• Journal of Service Research and Studies
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• v.2 no.1
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• pp.61-68
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• 2012

Much technologies building cloud computing environment and supporting sevices on the cloud computing have been developing. Through the environment, accessing new services and sharing knowledge become easy. So far, they have just focused on companies which can support services and people who can use those services. In other words, the environment and models for cloud computing are the most important issue. However, the environment changes rapidly, mobile devices that are connected with each other not only will replace the computing environment based on desktop, but also can create Big data. Therefore, technologies and models are need to follow the trend including mobile based cloud computing environment. In this paper, we explain the cloud computing technologies and trend. Also we address Machine to Machine(M2M) technology and Web of things(WoT) in order to apply those into the cloud computing environment because these two concepts will enhance effectiveness and service reusability in the coming days.

• Journal of Internet Computing and Services
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• v.15 no.3
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• pp.63-69
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• 2014

For the safety messages in IEEE 802.11p vehicles network environment(WAVE), strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. WAVE standards apply multiple radios and multiple channels to provide open public road safety services and improve the comfort and efficiency of driving. Although WAVE standards have been proposed multi-channel multi-radio, the standards neither consider the WAVE multi-radio environment nor its effect on the beacon broadcasting. Most of beacon broadcasting is designed to be delivered on only one physical device and one control channel by the WAVE standard. also conflict-free channel assignment of the fewest channels to a given set of radio nodes without causing collision is NP-hard, even with the knowledge of the network topology and all nodes have the same transmission radio. Based on the latest standard IEEE 802.11p and IEEE 1609.4, this paper proposes an interference aware-based channel assignment algorithm with Nash bargaining solution that minimizes interference and increases throughput with wireless mesh network, which is deigned for multi-radio multi-cahnnel structure of WAVE. The proposed algorithm is validated against numerical simulation results and results show that our proposed algorithm is improvements on 8 channels with 3 radios compared to Tabu and random channel allocation algorithm.

• Korean Journal of Environment and Ecology
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• v.24 no.4
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• pp.487-492
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• 2010

This study was conducted to analyze the home range size of Pipistrellus abramus in non-reproductive season. The survey was conducted in the day-roosting site of Pipistrellus abramus located in Gyeongju City(North Gyeongsang Province). We radio-tracked six Pipistrellus abramus(male 3, female 3) and LTM single stage radio transmitter(0.38g), R2000 ATS receiver, three element yagi antenna, roof mounted antenna and ArcGIS 3.3(ESRI, Animal Movement Extension 2.0) were used to locate bats and home range analyze. The home range sizes of the 6 radio-tracked Pipistrellus abramus ranged from 8.97 to 19.07ha(Maen $14.46{\pm}3.44ha$). Mean home range size of female($16.83{\pm}1.96ha$) was larger than that of male($12.08{\pm}2.96ha$) but there were no significant differences in home range sizes between male and female(t=2.32, p>0.05). Also, mean maximum distances from the roost was $468.73{\pm}94.38m$ but there were no significant differences between sexes(female, $422.73{\pm}10.38m$; male, $514.74{\pm}125.74m$; t=-1.26, p>0.05).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1349-1358
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• 2009

Because of the limitation of supporting power, the current WSN(Wireless Sensor Network) Technologies whose one of the core attributes is low power consumption are the best solution for shipping container networking in stack environment such as on vessel. So it is effective to use the Wireless Sensor Network Technology. In this case, many nodes join in the network through a sink node because there are difficulties to get big money and efforts to set up a lot of sink node. It needs clustering-based proactive protocol to manage many nodes. But it shows low reliability because they have effect on radio frequency in metal obstacle environments(interference, distortion, reflection, and etc) like the intelligent container. In this paper, we proposed an improved Modified LEACH Protocol for stableness radio frequency environment. In the proposed protocol, we tried to join the network and derived stable topology composition after the measuring of link quality. Finally, we verified that the proposed protocol is composing more stable topology than previously protocol in metal obstacle environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9C
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• pp.826-833
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• 2007

