• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.199-205
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• 2003

In this paper, CSMA/CA protocol is modified for aeronautical VHF communication through collision alleviation and the change of retransmission slot selection method in flag used transmission. When collision occurred in the contention period of CSMA/CA process, it is generally waiting for retransmission delay and it has the double size of CW(Contention Window). To solve this problem, this paper modifies the change procedure of original contention window size and reduces the state transition in collision among the whole of it. Also, in this paper we reduces the second collision probability through the station has to enter Backoff mode with increased contention window in the first collision. In the result of simulation, it is verified that it has good property in throughput and delay, So the proposed protocol is suitable for aeronautical VHF communication.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.46-53
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• 2014

In this paper, ku-band RF transceiver system is designed for the unmanned aerial vehicle(UAV) line-of-sight(LOS) datalink. The RF transceiver system is consisted of the transmitting and receiving unit, RF front-end unit, and high power amplification unit. The transmitting and receiving unit has the functions of frequency up/down converting and channel changing. The RF front-end unit has the functions of transmitting and receiving signal duplexing, antenna selection, small signal amplification, and frequency filtering excluding the receiving signal. The high power amplification unit has the functions of ku-band power amplification and transmitting power variation(High/Middle/Low/Mute). The frequency up/down converting of transmitting and receiving unit is designed by using the superheterodyne method. The RF transceiver system is designed to obtain the broadband and high linearity properties for the reliable transmission and reception of high data-rate and high speed data. Also, the channel changing function is designed to use selectively the frequency as the operation environment of UAV.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.982-992
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• 2017

In this paper, we introduce a method of selection for the optimal transmission polarization of a W-band seeker through the extraction of the one-dimensional scattering center of a ground tank target. We calculated the surface scattering and edge scattering using the shooting and bouncing ray tracing method of the CST A-solver. Based on 4-channel RCS data, using the one-dimensional RELAX algorithm, which is a kind of spectral estimation technique, scattering centers of ground targets were extracted. According to the changes in the polarization state and look angle, we compared and analyzed the scattering center results. Through simulation, we verified that the scattering center results can be applied when feature vectors are used for target recognition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.517-526
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• 2006

In order to achieve high capacity and reliable link quality in wireless communication, the significant efforts should be concentrated on mitigating interference between cells. To solve the interference problem, the newly introduced concept of a Distributed Wireless Communication System (DWCS) can provide the capability of joint control of the signals at multiple cells. This paper proposes a new concept of virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. The proposed system manages two kinds of virtual cell. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The proposed system constructs DVC by using antenna selection method. Also, for multi-user high-rate data transmission, the proposed system introduces multiple antenna technology to get a spatial and temporal diversity gam and exploits space-Time Trellis Codes known as STTC to increase a spectral efficiency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.85-92
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• 2010

In this paper, we consider the orthogonal frequency division multiplexing (OFDM) based transmission incoorperating with beam-switching and space-time coding. Specifically, we consider three configurations; (1) the beamforming technique, (2) the spatial diversity technique and (3) their combination and evaluate the performance in wireless personal area network (WPAN) environment. For the beam-forming technique, we consider the beam-switching which is performed at RF front-end with a pre-defined set of beams and for the space-time coding, we consider the Alamauti scheme with antenna selection. For the combined scheme, we divide the antennas used into two group to generate two independent beams and apply the two-antenna Alamauti scheme over the two beams. For these three configurations, performance is evaluated in terms of the SNR gain.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.61-66
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• 2020

The purpose of this study is to identify and manage the problem of components discontinuity in the future based on the implementation of information systems to solve the problem of discontinuance of militaries parts, so as to solve the problem of discontinuance of components in the operation of the weapon systems and reduce excessive expenditure due to aging of the weapon system. The purpose is to prevent the discontinuance of components in the future by up-dating the production phenomena of parts manufactures periodically. Defense industries and R&D perood can expand users convenience by supporting selection of more efficient parts in weapon systems development and information of vast components information systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.965-970
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• 2010

