• Journal of Internet Computing and Services
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• v.15 no.1
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• pp.179-191
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• 2014

In this paper, a frame transmission method to make IEEE 802.15.4 nodes run at a new channel and its characteristics are studied when they experience difficulties in transmission of frames due to WiFi traffic. The researches on evaluating the interference from WiFi traffic, searching for a new channel with little interference or not, and changing the operating channel are analyzed. In an wireless channel overlapped with IEEE 802.11 network, the transmission delay of IEEE 802.15.4 frames, the collision of frames in sending IEEE 802.15.4 frames without applying CSMA-CA algorithm, and the operation of IEEE 802.11 nodes are explained. A transmission method of frames including frame-formated code blocks in order to use the rest part of collided IEEE 802.15.4 frame is proposed. In the experiments of the proposed method, it is observed that frame-formated code blocks are synchronized and received by receivers in case of collision, and then the collided positions in IEEE 802.15.4 frame and the characteristics of frame reception rate are analyzed. The experimental results show that the performance of the proposed method is improved in comparison to an existing method when we measure the time taken to send a channel change command and get the response in order to avoid the interference from WiFi traffic.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.1
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• pp.24-36
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• 2003

The digital mobile communication will be developed till getting multimedia service in anyone, any where, any time. Theses requiring items are going to be come true via IMT-2000 system. Transmitting signal bandwidth of IMT-2000 system is 3 times as large as IS-95 system. That is mean peak to average of signal is higher than IS-95A system. So we have to design it carefully not to effect in adjacent channel. HPA(High Power Amplifier) located in the end point of system is operated in 1-㏈ compression point(Pl㏈), then it generates 3rd and 5th inter modulation signals. Theses signals affect at adjacent channel and RF signal is distorted by compressed signal which is operated near by Pl㏈ point. Then the most important design factor is how we make HPA having high linearity. Feedback, Pre-distorter and Feed-forward methods are presented to solve theses problems. Feed-forward of these methods is having excellent improving capacity, but composed with complex structure. Generally, Linearity and Efficiency in power amplifier operate in the contrary, then it is difficult for us to find optimal operating point. In this paper we applied algorithm which searches optimal point of linear characteristics, which is key in Power Amplifier, using minimum current point of error amplifier in 1st loop. And we made 2nd loop compose with new structure. We confirmed fabricated LPA is operated by having high linearity and minimum current condition with ACPR of -26 ㏈m max. @ 30㎑ BW in 3.515㎒ and ACLR of 48 ㏈c max@${\pm}$㎒ from 1W to 40W.

• Journal of IKEEE
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• v.18 no.4
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• pp.471-477
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• 2014

In this paper, we propose a low-cost license plate recognition system based on smart cam system using Android. The proposed system consists of a portable device and server. Potable device Hardware consists of ARM Cortex-A9 (S5PV210) processor control unit, a power supply device, wired and wireless communication, input/output unit. We develope Linux kernel and dedicated device driver for WiFi module and camera. The license plate recognition algorithm is consisted of setting candidate plates areas with canny edge detector, extracting license plate number with Labeling, recognizing with template matching, etc. The number that is recognized by the device is transmitted to the remote server via the user mobile phone, and the server re-transfer the vehicle information in the database to the portable device. To verify the utility of the proposed system, user photographs the license plate of any vehicle in the natural environment. Confirming the recognition result, the recognition rate was 95%. The proposed system was suitable for low cost portable license plate recognition device, it enabled the stability of the system when used long time by using the Android operating system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.299-307
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• 2018

Considering a nonlinear high power amplifier(HPA) and a predistorter, we have designed a four-dimensional 8-ary phase shift keying trellis-coded modulation(4D-8PSK-TCM) system, which is recommended for X-band satellite communications. Subsequently, we have evaluated and analyzed the spectrum, constellation characteristics, and BER performance of the system. In satellite communications, owing to the limited power, nonlinear characteristics that determine the operating point of the HPA must be analyzed because the HPA consumes high power. We herein report the design of the 4D-8PSK-TCM system, with efficiencies of 2 and 2.25 bits/channel-symbol. The simulation results confirmed that a 0.35 roll-off value is effective, considering the low peak-to-average power ratio(PAPR) characteristic and the narrow occupation bandwidth of the spectrum. It also confirmed that approximately 15~20 dB of output backoff(OBO) value is required at the HPA when the predistorter is not used, and approximately 1 dB of the OBO value is required when the predistorter is used.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.63-68
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• 2017

Although automated metro subway systems have the advantage of operating a train without a train driver, it is difficult to detect an immediate fault condition and take countermeasures when an unusual situation occurs. Therefore, it is important to construct a maintenance information system (MIS) that detects the vehicle failure/status information in real time and maintains it efficiently in the depot of the railway's vehicles. This paper proposes a conceptual design method that realizes the interface between the train control system (TCS), the operation control center train control monitoring system (OCC-TCMS) console, and the MIS using wireless communication network in real-time. To transmit a large amount of information on 800,000 occurrences per day during operation, data was collected in a 56 byte data table using a data processing algorithm. This state information was classified into 4 hexadecimal codes and transmitted to the MIS by mapping the status and the fault information on the vehicle during the main line operation. Furthermore, the transmission and reception data were examined in real time between the TCS and MIS, and the implementation of the failure information screen was then displayed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.794-805
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• 2017

