• Journal of KIISE:Information Networking
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• v.32 no.3
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• pp.339-349
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• 2005

For recent years, data broadcast technology has been recognized as a very effective data delivery mechanism in mobile computing environment with a large number of cli;ents. Especially, a hybrid broadcast algorithm in real-time environment, which integrates one-way broadcast and on-demand broadcast, has an advantage of adapting the requests of clients to a limited up-link bandwidth and following the change of data access pattern. However, previous hybrid broadcasting algorithms has a problem in the methods to get a grip on the change of data access Pattern. It is caused by the diminution of requests for the data items which are contained in periodic broadcasting schedule because they are already broadcasted. To solve this problem, existing researches may remove data items in periodic broadcasting schedule over a few cycles multiplying cooling factor or find out the requests of data items with extracting them on purpose. Both of them are the artificial methods not considering the property of data. In this paper, we propose a real-time adaptive hybrid broadcasting based on data type(RTAHB-DT) to broadcast considering data property and analysis the performance of our aigorithm through simulation study.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.131-140
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• 2018

A broadcast scheduling scheme is an essential technique to improve the performance of data broadcast systems. This paper explores the problem of data broadcast over multiple channels to reduce query response time, and proposes a new hybrid data broadcast scheduling scheme named HDAMA. The proposed scheme employs the strategy that combines the advantages of push-based broadcast and pull-based broadcast. HDAMA could enhance the performance of query response time since it is capable of controlling the influence of access probability properly reflecting the characteristics of multi-data queries and broadcasting pull data items relatively on time. Simulation is performed to evaluate the performance of the proposed scheme. The simulation results show that the performance of HDAMA is superior to other schemes in terms of the average response time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.1019-1028
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• 2013

The BWS (broadcast website) data broadcasting service for terrestrial DMB (digital multimedia broadcasting) has a great advantage that it can provide a website like service through broadcast without web traffic to a plurality of receiving terminals. However, the value of BWS has not been recognized due to the development of mobile communication technology and changes in the environment, where mobile web services through smart devices such as smart phones and pads are common. Recently, various hybrid service technologies provided through hybrid broadcasting, a fusion of broadcasting and communications, have been developed. In this paper, we propose a scalable BWS dividing the hierarchy of BWS into transmission layers and present its application for hybrid DMB data broadcasting services.

• 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.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.243-250
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• 2005

To introduce the cache in a client is one of the methods to migrate the performance degradation of broadcast systems doe to the inherent restrictions of wireless communication environments such as low bandwidth or frequent disconnections. In this paper, we propose a pull-based broadcast strategy in hybrid-based data broadcast systems using bit vectors in order to effectively broadcast data recently requested by clients. Then, we propose a caching strategy considering the characteristics of data broadcast algorithm and then evaluate the performance of the system. According to the result of evaluation, the system employing the proposed strategies shows the better performance in terms of response time.

• Journal of KIISE:Databases
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• v.31 no.3
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• pp.297-306
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• 2004

Push-based broadcasting in wireless information services is a very effective technique to disseminate information to a massive number of clients when the number of data items is small. When the database is large, however, it nay be beneficial to integrate a pull-based (client-to-server) backchannel with the push-based broadcast approach, resulting in a hybrid data delivery. In this paper, we analyze the performance behavior of a predeclaration-based transaction processing, which was originally devised for a push-based data broadcast, in the hybrid data delivery through an extensive simulation. Our results show that the use of predeclaration-based transaction processing can provide significant performance improvement not only in a pure push data delivery, but also in a hybrid data delivery.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.360-371
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• 2011

T-DMB hybrid data service provides advanced data services while maintaining backward compatibility with legacy T-DMB receivers by using hybrid BIFS technology enabling distributed delivery of scene description information and object description information. This paper presents the hybrid service authoring framework implementing hybrid BIFS technology for creating contents for distributed delivery, and the results of experiments by using it. Hybrid service authoring framework is comprised of service creation system, service management system, and contents offering system. It enables the creation of combined hybrid data service and the splitting of the contents into two parts for ecah delivery network, data for broadcasting network and the data for mobile network. It also enables the managements of the contents. The feasibility of advanced data services while maintaining backward compatibility with the legacy T-DMB receiver has been proved by the contents created by using the hybrid authoring framework presented in this paper.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.969-976
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• 2011

In this paper, a terrestrial transmission system is proposed for the next generation digital television (DTV) system by applying a hybrid multi-input multi-output (MIMO) technology based on linear dispersion codes (LDCs). The digital video broadcasting-2nd generation terrestrial (DVB-T2) system adopted a space time block code (STBC) for improving receive performance. However, the data rate of STBC is not increased in proportion to the transmitter. The hybrid STBC scheme utilizes several STBC transmission blocks for increasing data rate. It is possible to increase the data rate and performance in the receiver by utilizing LDC. The performances of the proposed and conventional hybrid STBC schemes are evaluated through computer simulations.

• Journal of Positioning, Navigation, and Timing
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• v.1 no.1
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• pp.65-75
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• 2012

We carry out an error analysis of 24-hour global positioning system (GPS)-very long baseline interferometry (VLBI) (GV) hybrid observation data. In this paper, we focus on the impacts of broadcast and final orbits on the GPS delays of the GV hybrid observation by analyzing the residuals, observed - calculated (O-C) values. The residuals show apparent and consistent biases for L1 and L2 signals, respectively. The scatters of the residuals are around a few nanoseconds. The main cause of those observation errors is the absence of the GPS phase and delay calibration system. Most of the satellites show that the differences between the delays, to which broadcast and final orbits are applied, are about 100 times smaller than the current GV hybrid observation errors. We conclude that GPS delays are not greatly affected by orbit accuracies.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.22-30
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• 2023

The portable mobile devices with high performance and high speed 5G network activate and explode the demands for ubiquitous information services that remove the limitations of time for the communication and places to request for the information. NN (Nearest Neighbor) search is one of the most important types of queries to be processed efficiently in the information services. Various indexes have been proposed to support efficient NN search in the wireless broadcast system. The indexes adopting Hilbert curve, grid partition or Voronoi diagram enable the clients to search for NN quickly in the wireless broadcast channel. It is necessary that an efficient means to evaluate the performances of various indexes. In this paper, we propose an open framework that can adopt a variety of indexing schemes and evaluate and compare the performances of them. The proposed framework is organized with open and flexible structure that can adopt hybrid indexing schemes extensible to Voronoi diagram as well as simple indexing schemes. With the implemented framework, we demonstrate the efficiency and scalability and flexibility of the proposed framework by evaluating various indexing schemes for NN query.