• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.114-120
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• 2013

Recently, navigation systems based on wireless communication have been applied to the internal structures such as building or ship. If a stable azimuth information is obtained, these systems can effectively guide the direction of the user's progress through the information and then can improve the performance of guidance. Since conventional method which has acquired an azimuth information using geomagnetic and acceleration sensor(azimuth sensor hereafter) is sensitive to the effects of the magnetic field, it has unstable error range according to the surrounding environment. In order to improve these problems, this paper presents a new relative azimuth estimation algorithm using the displacement of a mobile node and its rotation angle based on Wireless communication. For the performance assessment of the proposed algorithm, experiments using rotating arm are performed and the results are confirmed that the proposed system can estimate the relative azimuth without using additional sensors.

• Journal of Korea Multimedia Society
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• v.14 no.9
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• pp.1152-1164
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• 2011

Stock price is stream data to change continuously. The characteristics of these data, stock trends according to flow of time intervals may differ. therefore, stock price should be continuously prediction when the price is updated. In this paper, we propose the new prediction system that continuously predicts the stock price according to the predefined time intervals for the selected stock item using HTM model. We first present a preprocessor which normalizes the stock data and passes its result to the stream sensor. We next present a stream sensor which efficiently processes the continuous input. In addition, we devise a storage node which stores the prediction results for each level and passes it to next upper level and present the HTM network for prediction using these nodes. We show experimented our system using the actual stock price and shows its performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1939-1946
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• 2012

USNs (Ubiquitous Sensor Networks) such as IEEE 802.15.4 ZigBee network share ISM (Industrial, Scientific, and Medical) frequency band with WiFi networks. Once both networks operate in a region, packet collision may happen because of frequency overlapping. To assure this possibility, we conducted experiments where WiFi and ZigBee communication networks had been installed in an area. As a result of the test, successful data transmission rate were reduced due to the frequency overlapping between a WiFi communication channel and a ZigBee communication band. To cope with this problem, we propose a collision avoidance algorithm. In the proposed algorithm, if frequency collision is sensed, new communication channel with different frequency band is allocated to each node. Performance of the proposed frequency collision avoidance algorithm was tested and the results were described.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.615-620
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• 2009

Nowadays, wireless infrastructures such as sensor networks are widely used in many different areas. In case of sensor networks, the wirelessly connected sensors can execute different kind of tasks in a diversity of environments, and one of the most important parameter for a successful execution of such tasks is the location information of each node. As to localization problems in WSNs, there are ToA (Timer of Arrival), RSS (Received Signal Strength), AoA (Angle of Arrival), etc. In this paper, we propose a modification of existing ToA and RSS based methods, adding a weighted average scheme to measure more precisely the distance between nodes. The comparison experiments with the traditional ToA method show that the average error value of proposed method is reduced by 0.1 cm in indoor environment ($5m{\times}7m$) and 0.6cm in outdoor environment ($10{\times}10m$).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.887-898
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• 2009

Conventional routing protocols proposed for wireless sensor networks (WSNs) cannot fully accommodate the characteristics of WSNs. In particular, although it is possible to largely obtain benefits in the solution of energy consumption and global identification problems through applying position information, there are few protocols that actively apply such position information. In the case of geographical and energy aware routing (GEAR) that is a typical algorithm, which uses position information, it does not fully represent the characteristics of WSNs because it is limited to forward query messages and assumed as fixed network environments. The routing protocols proposed in this paper defines the direction of data, which is routed based on the position information of individual and target nodes, in which each node configures its next hop based on this direction and routes signals. Because it performs data-centric routing using position information, it does not require certain global identifications in order to verify individual nodes and is able to avoid unnecessary energy consumption due to the forwarding of packets by defining its direction.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2736-2744
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• 2013

