• Journal of KIISE:Computing Practices and Letters
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• v.11 no.2
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• pp.180-191
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• 2005

The rapid growth of mobile communication technology has provided the expansion of mobile internet services, particularly mobile commerce takes much weight among them. Even though current mobile commerce service has serious problems which check its development, such as limited contents, expensive charge system and hardware restriction of mobile device, it is strongly expected as one of the next generation Internet services. In this paper, we summarize the problems like above and provide some total solution to meet them as follows: a function for automatic gathering of product information on online Internet and automatic translation it to data for mobile commerce, a middlelet application which provides functions for product search and order on the mobile device through off-line processing, and a function of user adaptive recommendation. We have actually designed and implemented the proposed system and verified the functions and effectiveness of the system.

• Journal of Broadcast Engineering
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• v.24 no.4
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• pp.643-659
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• 2019

In this paper, the technology verification of next generation broadcasting technology and service suitable for domestic broadcasting environment was carried out to build and activate domestic terrestrial UHD broadcasting. ATSC 3.0-based mobile HD broadcasting is currently conducting experiments with various parameters from broadcasting companies, research institutes and others. However, experiments on integrated transmissions, including audio services, have not been carried out. Through this experiment, we first performed the theory and experiment on the maximum number of ATSC 3.0 based UHD broadcasting service, maximum service number of HD broadcasting considering mobility, and maximum service number of audio broadcasting within one channel (6MHz). Second, parameters for integrated transmission of each service (UHD broadcasting, mobile HD and audio broadcasting) in one channel were derived. Finally, we studied technical possibilities through field tests that we receive while moving directly in the field.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.607-610
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• 2012

The objective of this paper is to provide service continuity based on an efficient subchannel allocation in OFDMA systems. The management for handover are necessary to maintain the QoS requirements of different multimedia applications because the service continuity may be defected by some delay and information loss.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6B
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• pp.573-587
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• 2003

Due to the growth of mobile communication and the popularization of Internet, it is expected that wired and wireless communication network of the next generation will be integrated and flourished with IP-based. There have been a great deal of research efforts to provide mobile IP service onthe existing lower layer. The location update and the paging scheme is one of the most challenging technical issues for this topic. In this thesis, a paging method based on the distance-based location update scheme is proposed for IP network to support mobility in layer 3. The proposed scheme is implemented and verified with the OPNET.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.668-675
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• 2001

Recently, the performance of the commercial PCS(Personal Communication Service) system has been improved to the uppermost limit and ultimately the next generation mobile communication is to be realized by IMT-2000 (International Mobile Communication-2000) to provide multimedia services. Therefore, the new type receiving system is researched actively and one of the most important part in a receiver is direct conversion method. The direct conversion method is suitable for low power consumption, small size, MMIC, and low price, which is to be adopted to the next generation mobile communication systems. In this case, however, several problems occur due to DC-offset. The DC-offset suppresses amplification of the required signal because of the leakage signal of frequency synthesizer in the system. In this thesis, the removing method of DC-offset was considered. There are four removing techniques of DC-offset, which are AC-coupling, large capacitor, DC-feedback loop, and DC-free coding. Among these, the AC-coupling method is the most simplest method and the DC-feedback loop method has the best performance. Then, the performance of the AC-coupling method and DC-feedback loop method are evaluated by HP's ADS simulation tool. As a result, the AC-coupling method cannot be used to the digital communication systems due to data loss. On the other hand, it was confirmed that the DC-feedback loop method is suitable for the direct conversion receiver.

