• Journal of Korea Multimedia Society
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• v.4 no.2
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• pp.145-160
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• 2001

With the rapid of computer applications and digital communication networks, group based applications on the open network have been common tendency. The multicast infrastructure has played an important researching part in this application area. However the conventional solutions to achieve the secure and efficient structure don't satisfy all requirements. In this study, we classified and analyzed several existing multicast key management structure on the safety, the efficiency and the strengthen. Based on the analysis, we developed a new secure and efficient multicast key management structure. By comparing various aspects, that the number of communication and computation, of the new and the conventional methods, we were able to demonstrate the effectiveness of the proposed method.

• Journal of Integrative Natural Science
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• v.10 no.4
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• pp.216-224
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• 2017

In the terrain of the Korean peninsula, mountainous and flat lands are complexly distributed in small areas. Therefore, local severe weather develops and disappears in a short time due to the influence of the terrain. Particularly in the case of local severe weather with heavy wind that has the greatest influence on aviation meteorology, the scale is very small, and it occurs and disappears in a short time, so it is impossible to predict with fragmentary data alone. So, we use weather radar to detect and predict local severe weather. However, due to the development of wireless communication services and the rapid increase of wireless devices, radio wave jamming and interference problems occur. In this research, we confirmed through the cases that when the radio interference echo which is one of the non-precipitation echoes that occur during the operation of the weather radar is displayed in the image, its form and shape are shown in a long bar shape, and have a strong dBZ. We also found the cause of the interference through the radio tracking process, and solved through the frequency channel negotiation and AP output minimizing. The more wireless devices increase as information communication technology develops in the future, the more emphasized the problem of radio wave interference will be, and we must make the radio interference eliminated through the development of the radio interference cancellation algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.6
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• pp.721-728
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• 2015

IOT has evolved from the internet for human oriented, therefore our life is more advanced growth smartly. IoT is the network of physical objects or things embedded with electronics, software, sensors and connectivity to enable it to achieve greater value and service by exchanging data with the manufacturer, operator or other connected devices. Until now many researches have been studied for centering keyword for detecting emerging technology of future and scientometric analysis among the papers. This paper propose searching method of emerging technology for the IOT (internet of things) and smart device which are recently interesting area via dynamic analysis for keyword mapping.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.465-473
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• 2012

In this study, a novel dual band planar monopole antenna for wireless local area network (WLAN)/ Worldwide Interoperability of Microwave Access (WiMAX) application was designed, fabricated, and measured. The proposed antenna consists of two hook shaped strips, an asymmetric ground plane, and a rectangular slit in the ground plane. Acceptable agreements between the measured and simulated results are achieved. Numerical and experimental results demonstrate that the proposed antenna satisfies the 10 dB impedance bandwidth requirement while covering the WLAN and WiMAX bands simultaneously. This paper also presents and discusses the 2D radiation patterns and 3D gains according to the results of the experiment that was conducted.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.69-75
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• 2010

In this paper, we analyze an effect co-existence between digital television (DTV) and 802.22 wireless regional area network (WRAN) systems. We set DTV as an interfering system and 802.22 WRAN as a victim system. When they share the same spectrum, we calculate the minimum separation distance. In analysis, we compare a minimum coupling loss (MCL) with a transmission loss (TL) for determining whether there exists the potential interference or not. The minimum separation distance is determined when the TL is larger than the MCL. In this case, the DTV system does not affect any harmful effect to 802.22 WRAN.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.83-89
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• 2020

A microstrip feedline based open ended folded-slot antenna is proposed for ultra-wideband (UWB) applications. The prototype of the proposed antenna is fabricated on the FR4 dielectric substrate. The proposed antenna has a wide n-shaped slot that is useful for designing circuit components on the same printed circuit board (PCB) as that of the radio frequency (RF) modules. The proposed antenna use two kinds of slots as radiators, and each slots have different characteristics because of the different type of ends of the slot. The wideband characteristic can be obtained by resonances of each slot which are occurred at different frequencies. The measured impedance bandwidth (S₁₁≤ -10 dB) is 2.9-11.56 GHz, and the antenna peak gain is 2-4 dBi over the UWB range. The antenna has a stable omni-directional radiation pattern and only a small group-delay variation across the UWB passband. In addition, we present a modified design with band-notched characteristics of a 5 GHz wireless local area network (WLAN) frequency band.

• Journal of information and communication convergence engineering
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• v.15 no.4
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• pp.199-204
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• 2017

A compact dual-band half-ring-shaped (HRS) bent slot antenna fed by a coplanar waveguide for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is presented. The antenna consists of two HRS slots with different lengths and widths. The two HRS slots are connected through an arc-shaped slit, and the upper HRS slot is bent in order to reduce the size of the antenna. The optimized dual-band HRS bent slot antenna operating in the 2.45 GHz WLAN and 3.5 GHz WiMAX bands is fabricated on an FR4 substrate with dimensions of 30 mm by 30 mm. The slot length of the proposed dual-band slot antenna is reduced by 35%, compared to a conventional dual-band rectangular slot antenna. Experimental results show that the proposed antenna operates in the frequency bands of 2.40-2.49 GHz and 3.39-3.72 GHz for a voltage standing wave ratio of less than 2, and measured gain is larger than 1.4 dBi in the two bands.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.42-52
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• 1998

This paper proposes an extended TCP/IP protocol, LAN/TCP, that can be used for the distributed soft real-time systems connected through the Ethernet-based local area network. Since LAN/TCP shows soft real-time performance with keeping compatibility and interoperability with the standard TCP/IP, the existing application software can be used without any modification. LAN/TCP also provides the periodic transmission mode(PTM) with which the periodical data collection and updating the control signals can be efficiently implemented with relatively small traffic overhead. This paper includes the computer simulation and experimental results of the proposed protocol.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.1
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• pp.74-80
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• 2010

We implemented an application system which is able to verify visitor identification for remote bundle control based on OSGi and web camera control using embedded linux system. This system are designed open Oscar framework by porting java on the embedded linux system and implemented web camera system in local area networks. Also This system can verify information of visitor from receiving the data of RFID reader and designed the wireless internet system in home. Basically, in this paper we expect that home network system development and the period of application service development are reduced with integrated service provision based on OSGi.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.227-231
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• 2007

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication and ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.