• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1068-1075
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• 2006

Frequency resource value is growing bigger more with the development of the wireless communication. But Frequency shortage phenomenon is risen seriously because the need of Frequency resource is very many compared with the supply in an information society of the future. So we need Cognitive technique Radio which is taking the attention recently to use Frequency resource not to be not using efficiently. We propose efficient Dynamic Spectrum Allocation method in IEEE a 802.22 WRAN environment of CR foundation in this paper. To share spectrum more efficiently, we presented some Dynamic Spectrum Allocation technique to apply the Variable bandwidth, Mobility and verified this through the result of the simulations.

• The Journal of the Korea Contents Association
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• v.8 no.8
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• pp.28-36
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• 2008

The worth of frequency resources is growing up because of development of wireless communication. However, frequency resources is short, because demand is much more than supply. So it needs Cognitive Radio(CR), which manages frequency resources efficiently. In this paper, we apply the efficient Spectrum Sensing method based on CR in an embedded board. We examine various Spectrum Sensing methods and apply these methods to an embedded platform on CR environment and verify the performance through the MAC message.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.52-57
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• 2015

In this paper, we studies on the RF characteristics of the transmission line employing IPACD (inverted periodically arrayed capacitive devices) on MMIC (monolithic microwave integrated circuit) for application to wireless communication system. According to measured results, the novel transmission line employing IPACD showed a wavelength much shorter than conventional transmission lines. In addition, the IPACD structure showed an effective permittivity much higher than conventional ones. We also extracted the bandwidth characteristic of the IPACD structure using equivalent circuit analysis. According to the results, the cut-off frequency of the proposed structure was 129.2 GHz.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.75-80
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• 2011

In the cooperative communication, The relay that transmit signal to destination can achieve diversity gain. But transmitter and relay must have own frequency to transmit signal to destination. If Relay is secondary user and does not have own frequency, relay can't transmit signal to destination. So, To analysis performance of cognitive radio We need to consider detection probability of secondary user. In the paper we propose cooperative communication system considering detection probability. And to compare proposed system and conventional, we also simulate incremental cooperative communication. Through the simulation result, we can know that BER performance of proposed scheme is better than incremental relaying in the cognitive radio.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.401-401
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• 2004

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.478-483
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• 2002

Presently metro in our county has higher rate of passengers as a public transportation of urban area than other transportations. And road is under very restrictive condition to be expanded in many aspects because the streets are completely choked. Therefore increase of capacity in metro and reduction of headway has been seriously required and utmost efforts has been taken by related fields to meet the requirements. The concept of CBTC system came out from this background. CBTC system can be implemented to detect the train location without using the track circuits. It has many advantages in aspects of signalling equipments build-up and maintenance. This study investigated examples of radio communication system and applicable standard norms in other countries. And it also reviewed the suggestion for the establishment of radio frequency and radio network to be considered for application train control system by radio under Korean metro environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.222-225
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• 2001

This paper describes design and performance test of dual-mode horn antenna for HAPS (High Altitude Platform Station) in 47.2 - 47.5 GHz and 47.9 - 48.2 GHz bands. To obtain the optimal geometry parameters of it. the conical section is represented by a stepped transition composed of a set of cylindrical waveguide sections. For each step. the corresponding generalized scattering matrix is calculated. The elements of the matrices at the open end of the horn, are calculated by the rigorous formulas of the factorization method. To verify the theoretical results, a horn breadboard was manufactured for the medium frequency of 47.7 GHz and its radiation beam patterns were measured. The calculated and theoretical results are in good agreement.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.939-944
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• 2014

Traffic accidents caused by the attention dispersion are increasing and the behavior of the attention dispersion affects the front-observing rate, road keeping ability, and reaction time for a dangerous situation. Many drivers listen to a radio broadcast and they have to change the frequency for continuously listening a radio broadcast of the specific broadcasting station in case of crossing a boundary of the particular area. In this situation, the possibility of a car accident increases, because the attention dispersion of a driver might be occurred. Especially, the risk of a car accident caused by changing the frequency of a radio is more serious in the highway, due to the high speed of a vehicle. In order to reduce the risk of a car accident caused by handling a radio during driving car, in this paper, we propose an automatic frequency conversion algorithm for vehicle radio, which saves normal system frequencies of primary broadcasting stations in a database and determines new frequency of the changed area using the location information obtained from a navigation system in a boundary of the specific area. After determining new frequency, the proposed algorithm selects a frequency with better receiving rate comparing signal-to-noise ratios (SNRs) of two signals corresponding previous and new frequencies.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.583-584
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• 2022

Due to the development of drones, drone missions are performed in various fields, and BVLOS (Beyond Visual Line Of Sight) flight is performed in a wide area. Most drones operate through radio frequency (RF) communication and can only fly in a limited radius of about 1-2 km. To overcome this, in this paper, we propose a multi-communication protocol-based drone control system to control drones performing missions in BVLOS using RF and LTE (Long Term Evolution). The proposed system consists of a control unit and a drone unit. The control unit transmits one control signal generated from the remote controller through RF and LTE. The drone unit classifies the control signal transmitted through RF and LTE according to the priority of the communication protocol and delivers it to the FC (Flight Controller). Through the proposed control system, it is possible to overcome the RF communication distance limit and prevent the communication disconnection situation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.159-160
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• 2010

In this paper, we compared the absorption abilities of AMP and Sendust EM wave absorbers for a port logistics RFID system. Firstly, we fabricated EM wave absorber samples by using each absorbing material, AMP or Sendust, and CPE (Chlorinated Polyethylene) with composition ratios 85 : 15 wt. %. Secondly, we designed the optimum EM wave absorber using the calculated material constants found from the measured input impedance of the samples. Therefore, we confirmed that imaginary factor of complex relative permeability influences absorption ability and that AMP is better absorbing material than Sendust at the frequency band of 433 MHz.