Because of a large number of subcarriers, the high PAPR(Peak-to-Average Power Ratio) is the major drawback of NC-OFDM system used for wireless communication system. Comb type pilot assignment is more efficient and lower computational complexity for the channel estimation than the block type pilot. However, even if the CAZAC(Constant Amplitude Zero Autocorrelation) matrix transform is used for the PAPR reduction of the data symbols, PAPR increases when the pilot is inserted in comb type with the data symbols. Therefore, in this paper, we additionally use a new SLM technique in order to lower the PAPR again even in the comb type pilot. Also, a new SLM technique suggested in this paper does not need any additional bandwidth for sending selection information for SLM. This combined method has good PAPR reduction performance and efficient data transmission.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.587-596
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• 2008

For Wireless internet service in Metropolitan area, optimum location selection for base station and cell planning are critical process in determining service coverage by accurate prediction of Wave Propagation Characteristics. Due to different kinds of characteristics in service area such as lay of land, natural feature and material, height and width of artificially made building, it has a great impact on the transmission and distance recovery of wireless network service. Therefore, these facts may cause substantial barriers in predicting & analyzing the expected level of service quality and providing it to subscribers. In this thesis, we have simulated the process to improve quality and coverage of the service by adjusting the location of Base station and the antenna angle that influence the service after the basic location of base station is selected according to the wave prediction model. Based on this simulations test, we have demonstrated the results in which subscribers would get higher quality of wireless internet service along with bigger coverage and the improved quality in the same service coverage area through optimization process of base station.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.5
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• pp.2335-2340
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• 2014

Paclitaxel is hydrophobic in nature and is recognized as a highly toxic anticancer drug, showing adverse effects in normal body sites. In this study, we developed a polymeric nano drug carrier for safe delivery of the paclitaxel to the cancer that releases the drug in a sustained manner and reduces side effects. N-isopropylacrylamide/vinyl pyrrolidone (NIPAAm/VP) nanoparticles were synthesized by radical polymerization. Physicochemical characterization of the polymeric nanoparticles was conducted using dynamic light scattering, transmission electron microscopy, scanning electron microscopy and nuclear magnetic resonance, which confirmedpolymerization of formulated nanoparticles. Drug release was assessed using a spectrophotometer and cell viability assays were carried out on the MCF-7 breast cancer and B16F0 skin cancer cell lines. NIPAAm/VP nanoparticles demonstrated a size distribution in the 65-108 nm range and surface charge measured -15.4 mV. SEM showed the nanoparticles to be spherical in shape with a slow drug release of ~70% in PBS at $38^{\circ}C$ over 96 h. Drug loaded nanoparticles were associated with increased viability of MCF-7 and B16F0 cells in comparison to free paclitaxel. Nano loaded paclitaxel shows high therapeutic efficiency by sustained release action for the longer period of time, i increasing its efficacy and biocompatibility for human cancer therapy. Therefore, paclitaxel loaded (NIPAAm/VP) nanoparticles may provide opportunities to expand delivery of the drug for clinical selection.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.2
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• pp.26-33
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• 2011

Recently, the use of buried glass fiber reinforced plastic (GRP) pipes is widespread and ever increasing trend in the industry. GRP pipes are attractive for use in harsh environments, such as for the collection and transmission of liquids which are abrasive and/or corrosive. The structural behavior of a GRP pipes buried under the ground is different from that of a rigid one made of concrete or clay, for example. A GRP pipe buried under the ground is deflected circumferentially by several percent and the stresses in the pipe are mainly compressive stresses. A GRP pipes has been introduced by a number of manufacturers for selection and used by underground pipeline designers. In all cases, the modified Spangler's equation is recommended by these manufacturers for predicting the ring deflection of these pipes under dead and live loads. In this paper, the ring deflection of buried GRP pipe is evaluated and discussed based on the result of analytical investigation.