• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.207-211
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• 2019

Research and development are underway to connect the network to all things in the world and to manage the objects through the Internet. The Internet of Things is expected to play an important role in building ecosystem of next generation mobile communication service. The most significant communication technology is LPWAN. In this paper, we analyze the performance according to each data transmission rate to reduce and manage resource waste by using many LPWAN nodes more efficiently in accordance with the demands of the times. The LPWAN communication technology used in this paper was designed based on LoRaWAN, a long-distance low-power wireless platform developed by Semtech, and analyzed by implementing a virtual IoT base using Network Simulator-3.

• Journal of Sensor Science and Technology
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• v.31 no.1
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• pp.64-68
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• 2022

Herein, we propose a LoRaWAN-based small draft system that can measure the ocean current flow (speed, direction, and distance) in real time at the request of the Coast Guard to develop a device that can promptly find survivors at sea. This system has been implemented and verified in the early stages of rescue after maritime vessel accidents, which are frequent. GPS signals often transmit considerable errors, so correction algorithms using the improved triangulation method algorithm are required to accurately indicate the direction of currents in real time. This paper is structured in the following manner. The introduction section elucidates rescue activities in the case of a maritime accident. Chapter 2 explains the characteristics and main parameters of the GPS surveying technique and LoRaWAN communication, which are related studies. It explains and expands on the critical distance error correction algorithm for GPS signals and its improvement. Chapter 3 discusses the design and analysis of small draft buoys. Chapter 4 presents the testing and validation of the implemented system in both onshore and offshore environments. Finally, Section 5 concludes the study with the expected impact and effects in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.15-20
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• 2019

Due to evolving IoT technologies, the various application services using clothing, sport equipment, and wearable devices equipped with extream small communication devices have been actively developed. On the other hands, since these serveices requires long distance communications, Long Distance wireless communication technology LPWAN Research has been proceeded due to limitation of the commuication distance of Wi-Fi and Zigbee which were considered as representative technologies for IoT. Iin this paper, we introduces LoRa technology in detail, which is a non-band network technology among LPWAN technologies, and investigates the use cases of domestic as well as international countries.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.44-46
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• 2018

In this paper, we design a system that can control unmanned mobile objects through communication between unmanned mobile object and control server system using LoRa network which is a dedicated IoT network. It is more efficient when the unmanned mobile object performs the special work by installing the LoRa network applied to the unmanned mobile object control system from the small space house or office hospital to the factory. In this paper, we will discuss the design of a system that can improve the social utilization of unmanned mobile objects by making it possible to communicate the events that occur around other mobile objects from the simplification of the navigation path.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.07a
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• pp.103-104
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• 2019

최근 스마트시티 구축 사업에서 사물인터넷 기반 서비스 개발이 활발히 진행 중이다. 그 서비스들을 제공하기 위해 사용되어야 할 디바이스 수가 수백만 개까지 증가할 것으로 예상하고 있으며 수백만 개의 디바이스들을 수용하기 위해서는 Massive IoT 네트워크의 환경 구축을 필요로 하고 있다. 따라서 본 논문에서는 Massive IoT 네트워크 환경을 구축하기 위해 저전력 광역 네트워크(LPWAN) 기술 중 LoRa(Long Range) 네트워크가 적용이 가능한지를 LoRaSim을 이용하여 시뮬레이션한다. 시뮬레이션한 결과 중 충돌 횟수를 통해 충동률을 구하고 그래프를 이용하여 신뢰성을 나타내며, Massive IoT 네트워크에 적합성에 대해 분석한다.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.5
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• pp.231-238
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• 2017

A Class B device in LoRaWAN periodically receives a Beacon message from a gateway for synchronization, and it also periodically activates a ping slot to receive data from the server. In this paper, we save energy consumption by controlling the beacon-less operation which is immediately started on the packet loss. In addition, we propose a method that the server inactivates the ping slots of a device according to the amount of messages, which have to be received from the server, to save energy consumption resulting from activated but unused empty slots. The experiment with the 20% of packet loss rate showed that the reduced beacon-less operation and the inactivation of the ping slot decrease the energy consumption by 96.7% and 60% as compared to the existing method.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.816-818
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• 2016

LPWA 기술은 IoT 환경이 가지는 낮은 전송거리와 배터리 제약을 해결할 수 있는 통신규약이다. LPWA에서 주목 받는 LoRa 기술은 디바이스에서 전송방식을 선택할 수 있는 클래스 A, B, C를 제공한다. 이 논문은 클래스 B 옵션에서 동기는 맞으나 전송 중 Beacon메시지를 분실하였을 경우, 바로 실행되던 Beacon-less동작을 억제하도록 최대 실패 횟수를 설정한다. 기존방법보다 Beacon-less동작이 기존 방법에 비해 30배 이상 적게 동작하여 디바이스의 에너지 소모를 줄였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.359-366
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• 2018

Social infrastructure facilities that have been under construction since the country's high-growth period are undergoing rapid aging, and safety assessments of large structures such as bridge tunnels, which can be directly linked to large-scale casualties in the event of an accident, are necessary. Wireless smart sensor networks that improve SHM(Structural Health Monitoring) based on existing wire sensors are difficult to construct economical and efficient system due to short signal reach. The LPWAN, Low Power Wide Area Network, is becoming popular with the Internet of Things and it is possible to construct economical and efficient SHM by applying it to structural health monitoring. This study examines the applicability of LoRa LPWAN to structural health monitoring and proposes a channel usage pre-planning based LoRa network operation method that can efficiently utilize bandwidth while resolving conflicts between channels caused by using license - exempt communication band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.86-88
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• 2022

LoRa has been evaluated as a promising technology for Internet of things networks. Theoretically, the technology is robust for long-range communication by using chirp spreading spectrum, provides several orthogonal logical channels in a physical channel, exploits spatial reusability by introducing a star-of-stars topology. A part of recent studies indicates the quasi-orthogonality, or the imperfect orthogonality, between logical channels. The channel elements, however, are both spreading factor and bandwidth. Nevertheless, Most of the researches only treat the spreading factor. This study presents the quasi-orthogonality between all of the logical channels built by variations of the both factors. Furthermore, it shows the performance varied by the logical channel interference.

• Journal of Korea Multimedia Society
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• v.23 no.2
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• pp.255-261
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• 2020

As the accidents of cargo and passenger carrying ships occur, the stress faced by the vessel users is increasing. The risk factors for accident deterioration in remote marine area are stronger than those in road accidents, and therefore the need for safety control is greatly emphasized. To overcome such issue, a lot of effort has been made in terms of conducting research and development of the passengers and freights location tracking system. However, the inner bulkhead structures are made of aluminum/steel which is a difficult material to transfer location information through. This study aims to measure the receiving rate of LoRaWAN signal inside the aluminum/steel bulkhead structures with variation in reception strength and distance. The test was taken place at platforms with 6T and 8T enclosures to reflect the same conditions found in fishery patrol boats. The receiving rate of through-the-wall communication at 10M distance turned out to be 86% in case of using two 6T enclosures, and 73% in case of using one 8T enclosure. The result showed that the receiving rate was more affected by the thickness rather than the number of enclosures.