• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.825-832
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• 2012

GPS signal delay that caused by dry gases and water vapor in troposphere is a main error source of GPS point positioning and it must be eliminated for precise point positioning. In this paper, we implemented to generate tropospheric delay grid map over the Korean Peninsula based on post-processing method by using the GPS permanent station network in order to determine the availability of tropospheric delay generation algorithm. GIPSY 5.0 was used for GPS data process and nationwide AWS observation network was used to calculate the amount of dry delay and wet delay separately. As the result of grid map's accuracy analysis, the RMSE between grid map data and GPS site data was 0.7mm in ZHD, 7.6mm in ZWD and 8.5mm in ZTD. After grid map accuracy analysis, we applied the calculated tropospheric delay grid map to single frequency relative positioning algorithm and analyzed the positioning accuracy enhancement. As the result, positioning accuracy was improved up to 36% in case of relative positioning of Suwon(SUWN) and Mokpo(MKPO), that the baseline distance is about 297km.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.335-342
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• 2006

As PRC linear interpolation algorithm is applied after analysed and verified in this paper, the unknown location of a user can be identified by using PRC information of multi-DGPS reference station. The PRC information of each GPS satellite is not varying rapidly, which makes it possible to assume that PRC information of each GPS satellite varies linearly. So, the PRC regeneration algorithm with linear interpolation can be applied to improve the accuracy of finding a user's location by using the various PRC information obtained from multi-DGPS reference station. The desirable PRC is made by the linear combination with the known position of multi-DGPS reference station and PRC values of a satellite using signals from multi-DGPS reference station. The RTK-GPS result was used as the reference. To test the performance of the linearly interpolated PRC regeneration algorithm, multi-channel DGPS beacon receiver was built to get a user's position more exactly by using PRC data of maritime DGPS reference station in RTCM format. At the end of this paper, the result of the quantitative analysis of the developed navigation algorithm performance is presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.2
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• pp.108-113
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• 1997

Ultrasonic testing is one of the most widely used method of nondestructive testing for pre-service inspection(PSI) & in-service inspection(ISI) in structures of bridges, power plants, chemical plants & heavy industrial fields. It is very important to estimate safety, life, quality of structures. Also, a lot of research for quantities evaluation & analyses inspection data is proceeding. But traditional portable ultrasonic flaw detector had been following disadvantages. 1) Analog ultrasonic flaw detector decreased credibility of ultrasonic test, because it is impossible for saving data & digital signal processing. 2) Stand-alone digital ultrasonic flaw detector cannot effectively evaluate received signals because of lack of its storage memory. To overcome this shortcoming, we develop the computer based ultrasonic flaw detector for nondestructive testing. It can store the received signal and effectively evaluate the signal, and then enhance the reliability of the testing results.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.557-565
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• 2018

For GNSS navigation in urban environment, a novel short delay multipath mitigation algorithm is proposed in this paper. This algorithm detects which satellite's signal is the multipath signal by using the constraint that GNSS receiver is equipped in a ground vehicle, then estimate new position after separating the measurement of that satellite. A criterion for detecting and validating the multipath signal depends on the performance grade of the GNSS receiver and the dynamics of the vehicle. In order to evaluate the proposed algorithm, the real data had been collected at the multipath environment of 4 scenarios. By post-processing the real data with both of the multipath mitigation algorithm in the receiver and the proposed algorithm, it can be checked that the position errors were less than 5 meters except the case that the number of visible satellite is lower than 5.

• Journal of Broadcast Engineering
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• v.2 no.1
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• pp.45-55
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• 1997

In this paper, we propose a fast algorithm with adaptive thresholding for the wavelet transform (WT) based blocking artifact reduction. In the fast algorithm, all processings that are equivalent to the processing in WT domain of the first and second scale are performed in spatial domain. In the adaptive thresholding, the threshold values used to classify the block boundary are selected adaptively according to each input image by using the statistical properties of the WT of the coded signal at block boundary and at block center, which can be obtained in spatial domain. Experimental results showed that the proposed fast algorithm is about 10 times faster than the WT-based algorithm. It also was found that the postprocessing with proposed adaptive thresholding yields some PSNR improvement and better subjective quality over that with nonadaptive thresholding which has best performance at high compression ratios of a certain .image, even at low compression ratios.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.3
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• pp.27-33
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• 1993

