• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.243-246
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• 2019

In cognitive radio networks, secondary transmitters should cease its transmission immediately under the detection of primary transmission in the spectrum they are using. Then they need to exploit another idle spectrums and resynchronize to the newly found idle spectrums. Most of related work presume the existence of separate control channel used by secondary users commonly for exchanging the information of idle spectrums. However, this presumption is not feasible in real world cognitive radio scenario. Therefore we address a proactive spectrum synchronization scheme with no need of separate control channel. Our scheme lets secondary users exchange the spectrum information periodically during normal communication process and determine the next spectrum band in advance of detecting primary transmission. We evaluate our scheme in a real world cognitive radio environments set up with USRPs.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1075-1080
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• 2021

In this paper, we designed a 24.4GHz 2-channel TX and 4-channel RX patch array antenna mounted on a short-range vehicle radar system to simultaneously measure the range and speed of a single object within a single measurement cycle. The antenna was designed and fabricated using Rogers' RO4350B(ε_r=3.48, 0.5T) board. Through measurement, it was confirmed that the design specifications of antenna gain (> 10dBi or more) and radiation pattern (Elevation HPBW > 10deg.) were satisfied at 24.4 GHz frequency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1250-1264
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• 2017

This paper presents the architecture design, implement, experimental validation of a bistatic backscatter wireless communication system in Wi-Fi network. The operating principle is to communicate a tag's data by detecting the power level of the power modulated Wi-Fi packets to be reflected or absorbed by backscatter tag, in interconnecting with Wi-Fi device and Wi-Fi AP. This system is able to provide the identification and sensor data of tag on the internet connectivity without requiring extra device for reading data, because this uses an existing Wi-Fi AP infrastructure. The backscatter tag consists of Wi-Fi energy harvesting part and a backscatter transmitter/a power-detecting receiver part. This tag can operate by harvesting and generating energy from Wi-Fi signal power. Wi-Fi device decodes information of the tag data by recognizing the power level of the backscattered Wi-Fi packets. Wi-Fi device receives the backscattered Wi-Fi packets and generates the tag's data pattern in the time-series of channel state information (CSI) values. We believe that this system can be achieved wireless connectivity for ultra- low-power IoT and wearable device.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.54-56
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• 2015

In this paper, we investigate a physical-layer network coding (PNC) in a two-way relay channel (TWRC) where two sources send and receive data with each other by help of a relay node with multiple antennas. We focus on the multiple-access phase of the TWRC in this paper. It is assumed that the source nodes do not know the wireless channel and the wireless channel independently varies in time, that is, fast fading environments. At the relay node, the channel is assumed to be perfectly known. The relay node utilizes the channel sate information and applies maximum likelihood ratio for detecting received signals. Through extensive simulations, it is shown that a bit error rate (BER) performance becomes improved as the number of antennas at the relay node increases.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1
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• pp.42-47
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• 2007

In this paper. we have studied improvement in sensitivity by increasing the frequency of SAW sensors for detecting the immobilization and hybridization of DNA. The sensor consists of twin SAW delay lines operating at 200MHz, a sensing channel and a reference channel. fabricated on $36^{\circ}$ rotated Y-cut X-propagation $LiTaO_3$ crystals. The optimum concentration of probe and target DNA was decided for the improvement of detection mechanism. and digital syringe pump system was used to reduce the human errors. The hybridization between immobilized probe DNA and target DNA on the gold-coated delay line results in mass loading on the delay line of the sensing channel. Thus, the relative frequency change was monitored in relation to the mass loading. The measurement results showed a good response of the sensor to the DNA hybridization with a maximum sensitivity level up to 0.066ng/m1/Hz.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.116-131
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• 2019

