• Electronics and Telecommunications Trends
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• v.36 no.6
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• pp.36-45
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• 2021

As the global demand for satellite IoT services using small satellites increases, interest in their frequency requirements has also increased. Consequently, International Telecommunication Union Radiocommunication Sector (ITU-R) preparatory studies for WRC-23 include AI 1.18, which considers new frequency allocations for narrowband mobile satellites. This agenda item was issued in accordance with Resolution 284 (WRC-19), and contributions and reviews by government and satellite operators are underway at ITU-R SG4 WP4C with the aim of completing the study in 2023. Resolution 248 (WRC-19) considers the conditions for transmission of candidate bands and satellites and terminals for narrowband mobile satellite, and all contributions should satisfy narrowband mobile satellite system characteristics parameters within these conditions. However, among the current transmission specifications, there are several views on the exact definition of satellite e.i.r.p., and the derivation schedule of characteristic system parameters for the study is slower than that of the original work schedule. The goal of this paper is to examine the outline of WRC-23 AI 1.18 and the main content of Resolution 284 (WRC-19) and to determine the status of studies related to WRC-23 AI 1.18. The ITU-R's study on this agenda includes updating work schedules, developing the draft required spectrum and system characteristics parameter reports/recommendations, developing draft CPM reports, and examining the various views of transmission specifications in Resolution 284 (WRC-19). Focusing on candidate bands in Region 1 (Europe and Africa) and Region 2 (America), the current status of use in Korea is investigated and future countermeasures in Korea are investigated. In addition, we would like to examine the trend of narrowband mobile satellite through satellite frequency and service status and planning of satellite IoT operators, such as EchoStar, Omnispace, and Sateliot that are participating in the ITU-R study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.5
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• pp.1339-1355
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• 2023

Localization is a hot research spot for many areas, especially in the mobile robot field. Due to the weak signal of the global positioning system (GPS), the alternative schemes in an indoor environment include wireless signal transmitting and receiving solutions, laser rangefinder to build a map followed by a re-localization stage and visual positioning methods, etc. Among all wireless signal positioning techniques, Wi-Fi is the most common one. Wi-Fi access points are installed in most indoor areas of human activities, and smart devices equipped with Wi-Fi modules can be seen everywhere. However, the localization of a mobile robot using a Wi-Fi scheme usually lacks orientation information. Besides, the distance error is large because of indoor signal interference. Another research direction that mainly refers to laser sensors is to actively detect the environment and achieve positioning. An occupancy grid map is built by using the simultaneous localization and mapping (SLAM) method when the mobile robot enters the indoor environment for the first time. When the robot enters the environment again, it can localize itself according to the known map. Nevertheless, this scheme only works effectively based on the prerequisite that those areas have salient geometrical features. If the areas have similar scanning structures, such as a long corridor or similar rooms, the traditional methods always fail. To address the weakness of the above two methods, this work proposes a coarse-to-fine paradigm and an improved localization algorithm that utilizes Wi-Fi to assist the robot localization in a geometrically similar environment. Firstly, a grid map is built by using laser SLAM. Secondly, a fingerprint database is built in the offline phase. Then, the RSSI values are achieved in the localization stage to get a coarse localization. Finally, an improved particle filter method based on the Wi-Fi signal values is proposed to realize a fine localization. Experimental results show that our approach is effective and robust for both global localization and the kidnapped robot problem. The localization success rate reaches 97.33%, while the traditional method always fails.

• Journal of Korea Society of Industrial Information Systems
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• v.26 no.3
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• pp.59-69
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• 2021

t Global logistics companies are developing and introducing logistics systems to provide competitive logistics services. Especially as IT develops and mobile functions become more convenient, the Mobile TMS(Transportation Management System) is being introduced as a more convenient system for delivery workers and office managers. However, the success of such a system depends on the system developer who understand the site accurately and office managers and couriers who are using it in the field. The purpose of this paper is to understand which characteristics influence in exploiting new systems focusing on the attitudes of users who use the system daily, and we analyze it through the TAM(Technology Acceptance Model). According to the analysis result, when smart phone has become popular, users have concluded that usefulness is more significant than ease in acceptance of the systems. As a result, we draw suggestions that the focus should be on usefulness rather than ease of system at the stage of system developed.

• Review of KIISC
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• v.3 no.4
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• pp.57-62
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• 1993

GSM (Global System for Mobile Communications)은 범유럽적으로 추진되고 있는 디지탈 이동통신시스템으로서 ETSI(European Telecommunication Standards Institute)에 의해 표준화가 추진되고 있다. GSM 시스템 규격에서는 도청 또는 불법 사용에 대비하여 암호기술을 이용한 가입자 I.D 인증 및 보호, 그리고 무선구간에서의 정보 보호를 위해 암호화 기능을 갖도록 권고하고 있다. 본고에서는 GSM 이동통신망에서의Security에 관련된 기능들과 암호 알고리즘 특성에 관하여 고찰하였다.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.2
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• pp.99-109
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• 2015

