• Journal of KIISE:Software and Applications
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• v.29 no.12
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• pp.957-965
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• 2002

Garbage collection in the CLDC typically employs a stop-the-world GC algorithm which is performing a complete garbage collection when needed. This technique is unsuitable for the interactive Java embedded system because this can lead to long and unpredictable delays. In this paper, We present a garbage collection algorithm which reduces the average delay time and supports the interactive environment. Our garbage collector is composed of the allocator and the collector. The allocator determines the allocation position of free-list according to object size, and the collector uses an incremental mark-sweep algorithm. The garbage collector is called periodically by the thread scheduling policy and the allocator allocates the objects of marked state during collection cycle. Also, we introduce a color toggle mechanism that changes the meaning of the bit patterns at the end of the collection cycle. We compared the performance of our implementation with stop-the-world mark-sweep GC. The experimental results show that our algorithm reduces the average delay time and that it provides uniformly low response times.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.34-40
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• 2018

In this study, the optimal buffer size is calculated for seamless video playback on a mobile device. Buffer means the memory space for multimedia packet which arrives in mobile device for video play such as VOD service. If the buffer size is too large, latency time before video playback can be longer. However, if it is too short, playback service can be paused because of shortage of packets arrived. Hence, the optimal buffer size insures QoS of video playback on mobile devices. We model the process of buffering into a discret-time queueing model. Mean busy period length and mean waiting time of Geo/G/1 queue with N-policy is analyzed. After then, we uses the main performance measures to present numerical examples to decide the optimal buffer size on mobile devices. Our results enhance the user satisfaction by insuring the seamless playback and minimizing the initial delay time in VOD streaming process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.455-461
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• 2008

Enhanced Distributed Channel Access (EDCA) is a channel access scheme adopted by the IEEE 802.11e draft standard for QoS-enabled wireless local area networks. It classifies traffic into separate Access Categories (ACs) and achieves service differentiation by allowing each AC to have its own values of channel access parameters. This paper proposes a scheme to dynamically adapt the EDCA parameters to traffic environment so that they both maximize the throughput of non real-time traffics and meet the delay and throughput constraints of real-time traffics. For this purpose, we develop a design algorithm for efficient exploration of the EDCA parameter space. Using the algorithm, we derive a Pareto curve fur delay-throughput trade-off in each anticipated traffic environment. The Pareto database can then be used to optimally adjust the parameter according to the traffic environment and administrative policies. Simulation results show that compared with the default parameter configuration, the proposed scheme is better for delay, throughput guarantee and can improve the throughput of non real-time traffics by 12% on average.

• Journal of KIISE:Databases
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• v.36 no.1
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• pp.50-62
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• 2009

In wireless and mobile environments, data broadcasting is recognized as an effective way for data dissemination due to its benefits to bandwidth efficiency, energy-efficiency, and scalability. In this paper, we address the problem of delayed query processing raised by tree-based index structures in wireless broadcast environments, which increases the access time of the mobile clients. We propose a novel distributed index structure and a clustering strategy for streaming XML data which enable energy and latency-efficient broadcast of XML data. We first define the DIX node structure to implement a fully distributed index structure which contains tag name, attributes, and text content of an element as well as its corresponding indices. By exploiting the index information in the DIX node stream, a mobile client can access the wireless stream in a shorter latency. We also suggest a method of clustering DIX nodes in the stream, which can further enhance the performance of query processing over the stream in the mobile clients. Through extensive performance experiments, we demonstrate that our approach is effective for wireless broadcasting of XML data and outperforms the previous methods.

• Journal of the Korean Society of Child Welfare
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• no.59
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• pp.1-23
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• 2017

Using a subsample of 3,409 unmarried smothers and their children from the Fragile Families and Child Wellbeing study, the present study examined the cross-lagged effects of unmarried fathers' involvement on their children's behavior problems. Father involvement was used as a latent variable to measure the frequency of fathers' visits to the child, fathers' instrumental support, and their supportive parenting. Both variables of father involvement and child behavior problems were repeatedly measured at child ages 3, 5, and 9 to estimate their trends over time. The results indicated that fathers' more active engagement in parenting at child ages 3 to 5 reduced behavior problems in children at ages 5 to 9. Further discussions include programs and services to support unmarried fathers through education and training opportunities for effective parenting, relationship skills, and conflict resolutions as well as policy strategies to encourage their continuous involvement in the lives of their children.

