• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1229-1238
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• 2005

OFDM(Orthogonal Frequency Division Multiplexing) communications system is very attractive for the high data rate wireless transmission. However, it may be distorted in the nonlinear HPA(High Power Amplifier) since OFDM signal has hish PAPR(Peak-to-Average Power Ratio). In this paper, a new method using control tone is studied for reducing the PAPR and we call it PCT(PAPR Control Tone) method. This proposed PCT method is to assign control tones for PAPR reduction at the predefined sub-carriers. After IFFT(Inverse Fast Fourier Transform) and PAPR calculation, the OFDM data signal of the lowest PAPR is selected to transmit. Unlike the conventional method, it can cut down the computational complexity because it does not require the transmission and demodulation process of side information about the phase rotation. Furthermore, if this method is made up in parallel configuration, it can solve the time delay problem so that it can be processed in real time processing. This proposed method is compared with the conventional selected mapping(SLM) technique. We find out the PAPR reduction performance and BER when the number of control tone is 6 and nonlinear HPA is considered.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.5
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• pp.445-453
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• 2016

This paper presents the implementation and design of the 1T-1R wireless HD video streaming systems over 28 GHz mmWave frequency using 3GPP LTE-TDD standard on NI USRP RIO SDR platform. The baseband of the system uses USRP RIO that are stored in Xilinx Kintex-7 chip to implement LTE-TDD transceiver modem, the signal that are transceived from USRP RIO up or down converts to 28 GHz by using self-designed 28 GHz RF transceiver modules and it is finally communicated HD video data through self-designed $4{\times}8$ sub array antennas. It is that communication method between USRP RIO and Host PC use PCI express ${\times}4$ to minimize delay of data to transmit and receive. The implemented system show high error vector magnitude performance above 25.85 dBc and to transceive HD video in experiment environment anywhere.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.50-64
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• 2013

In clustered sensor networks, since a CH (Cluster Head) collects data from its members and delivers the collected data to the sink, it is very important to prevent compromised nodes from joining a CH election and manipulating and fabricating the election result. In order to protect CH elections from compromised nodes, unpredictability, non-manipulability, and agreement property should be guaranteed in CH elections. However, existing CH election schemes cannot prevent intelligent compromised nodes from skilfully violating those properties via their cooperation. In this paper, we propose a scheme which protects the CH election process by detecting intelligent compromised nodes and excluding them. For every CH election round, each member gives a direct trust value to other members according to their behavior. Then a real reputation value is given to each member by combining the direct trust value and indirect trust values provided by other members. Then, each node evaluates the real reputation values of members in its cluster and excludes some untrustable nodes from CH candidates. The scheme greatly improves the non-manipulability and agreement property of CH election results compared to other rival schemes. Furthermore, the scheme preserves the high non-manipulability and the high agreement property even in an environment where message losses can happen.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.3-11
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• 2016

In the environment of Internet of Things (IoT), IoT devices are limited by physical components such as power supply and memory, and also limited to their network performance in bandwidth, wireless channel, throughput, payload, etc. Despite these limitations, resources of IoT devices are shared with other IoT devices. Especially, remote management of the information of devices and patients are very important for the IoT healthcare service, moreover, providing the interoperability between the healthcare device and healthcare platform is essential. To meet these requirements, format of the message and the expressions for the data information and data transmission need to comply with suitable international standards for the IoT environment. However, the ISO/IEEE 11073 PHD (Personal Healthcare Device) standards, the existing international standards for the transmission of health informatics, does not consider the IoT environment, and therefore it is difficult to be applied for the IoT healthcare service. For this matter, we have designed and implemented the IoT healthcare system by applying the oneM2M, standards for the Internet of Things, and ISO/IEEE 11073 DIM (Domain Information Model), standards for the transmission of health informatics. For the implementation, the OM2M platform, which is based on the oneM2M standards, has been used. To evaluate the efficiency of transfer syntaxes between the healthcare device and OM2M platform, we have implemented comparative performance evaluation between HTTP and CoAP, and also between XML and JSON by comparing the packet size and number of packets in one transaction.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.25-36
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• 2016

The goal of the SmartGrid is to maximize energy efficiency by exchanging bi-directional real-time power information with the help of ICT(Information and Communication Technology). In this paper, we propose a "JRS-MS" (Joint Routing and Scheduling for Multi-channel SmartGrid) algorithm that uses numerical modeling methods in IEEE 802.11s based STDMA multi-channel SmartGrid NAN networks. The proposed algorithm controls the amount of data transmission adaptively at the link layer and finds a high data-rate path which has the least interference between traffic flows in multi-channel SmartGrid NAN networks. The proposed algorithm improve transmission performance by enhancing network utilization. By comparing the results of performance analysis between the proposed algorithm and the JRS-SG algorithm in the previous paper, we showed that the JRS-MS algorithm can improve transmission performance by maximally utilizing given network resources when the number of flows are increasing in the multi-hop NAN wireless mesh networks.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.6-14
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• 2011

The fast growing of the number of users requires the development of reliable communication systems able to provide higher data rates. In order to meet those requirements, techniques such as Multiple Input Multiple Out (MIMO) and Orthogonal Frequency Division multiplexing (OFDM) have been developed in the recent years. In order to combine the benefits of both techniques, the research activity is currently focused on MIMO-OFDM systems. In addition, for a fast wireless channel environment, the data rate and reliability can be optimized by setting the modulation and coding adaptively according to the channel conditions; and using sub-carrier frequency, and power allocation techniques. Depending on how accurate the feedback-based system obtain the channel state information (CSI) and feed it back to the transmitter without delay, the overall system performance would be poor or optimal. In this paper, we propose a Signal to Noise Ratio (SNR) estimation algorithm where the preamble is known for both sides of the transciever. Through simulations made over several channel environments, we prove that our proposed SNR estimation algorithm is more accurate compared with the traditional SNR estimation. Also, We applied AMC on several channel environments using the parameters of IEEE 802.11n, and compared the Throughput performance when using each of the different SNR Estimation Algorithms. The results obtained in the simulation confirm that the proposed algorithm produces the highest Throughput performance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.5
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• pp.919-929
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• 2013

