• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.572-579
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• 2010

Filtered multi-tone (FMT) is a form of multicarrier modulation utilizing frequency-domain equalization efficient in multi-path fading channels. Doppler frequency information can be employed for channel estimation and link adaptation to improve the performance. However, most previous studies have concentrated on the orthogonal frequency division multiplexing (OFDM) instead of FMT. Moreover, they have not considered the synchronization error that can commonly occur in practical systems. In this paper, we propose Doppler frequency estimation scheme that is effective in FMT systems with residual synchronization error and high noise levels.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.515-520
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• 1998

In this paper, we propose a new fault tolerant architecture for high availability systems, where for module internal operations both processor modules perform the same tasks at the same time independently of each other while for module external operations both processor modules act actively. That is, operations of synchronization between dual processor modules except clock synchronization are requested only when module external operations are executed. The architecture can not only improve system availability by reducing system reintegration time but also reduce performance degradation problem due to frequent synchronization between dual processor modules. The clock unit consists of a clock generator and a clock synchronization circuit. This supplies a stable clock signal under clock unit disorder of any processor module or rapid clock signal variation. And this architecture achieves system availability and data credibility by designing as symmetrical form.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.319-323
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• 2003

In this paper, we propose a hybrid transceiver for underwater acoustic communication, which allows the system to reduce complexity and increase robustness in time variant underwater channel environments. It is designed in the digital domain except for amplifiers and implemented by using a multiple digital signal processors (DSPs) system. The digital modulation technique is quadrature phase shift keying (QPSK) and frame synchronization is an energy (non-coherent) detection scheme based on the quadrature receiver structure. DSP implementation is based on block data parallel architecture (BDPA). We shaw experimental results in th? underwater anechoic basin at KRISO. The results indicate that the frame synchronization is performed without PLL. Also, we shaw that the adaptive equalizer can compensate frame synchronization error and the correction capability is dependent on the length of equalizer.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.4
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• pp.303-310
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• 2008

Recently, IEC 61850 supports the standardized communication technique in both station bus and process bus, and presents substation automation model. In order to implement the IEC 61850 based communication in a substation using the MU (merging unit) which is one of the important data acquisition equipments in substation automation, the time synchronization is demanded for cooperative operation between the devices. This paper proposes the precision time synchronization technique using IRIG-B protocol to develop the MU under IEC 61850 communication protocol. The proposed technique is implemented and its performance is verified experimentally.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.104-108
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• 2004

The most of the CDMA mobile communication depends on the GPS for the time synchronization. Then, we must prepare alternative system against the unusable GPS like a unexpectable accident or strategic purpose by the USA government. In this study, we have constructed ground test segment for the time synchronization system using the geostationary satellite. In addition. we have designed, manufactured and tested the transmitting and receiving board to receive 1 PPS signal from atomic clock for transmitting stored data in buffer to satellite modem and to produce 1 PPS signal from satellite modem for measuring time delay.

• Smart Structures and Systems
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• v.18 no.3
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• pp.541-568
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• 2016

The goal of this study is to investigate the effect of non-synchronous sensing when using wireless sensors on structural identification and to attempt correcting such errors in order to obtain a better identification result. The sources causing non-synchronous sensing are discussed first and the magnitudes of such synchronization errors are estimated based on time stamps of data samples collected from Imote2 sensors; next the impact of synchronization errors on power spectral densities (PSDs) and correlation functions of output responses are derived analytically; finally a new method is proposed to correct such errors. In this correction method, the corrected PSDs of output responses are estimated using non-synchronous samples based on a modified FFT. The effect of synchronization errors in the measured output responses on structural identification and the application of this correction method are demonstrated using simulation examples. The simulation results show that even small synchronization errors in the output responses can distort the identified modal and stiffness parameters remarkably while the parameters identified using the proposed correction method can achieve high accuracy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.715-718
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• 2016

SpaceWire invented for on-board data handling in a spacecraft has Time-Code defined for time synchronization over SpaceWire network. Delay and jitter of the transmission of Time-Code caused when a Time-Code travels through a network are the main reasons of time synchronization error. This work proposes a scheme that can reduce the time synchronization error by using extended Time-Codes. The proposed scheme can remove both transmission jitter and transmission delay. The scheme will be validated in a simulation environment built with OMNeT++.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.1
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• pp.3-12
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• 2001

In this paper, a synchronized stream encryption system for secure link layer communication in a radio channel is designed. Interleaving scheme which is used to enhance the transmission performance over a fading channel is applied to the encrypted information. A designed synchronous scream cipher system consists of a keystream generator, a synchronization pattern generator and a session key generator. The structure of a synchronous stream cipher system with periodic synchronization is composed of the encrypted information which consists of a synchronization pattern, an error correcting coded session key, an encrypted data in a period of synchronization. In this paper, interleaving scheme using dynamic allocation a1gorithm(DAA) is applied the encrypted information. The BER of the DAA has been slightly higher than that of the SAA(static allocation algorithm).

• Proceedings of the KSAR Conference
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• 2001.03a
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• pp.53-53
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• 2001

Two trials were conducted in a commercial dairy farm on heifer synchronization with PGF$_2$ $\alpha$. Animals showing estrus following the first injection were bred and animals not showing estrus were given the second injection 10 days later. In the first trial, the injection sites were rump and rump. In the second trial, the injection sites were rump and shoulder. Estrous detection was peformed 24 h after injection. Animals were bred by the same technician. In the first trial, the response rate for the first injection was 51.4% and the subsequent pregnancy rate of these animals was 60.0%. The response rate in the second injection was 57.1% and the pregnancy rate was 50.0%. In the second trial, the response rate in the first injection on the rump was 48.7% and the subsequent pregnancy rate was 70.6%. The second injection was given on the shoulder and the response rate was 60.0% and the subsequent pregnancy rate was 25.0%. The data suggests that the site of PGF2 $\alpha$ administration was critical to achieve success in estrous synchronization and pregnancy rates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.8
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• pp.3473-3487
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• 2020

In this paper, we present a new approach to creating speech animation with emotional expressions using a small set of example models. To generate realistic facial animation, two example models called key visemes and expressions are used for lip-synchronization and facial expressions, respectively. The key visemes represent lip shapes of phonemes such as vowels and consonants while the key expressions represent basic emotions of a face. Our approach utilizes a text-to-speech (TTS) system to create a phonetic transcript for the speech animation. Based on a phonetic transcript, a sequence of speech animation is synthesized by interpolating the corresponding sequence of key visemes. Using an input parameter vector, the key expressions are blended by a method of scattered data interpolation. During the synthesizing process, an importance-based scheme is introduced to combine both lip-synchronization and facial expressions into one animation sequence in real time (over 120Hz). The proposed approach can be applied to diverse types of digital content and applications that use facial animation with high accuracy (over 90%) in speech recognition.