• Electronics and Telecommunications Trends
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• v.33 no.5
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• pp.64-75
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• 2018

People usually check their social media, e-mail, and online news on their smartphones using their carrier network. During this process, much of the data traffic is offloaded to ubiquitous Wi-Fi networks. Such offloading will continue to increase rapidly because of flourishing public Wi-Fi networks located around the world. In this technical report, we first investigate domestic public Wi-Fi projects, and followed by foreign projects. In addition, we investigate the Wi-Fi technology evolution that has been standardized in IEEE 802. More and more people are tending to use Wi-Fi, not only at home or work, but also on public transport such as buses and trains. Hence, it is important to come up with ideas that can realize Wi-Fi onboard. The key technologies needed here are related to a mobile wireless backhaul between trains and trackside radio equipment, or between buses and roadside units. Thus, we also investigate the mobile wireless backhaul technologies and their trends.

• Journal of Broadcast Engineering
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• v.23 no.1
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• pp.154-161
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• 2018

As the number of smartphone users increases, research on indoor location recognition service is necessary. Access to indoor locations is predominantly WiFi, Bluetooth, etc., but in most quarters, WiFi is equipped with WiFi functionality, which uses WiFi features to provide WiFi functionality. The study uses the random forest algorithm, which employs the fingerprint index of the acquired WiFi and the use of the multI-value classification method, which employs the receiver signal strength of the acquired WiFi. As the data of the fingerprint, a total of 4 radio maps using the Mac address together with the received signal strength were used. The experiment was conducted in a limited indoor space and compared to an indoor location recognition system using an existing random forest, similar to the method proposed in this study for experimental analysis. Experiments have shown that the system's positioning accuracy as suggested by this study is approximately 5.8 % higher than that of a conventional indoor location recognition system using a random forest, and that its location recognition speed is consistent and faster than that of a study.

• TTA Journal
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• s.102
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• pp.151-160
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• 2005

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.99-101
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• 2011

본 논문에서는 WiMAX 의 신호세기(CINR: Carrier to Interference + Noise Ratio)의 변화와 예측 방법에 대해 연구한다. WiMAX 와 같은 무선 네트워크에서는 신호세기가 불규칙하게 변화하기 때문에 비디오 스트리밍시 에러나 지연이 발생할 수 있다. CINR 은 클라이언트 측의 가용 대역폭을 결정하는 중요한 요소이다. 하지만 기존의 RTCP(Real-time Transport Control Protocol)를 이용한 비트율 제어는 RTT(Round Trip time), PLR(Packet Loss Rate) 등의 정보를 사용하기 때문에 부정확하거나 지연이 발생될 수 있다. 이를 보완하기 위한 CINR 을 직접 비트율 제어에 사용하는 방법에 대해 연구하기에 앞서, 본 논문에서는 CINR 을 분석하고 미래의 값을 예측하는 방법에 대해 연구한다. 본 논문의 분석을 통해 CINR 의 예측을 비교적 정확하게 수행할 수 있다면 앞으로의 가용 대역폭을 비교적 정확하게 예측할 수 있고 효율적인 비디오 스트리밍 시스템을 제안할 수 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.291-293
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• 2012

급격히 증가하는 모바일 디바이스에 의한 모바일 데이터 요구량을 처리하기 위해 가장많이 고려되고 있는 IEEE 802.11의 WLAN은 셀룰러보다 높은 데이터 전송속도를 제공하지만 이동성이 고려되어있지 않다. 이에 본 논문에서는 Enterprise WLAN에서 IEEE 802.21 MIH 표준에 기반하여 Media Independent Information Server (MIIS)로부터 수신된 주변 AP들의 네트워크의 정보를 바탕으로 후보 엑세스 AP 네트워크를 선정 및 WiMAX에 make-before-break 핸드오버하는 방안을 제안한다. 제안하는 방안은 실제 Enterprise WLAN와 Mobile WiMAX 환경에서 이동하는 단말의 시간에 따른 TCP throughput에 대한 성능평가를 하였다. 이를 통해 제안하는 방안의 평균TCP throughput 성능이 9.04Mbits/s으로 기존 방안의 TCP throughput 성능 6.49Mbits/s보다 약 40%향상됨을 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.168-171
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• 2016

