• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.181-184
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• 2010

이 논문에서는 Linking Open Data 프로젝트를 기반으로 개발된 어플리케이션들의 접근제어를 위하여 기존 RBAC 모델을 연결 데이터에 적용 가능하도록 확장한 모델을 제안한다. 제안 모델은 온톨로지의 구조에 RBAC 모델에 적용할 수 있도록 RBAC 모델에 사용자를 위한 제약조건을 온톨로지로 표현하였으며, 지능형 엔진을 통해 사용자에게 적합한 권한을 추론한다. 사용자에 적합한 접근권한을 주기 위해 FOAF, flickr, 트위터 등의 데이터가 연결되어있는 연결 데이터로부터 사용자 프로파일을 확장할 수 있는 정보를 획득할 수 있으며, 이를 기존 정보에 확장하여 사용자의 권한을 부여한다. 본 논문에서 제안한 모델의 실효성을 검증하기 위하여 DBpedia Mobile을 위한 접근제어 시스템을 설계하였으며 안드로이드 SDK 환경에 프로토타입을 구현하여 제안 모델을 연결 데이터 환경의 어플리케이션에 적용 가능함을 보였다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.1
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• pp.1-11
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• 2018

This paper provides field test results to confirm and compare the receiving characteristics of digital radio in various environments. HD Radio and DRM+ was used for the in-band method, while DAB/DAB+/T-DMB were used for the out-of-band method. To run field tests for digital radio, a transceiver test bed was constructed in a region in Korea selected as suitable for the testing, and indoor and outdoor reception tests were conducted by selecting 16 test points with different levels of multipath. Not only was the receivability tested at the test point, but ATT margin was also applied, in order to derive the minimum reception level. Through various analyses, the findings obtained through the field tests can aid in the setting of a standard for determining the method of digital radio transmission to ensure a smooth reception environment for consumers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1754-1769
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• 2013

For the purpose of enhancing the spectrum efficiency, cognitive radio (CR) technology has been recently proposed as a promising dynamic spectrum allocation paradigm. In CR, spectrum sensing is the key capability of secondary users in a cognitive radio network that aims for reducing the probability of harmful interference with primary users. However, the individual CRs might not be able to carry out reliable detection of the presence of a primary radio due to the impact of channel fading or shadowing. This paper studies the cooperative spectrum sensing scheme as means of optimizing the sensing performance in AWGN and Rayleigh channels. Results generated from simulation provide evidence of the impact of channel condition on the complementary receiver operating characteristic (ROC). Based on the results, it was found that with constant local SNRs at the secondary users, the probability of missed detection ($P_m$) of cooperative spectrum sensing in a cognitive radio network, calculated using a closed form expression, can be significantly minimized. Thus, the paper illustrates that improvement of the detection performance of the CR network can be achieved by establishing a centralized cooperation among neighboring cognitive radio users. Finally, verification of the validity of the fusion schemes utilized for combining the individual CR decisions is provided.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.165-170
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• 2005

In this paper, influences of a ultra wideband (UWB) antenna on impulse channel measurement are investigated in time domain (TD) and frequency domain (FD) as well. Firstly, impulse response of an UWB antenna is obtained and then using the result of impulse response of the UWB antenna, influences of the antenna on impulse radio channel is analyzed. Furthermore, using the impulse response of the UWB anenna, method of impulse radio channel analysis is presented by excluding the effect of the antenna from an impulse radio channel. For verifying the theory, a modified conical monopole antenna is designed for measuring impulse radio channel and its impulse response is obtained. After that, in order to investigate the effects of the UWB antenna on an impulse radio channel, multipath environments are set up in an anechonic chamber and transmission coefficient for each multipath environment is measured with an aid of vector network analyzer. Data measured in frequency domain is transformed into those in time domain by way of signal processing. Measurement shows that such properties of the antenna as dispersion and ringing affect impulse radio channel. Moreover, using the impulse response of the antenna, impulse response of only multipath channel is obtained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.10
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• pp.2338-2356
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• 2013