Recently, a variety of IT technologies are applied to the vehicle. However, some vehicle-IT technologies without security considerations may cause security problems. Specially, some researches about a smart key system applied to automobiles for authentication show that the system is insecure from replay attacks and modification attacks using a wireless signal of the smart key. Thus, in this paper, we propose an authentication method for the driver by using driving patterns. Nowadays, we can obtain driving patterns using the In-vehicle network data. In our authentication model, we make driving ppatterns of car owner using standard normal distribution and apply these patterns to driver authentication. To validate our model, we perform an k-fold cross validation test using In-vehicle network data and obtain the result(true positive rate 0.7/false positive rate is 0.35). Considering to our result, it turns out that our model is more secure than existing 'what you have' authentication models such as the smart key if the authentication result is sent to the car owner through mobile networks.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.744-753
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• 2015

This paper presents the results of research on developing marine unified communications to provide VoIP service based on marine satellites. With the recent popularity of smart-phones and other mobile devices, the demand for Internet-based wired and wireless unified technology has been growing in marine environments, and increasing interest is being directed to VoIP products and service models with high price competitiveness and the ability to deliver a variety of services. In this regard, this research designed three instruments, developed their unit modules, and verified their performances. These three instruments included the following: (1) a marine VoIP module equipped with an analogue gateway that can be linked to the existing devices used in vessels, which is more than 80% smaller than that of a land system; (2) a text/voice/video engine for marine satellite communications that runs on technology that minimizes communication data usage, which is a core technology for a marine VoIP service; and (3) a unified communication service that can support multilateral cloud-based message conversations, telephone number-based call functions, and voice/video calling between a private space in a ship and shore.

• Journal of Distribution Science
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• v.10 no.11
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• pp.89-99
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• 2012

Purpose - Mobile devices, especially mobile terminals capable of telecommunication and wireless connectivity, are leading the advancements in consumer electronics. Digital convergence drives the functions of various devices, such as cellular phones, MP3 players, personal digital assistants, and gaming, into a single device. This trend would continue and applications such as digital audio and video streaming (including personalized content delivery mechanisms) would soon be on a handheld device. As customers want mobile convergence devices, manufacturers are driving new initiatives in the emerging mobile device market. Given the roles played by device design and service content in user satisfaction of a mobile convergence device, this study focuses on identifying and measuring the constructs for the process by which user satisfaction is achieved. This study synthesizes the expectation-disconfirmation paradigm with empirical theories in user satisfaction. Device and service levels are separated, and nine key constructs for user satisfaction of mobile convergence devices are proposed. Insight into this process could help web-based businesses to improve user satisfaction, thus enhancing the effectiveness of e-commerce for sellers and buyers. Research design, data, methodology - This study draws on three users of mobile convergence devices as examples. To test there search model and hypotheses, survey questionnaires were sent to 607 mobile device users. Mobile device users were initially identified from several members, and subjects were randomly drawn. Data from 577 survey responses were finally analyzed. The unit of measurement and analysis in this research study is at a personal level. Results - The measurements for the constructs were developed and tested in a two-phase study. In the first phase, the device and service dimensions were identified, and instruments for measuring them were developed and tested. In the second phase, using the salient dimensions of the device and service as the formulating first-order factors, instruments were developed and empirically tested to measure satisfaction of the device and service. In measuring satisfaction of mobile convergence devices, the critical tasks are to identify the key constructs of such user satisfaction and to develop validated instruments to measure them. Hence, the results of this study have immediate implications for businesses and for research in user satisfaction of mobile convergence devices. Conclusions - This study provides reliable instruments for operationalizing key constructs in the analysis of user satisfaction of mobile convergence devices within the expectation-disconfirmation paradigm. Hence, convergence device makers will be able to examine whether their websites meet their customers' expectations by examining the device aspect of the mobile convergence device customers, and the service aspect expectations and disconfirmation. Moreover, the introduction of expectation and disconfirmation constructs brings the marketing aspect of convergence devices into focus for such retailers, an aspect crucial to the effective design of websites for online businesses. In addition,this study provides the metrics required to initiate future studies on user satisfaction of mobile convergence devices.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.307-315
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• 2005

In the ubiquitous computing environments, ICT industries of current society are developed in enormous growth. Medicine or patients with mobile devices can access at any time, any place. The medical procedures at the patient bedside are out of the scope of current systems, which means that patient record and image data access during the medical visit or the execution, recording and confirmation of the medicine prescriptions, still do not enjoy computerized support. Today, the exchange of medical images and clinical information is well defined by DICOM and HL7 standards. The DICOM independent terminal equipment image access system was developed in which a DICOM Engine acts as the gateway between a PACS DB and user's terminal. Implementation system is compatible with most currently available Integration system models. This paper presents a software technology where the medical and nursing staff will be equipped with any device connected by wire and wireless to a central server that provides access to the electronic patient records and that will actively inform about tasks pending distribution. The prototype described in this article implements a medical images and structured reports server that makes the search and recovery of data stored in the DICOM standard possible.