In order to obtain high-quality high-resolution marine seismic data, the survey needs to be carried out at very low-sea condition. However, the survey is often performed with a slight wave, which degrades the quality of data. In this case, it is possible to improve the quality of seismic data by detecting the exact location of the sea bottom signal and eliminating the influence of waves or swells automatically during data processing. However, if noise is included or the sea bottom signal is weakened due to sea waves, sea bottom detection errors are likely to occur. In this study, we applied a method reducing such errors by estimating the sea bottom location, setting a narrow detection range and detecting the sea bottom location within this range. The expected location of the sea bottom was calculated using previously detected sea bottom locations for each channel of multi-channel data. The expected location calculated in each channel is also compared and verified with expected locations of other channels in a shot gather. As a result of applying this method to the noisy 8-channel high-resolution air-gun seismic data acquired off Yeosu, the errors in selecting the strong noise before sea bottom or the strong subsurface reflected signal after the sea bottom signal are remarkably reduced and it is possible to produce the high-quality seismic section with the correction of ~ 2.5 m swell effect.

• Korean Journal of Remote Sensing
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• v.32 no.4
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• pp.339-351
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• 2016

For the safety of sea, it is important to monitor sea fog, one of the dangerous meteorological phenomena which cause marine accidents. To detect and monitor sea fog, Moderate Resolution Imaging Spectroradiometer (MODIS) data which is capable to provide spatial distribution of sea fog has been used. The previous automatic sea fog detection algorithms were focused on detecting sea fog using Terra/MODIS only. The improved algorithm is based on the sea fog detection algorithm by Wu and Li (2014) and it is applicable to both Terra and Aqua MODIS data. We have focused on detecting spring season sea fog events in the Yellow Sea. The algorithm includes application of cloud mask product, the Normalized Difference Snow Index (NDSI), the STandard Deviation test using infrared channel ($STD_{IR}$) with various window size, Temperature Difference Index(TDI) in the algorithm (BTCT - SST) and Normalized Water Vapor Index (NWVI). Through the calculation of the Hanssen-Kuiper Skill Score (KSS) using sea fog manual detection result, we derived more suitable threshold for each index. The adjusted threshold is expected to bring higher accuracy of sea fog detection for spring season daytime sea fog detection using MODIS in the Yellow Sea.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.3
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• pp.247-259
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• 1992

In this paper, the types of the data exchange between a cell site and a cobile phonefor the call processing on the AMPS(Advanced Mobile Phone Service) are investigated, and the circuit for processing the wideband data stream according to the data types is designed and implemented. The circuit for detecting the Busy / Idle bit which is needed for determining the channel access, the circuit for detecting the word sync and the circuit for transmitting and receiving the wideband data is designed. The 3-out-of-5 majority vote of the 5received data is performed to reduce error and an algorithm requiring a small buffer size for real time processing of voting process is proposed. The method to overcome the computational complexity and the real time constraint of the conventional BCH decoding is proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.535-544
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• 1988

In this paper, the hybrid ARQ scheme, which is incorporated the selective-repeat ARQ system with the finite receiver buffer and the single-error-correcting and double-error-detecting(63.56) cyclic Hamming code system, has been investigated. As a result of simulation, the proposed hybrid ARQ scheme shows that that throughput efficiencies are improved by one error correction, and that the reversed codewords due to retransmission are delivered to the user in order by means of detecting two errors. The hybrid ARQ scheme significantly outperforms the FEC or the ideal selective-repeat ARQ system in the respect of throughput and reliability, especially when the channel error rate is approximately in the range from $10^{-2}$~$10^{-3}$.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.3
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• pp.332-340
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• 2019

Electronic warfare systems are needed to be advantageous in the modern war. Many radar threat signals with various frequency spectrums and complicated techniques exist. For detecting the threats, a receiver with wide and narrow-band digital processing is needed. To process a wide-band searching mode, a polyphase filter bank has become the architecture of choice to efficiently detect threats. A polyphase N-path filter aligns the re-sampled time series in each path, and a discrete Fourier transform aligns phase and separates the sub-channel baseband aliases. Multiple threats and CW are detected or rejected when the signals are received in different sub-channels. And also, to process a narrow-band precision mode, a direct down converter is needed to reduce aliasing by using a decimation filter. These digital logics are designed in a FPGA. This paper shows how to design and develop a wide and narrow-band digital receiver that is capable to detect the threats.