• ETRI Journal
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• v.36 no.3
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• pp.460-468
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• 2014

This paper addresses the problem of joint time of arrival (TOA) and direction of arrival (DOA) estimation in impulse radio ultra-wideband systems with a two-antenna receiver and links the joint estimation of TOA and DOA to the sparse representation framework. Exploiting this link, an orthogonal matching pursuit algorithm is used for TOA estimation in the two antennas, and then the DOA parameters are estimated via the difference in the TOAs between the two antennas. The proposed algorithm can work well with a single measurement vector and can pair TOA and DOA parameters. Furthermore, it has better parameter-estimation performance than traditional propagator methods, such as, estimation of signal parameters via rotational invariance techniques algorithms matrix pencil algorithms, and other new joint-estimation schemes, with one single snapshot. The simulation results verify the usefulness of the proposed algorithm.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.59-63
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• 2007

본 논문은 지연 다이버시티를 이용한 초광대역무선통신시스템의 PN 부호 포착 성능을 분석하였다. 무선채널은 주파수 선택적인 로그노말 페이딩 채널로 모델링하였다. 포착 성능은 PN 부호의 불확실한 부분에서 여러 개의 동기 상태가 존재한다는 가정하에서 검파 확률과 평균 포착 시간의 관점에서 분석되었다. 시뮬레이션 결과로부터 지연 다이버시티를 이용한 포착 시스템이 낮은 수신기의 단가와 복잡도에도 불구하고 다이버시티 이득을 획득할 수 있다는 것이 증명되었다. 본 논문의 결과는 CDMA에 기초한 초광대역무선통신시스템의 동기단을 디자인하는데 적용될 수 있다.

• Journal of Korea Multimedia Society
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• v.15 no.10
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• pp.1228-1235
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• 2012

In this Paper, we propose an energy efficient localization technique based on WUSB (Wireless USB) over WBAN (Wireless Body Area Networks) protocol required for Wearable Computer systems. For this purpose, the proposed localization algorithm minimizes power consumption and estimates location without range information. It is executed independently on the basis of WUSB over WBAN protocol at each sensor node comprising peripherals of a wearable computer system. And it minimizes power consumption by estimating locations of sensor nodes with range-free method fast.

• Journal of Korea Multimedia Society
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• v.15 no.7
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• pp.879-884
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• 2012

In this Paper, we propose an Energy Efficient Time Synchronization technique based on WUSB (Wireless USB) over WBAN (Wireless Body Area Networks) protocol required for Wearable Computer systems. For this purpose, the proposed Time Synchronization algorithm minimizes power consumption and estimates time information with accuracy. It is executed on the basis of WUSB over WBAN protocol at each sensor node comprising peripherals of a wearable computer system. It minimizes power consumption by exchanging time stamp packets and forming a hierarchical structure.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.942-945
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• 2007

유비쿼터스 환경에서 여러 종류의 센서들은 우리에게 많은 이점들을 주며 우리 생활에 보다 친숙한 생활 형태로 발달하고 있다. 이러한 센서노드들의 활용범위는 너무 범위가 넓기 때문에 지금 까지도 여러분야가 계발 중에 있다. 이러한 분야들 중 자동화 관리 시스템 분야는 대부분이 공업과 관련된 분야의 연구가 활발히 진행되어 왔다. 그 주류로서의 분야는 대부분 제조 공정의 자동화가 대부분을 차지하고 있었으며 일부분의 타 관리 시스템이 존재 하는 형태로 진행되어 왔다. 이러한 동향은 최근들어 유비쿼터스에 관한 많은 관심속에 우리와 밀접한 관련이 있는 실생활에 점점 도입되고 있다. 하지만 1차산업과 관련한 자동화 관리 시스템의 개발은 아직도 미비한 수준에 있으며, 이 또한 외국에서 개발된 상품을 수입하여 적용시키는 단계에 머물러 있는 것이 현재의 1차 산업의 관리 시스템의 실정이다. 이에 본 논문에서는 우리의 1차 산업과 관련된 분야에 적용 가능한 센서를 이용한 관리 시스템을 설계하고 이를 평가하고자 관리 시스템을 설계하였으며, 이에 따른 효용성을 평가 하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.225-227
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• 2012

