• 한국통신학회논문지
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• 제39C권8호
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• pp.696-707
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• 2014

본 논문에서는 UWB 기술 기반 무선 USB(WUSB) 프로토콜에서, 디바이스들의 이동성으로 인해 발생하는 Private Distributed Reservation Protocol (DRP) 예약 충돌 현상을 분석한다. 그리고 Private DRP 예약 충돌 시 발생하는 성능 저하를 감소시키기 위해 Private DRP 릴레이 통신 기술을 제안한다. 본 논문에서 제안하는 Private DRP 릴레이 통신 프로토콜은 충돌대상 디바이스에게 예약된 자원을 유지할 수 있도록 Direct Link 뿐만 아니라, Private DRP 예약 충돌 시 릴레이 노드를 경유하여 또 다른 Indirect Link 링크를 빠르게 예약할 수 있는 분산적인 자원 예약 프로토콜을 제안한다.

• Journal of information and communication convergence engineering
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• 제8권4호
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• pp.399-404
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• 2010

We propose a seamless IPTV transport technology of mobile device. This technology uses multiple interfaces of wireless communication on mobile device. This proposal for transportation of mobile IPTV contents is more mobile and adaptable than other wireless technologies that are currently being used. Algorithm of proposed technology is as follow. When the signal strength of the connected wireless network interface of mobile device is getting lower than specified level, another wireless network interface is connected to continue downloading the IPTV contents in advance. Another connection is maintained until the signal strength of the first connected interface is stable or the interface is connected to another base station (or AP) that have good signal strength. For more seamless services, we consider classifying the packets of mobile IPTV and using dynamic content quality select techniques. Dynamic content quality selection is based on notifying transfer rate to the content delivery network (CDN) server. The proposed technology is expected to use efficiently with both mobile IPTV and the transportation of mobile P2P/P4P.

• 전기학회논문지
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• 제64권5호
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• pp.739-745
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• 2015

In this paper, a flexible wireless power receiving system is proposed for wearable device applications. The proposed system is designed with printable component configuration to be integrable to textile material. While the defected ground structures(DGSs) are utilized for planar printable filter designs, direct impedance matching technique is considered for flexible circuit performance. The proposed system has been implemented on a flexible substrate with a thickness of 5 mils, and experimented for power conversion efficiencies and converted voltages. In order to evaluate the hardware flexibility, the system performance are measured a bended circuit board at a radius of curvature of 5 cm. The system performance is analyzed for the degradation due to the curvature. The proposed system has shown the excellent capability of far-field wireless power transfer systems in flexible device environments.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.569-575
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• 2014

A highly efficient class E power amplifier is demonstrated for application to wireless power transfer system. The amplifier is designed with an L-type matching at the output for harmonic rejection and output matching. The power loss and the effect of each component in the amplifier with the matching circuit are analyzed with the current ratio transmitted to the output load. Inductors with a quality factor of more than 120 are used in a dc feed and the matching circuit to improve transmission efficiency. The single-ended amplifier with 20 V supply voltage shows 7.7 W output power and 90.8% power added efficiency at 6.78 MHz. The wireless power transfer (WPT) system with the amplifier shows 5.4 W transmitted power and 82.3% overall efficiency. The analysis and measurements show that high-Q inductors are required for the amplifier design to realize highly efficient WPT system.

• 한국통신학회논문지
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• 제38B권8호
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• pp.632-640
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• 2013

본 논문에서는 무선랜 환경의 보안위협에 대비해 모바일 단말 및 원격서버 기반의 무선랜 보안 시스템을 제안 한다. 최근 무선랜 환경에서의 보안기술은 다양한 방식으로 제안되고 있으며, WIPS, DLP등 많은 제품들이 출시되고 있다. 하지만 이러한 제품들은 가격이 비싸고, 관리가 힘들다는 점에서 소규모 기업에서는 사용하기가 힘든 실정이다. 따라서 본 논문에서는 BYOD 시장의 발달과 스마트폰 하드웨어의 발전에 맞춰 whitelist를 이용한 단말 및 원격서버 기반의 무선랜 보안 시스템을 제안한다. 제안하는 시스템은 관리자에 의해 AP 및 개인 device에 대한 정보가 서버에 저장되고, 개인의 device에 Application설치만으로도 다양한 무선 네트워크 환경에 적용할 수 있는 장점이 있다.