This study proposes a new approach to analyze the impedance and the elasticity of a serial chain of spring-damper system, areal-time collision-free trajectory generation algorithm is proposed. The reference points on a trajectory connected by the spring-damper system have a mechanism for self-position adjustment to solve a collision problem by the impedance, and the local adjustment of each reference point is propagated through the elasticity to a real robot at the end of the spring-damper system. As a result, the overall trajectory consisting of the reference points becomes free of collision with environmental obstacles and efficient having the shortest distance as possible. In this process,, the reference points connected by the spring-damper system take role of virtual robot as global guidance for a real robot, and a cooperative is carried out by the system of robots. A control technology is proposed to implement for mobile robot.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.130-132
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• 2004

최근 무선통신망의 발전에 따라 무선 인터넷 시장이 빠르게 성장하면서 이동성을 기반으로 하는 서비스에 대한 관심이 고조되고 있다. 그리고 휴대폰과 PDA(Personal Digital Assistants), MET(Mobile Data Terminal)와 같은 휴대용 단말기의 사용이 일반화된 가운데 GPS(Global Positioning System)를 기반으로 하는 서비스들도 점차적으로 보편화되어 가고 있다. 이러한 변화에 따라 이동성을 지원하는 무선 단말기를 기반으로 한 Mobile GIS 환경에서의 위치 정보 활용은 큰 관심을 불러일으키고 있으며, 또한 이러한 서비스를 효율적으로 제공하기 위해서 위치 기반 서비스(LBS: Location Based Service)의 기술개발이 필요하게 되었다. 이 논문에서는 전력설비 고장복구업무에 LBS를 적용하기 위해 차량에 장착하는 MDT에서 모바일 지도 서비스가 가능한 Compact형 GIS 엔진을 설계하고 구현한 결과를 제시한다.

• Electronics and Telecommunications Trends
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• v.27 no.6
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• pp.165-181
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• 2012

세계은행의 발표에 따르면 전 세계적으로 개인 간 해외송금 시장의 규모는 지속적으로 성장해 왔으며, 향후에도 지속적으로 성장할 것으로 전망된다. 이러한 글로벌 송금 시장의 확산과 맞물려 이동통신 네트워크의 글로벌화와 스마트폰의 확산 등 통신 기술 및 서비스 진화에 따라 모바일 네트워크를 통해 간편하고 신속하게 송금할 수 있는 모바일 송금 서비스 시장이 국내외에서 급속하게 팽창하고 있다. 이에 세계이동통신사업자협회(Global System for Mobile Communications Association: GSMA)의 MMT(Mobile Money Transfer) 프로그램, 케냐 및 일본의 모바일 송금 서비스 제공 사례를 중심으로 서비스 제공 시스템 및 그 이용에 따른 장 단점, 가치사슬, 서비스 유형 등을 간략하게 살펴보았다. 이를 바탕으로 모바일 송금 서비스 제공 과정에서 나타날 수 있는 규제 이슈들을 분석해 보았다. 그리고, 국내 이동통신 사업자가 MMT 서비스를 본격적으로 제공하는 경우에 고려해야 할 규제 요소들과 안전하고 효율적인 MMT 시장의 활성화를 위해 필요한 규제정책 방향을 검토해 보았다.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1057-1066
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• 2023

Global Navigation Satellite System (GNSS) is one of the core technologies for the 4th Industrial Revolution, and its importance is increasingly highlighted in the next generation communications and smart mobility requiring the accurate location information. As the development of the high-performance/high-precesion GNSS technology makes it possible to obtain the more accurate locations information, the location based products and systems, which provide the high-quality service, are being researched/developed. In this paper, we present the results of a survey on the recent research trends and examples, utilizing GNSS technology in fields of the next generation communications and smart mobility, and analyzes the results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.131-140
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• 2011

Proxy Mobile IPv6 (PMIPv6) is designed to provide a network-based localized mobility management protocol, but it does not handle the global mobility of hosts. In this paper, we propose a location management scheme based on Domain Name System (DNS) for PMIPv6. In this proposed scheme, DNS as a location manager provides PMIPv6 for global mobility. In addition, a paging extension scheme is introduced to PMIPv6 in order to support large numbers of mobile terminals and enhance network scalability. To evaluate the proposed location management scheme, we establish an analytical model, formulate the location update and the paging cost, and analyse the influence of the different factors on the total signalling cost. The performance results show how the total signal cost changes under various parameters.

• Journal of the Korean Society of Visualization
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• v.20 no.1
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• pp.45-51
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• 2022

Airborne particulate matter(PM) has been a global environmental problem. PM whose diameter is smaller than 10 ㎛ can permeate respiratory organs and has harmful effects on human health. Therefore, PM monitoring systems are necessary for management of PM and prevention of PM-induced negative effects. Conventional PM monitoring techniques are expensive and cumbersome to handle. In the present study, two types of PM monitoring devices were designed for measuring indoor PM concentration, portably. We experimentally investigated the performance of three commercial PM concentration measurement sensors in a closed test chamber. As a result, PM2008 sensor showed the best PM concentration measurement accuracy. Linear regression method was applied to convert PM concentration value acquired from PM2008 sensor into ground truth value. A mobile application(app.) was also created for users to check the PM concentration, easily. The mobile app. also provides safety alarm when the PM₁₀ concentration exceeds 81 ㎛/m³. The developed hand-held system enables the facile monitoring of surrounding air quality.