• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.5
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• pp.643-649
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• 1993

The problem of locating a periodically inserted frame synchronization pattern in random data for a binary pulse amplitude modulated (PAM) digital communication system over a additive white Gaussian noise(AWGN) channel with co-channel interference is considered. The performance degradation of frame synchronization for the correlation rule due to the presence of co-channel interference is shown. The maximum likelihood(ML) decision rule for the frame synchronization over an AWGN channel with co-channel interference is derived. For the entire range of SNR considered, the ML frame synchronization rule obtains about 1dB signal energy gain over the correlation rule. Specially, the ML rule obtains as much as 2dB gain over the correlation rule when the SNR is greater than 0dB.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.6
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• pp.1689-1706
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• 2012

The preservation of temporal dependencies among a group of processes that exchange continuous media at runtime is a key issue for emerging mobile distributed systems (MDS), such as monitoring of biosignals and interactive multiuser games. Although several works are oriented to satisfy temporal dependencies, most of them are not suitable for MDSs. In general, an MDS is characterized by the absence of global references (e.g. shared memory and wall clock), host mobility, limited processing and storage capabilities in mobile hosts, and limited bandwidth on wireless communication channels. This paper proposes an asymmetric synchronization protocol to be used at runtime in an MDS without using a common reference. One main aspect of our synchronization protocol is that it translates temporal constraints to causal dependencies of the continuous media data as seen by the mobile hosts. We simulate the protocol by considering a cellular network environment and by using MPEG-4 encoders. The simulation results show that our protocol is effective in reducing the synchronization error. In addition, the protocol is efficient in terms of processing and storage costs at the mobile devices, as well as in the overhead attached per message across the wired and wireless channels.

• Journal of Korea Game Society
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• v.19 no.1
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• pp.73-84
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• 2019

This study is intended to suggest ways to improve the quality of the service of subtitles provided for the convenience of viewing for deaf people on e-sports broadcast content and game streamer content. Generally, subtitling files of broadcast content are manually written on air by stenographers, so a delay of 3 to 5 seconds is inevitable compared to the original content. Therefore, the present study proposed the formation of an automatic synchronization calibration system using speech recognition technology. In addition, a content application experiment using this system was conducted, and the final result confirmed that the time of synchronization error of subtitling data could be reduced to less than 1 second.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7B
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• pp.469-480
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• 2005

This paper presents new multimedia transmission and synchronization scheme for parallel server in wireless environment. The proposed scheme is developed for the parallel sewer that stores MPEG-4 data according to VOP (video object plane) types, i.e., I-, p-, and B-VOP. The goal of our research is to develop the enhanced multimedia transmission scheme that copes with load unbalancing, congestion, and jitter. Thus, we consider three issues; the data striping, the priority queuing, and the multimedia synchronization. First, we develop a parallel server architecture in which each server separately stores video data that is striped by the MPEG-4 VOP types.

• The KIPS Transactions:PartD
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• v.11D no.4
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• pp.783-798
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• 2004

An e-business client application in ubiquitous mobile computing environment may become disconnected from the enterprise server due to broken communication connections caused by the limitation of mobile computing environments(limited battery life of the mobile device, low bandwidth communication, incomplete wireless communication infrastructure, etc). It Is even Possible that mobile client application Intentionally operates in disconnected mode to reduce communication cost and the power consumption of the mobile device. We use “data hoarding” as a means of providing local autonomy to allow transactions to be processed and committed on the mobile host despite of disconnection. The key problem to this approach is the synchronization problem that serialize potentially conflicting updates from disconnected clients on master objects of the server database. In this paper, we present a new transaction synchronizing method that splits a transaction into a set of independent component transactions and give the synchronization priority on each component taking the possibility of use and conflicts in the server into consideration. Synchronization is performed component by component based un synchronization priority. After the Preferred component of a no bile transaction succeeds in synchronization with the server, the mobile transaction can pre-commit at server. A pre-committed transaction's updated value is made visible at server before the final commit of the transaction. The synchronization of the component with low synchronization priority can be delayed in adaption to wireless bandwidth and computing resources. As a result, the availability of important data updated by mobile client is increased and it can maximize the utilization of the limited wireless bandwidth and computing resources.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.10
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• pp.373-380
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• 2022

