• 전자공학회논문지
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• 제53권5호
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• pp.77-86
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• 2016

본 논문에서는 full / half-rate의 이중 모드로 동작하는 기준 클록을 사용하지 않는 클록 데이터 복원 회로와 그 동작 알고리즘에 관하여 기술한다. 클록 데이터 복원 회로는 주파수 검출기, 위상 검출기, 차지 펌프 및 루프 필터, 그리고 전압 제어 발진기와 알고리즘 구현을 위한 디지털 블록으로 구성되어 있다. 주파수 검출기와 위상 검출기는 클록 데이터 복원 회로의 이중 모드 기능을 위하여 full / half-rate에서 동작하며 주파수 검출기는 이에 더해 일반 주파수 검출기의 불감대 영역에서도 데이터 전송률과 클록 주파수 차이를 판별할 수 있다. 제안한 이중 모드 클록 데이터 복원 회로를 시뮬레이션을 통해 검증한 결과 클록 데이터 복원에 전체 1.2-1.3 us의 동기화 시간이 소요되었으며, 0.5-UI 지터를 인가하였을 때 full-rate (2.7 Gb/s)와 half-rate (5.4 Gb/s) 모드에서 모두 안정적으로 클록 데이터를 복원한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2213-2231
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• 2013

Compressed sensing is a novel technology used in the field of wireless communication and sensor networks for channel estimation, signal detection, data gathering, network monitoring, and other applications. It plays a significant role in highly secure, real-time, well organized, and cost-effective data communication in smart-grid (SG) systems, which consist of multi-tier network standards that make it challenging to synchronize in power management communication. In this paper, we present a multi-layer communication model for SG systems and propose compressed-sensing based data transmission at every layer of the SG system to improve data transmission performance. Our approach is to utilize the compressed-sensing procedure at every layer in a controlled manner. Simulation results demonstrate that the proposed monitoring devices need less transmission power than conventional systems. Additionally, secure, reliable, and real-time data transmission is possible with the compressed-sensing technique.

• 한국멀티미디어학회논문지
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• 제17권4호
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• pp.433-440
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• 2014

Wireless communication offers the flexibility to the node movement at the spatial dimension more than the wire communication not only in IP architecture but also in Content-Centric Networking. Although it gives such advantage, the intra-domain movement of a node especially the data source node affects the communication to the access point node which in the end affects the acceptance ratio of the client node that requests the data packets from the data source node. In this paper, we use time-division access method to maintain the acceptance ratio of the client node as the effect of the intra-domain data source node movement in Content-Centric Networking. The simulation result shows that the acceptance ratio of the client node can be maintained using the time-division access method as long as the interval access time is less than the coherence time.

• 한국정보통신학회논문지
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• 제15권12호
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• pp.2549-2554
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• 2011

본 논문은 중소형 선박을 대상으로 SSB 모뎀과 HF 무전기를 활용하여 안정된 디지털 데이터통신 서비스를 제공하기 위한 통합 인터페이스와 응용 개발에 대해 기술한다. 첫 째, GPS 와 통신장비와의 통합 인터페이스를 위한 모듈 개발하였다. 둘 째, 항해해도를 단말에 구현하여 GPS를 통한 위치 추적 서비스와 이를 이용한 항해 계획기능을 개발하였다. 또한, 안정된 어업활동 지원을 위해 선박의 상태 정보, 어획보고, 경보 기능 등을 개발하였다. 성능 측정결과 개발된 응용들은 메시지 길이 1 Kbyte 이하일 때 1:N 통신에서 3% 미만의 전송오류와 1초 미만의 전송지연을 보였다.

• 제어로봇시스템학회논문지
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• 제13권11호
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• pp.1099-1105
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• 2007

In this paper, modified two-port time-domain passivity approach is proposed for stable bilateral control of teleoperators under time-varying communication delay. We separate input and output energy at each port of a bilateral controller, and propose a sufficient condition for satisfying the passivity of the bilateral controller including time-delay. Output energy at the master port should be less than the transmitted input energy from the slave port with time-delay, and output energy at the slave port should be less than the transmitted input energy from the master port with time-delay. For satisfying above two conditions, two passivity controllers are attached at each port of the bilateral controller. A packet reflector with wireless internet connection is used to introduce serious time-varying communication delay of teleoperators. Average amount of time-delay was about 190(msec) for round trip, and varying between 175(msec) and 275(msec). Moreover some data packet was lost during the communication due to UDP data communication. Even under the serious time-varying delay and packet loss communication condition, the proposed approach can achieve stable teleoperation in free motion and hard contact as well.

