• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.38-44
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• 2006

The COMS(Communication, Ocean & Meteorological Satellite) is the geostationary satellite which will be performing three main objectives such as meteorological service, ocean monitoring and Ka-band satellite communications. In order to accomplish these missions, the COMS system needs to implement a specific electrical/mechanical interface functions which are requested by each payload units. This paper describes a on-board interface hardware design for COMS Meteorological Imager(MI). The Meteorological Imager Interface Unit(MI2U) achieves, through MIL-STD-15533 system bus, the interface between the Spacecraft Computer Unit(SCU) and the instrument which is dedicated to MI. MI2U provides a necessary power input to MI from +50V Power Supply Regulator(PSR), and allows adaptation of the specific payload interfaces and protocol to COMS spacecraft.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.83-89
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• 2014

A ku-band complementary cross-coupled differential voltage controlled oscillator is designed, measured and fabricated using $0.18-{\mu}m$ CMOS technology. A 2.4GHz of very wide frequency tuning at oscillating frequency of 14.5GHz is achieved with presented circuit topology and MOS varactors. Measurement results show -1.66dBm output power with 18mA DC current drive from 3.3V power supply. When 5V is applied, the output power is increased to 0.84dBm with 47mA DC current. -74.5dBc/Hz phase noise at 100kHz offset is measured. The die area is $1.02mm{\times}0.66mm$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.483-491
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• 2012

In vehicle-to-vehicle (V2V) communications, each vehicle should periodically disseminate a beacon message including the kinematics information, such as position, speed, steering, etc., so that a neighbor vehicle can better perceive and predict the movement of the vehicle. However, a simple broadcasting of such messages may lead to a low reception probability as well as an excessive delay. In this paper, we attempt to analyze the impact of the following key parameters of the beacon dissemination on the performance of vehicular networks: beacon period, carrier-sensing range, and contention window (CW) size. We first derive a beacon period which is inversely proportional to the vehicle speed. Next, we mathematically formulate the maximum beacon load to demonstrate the necessity of the transmit power control. We finally present an approximate closed-form solution of the optimal CW size that leads to the maximum throughput of beacon messages in vehicular networks.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.107-113
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• 2016

In this paper, we suggest a design method of a wide-band Butler matrix working at 5.9 GHz for V2X communication antennas. Since V2X communication needs beam-forming and beam-steering antennas to make transportation systems, mobile comm platforms, saturated frequency-resources, and signal TX-and-RX smart, multi-functional, resolved, and efficient utmost, respectively, the proper Butler matrix and its radiating elements as a low-profile geometry are realized. The constitutive components of the basic Butler matrix of a narrow band are designed first. And then, it is extended to a wide-band version to make its frequency-shift less affected by the event of the antenna system being mounted on a car body. The beam-forming and beam-steering performance is presented as the common feature tagged along with the different bandwidths of the frequency responses as the comparison between the narrow- and wide-band cases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.4
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• pp.188-194
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• 2014

V2I(Vehicular to Infrastructure) is a one kind of communication systems which is used between the base stations and mobile objects. In V2I communication system, it is difficult to obtain the desired communication performance. Beamforming technology is to find the optimal path. and it can be improved the communication performance. MUSIC algorithm can be estimated the direction of arrival. The directional vector of received signals and the eigenvector has orthogonal property. MUSIC algorithm uses this property. In V2I communication environment, real time optimal path is changed. By the high computational complexity of the MUSIC algorithm, the optimal path estimation error is generated. In this paper, we propose a method of computation reduction algorithm for MUSIC algorithm.

• Communications of the Korean Mathematical Society
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• v.20 no.2
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• pp.351-358
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• 2005

We study asymptotic equivalence between nonlinear difference system $$\Delta\chi(n)=f(n,\chi(n))$$ and its variational system $${\Delta}v(n)=f_{\chi}(n,0)v(n)$$.

• Communications of the Korean Mathematical Society
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• v.26 no.2
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• pp.305-320
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• 2011

The relations among various types of continuity of fuzzy proper function on a fuzzy set and at fuzzy point belonging to the fuzzy set in the context of $\v{S}$ostak's I-fuzzy topological spaces are discussed. The projection maps are defined as fuzzy proper functions and their properties are proved.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.10
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• pp.1589-1594
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• 2013

Vehicular communication is one of representative convergence technology which combines information technology and vehicle industry. Wireless Access in Vehicular Environments (WAVE) technology is vehicular communication standard which is widely used in the world. In this paper, we introduce service realization of WAVE based vehicular communication systems in the practical testbed. We review the overall WAVE based systems in brief and introduce the testbed. Then, we investigate various applications using vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. Based on realization of systems, we discuss practical implementation issues and the convergence area of WAVE systems.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.3 s.333
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• pp.17-24
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• 2005

We fabricated PIN-Photodiodes with a single mode fiber for analog communications and analyzed characteristics of the devices. The fabricated PIN-Photodiode shows a bandwidth of 1.5 GHz, a dark current of 20 p4 a capacitance of 0.48 pF, and the responsivity of 0.9 V/W, a second order distortion of -72 dBc. In this paper, we developed a new optical Packaging technology that is aligning in real-time monitoring of both responsivity and IM2 characteristics. As a result responsivity has been improved by 0.03 V/W, and also U has been improved by $3\~5\;dBc$. On the other hand, failure ratio has been reduced by $3.5\%$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.120-123
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• 2009

The WiBro to start June 2006 is mobile internet service with 60km/h, 3Mbps. And current WiBro service is used in Seoul, the metropolitan area and the local major cities. This study suggests WiBro technology and analyzes wireless communication technology to vehicle-to-infrastructure communications for the unmanned vehicle control. We were driving vehicle with two laptop computer's WiBro unit for V2I communication environment. So each RAS(Radio Access Station) on center is tested coverage area, transmission rate, latency rate, lost rate and transmission rate to parking area environment.