• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.47-48
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• 2012

스마트폰 보급과 Wi-Fi 기술의 대중화로 다양한 서비스가 가능해졌지만 현재까지도 Wi-Fi 이용을 위해서는 많은 소요시간과 사용자의 개입이 필요하다. 본 논문에서는 Wi-Fi 이용에 필요한 과정과 각 과정의 소요시간을 측정/분석하고, NFC기술을 이용하여 사용자의 불필요한 개입 없이도 신속하게 Wi-Fi 접속을 가능하게 하는 기법을 제안한다.

• Information and Communications Magazine
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• v.32 no.3
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• pp.69-76
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• 2015

무선랜(Wireless LAN)으로도 불리는 Wi-Fi 기술은 1997년 IEEE 802.11 전송 규격(Legacy Standard)이 출간된 이후 지속적인 보완과 개정 작업을 통해 그 규격이 발전되어 가며 스마트폰, Tablet, Note-PC 등 개인 휴대 단말 기기를 위한 데이터 네트워크의 필수적인 구성 요소가 되었다. IEEE 표준과 별도로 표준 인증기관인 Wi-Fi Alliance를 통하여 제품 간 무선연결 호환성의 확보 뿐 아니라 Wi-Fi 기반 서비스 규격 제정에 이르기까지 Wi-Fi 표준 작업이 수행되고 있다. 본고에서는 나날이 발전해 온 Wi-Fi 기술 표준을 전송 속도 향상 측면과 주파수 대역 확장 측면에서 살펴보고, 차세대 Wi-Fi 기술인 IEEE 802.11ax, 즉 HEW(High Efficiency WLAN) 표준에 대하여 살펴보도록 한다.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.436-442
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• 2005

컨버전스시대의 도래에 따라 다양한 유무선통합서비스를 지원하기 위한 embedded WiFi 기술이 모바일 PC, PDA, 핸드폰, TV, PMP, 카메라, 비디오 게임기 및 로봇 장남감에 이르기 까지 다양하게 적용되고 있다. 이에 다양한 단말의 형태를 고려한 무선구간의 성능확보가 요구되고 있는 실정으로 본 논문에서는 DBDM (Dual Band Dual Mode) 단말인 NESPOT Swing 단말을 근간으로 안테나 위치 최적화에 대한 기술과 단말 RF 및 기지국 안테나의 특성을 고려한 필드 성능 측정 방법에 대하여 기술하고, 이론적 분석과 실측정치를 제시하고자 한다. 본 연구의 결과는 앞으로 다양한 환경에서 사용이 예상되는 WiFi 기지국의 설치 및 embedded WiFi 단말의 안테나 구성과 RE모듈 성능 확보에 활용될 수 있을 것으로 기대된다.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.49-54
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• 2021

Indoor positioning system becomes of increasing interests due to the demands for accurate indoor location information where Global Navigation Satellite System signal does not approach. Wi-Fi access points (APs) built in many construction in advance helps developing a Wi-Fi Received Signal Strength Indicator (RSSI) based indoor localization. This localization method first collects pairs of position and RSSI measurement set, which is called fingerprint database, and then estimates a user's position when given a query measurement set by comparing the fingerprint database. The challenge arises from nonlinearity and noise on Wi-Fi RSSI measurements and complexity of handling a large amount of the fingerprint data. In this paper, machine learning techniques have been applied to implement Wi-Fi based localization. However, most of existing indoor localizations focus on single position estimation. The main contribution of this paper is to develop multi-target localization by using deep neural, which is beneficial when a massive crowd requests positioning service. This paper evaluates the proposed multilocalization based on deep learning from a multi-story building, and analyses its learning effect as increasing number of target positions.

