• Journal of KIISE:Computer Systems and Theory
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• v.31 no.9
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• pp.536-542
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• 2004

An architecture of direct digital frequency synthesizers (DDFS) is studied in this paper The Direct digital frequency synthesizers (DDFS) provide fast frequency switching with high spectral purity and are widely used in modern spread spectrum wireless communication systems. ROM-based DDFS uses a ROM lookup table to store the amplitude of a sine wave. In this paper, we suggest three new techniques to reduce the ROM size. One new technique uses more number of hierarchical levels in ROM structures. Another techniques use simple interpolation techniques combined with hierarchical ROM structures. A 12 bit sine wave is generated by using these techniques. Experimental results show that the new proposed techniques can reduce the required ROM size by up to 24%, when compared to that of a resent method[1].

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.319-323
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• 1999

This paper investigates the chaos secure communication with transmission line. The secure communication of chaos in two coupled canonical Chua's circuit with transmission line systems are studied.. We expected that to be available to apply this secure communication with digital communication.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.540-543
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• 2008

본 논문은 DVB-T 전송스트림의 비디오, 오디오 및 그 외의 데이터의 다중화를 고찰하고, 효율적인 역다중화에 대한 연구이다. DVB 시스템은 위성, 케이블, 지상파, 휴대용 등 모든 전송 매체에 디지털 TV 및 데이터 방송을 제공하며 전송(Transport) 시스템으로 MPEG-2 시스템을 채택하였다. MPEG-2 시스템은 여러 가지 영상과 음성, 데이터 스트림을 하나의 스트림으로 다중화하고 188byte 크기의 전송 스트림 패킷을 사용한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.528-531
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• 2008

서브타이틀 데이터는 비트맵으로 된 텍스트로 MPEG-2 전송 스트림형식으로 전송된다. 본 논문에서는 셋톱박스(SetTopBox)에 사용되는 서브타이틀 분석기를 구현하는데 필요한 표준 기술을 분석하고, 윈도우 환경에서 사용가능 한 응용프로그램을 구현하는 방법을 제안한다. 특히 DVB-T용으로 제한하여 디스플레이 크기는 표준인 $720{\times}576$이다. 실제 유럽에서 방송되던 스트림을 가지고 테스트해본 결과 성공적으로 처리함을 확인하였다.

• Journal of Information Processing Systems
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• v.15 no.2
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• pp.261-270
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• 2019

In order to protect secret digital documents against vulnerabilities while communicating, steganography algorithms are applied. It protects a digital file from unauthorized access by hiding the entire content. Pixel-value-difference being a method from spatial domain steganography utilizes the difference gap between neighbor pixels to fulfill the same. The proposed approach is a block-wise embedding process where blocks of variable size are chosen from the cover image, therefore, a stream of secret digital contents is hidden. Least significant bit (LSB) substitution method is applied as an adaptive mechanism and optimal pixel adjustment process (OPAP) is used to minimize the error rate. The proposed application succeeds to maintain good hiding capacity and better signal-to-noise ratio when compared against other existing methods. Any means of digital communication specially e-Governance applications could be highly benefited from this approach.

• International journal of advanced smart convergence
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• v.13 no.1
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• pp.69-76
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• 2024

The objective of this paper is to investigate digital transformation in logistics within the shipping and logistics industry. This paper examines the case of Hyundai Merchant Marine (HMM) and draws insights from its success in becoming the top company amidst the industry challenges. To achieve a more in-depth analysis, a single-case study approach was employed. Various secondary data have been analyzed to support the examination of HMM's digital transformation. HMM has emerged as a global leader in transportation services. The company's success is attributed to its development of diverse ships, robust logistics systems, and pioneering a digital logistics platform, ultimately overcoming the crisis. Especially, this paper show that the digitalization of logistics has been analyzed as the most significant transformation. The findings of this paper can offer valuable implications for other companies grappling with similar challenges in the current trade landscape.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12C
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• pp.983-990
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• 2008

In communication systems, initial acquisition is required for the reliable transmission performance, and the analysis of the acquisition performance over various communication environments including different signal-to-noise ratios plays an important role in communication system design. Usage of differential correlation methods in initial synchronization procedure is desired when frequency offsets exist, and additional performance improvement can be achieved through proper modifications of conventional correlation schemes. In this paper, we derive the error probability of the initial acquisition and express it in terms of the Marcum Q-function, via statistical modeling of the differential correlator output. The result is generalized to the error probabilities of the extended differential correlation methods using the complex- and magnitude-sum of the correlator outputs. The derived probabilities can be applied for the acquisition performance verification of various communication systems including the DVB-S2 standard.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6C
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• pp.498-504
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• 2008

In this paper, an efficient hardware platform for the digital signal processing for OFDM Communication systems is presented. The hardware platform consists of a single FPGA, two DSPs with 8000 MIPS of maximum at 1 GHz clock, 2-channel ADC and DAC supporting maximum 125 MHz sampling rate, and flexible data bus architecture, so that a wide variety of baseband signal processing algorithms for practical OFDM communication systems may be implemented and tested. The IEEE 802.16 software modem is also presented in order to verify the effectiveness and usefulness of the designed platform.

• Journal of the Korea Society of Computer and Information
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• v.1 no.1
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• pp.53-64
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• 1996

The methods for designing the adaptive filter performing DSP(digital signal processing)functions In mobile communication systems are Least-squares algorithm. Fast-Kalman and adaptive lattice algorithm. Least-squares algorithm It fast convergence algorithm for signal Processor of adaptive equallizer and used for eliminating inter symbol Interference which occur inmultiple path fading channel In mobille communication systems. In this paper. we propose the method of control adjustably algebra characteristics of signal vector that is sampling at some of new data sequence and confirm the improvement of fast convergence and iterative performance speed compared to existing algorithms by computer simulation.

• ETRI Journal
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• v.40 no.5
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• pp.664-676
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• 2018

Given the rapidly increasing market penetration of photovoltaic (PV) systems in many fields, including construction and housing, the effective maintenance of PV systems through remote monitoring at the panel level has attracted attention to quickly detect faults that cause reductions in yearly PV energy production, and which can reduce the whole-life cost. A key point of PV monitoring at the panel level is cost-effectiveness, as the installation of the massive PV panels that comprise PV systems is showing rapid growth in the market. This paper proposes an implementation method that involves the use of a panel-level wireless PV monitoring module (WPMM), and which assesses the cost-effectiveness of this approach. To maximize the cost-effectiveness, the designed WPMM uses a voltage-divider scheme for voltage metering and a shunt-resistor scheme for current metering. In addition, the proposed method offsets the effect of element errors by extracting calibration parameters. Furthermore, a design method is presented for portable and user-friendly PV monitoring, and demonstration results using a commercial 30-kW PV system are described.