• Information and Communications Magazine
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• v.28 no.7
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• pp.52-58
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• 2011

최근 GPS와 Wi-Fi가 내장된 스마트폰의 보급으로 이를 활용한 위치기반서비스 (Location-based Service)가 각광을 받고 있다. 이를 통해 GPS를 이용한 실외 위치추정 및 항법서비스뿐만 아니라 실내에서도 Wi-Fi 신호를 이용하여 사용자의 위치를 추정하고 다양한 서비스를 제공받을 수 있게 되었다. 본 논문에서는 Wi-Fi를 이용한 실내 위치추정 기술의 기본원리에 대해 살펴보고, 이를 활용한 기술의 동향을 소개하고자 한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.15-21
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• 2015

Due to the appearance of various mobile terminals like smartphone, smartpad, and smartwatch and tremendous development of WiFi technology, data utilization rate on WiFi network is significantly increasing. As a result, users are wanting to use WiFi network using only a simple identification at a visited place as if they are at their home institute. In this paper, we review the domestic status of eduroam service which supports global extension of wireless network access environment and present the future development perspective of the service in Korea. Besides, we shed light on the current status of WiFi sharing service between domestic universities and propose some methods to facilitate the join of domestic universities in eduroam service.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.7
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• pp.935-941
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• 2020

People estimation is important to provide IoT services. Most people counting technologies use camera or sensor data. However, the conventional technologies have the disadvantages of invasion of privacy and the need to install extra infrastructure. This paper proposes a method for estimating the number of people using a Wi-Fi AP. We use channel state information of Wi-Fi and analyze that using deep learning technology. It can be achieved by pre-installed Wi-Fi infrastructure that reduce cost for people estimation and privacy infringement. The proposed algorithm uses a k-binding data for pre-processing process and a 1D-CNN learning model. Two APs were installed to analyze the estimation results of six people. The result of the accurate number estimation was 64.8%, but the result of classifying the number of people into classes showed a high result of 84.5%. This algorithm is expected to be applicable to estimate the density of people in a small space.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.7-10
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• 2012

In this thesis, Wi-Fi Direct which can communicate with other device without AP, we study how to be selected GO considering multi-user connection and we apply it to application. We give the weight how many time a device was GO and how many time the device connected with other devices in 24 hours. With this value, the device is selected to GO when other devices request the connection. We show that the application which we implemented select right GO.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.27-32
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• 2012

In this paper, the wastewater treatment plant sludge proposed TN/TP sensor data collected an efficient monitoring system in order to implement status monitoring to build WiFi networks. Also we sludge concentration and TN/TP sensor data were collected from wastewater treatment plant. It is able to be monitored sensor data through smart devices(Smart phones, smart pad, tablet PC, etc.) and pc. In addition, when certain events occur immediately be able to cope by adding features to enable efficient and rapid processing, real-time status can be checked by ensuring improved user access and convenience. We has built a WiFi network for to transfer data efficiently. It proved its effectiveness by analysis of sensor communication network. Therefore, we have verified the usefulness of the proposed technology.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.243-248
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• 2012

In this paper we simulate the capacity of VOIP calls through WiFi network by computer simulations using OPNET modeler. The results show that sudden quality degradations occur on all VoIP calls when the number of call of an AP(Access Point) increases beyond a specific value. The reason of the quality degradation was turned out to be the queueing delay at the down link of AP. Under the IEEE 802.11b environments, the maximum number of VoIP calls of an AP maintaining the required voice quality (MOS > 2.5), was evaluated as 5, 12, and 27 when we use G.711, G.729a, and G.729a VAD codec, respectively.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.104-109
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• 2012

Currently, GPS(Global Positioning System) is used to find user location information. However, in some cases, especially in urban environments, we receive unreliable location information deu to multipath fading. In order to resolve this problem, we propose a closely coupled positioning technique where GPS signal is combined with QZSS signal. Also we proposed and analyze a combining algorithm of GNSS and Wi-Fi signals to get closely coupled location information by referring AP information. Finally, this paper proposes a combined GPS/QZSS/Wi-Fi navigation algorithm to improve navigation performance, and it is verified by testing of car deriving according to availability and accuracy standard.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1338-1343
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• 2018

MIMO(Multiple Input Multiple Output) slot antenna that operates on the dual WiFi band(2.401~2.495GHz, 5.18~5.825GHz), in this paper, was studied. The basic theory for the slot design is based on the coupling between adjacent slot, and slots are fed by the each microstrip lines. Two slot antennas for the MIMO operation are located on the left and the right side of top of the metal notebook, and grounds between a notebook and two microstrip feeding lines are connected. Measurement of return loss showed under -6dB on entire design band, and isolation was below than -30dB. Radiation efficiency, average gain and peak gain for the left and the right slot were measured in the anechoic chamber, and showed good performances as 57.25%, -2.42dBi, 5.64dBi and 55.35%, -2.61dBi, 6.42dBi for the 2.4GHz band and 55.89%, -2.58dBi, 7.3dBi and 53.79%, -2.8dBi, 7.54dBi for the 5GHz band.

• Design & Manufacturing
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• v.15 no.4
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• pp.14-23
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• 2021

In this study, we have analyzed the access status and the data usage trend of the public Wi-Fi on the bus, which has not been carried out in the previous studies. The analysis period of this study is 5 months from Nov. 2020 to Mar. 2021. When we compared the access status of Seoul metropolitan and the non-metropolitan region against each region's deployment status ratio, the access ratio of the metropolitan region was higher than the non-metropolitan region, of which the gap was 4.53%. The access for each region showed the growing trend, which was 43.5% on average. The data usage also showed the growing trend, 2.7% on average. Weekly data usage showed the growing trend irrespective of weekdays or weekends. The data usage of the weekdays was 695GB higher than weekends. The data usage during commuting hours including school (7:00~9:00 a.m. and 4:00~6:00 p.m.) was higher than 3,000GB. We can conclude that bus public Wi-Fi was used more actively in non-metropolitan region than Seoul metropolitan region by the office workers and students. The secure access also showed the growing trend. And the secure data usage also showed the growing trend.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.737-743
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• 2011

In this paper, we designed and implemented a Monopole+IFA(Inverted F Antenna) hybrid antenna using the coupled feeding structure for the all band mobile phone. Studied antenna has wide band characteristics by the simultaneous operation both monopole and IFA under the coupled feeding structure. An antenna has designed PCB embedded type without antenna carrier component for the low in cost. Implemented antenna has within 2.5:1 for VSWR under LTE/CDMA/GSM900/DCS/USPCS/WCDMA/WiBro/WiFi in all band for the mobile services Measured average gains and efficiencies were -3.98~-0.09 dBi and 40.03~97.99 % for the LTE, CDMA, GSM900 band, and -3.90~-1.01 dBi and 40.70~79.31 % for the DCS, USPCS, WCDMA, WiBro, WiFi band. It's shown that studied antenna can be applied to all band mobile phone antenna including LTE.