• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.91-98
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• 2022

Unmanned aircraft system traffic management (UTM) service for the safe operation of unmanned aerial vehicles (UAV) such as drones using commercial communication networks such as long-term evolution (LTE) and 5G in low-altitude areas of 150m or less is being studied in several countries. In this paper, whether it is possible to secure three-dimensional (3D) coverage for UTM service using the existing LTE cellular network for terrestrial usersis analyzed through simulations. The practicality in the real environment is confirmed by performing performance analysis in the actual topographical environment and the LTE base station layouts in Korea. According to the analysis results, as the altitude increases, the number of line-of-sight (LOS) interference base stations increases, resulting in a worse signal to interference plus noise ratio (SINR), but coverage is secured except for the limited areas within 150m. was confirmed to be possible. In addition, it is confirmed that a significant proportion of outage areas could be reduced by placing a small number of additional base stations for the outage area.

• Journal of Digital Contents Society
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• v.9 no.3
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• pp.483-490
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• 2008

In this paper, we propose an active location acquisition terminal needing to construct an infrastructure based on a LBS and analyze the performance in real field. The proposed terminal is compounded with a GPS module and a CDMA module, so it can get the location information independently using satellite GPS signal and the proposed terminal can decide a user location with the location information of a base station in satellite GPS shadowed area. This is the distinguishable location acquisition method from the conventional A-GPS, and it complements a disadvantage of the conventional GPS. From these results, we can confirm that the proposed active location acquisition terminal is suitable to the requirements for the LBS which are the independent location acquisition ability, the continuity in the location information acquisition and the maintenance in the location information security.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.904-907
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• 2003

To resolve the problems of underground space and shade area, repeaters which is used in CDMA system affect the performance and services of a base station or the other services. In this paper, we propose relevant procedures in using CDMA repeaters and the effect of CDMA base stations. We also want to know the operating conditions for the reduction of the effect of repeaters.

• Annual Conference of KIPS
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• 2015.04a
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• pp.199-202
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• 2015

본 논문은 재난 방재 시 실내의 지하시설, 음영지역의 재난 상황 정보에 대하여 원활한 서비스 제공에 대해 제안 하였다. 소셜 네트워크 서비스를 통해 사용자가 공유하는 자연재해 발생 정보를 자동적으로 감지하고, 수집된 정보를 분석하여 FOAF 기반으로 소셜 네트워크와의 관계 및 특성을 이끌어내어 연계가 용이하도록 온톨로지 추론을 설계하였다. 또한 사용자의 분석된 정보에 따라 기관 및 개인에게 정보를 신속하게 제공할 수 있는 시스템의 설계를 제시하여, 재난 방재 시 BLE 센서를 이용한 재난재해 정보를 재난환경 주변의 사람들에게 실시간으로 알려주는 시스템을 제시하였다.

• Journal of IKEEE
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• v.24 no.1
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• pp.90-96
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• 2020

As various communication services have emerged due to the development of mobile communication technology, there is a need for a wideband antenna supporting multiple communication services with one antenna. In this paper, we propose a planar slot wideband antenna that can support all the communication services of 3.1~4.99GHz, the low frequency band of 5G, in addition to the existing communication services such as WiFi, LTE 2300/2500, and WiMAX. Through the simulation, the optimized antenna design parameters were obtained, and the antenna was fabricated to implement an antenna with a frequency bandwidth of 1.96~6.01GHz (S11 <-10dB) and presented the radiation pattern and gain of the antenna. The proposed antenna is a multi-band antenna that can provide all the services of LTE, Wifi, WiMAX, and 5G low frequency bands. It can be used as a repeater antenna in radio shadow area such as buildings, dense areas, and ships.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.50-51
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• 2011

