• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.54-55
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• 2011

In recently, microstrip antenna has been used to be communication devices through compact size, lightweight, and multi-layered integration. Also miniaturized communication system is expected to be power consumption and cost savings. In this paper, Long-distance communication is possible for the purpose of micro-strip antenna design, and prototype antenna were made and analyzed by using network analyzer.

• Journal of Internet of Things and Convergence
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• v.3 no.1
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• pp.13-19
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• 2017

In this paper, we designed and implemented Thing Connected-Green, a self-installing agricultural automation system capable of remote monitoring and control based on Low Power Wide Area communication technology (LPWA). Farming requires water, sunlight, soil, fertilizer, temperature control, etc., and these elements can be remotely monitored and controlled using an automated system. Using this system, it is possible to construct an agricultural automation system which can be optimized according to the kind of plant and cultivation environment from vinyl house to flower garden. The information gathered from the sensor is stored in the server through the gateway, and the optimal cultivation environment can be set and operated using the smart phone based on the big data.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.283-288
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• 2019

LPWA (Low Power Wide Area) networks have been considered as one of the technologies which can be implemented in IoT (Internet of Things) applications by providing less power and longer communication range compared with existing wireless technologies. In this paper, we investigate LoRa which is one of representative technologies for LPWA networks. First, we present general properties and several technologies of LPWA networks. Then, the technical specification, properties, and pros/cons of LoRa are studied. Finally, we discuss analysis of LoRa's performance and its ehancement technologies by focusing on physical layer and MAC (Medium Access Control) layer.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1089-1096
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• 2019

Recently, small-scale IoT services using a small amount of information through low-performance computing have been spread. It requires low cost, low-power, and long-distance communication technologies with wide communication radius, relatively low power consumption. This paper proposes a MAC layer and routing protocol that supports multi-hop transmission in small-scale IoT environment distributed over a large area based on LoRa communication and delivering a small amount of sensing data. The terminal node is mobile and the communication type provides bidirectional transmission between the terminal node and the network application server. By applying the proposed protocol, a production line monitoring system for smart factory was implemented. It was confirmed that the basic monitoring functions are normally performed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.467-468
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• 2019

본 논문은 차량용 장거리 레이더를 위한 저 위상잡음 77GHz CMOS 전압제어발진기를 제안한다. 이러한 회로는 낮은 위상잡음을 가지도록 설계되어 있고, 1.5볼트 전원에서 동작한다. 제안한 회로는 TSMC $0.13{\mu}m$ 고주파 CMOS 공정으로 설계하였다. 제안한 회로는 최근 발표된 연구결과에 비해 저 위상잡음, 저 전력 및 적은 면적 특성을 보였다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.01a
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• pp.167-168
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• 2023

본 논문에서는 저전력 433MHz 주파수 RF 신호가 여러 종류의 벽을 투과할 시 신호에 일어나는 감쇠를 비교한다. 국내에서 기존의 와이파이, 블루투스 같은 고주파수 대역의 RF 신호에 관한 연구 및 실험은 많이 행해지었지만, 한국의 전파 관리법에 의해 성능이 제한된 비면허 주파수인 433MHz 대역의 RF 신호에 관한 연구는 매우 적게 이루어져 있다. 이러한 저주파수 대역 신호의 가장 큰 장점은 장거리 통신에 능하고 벽 투과특성이 뛰어나다는 것이다. 본 논문에서는 실험을 통해 433MHz 대역 RF 신호가 여러 종류의 장애물을 통과 시 신호 세기가 어떻게 변하는지 각각 비교하고 이를 통해 비가시 영역에서 저전력 주파수 통신의 사용 가능성을 확인한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.1
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• pp.100-106
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• 2020

In this paper smart shoes for dementia care using embedded boards and Low Power Wide Area technology and their application software are implemented. The communication board composed of Cortex-M3 board and LoRa module is embedded into groove made in outsole of smart shoes. Including the mold, the shoe outsole was manufactured by hand. By using application software and embedded board, caregiver can track the position of dementia patient using GPS and LoRa network. The location tracking and data transmission operations of smart shoes have been successfully verified in the outdoor environment. The smart shoes of this paper are applicable to a safety device to prevent the disappearance of demented patients through results of experiments and if bigdata is collected and analyzed by deep-learning, it may be helpful to analyze the predictive path of dementia patients or the pattern of dementia.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.268-273
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• 2015

Recently many countries are researching actively underwater sensor networks for securing ocean resources and changes of ocean environment in all over the world. Current the commercial modem are not suitable because it has characteristics of long distance, higher price, larger power consumption with the special object mainly. In this paper, a low power and compact underwater communication modem which is suitable for underwater sensor networks is implemented. It is comprised by using a simple analog circuit for non-coherent BFSK modulation method, ultra low power MCU and orthogonal codes with a less operation and a simple implementation. It was experimented an underwater communication using our modem in a water tank and open sea farms. It communicates fewer than $10^{-4}$ bit error rate.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.132-133
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• 2000

최근, 인터넷 등의 보급으로 인하여 급증하는 다양한 형태의 정보를 효과적으로 전송하기 위하여 파장분할다중화 광통신시스템 (wavelength division multiplexed optical communication system: WDM)이 활발히 개발 및 보급되어 왔다. 가변 광감쇠기는 각 파장별 광신호의 세기를 균일하게 하여 장거리 전송을 가능하게 하는 WDM시스템의 핵심 소자이다. 폴리머 소자는 제작이 간편하고 가격이 저렴할 뿐 만 아니라 다른 소자와의 집적이 용이하고, 열광학 계수가 실리카에 비하여 10배 정도 커서 구동전력을 크게 줄일 수 있는 등의 장점으로 인하여 폴리머 광감쇠기가 활발하게 연구되어 왔다$^{(1)}$ . 본 논문에서는 미세 가공된 멤브레인형$^{(2)}$ 도파로를 이용한 저전력 폴리머 가변 광가쇠기에 관한 것이다. (중략)

• KNOM Review
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• v.22 no.2
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• pp.29-38
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• 2019

The rapid growth of IoT (Internet of Things) owing to the advancement and spread of technologies such as wireless networks, communication modules, sensors, smart terminals, etc. enables the development of new services in diverse public and private sectors. In particular, research on IoT technology and its applications has increased in the field of science. To establish an IoT infrastructure in this field, KREONET launched the wireless IoT network, called ScienceLoRa, based on low power wide area network (LPWAN). ScienceLoRa aims to collect a variety of data from sensors and utilize and analyze the collected data for research in a variety of scientific fields. In this article, the authors present the concept, current status, applications and future plans of ScienceLoRa.