• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.833-836
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• 1987

The error probability for coherent frequency-hopped spread-spectrum multiple-access communications is computed. We employ PSK as a modulation scheme. The channel capacity is performance measure and the minimum bit signal-to-noise ratio for reliable communications is obtained.

• International Commerce and Information Review
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• v.8 no.1
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• pp.143-163
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• 2006

The terms electronic trade, electronic trading and electronic commerce are often used interchangeably, and refer to trading transactions conducted using electronic media. Electronic trade is business-to-business transactions in an industrial context, while electronic commerce refers to retailing and the consumer sector as well as mass marketing. The Electronic trade process is defined as a flow of information (documents) exchanged between enterprises and trade-related firms (shipping companies, foreign exchange banks, forwarders, etc.) in the course of implementing a series of export and import procedures. Electronic trading systems exploit information technology to improve the efficiency of communications and/or to alter the nature of inter-organizational transactions. Many studies exist about the adoption of inter-organizational systems (IOS) and electronic data interchange (EDI), but few focus on electronic trade. The literature on exporting companies's electronic trade adoption and implementation, although extensive, consists mainly of exploratory studies focusing on technological characteristics such as barriers, benefits and usage. The purpose of this study is to broaden this perspective by investigating the environmental, organizational and technological drivers of business-to-business e-commerce adoption.

• Information and Communications Magazine
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• v.26 no.3
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• pp.32-40
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• 2009

최근 전자전 (EW : Electronic Warfare)은 현대전의 핵심으로 자리매김하고 있다. 전자전에서 재밍 (Jamming)은 적군의 통신을 교란시키는 전자공격 (EA : Electronic Attack)을 의미하는 것으로 재밍 전술은공격 대상에 따라서 여러 가지로 나눌 수 있다. 본고에서는 군통신에서 사용되는 전자방해책 (ECM : Electronic Counter Measure)인 재밍 기술을 소개하고, 재밍 신호에 대한 대책으로 재밍 신호를 효과적으로 검출하고 제거할 수 있는 전자방해방어책인 (ECCM : Electronic Counter Counter Measure) 항재밍 (Anti-Jamming) 방안도 함께 분석 소개하고자 한다.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.97-99
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• 1998

A optical phase modulator of 5Gbps was fabricated on LiNbO$_3$ by Ti diffusion for optical communications. In this Paper the pigtailing, mode patterns and insertion loss were discussed. And the device Properties of driving voltage and bandwidth were measured.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4268-4290
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• 2015

Future mobile communications face enormous challenges as traditional voice services are replaced with increasing mobile multimedia and data services. To address the vast data traffic volume and the requirement of user Quality of Experience (QoE) in the next generation mobile networks, it is imperative to develop efficient content distribution technique, aiming at significantly reducing redundant data transmissions and improving content delivery performance. On the other hand, in recent years cloud computing as a promising new content-centric paradigm is exploited to fulfil the multimedia requirements by provisioning data and computing resources on demand. In this paper, we propose a cooperative caching framework which implements State based Content Distribution (SCD) algorithm for future mobile networks. In our proposed framework, cloud service providers deploy a plurality of cloudlets in the network forming a Distributed Cloud Service Network (DCSN), and pre-allocate content services in local cloudlets to avoid redundant content transmissions. We use content popularity and content state which is determined by content requests, editorial updates and new arrivals to formulate a content distribution optimization model. Data contents are deployed in local cloudlets according to the optimal solution to achieve the lowest average content delivery latency. We use simulation experiments to validate the effectiveness of our proposed framework. Numerical results show that the proposed framework can significantly improve content cache hit rate, reduce content delivery latency and outbound traffic volume in comparison with known existing caching strategies.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1057-1066
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• 2023

Global Navigation Satellite System (GNSS) is one of the core technologies for the 4th Industrial Revolution, and its importance is increasingly highlighted in the next generation communications and smart mobility requiring the accurate location information. As the development of the high-performance/high-precesion GNSS technology makes it possible to obtain the more accurate locations information, the location based products and systems, which provide the high-quality service, are being researched/developed. In this paper, we present the results of a survey on the recent research trends and examples, utilizing GNSS technology in fields of the next generation communications and smart mobility, and analyzes the results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2561-2576
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• 2013

The ship ad-hoc network (SANET) extends the coverage of the high data-rate terrestrial communications to the ships with the reduced cost in maritime communications. Cognitive radio (CR) has the ability of sensing the radio environment and dynamically reconfiguring the operating parameters, which can make SANET utilize the spectrum efficiently. However, due to the dynamic topology nature and no central entity for data fusion in SANET, the interference brought into the primary network caused by the hidden primary user requires to be carefully managed by a sort of decentralized cooperative spectrum sensing schemes. In this paper, we propose a self-weighted decentralized cooperative spectrum sensing (SWDCSS) scheme to solve such a problem. The analytical and simulation results show that the proposed SWDCSS scheme is reliable to detect the primary user in SANET. As a result, secondary network can efficiently utilize the spectrum band of primary network with little interference to primary network. Referring the complementary receiver operating characteristic (ROC) curves, we observe that with a given false alarm probability, our proposed algorithm reduces the missing probability by 27% than the traditional embedded spectrally agile radio protocol for evacuation (ESCAPE) algorithm in the best condition.

• Proceedings of the Korean Vacuum Society Conference
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• 2009.02a
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• pp.67-67
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• 2009

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.18 no.8
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• pp.101-102
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• 2000