• Proceedings of the Korea Society for Industrial Systems Conference
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• 2008.10b
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• pp.634-642
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• 2008

Radio wave is the valuable resources in $21^{st}$ century. It will be widely used in various applications such as DMB, USN, telematics, and home network as well as mobile and wireless communications. Cognitive Radio technology is devised to maximize the utilization of radio resources by sensing near-by spectrum and dynamic and allocating free resources dynamically and adaptively. Wireless links for the secondary user need to be frequently switched to idle frequencies during the transmission of multimedia data in the cognitive radio based system. This may cause delay and information loss, and QoS degradations occur inevitably. The efficient frequency allocation scheme is necessary to support the seamless multimedia service to the secondary user while maintaining QoS of the primary user. This paper suggests a frequency selection scheme which considers other parameters such as cell load, data rate, and available bandwidth than just received signal strength during the frequency selection process. The performance of our proposed scheme is analyzed by simulation.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.2030-2037
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• 2009

In this paper, the study on the allocation of dedicated radio frequency for the radio communication based CBTC system is performed. The dedicated bandwidth for the the private use in railroad is figured out and the allocatable frequency band, which should be investigated hereafter, is proposed. The result of this study provides the basis to present the requirement of dedicated railroad radio frequency and can be used as an important material for the frequency allocation. Furthermore, it is expected that the result can be contributed to the development on railroad radio communication.

• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.71-74
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• 2010

본 연구에서는 P3기반의 프로젝트 관리 모델을 제안하였다. 제안한 모델은 최근 프로젝트 추진의 범위가 신제품개발, 연구관리, 시스템개발과 경영혁신을 포함하는 등 다각적으로 전개됨에 따라 다양한 프로젝트를 수용할 수 있도록 Program, Project, 그리고 Portfolio를 통한 이슈, 예산, 자원, 위기, 변경관리, 산출물 관리 등에서 신속한 의사결정을 지원할 수 있도록 구현 하였으며, 이렇게 구현된 제안 모델은 빠르게 변화 되는 프로젝트 관리에서 신속한 의사결정과 프로젝트와 연계된 사람 간의 협업을 지원하는 면에서 우수함을 보인다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.349-350
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• 2006

This paper presents very low bit rate speech coder, ZFE-CELP(ZINC Function Excitation-Code Excited Linear Prediction). The ZFE-CELP speech codec is based on a ZINC function and CELP modeling of the excitation signal respectively according to the frame characteristic such as a voiced speech and an unvoiced speech. And this paper suggest strategies to improve the speech quality of the very low bit rate speech coder.

• 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.

• Journal of electromagnetic engineering and science
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• v.4 no.2
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• pp.51-55
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• 2004

With the progress of the electronics industry and radio communication technology, certain problems, such as electromagnetic interference(EMI), have arisen due to the increased use of electromagnetic(EM) waves. International organizations such as CISPR, FCC, and ANSI have provided the standards for the EM wave environment and for the countermeasure of the electromagnetic compatibility(EMC). EM wave absorbers are used for constructing an anechoic chamber to test and measure EMI and electromagnetic susceptibility(EMS). In this paper, we have designed an one-body EM(electromagnetic) wave ferrite absorber, based on the equivalent material constants method for both normally and obliquely incident waves, whose absorption abilities are superior to that of the conventional ones. The fabricated absorber has a thickness of 27.68 mm and shows an absorption ability over 20 ㏈ in the frequency from 30 MHz to 6 ㎓.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.230-233
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• 2004

CAMAC, PLC, DAQ나 GPIB와 같은 여러 인스트루먼트 인터페이스의 통합은 산업전반에 걸쳐서 널리 활용되고 있으며 이를 통하여 작업 효율 및 성능을 향상시킬 수 있다. 이를 지원하는 기술에는 여러 가지가 있지만 그 중에서 Virtual Instrumentation이 개발의 신속성 및 사용의 용이성 측면에서 타 기술을 압도하고 있는 추세이다. Virtual Instrumentation을 통한 시스템 통합에 있어서 현재 적용되고 있는 새로운 기술로서 XML을 들 수 있는데 이는 사용자와 인스트루먼트간의 통신뿐만 아니라 해당 정보 공유에 있어서 탁월한 기능을 제공한다. 본 논문에서는 이를 위하여 Virtual Instrumentation 시스템 설계에 있어서 XML 기술을 적용하고자 하면 이를 통하여 한층 진보된 시스템 설계를 제안하고자 한다.

• Journal of Information Processing Systems
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• v.10 no.1
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• pp.119-131
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• 2014

In recent literature on traffic scheduling, the combination of the two-dimensional discrete-time Markov chain (DTMC) and the Markov modulated Poisson process (MMPP) is used to analyze the capacity of VoIP traffic in the cognitive radio system. The performance of the cognitive radio system solely depends on the accuracy of spectrum sensing techniques, the minimization of false alarms, and the scheduling of traffic channels. In this paper, we only emphasize the scheduling of traffic channels (i.e., traffic handling techniques for the primary user [PU] and the secondary user [SU]). We consider the following three different traffic models: the cross-layer analytical model, M/G/1(m) traffic, and the IEEE 802.16e/m scheduling approach to evaluate the performance of the VoIP services of the cognitive radio system from the context of blocking probability and throughput.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.856-859
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• 2021

Image transmission by means of telecommunications is an essential task for information sharing. For considerable distances, wireless channels can be utilized and tuned for proper uses of image data exchange. However, the disturbances that a radio wave encounter during transmission causes partial or total loss of information. Result of such communications is a distorted image at the receiver's end. This paper proposes an auto-encoder architecture as an image enhancement method for narrow-bandwidth radio images. With this method, a distorted image can be improved for better receiver satisfaction. The proposed auto-encoder is trained with many narrow-bandwidth radio image data; hence it enhances a given distorted image. Also, the results were verified with the original image data being the reference images.

• Journal of electromagnetic engineering and science
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• v.18 no.1
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• pp.58-62
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• 2018

In this study, we propose a software-defined radio-based frequency interference emulator in the space-time domain. This emulator can easily model actual interference environments because of the versatile programming capability of the universal software radio peripheral and LabVIEW. As an example of an interfering network using the contention-based multiple access scheme in the time domain, we emulate a coordinated Wi-Fi network that consists of one access point and two Wi-Fi nodes. Results show that our emulator can successfully model multiple interfering signals in the Wi-Fi network and easily adjust various space-time domain parameters.