• Journal of KIISE
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• v.43 no.11
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• pp.1223-1232
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• 2016

A virtual network technology can provide a network reflecting the requirements of various services. The virtual network can distribute resources of the physical network to each virtual slice. An efficient resource distribution technique is needed to reflect the requirements of various services. Existing bandwidth distribution techniques can only control downlink traffic without taking traffic conditions on the network into account. Downlink and uplink share the same resources in a wireless network. The existing bandwidth distribution techniques assumed that all stations generate saturated traffic. Therefore, the existing bandwidth distribution technique cannot make traffic isolation in a virtual wireless network. In this paper, we proposed a traffic-based bandwidth control techniques to solve these problems. We applied Software-Defined Networking(SDN) to the virtual wireless network, monitored the traffic at each station, and searched for stations that generated unsaturated traffic. We also controlled both uplink and downlink traffics dynamically based on monitoring information. Our system can be implemented with legasy 802.11 clients and SDN-enabled APs. After the actual test bed configuration, it was compared to existing techniques. As a result, the distribution performance of the proposed technique was improved by 14% in maximum.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.741-746
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• 2015

Recently, as mobile operating system market and wireless communication technology have been rapidly developed, many devices such as smart phones, air conditioners, smart TVs, cleaning robot, and cameras become available with android operating system. Accordingly, collecting variety of information through many everyday use devices with network connections is now enabled. However, in the current market, most devices are controlled individually developed applications, and there is growing need to develop a master application that can control multiple devices. In this paper, we propose and implement a system that can control multiple android-based devices on a Wired/Wireless router(AP) registered through web server. we expect such an effort can attribute to future IoT researches.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.107-114
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• 2020

A power amplifier of 2.4 GHz ISM band is designed to implement a transmitter system. High efficiency amplifiers can be implemented as class E or class F amplifiers. This study has designed a 20 W high efficiency class E amplifier that has simple circuit structure in order to utilize for the ISM band application. The impedance matching circuit was designed by class E design theory and circuit simulation. The designed amplifier has the output power of 44.2 dBm and the power added efficiency of 69% at 2.45 GHz. In order to apply 30 dBm input power to the designed power amplifier, voltage controlled oscillator (VCO) and driving amplifier have been fabricated for the input feeding circuit. The measurement of the power amplifier shows 43.2 dBm output and 65% power added efficiency. This study can be applied to the design of power amplifiers for various wireless communication systems such as wireless power transfer, radio jamming device and high power transmitter.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.51-56
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• 2012

Nowadays, For that reason, the tactical training system that were applied to recruit training center and police training, a real-life survivor game place is a drill using conventional training methods that there is no special training system at open terrain and field, there is no training accomplishment in conformity with battlefield situation portrayal. Therefore, this paper developed the tactical training evaluation system and real-time monitoring system that is compensated the defect and controlled sensing, interlock with PC as wireless a way of GUI using PCB mounted MICOM. This system evaluate drill that regulate sensor control module, tactical training system remotely according to what they should do, is installed to fit the occasion as to be reflected or transmission choosingly and is a 24V H/W drive module.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.4
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• pp.34-42
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• 2012

In this paper, a wide-input range CMOS multi-mode rectifier for wireless power transfer system is presented. The output voltage of multi-mode rectifier is sensed by comparator and switches are controlled based on it. The mode of multi-mode rectifier is automatically selected by the switches among full-wave rectifier, 1-stage voltage multiplier and 2-stage voltage multiplier. In full-wave rectifier mode, the rectified output DC voltage ranges from 9 V to 19 V for a input AC voltage from 10 V to 20 V. However, the input-range of the multi-mode rectifier is more improved than that of the conventional full-wave rectifier by 5V, so the rectified output DC voltage ranges from 7.5 V to 19 V for a input AC voltage from 5 V to 20 V. The power conversion efficiency of the multi-mode rectifier is 94 % in full-wave rectifier mode. The proposed multi-mode rectifier is fabricated in a $0.35{\mu}m$ CMOS process with an active area of $2500{\mu}m{\times}1750{\mu}m$.

• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.33-42
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• 2011

In this paper we designed and implemented a wireless communication circuit which can control the remote devices integrating RFID and ZigBee. This system unifies transmit part and receive part. And this system recognizes RFID tag data, then the recognized information is controlled by MCU, and transmitted to a remote device through the ZigBee. This is operated on TinyOS. If this system is applied to a entrance security system, it can permit/deny one's entrance as well as control the personal computer or other electronic devices. Our experiment shows the result of the recognized data transmission is very different according to a opened playground and a closed place. The data transmission time is stable in the indoor and the data transmission distance is long in the outdoor. We anticipate that our system be applied the various office oriented domains by connecting to the Wired LAN or the WLAN of IEEE 802.11x category.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.186-192
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• 2014

This study presents the remote control of a board robot using an IMU sensor based on Bluetooth communication. The board robot is a kind of riding robot controlled throng wireless communication by a user. The user wears the proposed IMU sensor controller, and changes a direction of the robot by the angles of IMU sensor. Bluetooth is used for wireless communication between the board robot and its user. The IMU sensor in the remote controller is used for recognition of a number of actions, which are measured as analog signals. The user actions have five commands ('1'right '2'neutrality '3'left '4'operation '5'stop), which are transmitted from the user to the board robot through Bluetooth communication. Experimental results show that proposed IMU interface can effectively control the board robot.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.27-34
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• 2012

In this paper, Coplanar waveguide(CPW)-fed slot loop antenna, which is applicable to the dual band(2.4GHz~2.4835GHz, 5.15GHz~5.825GHz) for the wireless LAN, is proposed. In order to miniaturize the proposed antenna, slot loop is bent by meandering. The resonant frequencies in the required dual band are adjusted by variation of the resonant length of slot loop as well as slot width. In particular, use of capacitive coupling CPW feed provides impedance matching without a seperate matching circuit, because the amount of electromagnetic coupling can be controlled by the offset between feed and radiator. As a result, it has been observed that the proposed antenna satisfies not only the required return loss(${\leq}10dB$) but also has high efficiency(${\geq}80%$) over the whole frequency band. In order to check the validity of the proposed antenna, some simulated results for return loss and radiation pattern are presented in comparison with the measured results.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2179-2187
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• 1999

To privide multimedia mobile communication services for the users in scattered locations, the application ATM cells efficiently in wireless communications, it is effective to the use TDMA method. However, it is necessary to have methods to compensate the CDV(cell delay variation) caused by the difference between TDMA-ATM and cell stream multiplexing of the users. This paper optimizes the cell control time(Tc) when VBR traffic inputs have MMPP by applying CDV characteristics of time stamp method, which has the most advantages among compensation methods of CDV. This paper suggests a cell stream multiplex method employing time stamp techniques to reduce CDV for wireless suggest method shows that CDV distribution and cell stream multiples rangd can be controlled to 1.2${\times}$Tc which reduced over the VBR service in the TDMA-WATM transmission. This paper also presents evaluation of the suggested architecture obtained simulation.

• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.105-114
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• 2007

In sensor network processing environments, current location tracking methods have problems in accuracy on receiving the transmitted data and pinpointing the exact locations depending on the applied methods, and also have limitations on decision making and monitoring the situations because of the lack of considering context-awareness. In order to overcome such limitations, we proposed a method which utilized context-awareness in a data processing module which tracks a location of the magnetic object(Magnetic Line Tracer) and controlled introspection data based on magnetic sensor. Also, in order to prove its effectiveness we have built a wireless sensor network test-bed and conducted various location tracking experiments of line tracer using the data and resulted in processing of context-aware data. Using the new data, we have analyzed the effectiveness of the proposed method for locating the information database entries and for controlling the route of line tracer depending on context-awareness.