In this paper, we present a Smart Water Treatment Plant using Zigbee USN devices and a real-time monitoring system in K-water Flow Meter Calibration Center Building. For verification, the data of vertical type WTP such as flow rate, pressure, water level and water temperature are obtained by the Zigbee USN devices, operating in 2.45 GHz band, and be wirelessly surveilled by the real-time monitoring system. The received data from the sensor is transmitted to the data processing device, and then the processed data can be monitored on a smart phone. Consequently, the pilot plant based on the low-cost and high-efficiency USN has been developed with the performance analysis for the communication network and remote monitoring system on mobile devices.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.506-514
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• 2009

To minimize energy consumption, most of MAC Protocols in WSNs exploit low duty cycling. Among those, RMAC [4] allows a node to transmit a data packet for multiple hops in a single duty cycle, which is made possible by exploiting a control frame named Pioneer (PION) in setting up the path. In this paper, we present a MAC Protocol called Hop Extended MAC (HE-MAC) that transmits the data packet for more multiple hops in a single duty cycle. It employs an EXP (Explorer) frame to set up the multiple hop transmission, which contains the information of the maximum hop that a packet can be transmitted. With the use of the information in EXP and an internal state of Ready to Receive (RTR), HEMAC extends the relay of the packet beyond the termination of the data period by two more hops compared to RMAC. Along with our proposed adaptive sleeping method, it also reduces power consumption and handles heavy traffic efficiently without experiencing packet inversion observed in RMAC. We analytically obtain the packet delivery latency in HE-MAC and evaluate the performance through ns-2 simulations. Compared to RMAC, HE-MAC achieves 14% less power consumption and 20% less packet delay on average for a random topology of 300 nodes.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.4
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• pp.32-38
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• 2011

This paper describes implementation of the 5.0GHz RF frequency synthesizer with 0.18${\mu}m$ silicon CMOS technology being used as an application of the IEEE802.15.4 USN sensor node transceiver modules. To get good performance of speed and noise, design of the each module like VCO, prescaler, 1/N divider, fractional divider with ${\Sigma}-{\Delta}$ modulator, and common circuits of the PLL has been optimized. Especially to get excellent performance of high speed and wide tuning range, N-P MOS core structure and 12 step cap banks have been used in design of the VCO. The chip area including pads for testing is $1.1{\times}0.7mm^2$, and the chip area only core for IP in SoC is $1.0{\times}0.4mm^2$. Through analysing of the fabricated frequency synthesizer, we can see that it has wide operation range and excellent frequency characteristics.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.12
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• pp.13-22
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• 1998

In this paper, we propose a high-performance BICS(built-in current sensor) which is fabricated in 0.8${\mu}{\textrm}{m}$ single-poly two-metal process for IDDQ testing of CMOS VLSI circuit. The CUT(circuit under test) is 4-bit full adder with a bridging fault. Using two nMOSs that have different size, two bridging faults that have different resistance values are injected in the CUT. And controlling a gate node, we experimented various fault effects. The proposed BICS detects the faulty current at the end of the clock period, therefore it can test a CUT that has a much longer critical propagation delay time and larger area than conventional BICSs. As expected in the HSPICE simulation, experimental results of fabricated chip demonstrated that the proposed BICS can exactly detect bridging faults in the circuit.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.5
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• pp.49-54
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• 2009

This paper describes implementation of the 1.9GHz RF frequency synthesizer with $0.18{\mu}m$ silicon CMOS technology being used as an application of the USN sensor node transceiver modules. To get good performance of speed and noise, design of the each module like VCO, prescaler, 1/N divider, fractional divider with ${\Sigma }-{\Delta}$ modulator, and common circuits of the PLL has been optimized. Especially to get good performance of speed, power consumption, and wide tuning range, N-P MOS core structure has been used in design of the VCO. The chip area including pads for testing is $1.2{\times}0.7mm^2$, and the chip area only core for IP in SoC is $1.1{\times}0.4mm^2$. The test results show that there is no special spurs except -63.06dB of the 6MHz reference spurs in the PLL circuitry. There is good phase noise performance like -116.17dBc/Hz in 1MHz offset frequency.