스마트 휴대 단말기의 보급으로 인해 다양한 휴대 단말용 서비스가 보급되고 있다. 대부분의 서비스는 휴대 단말기의 가장 큰 특징인 이동성을 이용하여 위치 정보와 결합된 서비스이다. 따라서 정확도 높은 측위 기술은 휴대 단말용 서비스에 매우 중요하다. 현재 실외에서는 GPS를 이용해 고정밀의 측위가 가능하지만 실내에서의 측위에는 GPS를 사용할 수 없기 때문에 또 다른 고정밀 측위 시스템이 필요하다. 현재 주로 연구 개발되고 있는 실내 측위 기술은 주로 네트워크 기반의 측위 기술로써 설치 장소 및 인프라 구축 비용 등의 문제를 가지고 있으며 일부 지역에는 신호가 잡히지 않는 음영 지역 또한 존재하므로 정확한 실내 측위를 할 수 없다. 따라서 본 논문에서는 현재 휴대 단말에 기본적으로 탑재되어 있는 가속도 센서를 이용해 실내 측위를 하고 측위 오차를 QR코드를 이용해 보정하는 방안을 연구한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.127-134
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• 2012

Four river project in the South Korea contributes to solve flood damages and water shortages. Also, it has purpose for creating water ecosystem and improving the level of people' cultural leisure and quality of life through inducing water quality improvement and river restoration. It is necessary to monitor a variety of observing data in river areas among dozens to hundreds of kilometer for safe river administration. The 20th construction area of the four river project is located on Hapcheon areas, where wireless mesh network was installed to manage the basin. In the process of network construction, the characteristic of surrounding areas is considered about embodying secure service by investing the least expense. Besides, transmission environment analysis is performed such as LOS tests and reception level analysis, and transmission speed measurement to create safe service. Reception level in all places is confirmed among -55 dBm ~ -70 dBm, and data transmission speed proves more than 20 Mbps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.532-541
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• 2009

The RFID technology has attracted much attention these days due to the far better efficiency than the bar-code and magnetic card system. As an important usage, the 433 MHz active RFID tag was already adopted to the container ports in the United States and Europe for container loading/unloading automation and equipment location. However, there is one problem to be solved for the complete automation. RFID readers support only the direct communication with tags within their RF communication range. Then there are a lot of containers and equipments such as crane, yard tractor, and forklift in ports; and because they are made of metal, they interfere the RF communication, resulting in the occurrence of the dead-zone. In the dead-zone, RFID tags cannot receive any signal from readers. There may be several solutions to resolve the dead-zone problem. Among them, this paper suggests the most economical solution where RFID tags in the dead-zone can communicate with readers via neighbor tags in the multi-hop manner The new RFID communication architecture should be carefully designed in order to maintain the compatibility with the previous standard. Our experiment shows that the proposed architecture works well even in the case where some tags are out of the RF range of reader.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.51-59
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• 2011

It is the background that the provision of the mobile WiMAX femtocell trial service of a leading mobile telecommunication service operator using small base stations for indoor mobile broadband services and coverage expansion through eliminations of shadow areas in this paper. The paper presents an analysis result of trial subscribers' usage satisfaction for the mobile WiMAX femtocell service and suggests a market approach strategy of a mobile WiMAX femtocell service based on the analysis result. The interesting influence factors are extracted from wide influence factors suggested by existing research literature related with mobile service usage satisfaction and confined to a system quality, a service quality, and an account structure with consideration for attributes of mobile WiMAX femtocell service under exploring its early stages of service market. And then we analyze impacts of the factors to the mobile WiMAX femtocell service usage satisfaction. As a result, a system quality and an account structure have a tendency to provide considerable impacts to subscribers' usage satisfaction for mobile WiMAX femtocell service which is immature in both its technology and market. Therefore a market approach with the preferential consideration of the two factors will be valid.

• Journal of Korean Society of Transportation
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• v.27 no.2
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• pp.73-82
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• 2009

Location-based concierge services (LBCS) are considered to be one of the main service functions provided in a city in ubiquitous technology spaces. A "Ubiquitous City" is defined as a city in which both public and private services can be delivered and received anywhere and anytime. One of the key elements that make location-based concierge services successful is the interoperability of location data. Currently, several existing technologies could provide LBCS including car navigation services and ubiquitous computing. However, lack of standardized structure for location data makes it impossible for heterogeneous technologies to be able to deliver uniform LBCS. The purpose of this paper is to develop standardized locational data structure so that heterogeneous technologies could provide efficient LBCS to all users of the various transportation modes.