• Journal of information and communication convergence engineering
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• 제9권5호
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• pp.562-566
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• 2011

As telecommunication technologies in telemedicine services are developed, the expeditious development of wireless and mobile networks has stimulated wide applications of mobile electronic healthcare systems. However, security is an essential system requirement since many patients have privacy concerns when it comes to releasing their personal information over the open wireless channels. Due to the invisible feature of mobile signals, hackers have easier access to hospital networks than wired network systems. This may result in several security incidents unless security protocols are well prepared. In this paper, we analyzed authentication and authorization procedures for healthcare system architecture to apply secure M-health systems in the hospital environment. From the analyses, we estimate optimal requirements as a countermeasure to its vulnerabilities.

• ETRI Journal
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• 제34권4호
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• pp.553-563
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• 2012

Serial peripheral interface (SPI) has been identified as a bottleneck in many wireless sensing systems today. SPI is used almost universally as the physical connection between the microcontroller unit (MCU) and radios, storage devices, and many types of sensors. Virtually all wireless sensor nodes today perform up to twice as many bus transactions as necessary to transfer a given piece of data, as an MCU must serve as the bus master in all transactions. To eliminate this bottleneck, we propose the master-handoff protocol. After the MCU initiates reading from the source slave device and writing to the sink slave device, the MCU as a master becomes a slave, and either the source or the sink slave becomes the temporary master. Experiment results show that this master-handoff technique not only cuts the data transfer time in half, but, more importantly, also enables a superlinear energy reduction.

• International journal of advanced smart convergence
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• 제7권3호
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• pp.101-109
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• 2018

In this paper, we propose an adaptive filtering scheme of connection requests for the defense of malicious energy consumption attacks against wireless computing devices with limited energy budget. The energy consumption attack tries to consume the battery energy of a wireless device with repeated connection requests and shut down the wireless device by exhausting its energy budget. The proposed scheme blocks a connection request of the energy consumption attack in the middle, if the same connection request is repeated and its request result is failed continuously. In order to avoid the blocking of innocuous mistakes of normal users, the scheme gives another chance to allow connection request after a fixed blocking time. The scheme changes the blocking time adaptively by comparing the message arriving ate during non-blocking period and that during blocking period. Evaluation shows that the proposed defense scheme saves up to 94% energy consumption compared to the non-defense case.

• 한국산학기술학회논문지
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• 제9권6호
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• pp.1653-1658
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• 2008

본 논문에서는 GPS 수신기가 제공되지 않는 환경에서 무선 AP 위치 추적을 위한 방안을 마련하기 위해 AP 장비로부터 방사되는 무방향성 전파의 특성을 분석하였다. 무선 단말로부터 추적되는 AP장비나 고정된 AP 장비로 추적 가능한 무선 단말의 위치를 추적하기 위해서는 거리에 따른 수신 전력의 분포 환경을 분석하는 것이 무엇보다 중요하다. 따라서 본 논문에서는 2.4GHz 대역의 무선 전파 특성을 실내 및 실외 환경에서 거리에 따라 영향정도 및 특성을 분석하고 이를 위치 예측에 활용하였다.

• 한국정보통신학회논문지
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• 제16권7호
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• pp.1533-1540
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• 2012

u-라이프 케어 단말기는 생체 정보를 수집하고, 운동을 패턴 별로 분류, 저장하고 일정 시간마다 안드로이드 폰에 블루투스 무선통신을 통해 전송한다. 전송된 정보는 안드로이드 폰 어플리케이션을 통해 확인할 수 있다. u-라이프 케어 단말기는 3축 가속도 센서를 이용하여 활동량을 모니터링한 후 소모한 칼로리를 계산한다. 생체 데이터 마이닝을 통해 건강상태를 판단하고 적절한 맞춤형 운동치료를 컨설팅하게 된다. 생체 정보를 전송할 때 블루투스 무선통신을 통해 안드로이드 폰에 바로 전송하기 때문에 기존의 라이프케어 제품들에서 센싱된 정보를 웹서버에 전송하기 위해 사용되어지는 모바일 게이트웨이나 홈 게이트웨이가 별도로 필요치 않다는 장점을 가지고 있다.