• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8A
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• pp.815-820
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• 2008

Carrier frequency offset (CFO) is one of the most important problems in an orthogonal frequency division multiplexing (OFDM) system, which seriously degrades the performance of the systems due to its time-variant behavior. In this paper, the performance of a pilot-assisted fine CFO estimator in OFDM-based mobile WiMAX systems is analyzed. Analytical closed-form expression of the mean square error (MSE) of the post-FFT based CFO synchronization scheme is reported for time-variant fading channels. Taking into account the frame structure of the IEEE802.16e standard, simulation results are used to verify the theoretical analysis developed in this paper.

• Annual Conference of KIPS
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• 2008.11a
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• pp.1280-1283
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• 2008

The network performance of MOGs(Multiplayer Online Games) can be measured by the amount of network loads and the response times on user inputs. This paper introduces a frame locking algorithm and a game turn algorithm that have been used for game synchronization in the area of RTS(Real-time Strategy Simulation) Games, a kind of MOG; the results of performance evaluation of these two algorithms are also given. In addition, a server architecture for MOG servers in which replacing synchronization algorithms can be done easily for pursuing efficient performance evaluation, is also introduced.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.73-76
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• 2005

Preamble based synchronization result in performance degradation due to the high time variation in the power delay profile of the channel in fast varying channel. Since most of the timing metric that exploit the preamble is not based on theoretical back ground, it is not easy to find out the reason. In this paper, the behavior of the timing metric in the multipath fading channel is explained.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.213-216
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• 2005

The time synchronization method for Multi-band UWB systems is proposed. We analyze the performance in symbol synchronization using a training symbol with two identical halves. The two halves of the training symbol are made identical by transmitting a modulated sequence on the even frequencies, while zeros are used on the odd frequencies.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.284-293
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• 2005

A critical issue in applications involving networks of wireless sensors is their ability to synchronize, and mitigate the fading propagation channel effects. Especially when distributed 'slave' sensors (nodes) reach-back to communicate with the 'master' sensor (gateway), low power cooperative schemes are well motivated. Viewing each node as an antenna element in a multi-input multi-output (MIMO) multi-antenna system, we design pilot patterns to estimate the multiple carrier frequency offsets (CFO), and the multiple channels corresponding to each node-gateway link. Our novel pilot scheme consists of non-zero pilot symbols along with zeros, which separate nodes in a time division multiple access (TDMA) fashion, and lead to low complexity schemes because CFO and channel estimators per node are decoupled. The resulting training algorithm is not only suitable for wireless sensor networks, but also for synchronization and channel estimation of single- and multi-carrier MIMO systems. We investigate the performance of our estimators analytically, and with simulations.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.516-522
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• 2010

In this paper, the carrier frequency offset estimator is proposed for the China multimedia mobile broadcasting (CMMB). The fractional carrier frequency offset is estimated by utilizing the cyclic prefix in each CMMB symbol. In addition, the integer carrier frequency offset can be estimated with the synchronization signal in every CMMB frame. The proposed estimator is the most suitable for the frame structure of CMMB. It shows a prominent performance even in timing offset and multipath conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1499-1511
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• 2000

We have designed and implemented a receiver of Eureka-147 Digital Audio Broadcasting (DAB) scheme. DAB used OFDM (orthogonal frequency division multiplexing) as its transmission technique that is very sensitive to synchronization error. So reliable synchronization algorithms have been proposed and evaluated. With the algorithms we proposed a PC based real-time DAB receiver has been implemented. We find that the receiver performs satisfactorily to meet the specifications we determined.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.431-436
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• 2000

It is required for us to design multimedia synchronization model which present mixed media, tat contains not only continuous medial but also discontinuous media. And it is useful for us to develop multimedia application software. Proposed paper represents model tat expresses continuous media and discontinuous media. And continuous medial show the temporal relations between media objects then discontinuous media spatial relations. The model proposed in this paper is effective in applying the system to guarantee high quality of services and can process real time application form applying efficient multiple key media when events occur. We verified that the proposed model has improved media palyout rate compared with other previous synchronization models through simulation.

• Journal of Navigation and Port Research
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• v.30 no.5 s.111
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• pp.343-349
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• 2006

In order to enhance the robustness against noisy environment, the previous GPS initial synchronization method of DGPS reference stations adopts not only the coherent integration method but also the non-coherent integration method. However the previous GPS initial synchronization method muses the non-coherent integration loss, which is a dominant factor among the signal acquisition losses in noisy environment. And the non-coherent integration loss increases with the strength of noise signal. In this paper, a novel GPS initial synchronization method is proposed for robust DGPS reference stations in noisy environment. This paper presents that the proposed GPS initial synchronization method suppresses the non-coherent acquisition loss. Furthermore, with regard to the mean acquisition time, it is shown that the number of the search cells of the proposed GPS initial synchronization method is much smaller than that of the previous GPS initial synchronization method Finally, through the simulation by the GPS simulator, it is seen that the GPS signal of nigh signal-to-noise ratio can be acquired under increased noise floor using the proposed GPS initial synchronization method.