• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.243-252
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• 2008

In this paper, we propose the next-generation broadband wireless access network architecture, which is based on the wavelength division multiplexing-passive optical network(WDM-PON), and efficient mobility management scheme to support quality-of-service(QoS) of multimedia services in the next-generation wireless network. By adapting WDM-PON technology to wireless access network, the proposed scheme can realize broadband wireless access network. In addition, We utilize newly proposed local channels between optical network units(ONUs) or subnets in order to support the fast and efficient local data and handoff data transmission. We evaluate the performance of the proposed scheme in terms of handoff delay and packet loss thru computer simulation. Thru various computer simulation results, we verified the superior performance of the proposed scheme by comparing with the results of other schemes.

• Journal of the Institute of Convergence Signal Processing
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• v.16 no.4
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• pp.122-128
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• 2015

As multimedia information is spread over cyber networks, problems such as protection of legal rights and original proof of an information owner raise recently. Various image transformations of DCT, DFT and DWT have been used to embed a watermark as a token of ownership. Recently, SVD being used in the field of numerical analysis is additionally applied to the watermarking methods. A watermarking method is proposed in this paper using Gabor cosine and sine transform as well as SVD for embedding and extraction of watermarks for digital images. After delivering attacks such as noise addition, space transformation, filtering and compression on watermarked images, watermark extraction algorithm is performed using the proposed GCST-SVD method. Normalized correlation values are calculated to measure the similarity between embedded watermark and extracted one as the index of watermark performance. Also visual inspection for the extracted watermark images has been done. Watermark images are inserted into the lowest vertical ac frequency band. From the experimental results, the proposed watermarking method using the singular vectors of SVD shows large correlation values of 0.9 or more and visual features of an embedded watermark for various attacks.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.430-436
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• 2006

Polarization-independent $Ti:LiNbO_3\;2{\times}2$ optical add/drop multiplexer for the 1550nm wavelength region is fabricated. The device consists of two input waveguides, two polarization beam splitters. two polarization conversion/electrooptic tuning waveguide sections, and two output waveguides. The single mode channel waveguides for both TE and TM polarizations are fabricated on a x-cut $Ti:LiNbO_3$substrate by Ti diffusion. Spectral section is based on phase-matched polarization conversion due to shear strain induced by a thick $SiO_2$ grating overlay film. An applied voltage tunes the device by changing the waveguide birefringence, hence the optical wavelength at which most efficient polarization conversion occurs. Tuning rate of 0.094nm/V with a maximum range of 17nm has been obtained. The nearest side-lobe is about 8.2dB. The FWHM is 3.72nm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.55-57
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• 2022

In this study, a customized semi-passive RFID receiver module was implemented for in-VIVO deep tissue photo-therapy. A novel wireless technique is required due to a limitation of RF communication in body environment, as internal body has a complex structure such as, skin, fat, skeleton, water, and so on. Recently, coherently incoherent beamforming (CIB) based on RFID was introduced and it is able to transmit wireless signal with high reliability under the incoherent condition such as in-VIVO deep tissue. The proposed miniature photo capsule based on RFID consists of miniature controller, ultra small LED array and wireless RFID chip. RF Reader can access with standard RFID protocol (ISO 18000-6c) using UHF RFID antenna, a control command is wirelessly writtern on USER Bank memory. With received control command, therapy LED array dims with mulilevel under timer control. The signal process of designed RFID photo therapy capsule is analyzed and evaluated under the various environments in detailed.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.111-118
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• 2009

Against Anomaly of GPS, there are several projects of independent satellite navigation systems like Galileo of Europe and QZSS of Japan and modernization of terrestrial navigation system like Loran. In domestic, the need of independent navigation system was proposed and DGPS signal was nominated as the possible substitute. The DGPS signal uses medium frequency, which travels through the surface and cause the additional delay rather than the speed of light according to Conductivities and elevations of the irregular terrain. The similar approach is Locan-C. Loran-C has been widely used as the maritime location system. Loran-C uses the ASF estimation method and provides more precise positioning. However there was rarely research on this area in Korea Therefore, we introduce the legacy guaranteed model of additional delay(ASF) and present the results of implementation. With the comparison of the original Monteath results and BALOR results respectively, we guarantee that the implementation is absolutely perfect. For further works, we're going to apply the ASF estimation model to Korean DGPS system with the Korean terrain data.

