• Journal of KIISE:Information Networking
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• v.33 no.4
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• pp.324-332
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• 2006

A caching is a useful technique to alleviate performance degradation due to the inherent narrow bandwidth by reducing contention of broadcast requests. In this paper, we propose a caching strategy for pull-based data broadcast system which considers data popularity among clients. In addition, the proposed strategy also reflects recentness of data access based on data broadcast version. Then, we evaluate the performance of proposed strategy through a simulation approach. According to the results, the strategy considering both hit ratio and miss cost shows better performance than the traditional LRU. In addition, the strategy considering data popularity among clients shows better performance in some cases.

• Journal of KIISE:Databases
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• v.35 no.6
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• pp.518-532
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• 2008

Broadcast scheme has been widely researched for efficient data delivery in the mobile environment because the downlink capacity of a mobile client is much greater than the uplink capacity, and the power of a mobile client is limited. In the proposed scheme, the index lets the client know when data items would be broadcasted and enables the client to minimize the tuning time and power consumption. Single channel index schemes are fit to flat broadcast that performs well when all the broadcasted data items are accessed with the same probability whereas the multi-disk broadcast scheme is proper when the data access distribution is skewed. The existing index schemes, however, cannot work on the Multi-disk broadcast scheme because they cannot point the replicating data items in a broadcast cycle. This paper proposes a Multi-disk Exponential Index (MDEI) which is a single channel index scheme fit to Multi-disk broadcast scheme. Because MDEI scheme organizes a separate index for each disk, it functions with multi-disk broadcast, resulting in a greater reduction of average access latency than that of other flat-broadcast index schemes when the data access distribution is skewed. The performance evaluation showed that MDEI has a good performance when data access distribution is skewed. MDEI has short average access latency and not much average tuning time when the data access distribution is skewed.

• Journal of KIISE:Databases
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• v.29 no.4
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• pp.285-296
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• 2002

When a client requests a set of data items at once, it is crucial to reduce the total time elapsed till the client receives all data items requested. This paper describes a data broadcasting technique that reduces access time for multiple data accesses from clients. The impact of the relative position of each data item in a broadcast schedule is dependent on the degree of data replication between data requests from clients. The relative broadcast frequencies for data items are affected by the degree of access skewness from clients. This paper proposes a technique for generation of a hierarchical data broadcast schedule, which can support multiple data accesses effectively by considering the data sharing among client requests and data access skewness together. Simulation results show that the proposed technique consistently performs better than the previous research results in various environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1523-1545
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• 2019

Cloud computing is now a widespread and economical option when data owners need to outsource or share their data. Designing secure and efficient data access control mechanism is one of the most challenging issues in cloud storage service. Anonymous broadcast encryption is a promising solution for its advantages in the respects of computation cost and communication overload. We bring forward an efficient anonymous identity-based broadcast encryption construction combined its application to the data access control mechanism in cloud storage service. The lengths for public parameters, user private key and ciphertext in the proposed scheme are all constant. Compared with the existing schemes, in terms of encrypting and decrypting computation cost, the construction of our scheme is more efficient. Furthermore, the proposed scheme is proved to achieve adaptive security against chosen-ciphertext attack adversaries in the standard model. Therefore, the proposed scheme is feasible for the system of data access control in cloud storage service.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.11a
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• pp.167-181
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• 1999

• International Journal of Advanced Culture Technology
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• v.11 no.2
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• pp.315-322
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• 2023

Intelligent IoT environments that accommodate a very large number of clients require technologies that provide secure information service regardless of the number of clients. Wireless data broadcast is an information service technique that ensures scalability to deliver data to all clients simultaneously regardless of the number of clients. In wireless data broadcasting, clients access the wireless channel linearly to explore the data, so the access time of clients is greatly affected by the broadcast cycle. Data compression-based data broadcasting can reduce the broadcast cycle and thus reduce client access time. Therefore, a simulation framework that can evaluate the performance of data broadcasting by applying different data compression algorithms is essential and important. In this paper, we propose a simulation framework to evaluate the performance of data broadcasting that can adopt data compression. We design the framework that enables to apply different data compression algorithms according to the data characteristics. In addition to evaluating the performance according to the data, the proposed framework can also evaluate the performance according to the data scheduling technique and the kind of queries the client wants to process. We implement the proposed framework and evaluate the performance of data broadcasting using the framework applying data compression algorithms to demonstrate the performances of data compression broadcasting.

• 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.6
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• pp.561-572
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• 2003

Broadcast-based data delivery has attracted a lot of attention as an efficient way of disseminating data to very large client populations. The main motivation of broadcast-based information systems (BBISs) is that the number of clients that they serve can grow arbitrarily large without any effect on their performance. The performance of BBISs depends mainly on client caching strategies and on data broadcast scheduling mechanisms. This paper addresses the former issue and proposes a new client cache management scheme, named 2Q-CFP, that is suitable to BBISs. This paper also evaluates the performance of 2Q-CFP on the basis of a simulation model. The performance results indicate that 2Q-CFP scheme shows superior performances over GRAY, LRU and CF in the average response time.

• 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 KIISE:Databases
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• v.33 no.1
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• pp.69-85
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• 2006

Broadcast has been often used to disseminate the frequently requested data efficiently to a large volume of mobile clients over a single or multiple channels. Conventional concurrency control protocols for mobile transactions are not suitable for the wireless broadcast environments due to the limited bandwidth of the up-link communication channel. In wireless broadcast environments, the server often broadcast different data items with different frequency to incorporate the data access patterns of mobile transactions. The previously proposed concurrency control protocols for mobile transactions in wireless broadcast environments are focused on the mobile transactions with uniform data access patterns. However, these protocols perform poorly when the data access pattern of update mobile transaction are not uniform but skewed. The update mobile transactions with skewed data access patterns will be frequently aborted and restarted due 4o the update conflict of the same data items with a high access frequency. In this paper, we propose an energy-efficient concurrence control protocol for mobile transactions with skewed data access as well as uniform data access patterns. Our protocol use a random back-off technique to avoid the frequent abort and restart of update mobile transactions. We present in-depth experimental analysis of our method by comparing it with existing concurrency control protocols. Our performance analysis show that it significantly decrease the average response time, the amount of upstream and downstream bandwidth usage over existing protocols.