• 전기학회논문지
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• 제63권4호
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• pp.570-574
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• 2014

This paper proposes a wireless digital endoscope with a ultra-wide-angle view. Two key components are implemented to demonstrate the feasibility of the proposed endoscope. First, a ultra-wide-angle lens module with the field of view of 144 degree and F-number of 2.2 is designed and manufactured. Second, a wireless module for a high-speed video transfer is implemented using a USB device server and wireless LAN router. The wireless module can directly transfer a streaming video to a computer with the resolution of 1920x1080, frame rate of 30 fps, and data rate of 53.3 Mbps without an internet connection. Since the wireless module supports two USB devices, two spots can be simultaneously observed using the proposed endoscope.

• 센서학회지
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• 제16권2호
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• pp.142-149
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• 2007

Wireless sensor network technology is an emerging technology consisting of small, low power, and low cost devices that integrate limited computation, sensing, and radio communication capabilities. An ad-hoc home network system based embedded system for home environment monitoring was fabricated and tested. The wireless sensor node consists of a MCU, RF transceiver and sensors (temperature, humidity and light). Wireless sensor nodes run application software for data sampling and wireless communication, that was developed using 'nesC language' which runs on TinyOS. In our tests, acquired sensors data were monitored on 6.4" TFT-LCD of base-station through IEEE802.15.4 standard wireless communication. Also, the sensor data can be monitored by client user at the terminal PC to monitor environmental status of home in real time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.800-818
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• 2013

Supporting video streaming over multi-hop wireless networks is particularly challenging due to the time-varying and error-prone characteristics of the wireless channel. In this paper, we propose a joint optimization scheme for video streaming over multi-hop wireless networks. Our coding scheme, called Joint Source/Network Coding (JSNC), combines source coding and network coding to maximize the video quality under the limited wireless resources and coding constraints. JSNC segments the streaming data into generations at the source node and exploits the intra-session coding on both the source and the intermediate nodes. The size of the generation and the level of redundancy influence the streaming performance significantly and need to be determined carefully. We formulate the problem as an optimization problem with the objective of minimizing the end-to-end distortion by jointly considering the generation size and the coding redundancy. The simulation results demonstrate that, with the appropriate generation size and coding redundancy, the JSNC scheme can achieve an optimal performance for video streaming over multi-hop wireless networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2435-2453
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• 2015

Independent component analysis (ICA) is a signal processing technique used for un-mixing of the mixed recorded signals. In wireless communication, ICA is mainly used in multiple input multiple output (MIMO) systems. Most of the existing work regarding the ICA applications in MIMO systems assumed static or quasi static wireless channels. Performance of the ICA algorithms degrades in case of time varying wireless channels and is further degraded if the data block lengths are reduced to get the quasi stationarity. In this paper, we propose an ICA based MIMO transceiver that performs well in time varying wireless channels, even for smaller data blocks. Simulation is performed over quadrature amplitude modulated (QAM) signals. Results show that the proposed transceiver system outperforms the existing MIMO system utilizing the FastICA and the OBAICA algorithms in both the transceiver systems for time varying wireless channels. Performance improvement is observed for different data blocks lengths and signal to noise ratios (SNRs).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1390-1405
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• 2014

This paper investigates optimal relay selection and power allocation under an aggregate power constraint for cooperative wireless sensor networks assisted by amplify-and-forward relay nodes. By considering both transmission power and circuit power consumptions, the received signal-to-noise ratio (SNR) at the destination node is calculated, based on which, a relay selection and power allocation scheme is developed. The core idea is to adaptively adjust the selected relays and their transmission power to maximize the received SNR according to the channel state information. The proposed scheme is derived by recasting the optimization problem into a three-layered problem-determining the number of relays to be activated, selecting the active relays, and performing power allocation among the selected relays. Monte Carlo simulation results demonstrate that the proposed scheme provides a higher received SNR and a lower bit error rate as compared to the average power allocation scheme.

• 한국융합학회논문지
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• 제4권1호
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• pp.27-31
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• 2013

최근 IT기술의 발전에 따라 언제 어디서나 이용할 수 있는 M2M기반의 무선 충전 분야의 기술 개발이 빠르게 진행되고 있다. M2M에서 무선충전기술은 무선 네트워크를 기반으로 하기 때문에 다양한 보안의 위협요소가 발생된다. 본 논문에서는 무선 충전 시 무선 네트워크 공격 기반의 인증 및 지불 공격에 대한 위협을 알아보고, 기존의 인증 및 지불을 위하여 무선충전 서비스 상황에 맞는 대응 기법을 제안한다.

• 방송과미디어
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• 제11권1호
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• pp.78-85
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• 2006

Cognitive radio is a paradigm for wireless communication in which either network of wireless node itself changes particular transmission or reception parameters to execute its tasks efficiently without interfering with the licensed users. This paper represents a performance of the cognitive radio technology on dual polarized MIMO system using six-port receiver. Six-port technology is well known direct conversion receiver. In this paper, a six-port phase discriminator based polarization signal separation is shown. That is, the SER(Symbol Error Rate) performance is improved using polarization separator and simple receiver architecture is proposed applying six-port receiver. The six-port technology has priority to adapt changeable frequency system and variable environments for cognitive radio. In general, dual polarized MIMO system has good capacity and quality using polarization separator [1].

• 산업기술연구
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• 제27권A호
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• pp.131-139
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• 2007

The recent advance in wireless network technologies has enabled the streaming media service on the mobile devices such as PDAs and cellular phones. Since the wireless network has low bandwidth channels and mobile devices are actually composed of limited hardware specifications, the transcoding technology is needed to adapt streaming media to given mobile devices. Futhermore owing to the diversity of bandwidth in the wireless network by reason of mobile users' movements and environments, it is difficult to provide stable QoS. In this paper, the autonomic multimedia transcoding system is proposed in order for users to provide network adaptive QoS. Our proposed system is based on the estimation of available bandwidth in wireless network for seamless multimedia streaming service. The proposed system is designed and implemented for various mobile clients. In experiments, we evaluate its seamless multimedia streaming and the adaptation transcoding bit rate according to the changes of bandwidth in wireless network.

• 한국정보통신학회논문지
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• 제18권7호
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• pp.1571-1578
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• 2014

Binary CDMA는 음성 영상 등의 멀티미디어 데이터를 초고속으로 우수한 전송품질로 통신할 수 있는 우리나라가 개발한 새로운 표준 무선통신 기술이다. 본 논문에서는 유선의 제약 없이 자유롭게 설치 가능한 차량용 무선 카메라 시스템의 개발을 위해 이의 핵심 장치인 Binary CDMA 무선 영상전송기와 중계기의 설계와 구현에 관해 연구하였다.

• ETRI Journal
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• 제35권4호
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• pp.578-586
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• 2013

Using a sub-terahertz (sub-THz) wave generated using a photonics-based technology, a high-speed wireless link operating at up to 10 Gbps is designed and demonstrated for realization of seamless connectivity between wireless and wired networks. The sub-THz region is focused upon because of the possibility to obtain sufficient bandwidth without interference with the allocated RF bands. To verify the high-speed wireless link, such dynamic characteristics as the eye diagrams and bit error rate (BER) are measured at up to 10 Gbps for non-return-to-zero pseudorandom binary sequence $2^{31}-1$ data. From the measurement results, a receiver sensitivity of -23.5 dBm at $BER=10^{-12}$ is observed without any error corrections when the link distance between the transmitter and receiver is 3 m. Consequently, we hope that our design and experiment results will be helpful in implementing a high-speed wireless link using a sub-THz wave.