• International Journal of Advanced Culture Technology
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• v.11 no.1
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• pp.395-402
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• 2023

The implementation of a hybrid network utilizing Power Line Communication (PLC) and Wi-Fi technologies has been demonstrated to improve signal strength and coverage in areas with poor connectivity due to internet shadow areas. In this study we strategically positioned Wi-Fi relays and utilized the capabilities of PLC technology to significantly improve signal strength and coverage in areas with poor connectivity. We also analyzed the effects of metallic obstacles on Wi-Fi signal propagation and proposed a solution to strengthen the signal enough to pass through them. Our experiment demonstrated the feasibility and potential of using this hybrid network in industrial scenarios for real-time data transmission. Overall, the results suggest that the use of PLC and Wi-Fi hybrid networks can be a cost-effective and efficient solution for overcoming internet connectivity challenges and has the potential to provide high-speed internet access to areas with unreliable signals.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.5
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• pp.1735-1754
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• 2022

The reliability and performance of WiFi need optimization because of the rising number of WiFi users day by day. A highlighted point is saving power while transmitting and receiving packets using WiFi devices. Wake-on-Wlan (WoW) is also implemented to improve energy consumption, but it also needs betterment. This paper will introduce universal ideas to transmit and receive packets using low-power technology like Bluetooth or BLE (Bluetooth low energy). While looking for power-saving ways in this research, WiFi connection and maintenance also take care using lesser power-consuming technology. Identifying different use-cases where low power technology can help save energy and maintain 802.11 connection is part of the research. In addition, the proposed method discuss energy saving with unicast and broadcast/multicast data. Calculation of power-saving and comparison with standalone WiFi usage clearly shows the effectiveness of the proposed method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.717-720
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• 2020

An indoor localization system that uses Wi-Fi RSSI signals for localization gives accurate user position results. The conventional Wi-Fi RSSI signal based localization system uses raw RSSI signals from access points (APs) to estimate the user position. However, the RSSI values of a particular location are usually not stable due to the signal propagation in the indoor environments. To reduce the RSSI signal fluctuations, shadow fading, multipath effects and the blockage of Wi-Fi RSSI signals, we propose a Wi-Fi localization system that utilizes the advantages of Wi-Fi RSSI heat maps. The proposed localization system uses a regression model with deep convolutional neural networks (DCNNs) and gives accurate user position results for indoor localization. The experiment results demonstrate the superior performance of the proposed localization system for indoor localization.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.601-606
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• 2015

Recently wireless data services have widely spread on various multimedia devices such as smart phones and tablets. Existing wired data services have been replaced by wireless data services using mobile devices. Especially domestic mobile devices supporting both Wireless-Fidelity (Wi-Fi) and long term evolution (LTE) services have increased steadily. While Wi-Fi network is provided free of charge, LTE network is offered to pay for. Therefore, mobile devices provide smart network switch to support both preferred Wi-Fi and LTE networks. However, such handover and roaming between Wi-Fi and LTE networks can cause data connection stop in spite of charged data services. This paper has proposed the method to overcome data connection stop for guaranteeing seamless data service during handover and roaming procedures between networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.8
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• pp.663-671
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• 2013

Recently, the Wi-Fi Direct standard based on WLAN is getting more attention as a new technology for enabling D2D(Devide-to-Device) communications on mobile devices. However, due to limited power resource of mobile devices and, an energy inefficiency problem can be an issue. In order to solve this problem, the Wi-Fi Direct defines two power management schemes: Opportunistic scheme and Notice of Absence(NoA) scheme. However, there is no concrete description of which power management scheme would be better for when. In this paper, via comprehensive simulation studies using ns-3, we show that each scheme presents obviously different performance and energy efficiency according to data traffic patterns. We then propose more energy efficient way of dynamically switching the two power management schemes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1939-1946
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• 2012

USNs (Ubiquitous Sensor Networks) such as IEEE 802.15.4 ZigBee network share ISM (Industrial, Scientific, and Medical) frequency band with WiFi networks. Once both networks operate in a region, packet collision may happen because of frequency overlapping. To assure this possibility, we conducted experiments where WiFi and ZigBee communication networks had been installed in an area. As a result of the test, successful data transmission rate were reduced due to the frequency overlapping between a WiFi communication channel and a ZigBee communication band. To cope with this problem, we propose a collision avoidance algorithm. In the proposed algorithm, if frequency collision is sensed, new communication channel with different frequency band is allocated to each node. Performance of the proposed frequency collision avoidance algorithm was tested and the results were described.