• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.73-75
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• 2018

LoRaWan(Long Range Wide Area Network)은 저전력, 장거리 특성을 가진 무선 통신기술로 그 특성상 스마트 시티(Smart City), IoT(Internet of Things) 등에 각광받고 있다. 또한 LoRaWan은 Chirp 신호 특성에 의해 실외 삼각측량에 따른 사용자 위치 추정 기술을 제공한다. 본 논문에서는 이러한 LoRaWan의 특성에 더해 Wi-Fi 지문 정보를 활용하여 위치 추정 정확도를 개선하고 또한 이웃 Wi-Fi 단말들, 가령 스마트폰 등의 위치 정보를 LoraWan 게이트웨이와 통신하여 최종적으로 서버에서 측위 할 수 있는 시스템을 제안한다.

• Journal of IKEEE
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• v.26 no.2
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• pp.186-195
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• 2022

In this paper, we propose a new algorithm to improve the accuracy of indoor positioning techniques using Wi-Fi access points as beacon nodes. The proposed algorithm is based on the Weighted Centroid algorithm, a popular method widely used for indoor positioning, however, it improves some disadvantages of the Weighted Centroid method and also for other kinds of indoor positioning methods, by using the received signal strength correction method and genetic algorithm to prevent the signal strength fluctuation phenomenon, which is caused by the complex propagation environment. To validate the performance of the proposed algorithm, we conducted experiments in a complex indoor environment, and collect a list of Wi-Fi signal strength data from several access points around the standing user location. By utilizing this kind of algorithm, we can obtain a high accuracy positioning system, which can be used in any building environment with an available Wi-Fi access point setup as a beacon node.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.103-106
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• 2010

전자 출판 기술과 전자책 단말기의 발전으로 전자책 컨텐츠의 보급이 확산되면서 전자책은 정보 자료로써 그 중요성이 더해가고 있으며 전자책 단말기를 통하여 컨텐츠를 다운로드 받으려는 요구가 증가 되어 가고 있다. 전자책 컨텐츠 다운로드 서버를 개발하기 위해서는 전자책 단말기의 하드웨어 특성이 고려되어야 한다. 본 논문에서는 Wi-Fi 전자책 단말기의 하드웨어 특성을 고려하여 Wi-Fi 전자책 단말기를 통해 전자책 컨텐츠를 효과적으로 다운 받을 수 있는 다운로드 서버를 설계 및 구현 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.163-164
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• 2009

최근 감시카메라의 사용률이 증가하고 있다. 개인 사업체, 전문 감시업체, 일반 기업 및 공공기관 등 감시카메라는 폭넓게 사용된다. 하지만 현재 설치된 감시카메라는 녹화된 감시영상이나 카메라 컨트롤을 관리자가 언제 어디서나 확인하고 조절할 수 없다는 단점이 있다. 이러한 단점을 해결하기 위해 TCP/IP기반의 네트워크에서 PDA로 Wi-Fi를 이용하여 접속한 후 감시카메라를 제어하거나 영상을 확인하는 방법을 제안하고 구현하였다. 제안하는 시스템은 서버 컴퓨터는 카메라의 영상을 받고 팬틸트 컨트롤을 하게한다. 클라이언트 컴퓨터는 PC와 PDA를 이용하여 서버에 접속한 뒤 실시간으로 영상을 받아오고 카메라 팬틸트를 컨트롤 한다. 본 논문에서 제안한 내용은 Wi-Fi가 사용가능한 곳에 있는 사용자가 언제 어디서나 감시카메라의 영상을 보고 컨트롤 하는데 유용할 것이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.687-688
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• 2009

차세대 무선 통신 기술인 Wi-Fi는 이동통신사를 거치지 않고 근처의 AP(Access Point)를 통하여 여러 컨텐츠 제공서버에 접근한다. 그에 따라 사용자는 컨텐츠 제공서버로 위장한 피싱이나, 인증되지 않은 사이트를 통해 악성코드 배포, 사용자 정보유출등과 같은 취약점에 노출되고, 컨텐츠 제공 서버 또한 타인으로 위장한 위장공격등과 같은 취약점에 노출된다. 본 논문에서는 Wi-Fi 환경 내에서 사용자 단말기와 컨텐츠 제공서버간의 상호 인증 방안을 모색하고, 모바일 환경의 특성을 고려한 상호 인증 방안을 제안한다.