• The Journal of the Acoustical Society of Korea
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• v.28 no.7
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• pp.589-598
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• 2009

As mobile devices become multi-functional, and converge into a single platform, there is a strong need for a codec that is able to provide consistent quality for speech and music content MPEG-D USAC standardization activities started at the 82nd MPEG meeting with a CfP and approved WD3 at the 88th MPEG meeting. MPEG-D USAC is converged technology of AMR-WB+ and HE-AAC V2. Specifically, USAC utilizes three core codecs (AAC ACELP and TCX) for low frequency regions, SBR for high frequency regions and the MPEG Surround tool for stereo information. USAC can provide consistent sound quality for both speech and music content and can be applied to various applications such as multi-media download to mobile device Digital radio Mobile TV and audio books.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.23-32
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• 2011

Design and Implementation of Clipcast Service via Terrestrial DMB This paper outlines the system design and the implementation process of clipcast service that can send clips of video, mp3, text, images, etc. to terrestrial DMB terminals. To provide clipcast service in terrestrial DMB, a separate data channel needs to be allocated and this requires changes in the existing bandwidth allocation. Clipcast contents can be sent after midnight at around 3 to 4 AM, when terrestrial DMB viewship is low. If the video service bit rate is lowered to 352 Kbps and the TPEG service band is fully used, then 320 Kbps bit rate can be allocated to clipcast. To enable clipcast service, the terminals' DMB program must be executed, and this can be done through SMS and EPG. Clipcast service applies MOT protocol to transmit multimedia objects, and transmits twice in carousel format for stable transmission of files. Therefore, 72Mbyte data can be transmitted in one hour, which corresponds to about 20 minutes of full motion video service at 500Kbps data rate. When running the clip transmitted through terrestrial DMB data channel, information regarding the length of each clip is received through communication with the CMS(Content Management Server), then error-free files are displayed. The clips can be provided to the users as preview contents of the complete VOD contents. In order to use the complete content, the user needs to access the URL allocated for that specific content and download the content by completing a billing process. This paper suggests the design and implementation of terrestrial DMB system to provide clipcast service, which enables file download services as provided in MediaFLO, DVB-H, and the other mobile broadcasting systems. Unlike the other mobile broadcasting systems, the proposed system applies more reliable SMS method to activate the DMB terminals for highly stable clipcast service. This allows hybrid, i.e, both SMS and EPG activations of terminals for clipcast services.

• Journal of the Korean Professional Engineers Association
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• v.29 no.2
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• pp.15-23
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• 1996

With the ever-increasing importance of high-speed information in society as we move towards the 21 st century, telecommunication laboratories of advanced nations are pressing forward with research and development aimed at implementing its W & P(Visual Intelligent and Personal) services and construction of a new network to support them. In legals to the former, based on a long-term view of technological and market trends, those laboratories are researching and developing services that will make possible an effective progression from the development of services that answer to potential needs towards the full-scale implementation of VI & P services. In regards to the latter, these laboratories are responding in a flexible manner to the increasing diversity and disposal of the communications environment by separating the network into a transmission system and a versatile information control/conversion -ion system and laboratories are working at enhancing the performance of both. Within these board aims, the laboratories are currently focusing our attention in three areas : the technology for a high-speed broadband transmission system featuring optical frequency multiplexing and ATM techniques, network and software technologies for advanced information control and conversion, and technology for constructing a new access network that can provide a comprehensive range of multimedia services. This article describes the laboratories' concept of how VI & P services will develop in the future, and the latest trends in the field of communications. It also describes the ideal configuration of the new network and discusses the important technological aspects of how it is to be constructed. Finally, it presents the results of the laboratories'recent research which include some innovative work, point out the areas requiring future investigation.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.181-189
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• 2011

According to developments of digital signal processing, 3D sound come into focus on multimedia systems. Many studies on 3d sound have proposed lots of clues to create realistic sounds. But these clues are only focused on binaural systems which two ears are normal. If we make the 3d sound using those clues at monaural systems, the performance goes down dramatically. In order to use the clues for monaural systems, we have studies algorithms such as duplex theory. In duplex theory, the sounds that we listen are affected by human's body, pinna and shoulder. So, we can enhance sound localization performances using its characteristics. In this paper, we propose a new method to use psychoacoustic theory that creates realistic 3D audio at monaural systems. To improve 3d sound, we calculate the excitation energy rates of each symmetric HRTF and extract the weights in each bark range. Finally, they are applied to emphasize the characteristics related to each direction. Informal listening tests show that the proposed method improves sound localization performances much better than the conventional methods.

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.80-85
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• 2017

In this paper, a mircrowave breakdown of X-band circular waveguide cavity filter, which occurred during ground test, was introduced, and electro-magnetic field simulation results to identify a root cause, and the analysis of possibility of its occurrence on orbit operation were presented. Filter modeling for simulation was conducted with a commercial tool (FEST3D), and electric fields inside the filter were monitored at the input of 1 W continuous wave. In our observation, strong electric field intensities were monitored on the tuning screws especially at the input of band-edge frequencies. The threshold power levels for the breakdown were also estimated and compared with the input power levels actually injected to the filter. From this estimation, we could figure out that the power exceeding the breakdown threshold was injected to the filter so that strong electric fields were generated and temperature increased high, and this became a root cause of the electrical short. Our further analysis showed that this kind of microwave breakdown is not likely to occur on orbit operation, and multipactor is expected not to occur at the input of band-edge frequencies. As a measure to prevent the microwave breakdown, we suggested to avoid the injection of band-edge frequencies and inject lower power levels to the filter.