• Journal of Platform Technology
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• v.8 no.2
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• pp.10-21
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• 2020

The use of WiFi is gradually increasing through the spread of mobile terminals and the development of data communication. Mobile Internet usage has been steadily increasing from the 2000s to the present. Almost all households in Korea have smart devices, and 90% of the population uses mobile Internet. Due to this trend, the government is currently constructing public WiFi zones in dense urban areas as a way to reduce communication costs. The WiFi usage in the public WiFi zone is increasing every year. Therefore, in this paper, we propose a method for using such public WiFi efficiently. A mobile terminal collects WiFi information and constructs a WiFi zone in a map using a concave hull algorithm. In the map, the mobile terminal provides a route through many public WiFi areas. As a result, the WiFi usage of the mobile terminal is increased through more WiFi regions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5479-5486
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• 2012

In this paper, we have measured PRR, RSSI and LQI of ZigBee channels under Wi-Fi environment and have assessed channel characteristic and link quality. To confirm any relationship among RSSI, LQI values and PRR under Wi-Fi interference in overlapping and non-overlapping channels of Wi-Fi and ZigBee, the experiments were performed without Wi-Fi, with Wi-Fi and file download through Wi-Fi. Under Wi-Fi interference, We perfomed experiments to ensure channel characteristics and link quality by fixing Wi-Fi and ZigBee receiver and varying the distance between ZigBee receiver and transmitter. ZigBee transmitter sends packet of 256 bits every second to ZigBee receiver. PRR was measured from ZigBee with variance of distance between fixed Wi-Fi and ZigBee. RSSI, LQI, PRR were measured from ZigBee with fixed Wi-Fi, fixed ZigBee receiver and variance of distance of ZigBee transmitter. As a result, we confirmed decrease of PRR under Wi-Fi interference but RSSI, LQI values similar regardless of overlapped or non-overlapped channel and Wi-Fi interference. Therefore, PRR should be used for interference detection in ZigBee communication under Wi-Fi environment but RSSI and LQI are not appreciate.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.476-483
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• 2016

Super Wi-Fi is a Wi-Fi-like service exploiting TV white space (WS) which is expected to achieve larger coverage than today's Wi-Fi thanks to its superior propagation characteristics. Super Wi-Fi has been materialized as an international standard, IEEE 802.11af, targeting indoor and outdoor applications, and is undergoing worldwide field tests. This paper demonstrates the true potential of indoor Super Wi-Fi, by experimentally comparing the signal propagation characteristics of Super Wi-Fi and Wi-Fi in the same indoor environment. Specifically, we measured the wall and floor attenuation factors and the path-loss distribution at 770MHz, 2.401 GHz, and 5.540 GHz, and predicted the downlink capacity of Wi-Fi and Super Wi-Fi. The experimental results have revealed that TVWS signals can penetrate up to two floors above and below, whereas Wi-Fi signals experience significant path loss even through a single floor. It has been also shown that Super Wi-Fi mitigates shaded regions of Wi-Fi by providing almost-homogeneous data rates within its coverage, performs comparable to Wi-Fi utilizing less bandwidth, and always achieves better spectral efficiency than Wi-Fi. The observed phenomena imply that Super Wi-Fi is suitable for indoor applications and has the potential of extending horizontal and vertical coverage of today's Wi-Fi.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1050-1057
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• 2012

Super Wi-Fi is a newly emerging wireless Internet technology, which constitutes Wi-Fi networks using TV white space. A key technical challenge in the Super Wi-Fi applications is how to provide a seamless Internet service even when a Super WiFi user should give up the channel in use to the active incumbent user which is activated in the same service area, preventing from the service continuity in Super Wi-Fi. In this paper, we propose a channel handover method to support service continuity of Super Wi-Fi, in which an AP selects a new operational channel and provides the channel information for MSs. Therefore, the AP and the MSs can carry out seamless handover for Super Wi-Fi service. A performance evaluation shows that the proposed scheme is superior to the conventional Wi-Fi in channel mobility delay.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.167-172
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• 2010

This paper is to implement HSDPA-CPE that can provides WiFi terminal with wireless Internet service through the connection to HSDPA wireless network. This system aims to support HSDPA interface in upstream, and WiFi and 100Mbps Ethernet interface in downstream. So, this system can provide multiple Internet customers with wireless Internet service by using WiFi terminal in subway, car, ship, and so on, and WiFi terminals that be registered in HSDPA service can be connected to Internet.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.186-188
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• 2014

In recent years, domestic as well as LTE wireless network of Wi-Fi and most used. In addition, mobile-intensive services that used mainly in our society makes it easier, SNS, application (APP), and file downloads. As such, the amount of data requested, while living at the time of mobile users will want to be safe from the earliest. And the wireless network communications mortality (3G, 4G (LTE), LTE-A) and Wi-Fi (802.11 n-2.4 G H z z H a c-5, 802.11 G), and users are mainly used in the death 4G (LTE), communication Wi-Fi, 802.11 n-2.4 GHz are used most frequently. As above, use the wireless network in order to safely and quickly developed the technology of the Li-Fi. Li-Fi light (visible light) technology to communicate with, and Wi-Fi (802.11 n-2.4 G z H) 100 times faster, LTE-A 66 times faster. However, the current Li-Fi to commercialise the big issue exists. In this paper, there are a lot of existing problems in the commercialization of Li-Fi being used in Wi-Fi, and a comparative analysis.