무선 사운드 스피커는 서로 다른 위치에 배치되어 송신기와의 채널 환경이 서로 다르게 되어 송신기와의 거리가 상대적으로 먼 후방 스피커의 경우 사람이나 구조물에 의해 채널 환경이 열악하게 되어 전방 스피커에 비해 데이터 오류 발생 확률이 높다. 본 논문은 Multi-band orthogonal frequency division multiplexing (MB-OFDM) 기반의 무선 오디오 전송 시스템에서 무선 채널 환경이 우수한 스피커에서 무선 채널 환경이 열악한 스피커로 데이터를 전달하는 스피커 릴레이 기법을 사용할 때, packet error ratio (PER) 성능을 향상시키며 전송 시간을 감소시킬 수 있는 효율적인 스피커 릴레이 기법을 제안한다.

• Journal of Information Technology Services
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• v.9 no.3
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• pp.145-161
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• 2010

Recently, identifying user locations is becoming important as the society evolves into an ubiquitous society with the innovation of information technology. Particularly, many researches on identifying user locations are headed in direction to identify locations of users in the indoors, because a GPS that is widely used to identify the locations of users in the outdoors is inapplicable in the indoors. However, those researches are mostly not useful to general indoor environment because they are performed in a specific environment with specialized or customized devices such as UWB, RFID. Therefore, in this paper we propose a effective method to identify user locations in general indoor environments with wireless local network access points. Our approach enables to identify user location efficiently by measuring signal power of access points around the user and using the FRIIS formula which is used to calculate the distance among the things.

• Journal of Communications and Networks
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• v.14 no.5
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• pp.518-523
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• 2012

This paper presents new coherent and non-coherent detection methods for the IEEE 802.15.4a low-rate ultra-wideband physical layer with forward error correction (FEC) coding techniques. The coherent detection method involving channel estimation is based on the correlation characteristics of the preamble signal. A coherent receiver uses novel iterated selective-rake (IT-SRAKE) to detect 2-bit data in a non-line-of-sight channel. The non-coherent detection method that does not involve channel estimation employs a 2-bit data detection scheme using modified transmitted reference pulse cluster (M-TRPC) methods. To compare the two schemes, we have designed an IT-SRAKE receiver and a MTRPC receiver using an IEEE 802.15.4a physical layer. Simulation results show the performance of IT-SRAKE is better than that of the M-TRPC by 3-9 dB.

• ETRI Journal
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• v.42 no.4
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• pp.480-490
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• 2020

More than 42 000 fires occur nationwide and cause over 2500 casualties every year. There is a lack of specialized equipment, and rescue operations are conducted with a minimal number of apparatuses. Through-the-wall radars (TTWRs) can improve the rescue efficiency, particularly under limited visibility due to smoke, walls, and collapsed debris. To overcome detection challenges and maintain a small-form factor, a TTWR system-on-chip (SoC) and its architecture have been proposed. Additive reception based on coherent clocks and reconfigurability can fulfill the TTWR demands. A clock-based single-chip infrared radar transceiver with embedded control logic is implemented using a 130-nm complementary metal oxide semiconductor. Clock signals drive the radar operation. Signal-to-noise ratio enhancements are achieved using the repetitive coherent clock schemes. The hand-held prototype radar that uses the TTWR SoC operates in real time, allowing seamless data capture, processing, and display of the target information. The prototype is tested under various pseudo-disaster conditions. The test standards and methods, developed along with the system, are also presented.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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• pp.471-476
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• 2007

Various active microwave imaging techniques have been developed for cancer detection for past several decades. Both the microwave tomography and the UWB radar techniques, constituting functional microwave imaging systems, use the electrical property contrast between normal tissues and malignancies to detect the latter in an early development stage. Even though promising simulation results have been reported, the understanding of the functional microwave imaging diagnostics has been relied heavily on the complicated numerical results. We present a computationally efficient and physically instructive analytical electromagnetic wave channel models developed for functional microwave imaging system in order to detect especially the breast tumors as early as possible. The channel model covers the propagation factors that have been examined in the previous 2-D models, such as the radial spreading, path loss, partial reflection and transmission of the backscattered electromagnetic waves from the tumor cell. The effects of the system noise and the noise from the inhomogeneity of the tissue to the reconstruction algorithm are modeled as well. The characteristics of the reconstructed images of the tumor using the proposed model are compared with those from the confocal microwave imaging.