In this paper, we present an adaptive transmission system model to establish the baseline for wireless adaptive transmission using CR (Cognitive Radio) systems, and propose an adaptive transmission scheme based on IT (Interference Temperature) cognition for CR systems in the presented system environment. The proposed CR adaptive transmission scheme is the method that provides the CR user with the maximum transmit power in the range of not causing any interference to the incumbent user and guaranteeing the optimal throughput by applying CR-AMC (CR-Adaptive Modulation and Coding) in the given channel state. Simulation results show that in case of using the proposed CR adaptive transmission scheme, there is little degradation of BER performance, while causing no interference to the incumbent user. At the same time, the proposed scheme guarantees the optimal throughput to the CR user in the given channel state.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.677-687
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• 2008

CR technology is an intelligent technology which can sense the spectrum environment an adaptively adjust the parameters for wireless transmission. In this paper, by using CR-UWB, the spectrum efficiency of the transmission channel is largely improved; Furthermore, the interference to other system can be effectively avoided. In this paper, we propose a solution on interference problem of UWB system using cognitive radio. We use interference temperature model of cognitive radio that has proposed by FCC for estimating interference signal. Calculating channel capacity of UWB system with interference temperature, we suggest how to solve interference problem. We have used genetic algorithm in cognitive engine's calculation precess. The proposed UWB System with cognitive radio shows very efficient in solving interference problem.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.178-203
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• 2018

In this paper, authors have been evaluated the Frame Error Rate (FER) performance of IEEE 802.11 a/g/p standard 5 GHz frequency band WLAN over Rayleigh and Rician distributed fading channels in presence of Additive White Gaussian Noise (AWGN). Orthogonal Frequency Division Multiplexing (OFDM) based transceiver is implemented by using real-time signal processing frameworks (IEEE 802.11 Blocks) in GNU Radio Companion (GRC) and Ettus USRP N200 is used to process the symbol over the wireless radio channel. The FER is calculated for each sub-carrier conventional modulation schemes used by OFDM such as BPSK, QPSK, 16, 64-QAM with different punctuated coding rates. More precise SNR is computed by modifying the SNR calculation process of YANS and NIST error rate model to estimate more accurate FER. Here, real-time signal constellations, OFDM signal spectrums etc. are also observed to find the effect of multipath propagation of signals through flat and frequency selective fading channels. To reduce the error rate due to the multipath fading effect and Doppler shifting, channel estimation (CE) and equalization techniques such as Least Square (LS) and training based adaptive Least Mean Square (LMS) algorithm are applied in the receiver. The simulation work is practically verified at GRC by turning into a pair of Software Define Radio (SDR) as a simultaneous transceiver.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.121-128
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• 2004

As the first step of the real time monitoring system of the solar radio disturbance, we constructed the control system of the solar radio telescope. An 1.8m antenna built by Korean Astronomy Observatory has been used, and the observed radio flux is transformed to the digital signal by the powermeter. We have also developed a computer program CBNUART in order to control the telescope system and the powermeter. As the sun rises, the telescope begins to observe the sun, and ends the observation automatically at sunset. The CBNUART enables the telescope automatically to go to the position of the sunrise for the beginning the observation and come back to the setposition after the ending the observation at the sunset. An active tracking routine is adopted in order to improve the tracking accuracy of the control system, and we used an optical telescope equipped in front of the antenna for control test. The tracking test shows that our control system can track with the accuracy of arc seconds, and the 50 minute pointing test shows that the pointing accuracy of right ascension and declination are 1.12 and 0.08 arc minutes respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.4
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• pp.229-234
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• 2017

In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) and hexamethylenetetramine ($(CH_2)6N_4$). When 15 ppm of NO gas was supplied in a gas chamber at $150^{\circ}C$ to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.10
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• pp.977-985
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• 2012

Recently, many countries have been developing new protocols to improve the performance of tactical ad hoc networks for implementing NCW (Network Centric Warfare). Combat net radio (CNR) networks are the most important communication infra for the ground forces such as infantry of Army. U.S. Army had developed MIL-STD-188-220D that is the Interoperability Standard for DMTDs (Digital Messages Transfer Device Subsystems) for voice and data communication in CNR. MIL-STD-188-220D is a candidate for MAC protocol of TMMR which is next radio and has a few constraints to used in TMMR. NAD (Network Access Delay) defined in MIL-STD-188-220D needs time synchronization to avoid collision. However, it is difficult for time synchronization to fit in multi-hop environment. We suggest the enhanced DAP (Deterministic Adaptable Priority)-NAD to prevent conflicts and decrease delays in multi-hop CNR. Simulation results show that the proposed scheme improves the performance in multi-hop CNR networks.