• The Journal of the Acoustical Society of Korea
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• v.26 no.7
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• pp.366-374
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• 2007

In underwater wireless communication, needs for long distance communication using the high frequency are surpassing ones of short range communication by ultrasonic wave, and demands for transmitting and receiving various data such as voice or high resolution image data are increasing as well. In this work, we studied the effects on the real underwater communication depending on the difference of digital modulation methods. Simulation shows that only the performance of GMSK among many other PSK based modulation schemes(BPSK, QPSK, MSK, GMSK) is significant. Test condition simulates the oceanographic conditions along the 207-survey line, 15Km south of Busan and SNR is maintained 35dB or below. Simulated tests are composed of both transmitting image data($3{\times}10^5$ pixel, 4 bit per pixel) and voice communication($10^{-2}$BER, channel capacity of 1Kbps). Test results show that there are gain of about 7 seconds in transmission time in image transmission case, where channel capacity for BPSK, QPSK, and MSK and for GMSK were 65 Kbps and 45 Kbps, respectively and gain of about 8Km in distances in voice communication case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.947-955
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• 2002

In this paper, we derive an outage probability for the Erlang capacity and the link margin respectively, calculate them with the same parameters and outage probability, and then analyze a capacity and cell coverage in city, suburban, and open area. So, the Erlang capacity is more real than in a cell, and the cell coverage can be calculated with high reliability by the margin. When the $E_b/N_o$ decreases from 7 dB to 5 dB within the outage probability of 5 %, it is observed that the capacity is increased from 18 Erlang to 31 Erlang with the same margin of 2.8 dB, then the coverage is increased to 0.4 km, 1 km, and 2.5 km in city, suburban, and open area respectively. Also if the outage probability is decreased from 5 % to 2 % in case of $E_b/N_o$ of 5 dB, the result shows a very reliable link with additional increment of 0.88 dB in the margin and a high QoS (quality of service) within decrement of 0.15 km, 0.5 km, and 1.5 km for the same areas with decrement of 3 Erlang from 31 Erlang.

• Informatization Policy
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• v.27 no.3
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• pp.56-81
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• 2020

The purpose of this research is to empirically examine the effects of motivation and skill for digital devices and the Internet on the use of online services in the severely disabled people. In addition to the general effect of digital divide, particularly for the case of severely disabled people, the effects of physical and mental inconvenience of individuals were taken into account and the moderating effect was confirmed by classifying the groups that need help with online activities and those that do not. The 2018 Digital Divide Survey data of the National Information Society Agency was used for the study. As a research method, path analysis and multi-group analysis using a sequence access model to Internet use were performed. As a result, it was confirmed that even in the case of the disabled, the motivational factor affects the skill for digital device operation and Internet use, and this access skill sequentially affects the use of online services. In particular, it was found that the effect of strategic and technical skill for internet use is the most important for the use of online services for the disabled rather than the motivation or a simple operational skill for digital devices. In addition, it was found that even in the disabled group, those requiring help in using the Internet was more passive in using the online service than the rest in the group. The results of this study suggest the need for stronger capacity for physical access as well as support in building strategic and technical skills that enhance responsibilities and protect from risks in using the Internet among the people with disabilities.

• International Journal of Computer Science & Network Security
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• v.22 no.5
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• pp.335-341
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• 2022

This article is devoted to the study of the process of formation of the digital generation in a distance learning environment. With the introduction of quarantine due to the spread of COVID-19, opponents of digital technologies were forced to turn to relevant resources, while supporters identified new opportunities for the development of didactics and education in general. The irreversibility of the former educational reality became apparent and only the scale of the vision of potential change by interested and disinterested groups differed. Using a comprehensive approach, the authors consider the issues related to the direct and indirect impact of distance learning on children and young people born after the beginning of the XXI century. The article reveals the prerequisites and implications of distance education for the interaction of participants in the educational process. IC technologies during the educational process in the primary grades, in addition to identifying the student's learning deficit, should provide the transmission of non-verbal signals, which are important for children of this age. At the same time in the secondary school IR-technologies are designed to replace frontal learning during the assimilation of knowledge and at the same time not to worsen the quality of the educational process. Formation of students in the HEI takes place in the political science format, constant discussion of problem situations, so the task of introducing IC technology in this process is the accurate transfer of the content of the discussions. Individualization and autonomization of the educational process, its dependence on the results of the choice of educational content, and the use of pedagogical management tools change the philosophy of education for children and youth. The authors conclude that the formation of a digital generation, characterized by an increased level of digital literacy of children and youth, the possession of a certain level of digital capacity requires the use of strategies aimed at optimizing the learning process in a digital educational environment.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.500-509
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• 2007

In this paper, we propose a novel pc-based 8-channel USB interface digital multi-controller (DMC) has capacity to be able to adjust ultrasonic motor's (USM's) the parameters-frequency, amplitude, phase difference using FPGA. The proposed DMC can control parameters directly by digital logic through a FPGA. Since it has counter circuit for rotary encoder to measure position and velocity of USM, the other separate circuits are unnecessary. Therefore, it could reduce the size of controller and the production cost. Finally, to verify the performance of proposed DMC, we tested the speed characteristic of two types USM with no-load as adjusting the parameters.

