• Journal of KIISE:Databases
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• v.33 no.1
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• pp.86-101
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• 2006

The bandwidth of channel and the power of the mobile devices are limited on a wireless environment. In this case, data broadcast has become an excellent technique for efficient data dissemination. A significant amount of researches have been done on generating an efficient broadcast program of a set of data items with different access frequencies over multiple wireless broadcast channels as well as single wireless broadcast channel. In this paper, an efficient data allocation method over multiple wireless broadcasting channels is explored. In the traditional approaches, a set of data items are partitioned into a number of channel based on their access probabilities. However, these approaches ignore a variation of access probabilities of data items allocated in each channel. In practice, it is difficult to have many broadcast channels and thus each channel need to broadcast many data items. Therefore, if a set of data items broadcast in each channel have different repetition frequencies based on their access frequencies, it will give much better performance than the traditional approaches. In this paper, we propose an adaptive data allocation technique based on data access probabilities over multiple broadcast channels. Our proposed technique allows the adaptation of repetition frequency of each data item within each channel by taking its access probabilities into at count.

• Journal of Information Technology Services
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• v.15 no.2
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• pp.21-33
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• 2016

Recently, T-Commerce is emerging to provide new services, with the proliferation of digital broadcasting services. However, T-Commerce market and TV home shopping market are being classified as a legal policy on other markets, such as regulated in the service of live broadcasts. The factor that has inhibited activation T-Commerce related to the lack of appropriate institutions and legal systems in the market, despite the environment with the digital broadcasting service is being spread. We were performed conjoint analysis. For this analysis, we select attributes as a quality attractive factors that significantly affects the satisfaction of TV based shopping customers through previous studies. The results showed that the TV-based shopping customers are important to think 'Responsive', 'Playfulness', 'Live broadcast', 'Convenience' and 'Bidirectional' in the order. The 'Responsive' and 'Live broadcast' of such attributes are served as possible only in TV home shopping, because these attributes don't service due to legal and institutional regulations in T-commerce market. The cluster analysis result also showed that TV shopping consumers are more important to think 'Responsive', 'Playfulness', 'Live broadcast' than 'Convenience' and 'Bidirectional', except one of the classification clusters. If real-time broadcast service is impossible because of the legal and institutional regulations, it seems to require the expansion of the services linked the terrestrial broadcasting to the activating T-Commerce market.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.75-84
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• 2015

A data allocation technique is essential to improve the performance of data broadcast systems. This paper explores the issues for allocating data items on broadcast channels to process multiple-data queries in the environment where query profiles and query request rates are given, and proposes a new data allocation scheme named IDAS. The proposed scheme employs the strategy that the broadcast frequency of each data is determined by the square root value of its relative access probability. IDAS could enhance the performance of query response time since it can process queries of high request rate fast and show a resonable degree of query data adjacency. Simulation is performed to evaluate the performance of the proposed scheme. The simulation results show that IDAS outperforms other schemes in terms of the average response time.

• Journal of the Korea Society of Computer and Information
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• v.12 no.2 s.46
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• pp.111-121
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• 2007

In mobile computing environments, data broadcasting is widely used to resolve the problem of limited power and bandwidth of mobile equipments. However, the previous broadcast scheduling methods can be inefficient in the environment where the user requests change dynamically since they are based on static data requests. Moreover, a high-priority user can wait long for infrequently requested data because they never consider the priority of listeners. In this paper, we propose a new broadcast scheduling method that reflects dynamic changes of user requests using user profiles. It also reflects user priorities to reduce the access time of high-priority users. We evaluate the performance of the proposed method through simulation.

• Korean Journal of Remote Sensing
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• v.21 no.5
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• pp.371-382
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• 2005

We present a processing system for the Atmospheric Infrared Sounder (AIRS) sounding suite onboard Aqua satellite. With its unprecedented 2378 channels in IR bands, AIRS aims at achieving the sounding accuracy of radiosonde (1 K in 1-km layer for temperature and $10\%$ in 2-km layer for humidity). The core of the processor is the International MODIS/AIRS Processing Package (IMAPP) that performs the geometric and radiometric correction for generation of Level 1 brightness temperature and Level 2 geophysical parameters retrieval. The processor can produce automatically from received raw data to Level 2 geophysical parameters. As we process the direct-broadcast data almost for the first time among the AIRS direct-broadcast community, a special attention is paid to understand and verify the Level 2 products. This processor includes sub-systems, that is, the near real time validation system which made the comparison results with in-situ measurement data, and standard digital information system which carry out the data format conversion into GRIdded Binary II (GRIB II) standard format to promote active data communication between meteorological societies. This processing system is planned to encourage the application of geophysical parameters observed by AIRS to research the aqua cycle in the Korean peninsula.