• 대한가정학회지
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• 제43권10호
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• pp.103-114
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• 2005

This study analyzed the effect of parent-child communication and peer relationship on children's internet addiction. The subjects were 642 elementary school students living in Daejeon city. Cronbach's $\alpha$, t-test, ANOVA, and Duncan's test were employed in analyzing the data by using SPSS 10.0. The findings of this study were as follows First, the boys were more addicted to internet use than the girls, as were the children of less educated parents. The children of parents with professional careers were less addicted to the internet. The children who perceived their school achievements as low were more addicted to the internet. Second, the children who spent more time daily, longer time at once and more frequently per weekly internet use were more addicted. Third, internet addiction was influenced tv parent-child communication and peer relationship. Boys who had more problem communications with their parents less open communication with their mother and a lower level of peer support were more addicted to the internet. The problem of communication with their mother and conflict in their peer relationship had more influence on the internet addiction of girls.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.557-560
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• 1998

In this paper, we presetn the WWW (world-wide-web) base dtelePACS, which uses the communication network as asymmetric satellite data communication system (ASDCS). Web-based telePACS is imple-mented with JAVA language. Through the internet, web-based TelePACS can make it possible for remote hospital or doctor to access PACS data and information easily and cheaply. The ASDCS uses receive-only satellite links for data delivery and PSTN (Public switched telephone Network) modem or N-ISDN (narrow band integrate services digital network) for communication. The satellite communication linking shows the very high-seed performance such as 10-30 times faster than the modem linking.To solve the speed limits of internet, JPEG and wavelet compression methods were adapted in WWW-based TelePACS and were evaluated by PSNR (peak signal-to-noise ratio) and by radiological experts that 10:1 or less JPEG and wavelet compression may be acceptable for diagnostic purposes. Consequently, we get the conslusion that our system is suitable for tele-radiology and telemedicine world widely.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.401-406
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• 2005

The GFSK Transceiver of 400MHz ISM band for data communication is designed and fabricated. To reduce the occupied bandwidth of transmitted signal, the GFSK modulation is selected. The measured results of fabricated transceiver show the data rate of 2400bps at 8.5kHz bandwidth, frequency deviation of less than $\pm$3kHz, sensitivity of -111dBm, SNR of 21.58dB. The fabricated transceiver is satisfied with the regulation of radio wave and has the good performance. This transceiver is well suited for data communication of 400MHz ISM band.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권1호
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• pp.264-284
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• 2021

As the next-generation network architecture, software-defined networking (SDN) has great potential. But how to forward data packets safely is a big challenge today. In SDN, packets are transferred according to flow rules which are made and delivered by the controller. Once flow rules are modified, the packets might be redirected or dropped. According to related research, we believe that the key to forward data flows safely is keeping the consistency of flow rules. However, existing solutions place little emphasis on the safety of flow rules. After summarizing the shortcomings of the existing solutions, we propose FRChain to ensure the security of SDN data forwarding. FRChain is a novel scheme that uses blockchain to secure flow rules in SDN and to detect compromised nodes in the network when the proportion of malicious nodes is less than one-third. The scheme places the flow strategies into blockchain in form of transactions. Once an unmatched flow rule is detected, the system will issue the problem by initiating a vote and possible attacks will be deduced based on the results. To simulate the scheme, we utilize BigchainDB, which has good performance in data processing, to handle transactions. The experimental results show that the scheme is feasible, and the additional overhead for network performance and system performance is less than similar solutions. Overall, FRChain can detect suspicious behaviors and deduce malicious nodes to keep the consistency of flow rules in SDN.

• 한국전자파학회논문지
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• 제17권2호
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• pp.198-206
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• 2006

데이터 통신용 400 MHz ISM 대역 송${\cdot}$수신기를 설계하였다. 전파 법규의 8.5 kHz 이하 점유 주파수 대역폭을 만족하기 위해 GFSK 변조 방식을 이용하였고, 8051 CPU에 통신 프로토콜을 이식하여 데이터를 송${\cdot}$수신하였다. 제작된 송${\cdot}$수신기는 ${\pm}3\;kHz$이하의 주파수 변조도와 20 dB의 SINAD에서 -107 dBm의 감도를 나타내었으며, 인접 채널 평균 전력을 -60 dBc 이하로 전파 법규를 만족하였다. 제작된 송수신기의 BER 특성은 입력 신호 전력이 -110 dBm에서 $1.8{\times}10^{-3}$, -106 dBm 이상일 경우 0으로 측정되었다.