• Electronics and Telecommunications Trends
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• v.26 no.5
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• pp.74-82
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• 2011

최근 Wi-Fi Alliance는 Wi-Fi 기반의 Peer-to-Peer(P2P) 규격인 Wi-Fi Direct 기술의 발표와 함께 인증을 진행하고 있다. Wi-Fi Direct 기술은 TV, 노트북, 프린터, 카메라와 같은 휴대기기 및 모바일 단말 등에 탑재되어 Access Point(AP) 또는 라우터와 같은 별도의 장비 없이도 단말 간 직접 통신을 통하여 기기 간 콘텐츠 및 서비스를 사용할 수 있는 기반을 제공하는 기술이다. Wi-Fi Direct 기술은 빠른 전송속도와 전송거리를 제공함으로써 향후 일부 영역에서 블루투스 기술을 대체할 수 있을 것으로 기대된다. 또한 향후 Wi-Fi Direct 규격의 전체 기능을 구현한 스마트폰이 출시된다면 사용자 경험(UX)을 극대화 시킬 수 있는 혁신적인 모바일 서비스를 제공할 수 있을 것으로 기대된다. 본 고에서는 Wi-Fi Direct의 업계 동향과 Wi-Fi Direct의 동작 원리를 표준 기술 규격서를 통해 분석하여 요약 정리한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.678-681
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• 2009

WiFi는 무선인터넷 접속(Wireless LAN) 방식의 하나로서 이동성, 설치용이성, 유연성 등으로 인하여 널리 사용되고 있다. 더욱이 기존 다양한 디지털 기기들이 WiFi 기반의 application을 탑재하여 각종 온라인 콘텐츠를 이용할 수 있게 하면서 점차 보편적인 인터넷 접속수단으로서 변모하고 있는 상황이다. WiFi의 편리성으로 인하여 기업, 공공기관, 교육기관 등에서 네트워크 구축에 WiFi를 사용하는데 그 추세가 개인부문에서 기업부문으로 확산되고 있다. 하지만 유선인터넷이 케이블이라는 매체를 통해 연결되어 외부와 차폐된데 비해 WiFi는 주파수를 매개로하기 때문에 네트워크 접근이 용이하며 이로인해 보안이 취약해 질 수 있다는 것이다. 이로 인하여 일명 워드라이빙(war driving)이라 불리는 서비스의 무단사용뿐만 아니라 악의를 가진 네트워크 침입이 가능해져 개인정보나 사유재산이 침해 가능성이 높다고 할 수 있다. 이에 본 연구에서는 해외의 WiFi의 보안관련 법제도를 살펴보고 이로부터 국내 WiFi보안을 위한 대안을 제시하고자 한다.

• Journal of Food Hygiene and Safety
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• v.29 no.4
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• pp.305-311
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• 2014

Minimum infective dose (MID) data has been recognized as an important and absolutely needed in quantitative microbiological assessment (QMRA). In this study, we performed a comprehensive literature review and meta-analysis to better quantify this association. The meta-analysis applied a final selection of 82 published papers for total 12 species foodborne disease pathogens (bacteria 9, virus 2, and parasite 1 species) which were identified and classified based on the dose-response models related to QMRA studies from PubMed, ScienceDirect database and internet websites during 1980-2012. The main search keywords used the combination "food", "foodborne disease pathogen", "minimum infective dose", and "quantitative microbiological risk assessment". The appropriate minimum infective dose for B. cereus, C. jejuni, Cl. perfringens, Pathogenic E. coli (EHEC, ETEC, EPEC, EIEC), L. monocytogenes, Salmonella spp., Shigella spp., S. aureus, V. parahaemolyticus, Hepatitis A virus, Noro virus, and C. pavum were $10^5cells/g$ (fi = 0.32), 500 cells/g (fi = 0.57), $10^7cells/g$ (fi = 0.56), 10 cells/g (fi = 0.47) / $10^8cells/g$ (fi = 0.71) / $10^6cells/g$ (fi = 0.70) / $10^6cells/g$ (fi = 0.60), $10^2{\sim}10^3cells/g$ (fi = 0.23), 10 cells/g (fi = 0.30), 100 cells/g (fi = 0.32), $10^5cells/g$ (fi = 0.45), $10^6cells/g$ (fi = 0.64), $10{\sim}10^2particles/g$ (fi = 0.33), 10 particles/g (fi = 0.71), and $10{\sim}10^2oocyst/g$ (fi = 0.33), respectively. Therefore, these results provide the preliminary data necessary for the development of foodborne pathogens QMRA.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.55-61
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• 2016

As the price-performance ratio of embedded PCs improves, the benefits of the PC-Fi can be maximized by designing an embedded PC-Fi system. In this paper presents the design of an embedded PC-Fi that can be manipulated by a remote controller based on mobile devices such as smart phones or tablets. Additionally, an interactive control system and its GUI, through which the user can select and play music as they like at ease, are presented. The case that a large amount of music is stored in the PC-Fi system requires a function allowing the user to easily select the music they want to listen to. In order to implement this function, a DB containing detailed information of each track can be used to find the location of the desired music with keywords provided by the user. In this proposed system, the embedded PC-Fi system and remote controller are mutually connected via a WiFi network, and more than one user can remotely control the embedded system with their own mobile device.