In cognitive radio networks, acquiring the position information of the primary user is critical to the communication of the secondary user. Localization of primary users can help improve the efficiency with which the spectrum is reused, because the information can be used to avoid harmful interference to the network while simultaneity is exploited to improve the spectrum utilization. Despite its inherent inaccuracy, received signal strength based on range has been used as the standard tool for distance measurements in the location detection process. Most previous works have employed the path-loss propagation model with a fixed value of the path loss exponent. However, in actual environments, the path loss exponent for each channel is different. Moreover, due to the complexity of the radio channel, when the number of channel increases, a larger number of RSS measurements are needed, and this results in additional energy consumption. In this paper, to overcome this problem, we propose using the Bayesian compressive sensing method with a calibrated path loss exponent to improve the performance of the PU localization method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.549-556
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• 2011

In this paper, high performance radio buoy system for inshore and deep sea fishery is proposed and implemented. Binary FSK modulation technique is used for real-time communication & control between buoys and buoy finder, and optimum access protocol is adopted for minimizing the power consumption of radio buoy system. Using the GPS and sensor techniques, location and environments of radio buoy can be accurately monitored and traced by the mother ship. Developed buoy system with 10 W transmitting power can cover over 120km coastal range and operate more than 73 days of battery life. Proposed digital coding methods can also assure high security from burglary and loss.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.1
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• pp.28-36
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• 2020

Due to the continued demand for high-definition video, video compression technology is steadily developing and the High Efficiency Video Coding standard was established in 2013. However, despite the development of this compression technology, it is very difficult to smoothly transmit VGA-level videos in Ultra-narrowband environments. In this paper, the target information preprocessing algorithm is presented for smooth transmission of target images moving in forest or open-terrain in Ultra-narrowband environment. In addition, for algorithm verification, the target information preprocessing algorithm was simulated and the simulated results were compared with the video compression result without the algorithm being applied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3711-3730
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• 2014

Cognitive radio networks (CRNs) have emerged as a promising solution to enhance spectrum utilization by using unused or less used spectrum in radio environments. The basic idea of CRNs is to allow secondary users (SUs) access to licensed spectrum, under the condition that the interference perceived by the primary users (PUs) is minimal. In CRNs, the channel availability is uncertainty due to the existence of PUs, resulting in intermittent communication. Transmission control protocol (TCP) performance may significantly degrade in such conditions. To address the challenges, some transport protocols have been proposed for reliable transmission in CRNs. In this paper we survey the state-of-the-art transport protocols for CRNs. We firstly highlight the unique aspects of CRNs, and describe the challenges of transport protocols in terms of PU behavior, spectrum sensing, spectrum changing and TCP mechanism itself over CRNs. Then, we provide a summary and comparison of existing transport protocols for CRNs. Finally, we discuss several open issues and research challenges. To the best of our knowledge, our work is the first survey on transport protocols for CRNs.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.13-23
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• 2001

Recently, the demands on the short range radio device has been highly increasing, with the advantage of its mobility and improvement of its reliability which has been ensured by development of digital communication techniques. This study suggests the direction for the improvement of the national regulations in the technical, administrative and regulatory aspects, discussing the present situation of the regulations. While suggesting to launch the study on spectrum source and RE environments, we expect that several proposals in this paper will give a satisfaction on the development of strategy for spectrum management, development of radio technology and booming the short range radio communication.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.195-201
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• 2011

Cognitive radio (CR), which is proposed as a technology that utilizes the frequency resources effectively, has studied to relive scarcity of the frequency resources. CR provides opportunistically under-utilize licensed frequency to the secondary user. However, in the wireless channels, due to the effect of fading and shadowing environments, spectrum sensing performance is compromised. Besides, to detect and classify various CR systems, a novel spectrum sensing algorithm is needed. Therefore, in this paper, we proposed the spectrum sensing algorithm with water marking scheme.