• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.565-573
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• 2016

Wi-Fi Direct standard technology(Wi-Fi Peer to Peer Technical Specifications v1.2, 2010) was designed for allowing peer to peer communication between two or more devices and various products which have been currently manufactured such as smart phone and smart TV have already provided this technical function. In this technology the role of Coordinator in Wi-Fi infrastructure would be matched to GO(Group Owner) which needs relatively high energy resource and computation power due to the high probability for allowing 3rd-party connection, however, the current standard specification would be limited in terms of energy distribution because it has not included a process to determine the role of GO. To address above problem, this paper classified considerable parameters into the general parameters for the physicality of devices and the specific parameters for considering the role position depending on use-case scenario, and proposed a new method called DIVA to help efficiently determining GO role from the member devices of Wi-Fi Direct network. Furthermore the effect of this mechanism was proved via simulation-based experiments.

• 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.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.1
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• pp.38-44
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• 2021

Wi-Fi provides some low-power connection solutions that other Bluetooth cannot provide, and at the same time brings many benefits. First, there is a potentially higher data rate: it can reach 230mbps. Wi-Fi coverage is also wider than competitors, and its operating frequency is also 5GHz, which is much less congested than 2.4GHz. Finally, it also supports IP networks, which is important if you want to send data to the cloud without complexity. The 802.11ac standard of the previous generation still accounts for most shipments (80.9%) and revenue (76.2%). However, there is a limit to accepting IoT devices that will continue to increase significantly in the future. To solve this problem, the new Wi-Fi 6 standard is expected to be the solution (IEEE 802.11ax) which is quickly becoming the main driving force of the wireless local area network (WLAN) market. According to IDC market research analysts, in the first quarter of 2020, independent access points (APs) supported by Wi-Fi 6 accounted for 11.8% of shipments, but 21.8% of revenue. In this paper, we have compared and analyzed the IoT connectivity, QoS, and security requirements of devices using Wi-Fi 6 network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.631-639
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• 2016

Wi-Fi Direct standard technology has been widely deployed on the recently manufactured products such as smart phone, smart monitor, TV, set-top box, and gaming console, and it was published from Wi-Fi Alliance with the name of Wi-Fi Peer-to-Peer Technical Specifications (v1.4, 2014) for direct connection on the wireless communication environment. However, the connection process of this standard needs 5 to 10 seconds so it can lead to user's inconvenience as well as long delay for connection. From the focus of that this problem was derived from long discovery process composed of Scan and Find, as a result, the proposed scheme on this paper modified and adapted Scan and Find processes with reassembling steps of them for reducing the connection delay. In addition, the analysis and experiments were progressed for the evaluations of the proposed scheme.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.585-594
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• 2017

Wireless Docking system can provide enhanced convenience to user experience of handheld device such as smart phone by using previously deployed peripheral devises such as monitor and keyboard. In this environment, user can easily use the handheld device with variable peripheral devices at any docking system place. This system would be composed of peripherals except host computing device contrarily to previous desktop and laptop environment. For this system, Wi-Fi Alliance has been developing standard technology based on Wi-Fi Direct(Wi-Fi Peer-to-Peer Technical Specifications v1.2, 2010) technology. However, this system can make a problem which may lead to complex connectivity on handheld device due to non-compatible communication interface. To address given problem, we designed a new method of Bluetooth tunneling technology via previous Wi-Fi Direct communication, and evaluated it with experiment results.

• MALSORI
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• no.56
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• pp.135-145
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• 2005

In this paper, a WiFi phone system with distributed speech recognition is implemented. The WiFi phone with voice-activated dialing and its functions are explained. Features of the input speech are extracted and are sent to the interactive voice response (IVR) server according to the real-time transport protocol (RTP). Feature extraction is based on the European Telecommunication Standards Institute (ETSI) standard front-end, but is modified to reduce the processing time. The time for front-end processing on a WiFi phone is compared with that in a PC.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.83-88
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• 2006

Many applications in the area of location-based services and personal navigation require nowadays the location determination of a user not only in outdoor environment but also indoor. To locate a person or object in a building, systems that use either infrared, ultrasonic or radio signals, and visible light for optical tracking have been developed. The use of WiFi for location determination has the advantage that no transmitters or receivers have to be installed in the building like in the case of infrared and ultrasonic based location systems. WiFi positioning technology adopts IEEE802.11x standard, by observing the radio signals from access points installed inside a building. These access points can be found nowadays in our daily environment, e.g. in many office buildings, public spaces and in urban areas. The principle of operation of location determination using WiFi signals is based on the measurement of the signal strengths to the surrounding available access points at a mobile terminal (e.g. PDA, notebook PC). An estimate of the location of the terminal is then obtained on the basis of these measurements and a signal propagation model inside the building. The signal propagation model can be obtained using simulations or with prior calibration measurements at known locations in an offline phase. The most common location determination approach is based on signal propagation patterns, namely WiFi fingerprinting. In this paper the underlying technology is briefly reviewed followed by an investigation of two WiFi positioning systems. Testing of the system is performed in two localization test beds, one at the Vienna University of Technology and the second at the Hong Kong Polytechnic University. First test showed that the trajectory of a moving user could be obtained with a standard deviation of about ${\pm}$ 3 m.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2218-2229
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• 2015

Recently Wi-Fi Alliance defined Wi-Fi direct, which can communicate through a direct connection between the mobile device anytime, anywhere. In Wi-Fi direct, all devices are categorized by group of owner (GO) and client. Since portability is emphasized in Wi-Fi direct devices, it is essential to control the energy consumption of a device very efficiently. In order to avoid unnecessary power consumed by GO, Wi-Fi direct standard defines two power management schemes: Opportunistic power saving scheme and Notice Of Absence (NOA) scheme. But, these two schemes do not consider the traffic pattern, so we cannot expect high energy efficiency. In this paper, we suggest an algorithm to enhance the energy efficiency of Wi-Fi direct power saving, considering the characteristics of multimedia video traffic. Proposed algorithm utilizes the statistical distribution for the size of video frames and adjusts the length of awake interval dynamically. Also, considering the inter-dependency among video frames, the proposed algorithm assigns priorities to video frames and ensures that a video frame with high priority is transmitted with higher probability than other frames with low priority. Simulation results shows that the proposed method outperforms the traditional NOA in terms with average delay and energy efficiency.

• 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.