• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.512-522
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• 1996

To provide broadband ISDN service for the users in scattered locations, the application of satellite communications network is seriously considered. To trans mit ATM cells efficiently in satellite communications, it is effective to use TDM A method. However, it is necessary to have a method to compensate the cell delayvari-ation caused by the difference between TDMA and ATM. This paper optimized the cell control time(Tc) when traffic inputs have poisson or markov modulated poisson process by applying cell delay variation characteristics of time stamp method, which has the most advantages among compensation methods or cell delay variation. This paper also intorduces a method of reducing the cell clumping phenomena by adapting discrete time stamp method, including the analysis and evalutation of the range of required quality of CDV distribution by ATM transmission.The result of the experiment shows that CDV distribution-range can be controlled to 1.2$\times$Tc which reduces overall cell delay variation by discrrete time stamp method.

• Journal of Korean Society of Transportation
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• v.22 no.6
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• pp.7-16
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• 2004

In mode choice decision, travelers consider not only travel time but also reliability of its modes. In this paper, reliability was expressed in terms of standard deviation and maximum delay that were measured based on triangular distribution. In order to estimate value of time and value of reliability, the Multinomial and Nested Logit models were used. The analysis results revealed that reliability is an important factor affecting mode choice decisions. Elasticity is used to estimate the impacts of the different policies and system improvements for water transportation mode. Among these policies, decision maker can assess and select the best alternative by doing the benefit and cost analysis based on a new market share, the value of time, and the value of reliability. Finally, a set of promising policies and system improvement of the water transportation were proposed.

• Smart Structures and Systems
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• v.31 no.3
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• pp.259-273
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• 2023

Real-time hybrid simulation (RTHS) is an effective experimental technique for structural dynamic assessment. However, time delay causes displacement de-synchronization at the interface between the numerical and physical substructures, negatively affecting the accuracy and stability of RTHS. To this end, the authors have proposed a model-based adaptive control strategy with a Kalman filter (MAC-KF). In the proposed method, the time delay is mainly mitigated by a parameterized feedforward controller, which is designed using the discrete inverse model of the control plant and adjusted using the KF based on the displacement command and measurement. A feedback controller is employed to improve the robustness of the controller. The objective of this study is to further validate the power of dealing with a nonlinear control plant and to investigate the potential challenges of the proposed method through actual experiments. In particular, the effect of the order of the feedforward controller on tracking performance was numerically investigated using a nonlinear control plant; a series of actual RTHS of a frame structure equipped with a magnetorheological damper was performed using the proposed method. The findings reveal significant improvement in tracking accuracy, demonstrating that the proposed method effectively suppresses the time delay in RTHS. In addition, the parameters of the control plant are timely updated, indicating that it is feasible to estimate the control plant parameter by KF. The order of the feedforward controller has a limited effect on the control performance of the MAC-KF method, and the feedback controller is beneficial to promote the accuracy of RTHS.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.295-304
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• 1996

Toprovide economical BISDN service, with which integration process of many types of media is possible, it is necessary to construct a system with ground network and satellite network combined. The method for this type of transmission using satellite is TDMA that can provide services to many users in various area. However, the most difficult task to connect TDMA which uses synchronous method to ATM which used asynchronous transfer mode is the deterioration n of ATM transmission quality such as cell delay variation. Therefore, it is necessary to develop delay variation compensation method which can confront to the ATM. Efficient ways to use satellite links under the conditions such that maximum efficiency of the delay variation is limited under the required value, and the burst characteristic of transmission cell does not increase are being researched for translation between in ATM and TDMA. This paper points out the problems when time stamp method, reviewd in ground network, is applied to the satellite links to compensate the delay variation .To solve the problem, discrete cell count method is introduced along with the calculation of transmission capacity and error rate.Also, from the observation of stab-ility of the system and verification of reliability even when singal error occurred in the cell transmission timing information, the proposed compensation method appeared to be excellent.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.777-784
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• 2010