• International Journal of Contents
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• v.8 no.4
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• pp.12-20
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• 2012

For a library to be able provide information services and fulfill its function as a knowledge convergence center capable of responding to various information demands, the development of next-generation information systems based on the latest information and communication technology is needed. The development of mobile information services using portable devices such smart phones and tablet PCs and information systems which incorporate the concepts of cloud computing, SaaS (Software as a Service), annotation and Library2.0 is also required. This paper describes a library information system that utilizes collective intelligence and cloud computing. The information system developed for this study adopts the SaaS-based cloud computing service concept to cope with the shift in the mobile service paradigm in libraries and the explosion of electronic data. The strengths of such a conceptual model include the sharing of resources, support of multi-tenants, and the configuration and support of metadata. The user services are provided in the form of software on-demand. To test the performance of the developed system, the efficiency analysis and TTA certification test were conducted. The results of performance tests, It is encouraging that, at least up to 100MB, the job time is approximately linear and with only a moderate overhead of less than one second. The system also passed the level-3 or higher criteria in the certification test, which includes the SaaS maturity, performance and application program functions.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.26 no.2
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• pp.199-215
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• 2015

The objective of this study is to investigate and compare the situation of the informationization of public libraries between 2012 and 2014. Data were collected two times in both 2012 and 2014 using Internet survey. Survey contents were general information situation, softwares, digital service room, RFID, digital contents, mobile service, integrated digital services. Results show that library informationization went for demonstration effect for local residents, staff for library informationization was insufficient, KOLAS was still needed to be upgraded, and most of public libraries were insufficient for future digital services. As improvement plans, there are the development of next generation integrated system, expansion of mobile web and app service, and increasing digital contents. For further study, it provides a study of the use of digital contents and equipment on public libraries.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.10
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• pp.888-893
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• 2012

Quality of Service (QoS) provisioning is an important issue in the design of next generation wireless network. In visible light communication (VLC) networks, link switching is a solution to maintain or improve the quality of communication. In this paper, we propose a novel link switching scheme using the location of mobile nodes (MNs). The current serving transmitter uses location history of the MN to find out which neighbor transmitter the MN is approaching. This neighbor transmitter is chosen to inform the MN as the next serving transmitter. The simulation results show that our proposed scheme gains better performance than non-predictive link switching scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2073-2085
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• 2012

Recently, the International Telecommunication Union allocated the 470-862 MHz band to the digital broadcasting (DB) service. Moreover, the 790-862 MHz sub-band will be allocated to the next-generation mobile system, known as the International Mobile Telecommunication - Advanced (IMT-A), and to the DB on a co-primary basis in the year 2015. Currently, two candidate technologies are available to represent the IMT-A system; the Mobile WiMAX and Long Term Evolution - Advanced (LTE-A). One of the main criteria of the IMT-A candidate is to not cause additional interference to the primary service (i.e., DB). In this paper, we address the spectrum sharing issue between the IMT-A candidates and the DB service. More precisely, we investigate the interference effect between the DB service and the mobile network, which could be either LTE-A or WiMAX. Our study proposes a spectrum sharing model to take into account the impact of interference and evaluates the spectrum sharing requirements such as frequency separation and separation distance. This model considers three spectrum sharing scenarios: co-channel, zero guard band, and adjacent channel. A statistical analysis is performed, by considering the interferer spectrum emission mask and victim receiver blocking techniques. The interference-to-noise ratio is used as an essential spectrum sharing criterion between the systems. The model considers the random distribution of the users, antenna heights, and the bandwidth effect as well as the deployment environment in order to achieve spectrum sharing. The results show that LTE-A is preferable to WiMAX in terms of having less interference impact on DB; this can eventually allow the operation of both services without performance degradation and thus will lead to efficient utilization of the radio spectrum.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.770-777
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• 2007

Smaller cell size in the micro-cell or pico-cell structure brings about more frequent hand-overs between cells, and higher speed movement of the mobile terminal makes short the permissible time interval for executing these hand-over procedures. In this situation the hand-over failure may occur or some packets may be lost during the hand-over. Moreover a rapid degradation of throughput is triggered by packet re-transmission for compensating such errors. The QoS (Quality of Services) of mobile multimedia applications with higher bits rate requirements and higher speed mobility are severely affected by even shot service interruption. This paper proposes a new hand-over scheme to provide seamless services in the next generation mobile communication systems. Simulation is done to evaluate the performance of the proposed scheme based on its hand-over failure rate and packet loss rate.