• Journal of Digital Convergence
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• v.17 no.9
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• pp.153-161
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• 2019

Discrimination of media object segments in wireless home proxies has a significant impact on caching delay, and caching delay degrades the performance of the proxy. In this paper, we propose a Single Fetching Smart Caching (SFSC) strategy and a Multi-Fetching Smart Caching (MFSC) strategy to improve the proxy performance of the home network and improve the caching performance for media object segments. The SFSC strategy is a technique that performs caching by sequential fetching of object segments requested by the home node one at a time, which guarantees a faster cache hit rate, and the MFSC strategy is a technique that caches the media object segments by blocking object segments requested by the home node one at a time, which improves the throughput of cache. Simulation results show that the cache hit rate and the caching delay are more efficient than the MFSC technique, and the throughput of the object segment is more efficient than that of the SFSC technique.

• Journal of Digital Convergence
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• v.20 no.4
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• pp.459-468
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• 2022

In medical area, very high resolution images, which is loss sensitive data, are used. Therefore, the use of optical internet with high bandwidth and the transmission of high realiability is required. However, according to the nature of the Internet, various data use the same bandwidth and a new scheme is needed to differentiate effectively these data. In order to achieve the differentiation, optical delay line buffers are used. However, these buffers is constructed based on some optimal values such as the average offered load, measured data burst length, and basic delay unit. Once the buffers are installed, they are impossible to reinstall new buffers. So, the scheme changing burst length dynamically was considered. However, this method is highly unstable. Therefore, in this article, in order to guarantee the stable operation of the scheme, the analysis of operation conditions is performed. With the analysis together with the scheme, high resolution medical data with the higher class can transmit stably without loss.

• The Transactions of the Korea Information Processing Society
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• v.2 no.6
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• pp.891-902
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• 1995

To integrate both the OSI network and the TCP/IP internet, the application gateway that have the powerful and flexible paradigms has been used, but due to the micro-managements of the gateway produce the high costs and the long delay of communication in the case of emergency. The mechanism that maps the access control policies between two domains using the different security policies is needed. These problems are caused by integrating both domains with the different standards. In this paper, the application gateway that delegating to an agent the powerful and flexible services of the CMIP as well as the management functions were proposed. A proposed algorithm that delegates he management script to an gateway safely by capitalizing on the Diffie-Hellman's distribution method, and presents the security mechanism mediating the security policies for guaranteeing the secure communication between two domains using the different security policies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.149-159
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• 2011

Recently, mobile computing environments are becoming rapidly common. This trend emphasizes the necessity of accessing database systems on fixed networks from mobile platforms via wireless networks. However, it is not an appropriate way that applies the database access methods for traditional computing environments to mobile computing environments because of their essential restrictions. This paper suggests a new agent-based mobile database access model and also two functions calculating data significance scores to choose suitable data items for cache replacement and coherence policies. These functions synthetically reflect access term, access frequency and tendency, update frequency and tendency, and data item size distribution. As the result of simulation experiment, our policies outperform LRU, LIX, and SAIU policies in aspects of decrement of access latency, improvement of cache byte hit ratio, and decrease of cache byte pollution ratio.

• Journal of the Korea Society for Simulation
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• v.16 no.3
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• pp.29-38
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• 2007

Recently, the deepening of the environment and accompanying concerns produce various environmental regulations. For example, EPR(Extended Producer Responsibility) is emphasized in many countries such as USA and Europe. According to this, the construction of a reverse supply chain is under compulsion. A diversity of parts can be controlled by a government or enterprises in the construction and management of a reverse supply chain and the effect to the environment is changed according to the policy. Therefore, it is essential to understand the effects of regulations or policies of a government and enterprises on a supply chain. The object of this research is to develop a means to assess the management efficiency and the environmental effect over a whole supply chain and show the effects of various reverse supply chain construction policies on a supply chain. This model can be utilized to establish appropriate policies by understanding the change in the management efficiency and the environmental effect according to the reverse supply chain construction and management method.