• Journal of Advanced Navigation Technology
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• v.12 no.1
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• pp.34-45
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• 2008

Broadcast encryption schemes are applied to transmit digital informations of multimedia, software, Pay-TV etc. in public network. User acquires message or session key to use key that broadcaster transmits, broadcaster need process that generation and distribution key in these process. Also, user secession new when join efficient key renewal need. In this paper, introduce about efficient key generation and distribution, key renewal method. The temporary conference environment base structure against an each mobile device wild gap. Without the transmission possible, it follows infrequent location change and with the quality where the key information change flow. Thus, in this paper, in order to apply to the embedded computing environment and the key generation and the efficient key renewal are done when the mobile device is used of the specify space it proposes.

• Journal of Broadcast Engineering
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• v.21 no.3
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• pp.436-449
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• 2016

This paper compares the transport overhead of MMT (MPEG Media Transport) with that of MPEG-2 TS (Transport Stream). MPEG-2 TS is globally used in multiplexing compressed audio and video data in digital broadcast industry, including areas of DTV (Digital Television), IPTV (Internet Protocol Television), and DMB (Digital Multimedia Broadcasting). It was the early 1990s when MPEG-2 TS standard was established. After more than two decades of years since its first establishment, many parts of MPEG-2 TS turned out to be inappropriate to today's broadcast and communication environment. Given the situations, in 2014 MPEG (ISO/IEC JTC 1 SC 29/WG 11) standardized MMT as the next-generation multimedia transport standard hopefully that can replace MPEG-2 TS. In this paper, with assumptions of broadcast service scenarios we applied both MMT and MPEG-2 TS to each scenario and we calculated their transport overheads. We used a software program that counts the transport overhead, which was developed in our laboratory for this paper. And we conducted a comparative analysis based on the calculated result of transport overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8B
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• pp.954-961
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• 2011

To apply Wi-Fi technique to the Broadcast field, we have to study features of IEEE 802.11 Broadcast packet. IEEE 802.11 Broadcast technique cannot guarantee successful packet delivery than IEEE 802.11 Unicast. A promising solution to this problem is the use of FEC(Forward Error Correction) mechanisms. However, the adjustment of the FEC redundancy rate is not a trivial issue due to the dynamic wireless environment. In order to explore the above issues we conducted an experimental study of the packet loss behavior of the IEEE 802.11g protocol. In order to study, we implemented a broadcast test bed. Based on the experimental results, we provide guidelines on wireless lan parameters(packet size, transmission rate(11g), background traffic). From this experimental study, we provide FEC redundancy rate.

• Journal of KIISE:Databases
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• v.31 no.4
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• pp.422-431
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• 2004

In recent years, different models in data delivery have been explored in mobile computing systems. Particularly, there were a lot of research efforts in the periodic push model where the server repetitively disseminates information without explicit request. However, average waiting time per data operation highly depends on the length of a broadcast cycle and different access pattern among clients may deteriorate the response time considerably. In this case, clients are preferably willing to send a data request to the server explicitly through backchannel in order to obtain optimal response time. We call the broadcast model supporting backchannel as hybrid broadcast. In this paper, we devise a new transaction processing algorithm(O-PreH) in hybrid broadcast environments. The data objects which the server maintains are divided into Push_Data for periodic broadcasting and Pull_Data for on-demand processing. Clients tune in broadcast channel or demand the data of interests according to the data type. Periodic invalidation reports from the server support maintaining transactional consistency. If one or more conflicts are found, conflict orders are determined not to violate the consistency(pre-reordering) and then the remaining operations have to be executed pessimistically. Through extensive simulations, we demonstrate the improved throughput of the proposed algorithm.

• Journal of KIISE:Databases
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• v.30 no.5
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• pp.476-493
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• 2003

Data broadcast is an effective data transmission method from a data base server to numerous mobile clients due to the restrictions on mobile environment such as low wireless communication bandwidth and energy shortage of mobile devices. There are various broadcast methods based on clients' data access frequencies or semantic relationship of data. The broadcast schedule based only on the access frequencies does not consider semantic relations of data, so that when a client needs to access a series of semantically related data, the client has to listen to the wireless channel for a long time. On the other hand, the broadcast schedule based only on semantic relationship of data makes data access time longer when clients highly request specific data which are not semantically related but frequently accessed. In this paper, we present an efficient data broadcast method based on not only data access frequencies but also semantic relationship to improve mobile clients' query response time. The new hybrid broadcast method we propose creates a data broadcast schedule according to the data access frequencies and then the schedule is adjusted to reflect semantic relationship of data. We show our method is efficient by experimental performance analysis.