• The Journal of Information Systems
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• v.20 no.4
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• pp.181-204
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• 2011

Recently, the development of ICT(information & communications technology) with the advent of new media paradigm shift in learning has brought a dramatic impact on the competitiveness of universities. The previous studies on the academic performance of e-learning mainly targeted on e-learning users, studying additional synchronization and system quality factors to measure academic performance. This study empirically analyzed the learning flow and academic performance considering both DeLone & McLean model system quality and synchronizing factors based on ARCS model. Relating to quality and synchronization factors, the academic performance of e-learning system was tested, and the difference between learning flow and academic performance was also analyzed based on time-series data, by the test difference(in the beginning, during, and final of the semester). The results of the study are as follows. First, the study shows that both system quality and synchronization directly affected the learning performance. Thus, when designing e-learning system, it is necessary to consider these two factors at the same time. Second, the indirectly mediating effect on the system quality and synchronization factors turned out to be significant in learning flow. Third, the result of regression analysis on the contents of utilizing dummy variable presents that the teacher's explanation has greater influence than multimedia has to the academic performance, and furthermore, the test difference showed no significance. Further research should be undertaken to consider the learner's degree of acceptance which reflects various aspects for building m-learning or u-learning.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.123-124
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• 2007

In this paper a comparison of several coarse time synchronization(CTS) algorithms for OFDM is presented. The goal of a CTS is to achieve a timing estimate that avoids IST in the receiver. Five coarse timing estimation algorithms are examined and their performances are compared associated with hardware complexity. Simulations has been performed for DVB-T 2K system in thee different channels.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.6
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• pp.127-134
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• 2016

WBSN (Wireless Body Sensor Network), also called WBAN (Wireless Body Area Networks) generally, is a kind of WSN (Wireless Sensor Network) applications, which is composed of the various sensor nodes residing in human body embodied or in wearable way. The measured data at each sensor node in WBSN requires being synchronized at sink node for exact analysis for status of human body, which is like WSN. Although many time synchronization protocols for WSN has been already developed, they are not appropriate to WBSN. In this paper, a new time synchronization protocol for WBSN considering the characteristics of WBSN is proposed. The proposed scheme is not only simple, but also consumes less power, leading to increasing network life time. We will show that the proposed scheme is appropriate to WBSN by evaluating its performance by simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1543-1548
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• 2009

In this paper, a high speed code synchronization circuit is proposed. for fast code synchronization, matched filler method is used for initial code acquisition with two channel correlators. Particular frequency patterns of the limited number having the information about PN code start time are composed and transmitted repeatedly to increase the probability of accurate initial synchronization. And digital frequency synthesizer is proposed. And it's performance is analyzed theoretically. The analysis show that fast frequency hopping is possible in frequency hopping system that use digital frequency synthesizer.

• Journal of KIISE:Information Networking
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• v.27 no.2
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• pp.123-130
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• 2000

It is important interest for us to solve skew problem in intermedia synchronization and to solve jitter problem in intramedia synchronization. It propose multimedia synchronization model to represent mixed media which contain temporal media and spatial media, and that helps us to develop multimedia application software efficiently. The proposed paper use four parameters to deal with QoS of intermedia synchronization and relative duration time algorithm and jitter-compensatory time algorithm are presented. When key medium is destroyed we make a delay as much as maximum delay jitter of the key medium in order to playout the other medium as much as that. The result is that the application of maximum delay jitter improves the service quality.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.125-131
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• 2017

In this paper, an efficient structure of device-to-device (D2D) synchronization preamble is proposed to meet the enhanced time and frequency synchronization requirements for D2D communication. D2D communication can be applied not only for the cellular communications, but also unmaned aerial vehicle communications and vehicle-to vehicle communication. The proposed preamble structure is transmitting signals at every odd subcarriers, and empty the other subcarriers to minimize the effect of inter-carrier interference. According to the simulation results, the proposed preamble structure provides improved time offset estimation performance, without degrading frequency offset estimation performance compared to the current LTE D2D preamble.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1506-1513
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• 2009

This paper presents a synchronization method to determine the exact demodulation time using the MFM Flag of the 18000-3 PJM mode, along with the hardware structure to implement the proposed method. The proposed system detects an incipient peak using ITS(Initial Time Selector) and a correlator and achieves the final synchronization via identifying the peak position from the comparison of the outputs of two followed additional correlators. The peak detection algorithm and the choice of the templates of the correlators are described. Simulation results show that the proposed system performs successfully in noisy environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.8
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• pp.3121-3135
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• 2015

Owing to the increase in consumption of multimedia content and the improvement of device capacity, user demand for high-quality content has increased. However, it is difficult to transport such large amounts of content over the existing broadcasting network with limited bandwidth. To provide high-definition broadcasting, some studies suggest methods of transporting multimedia over heterogeneous networks after encoding content hierarchically. MPEG Media Transport (MMT), standardized by Moving Picture Experts Group (MPEG), is a solution that enables large-volume media transport over heterogeneous networks such as digital broadcasting networks and packet-switched networks. In the case of delivering a scalable encoded video over different networks, synchronization of each stream is an important issue. MMT defines a synchronization scheme, but does not contain sufficient functions to implement it. In this paper, we propose a synchronization scheme for media streams that are encoded hierarchically, divided into layers, and transported over heterogeneous networks. We implement our scheme using MMT and HTTP, and experimented using three encapsulated video streams with different durations. As a result, we show that the proposed scheme can reduce the waiting time to display high-quality video, relative to Dynamic Adaptive Streaming over HTTP-Scalable Video Coding (DASH-SVC) by requesting segments of enhanced layers after calculating the transmission time. Additionally, we find out that the selection of durations have a relation to the characteristics of the video.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.225-232
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• 2008

When a single source of multimedia contents is distributed to multiple reproduction devices, the audio and video contents require synchronous play for multi-channel stereo sound and lip-synchronization. The multimedia system in vehicle, especially, has researched to move to wireless environments from legacy wired environments. This paper proposes the advanced algorithm for providing synchronized services of real-time multimedia traffic in IEEE 802.11 WLANs [1]. For these, we implement the advanced IEEE 1588 Precision Time Protocol [2] and the environments for simulation. Also, we estimate and analysis performance of the algorithm, then we experiment and analysis after the porting of algorithm in wireless LAN devices (Linksys wrt-350n AP network device) to characterize timing synchronization accuracy.

• 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.