This paper presents the &tal controller for driving high frequency voltage fed PWM inverter that carrier frequency is over 2OkHz.We analyzed the conventional PWM to select a proper PWM pattern. as the result, obtained PWM pattern of the controller in which asynchronus staircase sinusoidal waveform is used as reference signal, and variable carrier ratio method was used for PWM control. The PWM controller is designed by fully digital method. Especially, Thk proposed controller is consisted of 8 bit one-chip microprocessor and digital logic. the former is for arithmetic and data processing, and the latter is for PWM pattern synthesis. Therefore, The responsibility and controllability is improved. Also, Data processing capability is improved using proper program to output modulation index with 9 bits. Circuits configuration of digital controller are made up of one chip 8051 and EPLD, and its controllability is tested by operating voltage fed inverter. Harmonics and current waveform is evaluated and analyzed for the voltage fed inverter system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.14-21
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• 2020

In order to provide confidential services between two communicating parties, block data encryption using a symmetric secret key is applied. A power analysis attack on a cryptosystem is a side channel-analysis method that can extract a secret key by measuring the power consumption traces of the crypto device. In this paper, we propose an attack model that can recover the secret key using a power analysis attack based on a deep learning convolutional neural network (CNN) algorithm. Considering that the CNN algorithm is suitable for image analysis, we particularly adopt the recurrence plot (RP) signal processing method, which transforms the one-dimensional power trace into two-dimensional data. As a result of executing the proposed CNN attack model on an XMEGA128 experimental board that implemented the AES-128 encryption algorithm, we recovered the secret key with 22.23% accuracy using raw power consumption traces, and obtained 97.93% accuracy using power traces on which we applied the RP processing method.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.299-311
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• 2012

Recently, H.264 SE(scalable extension) has become a standard of next generation multimedia service which is one source, multi-user service in the telecommunication environment of different kinds of networks and terminal equipments. But existing DRM schemes for multimedia service are not fit for H.264 SE system. Because the amount of transmitted multimedia data is changed considering network environment and terminal equipments' performance by the system, but in the existing DRM schemes, the amount of handled multimedia data are not variable according to network environment and terminal equipments' performance. In this paper, an information security scheme combined video watermarking and encryption is presented for H.264 SE. Amount of watermarks and embedding positions are calculated by the frame number of enhancement layers which are created according to the state of networks and terminal equipments. In order to minimize delayed time by video watermarking and encryption, the video data are watermarked and encrypted in the H.264 SE compression process. In the experimental results, we confirmed that proposed scheme is robust against video compression, general signal processing and geometric processing.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.369-380
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• 1996

Inductive Loop Detector(ILD) has been commonly used in collecting traffic data such as occupancy time and non-occupancy time. From the data, the traffic volume and type of passing vehicle is calculated. To provide reliable data for traffic control and plan, accuracy is required in type recognition which can be utilized to determine split of traffic signal and to provide forecasting data of queue-length for over-saturation control. In this research, a new recognition model issuggested for recognizing typeof vehicle from thecollected data obtained through ILD systems. Two clustering methods, based on statistical algorithms, and one neural network clustering method were employed to test the reliability and occuracy for the methods. In a series of experiments, it was found that the new model can greatly enhance the reliability and accuracy of type recongition rate, much higher than conventional approa-ches. The model modifies the neural network clustering method and enhances the recongition accuracy by iteratively applying the algorithm until no more unclustered data remains.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8S
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• pp.2608-2619
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• 2000

This paper proposes the Handover Scheme for the mobile and describes the result of the performance analysis. In the conventional scheme of handover request, the withdrawal of terminal may occur because handover request is performed based on fixed signal level without considering network load and terminal mobility. The proposed scheme offers the minimization of withdrawal and handover blocking probability by means of the handover request of terminal based on the network load and terminal mobility. Conventional handover scheme has the sequential procedure that network performs resource check and path rerouting on the handover by MT(Mobile Terminal). Proposed handover scheme pre-processes the resource check before the handover request by predicting the handover request timo so that handover latency can be reduced. Moreover, path optimization is executed after the completion of handover in order to reduce handover latency. The rdduction of handover latency prevents the dropping of service by minimizing backward handover blocking. In summary, we propose the prediction of handover request time and decision method based on terminal, validating the performance of proposed scheme considering various cases of simulation.