필요한 Viterbi 디코더를 설계하였다. 설계된 Viterbi 디코더는 고음질의 2채널 무선 오디오 신호(705,6kbps) 처리를 목적으로 하였다. 수신된 데이터에 8-level soft decision을 적용하였다. ACS(Add Compare Select)부와 TB(Traceback) 메모리 블럭은 데이터의 고속처리를 위해 병렬로 설계하였고, traceback depth는 50으로 하였다, 시뮬레이션 결과 설계된 Viterbi 디코더는 1bit, 2bit 등 랜덤하게 발생하는 에러에 대해 정정 능력이 우수하였다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1951-1952
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• 2008

본 논문에서는 메탈핼라이드 램프(MHL)의 원격 조도제어 및 감시 시스템을 구성하기 위하여 2.4GHz Zigbee 무선모듈로 구성된 무선모뎀을 구현하였다. MHL은 주로 가로등이나 보안등의 용도로 쓰이며, 대부분 설치되어 있는 시스템은 Group 제어 기반의 단방향 제어방식이다. 이러한 방식들은 각 등에 대한 개별적인 제어 및 감시가 이루어지지 못한다는 단점이 있으며, 이를 극복하기 위해서는 양방향 통신을 할 수 있는 통신 시스템이 필요하다. MHL은 다른 방전등들과 비교하여 비교적 방전시간이 긴 특징이 있으며, 이러한 특징은 조도제어 시스템 구성 시 고려되어야 한다. 본 논문에서는 시스템 구성을 위하여 IEEE 802.15.4 기반의 ZigBee 모듈을 이용하고, 조도제어를 위하여 Half-Bridge 방식의 전자식 안정기를 설계하여, 이를 제어하기 위한 제어회로를 구성하였으며, 램프의 특성에 맞는 프로토콜을 제안하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.781-782
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• 2016

본 논문은 스마트그리드 중요 인프라인 AMI 시스템 성능 제고를 위해 다양한 환경에서의 원격검침이 가능한 솔루션 개발에 있어 통신환경 등을 고려하였을 때 다양한 통신기술에 맞춰 원격검침 서비스를 제공할 수 있는 복합 브릿지 모뎀의 개발 사례를 다루고자 한다. 유무선 복합 기술을 적용하기 위해 TVWS 대역 무선 통신, 저속 PLC를 복합적으로 적용하였다. 본 개발 모뎀은 현재 시작품 형태로 제작이 되어 있으며, 현재 진행 중인 연구가 완료되는 시점에는 제품수준의 복합 모뎀이 산출될 예정이다.