This paper proposes a Hardware-In-Loop(HIL) Simulator for a Wind Turbine and an operational control algorithm to evaluate the performance of a wind turbine control system. It provides not only for the validation of the control logics, safety functions and H/W failure, but also for the high reliability of the wind turbines (by reducing/and the reduction of the operating expense(OPEX) through performance evaluation tests with complex scenarios. On the other hand, the proposed simulator uses MATLAB, CODER, and the PLC library to operate in synchronization with the hardware, and a real-time processing-based wind turbine module including a dynamic model and control system, wind module, grid module and host PC to manage the HIL-simulator. Several experiments were carried out under the above concept to verify the effectiveness of the proposed WT HIL-simulator.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.34-39
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• 2001

An adaptive multi-rate (AMR) speech coder was adopted as a standard of W-CDMA by 3GPP and ETSI. The AMR coder is based on the CELP algorithm operating at rates ranging from 12.2 kbps down to 4.75 kbps, and it is a source controlled codec according to the channel error conditions and the traffic loading. In this paper, we implement the DSP S/W of the AMR coder using OakDSPCore. The implementation is based on the CSD17C00A chip developed by C&S Technology, and it is tested using test vectors, for the AMR speech codec, provided by ETSI for the bit exact implementation. The DSP B/W requires 20.6 MIPS for the encoder and 2.7 MIPS for the decoder. Memories required by the Am coder were 21.97 kwords, 6.64 kwords and 15.1 kwords for code, data sections and data ROM, respectively. Also, actual sound input/output test using microphone and speaker demonstrates its proper real-time operation without distortions or delays.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.451-462
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• 2005

Optimal Trajectory Correction Maneuver (TCM) design algorithm has been developed using the B-plane targeting method for future Korean Mars missions. For every-mission phase, trajectory informations can also be obtained using this developed algorithms which are essential to design optimal TCM strategy. The information were computed under minimum requiring perturbations to design Mars missions. Spacecraft can not be reached at designed aim point because of unexpected trajectory errors, caused by many perturbations and errors due to operating impulsive maneuvers during the cruising phase of missions. To maintain spacecraft's appropriate trajectory and deliver it to the designed aim point, B-plane targeting techniques are needed. A software NPSOL is used to solve this optimization problem, with the performance index of minimizing total amount of TCM's magnitude. And also executing time of maneuvers on be controlled for the user defined maneuver number $(1\~5)$ of TCMs. The constraints, the Mars arrival B-plane boundary conditions, are formulated for the problem. Results of this work show the ability to design and analyze overall Mars missions, from the Earth launch phase to Mars arrival phase including capture orbit status for future Korean Mars missions

• Journal of Biosystems Engineering
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• v.16 no.3
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• pp.248-262
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• 1991

Simulation model was developed to analyze drying process for tray type red pepper dryer and validated by experiments. This model could predict satisfactorily temperatures and moisture contents of red pepper and temperatures of drying air during drying. Optimize algorithm was developed to search control valiables (drying air temperature, air recycle ratio and air flow rate) of red pepper dryer based on a criterion of minimizing energy consumption under the constraint conditions that statisfied carotenoid retension of at least 210mg per 100g dry matter, the moisture content of bottom layer of 15% (d.b) and drying time of less than 35 hours. Step changes in drying air temperature and air recycle ratio were considered in the optimization. In single step in control variables, the difference of the moisture content between top layer and bottom layer was great and more fan power was required. As the drying trays were exchanged when the moisture content of bottom layer reached to 100% (d.b), fifty percent of energy was saved and the difference of moisture content was little. In double step changes in control variables, optimal conditions were found by changing the step when the moisture content of bottom layer reached to 100% (d.b) (about 19.8 hours from starting drying). Optimum air flow rate was $18.1cmm/m^2$. Optimum drying air temperature and air recycle ratio in the first step was $55.8^{\circ}C$ and 0.80, and in the second step $65.6^{\circ}C$ and 0.88, respectively. In triple step changes in control variables, the optimal conditions were found by changing the steps when the moisture content of bottom layer reached to 250% (d.b) and 150% (d.b). Optimal air temperatures were $66.2^{\circ}C$, $58.4^{\circ}C$ and $66.9^{\circ}C$, and optimal air recycle ratios were 0.778, 0.785, 0.862 at each step, respectively. Optimal air flow rate was $18.9cmm/m^2$. The best operating mode was triple step mode considering energy consumption, drying time, fan power, and quality of dried red pepper. When the triple step mode was used to dry the red pepper, the energy consumption was about 16.5%~57.2% less than that of the single step mode and the drying time was 6.6 hours shorter than that of the double step mode.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.779-793
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• 1998

In this study, for the purpose of water supply planning, we propose a sophisticated multi-period mixed integer programming model that can coordinate the behavior of multi-reservoir operation, minimizing unnecessary spill. It can simulate the system with operating rules which are self- generated by the optimization engine in the algorithm. It is an optimization model in structure, but it indeed simulates the coordinating behavior of multi-reservoir operation. It minimizes the water shortfalls in demand requirements, maintaining flood reserve volume, minimizing unnecessary spill, maximizing hydropower generation release, keeping water storage levels high for efficient hydroelectric turbine operation. This optimization model is a large scale mixed integer programming problem that consists of 3.920 integer variables and 68.658 by 132.384 node-arc incidence matrix for 28 years of data. In order to handle the enormous amount of data generated by a big mathematical model, the utilization of DBMS (data base management system)seems to be inevitable. It has been tested with the Han River multi-reservoir system in Korea, which consists of 2 large multipurpose dams and 3 hydroelectric dams. We demonstrated successfully that there is a good chance of saving substantial amount of water should it be put to use in real time with a good inflow forecasting system.