This paper presents a deep learning based group synchronization that supports networked immersive interactions between remote users. The goal of group synchronization is to enable all participants to synchronously interact with others for increasing user presence Most previous methods focus on NTP-based clock synchronization to enhance time accuracy. Moving average filters are used to control media playout time on the synchronization server. As an example, the exponentially weighted moving average(EWMA) would be able to track and estimate accurate playout time if the changes in input data are not significant. However it needs more time to be stable for any given change over time due to codec and system loads or fluctuations in network status. To tackle this problem, this work proposes the Deep Group Synchronization(DeepGroupSync), a group synchronization based on deep learning that models important features from the data. This model consists of two Gated Recurrent Unit(GRU) layers and one fully-connected layer, which predicts an optimal playout time by utilizing the sequential playout delays. The experiments are conducted with an existing method that uses the EWMA and the proposed method that uses the DeepGroupSync. The results show that the proposed method are more robust against unpredictable or rapid network condition changes than the existing method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.264-274
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• 2014

Time synchronization becomes a critical issue in underwater acoustic networks (UANets) because nodes cooperate together or individually work by communicating each other in diverse underwater applications. Compared with the time synchronization approaches in terrestrial networks, several intrinsic limitations of UANets (e.g., the unavailability of GPS, long propagation delay, mobility due to currents, limited energy consumption, or low data rate) need to be considered in synchronizing the timing among underwater nodes. For the purpose of developing more efficient time synchronization protocols for UANets, we review the existing approaches, which estimate both the clock offset and the clock skew of underwater nodes. Finally, we outline the state-of-the art time synchronization protocols for UANets by comparing and summarizing them according to their synchronization characteristics.

• Spatial Information Research
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• v.11 no.2
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• pp.119-130
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• 2003

Since GIS strategic implementation plan was prepared in 1995, Seoul Metropolitan Government (SMG) has implemented the distributed GIS at department level, which prevents various SMG organizations from data-sharing and its common utilization. To solve those problems due to the fragmented GIS structure, SMG developed an action plan for the evolution of enterprise GIS with Spatial Data Warehouse (SDW). In this context, this paper initially analyzed the conceptual architecture of SDW structure and then provided the following guidelines for 1) determining the common GIS data and framework data stored at SDW to satisfy the demand for various GIS data from many SMG departments and sub-organizations, 2) developing the data synchronization process and techniques to make effective data-sharing possible, and 3) making an action plan for enterprise GIS of other self-governmental organizations.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.3
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• pp.239-244
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• 2014

As the usefulness of mobile device is kept growing the privacy of the cloud computing is receiving more attentions. Even though many researches and solutions for privacy matters are suggested we are still worrying about the security problems. In addition most of cloud computing systems uses file-level synchronization which make it difficult to modify a part of a file. If we use data-centric app that stores data on embedded DBMS such as SQLite, a simple synchronization may incur some loss of information. In this paper we propose a solution to build a personal cloud that supports record-level synchronization. And we show a prototype system which uses RESTful web services and the same schema on mobie devices and the cloud storage. Synchronization is achieved by using a kind of optimistic concurrency control.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.251-266
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• 1996

In this paper, we design MHEG engine that can generate MHEG objects and present It to the users in Multimedia/Hypermedia Applications In the MHEG engine, the transmitted MHEG objects decoded into internal format. For the easy interpretation of MHEG objects, we define internal format as to be matched for each MHEG object. We easily processobjectinformation using the tree data structure because object inheritance and possession can be represented in tree structure. Object inheritance and possession must be represented in the internal format because they used in resolving the reference to external objector data file. The presentation synchronization extracts the synchronization information from MHEG composite objects, representing and controlling heterogencous media associated to spatio- temporal relation. In order to exactly represent the spatio-temporal synchronization included into MHEG composite object, we propose the algorithm that processes synchronization using the message of the synchronization module and the internal objects. MHEG engine proposed in this paper may be basic technology fro multimedia application area using Korea New Net.