• Journal of Satellite, Information and Communications
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• v.4 no.2
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• pp.34-38
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• 2009

This paper is related with optimum burst structure design for high efficient TDMA satellite return link transmission. In general, some typical burst structure for data transmission is composed of a pair of preamble and traffic data in the DVB-RCS (Digital Video Broadcasting. Return Channel via Satellite) and IPOS (IP over Satellite) standard. This structure has some difficulties to increase spectral efficiency that it requires a large of preamble length, high SNR environment, or receiver complexity. To cope with them, burst structure with distributed pilot symbol can be used to alleviate the residual frequency offset effect by calculating accurate frequency offset than conventional one. In particular, we investigate some relevant to proposed distributed pilot structure, previously and analyze their strong points/drawbacks in terms of synchronization to draw the most appropriate one.

• Journal of Satellite, Information and Communications
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• v.4 no.2
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• pp.39-45
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• 2009

This paper proposes the specific code synchronization technique for DS-SS(Direct Sequence-Spread Spectrum transmission in the DVB-RCS +M standard. DS-SS is better than multi-carrier transmission method under nonlinear channel but imposes a long acquisition time. To improve the synchronization aspect, the robust correlation structure is introduced for acquisition and the nonlinear delay lock loop is done for tracking. MAT(Mean Acquisition Time) performances is shown to validate its superiority. In addition, code tracking and jitter performances are done when code tracking algorithm based on 2 oversamples which is not influenced by sampling clock timing offset and carrier freq. offset is used.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.29-35
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• 2006

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2363-2369
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• 2014

The DVR system supports multiple cameras and should be able to receive images at 30 frames per channel in real time. Thus, The system is using Full-HD-grade Multiplexer and Hardware compression codec. In this paper, Describing the design and implementation for the 4-channel Full-HD-grade PC-based DVR using FPGA and GPU inside CPU without Multiplexer and Hardware codec. The existing DVR system for Full-HD-grade has drawbacks to acquire images of about only 20 frames per channel in real time. The system to acquire images of multiple channel in real time was designed using FPGA. The software for the system was implemented using Intel Media SDK. At the result of performance evaluation, It was satisfied all for the required conditions. The practicality of the system was confirmed as implementation the system without using hardware compression.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.662-672
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• 2011

This paper presents a new edge-preserving algorithm and its VLSI architecture for block artifact reduction. Unlike previous approaches using block classification, our algorithm utilizes pixel classification to categorize each pixel into one of two classes, namely smooth region and edge region, which are described by the edge-preserving maps. Based on these maps, a two-step adaptive filter which includes offset filtering and edge-preserving filtering is used to remove block artifacts. A pipelined VLSI architecture of the proposed deblocking algorithm for HD video processing is also presented in this paper. A memory-reduced architecture for a block buffer is used to optimize memory usage. The architecture of the proposed deblocking filter is prototyped on FPGA Cyclone II, and then we estimated performance when the filter is synthesized on ANAM 0.25 ${\mu}m$ CMOS cell library using Synopsys Design Compiler. Our experimental results show that our proposed algorithm effectively reduces block artifacts while preserving the details.

• Journal of IKEEE
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• v.16 no.1
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• pp.7-14
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• 2012

In this paper, a reception rate of terrestrial digital TV broadcasting service is analyzed and a novel method which can estimate the broadcasting coverage rate more objectively and reliably than the existing method is proposed. Previous method measures the reception rate by means of electric field intensity measurement or subjective video quality assessment. Because of limited measuring points, it inherently has measurement error and cannot consider the viewer's receiving conditions in real-time. In order to consider the viewer's population and receiving environment, morphology which characterizes the viewer's receiving environment is extracted using household census data of National Statistical Office and the land cover map of Ministry of Environment. Using the extracted geographical morphology, the reception rate of terrestrial digital TV broadcasting service is calculated with Spectrum Management Intelligence System (SMIs). Proposed method can calculate the reception rate more objectively and reliably than the existing methods because it fully considers the viewer's receiving environments in real-time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.19-27
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• 2011

WiBro is a wireless mobile communication system which supports a high data rate and high mobility in anywhere and anytime. Although WiBro system provides multimedia service including data, audio and video services, customers require better service quality in WiBro system. But, many researches have theoretically evaluated the performance of WiBro system without systematic studies by simulation. Therefore, in this paper, we evaluate a performance of WiBro system using OPNET simulator. We analyze system performance according to various modulation and coding schemes, and propose Adaptive Modulation and Coding (AMC) profile to support quality of services for user requirements. Also we evaluate the performance of WiBro system using AMC and Hybrid-Automatic Repeat Request (H-ARQ) technologies, and confirm that the proposed AMC profile can be applied to WiBro system with high performance.

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.8-14
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• 2017

In 4G mobile communication, data services of mobile communication began to be provided in earnest. As a result, services such as the internet and multimedia including the video have become the main contents in the recent wireless traffic. Accordingly, research on 5G mobile communication with higher transmission rate has been actively carried out. 5G mobile communication is expected to be based on 4G for compatibility with existing terminals. Therefore, the simulation of this paper is based on 4G and we propose a new user scheduling scheme based on the Max throughput scheduling algorithm to improve system performance. This paper derives the frequency efficiency and fairness to compare the existing user scheduling algorithm with the proposed user scheduling algorithm. The proposed scheme shows better frequency efficiency and fairness than Max throughput in all situations. This paper contributes to the research for improving the system performance of 5G mobile communication technology, and I hope that it will help some of the ongoing standardization work.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.604-610
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• 2009

This paper propose a digital watermarking method for digital contents which satisfies both the invisibility and the robustness to attacks to prohibit counterfeiting, modification, illegal usage and illegal re-production of video contents. This watermarking algorithm insert a watermark(digital hologram) by generated using Fresnel transform which improve the robustness. The inserting positions of the watermark choose by considering the frequency property of an image and a watermark. Also the amount of watermarking for watermark bit decide by considering the level of 2DDWT. This algorithm was implemented by C++ and experimented for invisibility and robustness with optical system. The experiment results showed that the method satisfied enough the invisibility of the inserted watermark and robustness against attacks. For the general attacks, the error rate of the extracted watermark was less than 15%, which is enough in robustness against the attacks.

• Communications of Mathematical Education
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• v.21 no.2 s.30
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• pp.153-176
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• 2007

The purpose of this paper is to analyze teaching-learning program which can be applied to mathematically gifted students in primary school, Our program is based on constructivist views on teaching and learning of mathematics. Mainly, we study the algorithmic thinking of mathematically gifted students in primary school in connection with the network problems; Eulerian graph problem, the minimum connector problem, and the shortest path problem, The above 3-subjects are not familiar with primary school mathematics, so that we adapt teaching-learning model based on the social constructivism. To achieve the purpose of this study, seventeen students in primary school participated in the study, and video type(observation) and student's mathematical note were used for collecting data while the students studied. The results of our study were summarized as follows: First, network problems based on teaching-learning model of constructivist views help students learn the algorithmic thinking. Second, the teaching-learning model based on constructivist views gives an opportunity of various mathematical thinking experience. Finally, the teaching-learning model based on constructivist views needs more the ability of teacher's research and the time of teaching for students than an ordinary teaching-learning model.