• Journal of Digital Convergence
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• v.12 no.2
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• pp.285-293
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• 2014

Two-dimensional PDF417 bar code has a wide range of use and has a storage capacity to compress a large amount of data. With these characteristics, PDF417 has been used in various ways to prevent the forgery and alteration of important information in documents. On the other hand, previous decoding methods in PDF417 barcode are slow and inefficient because they simply employ the standard specifications of AIM (Association for Automatic Identification and Mobility). Therefore, this paper propose an efficient and fast algorithm of decoding PDF417 bar code. As a result, the proposed decoding algorithm will be more faster and efficient than previous methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10B
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• pp.857-865
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• 2004

Recently the interest in digital home services and its related technology has increased rapidly. Multimedia data transmission between digital devices that are connected to home network is essential function. This paper presents the design and implementation of multimedia streaming system based on IEEE1394 in Linux environment. The key features of proposed system are as follows. First, it can transmit and receive not only DV format data but also MPEG2-TS format data through IEEE1394 bus. Second, it uses device drivers that handling IEEE1394 and IEC61883 protocol transparently to reduce the complexity of communication program. Third, it applied capacity adaptation technique considering various specifications of PCs to get smooth streaming for HD data. These characteristics are tested on testbed of IEEE1394 based home network. The proposed media streaming technique can be used as a home media sever in Linux environment.

• The Journal of the Korea Contents Association
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• v.8 no.9
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• pp.42-54
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• 2008

In recent years, embedded systems have been expanding their application domains from traditional embedded systems such as military weapons, robots, satellites and digital convergence systems such as celluar phones, PMP(Portable Multimedia Player), PDAs(Personal Digital Assistants) to Next Generation Personal Computers(NGPCs) such as eating PCs, wearable computers. The NGPCs are network-based, human-centric digital information devices diverged from the traditional PCs used mainly for document writing, internet searching and database management. Wearable computers with battery capacity and memory size limitations have to use real-time operating systems with small footprints and low power management techniques to provide user's QoS in spite of hardware constraints. In this paper, we have designed and implemented a low-power RTOS (called eRTOS) for wearable computers. The implemented eRTOS has 18KB footprints and the dynamic power management and the device power management schemes are adapted in it. Experimental results with wearable computer applications show that the low power techniques could save energy up to 47 %.

• The Journal of the Korea Contents Association
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• v.5 no.6
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• pp.343-350
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• 2005

During the design of a successful digital watermarking systems, Pseudo-Noise(PN) sequences are widely used to modulate information bits into watermark signals. In this method, the number of bits that can be hidden within a small image by means of frequency domain watermarking is limited. In this paper, we show the possibility of introducing chaotic sequences into digital watermarking systems as potential substitutes to commonly used PN-sequences. And we propose a method that transforms the text to chaotic sequence. In our current implementation, we show how the sample text is expressed by an implied unit data(watermark) and the implied unit data is regenerated into the original left. Because we use this implied data as watermark for information hiding, we can insert much more watermark compared with previous method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7C
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• pp.696-705
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• 2005

The rapid progress of the software has enabled individuals to copy and remake digital contents, which was only done by professionals. However, this rapid growth of software has brought many other defects. As a solution to the problems, contents producer needs to have certification and inspection of its contents text and hold the proprietary rights. In this paper, the new video watermarking scheme is proposed which is appropriate for the requirements mentioned for digital video contents and it is applied to MPEG-2 video encoder and decoder. In order to insert watermark sequence for digital video data, watermarking used blocks reordering algorithm and SCL(secret code list). It is satisfied two properties of cryptography that confidentiality and integrity. We test the proposed algorithm to see its performance in terms of watermark capacity, compression robustness and visual quality impact. According to the experiment of proposed watermarking algorithm, we obtained satisfactory results that watermark can still be extracted after MPEG-2 re-encoding at lower bit rates. It is important property for data hiding and user authentication in video data.