• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.20-39
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• 2020

This paper considers a downlink multi-carrier cooperative non-orthogonal multiple access (NOMA) transmission, where no direct link exists between the far user and the base station (BS), and the communication between them only relies on the assist of the near user. Firstly, the BS sends a superimposed signal of the far and the near user to the near user, and then the near user adopts simultaneous wireless information and power transfer (SWIPT) to split the received superimposed signal into two portions for energy harvesting and information decoding respectively. Afterwards, the near user forwards the signal of the far user by utilizing the harvested energy. A minimum data is required to ensure the quality of service (QoS) of the far user. We jointly optimize power allocation, subcarrier allocation, time allocation, the power allocation (PA) coefficient and the power splitting (PS) ratio to maximize the number of data bits received at the near user under the energy causality constraint, the minimum data constraint and the transmission power constraint. The block-coordinate descent method and the Lagrange duality method are used to obtain a suboptimal solution of this optimization problem. In the final simulation results, the superiority of the proposed NOMA scheme is confirmed compared with the benchmark NOMA schemes and the orthogonal multiple access (OMA) scheme.

• The Journal of the Korea Contents Association
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• v.7 no.11
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• pp.130-139
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• 2007

As increasing the usefulness of wireless communication, there are developing the environment of ubiquitous that is combined the network of wireless and wire communication combinate type in various filed and in this network environment, u-campus constructions, based on ubiquitous sensor network, is developing. u-Campus is the new type campus which applies to ubiquitous computer technology and wireless network one. at this thesis, it is designed u-campus construction using zigbee technology with u-campus basic technology. u-Campus service, being subject to zigbee wireless communication skills, presents the members an convenient service using zigbee network.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.571-574
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• 2002

In a recent wireless network environments, dynamic host configuration protocol (BHCP) service is used to assign IP addresses to mobile terminals. In IPv6 networks, it is necessary to introduce the concept of handoff to support a seamless service to mobile terminals. In a general soft handoff technique used by code-division multiple acces (CDMA) communication systems, the powers received to base station are simply compared to determine which base station will handle the signal to and from each mobile termins. However, in IPv6 network, to transmit data-oriented services, it is necessary to support an enhanced soft handoff technique with more security and quality of service. In this paper, we propose a scheme to reduce a signaling process of handoff in IPv6 network. Also, we propose a technique to reduce wasted reservation resources and to guarantee quality of service (QoS) using DHCP.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.183-184
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• 2007

As the mobile communication service is widely used, the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But wireless repeaters has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we investigate the performance of adaptive variable step-size NLMS-based algorithms for cancelling the interference signals in the W-CDMA system under time-varying multipath channels. The criteria for comparison are tracking capability, convergence speed, and complexity.

• Convergence Security Journal
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• v.20 no.4
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• pp.169-176
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• 2020

Recently, the era in which various services using smart devices are used is sometimes referred to as the so-called "smart era". Among these, Smart Home Service' have not only brought about significant changes in the residential environment and culture, but are evolving very rapidly. and The 'Smart Home Service' provides more convenient services to users through communication between various electronic products in general homes, and has a bright future in the future. In particular,'Smart Home Service' provides various services combined based on IoT(Internet of Things) technology and wired/wireless communication in connection between various devices. However, such a "smart home service" inherits the security vulnerabilities of the underlying technologies such as the Internet of Things and wired and wireless communication technologies, and accidents that lead to the leakage of personal information and invasion of privacy continue to occur. So, it is necessary to prepare a countermeasure and prevention against the weak factors of the underlying technologies. Therefore, this paper is expected to be used as basic data for future application technology development and countermeasure technology by examining various security vulnerability factors of 'Smart Home Service'.

• Convergence Security Journal
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• v.16 no.5
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• pp.49-55
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• 2016

Recently mobile service industry has grown very rapidly. In this paper, We investigated the changes in mobile service network as well as security vulnerabilities of network in future 5G mobile service network, too. Recently, there are rapid developement of information and communication and rapid growth of mobile e-business users. Therefore We try to solve security problem on the internet environment which charges from wire internet to wireless internet or wire/wireless internet. Since the wireless mobile environment is limited, researches such as small size, end-to-end and privacy security are performed by many people. In addition, there is a need of internetworking between mobile and IoT services. Wireless Application Protocol has weakness of leaking out information from Gateway which connected wire and wireless communication. As such, We investigate the structure of mobile service network in order to gain security vulnerabilities and insights in this paper.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.1
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• pp.19-25
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• 2015

In this time, as an industrial society developed to a welfare society, more and more people want their quality of lives upgraded and specially customized service by mass production/mass consumption. And it leads to an increase of requiring service. There're active developments and studies on various IT equipment as the requirement made IT devices used in service. In this paper, we try to design and realize radio paging DID by using smart device to be used as a receiver of a radio pager which is broadly used at face to face service. Firstly, we used MCU to design and implement Wireless Calling Gateway which change radio calling signal of ISM band to smart device. A receiver of wireless caller used original receiver module. Also it used bluetooth module to communicate with smart device. It was possible to have satisfactory communication since radio paging signal converter and smart device were linked in 3M. Secondly, to indicate various paging information delivered from a radio pager, we realized DID application program by using Smart PAD. As a result, we could indicate various information compared to an original receiver which only could indicate letters or numeric data. Secondly, we implemented the DID app for wireless calls that can display a variety of information sent from a wireless pager. Was implemented using the Smart Pad. As a result, it is shown that can display a variety of information than the existing receiver.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.2
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• pp.95-101
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• 2012

In order to supply emotion service depending on user's emotional change in a mobile environment, various researches have been carried. This paper discusses a protocol for wireless charging and an embedded platform of the mobile emotional sensing device which supports that. Wireless charging process relieves user's vexatious task to charge the emotional sensing device. To support wireless charging, there are one basestation and several mobile devices. Basestation coordinates and controls the devices over wireless communication, as well as supplies energy. For 1:N communication we defines the network whose superframe is classified into four categories: a network join superframe, a charging request superframe, a charging superframe and an inactive superframe. Physical layer provides how to supply energy to the devices and communicate physically. Mobile device is equipped with energy charged circuits, which correspond with the defined energy supplying method, as well as bidirectional communication circuits. Mobile device monitors and analyzes its own battery status, and is able to send a request packet to basestation. Therefore, it can be charged before its battery is exhausted without user's perception.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.237-244
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• 2011

Vehicular communications extend their application areas by combining communication technologies with roads/vehicles, and one of major applications is Smart Highway project. Smart Highway is a new advanced highway system which enhances the current highway system in Korea by improving reliability, safety and convenience. In this paper, we introduce wireless access technologies for vehicular communications especially focusing on Smart Highway. We first introduce the overall communication system architecture and the basic service and communication requirements for Smart Highway. Then, we discuss wireless access technologies including L2-level hand-over scheme. In addition, the results of experimental measurements of Wireless Access in Vehicular Environments (WAVE) system are introduced.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.233-234
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• 2004

The study for ubiquitous computing infra is proceeding actively, it make possible to use service and access network anywhere, anytime because of wire/wireless communication technology and progress of hardware. Domestically, study for the network mobility support technology which is the key technology for future ubiquitous computing realization have progressed, but that is Insufficient. Especially, there is no study for independent mobility support study about railway wireless network. So, this study propose network mobility management technology for mobile network infra in railway and proper network model in train.