In recent years, indoor localization in Wi-Fi environment has been researched for its location determining capability. The fingerprint and RF propagation models has been the main approach in determining indoor positioning. With the use of fingerprint, a low-cost, versatile localization system can be achieved without the use of external hardware. However, only a few research have been made on virtual access points (VAPs) among indoor localization models. In this paper, the idea of indoor localization system using fingerprint with the addition of VAP in Wi-Fi environment is discussed. The idea is to virtually add APs in the existing indoor Wi-Fi system, this would mean additional virtually APs in the network. The experiments of the proposed algorithm shows the positive results when 2VAPs are used compared with only APs. A combination of 3APs and 2VAPs had the lowest average error in all 4 scenarios with 3.99 meters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1463-1471
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• 2016

The indoor localization algorithm using the Difference Means based on Fingerprint (DMFPA) to improve the performance of indoor localization in moving Wi-Fi environment is proposed in this paper. In addition to this, the performance of the proposed algorithm is also compared with the Original Fingerprint Algorithm (OFPA) and the Gaussian Distribution Fingerprint Algorithm (GDFPA) by our developed indoor localization simulator. The performance metrics are defined as the accuracy of the average localization accuracy; the average/maximum cumulative distance of the occurred errors and the average measurement time in each reference point.

• Electronics and Telecommunications Trends
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• v.21 no.5 s.101
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• pp.11-20
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• 2006

USB는 사용의 편리성, 넓은 확장성을 기반으로 PC 역사상 가장 성공적인 접속 장치로서, 현재까지 20억 개 이상이 사용되고 있고, USB가 장착된 장치의 종류 및 사용 개수도 빠르게 증가하는 추세이다. 이와 같은 USB의 발전에 힘입어 유선의 속도와 보안성에 무선의 편리함을 추가한 무선 USB 1.0 규격이 2005년 5월 발표되었으며, 상용 제품도 속속 출시되고 있다. 본 고는 유선 USB 2.0 기술에 기반하고 무선 매체로서UWB를 이용하는 무선 USB의 기술 및 표준화 동향에 대하여 소개하고, 무선 USB 기술의 특징 및 국내외 연구 동향에 대하여 살펴보고자 한다.

• Journal of Korea Multimedia Society
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• v.19 no.11
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• pp.1871-1877
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• 2016

In this paper, a Wireless USB (WUSB) protocol is adopted for development of ASMD (Adaptive Source Multi Device) N-screen wireless services. WUSB is the USB technology merged with WiMedia PHY and Distributed-MAC (D-MAC). However, the current WUSB protocol can't provide seamless N-screen streaming services to moving WUSB devices in home network environment. Therefore, to provide the ASMD N-screen services through WUSB based on D-MAC protocol, a channel management scheme is proposed to support seamless mobility between adjacent ASMD groups for wireless IPTV N-screen services. In simulation results, proposed ASMD channel management (ACM) scheme is compared with conventional WUSB channel management scheme in view points of throughput, average path interference and energy consumption according to various numbers of nodes and elapsed simulation times. Through simulation results, it is explained that proposed ASMD channel management (ACM) scheme should be adopted in the WUSB protocol to realize ASMD N-screen wireless services.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.263-264
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• 2008

고속 무선 PAN(Personal Area Networks)기술은 10m 이내의 짧은 거리에서 고속으로 대용량의 데이터를 전송하기 위한 기술로, 최근 무선 USB(Wireless Universal Serial Bus)나 HDTV(High Definition TV)와 같은 광대역 멀티미디어 응용 시장을 겨냥한 연구가 IEEE 802.15.3과 WiMedia를 중심으로 활발히 진행되고 있다. [1] 본 논문에서는 WiMedia Alliance에서 제안한 Distributed Medium Access Control (D-MAC)에서 다수 스트림의 QoS 요구를 만족시키는 신뢰성 있는 전송을 위해 데이터 시간 슬롯을 효율적으로 할당하는 알고리즘에 대해 연구하고자 한다.