• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1764-1770
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• 2013

Use of the 5.1 channel audio signals suitable for the television system is improper for the radio broadcasting system, which uses the stereo audio system. Therefore, it is necessary to develop an audio down-mixer to convert 5.1 multi-channel audio signals to stereo signals for radio broadcasting. In this paper, a development of an audio down-mixer was carried out to convert 5.1 multi-channel audio signals to stereo signals. The down-mixer which was developed can use the audio signals separated from video signals, including sound signals or individual signals provided from 3-channel AES/EBU signals including Left(L), Right(R), Left Surround(Ls), Right Surround(Rs), Center(C) and Low Frequency Effect(Lfe) sounds as mixer inputs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4387-4404
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• 2015

The energy-efficient design of sensing-based spectrum sharing of a multi-input and multi-output (MIMO) cognitive radio (CR) system with imperfect multiple antenna spectrum sensing is investigated in this study. Optimal resource allocation strategies, including sensing time and power allocation schemes, are studied to maximize the energy efficiency (EE) of the secondary base station under the transmit power and interference power constraints. EE problem is formulated as a nonlinear stochastic fractional programming of a nonconvex optimal problem. The EE problem is transformed into its equivalent nonlinear parametric programming and solved by one-dimension search algorithm. To reduce searching complexity, the search range was founded by demonstration. Furthermore, simulation results confirms that an optimal sensing time exists to maximize EE, and shows that EE is affected by the spectrum detection factors and corresponding constraints.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.19-29
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• 2010

Recently, spectrum sensing has been intensively studied as a key technology in realizing the cognitive radio. There have been advances in the performance of spectrum sensing through both multi-antenna and cooperative sensing schemes. In this paper, the performances and complicated scenarios of the latest spectrum sensing schemes are analytically compared and arranged into a technical tree while considering practical concerns. This paper will give a macroscopic view of spectrum sensing and will also provide insight into future spectrum sensing works.

• Journal of Information Processing Systems
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• v.8 no.1
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• pp.1-20
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• 2012

The most important criterion for achieving the maximum performance in a wireless mesh network (WMN) is to limit the interference within the network. For this purpose, especially in a multi-radio network, the best option is to use non-overlapping channels among different radios within the same interference range. Previous works that have considered non-overlapping channels in IEEE 802.11a as the basis for performance optimization, have considered the link quality across all channels to be uniform. In this paper, we present a measurement-based study of link quality across all channels in an IEEE 802.11a-based indoor WMN test bed. Our results show that the generalized assumption of uniform performance across all channels does not hold good in practice for an indoor environment and signal quality depends on the geometry around the mesh routers.

• Advances in aircraft and spacecraft science
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• v.1 no.4
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• pp.455-469
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• 2014

High-precision autonomous localization technique is essential for future Mars rovers. This paper addresses an innovative integrated localization algorithm using a multiple information fusion approach. Firstly, the output of IMU is employed to construct the two-dimensional (2-D) dynamics equation of Mars rover. Secondly, radio beacon measurement and terrain image matching are considered as external measurements and included into the navigation filter to correct the inertial basis and drift. Then, extended Kalman filtering (EKF) algorithm is designed to estimate the position state of Mars rovers and suppress the measurement noise. Finally, the localization algorithm proposed in this paper is validated by computer simulation with different parameter sets.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.69.1-69.1
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• 2011

The multi-band receiving feed which is one of the unique characteristics of the Korean VLBI Network (KVN) system compare to the other VLBI network enables to study precise astrometry with a source frequency phase referencing (SFPR) techniques. SFPR almost perfectly compensates the dominant non-dispersive tropospheric fluctuations by observing sources with multi-frequency simultaneously, and it also corrects the dispersive ionospheric fluctuations by adding a slow source-switching observation. In this talk, I will present the results from the KVN astrometric observations with SFPR and the achievable astrometric accuracy in KVN will be discussed.

• Information and Communications Magazine
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• v.32 no.2
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• pp.114-116
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• 2015

점점 더 가속화하고 있는 이동통신 기술의 진보에서 비롯된 통신 환경의 변화는 폭증하는 데이터 트래픽에 대한 효율적인 관리 제어를 요구하고 있으며, 이러한 요구에 대응한 다양한 방식의 시스템들이 개발되고 있다. 이 중에서 RU(Radio Unit)와 DU(Digital Unit)의 분리 및 관련 기술의 고도화는 이동통신 시스템 환경 구축의 효율성과 유연성을 제고하는 신기술 방식으로 자리 잡고 있다. 본 고에서는 RF 처리부를 소형 모듈화한 RF 단위모듈을 이용하여 RU를 구현함으로써, 다양한 용량과 서비스 영역을 제공할 수 있는 기지국 솔루션 개발현황을 소개하고자 한다.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.77-81
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• 2011

This paper presents a single-pole eight-throw(SP8T) switch based on proposed a radio-frequency(RF) microelectromechanical systems (MEMS) switches. The proposed switch was driven by a double stop(DS) comb drive, with a lateral resistive contact. Additionally, the proposed switch was designed to have tapered signal line and bi-directionally actuated. A forward actuation connects between signal lines and contact part, and the output becomes on-state. A reverse actuation connects between ground lines and contact part, and the output becomes off-state. The SP8T switch of 3-stage tree topology was developed based on an arrangement of the proposed RF MEMS switches. The developed SP8T switch had an actuation voltage of 12 V, an insertion loss of 1.3 dB, a return loss of 15.1 dB, and an isolation of 31.4 dB at 6 GHz.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.3
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• pp.22-27
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• 2012

In oceanic flight routes, HF radio and satellite data links have been used for air-to-ground communication, but these systems have long propagation delay and low data throughput. In this paper, we propose a reliable system to overcome the weakness of current HF radio and satellite communication systems for oceanic aeronautical flight routes. The proposed scheme uses only one aeronautical VHF channel in multi-hop oceanic communication environments and supports a hybrid type of multiple access, which consists of random access and TDMA (Time Division Multiple Access) scheme. The proposed system improves performance on delay and throughput as an effective solution to communicate end-to-end on the oceanic flight routes and strengthens the reliability of oceanic aeronautical communication.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.38.1-38.1
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• 2018

A merging galaxy cluster is a useful laboratory to study many interesting astrophysical processes such as intracluster medium heating, particle acceleration, and possibly dark matter self-interaction. However, without understanding the merger scenario of the system, interpretation of the observational data is severely limited. In this work, we focus on the off-axis binary cluster merger Abell 115, which possesses many remarkable features. The cluster has two cool cores in X-ray with disturbed morphologies and a single giant radio relic just north of the northern X-ray peak. In addition, there is a large discrepancy (almost a factor of 10) in mass estimate between weak lensing and dynamical analyses. To constrain the merger scenario, we perform a hydrodynamical simulation with the adaptive mesh refinement code RAMSES. We use the multi-wavelength observational data including X-ray, weak-lensing, radio, and optical spectroscopy to constrain the merger scenario. We present detailed comparisons between the simulation results and these multi-wavelength observations.