• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.333-339
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• 1997

We fabricated a sensor head which consists of spliced different-diameter fiber gratings for discrimination between strain and temperature. Because the fibers were drawn from the same preform, their temperature characteristics were the same but not for strain sensitivities which are inversely proportional to fibers cross-sectional areas. In measurement range of 0-1500$\mu$strain and 20-10$0^{\circ}C$, we could obtain, by using the matrix calculation, the unknown physical quantities within 10% of calculation error compared with the micrometer and thermocouple values. To improve the strain measurement accuracy, we suggest a new, novel method which deploys an unbalanced fiber Mach-Zehnder interferometer. This new signal processing technique converts the strain information to interference signal amplitude variation, temperature-independently. we obtained measurement accuracy nearly 80 times better than that obtainable with the conventional optical spectrum analyzer usage.

• Journal of the Korean Data and Information Science Society
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• v.22 no.3
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• pp.449-458
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• 2011

Illegal waste dumping is one of the major problems that the government agency monitoring water quality has to face. Recently government agency installed COD (chemical oxygen demand) auto-monitering machines in river. In this article we provide an outlier detection algorithm using R based on the time series intervention model that detects some outlier values among those COD time series values generated from an auto-monitering machine. Through this algorithm using R, we can achieve an automatic algorithm that does not need manual intervention in each step, and that can further be used in simulation study.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.276-283
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• 2003

Most of CDMA system algorithm must be verified by simulating the cellular system consisted of many other tier cells. But it takes long time to simulate such a huge CDMA cellular system. In this paper, we propose an effective time saving simulation scheme based on wraparound technique. And we study that how our remaining cell interference compensation method works on calculating of the total interference, SIR, outage probability, and cell capacity. We made a conclusion that by using proposed scheme, we can get the same result of maximum configuration cells with only one tier real cells and that we can minimize the simulation time.

• The Journal of the Acoustical Society of Korea
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• v.21 no.3
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• pp.230-236
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• 2002

A study on architecture of new parallel interference canceller which can be applied for reverse link of next generation mobile communication system supporting multi-rate is performed on this paper. The proposed method adopts new algorithm which can be applied for multi-rate system to reduce multiple access interference (MAI) which cause performance degradation of CDMA system and limit of channel capacity. The proposed system is evaluated by simulation results under various conditions. As a result, performance enhancement is achieved compared to existing conventional interference cancellers. Although the amount of calculation is increased, we can find that the performance is improved generally.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1643-1648
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• 2005

MIMO system takes advantage of the spatial diversity obtained by spatially separated antennas for high- performance and high-capacity broadband wireless access. In this paper, we propose Carrier Interferometry coded MIMO-OFDM system (MIMO-CI/OFDM) which provides frequency and spatial diversity. One combined diversity gains featly improve the performance of OFDM systems. To perform a performance analysis, we have used SPW platform that provides an easy tool to analyze the performance. The results show that the performance of MIMO-CI/OFDM shows an approximately 4dB gain over the MIMO-OFDM even in highly frequency selective fading channels.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.285-290
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• 2007

A wavelength-demodulation algorithm for FBG sensor is proposed by using a double-pass Mach-Zehnder interferometer. Zero-crossing points of double-passed interference signal are used to trigger the accurate $90^{\circ}C$ phase difference positions in the sensor signal, which is an essential condition in the subsequent arctangent and phase unwrapping signal processing. With the proposed method, we could efficiently measure various measurands, such as dynamic-, static-strain, and temperature, and ${\sim}8pm$ of wavelength resolution was obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6A
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• pp.601-608
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• 2011

In OFDMA(Orthogonal Frequency Division Multiple Access) based multi-hop networks, the subcarrier-pairing scheme using the SNR(Signal-to-Noise Ratio) has been proposed as the best solution. But, this scheme is not optimal in cognitive radio system, because of the power control due to the interference to the primary user. In this paper, we propose two subcarrier-pairing schemes for OFDMA based 2-hop cognitive radio systems. One is the IT(Interference channel gain) scheme considering only the interference channel gain, and the other is the CI(Channel SNR over interference channel gain) scheme considering the ratio of channel SNR to interference channel gain. The results show that the CI scheme has the best performance in which throughput is improved more than 10% in comparison with other schemes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.51-60
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• 2009

In radio frequency identification(RFID) systems, when an RFID reader uses the same or adjacent frequency with neighbor readers, the interference between the readers may occur, which causes the reader collision and errors in tag recognition. In the previous study on RFID reader anti-collision, the techniques based on Frequency Division Mutiplex(FDM) or Time Division Multiplex(TDM) are proposed. However in these paper, the problem on the condition of RFID reader-to-reader interference considering the distance between interfering readers, frequency and operating time is not define exactly. In this paper, the interference effect is analyzed through RFID reader interference model considering the TDM and FDM, and the optimization problem is defined. To solve this, genetic-resource allocation technique is proposed. Therefore the optimal resource allocation applied RFID environment faithfully is accomplished.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.321-328
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• 2006

In this study, the deformation oi wall thinning elbow is measured and the position of the internal thinning defect is found out by shearography. Shearography is an optical method which has applied to nondestructive testing (NDT) and the strain/stress and deformation analysis. This technique has the merit of the directly measuring the first derivative of displacement with sensitivity which can be adjusted by handling the tilt mirror in the interferometer. In this paper, we tested carbon steel pipe locally wall thinned and loaded internal pressure and the shearography was applied to measure the out-of-plane deformation of wall thinning elbow and to investigate the internal thinning defect of it. From the results, it was confirmed that this technique is proper to the practical application on the pipe line system with internal defect.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.35-40
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• 2007

As the mobile communication service is widely used and the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But a wireless repeater has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we propose a new varable step-size LMS algorithm which utilizes correlation between reference and error signals to adjust the step sizes, for cancelling the feedback interference signals in the WCDMA repeater under time-varying multi-path channels. The proposed algorithm was evaluated through computer simualation by being applied to the feedback canceling filter of the WCDMA repeater. The simulation results demonstrated that the proposed one is superior to the conventional ones in terms of the cancelation perormance.