Recently, the necessity of underwater communication and demand for transmitting and receiving various data such as voice or high resolution image data are increasing as well. The performance of underwater acoustic communication system is influenced by characteristics of the underwater communication channels. Especially, ISI(inter symbol interference) occurs because of delay spread according to multi-path and communication performance is degraded. In this paper, we study the OFDM technique to overcome the delay spread in underwater channel and by using CP, we compensate for delay spread. But PAPR which OFDM system has problem is very high. Therefore, we use DFT-spread OFDM method to avoid nonlinear distortion by high PAPR and to improve efficiency of amplifier. DFT-spread OFDM technique obtains high PAPR reduction effect because of each parallel data loads to all subcarrier by DFT spread processing before IFFT. In this paper, we show performance about delay spread through OFDM system and verify method that DFT spread OFDM is more suitable than OFDM for underwater communication. And we analyze performance according to two subcarrier mapping methods(Interleaved, Localized). Through the simulation results, performance of DFT spread OFDM is better about 5~6dB at $10^{-4}$ than OFDM. When compared to BER according to subcarrier mapping, Interleaved method is better about 3.5dB at $10^{-4}$ than Localized method.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.141-144
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• 2000

PRML (partial response maximum-likelihood) 과 FDTS/DF (fixed-delay tree search with decision feedback)는 기록 저장 시스템에서 준최적의 성능을 보임이 잘 알려져 있다. 그러나, 위와 같은 정보열 검출 기법은 피할 수 없는 복잡도 문제를 가지고 있다. 본 논문은 최소 run 길이 제한조건 d=2를 가진 광기록 채널을 위한 다양한 저복잡도 검출 기법을 다룬다. 우선, 결정 궤환 기법을 이용한 이산 정합 여파기 (discrete matched filter with decision feedback：DMF/DF)가 기존의 PRML로부터 유도된다. 유도된 시스템은 PRML보다 결정 궤환에 의한 성능 이득을 갖는다. 또한, 메트릭 계산을 사용하지 않는 저복잡도 FDTS/DF가 유도된다. 모의실험 결과에 의하면, 유도된 저복잡도 검출 기법들은 기록 밀도 S>=5.5에서 P(D)=1+D+D/sup 2/+D/sup 3/의 target을 갖는 PRML보다 우수한 성능을 보인다.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.3
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• pp.199-206
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• 2016

This paper describes a simple routing control system. We propose achieving high-speed data transmission without modifying the data frame configuration. To add a routing control signal, called the "labeling signal" in this paper, to the data frame, we use a frequency modulation technique on the transmitted frame. This means you need not change the data frame when you transmit additional signals. Using a prototype system comprising a field-programmable gate array and discrete elements, we investigate the system performance and devise a method to achieve high resolution. A three-channel routing control for a 10 Gb/s data frame was achieved, which confirms the advantages of the proposed system.

• Journal of Power Electronics
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• v.17 no.2
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• pp.389-397
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• 2017

A control scheme for stand-alone inverters that utilizes an inductor current observer (ICO) is proposed. The proposed method measures disturbance load currents using a current sensor and it estimates the inductor current using the ICO. The filter parameter mismatch effect is analyzed to confirm the ICO's controllability. The ICO and controllers are designed in a continuous-time domain and transferred to a discrete-time domain with a digital delay. Experimental results demonstrate the effectiveness of the ICO using a 5-kVA single-phase stand-alone inverter prototype. The experimental results demonstrate that the observed current matches the actual current and that the proposed method can archive a less than 2.4% total harmonic distortion (THD) sinusoidal output waveform under nonlinear load conditions.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.375-379
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• 1990

A microprocessor-based multi-function switchgear for the protection, measurement and control of the power system is presented. For the extraction of the RMS values of the fundamental components of current and voltage signals, a simple digital filter based on cross-correlation of the distorted signal with even and odd heptagonal waves is used. The frequency response of this filter is almost identical to that of the filter based on the discrete fourier transform, while its computational requirement is far less. For the time delay element relaying, a new log-table based relaying algorithm is suggested. The suggested use of the heptagonal wave cross-correlation digital filter algorithm and a new relaying algorithm reduce the computational needs so drastically that all functions of the switchgear can be implemented on the microprocessor system. Real time testing of the implemented daboratory prototype show good practical response under different operating conditions.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.378-384
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• 1993

In this paper, an intelligent adaptive controller is proposed for the process with unmodelled dynamics. The intelligent adaptive controller consists of the numeric adaptive controller and the intelligent tuning part. The continuous scheme is used for the numeric adaptive controller to avoid the problems occurred in the discrete time schemes. The adaptive controller is adopted to the process with time delay. It is an implicit adaptive algorithm based on GMV using the emulator. The tuning part changes the design parameters in the control algorithm. It is a multilayer neural network trained by robustness analysis data. The proposed method can improve the robustness of the adaptive control system because the design parameters are tuned according to the operating points of the process. Through the simulation, robustnesses are shown for intelligent adaptive controller. Finally, the proposed algorithms are implemented on the electric furnace temperature control system. The effectiveness of the proposed algorithm is shown from experiments.