• ETRI Journal
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• v.45 no.6
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• pp.939-951
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• 2023

It is critical to estimate the location using only Long-Term Evolution (LTE) and Wi-Fi information gathered by the user's smartphone and deployable for emergency rescue, regardless of whether the Global Positioning System is received. In this research, we used a vehicle to gather LTE and Wi-Fi wireless signals over a large area for an extended period of time. After that, we used the learning technique to create a positioning database that included both collection and noncollection points. We presented a two-step positioning algorithm that utilizes coarse localization to discover a rough location in a wide area rapidly and fine localization to estimate a particular location based on the coarse position. We confirmed our technology utilizing different sorts of devices in four regional types that are generally encountered: dense urban, urban, suburban, and rural. Results presented that our algorithm can satisfactorily achieve the target accuracy necessary in emergency rescue circumstances.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2734-2747
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• 2018

In this study, a novel fractal ring antenna with a compact size of $24{\times}9{\times}0.8mm^3$ was configured using three iterations. Low profile, circular polarization, and measured operating bands (4.5-6.5 GHz) meet specifications of the upper band used in Wi-Fi and WiMAX applications. The antenna featured, stable radiation properties, especially gain and efficiency, in the notched band (92%). In deep, the antenna impedance, reflection coefficients, surface current distribution and circular polarization for the three iterations had been studied to improve the process of antenna design and its radiation characteristics.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.153-155
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• 2010

Internet phone (VoIP) services in Korea have achieved noticeable growth year after year since the service launching, and the growth still coninues. The market of mobile internet phone also expands sharply. Therefore, it is crucial to deploy networks which can support mobile internet phone services with excellent quality. For mobile internet phone services, it will be necessary to build and use networks with good mobility and high transmission rate. Current wireless networks for Internet services include 3G, Wi-Fi, and mobile WiMAX networks. 3G provides good mobility but lower transmission rate, whereas Wi-Fi exhibits excellent transmission rate but less mobility. Mobile WiMAX networks taking the merits of both, high mobility and transmission rate, are being deployed widely in recent years. This article examines the recent standardization efforts of WiMAX Forum for VoIP service in WiMAX networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.10
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• pp.2345-2351
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• 2013

LBS(Location Based System) usually uses GPS technology to measure the exact position of the moving object. However, the method of managing location which utilizes the WiFi technology of mobile phone has not been introduced so far. The method of managing moving objects in view of the location of guardian has also not been proposed. In this paper, a new location management system of moving objects which take guardian's location into consideration is proposed. Specifically, the three methods of searching for missing child proposed in this paper are as follows : 1) a method based on an app for smart phone, 2) a method based on control server, 3) a method based on control server and fixed APs. Because the proposed system reflects the location of the guardian, the guardian is able to identify the state of child immediately and the workload can be reduced.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.43-49
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• 2020

In spite of the notable advancements of millimeter wave communication technologies, the 60 GHz Wi-Fi is still not widespread yet, mainly due to the high limitation of coverage. Conventionally, it has been hardly possible to support a high data rate with fast beam adaptation while keeping atmospheric beamforming coverage. To solve these challenges in the 60 GHz communication system, holistic system designs are considered. we implemented an enhanced design LDPC decoder enabling 6.72 Gbps coded-throughput with minimal implementation loss, and our proposed phase-tracking algorithm guarantees 3.2 dB performance gain at 1 % PER in the case of 16 QAM modulation and LDPC code-rate 3/4.